LOW LEVEL MEASUREMENTS OF ATMOSPHERIC AMMONIA: A STUDY OF ITS
ROLE IN NEW PARTICLE FORMATION AND ITS IMPACT ON GLOBAL CLIMATE
Principal Investigator:
Dr. Pai-Yei Whung
Collaborating scientist(s):
Charlie Fischer
Objective:
To conduct real-time measurements of low level gaseous
ammonia in both clean marine and polluted environments in order to better
understand the
baseline aerosol chemistry for radiatively important aerosols and the
anthropogenic perburbation on aerosol chemistry and processes,
repectively. To ultilize this information to better define the role of
ammonia in new particle formation.
Rationale:
Sulfate containing aerosols are the major source of cloud
condensation nuclei (CCN) which have direct and indirect effects on
global climate. Recent results (Coffman and Hegg, 1995; Weber
et al., 1995) showed that atmospheric ammonia could play an important role in
the nucleation of new particles. The presence of ammonia can enhance the
nucleation rate and the production of new particles in the atmosphere.
These new particles can be activated to become condensation nuclei (CN)
and then, through various processes, grow to a size of 0.05 um or
larger to be effective as CCN. As mentioned before, CCN can affect the
global radiation budget. The magnitude of this effect is sensitive to
number density and size of the particle, so it is important to
understand the processes governing the chemical and physical properties
of aerosols. Since NH3 can be a key species involved in new particle
production, it is necessary to obtain information on the spatial
distribution of ammonia in the atmosphere.
Method:
To conduct low level atmospheric gaseous ammonia measurements, a
diffusion scrubber and HPLC/fluoresence-based technique was developed (Figure). The detection limit of this method is at
the low pptv level at a sampling rate of 15 minutes.
Accomplishment:
We have proven the new method in laboratory tests and will
field test the method in the Aerosol Characterization
Experiment 1 (ACE-1) Cape Grim platform in November, 1995. We hope to
demonstrate the importance of ammonia in baseline aerosol chemistry
during this field campaign. We have submitted a proposal to the NOAA
Climate and Global Change Program to be part of the ACE-2 expedition in
1997.
Key reference:
Whung, P.-Y., E.S. Saltzman, and C. Fischer (in prep.), Low level
measurements of atmospheric ammonia, draft is available upon request.
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