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County-scale annual ammonia emissions are estimated in eight Southeast States for the
year 1997 using emission factors and activity data for all domestic livestock and fertilizer sources.
A geographical distribution of the data yields local areas (350-1500 km2) of elevated ammonia
(NH3) emissions (>2000 kg NH3/km2). Temporal and spatial variation in ambient ammonium
(NH4
+) concentrations and volume-weighted NH4
+ concentration in precipitation are investigated
over the period 1990-1998 in and around these source regions. Regression analysis for the year
1997 shows that annual average ambient NH4
+ concentration increases logarithmically (R2=0.86)
with the total annual NH3 emission within the corresponding county. It is also shown that annual
volume-weighted average NH4
+ concentration in precipitation increases linearly with annual NH3
emission within the corresponding county when precipitation effects are accounted for. Analysis of
ambient NH4
+ concentration at various Clean Air Status and Trends Network (CASTNet) sites
revealed that temperature, precipitation amount, and relative humidity are the most statistically
significant (p<0.05) parameters in predicting the weekly concentrations of NH4
+ during the period
1990-1998. Wind speed and wind direction were also statistically significant (p<0.05) at several
CASTNet sites, but the results were less consistent. Investigation into wet NH4
+ concentration in
precipitation yielded temperature as a statistically significant (p<0.05) parameter. Trends over the
period 1990-1998 revealed a slight decrease in ambient NH4
+ concentration at CASTNet site SPD
(2.14 to 1.88 mg/m3), while positive trends in NH4
+ concentration in precipitation were evident at
NADP sites NC35 (0.2 to 0.48 mg/L) and KY35 (0.2 to 0.35 mg/L ) over the period 1990-1998.
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CNumber:
International Symposium on the Measurement of Toxic and Related Air Pollutants: 09/12/2000
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Publication Type:
Proceedings
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Publication Date:
September 2000
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