monitoring chemical climate change in america the case for ammonia v. bowersox, c. lehmann, b....
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Monitoring Monitoring Chemical Climate ChangeChemical Climate Change
in Americain America
The Case for Ammonia
V. Bowersox, C. Lehmann, B. LarsonAcknowledge – R. Claybrooke
NADP Program Office
Air and Rain– the Beginnings of a Chemical Climatology
by Robert Angus Smith (1872)
“When the sulphuric acid increases more rapidly than the ammonia, the rain becomes acidic.”
Ammonia/Ammonium TrendsAmmonia/Ammonium Trends
Methods:Methods:
trends period: 1985 through 2002
applied Seasonal Kendall Trend Test meteorological seasons (Dec-Feb, etc.) applied four NADP data completeness criteria to accept/reject a season & a site
calculated Sen’s Estimator to quantify trends
Ammonia/Ammonium TrendsAmmonia/Ammonium Trends
Results:Results:
139 sites met completeness criteria for the 18-year trends period
Ammonium Increasing• 124 (89.2%) sites• 58 (41.7%) significant (p<0.05)
Ammonium Decreasing• 15 (10.8%) sites• 2 (1.4%) significant
Sulfate, Nitrate & Ammonium TrendsSulfate, Nitrate & Ammonium Trends
Results:Results:
Up Sig | Down SigSulfate 7 0 | 132 106Ammonium 124 58 | 15 2Nitrate 70 23 | 69 17
Chemical Climate: Chemical Climate: SO4/NH4/NH3/NO3/HNO3
Inorganic SO4 has low volatility & reacts readily with NH3 to form stable salts
• (NH4)2SO4 : NH4/SO4 = 1.00• (NH4)3H(SO4)2 : NH4/SO4 = 0.75• (NH4)HSO4 : NH4/SO4 = 0.50• H2SO4 : NH4/SO4 = 0.00
Ammonia-rich environment: NH4/SO4>1.00 (Seinfeld, Saxena,Tanner,etal.)
Chemical Climate: Chemical Climate: SO4/NH4/NH3/NO3/HNO3
NH4/NH3/NO3/HNO3 : distribution between aerosol & gas phases depends on SO4, T, TD, PHNO3, PNH3
Ammonia-excess: NH4-[(SO4+NO3+Cl) - (base cations)] > 0 (Blanchard, etal., 2000, JAWMA)
NH4 increased at ~90% (42% significant) of sites & SO4 decreased at ~95% (76% significant) of sites between 1985 and 2002.
Monitoring Monitoring Chemical Climate ChangeChemical Climate Change
in Americain AmericaThe Case for Ammonia
These trends, accompanied by locally significant changes in NO3, have increased the ammonia-excess, altering the SO4/NH4/NH3/NO3/HNO3
chemistry in air and precipitation in the United States.
Monitoring Monitoring Chemical Climate ChangeChemical Climate Change
in Americain AmericaThe Case for Ammonia
The NADP provides a long-term high-quality database for studying our chemical climate.