1. Flower, H., M. Rains, D. Lewis, and J.-Z. Zhang. Rapid and intense phosphate desorption kinetics when saltwater intrudes into carbonate rock. Estuaries and Coasts, 40(5):1301-1313, doi:10.1007/s12237-017-0228-z 2017

    Abstract:

    It is important to understand how phosphate sorption dynamics of coastal carbonate aquifers are affected by seawater intrusion, because many coastal aquifers are composed of carbonate rocks and subject to an increase in saltwater intrusion during relative sea-level rise. Twelve carbonate rock and unconsolidated sediment specimens were acquired from a test corehole spanning the full thickness of the Biscayne aquifer in southeastern Florida. All 12 samples exhibit low phosphorus content but variable contents of iron. Column leaching experiments were conducted with two carbonate aquifer samples, alternating between freshwater and saltwater flow. With the first influx of saltwater, phosphate concentration in leachate increased rapidly from a freshwater value of approximately 0.2 μM to peaks of between 0.8 and 1.6 μM. The phosphate concentration began to diminish as saltwater continued to flow, but sustained desorption continued for over 2 h. Overall, seawater drove sorption behavior much more than chemical composition for the aquifer rocks and sediment from the seven rock samples for which we did isotherm sorption experiments. Our results indicate that an immediate and intense pulse of phosphate desorption from carbonate rock and sediment with low phosphorus content occurs in response to an influx of seawater and that the duration of desorption will vary by layer within a single aquifer.

  2. Flower, H., M. Rains, D. Lewis, J.-Z. Zhang, and R. Price. Saltwater intrusion as potential driver of phosphorus release from limestone bedrock in a coastal aquifer. Estuarine, Coastal and Shelf Science, 184:166-176, doi:10.1016/j.ecess.2016.11.013 2017

    Abstract:

    An important but often overlooked consequence of saltwater intrusion is the potential increase of groundwater soluble reactive phosphorus concentrations. The phosphorus sorption dynamics of two limestone rocks of different composition were investigated by simulating seawater intrusion over a wide range of mixing ratios between freshwater and saltwater. Both rocks exhibited a logarithmic loss of sorption efficiency in mixtures containing more than approximately 3 mM Cl concentration (100 mg Cl/L; about 0.5% saltwater). We infer that aquifer solids immersed in freshwater would undergo phosphorus desorption in response to the introduction of this minor amount of seawater. This Cl concentration is within the range designated as fresh water. Thus we conclude that increased soluble reactive phosphorus availability from saltwater-induced desorption may occur at the ion exchange front, which is actually landward of the saltwater intrusion front as it is commonly defined. Sorption efficiency in our experiments continued to decline as salinity increased, until Cl concentration reached a second threshold of 50 or 200 mM (1700 or 7700 mg Cl/L), depending on the rock composition, particularly iron content. Further increase in salinity would produce little increase in groundwater soluble reactive phosphorus concentration. Our results have implications for soluble reactive phosphorus availability in estuaries that receive mixing zone groundwater discharge.

  3. Aoyama, M., M. Abad, C. Anstey, M. Ashraf, A. Bakir, S. Becker, S. Bell, E. Berdalet, M. Blum, R. Briggs, F. Caradec, T. Cariou, M. Church, L. Coppola, M. Crump, S. Curless, M. Dai, A. Daniel, C. Davis, E. de Santis Braga, M.E. Solis, L. Ekern, D. Faber, T. Fraser, K. Gundersen, S. Jacobsen, M. Knockaert, T. Komada, M. Kralj, R. Kramer, N. Kress, S. Lainela, J. Ledesma. X. Li, J.-H. Lim, M. Lohmann, C. Lonborg, K.-U. Ludwichowski, C. Mahaffey, F. Malien, F. Margiotta, T. McCormack, I. Murillo, H. Naik, G. Nausch, S.R. Olafsdottir, J. van Ooijen, R. Paranhos, C. Payne, O. Pierre-Duplessix, G. Prove, E. Rabiller, P. Raimbault, L. Reed, C. Rees, T. Rho, R. Roman, J. Sun, B. Szymczycha, S. Takatani, A. Taylor, P. Thamer, S. Torres-Valdes, K. Trahanovsky, H. Waldron, P. Walsham, L. Wang, T. Wang, L. White, E.M.S. Woodward, T. Yoshimura, and J.-Z. Zhang. IOCCP-JAMSTEC 2015 inter-laboratory calibration exercise of a certified reference material for nutrients in seawater. Japan Agency for Marine-Earth Science and Technology, IOOCP Report No. 1/2016, ISBN 978-4-901833-23-3, 163 pp., 2016

    Abstract:

    No abstract.

  4. Dong, Y., Q.P. Li, Z. Wu, and J.-Z. Zhang. Variability in sinking fluxes and composition of particle-bound phosphorus in the Xisha area of the northern South China Sea. Deep Sea Research-Part I, 118:1-9, doi:10.1016/j.dsr.2016.10.007 2016

    Abstract:

    Export fluxes of phosphorus (P) by sinking particles are important in studying ocean biogeochemical dynamics, whereas their composition and temporal variability are still inadequately understood in the global oceans, including the northern South China Sea (NSCS). A time-series study of particle fluxes was conducted at a mooring station adjacent to the Xisha Trough in the NSCS from September 2012 to September 2014, with sinking particles collected every two weeks by two sediment traps deployed at 500 m and 1500 m depths. Five operationally defined particulate P classes of sinking particles including loosely-bound P, Fe-bound P, CaCO3-bound P, detrital apatite P, and refractory organic P were quantified by a sequential extraction method (SEDEX). Our results revealed substantial variability in sinking particulate P composition at the Xisha over two years of samplings. Particulate inorganic P was largely contributed from Fe-bound P in the upper trap, but detrital P in the lower trap. Particulate organic P, including exchangeable organic P, CaCO3-bound organic P, and refractory organic P, contributed up to 50–55% of total sinking particulate P. An increase of CaCO3-bound P in the upper trap during 2014 could be related to a strong El Niño event with enhanced CaCO3 deposition. We also found sediment resuspension responsible for the unusual high particles fluxes at the lower trap based on analyses of a two-component mixing model. There was, on average, a total mass flux of 78 ± 50 mg m−2 d−1 at the upper trap during the study period. A significant correlation between integrated primary productivity in the region and particle fluxes at 500 m of the station suggested the important role of biological production in controlling the concentration, composition, and export fluxes of sinking particulate P in the NSCS.

  5. Flower, H., M. Rains, D. Lewis, J.-Z. Zhang, and R. Price. Control of phosphorus concentration adsorption and desorption in shallow groundwater of subtropical carbonate estuary. Estuarine, Coastal and Shelf Science, 169:238-247, doi:10.1016/j.ecss.2015.10.024 2016

    Abstract:

    The balance of fresh and marine water sources in coastal mixing zones can affect phosphorus (P) availability, one of the important drivers of primary productivity. This study focuses on an abiotic portion of the P cycle in the mangrove ecotone of Taylor Slough, coastal Everglades, Florida. We investigated the P sorption properties of sediment with three distinct water sources in this region: (1) fresh groundwater from the inland Everglades; (2) bicarbonate enriched groundwater from the mangrove ecotone; and (3) surface saltwater from Florida Bay. Ecotone groundwater caused soluble reactive P (SRP) to exhibit markedly low sorption efficiency (Kd=0.2 L g-1) compared to fresh groundwater and Florida Bay water (11.3 L g-1 and 3.4 L g-1, respectively). The low SRP buffering capacity of the sediment in ecotone groundwater would maintain higher ambient water SRP concentration in ecotone groundwater than in the other two waters, and would trigger desorption if the sediment changed from one of them to ecotone groundwater. The relative sorption efficiency is consistent with the measured zero equilibrium SRP concentration being highest in ecotone groundwater (0.094 ± 0.003 μM) and lower in fresh groundwater and Florida Bay surface water (0.075 ± 0.005 μM and 0.058 ± 0.004 μM respectively). The temporal variability of SRP concentration in groundwater at the ecotone field station is greater than the range of zero equilibrium SRP concentration for all three waters, so very low SRP concentration in the ambient water would induce desorption from the sediment. Soluble reactive P would be expected to begin desorbing from the sediments at a higher ambient SRP concentration in ecotone groundwater than the other two water types. Our results suggest that ecotone groundwater would release more SRP from mangrove sediments compared to the upstream and downstream waters, due to both its lower P sorption efficiency and its higher zero equilibrium SRP concentration.

  6. Talley, L.D., R.A. Feely, B.M. Sloyan, R. Wanninkhof, M.O. Baringer, J.L. Bullister, C.A. Carlson, S.C. Doney, R.A. Fine, E. Firing, N. Gruber, D.A. Hansell, M. Ishii, G.C. Johnson, K. Katsumata, R.M. Key, M. Kramp, C. Langdon, A.M. Macdonald, J.T. Mathis, E.L. McDonagh, S. Mecking, F.J. Millero, C.W. Mordy, T. Nakano, C.L. Sabine, W.M. Smethie, J.H. Swift, T. Tanhua, A.M. Thurnherr, M.J. Warner, and J.-Z. Zhang. Changes in ocean heat, carbon content, and ventilation: A review of the first decade of GO-SHIP global repeat hydrography. Annual Review of Marine Science, 8:185-215, doi:10.1146/annurev-marine-052915-100829 2016

    Abstract:

    Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth’s climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcing and ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (∼20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean’s overturning circulation.

  7. Carsey, T., J. Stamates, J.-Z. Zhang, F. Bloetscher, D. Meeroff, and C. Featherstone. Point source nutrient fluxes from an urban coast: The Boynton (Florida) Inlet. Environment and Natural Resources Research, 5(2):121-134, doi:10.5539/enrr.v5n2p121 2015

    Abstract:

    The Boynton Inlet (SE Florida, USA) is one of two tidal inlets connecting the Lake Worth Lagoon to the Atlantic Ocean. To quantitate the amount of anthropogenic materials reaching the South Florida coastal ocean and reef track, nutrient fluxes through the Boynton Inlet were measured during two 48-hour intensive studies conducted on June 4-6 and September 26-28, 2007. These studies combined analyses of water samples taken at regular intervals in the Boynton Inlet with acoustic Doppler current profiler (ADCP) measurements of the flow through the inlet. Data collected include concentrations of nutrients (silicate [Si], orthophosphate [PO4], ammonium [NH4], nitrate+nitrite [N+N]), isotope ratios of nitrogen, and physical parameters that included pH, salinity, total suspended solids (TSS), and turbidity. The study found a significant but highly variable flux of nutrients in the eight outgoing (ebb) tidal pulses sampled. Daily fluxes of nitrate+nitrite ranged from 16 to 565 kg N, silicate from 564 to 5197 kg Si, phosphate from 154 to 309 kg P, and ammonium from 34 to 354 kg N. These results are compared with other sources of nutrient inputs into the coastal environment. Inlets are a significant source of offshore nutrients.

  8. Carsey, T.P., S.J. Stamates, C.M. Featherstone, N. Amornthammarong, J.R. Bishop, C.J. Brown, A. Campbell, H.L. Casanova, M.L. Gidley, M. Kosenko, R.M. Kotkowski, J.V. Lopez, C.D. Sinagalliano, L.A. Visser, and J.-Z. Zhang. Broward County coastal ocean water quality study, 2010-2012. NOAA Technical Report, OAR-AOML-44, 217 pp., doi:10.7289/V5TD9VCC 2015

    Abstract:

    Researchers with the Ocean Chemistry and Ecosystems Division of NOAA’s Atlantic Oceanographic and Meteorological Laboratory conducted 12 monthly cruises in two separate track lines off of Broward County, Florida, from November 2010 through January 2012. The cruise tracks were designed to provide information on three categories of the coastal ocean: (1) the vicinity of the Broward and Hollywood treated-wastewater outfalls; (2) the vicinity of the Hillsboro and Port Everglades inlets; and (3) the interstitial areas in between. Sampling took place from aboard the NOAA R/V Hildebrand using a conductivity-temperature-depth (CTD)/rosette for water samples and water column profiles and appropriately located acoustic Doppler current profiler (ADCP) instruments for ocean current information. Measured discrete parameters included location, depth, salinity, temperature, pH, oxygen saturation (dissolved oxygen, DO), oxidation-reduction (redox) potential (ORP), chlorophyll-a, phaeopigments, total suspended solids (TSS), nitrate (NO3), nitrite (NO2), ammonium (NH4), silicate (Si), orthophosphate (PO4), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), particulate carbon (PC), particulate phosphorus (PP), particulate nitrogen (PN), and dissolved organic carbon (DOC). CTD profile data included depth, turbidity, ORP, DO, pH, chlorophyll-a, salinity, temperature, and density. A variety of microbiological entities were measured, including fecal indicator bacteria (FIB), selected waterborne pathogens, and molecular microbial source tracking (MST) markers. Community bacterial metagenomic profiles were also generated for selected sample sites. Quality controls of nutrient sample analyses were obtained following National Environmental Laboratory Accreditation Conference (NELAC)-certified procedures. The data obtained present a view of the coastal ocean as having a low “background” concentration of most analytes, interrupted by elevated concentrations near the outfalls and inlets whose excess concentrations decreased rapidly away from the point sources. The waters were found to be oligotrophic, with no evidence of bloom events. A major upwelling event was observed on August 11, 2011, where a ~10°C temperature drop was observed near the southernmost portion of the sampled area.

  9. Wanninkhof, R., L. Barbero, R. Byrne, W.-J. Cai, W.-J. Huang, J.-Z. Zhang, M. Baringer, and C. Langdon. Ocean acidification along the gulf coast and east coast of the USA. Continental Shelf Research, 98:54-71, doi:10.1016/j.csr.2015.02.008 2015

    Abstract:

    As part of an effort to monitor changes in inorganic carbon chemistry of the coastal ocean, near-synoptic cruises are being conducted in the northern Gulf of Mexico and along the east coast of the United States. Here we describe observations obtained on a cruise in the summer of 2012 and compare them with results from a cruise following a similar track in 2007. The focus is on describing spatial patterns of aragonite saturation state (ΩAr). This parameter is an indicator of ecosystem health, in particular, for calcifying organisms. The results show large-scale regional trends from different source waters at the northeastern and southwestern edges of the domain, along with the modulating effects of remineralization/respiration and riverine inputs. The broader patterns and changes over five years along the coast can be well described by the impacts of large-scale circulation, notably changes in source waters contributions. Changes in the well-buffered Loop Current and Gulf Stream with high ΩAr impact the waters in the southern part of the study area. The less buffered southward coastal currents with low ΩAr originating from the Labrador Sea and Gulf of St. Lawrence impact the ΩAr patterns in the northern regions. The expected 2% average decrease in ΩAr in the surface mixed layer due to increasing atmospheric CO2 levels over the 5-year period is largely overshadowed by local and regional variability from changes in hydrography and mixed layer dynamics.

  10. Zhang, J.-Z., and C.J. Fischer. Carbon dynamics of Florida Bay: Spatiotemporal patterns and biological control. Environmental Science and Technology, 48(16):9161-9169, doi:10.1021/es500510z 2014

    Abstract:

    Carbon dynamics of Florida Bay is manifested by wide ranges of pH (7.65–8.61), dissolved inorganic carbon (DIC, 929-3223 μM), and partial pressure of CO2 (pCO2, 50-1313 μatm) observed over seven years. Despite the seasonal variation, a decline of −0.0066 pH per year was observed as a result of ocean acidification, and the spatiotemporal patterns were consistent with known biological processes in the bay. Microbial respiration of organic matter produced high pCO2, resulting in Florida Bay being a CO2 source to the atmosphere during winter and spring. In summer, cyanobacteria blooms developed in the north central bay drew down pCO2, causing bloom waters to become a CO2 sink while the nonbloom waters shrunk but remained a CO2 source. The maxima local CO2 fluxes were 36.4 ± 10.5 and −14.0 ± 5.6 mmol m–2 d–1 for the source and sink region, respectively. Cyanobacteria blooms modulated the interannual variation in bay-wide CO2 net flux, which averaged 7.96 × 109 ± 1.84 × 109 mol yr–1. Extensive cyanobacteria blooms in 2009 resulted in a 50% reduction in the net CO2 flux as compared with 2010 when a minimal cyanobacteria bloom occurred.

  11. Amornthammarong, N., J.-Z. Zhang, P.B. Ortner, J. Stamates, M. Shoemaker, and M.W. Kindel. A portable analyzer for the measurement of ammonium in marine waters. Environmental Science: Processes and Impacts, 15(3):579-584, doi:10.1039/C2EM30793F 2013

    Abstract: A portable ammonium analyzer was developed and used to measure in situ ammonium in the marine environment. The analyzer incorporates an improved LED photodiode-based fluorescence detector (LPFD). This system is more sensitive and considerably smaller than previous systems and incorporates a pre-filtering subsystem enabling measurements in turbid, sediment-laden waters. Over the typical range for ammonium in marine waters (0-10 µM), the response is linear (r2 = 0.9930) with a limit of detection (S/N ratio >3) of 10 nM. The working range for marine waters is 0.05-10 µM. Repeatability is 0.3% (n = 10) at an ammonium level of 2 µM. Results from automated operation in 15 min cycles over 16 days had good overall precision (RSD = 3%, n = 660). The system was field tested at three shallow South Florida sites. Diurnal cycles and possibly a tidal influence were expressed in the concentration variability observed.

  12. Carsey, T.P., S.J. Stamates, N. Amornthammarong, J.R. Bishop, F. Bloetscher, C.J. Brown, J.F. Craynock, S.R. Cummings, W.P. Dammann, J. Davis, C.M. Featherstone, C.J. Fischer, K.D. Goodwin, D.E. Meeroff, J.R. Proni, C.D. Sinigalliano, P.K. Swart, and J.-Z. Zhang. Boynton Inlet 48-hour sampling intensives: June and September 2007. NOAA Technical Report, OAR-AOML-40, 43 pp., 2012

    Abstract:

    Researchers with the Ocean Chemistry Division of NOAA’s Atlantic Oceanographic and Meteorological Laboratory performed two 48-hour intensive studies of the water flowing through the Boynton Inlet at Boynton Beach, Florida, during June and September 2007. These studies were conducted in support of the Florida Area Coastal Environment (FACE) program. Academic partners who also participated in the effort included colleagues with the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies and the Rosenstiel School of Marine and Atmospheric Science, Florida Atlantic University’s Laboratories for Engineered Environmental Solutions, and the Applied Research Center of Florida International University. Sampling was performed from the southern boardwalk at Boynton Beach during the June intensive and the Boynton Beach Inlet Bridge during the September intensive. The sampling strategy was designed to collect water samples over four complete tidal cycles for each intensive; these data would be employed to quantify the total flux of nearshore-source entities into the coastal waters. The first sampling event was conducted on June 4-6, 2007, and the second was conducted on September 26-28, 2007. Data collected include nutrients (silicate, orthophosphate, ammonium, nitrite+nitrate), isotope ratios of nitrogen, the presence or absence of selected biological indicators (Escherichia coli, enterococci, and total coliform), and physical parameters that included pH, salinity, total suspended solids, and turbidity. Critical to this study was the continuous in situ flow rate measurements obtained via an acoustic Doppler current profiler (ADCP) mounted on the north side of the inlet. This report presents the data gathered from the two sampling intensives. The data reported herein suggest that inlets are important contributors of nutrient and microbiological loads to the coastal zone. The overall view presented is that the lagoon input into Boynton Inlet may be substantial but is also highly variable.

  13. Huang, X.-L., and J.-Z. Zhang. Hydrolysis of glucose-6-phosphate in aged, acid-forced hydrolysed nanomolar inorganic iron solutions-an inorganic biocatalyst? RSC Advances, 2(1):199-208, doi:10.1039/C1RA00353D 2012

    Abstract:

    Phosphate ester hydrolysis is one of the most important chemical processes in biological systems. Although catalysis by the natural phosphoesterases, e.g., purple acid phosphatase (PAP) and its biomimetics, are well known in biochemistry, it has been reported that some metals and mineral phases can significantly facilitate the hydrolysis of phosphate ester. Here we report for the first time that aged, acid-forced hydrolysed nanomolar inorganic iron solutions significantly promoted the hydrolysis of glucose-6-phosphate (G6P), and that the reaction kinetics followed the Michaelis-Menten equation. The catalysis was inhibited by tetrahedral oxyanions in an order of WO4 > MoO4 > PO4. The newly formed oxo-bridge or hydroxo-bridge during the iron-aging process might contribute to this biocatalytic effect, though the detailed mechanism is still unclear. Further studies are needed in order to understand the (hydr)oxo-bridged Fe-Fe structure in water and its role in organic phosphorus transformation. This catalyst might be one of many ubiquitous sets of inorganic enzymes yet to be discovered in nature that act as a bridge between the inorganic and organic worlds, and would have played a critical role in the origin of life.

  14. Lance, V.P., P.G. Strutton, R.D. Vaillancourt, B.R. Hargreaves, J.-Z. Zhang, and J. Marra. Primary productivity, new productivity, and their relation to carbon flux during two Southern Ocean Gas Exchange tracer experiments. Journal of Geophysical Research, 117:C00F14, 14 pp., doi:10.1029/2011JC007687 2012

    Abstract:

    Biological uptake rates of inorganic carbon and nitrate were measured during two sequential tracer-release gas exchange experiments, together known as the Southern Ocean Gas Exchange Experiment (SO GasEx) in the southwest Atlantic sector of the Southern Ocean Antarctic Zone (51°N, 38°W). Primary productivity estimated from 14°C incubations ranged from 26.7 to 47.2 mmol C m-2 d-1 in the first experiment (Patch 1) and 13.7 to 39.4 mmol C m-2 d-1 in the second experiment (Patch 2). Nitrate-based productivity estimated from 15NO3 incubations ranged from 5.8 to 13.1 mmol C m-2 d-1 in Patch 1 and 1.9 to 7.1 mmol C m-2 d-1 in Patch 2. The average ratio of nitrate-based productivity to primary productivity (approximating the f-ratio) was 0.24 in Patch 1 and 0.15 in Patch 2. Chlorophyll concentrations for both patches were less than 1 mg m-3. Photochemical efficiency (Fv/Fm) was low (~0.3) in Patch 1 and moderate (~0.45) in Patch 2. Si(OH)4 concentrations were potentially limiting (-3 for Patch 1 and ~3 mmol m-3 for Patch 2) while NH4+ concentrations were elevated (~1 mmol m-3 for Patch 1 and ~2.2 mmol m-3 for Patch 2) compared with typical open ocean Antarctic Zone water. We hypothesize that Patch 1 productivity was regulated by the availability of Si(OH)4 while Patch 2 productivity was regulated by grazers. Primary production and nitrate-based production (as a proxy for C export) determined here provide components for a mixed layer carbon budget from which the air-sea flux of CO2 will be quantified.

  15. Zhang, J.-Z. Current wet persulfate digestion method considerably underestimates total phosphorus content in natural waters. Environmental Science and Technology, 46(24):13033-13034, doi:10.1021/es304373f 2012

    Abstract:

    No abstract.

  16. Amornthammarong, N., J.-Z. Zhang, and P.B. Ortner. An autonomous batch analyzer for the determination of trace ammonium in natural waters using fluorometric detection. Analytical Methods, 3(7):1501-1506, doi:10.1039/C1AY05095H 2011

    Abstract:

    An autonomous batch analyzer (ABA) is described for the measurement of ammonium in natural waters. The system combines previously described batch analysis and continuous flow analysis methods. With its simpler design, the system is robust, flexible, inexpensive, and requires minimal maintenance. The sampling frequency is ca. 8 h-1 and the limit of detection ca. 1 nM which is comparable to the most sensitive flow through or batch analysis methods previously described. Reproducibility is 0.6% (n = 10) at an ammonium level of 200 nM. There are three working ranges: 5-1000 nM, 20-4000 nM, and 0.2-25 μM. In addition, the system produces a calibration curve by autodilution from a single stock standard solution with the same accuracy as traditional manual calibration methods. Representative field data and comparisons with standard EPA methods confirm the utility of the ABA.

  17. Carsey, T.P., C.M. Featherstone, K.D. Goodwin, C.D. Sinigalliano, S.J. Stamates, J.-Z. Zhang, J. Proni, J.R. Bishop, C.J. Brown, M. Adler, P.L. Blackwelder, and H. Alsayegh. The Boynton-Delray coastal water quality monitoring program. NOAA Technical Report, OAR-AOML-39, 177 pp., 2011

    Abstract:

    This report discusses a sequence of six cruises in the vicinity of the Boynton-Delray (South Central) treated-wastewater plant outfall plume (26°27'43"N, 80°2'32"W), the Boynton Inlet (26°32'43"N, 80°2'30"W), and the Lake Worth Lagoon, Palm Beach County, Florida. The sampling cruises took place on June 5-6, 2007; August 28-29, 2007; October 18-19, 2007; February 14 and 18, 2008; May 19-20, 2008; and July 11-13, 2008. Water was sampled at 18 locations at the surface, middle, and near the seafloor (where there was sufficient depth) for a total of 45 samples; these samples were analyzed for a variety of nutrients and related parameters. The water sampling unit contained a conductivity-temperature-depth (CTD) instrument from which data were obtained at each sampling site. Synchronal ocean current data were measured by a nearby acoustic Doppler current profiler (ADCP) instrument.

  18. Huang, X.-L., and J.-Z. Zhang. Phosphorus sorption on marine carbonate sediment: Phosphonate as model organic compounds. Chemosphere, 85(8):1227-1232, doi:10.1016/j.chemosphere.2011.07.016 2011

    Abstract: Organophosphonate, characterized by the presence of a stable, covalent, carbon to phosphorus (C-P) bond, is a group of synthetic or biogenic organophosphorus compounds. The fate of these organic phosphorus compounds in the environment is not well studied. This study presents the first investigation on the sorption of phosphorus (P) in the presence of two model phosphonate compounds, 2-aminothylphosphonoic acid (2-AEP) and phosphonoformic acid (PFA), on marine carbonate sediments. In contrast to other organic P compounds, no significant inorganic phosphate exchange was observed in seawater. P was found to adsorb on the sediment only in the presence of PFA, not 2-AEP. This indicated that sorption of P from phosphonate on marine sediment was compound specific. Compared with inorganic phosphate sorption on the same sediments, P sorption from organic phosphorus is much less in the marine environment. Further study is needed to understand the potential role of the organophosphonate compounds in biogeochemical cycle of phosphorus in the environment.

  19. Zhang, J.-Z. Avoiding spurious correlation in analysis of chemical kinetic data. Chemical Communications, 47(24):6861-6863, doi:10.1039/C1CC11278C 2011

    Abstract: This communication demonstrates that improperly formulated data analyses can inflate the strength of statistical correlations and result in drawing incorrect conclusions. The widespread misuse of a second-order kinetic model in the recent literature reveals that many chemists are not aware of the dangers of spurious correlation.

  20. Zhang, J.-Z., and X.-L. Huang. Effect of temperature and salinity on phosphate sorption on marine sediments. Environmental Science and Technology, 45(16):6831-6837, doi:10.1021/es200867p 2011

    Abstract:

    Our previous studies on the phosphate sorption on sediments in Florida Bay at 25°C in salinity 36 seawater revealed that the sorption capacity varies considerably within the bay but can be attributed to the content of sedimentary P and Fe. It is known that both temperature and salinity influence the sorption process and their natural variations are the greatest in estuaries. To provide useful sorption parameters for modeling phosphate cycle in Florida Bay, a systematic study was carried out to quantify the effects of salinity and temperature on phosphate sorption on sediments. For a given sample, the zero equilibrium phosphate concentration and the distribution coefficient were measured over a range of salinity (2-72) and temperature (15-35°C) conditions. Such a suite of experiments with combinations of different temperature and salinity were performed for 14 selected stations that cover a range of sediment characteristics and geographic locations of the bay. Phosphate sorption was found to increase with increasing temperature or decreasing salinity and their effects depended upon sediment s exchangeable P content. This study provided the first estimate of the phosphate sorption parameters as a function of salinity and temperature in marine sediments. Incorporation of these parameters in water quality models will enable them to predict the effect of increasing freshwater input, as proposed by the Comprehensive Everglades Restoration Plan, on the seasonal cycle of phosphate in Florida Bay.

  21. Amornthammarong, N., P.B. Ortner, and J.-Z. Zhang. A simple, effective mixing chamber used in conjunction with a syringe pump for flow analysis. Talanta, 81(4-5), 1472-1476, doi:10.1016/j.talanta.2010.02.054 2010

    Abstract: A simple, effective mixing chamber used in conjunction with a syringe pump for flow analysis is described and evaluated. A mixing chamber was constructed using a conventional 5 mL pipette tip and its performance compared with a widely used mixing coil. The results demonstrate that the mixing coil does not rapidly and completely mix solutions. Utilizing a configuration that reversed solution positions in the chamber with each mixing cycle, the proposed mixing chamber achieved complete mixing in a significantly shorter time than the mixing coil. The influence of injected sample volume on absorbance signals was evaluated by calculating an S1/2 value for the system. As tested with a minimal rinse, the system has no discernable carryover. Testing this new approach in our previously described silicate measurement system resulted in a more than twofold improvement in sensitivity.

  22. Aoyoma, M., C. Anstey, J. Barwell-Clarke, F. Baurand, S. Becker, M. Blum, S.C. Coverly, E. Czobik, F. d’Amico, I. Dahllöf, M. Dai, J. Dobson, M. Duval, C. Engelke, G.-C. Gong, O. Grosso, A. Hirayama, H. Inoue, Y. Ishida, D.J. Hydes, H. Kasai, R. Kerouel, M. Knockaert, N. Kress, K.A. Krogslund, M. Kumagai, S.C. Leterme, C. Mahaffey, H. Mitsuda, P. Morin, T. Moutin, D. Munaron, A. Murata, G. Nausch, H. Ogawa, S. Olafsdottir, J. van Ooijen, J. Pan, G. Paradis, C. Payne, O. Pierre-Duplessix, G. Prove, P. Raimbault, M. Rose, H. Saito, K. Saito, K. Sato, C. Schmidt, M. Schuett, T.M. Shammon, J. Sun, T. Tanhua, S. Weigelt-Krenz, L. White, E.M.S. Woodward, P. Worsfold, T. Yoshimura, A. Youénou, and J.-Z. Zhang. 2008 inter-laboratory comparison study of a reference material for nutrients in seawater. Meteorological Research Institute, Technical Report No 60, Tsukuba, Japan, 134 pp., 2010

    Abstract:

    Autoclaved natural seawater collected in the North Pacific Ocean was used as a reference material for nutrients in seawater (RMNS) during an inter-laboratory comparison (I/C) study conducted in 2008. This study was a follow-up to previous studies conducted in 2003 and 2006. A set of six samples was distributed to each of 58 laboratories in 15 countries around the globe, and results were returned by 54 of those laboratories (15 countries). The homogeneities of samples used in the 2008 I/C study, based on analyses for three determinants, were improved compared to those of samples used in the 2003 and 2006 I/C studies. Results of these I/C studies indicate that most of the participating laboratories have an analytical technique for nutrients that is sufficient to provide data of high comparability. The differences between reported concentrations from the same laboratories in the 2006 and 2008 I/C studies for the same batch of RMNS indicate that most of the laboratories have been maintaining internal comparability for two years. Thus, with the current high level of performance in the participating laboratories, the use of a common reference material and the adaptation of an internationally accepted nutrient scale system would increase comparability among laboratories worldwide, and the use of a certified reference material would establish traceability. In the 2008 I/C study we observed a problem of non-linearity of the instruments of the participating laboratories similar to that observed among the laboratories in the 2006 I/C study. This problem of non-linearity should be investigated and discussed to improve comparability for the full range of nutrient concentrations. For silicate comparability in particular, we see relatively larger consensus standard deviations than those for nitrate and phosphate.

  23. Carsey, T.P., H. Casanova, C. Drayer, C. Featherstone, C. Fischer, K. Goodwin, J. Proni, A. Saied, C. Sinigalliano, J. Stamates, P. Swart, and J.-Z. Zhang. FACE outfalls survey cruise: October 6-19, 2006. NOAA Technical Report, OAR-AOML-38, 130 pp. (CD-ROM), 2010

    Abstract:

    In October 2006, a cruise of the Florida Area Coastal Environment (FACE) program was conducted aboard the NOAA RV Nancy Foster. The cruise visited coastal sites in the vicinity of six treated wastewater boils in south Florida. The outfalls included in this study were those for the South Central, Boca Raton, Broward, Hollywood, Miami-Dade North, and Miami-Dade Central wastewater treatment plants. The boils and associated down-current plumes were studied to produce a data set of ocean currents, ocean chemistry, and microbiology. Seawater was analyzed for nitrate + nitrite, nitrite, ammonia, orthophosphate, and silicate. Samples down-current of each boil were collected by a conductivity-temperature-depth (CTD) rosette at three depths--near-surface, mid-depth, and near-bottom--and from three transects--inshore of the boil, approximately in line with the boil, and further offshore of the boil. Overall, surface samples showed the highest nutrient concentrations versus samples taken at other depths; surface samples taken nearest the boil showed the highest nutrient concentrations in comparison to other samples collected in the vicinity of the outfall. The only exception was Si, which had a maximum observed concentration at an inlet sampling site. The outfall plume was found to be dynamic, irregular, and mainly in the upper 10 m of the water column. Samples were analyzed for a variety of microbes; the detection frequency was higher for the southern boils compared to the northern boils. The CTD data indicated a tendency toward better defined and deeper thermoclines at the 20-30 m depth in the deeper (more offshore) casts; the thermocline showed a tendency to shoal at 10-20 m and become less well defined in more inshore casts.

  24. Huang, X.-L., and J.-Z. Zhang. Spatial variation in sediment-water exchange of phosphorus in Florida Bay: AMP as a model organic compound. Environmental Science and Technology, 44(20):7790-7795, doi:10.1021/es100057r 2010

    Abstract: Dissolved organic phosphorus (DOP) has been recognized as dominant components in total dissolved phosphorus (TDP) pools in many coastal waters, and its exchange between sediment and water is an important process in biogeochemical cycle of phosphorus. Adenosine monophosphate (AMP) was employed as a model DOP compound to simulate phosphorus exchange across sediment-water interface in Florida Bay. The sorption data from 40 stations were fitted to a modified Freundlich equation and provided a detailed spatial distribution both of the sediments zero equilibrium phosphorus concentration (EPC0-T) and of the distribution coefficient (Kd-T) with respect to TDP. The Kd-T was found to be a function of the index of phosphorus saturation (IPS), a molar ratio of the surface reactive phosphorus to the surface reactive iron oxide content in the sediment, across the entire bay. However, the EPC0-T was found to correlate to the contents of phosphorus in the eastern bay only. Sediment in the western bay might act as a source of the phosphorus in the exchange process due to their high EPC0-T and low Kd-T, whereas sediments in the eastern bay might act as a sink because of their low EPC0-T and high Kd-T. These results strongly support the hypothesis that both phosphorus and iron species in calcareous marine sediments play a critical role in governing the sediment-water exchange of both phosphate and DOP in the coastal and estuarine ecosystems.

  25. Hydes, D.J., M. Aoyama, a. Aminot, K. Bakker, S. Becker, S. Coverly, A. Daniel, A.G. Dickson, O. Grosso, R. Kerouel, J. van Ooijen, K. Sato, T. Tanhua, E.M.S. Woodward, and J.-Z. Zhang. Determination of dissolved nutrients (N, P, Si) in seawater with high precision and inter-comparability using gas-segmented continuous flow analyzers. The GO-SHIP Repeat Hydrography Manual: A Collection of Expert Reports and Guidelines, IOCCP Report No. 14, ICPO Publication Series No. 134, Version 1, 87 pp., 2010

    Abstract:

    The Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) brings together scientists with interests in physical oceanography, the carbon cycle, marine biogeochemistry and ecosystems, and other users and collectors of ocean interior data to develop a sustained global network of hydrographic sections as part of the Global Ocean Climate Observing System. A series of manuals and guidelines are being produced by GO-SHIP which update those developed by the World Ocean Circulation Experiment (WOCE) in the early 1990s. Analysis of the data collected in WOCE suggests that improvements are needed in the collection of nutrient data if they are to be used for determining change within the ocean interior. Production of this manual is timely as it coincides with the development of reference materials for nutrients in seawater (RMNS). These RMNS solutions will be produced in sufficient quantities and be of sufficient quality that they will provide a basis for improving the consistency of nutrient measurements both within and between cruises. This manual is a guide to suggested best practice in performing nutrient measurements at sea. It provides a detailed set of advice on laboratory practice for all the procedures surrounding the use of gas-segmented continuous flow analyzers (CFA) for the determination of dissolved nutrients (usually ammonium, nitrate, nitrite, phosphate and silicate) at sea. It does not proscribe the use of a particular instrument or related chemical method as these are well described in other publications. The manual provides a brief introduction to the CFA method, the collection and storage of samples, considerations in the preparation of reagents and the calibrations of the system. It discusses how RMNS solutions can be used to track the performance of a system during a cruise and between cruises. It provides a format for the meta-data that need to be reported alongside the sample data at the end of a cruise so that the quality of the reported data can be evaluated and set in context relative to other data sets. Most importantly the central manual is accompanied by a set of nutrient standard operating procedures (NSOPs) that provide detailed information on key procedures that are necessary if best quality data are to be achieved consistently. These cover sample collection and storage, an example NSOP for the use of a CFA system at sea, high precision preparation of calibration solutions, assessment of the true calibration blank, checking the linearity of a calibration and the use of internal and externally prepared reference solutions for controlling the precision of data during a cruise and between cruises. An example meta-data report and advice on the assembly of the quality control and statistical data that should form part of the meta-data report are also given.

  26. Zhang, J.-Z. Application of liquid waveguide to shipboard underway and in situ low-level nutrient measurements in seawater. Proceedings, OceanObs'09: Sustained Ocean Observations and Information for Society (Annex), Venice, Italy, September 21-25, 2009, J. Hall, D.E. Harrison, and D. Stammer (eds.). ESA Publication WPP-306, 4 pp., doi:10.5270/OceanObs09 2010

    Abstract: No abstract.

  27. Zhang, J.-Z., L. Guo, and C.J. Fischer. Abundance and chemical speciation of phosphorus in sediments of the Mackenzie River Delta, the Chukchi Sea, and the Bering Sea: Importance of detrital apatite. Aquatic Geochemistry, 16(3):353-371, doi:10.1007/s10498-009-9081-4 2010

    Abstract:

    Utilizing a sequential extraction technique this study provides the first quantitative analysis on the abundance of sedimentary phosphorus and its partitioning between chemically distinguishable phases in sediments of the Bering Sea, the Chukchi Sea and the Mackenzie River Delta in the western Arctic Ocean. Total sedimentary phosphorus (TSP) was fractionated into five operationally defined phases: (1) adsorbed inorganic and exchangeable organic phosphorus; (2) Fe-bound inorganic phosphorus; (3) authigenic carbonate fluorapatite, biogenic apatite, and calcium carbonate-bound inorganic and organic phosphorus; (4) detrital apatite; and (5) refractory organic phosphorus. TSP concentrations in surface sediments increased from the Chukchi Sea (18 µmol g-1 of dried sediments) to the Bering Sea (22 µmol g-1) and to the Mackenzie River Delta (29 µmol g-1). Among the five pools, detrital apatite phosphorus of igneous or metamorphic origin represents the largest fraction (~43%) of TSP. The second largest pool is the authigenic carbonate fluorapatite, biogenic apatite as well as CaCO3 associated phosphorus (~24% of TSP), followed by the Fe-bound inorganic phosphorus, representing ~20% of TSP. The refractory organic P accounts for ~10% of TSP and the readily exchangeable adsorbed P accounts for only 3.5% of TSP. Inorganic phosphorus dominates all of phosphorus pools, accounting for an average of 87% of the TSP. Relatively high sedimentary organic carbon and total nitrogen contents and low delta13C values in the Mackenzie River Delta together with the dominance of detrital apatite in the TSP demonstrate the importance of riverine inputs in governing the abundance and speciation of sedimentary phosphorus in the Arctic coastal sediments.

  28. Amornthammarong, N., and J.-Z. Zhang. Liquid-waveguide spectrophotometric measurement of low silicate in natural waters. Talanta, 79(3):621-626, doi:10.1016/j.talanta.2009.04.050 2009

    Abstract:

    This paper describes a robust, sensitive method for measurement of low silicate in natural water. The method is based on the reaction of silicate with ammonium molybdate to form a yellow silicomolybdate complex, which is then reduced to silicomolybdenum blue by ascorbic acid. This method shows no refractive index effect and a small salinity effect that can be corrected for seawater samples. It was found that the use of poly-vinyl alcohol can prevent the precipitation formation in the ammonium molybdate solution and improve the stability of the silicomolybdenum blue complex. The sensitivity of this method is substantially enhanced by using a liquid-waveguide capillary cell. The detection limit is 0.1 µM and the working range is 0.1-10 µM for using a 2-m liquid-waveguide capillary cell (LWCC). The method can be used for both freshwater and seawater samples and has been used to study the distribution of silicate in surface seawater of Gulf Stream in the Florida Straits.

  29. Carsey, T., K.D. Goodwin, J. Hendee, J.R. Proni, C. Sinigalliano, J. Stewart, J.-Z. Zhang, N. Amornthammarong, J. Craynock, S. Cummings, P. Dammann, C. Featherstone, J. Stamates, and K. Sullivan. A glimpse of the Florida Area Coastal Environment (FACE) program. Proceedings, 11th International Coral Reef Symposium, Ft. Lauderdale, FL, July 7-11, 2008. International Society for Reef Studies, 559-563, 2009

    Abstract: The Florida Area Coastal Environment (FACE) research program gathers a variety of data related to water inputs into the coastal zone of southeast Florida. The water inputs studied include treated wastewater discharges, inlet flows, and upwelling events. Measurements include currents, nutrients, microbial contaminants, and stable isotopes. This report provides a glimpse of the data collected in this program. Data collected from the Boynton inlet point to the significance of this discharge as a source of nutrient and microbiological loads to coastal waters and demonstrate the importance of accounting for all major discharges in order to fully understand the impact of land use and water management decisions on coastal resources.

  30. Huang, X.-L., and J.-Z. Zhang. Neutral persulfate digestion at sub-boiling temperature in an oven for total dissolved phosphorus determination in natural waters. Talanta, 78(3):1129-1135, doi:10.1016/j.talanta.2009.01.029 2009

    Abstract:

    A simplified, easily performed persulfate digestion method has been developed to process a large number of water samples for routine determination of total dissolved phosphorus. A neutral potassium persulfate solution (5%, w/v, pH ~6.5) is added to the samples (at 10 mg potassium persulfate per mL of sample), which are then digested at 90°C in an oven for 16 h. This method does not require pH adjustment after digestion because neither an acid nor a base is added to the samples prior to digestion. The full color of phosphoantimonylmolybdenum blue from the digested samples develops within 8 min. Compared with the autoclave method, digestion at sub-boiling temperatures in an oven is safer, and a large number of samples can be heated overnight requiring no constant monitoring. The apparent molar absorptivity (epsilon) of nine organic phosphorus compounds and two condensed inorganic phosphates ranged from 1.17 x 104 to 1.82 x 104L mol-1 cm-1 in both distilled water and artificial seawater matrixes. The average recovery of these phosphorus compounds was 94 ± 11% for the DIW matrix and 90 ± 12% for the ASW matrix. No significant difference in molar absorptivity was observed between the undigested and digested phosphate, especially in the seawater matrix. It is, therefore, suggested that a phosphate solution be directly employed without digestion as the calibration standard for routine determination of total dissolved phosphorus. This method was used to study the spatial distribution of total dissolved phosphorus in the surface waters of Florida Bay.

  31. Zhang, J.-Z., C.R. Kelble, C.J. Fischer, and L.D. Moore. Hurricane Katrina induced nutrient runoff from an agricultural area to coastal waters in Biscayne Bay, Florida. Estuarine, Coastal, and Shelf Science, 84(2):209-218, doi:10.1016/j.ecss.2009.06.026 2009

    Abstract: Water quality surveys conducted in Biscayne Bay, Florida, indicated enhanced nutrient input coupled with increased runoff as a result of precipitation associated with Hurricane Katrina. Nutrient concentrations before Katrina ranged from 0.06-24.2 mM (mean 3.3 mM) for nitrate and 0.01-0.18 mM (mean 0.1 mM) for soluble reactive phosphate. Five days after Katrina, nitrate concentrations ranged from 0.87-80.0 mM (mean 17.0 mM), with a bay-wide mean increase of 5.2-fold over pre-hurricane levels. Soluble reactive phosphate concentrations ranged from 0.07-0.62 mM (mean 0.2 mM), with a bay-wide mean increase of 2-fold over pre-hurricane levels. The maximum concentrations for both nitrate and soluble reactive phosphate were found at a water quality monitoring station near the mouth of Mowry Canal, which drains an agricultural area in the southern Biscayne Bay watershed near Homestead, Florida. At this station, nitrate and soluble reactive phosphate concentrations increased 7- and 10-fold, respectively. Storm-induced fertilizer runoff from this agricultural area caused a bay-wide increase in nutrient concentrations after Hurricane Katrina. Nutrient concentrations in the bay returned to pre-hurricane levels within three months after Hurricane Katrina, showing the resiliency of the Biscayne Bay ecosystem.

  32. Amornthammarong, N., and J.-Z. Zhang. Shipboard fluorometric flow analyzer for high-resolution underway measurement of ammonium in seawater. Analytical Chemistry, 80(4):1019-1026, doi:10.1021/ac701942f 2008

    Abstract: A shipboard fluorometric flow analyzer has been developed for near-real-time, high-resolution underway measurement of ammonium in seawater. The fluorometric method is based on the reaction of ammonium with o-phthaldialdehyde (OPA) and sulfite. The reagents used in this method have been modified to suit seawater analysis. This method shows no refractive index and salinity effect from seawater samples. The potential interferences in seawater have been studied, and their effects have been reduced. The instrument response is linear over a wide range of ammonium concentration. The limit of detection of 1.1 nM was estimated in laboratory using ammonium standards prepared in distilled water. It should be noted that application of this method to low-level ammonium measurement requires a correction of interference species, such as amino acids. The sample throughput is 3600 h-1. The system can be used for both freshwater and seawater samples and has been used to monitor the distribution of ammonium in Florida coastal waters around an oceanic wastewater outfall.

  33. Aoyoma, M., J. Barwell-Clarke, S. Becker, M. Blum, E.S. Braga, S.C. Coverly, E. Czobik, I. Dahll"f, M. Dai, G.O. Donnell, C. Engelke, G.-C. Gong, G.-H. Hong, D.J. Hydes, M.-M. Jin, H. Kasai, R. Kerouel, Y. Kiyomono, M. Knockaert, N. Kress, K.A. Krogslund, M. Kumagai, S. Leterme, Y. Li, S. Masuda, T. Miyao, T. Moutin, A. Murata, N. Nagai, G. Nausch, M.K. Ngirchechol, A. Nybakk, H. Ogawa, J. van Ooijen, H. Ota, J.M. Pan, C. Payne, O. Pierre-Duplessix, M. Pujo-Pay, T. Raabe, K. Saito, K. Sato, C. Schmidt, M. Schuett, T.M. Shammon, J. Sun, T. Tanhua, L. White, E.M.S. Woodward, P. Worsfold, P. Yeats, T. Yoshimura, A. You,nou, and J.-Z. Zhang. 2006 inter-laboratory comparison study of a reference material for nutrients in seawater. Meteorological Research Institute, Technical Report No. 58, Tsukuba, Japan, 104 pp., 2008

    Abstract:

    Autoclaved natural seawater collected in the North Pacific Ocean was used as a reference material for analyzing nutrient concentrations in seawater during an inter-laboratory comparison study conducted in 2006; this study was a follow-up to a similar but smaller study conducted in 2003. Homogeneity of sample #2 was confirmed by the repeatability of the nutrient concentration measurements and those in terms of one sigma of standand deviation are 0.2%, 0.3%, and 0.2% for nitrate, phosphate, and silicate, respectively. Sets of six samples with concentration ranges of 0.1-42.4 µmol kg-1 for nitrate, 0.0-0.6 µmol kg-1 for nitrite, 0.0-3.0 µmol kg-1 for phosphate, and 1.7-156.1 µmol kg-1 for silicate were analyzed. A set of samples was distributed to each of 55 laboratories around the globe (20 countries), and results were returned by 52 of those laboratories (19 countries). Analytical precisions reported by the participating laboratories for all deteminands were generally lower, by at least 50%, than the consensus standard deviations of the reported concentrations. The consensus standard deviations for sample #2 for all determinands were 5 to 10 times as large as the homogeneities of sample #2 for all determinands. In some laboratories, the non-linearity of the calibration curve was not treated effectively. Our results indicate that variability in the in-house standards of the participating laboratories and the handling of the non-linearity of the calibration curve of the participating laboratories were the primary sources of inter-laboratory discrepancies. The results confirm that a certified reference material for nutrients in seawater and a common method for measuring nutrient concentrations are essential for the improvement of the global comparability of nutrient data in the worlds oceans.

  34. Huang, X.-L., and J.-Z. Zhang. Kinetic spectrophotometric determination of submicromolar orthophosphate by molybdate reduction. Microchemical Journal, 89(1):58-71, doi:10.1016/j.microc.2007.12.001 2008

    Abstract: A kinetic spectrophotometric procedure was developed for determination of submicromolar orthophosphate based on the reaction in which orthophosphate serves as a catalyst in the reduction of molybdenum, and the initial rate of molybdenum-blue formation (Lambdamax = 780 nm) is proportional to the concentration of orthophosphate in the samples. The detection limit (3 x standard deviation of blank, n = 8) was 6 nM and the linear calibration ranged from 10 to 100 nM (r2 = 0.997). The precisions of this method were 3.3% at 10 nM and 5.4% at 50 nM (n = 8), respectively. Similar to other molybdate based methods, silica and arsenate in the samples can interfere with phosphate determination. The responses of silicate and arsenate were about 25% and 7% of that of orthophosphate, respectively, and their interferences were enhanced in the presence of phosphate in the samples due to the synergistic effect of phosphate with arsenate or silicate on the molybdate reagent.

  35. Huang, X.-L., and J.-Z. Zhang. Rate of phosphoantimonylmolybdenum blue complex formation in acidic persulfate digested sample matrix for total dissolved phosphorus determination: Importance of post-digestion pH adjustment. Talanta, 77(1):340-345, doi:10.1016/j.talanta.2008.06.041 2008

    Abstract: Acidic persulfate oxidation is one of the most common procedures used to digest dissolved organic phosphorus compounds in water samples for total dissolved phosphorus determination. It has been reported that the rates of phosphoantimonyl-molybdenum blue complex formation were significantly reduced in the digested sample matrix. This study revealed that the intermediate products of persulfate oxidation, not the slight change in pH, cause the slowdown of color formation. This effect can be remedied by adjusting digested samples pH to a near neural to decompose the intermediate products. No disturbing effects of chlorine on the phosphoantimonylmolybdenum blue formation in seawater were observed. It is noted that the modification of mixed reagent recipe cannot provide near neutral pH for the decomposition of the intermediate products of persulfate oxidation. This study provides experimental evidence not only to support the recommendation made in APHA standard methods that the pH of the digested sample must be adjusted to within a narrow range of sample, but also to improve the understanding of role of residue from persulfate decomposition on the subsequent phosphoantimonylmolybdenum blue formation.

  36. Li, Q.P., D.A. Hansell, and J.-Z. Zhang. Underway monitoring of nanomolar nitrate plus nitrite and phosphate in oligotrophic seawater. Limnology and Oceanography: Methods, 6:319-326, 2008

    Abstract: To study nutrient dynamics and cycling in oligotrophic open ocean environments, continuous measurements of nanomolar nitrate, nitrite, and phosphate are valuable. However, such studies are usually impeded by the detection limits of conventional nutrient-sensors and analyzers. Here, we developed a shipboard deployable underway system for simultaneously monitoring nitrate plus nitrite and phosphate at nanomolar concentrations by the coupling of an optimized flow injection analytical system with two long-path liquid waveguide capillary cells (LWCC). The detection limits are ~2 nM for nitrate plus nitrite and ~1.5 nM for phosphate, respectively. Results from realtime surveys of waters over the west Florida continental shelf and the oligotrophic Sargasso Sea are presented. This system has also been successfully used to analyze more than 1000 discrete seawater samples manually during two cruises in the North Atlantic.

  37. Park, G.-H., K. Lee, R. Wanninkhof, J.-Z. Zhang, D.A. Hansell, and R.A. Feely. Large, non-Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N): Evidence for dinitrogen fixation? Limnology and Oceanography, 53(5):1697-1704, doi:10.4319/lo.2008.53.5.1697 2008

    Abstract: Considerable drawdown of total dissolved inorganic carbon (CT) and oversaturation of oxygen (O2) within a cold (15°C) oligotrophic eddy in the extratropical North Atlantic Ocean (46°N, 20.5°W) indicate that, despite the absence of nitrate (NO3), the eddy was highly productive. Estimates of net community production using the mass balances of CT and O2 were two to five times greater than those obtained using the mass balance of NO3. The remineralization rates obtained using the integrated rates of CT and NO3 accumulation and O2 utilization for the upper thermocline waters (35-300-m depth) were in agreement with CT- and O2-based net community production over the same period; however, all the estimates exceeded the NO3 -based net community production by a factor of two to five, pointing to a considerable accumulation of NO3 in the upper thermocline in excess of changes in the mixed-layer NO3 inventory. The amount of this excess NO3 suggests that a considerable fraction of the net community production was not supported by the mixed-layer NO3 inventory and that an external source of NO3 must be present. Of the various mechanisms that might explain the inequity between NO3 drawdown in the surface layer and NO3 accumulation in the upper thermocline, N2 fixation is the most viable yet surprising mechanism for producing such excess NO3 in this oligotrophic eddy. A significant fraction of net community production in oligotrophic extratropical waters could be supported by processes that are not fully explored or to date have been considered to be insignificant.

  38. Proni, J.R., S.J. Stamates, T.P. Carsey, J.-Z. Zhang, C.D. Sinigalliano, and K.F. Sullivan. Acoustic methods for water mass delineation in coastal marine ecosystems. Proceedings, Ninth European Conference on Underwater Acoustics (ECUA 2008), Paris, France, June 29-July 4, 2008. European Acoustics Association, Volume 1, 237-242, 2008

    Abstract: Acoustical methods play an important role in identifying sources of nutrient to coral reef ecosystems in the South Florida coastal waters. Nutrient fluxes into the coastal ocean are associated with distinct water masses such as inlet discharge plumes, wastewater outfall discharge plumes, and upwelling of deep oceanic water. Various nutrient-bearing water masses can be identified by water column acoustic backscatter profiles, obtained via either shipborne instrumentation or in-situ instrumentation. Such multidimensional images of water masses can be used to optimize the design of chemical and biological sampling efforts. Examples of water mass imaging will be presented, as well as the use of such images in the design of water quality sampling programs.

  39. Zhang, J.-Z., and X.-L. Huang. Relative importance of solid-phase phosphorus and iron on the sorption behavior of sediments. Environmental Science and Technology, 41(8):2789-2795, doi:10.1021/es061836q 2007

    Abstract:

    Of all the metal oxide particles, amorphous iron oxides have the greatest adsorption capacity for phosphate. Coastal sediments are often coated with terrigenous amorphous iron oxides, and those containing high iron are thought to have a high adsorption capacity. However, this conventional wisdom is based largely upon studies of phosphate adsorption on laboratory-synthesized minerals themselves containing no phosphorus. Using natural sediments that contain variable phosphorus and iron, our results demonstrate that the exchangeable phosphate rather than the iron oxides of sediments governs the overall sorption behavior. The iron oxide content becomes important only in sediments that are poor in phosphorus. A total of 40 sampling sites across the Florida Bay provide detailed spatial distributions both of the sediment's zero equilibrium phosphate concentration (EPC0) and of the distribution coefficient (Kd) that are consistent with the distribution of the exchangeable phosphate content of the sediment. This study provides the first quantitative relationships between sorption characteristics (EPC0 and Kd) and the exchangeable phosphate content of natural sediments.

  40. Feely, R.A., R. Wanninkhof, C.L. Sabine, G.C. Johnson, M.O. Baringer, J. Bullister, C.W. Mordy, and J.-Z. Zhang. Global repeat hydrographic/CO2/tracer surveys in support of CLIVAR and global carbon cycle objectives: Carbon inventories and fluxes, pp. 196-205. In Annual Report on the State of the Ocean and the Ocean Observing System for Climate (FY-2005), J.M. Levy, D.M. Stanitski, and P. Arkin (eds.). NOAA Office of Climate Observation, Silver Spring, MD, 337 pp., 2006

    Abstract:

    No abstract.

  41. Huang, X.-L., and J.-Z. Zhang. Surfactant-sensitized malachite green method for trace determination of orthophosphate in aqueous solution. Analytica Chimica Acta, 580(1):55-67, doi:10.1016/j.aca.2006.07.046 2006

    Abstract:

    A surfactant-sensitized spectrophotometric method for determination of trace orthophosphate has been developed using anion surfactant (Ultrawet 60 L) with molybdate and malachite green in low acidic medium (pHT 1.0). The method detection limit (3x standard deviation of blank, n = 10) was 8 nM, and the calibration curve was linear over a range of 10-400 nM (r2 = 0.997). The molar absorptivity was 1.26 x 105 L mol-1 cm-1 at 600 nm with the background correction at 530 nm. The precision of method was 3.4% at 50 nM and 2.4% at 100 nM orthophosphate (n = 10). The hydrolysis of eight organic phosphorus and polyphosphate compounds was less than 2% of the total phosphorus present (5-10 µM). This method showed less arsenate interference than previous methods, with only 3% even in the presence of orthophosphate in the samples. No interference of silicate up to 40 µM was observed. Background anions (in an order of SO42- > NO3- > Cl-) have greater effects than cations (Ca2+ > Mg2+ > Na+) on the reagent blank and the molar absorptivity of the color product.

  42. Zhang, J.-Z. Enhanced sensitivity in flow injection analysis using a long pathlength liquid waveguide capillary flow cell for spectrophotometric detection. Analytical Sciences, 22(1):57-60, doi:10.2116/analsci.22.57 2006

    Abstract:

    Incorporation of a liquid waveguide capillary flow cell into a flow injection instrument enhances the sensitivity of flow injection analysis with spectrophotometric detection by two orders of magnitude. Nitrite determination at nM levels has been used to demonstrate the feasibility of this novel technique for trace analysis. Combining the long pathlength spectrophotometry with flow injection analysis, this technique has advantages of low detection limit, good precision and high sample throughput.

  43. Zhang, J.-Z., and C.J. Fischer. A simplified resorcinol method for direct spectrophotometric determination of nitrate in seawater. Marine Chemistry, 99(1-4):220-226, doi:10.1016/j.marchem.2005.09.008 2006

    Abstract:

    A direct, spectrophotometric method has been adapted for quantitative determination of nitrate concentrations in seawater. The method is based on nitration of resorcinol in acidified seawater, resulting in a color product. The absorption spectrum obtained for the reaction product shows a maximum absorption at 505 nm, with a molar absorptivity of 1.7 x 104 L mol-1 cm-1. This method has a detection limit of 0.5 µM and is linear up to 400 µM for nitrate. The advantage of this method is that all reagents are in aqueous solutions without involving cadmium granules as a heterogeneous reactant, as in conventional methods, and therefore is simple to implement. Application of the resorcinol to seawater analysis demonstrated that the results obtained are in good agreement with the conventional approach involving the reduction of nitrate by cadmium followed by diazotization.

  44. Carsey, T.P., R. Ferry, K.D. Goodwin, P.B. Ortner, J.R. Proni, P. Swart, and J.-Z. Zhang. Brevard County nearshore ocean nutrification analysis. NOAA Technical Report, OAR-AOML-37 (PB2006-101563), 84 pp., 2005

    Abstract:

    In response to public concerns regarding the possibility of elevated nutrients in the Brevard County surf zone, Brevard County and Canaveral Port Authority officials contracted the National Oceanic and Atmospheric Administration (NOAA), Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami to assemble an expert panel of scientists to critically assess the issue. The panel included scientists from AOML, the Environmental Protection Agency, and the University of Miami's Rosenstiel School for Marine and Atmospheric Science. The expert panel was charged with reviewing scientific data and literature to answer a series of questions aimed at determining the existence of elevated nutrients along Brevard County Beaches and the various impacts of elevated nutrients to near shore ecology and human health. The panel was also tasked with evaluating methods for detecting nutrient sources and the impact of cruise and gaming vessels. Lastly, the panel was asked to make recommendations for future monitoring and research. The panel found that existing data did not support the claim that nutrient levels in the surf zone along Brevard County beaches were elevated. In fact, available data indicated that the Brevard County coast had comparatively less nutrients than other observed regions on Florida's east coast. The nutrient concentrations found in the surf zone should not pose a direct risk to human health. Furthermore, there was no evidence of elevated levels of sewage-indicating bacteria in numerous samples taken within the Brevard County surf zone. There was also no scientific evidence that red tide blooms, caused by the organism Karenia brevis, were related to near shore coastal nutrients off Brevard County beaches. Even if elevated nutrients had been found, the response of near shore ecology would depend on a complex set of factors, such as naturally-occurring biological, physical, meteorological, and geochemical forces, which would need to be considered in an integrated fashion. The panel concluded that although the nitrogen isotope method may be used to help identify sources of pollution, such measurements could not be used in isolation to determine the presence of sewage pollution. Based on information from numerous peer-reviewed sources, the panel concluded that one cannot simply assign a particular value to unambiguously indicate sewage contamination. To effectively utilize this method in Brevard County, a much greater understanding of the nitrogen cycle in this particular ecosystem would be needed, including analysis of isotopes in a variety of local sources and organisms. Additional data would be needed to verify the analysis of nutrient data conducted by the panel and to establish a baseline for any future monitoring efforts. Scientifically rigorous answers to the difficult questions posed to the panel would require a comprehensive interdisciplinary program that would include nutrient and microbiological water quality monitoring, techniques to determine nutrient sources (e.g., stable isotope studies of multiple elements, biochemical sewage markers, and deliberate tracers), circulation studies, and mass-balance and numeric modeling. The scope and expense of such a program implies it would be feasible only with the leveraging that can be obtained by close cooperation and coordination with ongoing and planned federal and state programs.

  45. Kim, D.-O., K. Lee, S.-D. Choi, H.-S. Kang, J.-Z. Zhang, and Y.-S. Chang. Determination of diapycnal diffusion rates in the upper thermocline in the North Atlantic Ocean using sulfur hexafluoride. Journal of Geophysical Research, 110(C10):C10010, 9 pp., doi:10.1029/2004JC002835 2005

    Abstract:

    The apparent diapycnal diffusivity below the wind-driven surface mixed layer of the ocean was determined in an anticyclonic eddy in the eastern North Atlantic using sulfur hexafluoride (SF6) tracer data collected in June 1998. In this tracer experiment, the downward penetration of SF6 was measured for three weeks following the deliberate injection of SF6 in the surface mixed layer. The resulting data were used to constrain the one-dimensional Fickian diffusion model to estimate the diapycnal diffusivity. The model also includes the lateral diffusion component so that it can more accurately represent the time evolution of the SF6 concentrations along the isopycnal surface. This affects the estimation of the diapycnal diffusivity. For the upper thermocline immediately below the surface mixed layer we estimated the diapycnal diffusivity for the three-week period as 0.3 ± 0.2 cm2 s-1 at a buoyancy frequency of 8.2 cph.

  46. Li, Q.P., J.-Z. Zhang, F.J. Millero, and D.A. Hansell. Continuous colorimetric determination of trace ammonium in seawater with a long-path liquid waveguide capillary cell. Marine Chemistry, 96(1-2):73-85, doi:10.1016/j.marchem.2004.12.001 2005

    Abstract:

    An automated method for routine determination of nanomolar ammonium in seawater has been developed using segmented flow analysis coupled with a 2-m-long liquid waveguide capillary cell. Conventional photometric detector and autosampler were modified for this method. The optimal concentrations of the reagents and parameters for the development of indophenol blue are discussed. The method has low detection limit (5 nM), high precision (5% at 10-100 nM) and the advantage of rapid analysis of a large number of samples. The method has been used to examine the distribution of ammonium in Florida Bay and Biscayne Bay.

  47. Peltola, E., R. Wanninkhof, R. Feely, R. Castle, D. Greeley, J.-Z. Zhang, F. Millero, N. Gruber, J. Bullister, and T. Graham. Inorganic carbon, nutrient, and oxygen data from the R/V Ronald H. Brown repeat hydrography cruise in the Atlantic Ocean: CLIVAR CO2 section A16N_2003a (4 June-11 August 2003). Oak Ridge National Laboratory/Carbon Dioxide Information Analysis Center, Technical Report, ORNL/CDIAC-149, 36 pp., 2005

    Abstract:

    This report presents methods and analytical and quality control procedures for nutrient, oxygen, and inorganic carbon system parameters performed during the A16N_2003a cruise, which took place from June 4 to August 11, 2003 aboard NOAA Ship R/V Ronald H. Brown under auspices of the National Oceanic and Atmospheric Administration (NOAA). The first hydrographic leg (June 19-July 10) was from Reykjavik, Iceland, to Funchal, Madeira, Portugal along the 20°W meridian, and the second leg (July 15-August 11) continued operations from Funchal, Portugal to Natal, Brazil, on a track southward and ending at 6°S, 25°W. The research was the first in a decadal series of repeat hydrography sections jointly funded by NOAA and the National Science Foundation (NSF) as part of the CLIVAR/CO2/hydrography/tracer program. Samples were taken from up to 34 depths at 150 stations. The data presented in this report includes the analyses of water samples for total inorganic carbon (TCO2), fugacity of CO2 (fCO2), total alkalinity (TALK), pH, nitrate (NO3), nitrite (NO2), phosphate (PO4), silicate (SiO4), and dissolved oxygen (O2). The R/V Ronald H. Brown A16N_2003a data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center (CDIAC). The NDP consists of the oceanographic data files and this printed documentation, which describes the procedures and methods used to obtain the data.

  48. Guo, L., J.-Z. Zhang, and C. Gueguen. Speciation and fluxes of nutrients (N, P, Si) from the upper Yukon River. Global Biogeochemical Cycles, 18(1):GB1038, 12 pp., doi:10.1029/2003GB002152 2004

    Abstract:

    Water samples were collected from the Yukon River near the Stevens Village Station from May to September 2002 and analyzed for nutrients (N, P, and Si) in dissolved, particulate, organic, and inorganic forms to examine temporal variations in nutrient concentrations, fluxes, and phase partitioning. Both NO3 and PO4 concentrations in the Yukon River were much lower than those of world rivers, with an average concentration of 2.43 ± 0.63 µM-N and 0.053 ± 0.040 µM-P, respectively. Si(OH)4 concentrations were more comparable to those of world rivers, with an average concentration of 82 ± 21 µM-Si. Integrated annual fluxes were 2.4 x 108 mole-NO3, 3.4 x 106 mole-PO4, and 8.7 x 109 mole-Si(OH)4, respectively. Nutrient discharge during the river ice open season contributed 73 to 95% of the annual flux depending on nutrient species. Within the total N pool transported by the Yukon River, dissolved inorganic N comprised 7 ± 4% and particulate N made up 25 ± 10%, while dissolved organic N (DON) was the dominant N species (with an average of 67 ± 10%). In contrast, P was predominantly partitioned in the particulate phase (with an average of 94 ± 6%), leaving 4 ± 5% of the total P in the dissolved organic phase and ~2 ± 1% in the dissolved inorganic phase. The partitioning of N and P indicates that the transformation between dissolved and particulate or inorganic and organic phases may play a critical role in controlling the flux of bioavailable nutrients and thus the nutrient dynamics in the Yukon River Basin and its coastal region. Nutrient specific fluxes normalized to drainage area in the Yukon River Basin were 0.57 mmole/m2/yr for NO3, 0.012 mmole/m2/yr for PO4, and ~19 mmole/m2/yr for Si(OH)4, respectively. The relatively low specific fluxes of NO3 and PO4 in the Yukon River Basin reflect its pristine status or little anthropogenic influence, whereas cold climate in the Arctic/subarctic region may be responsible for its lower Si(OH)4 specific flux, in agreement with a general trend of increasing Si specific flux with decreasing latitude in global river systems. A warming climate and thus deeper permafrost active layer in the Yukon River watershed would likely enhance the export flux of nutrients into the Bering Sea.

  49. Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Potential availability of sedimentary phosphorus to sediment resuspension in Florida Bay. Global Biogeochemical Cycles, 18(4):GB4008, 14 pp., doi:10.1029/2004GB002255 2004

    Abstract:

    Several studies have suggested that phosphorus is a limiting nutrient for seagrass and phytoplankton growth in much of Florida Bay. In fact, soluble reactive phosphate concentrations in Florida Bay waters can be as low as a few nM. Sediments represent the largest phosphorus reservoir because Florida Bay sediments are dominated by carbonate, which has a strong capacity to retain phosphorus. The supply of phosphorus to the water column from sediment resuspension is potentially important in providing the nutrients required for phytoplankton production. Applying an improved sequential extraction technique to sediments collected from 40 geographically representative stations in Florida Bay, this study provides the first detailed spatial distribution of total sedimentary phosphorus (TSP) and its partitioning into five chemically distinguishable pools in the surface, fine-grained sediments of the bay. A strong gradient of decreasing TSP concentration was observed from the west (14.6 µmol g-1) to east (1.2 µmol g-1) across the central bay. The spatial pattern of TSP is consistent with distribution of both seagrass and phytoplankton that are limited by available phosphorus in Florida Bay. Among the five pools, the authigenic carbonate fluorapatite, biogenic apatite and CaCO3-bound phosphorus account for the largest fraction (45%) of TSP, of which inorganic phosphorus is the dominant form, and organic phosphorus accounts for about 30% in the western and north central regions and less than 10% in other areas of Florida Bay. The second largest pools are the refractory organic phosphorus (24% of TSP) and reductant-soluble inorganic phosphorus (19% of TSP). Readily exchangeable phosphorus accounts for 8% of TSP, of which organic phosphorus is 60%. Detrital apatite phosphorus of igneous or metamorphic origin represents the smallest fraction, only 5% of TSP. Spatial distribution of phosphorus and iron in sediments indicates that external sources of these two essential plant nutrients to Florida Bay are spatially separated with phosphorus introduced by west coast waters across the western margin of Florida Bay and iron from freshwater flow into the eastern region.

  50. Darrow, B.P., J.J. Walsh, G.A. Vargo, R.T. Masserini, K.A. Fanning, and J.-Z. Zhang. A simulation study of the growth of benthic microalgae following the decline of a surface phytoplankton bloom. Continental Shelf Research, 23(14-15):1265-1283, doi:10.1016/S0278-4343(03)00130-4 2003

    Abstract:

    The West Florida continental shelf is an oligotrophic system for most of the year. An episodic chlorophyll plume has previously been observed in satellite imagery on the northern portion of the shelf during the spring months. The fate of the plume upon its decline in the late spring and early summer is unknown. Decreased chlorophyll levels and sustained nutrient stocks may be explained by sediment/water-column interactions, including the presence of benthic microalgae. A one-dimensional model, consisting of 16 state variables, is constructed to simulate the decline of a surface chlorophyll bloom in the northeastern Gulf of Mexico as measured during the Florida Shelf Lagrangian Experiment (FSLE). Results from a baseline simulation of two FSLE studies suggest that remineralized nutrients from the declining bloom are taken up by heterotrophic bacteria in the water-column and by benthic microalgae in the sediments. Perturbation experiments imply that low light levels, due to increased CDOM, do not have significant effects on the benthic microfloral community at mid-shelf locations.

  51. Lee, K., D.M. Karl, R. Wanninkhof, and J.-Z. Zhang. Global estimates of net carbon production in the nitrate-depleted tropical and subtropical oceans. Geophysical Research Letters, 29(19):1907, 4 pp., doi:10.1029/2001GL014198 2002

    Abstract:

    Nitrate availability is generally considered to be the limiting factor for oceanic new production and this concept is central in our observational and modeling efforts. However, recent time-series observations off Bermuda and Hawaii indicate a significant removal of total dissolved inorganic carbon (CT) in the absence of measurable nitrate. Here we estimate net carbon production in nitrate-depleted tropical and subtropical waters with temperatures higher than 20°C from the decrease in the salinity normalized CT inventory within the surface mixed layer. This method yields a global value of 0.8 ? 0.3 petagrams of carbon per year (Pg C yr-1, Pg = 1015 grams), which equates to a significant fraction (20-40%) of the recent estimates (20-4.2 Pg C yr-1) of total new production in the tropical and subtropical oceans (Emerson et al., 1997; Lee, 2001). The remainder is presumably supported by upward flux of nutrients into the euphotic zone via eddy diffusion and turbulent mixing processes or lateral exchange. Our calculation provides the first global-scale estimate of net carbon production in the absence of measurable nitrate. We hypothesize that it is attributable to dinitrogen (N2) fixing microorganisms, which can utilize the inexhaustible dissolved N2 pool and thereby bypass nitrate limitation.

  52. Yvon-Lewis, S.A., J.H. Butler, E.S. Saltzman, P.A. Matrai, D.B. King, R. Tokarczyk, R.M. Moore, and J.-Z. Zhang. Methyl bromide cycling in a warm-core eddy of the North Atlantic. Global Biogeochemical Cycles, 16(4):1141, 6 pp., doi:10.1029/2002GB001898 2002

    Abstract:

    We conducted a detailed investigation of the evolution of methyl bromide concentrations, degradation rates, and ventilation rates for 26 days in a naturally contained, warm-core eddy of the North Atlantic Ocean. This is the first study of the oceanic cycling of methyl bromide in a natural, contained system with a complete suite of supporting measurements of physical and chemical variables. Methyl bromide concentrations in the mixed layer ranged from 2.3 to 4.2 nmol m-3, degradation rates ranged from 0.1 to 0.9 nmol m-3 d-1, net sea-to-air exchange rates ranged from 0 to 0.5 nmol m-3 d-1, and net loss rates through the thermocline were less than 0.1 nmol m-3 d-1. From a mass balance for methyl bromide in the mixed layer, we calculated production rates ranging from -3 d-1. The median of this range, 0.48 nmol m-3 d-1, is higher than the ~0.15 nmol m-3 d-1 necessary to maintain the reported global oceanic emission of 56 Gg yr-1. This is reasonable, because our study area was supersaturated in methyl bromide, whereas the ocean as a whole is undersaturated.

  53. Zhang, J.-Z., and F.J. Millero. Comment on "A kinetic study of the oxidation of S(IV) in seawater." Environmental Science and Technology, 36(4):817, doi:10.1021/es011338b 2002

    Abstract:

    No abstract.

  54. Zhang, J.-Z., and J. Chi. Automated analysis of nanomolar concentrations of phosphate in natural waters with liquid waveguide. Environmental Science and Technology, 36(5):1048-1053, doi:10.1021/es011094v 2002

    Abstract:

    Concentrations of phosphate in natural waters are often below the detection limits of conventional nutrient auto-analyzers by either gas-segmented continuous flow analysis or flow injection analysis. A liquid waveguide capillary flow cell has been used to extend the sensitivity of a conventional auto-analyzer for automated analysis of nanomolar concentrations of phosphate in natural waters. Total reflection of light can be achieved within the liquid core of the flow cell, as the refractive index of cell wall coated with Teflon 1600 is lower than water. This property allows the manufacturers to construct long liquid waveguide capillary flow cells in a helical, rather than linear shape, with compact dimensions. A small sample volume is required because the internal volume of a 2-m long capillary flow cell is only approximately 0.5 cm3. Adaptation of this long flow cell to auto-analyzers significantly enhances the sensitivity of automated colorimetric analysis of phosphate with molybdenum blue method, allowing for accurate and precise determination of nanomolar concentrations of phosphate in natural waters. The advantages of this technique are a low detection limit (0.5 nM), small sample volume (2 mL), high precision (2% at 10 nM levels), and automation for rapid analysis of a large number of samples.

  55. Zhang, J.-Z., G.A. Berberian, and R. Wanninkhof. Long-term storage of natural water samples for dissolved oxygen determination. Water Research, 36(16):4165-4168, doi:10.1016/S0043-1354(02)00093-3 2002

    Abstract:

    A method for preserving natural water samples for dissolved oxygen analysis is recommended. The conventional method of using greased glass stoppers has been found to cause a 12% increase in oxygen concentration over a one-month period as a result of evaporation of water sample through micro-gaps and concurrent intrusion of air into the water sample bottles. Sealing the sample bottles with water has been found to be the optimal storage method. It permits a 100.2 ? 0.3% recovery of dissolved oxygen concentration from storage seawater samples over four months.

  56. Daly, K.L., W.O. Smith, G.C. Johnson, G.R. DiTullio, D.R. Jones, C.W. Mordy, R.A. Feely, D.A. Hansell, and J.-Z. Zhang. Hydrography, nutrients, and carbon pools in the Pacific sector of the Southern Ocean: Implications for carbon flux. Journal of Geophysical Research, 106(C4):7107-7124, doi:10.1029/1999JC000090 2001

    Abstract:

    We investigated the hydrography, nutrients, and dissolved and particulate carbon pools in the western Pacific sector of the Antarctic Circumpolar Current (ACC) during austral summer 1996 to assess the region's role in the carbon cycle. Low fCO2 values along two transects indicated that much of the study area was a sink for atmospheric CO2. The fCO2 values were lowest near the Polar Front (PF) and the Subtropical Front (STF), concomitant with maxima of chlorophyll-a and particulate and dissolved organic carbon. The largest biomass accumulations did not occur at fronts, which had high surface geostrophic velocities (20-51 cm s-1), but in relatively low velocity regions near fronts or in an eddy. Thus, vertical motion and horizontal advection associated with fronts may have replenished nutrients in surface waters but also dispersed phytoplankton. Although surface waters north of the PF have been characterized as a "high nutrient-low chlorophyll" region, low silicic acid (Si) concentrations (2-4 µM) may limit production of large diatoms and, therefore, the potential carbon flux. Low concentrations (4-10 µM Si) at depths of winter mixing constrain the level of Si replenishment to surface waters. It has been suggested that an increase in aeolian iron north of the PF may increase primary productivity and carbon export. Our results, however, indicate that while diatom growth and carbon export may be enhanced, the extent ultimately would be limited by the vertical supply of Si. South of the PF, the primary mechanism by which carbon is exported to deep water appears to be through diatom flux. We suggest that north of the PF, particulate and dissolved carbon may be exported primarily to intermediate depths through subduction and diapycnal mixing associated with Subantarctic Mode Water and Antarctic Intermediate Water formation. These physical-biological interactions and Si dynamics should be included in future biogeochemical models to provide a more accurate prediction of carbon flux.

  57. Millero, F.J., F. Huang, X. Zhu, X. Liu, and J.-Z. Zhang. Adsorption and desorption of phosphate on the calcite and aragonite in seawater. Aquatic Geochemistry, 7(1):33-56, doi:10.1023/A:1011344117092 2001

    Abstract:

    The adsorption and desorption of phosphate on calcite and aragonite were investigated as a function of temperature (5-45°C) and salinity (0-40) in seawater pre-equilibrated with CaCO3. An increase in temperature increased the equilibrium adsorption; whereas an increase in salinity decreased the adsorption. Adsorption measurements made in NaCl were lower than the results in seawater. The higher values in seawater were due to the presence of Mg2+ and Ca2+ ions. The increase was five times greater for Ca2+ than Mg2+. The effects of Ca2+ and Mg2+ are diminished with the addition of SO42-, apparently due to the formation of MgSO4 and CaSO4 complexes in solution and/or SO42- adsorption on the surface of CaCO3. The adsorbed Ca2+ and Mg2+ on CaCO3 (at carbonate sites) may act as bridges to PO43- ions. The bridging effect of Ca2+ is greater than Mg2+, apparently due to the stronger interactions of Ca2+ with PO43-. The apparent effect of salinity on the adsorption of PO4 was largely due to changes in the concentration of HCO3- in the solutions. An increase in the concentration of HCO3- caused the adsorption of phosphate to decrease, especially at low salinities. The adsorption at the same level of HCO3- (2 mM) was nearly independent of salinity. All of the adsorption measurements were modeled empirically using a Langmuir-type adsorption isotherm [[PO4]ad = Km Cm [PO4]T /(1 + Km [PO4]T)], where [PO4]ad and [PO4]T are the adsorbed and total dissolved phosphate concentrations, respectively. The values of Cm (the maximum monolayer adsorption capacity, mol/g) and Km (the adsorption equilibrium constant, g/(mol)) over the entire temperature (t, °C) and salinity (S) range were fitted to [Cm = 17.067 + 0.1707t - 0.4693S + 0.0082S2 (sigma = 0.7)] [ln Km = -2.412 + 0.0165t - 0.0004St - 0.0008S2 (sigma = 0.1)]. These empirical equations reproduce all of our measurements of [PO4]ad up to 14 µmol/g and within ?0.7 µmol/g. The kinetic data showed that the phosphate uptake on carbonate minerals appears to be a multi-step process. Both the adsorption and desorption were quite fast in the first stage (less than 30 min) followed by a much slower process (lasting more than one week). Our results indicate that within 24 hours aragonite has a higher sorption capacity than calcite. The differences between calcite and aragonite become smaller with time. Consequently, the mineral composition of the sediments may affect the short-term phosphate adsorption and desorption on calcium carbonate. Up to 80% of the adsorbed phosphate is released from calcium carbonate over one day. The amount of PO4 left on the CaCO3 is close to the equilibrium adsorption. The release of PO4 from calcite is faster than from aragonite. Measurements with Florida Bay sediments produced results between those for calcite and aragonite. Our results indicate that the calcium carbonate can be both a sink and source of phosphate in natural waters.

  58. Millero, F.J., W.T. Hiscock, F. Huang, M. Roche, and J.-Z. Zhang. Seasonal variation of the carbonate system in Florida Bay. Bulletin of Marine Science, 68(1):101-123, 2001

    Abstract:

    The carbonate system has been studied in the Florida Bay from 1997 to 2000. Measurements of pH, total alkalinity (TA), and total inorganic carbon dioxide (TCO2) were made from 20 stations in the Bay and used to calculate the partial pressure of carbon dioxide (pCO2) and the saturation states of aragonite (ΩArg) and calcite (ΩCal). The results were found to correlate with the salinity. The pH was low and the pCO2 was high for the freshwater input from the mangrove fringe due to the photochemical and biological oxidation of organic material. The TA and TCO2 for the freshwater input are higher than seawater due to the low values of pH and Ω. The pH was high and the pCO2 was low in November in regions where the chlorophyll is high due to biological production. During the summer when the salinity is the highest, the normalized values of TA and TCO2 were lower than average seawater, due to the inorganic precipitation of CaCO3 caused by the resuspension of sediments or the biological loss by macroalgae. A transect across the mangrove fringe near the outflow of Taylor Slough shows that PO4 and TA increases as the freshwater enters the Bay. This is thought to be due to the dissolution of CaCO3 in the low pH waters from the bacterial and photo oxidation of plant material.

  59. Peltola, E., K. Lee, R.H. Wanninkhof, R. Feely, M. Roberts, D. Greeley, M.O. Baringer, G. Johnson, J. Bullister, C. Mordy, J.-Z. Zhang, P. Quay, F. Millero, D. Hansell, and P. Minnett. Chemical and hydrographic measurements on a Climate and Global Change Cruise along 24°N in the Atlantic Ocean WOCE Section A5R (repeat) during January-February 1998. NOAA Data Report, OAR-AOML-41 (PB2001-107645), 210 pp., 2001

    Abstract:

    This document contains data and metadata from a zonal cruise along nominally 24.5°N in the Atlantic Ocean from Las Palmas, Canary Islands in Spain to Miami, Florida. The cruise took place from January 23 to February 24, 1998 aboard the NOAA Ship Ronald H. Brown under auspices of the National Oceanic and Atmospheric Administration (NOAA). This report presents the analytical and quality control procedures performed during the cruise and bottle data from the cruise. The research was sponsored by the NOAA Climate and Global Change Program under: (i) The Ocean-Atmosphere Carbon Exchange Study (OACES); and (ii) the World Ocean Circulation Experiment (WOCE) repeat hydrography program. Samples were taken from up to 36 depths at 130 stations. The data presented in this report includes the analyses of water samples for: salinity, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity of carbon dioxide (fCO2), total alkalinity (TA), pH, total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), chlorofluorocarbons, and stable carbon isotopic ratio of DIC (13C/12C). Basic hydrographic parameters, pressure, CTD salinity, temperature and the calculated potential temperature, and potential density are included as well.

  60. Zhang, J.-Z. Oxidation of hydrogen sulfide by various oxidants in natural waters. Trends in Geochemistry, 1(2000):53-68, 2001

    Abstract:

    This article reviews the literature on the oxidation of H2S by various oxidants, including oxygen, hydrogen peroxide, iodate, chromate, ferrate, Fe(III) hydroxides, and Mn(IV) oxides, in natural waters. The rates of H2S oxidation increased with oxidants in an order of chromate, oxygen, hydrogen peroxide, iodate, Fe(III) hydroxides, Mn(IV) oxides, and ferrate. Effect of pH on the rates of oxidation by various oxidants indicated that HS- is a reactive species while H2S is less reactive or, in some cases, non-reactive. The oxidation by oxygen has been a subject of extensive studies and its rates have been measured over a wide range of environmental conditions such as pH, temperature, and salinity. Dissolved and particulate metals have a significant effect on the rates of oxidation and the product formation. The reaction conditions and resulting product formation (S, Sn2-, SO32-, S2O32- and SO42-) were examined to unravel the reaction pathway.

  61. Zhang, J.-Z., and C.J. Fischer. The role of sediment resuspension in the phosphorus cycle in Florida Bay. Proceedings, 2001 Florida Bay and Adjacent Marine Systems Science Conference, Key Largo, FL, April 23-26, 2001. University of Florida, 98-99, 2001

    Abstract:

    The mass mortality of sea grass and frequent algal blooms in Florida Bay are a result of eutrophication. Existing data indicate that phosphorus is the limiting nutrient, while nitrogen is abundant. Therefore, the supply of phosphorus is critical to the onset and persistence of phytoplankton blooms in Florida Bay. Biogenic calcium carbonates are major components of the sediments (>90%) in the Florida Bay. Our studies have shown that phosphorus is strongly adsorbed on the surface of calcium carbonate sediment. Sediments in Florida Bay can easily be suspended by storms and tidal mixing due to shallow water depth (~3 m). Phosphorus cycling processes such as release from adsorption to and coprecipitation with suspended sediment may play an important role in the supply phosphorus to phytoplankton bloom. Our project has been focused on the following three aspects: (1) The time scales of phosphate availability through sediment resuspension in Florida Bay water and kinetic of interaction of sedimentary phosphorus with seawater; (2) the distribution coefficients for phosphorus partitioning between sediment/seawater in Florida Bay; and (3) the reactivity and partitioning of various pools of sedimentary phosphorus in Florida Bay surface sediments.

  62. Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Continuous flow analysis of phosphate in natural waters using hydrazine as a reductant. International Journal of Environmental Analytical Chemistry, 80(1):61-73, doi:10.1080/03067310108044386 2001

    Abstract:

    The use of hydrazine to reduce 12-molybdophosphoric acid to phosphomolybdenum blue in continuous flow analysis of phosphate in natural water samples is characterized. Using hydrazine in gas-segmented continuous flow phosphate analysis minimizes coating and silicate interference in comparison with using ascorbic acid. The addition of Sb to the molybdate reagent increases sensitivity at temperatures greater than 50°C but causes severe additional coating. The degree of coating was found to be a function of pH. Minimal coatings were achieved at a final solution pH of 0.5. Silicate interference was found to increase dramatically with color development temperature. At room temperature no detectable silicate interference was found. We recommend hydrazine in preference to ascorbic acid for gas-segmented continuous flow phosphate analysis with optimal reaction conditions of room temperature color development and a final solution pH of 0.5.

  63. Zhang, J.-Z., C.R. Kelble, and F.J. Millero. Gas-segmented continuous flow analysis of iron in water with a long liquid waveguide capillary flow cell. Analytica Chimica Acta, 438(1-2):49-57, doi:10.1016/S0003-2670(01)01031-5 2001

    Abstract:

    A long liquid waveguide capillary flow cell has been successfully adapted to a gas-segmented continuous flow auto-analyzer for trace analysis of iron in water. The flow cell was made of new material, Teflon AF-2400, which has a refractive index (1.29) lower than water (1.33). Total reflection of light can be achieved provided that the incident angle at each reflection on the water/Teflon interface is greater than the critical angle. Teflon AF-2400 is superior to currently used materials in both refractivity and mechanical stability. This allows for construction of a long liquid waveguide capillary flow cell in a helical, rather than linear shape, with compact dimensions. Since the internal volume of a 2 m-long, 550 ?m ID liquid waveguide capillary flow cell is only approximately 0.5 cm3, a small sample volume is required. Utilization of this long flow cell significantly enhances the sensitivity of automated colorimetric analysis of iron by the ferrozine method, allowing for accurate determination of nanomolar concentrations of iron in natural waters. The advantages of this technique are low detection limit (0.1 nM), small sample volume (2 ml), high precision (1%), and automation for rapid analysis of a large number of samples. This technique is applicable to any gas-segmented continuous flow analysis or flow injection analysis with spectrophotometric detection.

  64. Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. Enhanced new production observed from the diurnal cycle of nitrate in an oligotrophic anticyclonic eddy. Geophysical Research Letters, 28(8):1579-1582, doi:10.1029/2000GL012065 2001

    Abstract:

    A diurnal study in an anticyclonic eddy provides the first evidence of nutrient dynamics consistent with the observed trends in solar radiation, oxygen concentration changes, and estimates of the eddy diffusive flux of nitrate from nitracline. A new production rate of 24 mmol C m-2 d-1 was determined from nitrate inventory changes at nM levels in the mixed layer using a liquid waveguide technique combined with eddy diffusion estimates across the base of the mixed layer from temporal changes in the vertical penetration of SF6. The new production supported by nitrate from deepening of the mixed layer after storm events is two times larger than that from the daily diffusive flux. Our results demonstrate that new production in the oligotrophic ocean can be enhanced by a supply of nitrate through the eddy turbulence-induced diffusive flux and entrainment during storms.

  65. Zhang, J.-Z. Shipboard automated determination of trace concentrations of nitrite and nitrate in oligotrophic water by gas-segmented continuous flow analysis with a liquid waveguide capillary flow cell. Deep-Sea Research, Part I, 47(6):1157-1171, doi:10.1016/S0967-0637(99)00085-0 2000

    Abstract:

    Incorporation of a liquid waveguide capillary flow cell to a gas-segmented continuous flow auto-analyzer significantly enhances the sensitivity of automated colorimetric analysis. Nanomolar concentrations of nitrite and nitrate in oligotrophic surface seawater can be accurately determined. The advantages of this technique are low detection limit, high precision, and automation for rapid analysis of a large number of samples. This technique has been successfully used on shipboard measurements of about 1000 seawater samples during a one-month cruise in North Atlantic.

  66. Zhang, J.-Z. The use of pH and buffer intensity to quantify the carbon cycle in the ocean. Marine Chemistry, 70(1-3):121-131, doi:10.1016/S0304-4203(00)00024-4 2000

    Abstract:

    The pH of seawater is governed by the content of total carbon dioxide and ionic equilibra between hydrogen ions and various inorganic carbon species in seawater. Buffer intensity is defined as a measure of the ability of seawater to accommodate the addition of acid or base without appreciable pH change. It can be calculated from pH and total carbon dioxide of seawater. pH data in conjunction with buffer intensity can be used to quantify the carbon cycle in the ocean. The total amount of acid that has been released or consumed by any biogeochemical processes can be calculated from the change in pH multiplied by buffer intensity of seawater, dCH= d(β-pH). This approach has been used to quantify the remineralization process in the Antarctic Intermediate Water in the South Pacific. Based on the observational data (pH, total carbon dioxide, O2, and nutrient measurements on P18 cruise), calculated elemental remineralization ratios are 173, 107, and 14.3 for O/P, C/P and N/P, respectively. The dissolution of calcium carbonate accounts for 21.5% of carbon increased from the remineralization in the Antarctic Intermediate Water.

  67. Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Comparison of open tubular cadmium reactors and packed cadmium columns in automated gas-segmented continuous flow nitrate analysis. International Journal of Environmental Analytical Chemistry, 76(2):99-113, doi:10.1080/03067310008034123 2000

    Abstract:

    Detailed procedures are provided for preparing packed cadmium columns to reduce nitrate to nitrite. Experiments demonstrated the importance of conditioning both open tubular cadmium reactor (OTCR) and packed copper-coated cadmium columns to achieve 100% reduction efficiency. The effects of segmentation bubbles in the OTCR upon reduction efficiency and baseline noise in nitrate analysis are investigated using an auto-analyzer. Metal particles derived from segmentation bubbles in OTCR result in interference with continuous flow analyses. Therefore, packed columns are recommended for determination of low level nitrate in natural waters.

  68. Zhang, J.-Z., C.W. Mordy, L.I. Gordon, A. Ross, and H.E. Garcia. Technical comment on “Temporal trends in deep ocean Redfield ratios” by Pahlow and Riebesell. Science, 289(5486):1839, 2000

    Abstract:

    No abstract.

  69. Zhang, J.-Z., R.H. Wanninkhof, and K. Lee. New production in oligotrophic waters: Estimation based on diel cycle of nitrate. Proceedings, Joint Global Ocean Flux Study (JGOFS) Open Science Conference, Bergen, Norway, April 13-17, 2000. JGOFS International Project Office, 76-77, 2000

    Abstract:

    New production can be estimated from accurate measurements of inventory change in nitrate at nM levels in the photic zone. A strong diel cycle was observed in nitrate concentrations in response to photosynthesis in the eastern North Atlantic during the GASEX-98 cruise. During a diel study, nitrate concentration was 92 nM in the morning and decreased to 12 nM by 6 p.m. It increased after dark, presumably due to the diffusive flux from the nitracline. Oxygen showed a similar diel cycle with a change in concentration of about 2 µM. The vertical eddy diffusivity was derived from temporal changes in concentrations of a deliberate tracer, SF6, below the mixed layer. Together with vertical nitrate distributions, the nitrate flux from nitracline throughout the nighttime can account for a nitrate concentration of 102 nM by morning, which is in good agreement with measured nitrate of 92 nM at 6 a.m. The new production estimated from changes of nitrate inventory in the photic zone during the day was 28 mmole C/m2 d. Increases in the mixed layer nitrate were observed during storm events that deepened the mixed layer and brought the nitrate to the surface. The storm-induced nitrate disappeared within two days, indicating a rapid uptake by phytoplankton. The relative importance of sporadic storm events versus daily diffusive flux in supply nitrate to new production can be estimated based on nitrate inventory changes in the photic zone.

  70. Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Laboratory glassware as a contaminant in silicate analysis of natural water samples. Water Research, 33(12):2879-2883, doi:10.1016/S0043-1354(98)00508-9 1999

    Abstract:

    When glassware is used for the storage of water samples, reagents, and standard solutions, dissolution of silicate from the glass containers can contaminate the samples. Experimental results demonstrate that dissolution from glassware can introduce micromolar silicate within a few hours. The extent of dissolution depends upon contact time, salinity, and pH of the solution, and the size and shape of the containers.

  71. Zhang, J.-Z., C.J. Fischer, and P.B. Ortner. Optimization of performance and minimization of silicate interference in continuous flow phosphate analysis. Talanta, 49(2):293-304, doi:10.1016/S0039-9140(98)00377-4 1999

    Abstract:

    Specific reaction conditions for automated continuous flow analysis of phosphate are optimized in regard to minimizing coating and silicate interference, while maintaining high sensitivity. Use of Sb in the reagent increases sensitivity and yields absorbances with little temperature dependence. Coating can be minimized by using a final solution at a pH >0.5. At final pH of 0.78, there is maximum interference from silicate in the sample. We recommend, therefore, as an optimal reaction condition with minimal silicate interference, the use of Sb, a final solution pH of 1.00, room temperature for the reaction, and a [H+]/Mo ratio of 70. An equation is provided to correct silicate interference in high precision phosphate determination.

  72. Millero, F.J., W. Yao, K. Lee, J.-Z. Zhang, and D.M. Campbell. Carbonate system in the waters near the Galapagos Islands. Deep-Sea Research, Part II, 45(6):1115-1134, doi:10.1016/S0967-0645(98)00016-2 1998

    Abstract:

    During the IRONEX cruise in the equatorial Pacific Ocean, the carbonate parameters TA (total alkalinity), TCO2 (total inorganic carbon), pH, and fCO2 (fugacity of CO2), were determined both in a small (8 × 8 km) patch of water fertilized with Fe and in the waters around the Galapagos Islands. The CO2 parameters, along with hydrographic properties, were found to be uniform in the surface waters of the study area before the addition of iron. A significant decrease of the surface TCO2 (7 µmol kg-1) and fCO2 (11 µatm) in the patch was detected within 48 h of the iron release. This decrease, however, did not continue and was lower than expected from the complete utilization of NO3- due to the addition of iron. The shipboard iron addition experiments (3 nM fe) resulted in a continual decrease of TCO2 (up to 48 µmol kg-1) and complete consumption of the nutrients. A good correlation was found between TCO2, pH, and fCO2 with temperature in the surface waters around the Galapagos Islands. The salinity (S = 35) normalized alkalinities were quite uniform (NTA = 2310 ± 9 mol kg-1) throughout the region. The effect of high primary production on the CO2 system in the downstream plume is overshadowed by the upwelling waters with high CO2.

  73. Peltola, E., R. Wanninkhof, R. Molinari, B.E. Huss, R. Feely, J. Bullister, J.-Z. Zhang, F. Chavez, A. Dickson, A. Ffield, D. Hansell, F. Millero, P. Quay, R. Castle, G. Thomas, R. Roddy, T. Landry, M. Roberts, H. Chen, D. Greeley, K. Lee, M. Roche, J.A. Goen, F. Millero, K. Buck, M. Kelly, F. Menzia, A. Huston, T. Waterhouse, S. Becker, and C. Mordy. Chemical and hydrographic measurements during the Indian Ocean I8 repeat cruise (IR8N) in September and October 1995. NOAA Data Report, ERL-AOML-34 (PB99-126948), 176 pp., 1998

    Abstract:

    This document contains data and metadata from the I8 repeat cruise in the Indian Ocean cruise in 1995 from Fremantle, Australia to Male in the Maldives. From September 22 to October 25, 1995, the National Oceanic and Atmospheric Administration (NOAA) sponsored an oceanographic research cruise conducted aboard the NOAA Ship Malcolm Baldrige. This report presents the analytical and quality control procedures and data from the cruise that was conducted for the Ocean-Atmosphere Carbon Exchange Study (OACES). Samples were taken at 101 stations. The data presented in this report includes hydrography, nutrients, total dissolved inorganic carbon dioxide (DIC), fugacity of carbon dioxide (fCO2), total alkalinity (TA), pH, total organic carbon and nitrogen data (TOC/TON), chlorofluorocarbons, 13C, and biological parameters.

  74. Zhang, J.-Z., and P.B. Ortner. Effect of thawing conditions on the recovery of reactive silicic acid from frozen natural water samples. Water Research, 32(8):2553-2555, doi:10.1016/S0043-1354(98)00005-0 1998

    Abstract:

    A method for thawing frozen samples for silicic acid analysis is recommended. The maximum recovery of silicic acid is achieved by thawing the frozen samples in a refrigerator (at 4°C) in the dark for at least four days. This method significantly improves the recovery of silicic acid from frozen fresh water samples. It also permits close to 100% recovery of reactive silicic acid from frozen seawater samples even after three months storage.

  75. Lamb, M.F., J.L. Bullister, R.A. Feely, G.C. Johnson, D.P. Wisegarver, B. Taft, R.H. Wanninkhof, K.E. McTaggart, K.A. Krogslund, C.W. Mordy, K. Hargreaves, D. Greeley, T. Lantry, H. Chen, B.E. Huss, F.J. Millero, R.H. Byrne, D.A. Hansell, F.P. Chavez, P.D. Quay, P.R. Guenther, J.-Z.Zhang, W. Gardner, M.J. Richardson, and T.-H. Peng. Chemical and hydrograph measurements in the eastern Pacific during the CGC94 expedition (WOCE section P18). NOAA Data Report, ERL-PMEL-61 (PB97-158075), 235 pp., 1997

    Abstract:

    NOAA's Climate and Global Change (CGC) Program sponsored a major cooperative effort in the eastern Pacific along WOCE Hydrographic Programme Line P18 from 26 January to 27 April 1994. The first leg (Leg 1) consisted of a transit from Seattle to Punta Arenas, Chile. The second leg (Leg 2) covered hydrographic stations from 67°S, 103°W to 27°S, 103°. The third leg (Leg 3) included stations between 26.5°S, 103°W and 23°N, 110°W. Full depth CTD/rosette casts were made to the ocean bottom at a nominal spacing of 30 miles on Legs 2 and 3. Water samples were collected on the casts for analyses of concentrations of salinity, DO, CFC, fCO2, DIC, TAlk, pH, TOC/TON, 13C/12C isotopes, and nutrients. Biological parameters were also sampled, and included biogenic Si, chlorophyll-a, phaeopigments, and primary productivity.

  76. Wanninkhof, R.H., G. Hitchcock, W.J. Wiseman, G. Vargo, P.B. Ortner, W.E. Asher, D.T. Ho, P. Schlosser, M.-L. Dickson, R. Masserini, K. Fanning, and J.-Z. Zhang. Gas exchange, dispersion, and biological productivity on the West Florida Shelf: Results from a Lagrangian tracer study. Geophysical Research Letters, 24(14):1767-1770, doi:10.1029/97GL01757 1997

    Abstract:

    A Lagrangian tracer study was performed on the West Florida Shelf in April 1996 using deliberately injected trace gases. Although such studies have been performed previously, this work is the first where the deliberate tracers, in conjunction with carbon system parameters, are used to quantify changes in water column carbon inventories due to air-sea exchange and net community metabolism. The horizontal dispersion and the gas transfer velocity were determined over a period of 2 weeks from the change in both the concentrations and the concentration ratio of the two injected trace gases, sulfur hexafluoride (SF6) and helium-3 (3He). Horizontal diffusion estimates were about an order of magnitude greater than calculated from empirical equations, and the difference is attributed to vertical shear. The second moment of the patch grew to 1.6 × 103 km2 over a period of 11 days. The gas transfer velocity, normalized to CO2 exchange at 20°C, was 8.4 cm hr-1 at an average wind speed, U10, of 4.4 m s-1 for the duration of the experiment, which is in good agreement with empirical estimates. Remineralization rates exceeded productivity, causing an increase in dissolved inorganic carbon of about 1 µmol kg-1 day-1 in the water column. During this period of senescence, 80% of the increase in inorganic carbon is attributed to community remineralization and 20% due to invasion of atmospheric CO2. This net remineralization is in accordance with in situ and on-deck incubation experiments.

  77. Zhang, J.-Z. Distinction and quantification of carry-over and sample interaction in gas segmented continuous flow analysis. Journal of Automatic Chemistry, 19(6):205-212, doi:10.1155/S1463924697000254 1997

    Abstract:

    The formulae for calculation of carry-over and sample interaction are derived for the first time in this study. A scheme proposed by Thiers et al. (two samples of low concentration followed by a high concentration sample and low concentration sample) is verified and recommended for the determination of the carry-over coefficient. The derivation demonstrates that both widely used schemes of a high concentration sample followed by two low concentration samples, and a low concentration sampled followed by two high concentration samples, actually measure the sum of the carry- over coefficient and sample interaction coefficient. A scheme of three low concentration samples followed by a high concentration sample is proposed and verified for determination of the sample interaction coefficient. Experimental results indicate that carry-over is a strong function of cycle time and a weak function of ratio of sample time to wash time. Sample dispersion is found to be a function of sample time. Fitted equations can be used to predict the carry-over, absorbance, and dispersion given sample times, and wash times for an analytical system. Results clearly show the important role of intersample air segmentation in reducing carry-over, sample interaction, and dispersion.

  78. Zhang, J.-Z., and G.A. Berberian. Method 366.0: Determination of dissolved silicate in estuarine and coastal waters by gas segmented continuous flow colorimetric analysis. In Methods for the Determination of Chemical Substances in Marine and Estuarine Environmental Matrices, Second Edition. U.S. Environmental Protection Agency, EPA-600-R-97-072, 13 pp., 1997

    Abstract:

    No abstract.

  79. Zhang, J.-Z., P.B. Ortner, and C.J. Fischer. Method 353.4: Determination of nitrate and nitrite in estuarine and coastal waters by gas segmented continuous flow colorimetric analysis. In Methods for the Determination of Chemical Substances in Marine and Estuarine Environmental Matrices, Second Edition. U.S. Environmental Protection Agency, EPA-600-R-97-072, 20 pp., 1997

    Abstract:

    No abstract.

  80. Zhang, J.-Z., P.B. Ortner, C.J. Fischer, and L.D. Moore. Method 349.0: Determination of ammonia in estuarine and coastal waters by gas segmented continuous flow colorimetric analysis. In Methods for the Determination of Chemical Substances in Marine and Estuarine Environmental Matrices, Second Edition. U.S. Environmental Protection Agency, EPA-600-R-97-072, 16 pp., 1997

    Abstract:

    No abstract.

  81. Millero, F.J., J.-Z. Zhang, K. Lee, J. Aicher, S. Mane, S. Olivella, D.O. Medina, and P.A. Steinberg. Ph and total alkalinity measurements in the North Atlantic. University of Miami Technical Report, RSMAS-95-004, 81 pp., 1995

    Abstract:

    This report gives the results of our pH (spectrophotometry and potentiometry), total alkalinity (TA), and total inorganic carbon dioxide (TCO2) measurements made in the North Atlantic during the Joint Global Ocean Flux Study (JGOFS) sponsored by the National Oceanic and Atmospheric Administration (NOAA). Measurements of TA on 91 samples of Certified Reference Materials (CRMs) with the three cells at sea indicate that the systems have a reproducibility of ±3 µmol/kg in TA. The resulting pH, TA, and TCO2 are thought to be precise to ±0.002 (spectrophotometry) and ±0.01 (potentiometry) in pH, ±3 µmol kg-1 in TCO2, and ±3 µmol kg-1 in TA. Our titration results will be combined with NOAA measurements of TCO2 (coulometry) and fCO2 to characterize the CO2 system in the North Atlantic.

  82. Millero, F.J., W. Yao, K. Lee, J.-Z. Zhang, and D.M. Campbell. The carbonate system near the Galapagos Islands. University of Miami Technical Report, RSMAS-95-001, 104 pp., 1995

    Abstract:

    During the IRONEX cruise and theh PlumEX experiments around the Galapagos Islands, measurements were made on the components of the carbonate system. The carbonate parameters pH, TA (total alkalinity), TCO2 (total carbon dioxide), and fCO2 (fucacity of CO2) were determined. The pH measurements (±0.002) were made using spectrophotometric techniques, the TA (±2 µmol kg-1) measurements were made by potentiometric titrations, the TCO2 (±2 µmol kg-1) were determined by coulometry and the fCO2 in the surface waters (±2 µatm) was determined using an infrared detector. A significant decrease of the surface TCO2 (7 µmol kg-1) and fCO2 (11 µatm) in the Fe patch was detected within 48 hours of the iron release. This decrease, however, did not continue. A good correlation was found between TCO2, pH, and fCO2 with temperature in the surface waters around the Galapagos Islands. The effect of high primary production on the CO2 system in the downstream plume is overshadowed by the upwelling waters with high CO2.

  83. Martin, J.H., K.H. Coale, K.S. Johnson, S.E. Fitzwater, R.M. Gordon, S.J. Tanner, C.N. Hunter, V.A. Elrod, J.L. Nowicki, T.L. Coley, R.T. Barber, S. Lindley, A.J. Watson, K. Van Scoy, C.S. Law, M.I. Liddicoat, R. Ling, T. Stanton, J. Stockel, C. Collins, A. Anderson, R. Bidigare, M. Ondrusek, M. Latasa, F.J. Millero, K. Lee, W. Yao, J.-Z. Zhang, G. Friederich, C. Sakamoto, F. Chavez, K. Buck, Z. Kolber, R. Greene, P. Falkowski, S.W. Chisholm, F. Hoge, R. Swift, J. Yungel, S. Turner, P. Nightingale, A. Hatton, P. Liss, and N.W. Tindale. Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean. Nature, 371(6493):123-129, doi:10.1038/371123a0 1994

    Abstract:

    The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km2 in the open equatorial Pacific Ocean with iron. This resulted in a doubling of plant biomass, a threefold increase in chlorophyll, and a fourfold increase in plant production. Similar increases were found in a chlorophyll-rich plume downstream of the Galapagos Islands, which was naturally enriched in iron. These findings indicate that iron limitation can control rates of phytoplanton productivity and biomass in the ocean.

  84. Millero, F.J., J.-Z. Zhang, D.M. Campbell, W. Yao, K. Lee, M. Helmer, S. Mane, S. Olivella, S. Cass, D.G. Purkerson, J. Aicher, P.A. Steinberg, and D. Medina. Total alkalinity measurements in the eastern equatorial Pacific. University of Miami Technical Report, RSMAS-94-005, 229 pp., 1994

    Abstract:

    In 1992, we made measurements on the carbonate system on two cruises (spring and fall) in the eastern equatorial Pacific during the Joint Global Ocean Flux Study (JGOFS) sponsored by the National Oceanic and Atmospheric Administration (NOAA). This report gives the results of our pH, total alkalinity (TA), and total inorganic carbon dioxide (TCO2) measurements made during the spring and fall cruises. The results were obtained by a potentiometric titration of seawater with HCl acid. Measurements on the Certified Reference Materials during the cruise with the three cells indicate that the systems have a reproducibility of ± 2-4 µmol kg-1 in TA. The titration values of TCO2 determined on the Certified Reference Materials and the samples collected at sea were about 20 ± 6 µmol kg-1 (spring) and 17 ± 6 µmol kg-1 (fall) too high. This offset in TCO2 is independent of depth and is due to the non-Nernstian Behavior of the electrodes. The measured values of pH, TA, and TCO2 are thought to be precise to ± 0.01 in pH, ± 3 µmol kg-1 in TA, and ± 5 µmol kg-1 in TCO2. These results will be combined with NOAA's AOML and PMEL groups to characterize the CO2 system in this region.

  85. Millero, F.J., J.-Z. Zhang, E. Peltola, M. Roche, S. Olivella, M. De Alessi, and B. Vargas. Total alkalinity measurements in the South Pacific. University of Miami Technical Report, RSMAS-94-003, 207 pp., 1994

    Abstract:

    In spring 1994, we participated in one CO2 cruise in the South Pacific during the Joint Global Ocean Flux Study (JGOFS) sponsored by the National Oceanic and Atmospheric Administration (NOAA). This report gives the results of our pH, total alkalinity (TA), and total inorganic carbon dioxide (TCO2) measurements made in the South Pacific during the cruise. The results were obtained by a potentiometric titration of seawater samples with HCl. Measurements on 116 samples of Certified Reference Material with the three cells at sea indicate that the systems have a reproducibility of ± 3.3 µmol kg-1 in TA. The resulting pH, TA, and TCO2 are thought to be precise to ± 0.01 in pH, ± 3 µmol/kg in TA, and ± 3 µmol/kg in TCO2. Our titration results will be combined with the NOAA measurements of TCO2 and fCO2 to characterize the CO2 system in this region.

  86. Zhang, J.-Z., and F.J. Millero. Investigation of metal sulfide complexes in seawater using cathodic stripping square wave voltammetry. Analytica Chimica Acta, 284(3):497-504, doi:10.1016/0003-2670(94)85056-9 1994

    Abstract:

    Cathodic stripping square wave voltammetry has been used to detect H2S in seawater over a wide range of concentrations (nM tomM). The addition of metal ions to the solutions was found to depress the signal. This depression was attributed to the formation of metal sulfide complexes [MHS+, M(HS)2]. Stability constants for the formation of sulfide complexes with Cd2+,Cu2+, Cu+, Pb2+, Co2+, Fe2+, Mn2+, Ni2+, and Hg2+ have been estimated in seawater at pH 8.0 and 25°C using this method. The stability constants of cadmium sulfide complexes (log βCdHS = 6.3 and log βCd(HS)2 = 12.7) were found to be in reasonable agreement with previous measurements. The values of log βCuHS = Cu(HS)2 = 13.0; log βPb(HS) = 7.1 and log βPb(HS)2 = 13.5; log βZnHS = 6.0 and log βZn(HS)2 = 13.7; log βFeHS = log βCoHS = log βNiHS = 5.3 and log βMnHS = 6.7 were also obtained. Correction for the formation of strong chloro complexes for Hg2+ and Cu+ in seawater gave measured values close to the literature values. The results have been used to determine the speciation of HS- in surface seawater and of a number of metal ions in various anoxic basins.

  87. Zhang, J.-Z., and F.J. Millero. Kinetics of oxidation of hydrogen sulfide in natural waters. In Environmental Geochemistry of Sulfide Oxidation, C.N. Alpers and D.W. Blowes (eds.). American Chemical Society Symposium Series, Washington, DC, 550:393-409, doi:10.1021/bk-1994-0550.ch026 1993

    Abstract:

    Recently we have studied the oxidation of H2S with O2 in natural waters as a function of pH (4-10), temperature (278.15-338.15 K), and salinity (0-36). The major products formed from the oxidation of H2S were SO32-, S2O32-, and SO42-. A kinetic model was developed to predict the distribution of the reactants and products over a wide range of conditions. Dissolved and particulate metals have a significant effect on the rates of oxidation and the product formation. Field measurements made in the Black Sea, Framvaren Fjord, Chesapeake Bay, and Cariaco Trench are in reasonable agreement with the values predicted from laboratory studies at the same concentration of Fe2+.