The Blind Pass Petroleum in Sediments Project
The Blind Pass Petroleum in Sediments (BPPES) program is designed to map the location of petroleum-based sediments in and around of Blind Pass (near Tampa), Florida.
In 1993 a collision of tanker barges resulted in the discharge of approximately 330,000 gallons of #6 fuel oil from the Bouchard #155 and of about 32,000 gallons of Jet A, diesel and gasoline oil into lower Tampa Bay. Winds and currents carried most of the oil into open waters of the Gulf of Mexico in the first few days after the spill; however, oil residue came ashore on August 14 and 15 on a strong storm front, and was deposited on the sandy beaches of the barrier island communities and moved through inlets into Boca Ciega Bay. The incident resulted in oiling of birds, sea turtles, mangroves, salt marshes, sea grasses, mud flats, oyster beds, and seawalls in finger canals within Boca Ciega Bay and miles of shoreline, including sandy recreational beaches. Some of the fuel oil sank, forming mats on submerged sediments in offshore depressions, in passes such as Blind Pass, and in Boca Ciega Bay (Urquhart-Donnelly, 2000).
In late 1999, the U.S. Army Corps of Engineers and Pinellas County conducted geotechnical borings in those passes to determine the sand quality and identify any areas of unsuitable material for beach renewal. With minimal indication of the presence of residual oil, dredging activities in Blind Pass began in January 2000. During these activities, small pockets of petroleum hydrocarbon, approximately 50 gallons each, were discovered. T he U.S. Coast Guard initiated oil containment and cleanup of this oil after cessation of dredging activities. The oil recovered was #6 fuel oil, the same type as spilled in 1993.
The dredging project was put on standby while additional borings be performed at Blind Pass; these produced a more detailed map of where residual oil pockets were located. An Assessment Team recommended continuation of the dredging project in Blind Pass as the best method for removal of the submerged oil. Dredging operations resumed on February 2, 2000 and approximately 20,000 gallons of oil/water were recovered. The condition of this submerged oil after almost seven years in the natural environment is technically noteworthy. When found, the oil was still fairly fluid, producing sheens and releasing volatile or aromatic fractions. Substantial degradation due to aerobic or anaerobic processes was not evident (Urquhart-Donnelly, 2000)
The present work was conducted in anticipation of future Blind Pass dredging operations. As part of this effort, sediment cores were collected by the University of South Florida (USF) and analyzed by AOML and RSMAS. At AOML, the samples were analyzed using a new instrument, the fuel fluorescence detector (FFD). In conjunction with those analyses, petroleum hydrocarbon characterization and calibration using GC/FID and GC/MS were conducted under the direction of the University of Miami Rosensteil School of Marine and Atmospheric Sciences (RSMAS).
The objectives of the investigation were to determine (1) the utility of the FFD probe in assessing petroleum hydrocarbons in coastal marine environments, (2) characterization of intra-core petroleum hydrocarbon levels in sediment, and (3) depiction of the spatial distribution and individual hydrocarbon speciation of these petroleum hydrocarbons within Blind Pass.
In the study, one hundred and one sediment cores were collected to characterize the spatial distribution of petroleum hydrocarbons within and just outside the pass. Twenty five percent of the cores exhibited levels of petroleum hydrocarbons above detection limits of the GC/FID (0.01 mg/Kg), but at generally low concentrations. Petroleum hydrocarbon speciation studies (GC/MS) of these samples indicate above detection level (1ug/Kg) petroleum hydrocarbons are similar to the non-volatile petroleum hydrocarbons found in a Bouchard #155 reference sample, collected after the 1993 oil spill in the area, but are in a much degraded and weathered state. Individual petroleum hydrocarbons were, in all but one case, below the Threshold Effective Level (TEL) described in the literature (McDonald, 1994). The petroleum hydrocarbons were primarily found at 100-300cm depth in Blind Pass cores. Above detection level petroleum hydrocarbons were generally found in samples from cores found in the center of the Channel, near the edges of the Shoal and just Outside the Pass.
A second mixture of hydrocarbons, primarily phthalates, ketones and ether were found at relatively shallow core depths (0-99cm) in the Mid and North End Channel cores. These suggest a separate source of contamination, possibly storm water runoff. The Fuel Fluorescence (FFD) probe was investigated for its applicability to detect petroleum hydrocarbons in marine sediments. When analyzed with the FFD, all sediments from the cores produced peaks of fluorescence, but none above background levels of Blind Pass native sediments. All but two samples analyzed by GC/FID were below the detection limits (100 ppm) of the FFD. These samples were found in dark-colored sediments. The combination of the detection limit of the instrument, sediment color, and the degraded nature of the heavier weight petroleum hydrocarbons may have resulted in fluorescence outputs below background levels. These studies demonstrate that the distribution of petroleum hydrocarbons within Blind Pass sediments is generally low and patchy. However, 25% of the cores exhibited levels above detection using GC/FID/MS, and could be subjected to individual speciation studies which indicated generally below TEL levels, and an association of some, but not all, with the 1993 oil spill in Blind Pass.
Summary and Conclusions
Twenty two of the 101 sediment cores collected in Blind Pass contained horizons with low, but above detection levels (0.01mg/Kg) of C8-C40 total petroleum hydrocarbons using the Florida DEP FL-PRO methodology and GC/FID.
Detected concentrations of petroleum hydrocarbons were generally found at the 100-300 cm depths in Blind Pass cores.
Although petroleum hydrocarbon concentrations were not regionally localized, they were noted in the center of the Channel, around the edges of the Shoal area and Outside the Pass.
Blind Pass GC/MS petroleum hydrocarbon speciation analyses indicated above detection (>1ug/Kg) of non-volatile individual hydrocarbons which were similar to those found in the Bouchard #155 reference sample. Common hydrocarbon species include acenaphthene, fluorene, anthracene, acenaphthlene, chyrsene, pyrene, benzo(a)pyrene, benzo(b)fluoranthene, fluoranthene and phenanthrene.
Several sediment cores located at the North end of the channel and within the Mid channel contained phthalates, ketones and ether. These may be from a source of hydrocarbon contamination distinct from the 1993 oil spill, possibly storm water runoff. Most of these were found in the upper 99cm depth of the sediment cores.
The FFD probe detected peaks of fluorescence in all the sediment cores, but none were above background levels of the native sediments found in Blind Pass. All petroleum hydrocarbon concentrations were below detection limits (100 mg/Kg) of the FFD, with the exception of two samples with concentrations of 110.0 mg/Kg and 346.0 mg/Kg. In addition to these samples being at or just above detection limits of the FFD, they were present in dark colored sediments which affect the fluorescence peaks of the FFD. These results indicate the samples may have been below detection levels for FFD analyses.
FFD responded well when fresh oil was mixed in Blind Pass sediment and analyzed. However, it showed little response to a sample of degraded oil from the Exxon Valdez spill. FFD may not be sensitive enough to detect areas of petroleum hydrocarbon contamination when the hydrocarbons have been significantly degraded as is the case in Blind Pass.
Spatial Distribution of Petroleum Hydrocarbons in Blind Pass Sediment Cores. Charles Featherstone, John R. Proni, Thomas P. Carsey, Madeleine Adler, Cheryl Brown Patricia L. Blackwelder, Husain Alsayegh, Terri Hood, Christina Piela Donald S. McCorquodale. NOAA Report 2009 (pdf).
Scientists and Support Staff
John Proni (Applied Research Center, Florida International University, Miami, Florida),
P. Blackwelder (Rosenstiel School of Marine and Atmospheric Sciences, University of Miami)
P. Wang, (University of South Florida)
The Blind Pass Program is another environmental program from the Ocean Chemistry Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory.