摘要：The relaxed eddy accumulation (REA) method was utilized to
measure fluxes of key atmospheric species, specifically ammonia
(NH3), nitric acid
(HNO3), sulfur
dioxide (SO2) and
particulate sulfate (SO42−) to vegetation that is characteristic throughout the Tampa Bay Watershed. Three annular
denuder systems (ADS), each consisting of two annular denuders and a filter pack in series,
were deployed to accumulate gaseous constituents and fine-fraction particulates
(Dp<2.5 µm) in updraft and downdraft eddies, as well as in the mid-draft velocity range. Relaxed eddy
accumulation samples, which were analyzed by ion chromatography, and continuous meteorological
data were collected during the May 2002 Bay Regional Atmospheric Chemistry Experiment
(BRACE) near Sydney, FL. For the chemical species of current interest, concentrations were
1.64 ± 0.23 for NH3, 2.06 ± 0.24 for HNO3, 3.49 ± 0.50 for
SO2 and
4.64 ± 0.31 µg m−3 for
SO42−, and the deposition
velocity (Vd)
estimates for NH3, HNO3, SO2 and SO42− were 1.27 ± 3.65, 3.63 ± 1.47, 0.45 ± 0.98 and 0.42 ± 1.00 cm s−1, respectively. The results obtained confirm the expectation that the deposition of
ammonia, nitric acid and particulate sulfate was controlled by aerodynamic and
quasi-laminar layer resistances and that sulfur dioxide is relatively dependent upon
stomatal conditions.
