monitoring chemical climate change in america the case for ammonia v. bowersox, c. lehmann, b....

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Monitoring Monitoring Chemical Climate Change Chemical Climate Change in America in America The Case for Ammonia V. Bowersox, C. Lehmann, B. Larson Acknowledge – R. Claybrooke NADP Program Office

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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.