Monitoring long-term trends in sulfate and ammonium in US precipitation: Results from the national atmospheric deposition program/national trends network

Christopher M.B. Lehmann, Van C. Bowersox, Robert S. Larson, Susan M. Larson

Research output: Contribution to journalArticle

Abstract

Data from the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) indicate significant changes have occurred in precipitation chemistry and the chemical climate in the United States (US). A Seasonal Kendall Trend (SKT) analysis shows statistically significant increases in precipitation ammonium concentrations at 64% of 159 continental US NADP/NTN sites evaluated from Winter 1985 to Fall 2004 (Dec. 1984 - Nov. 2004). Sulfate decreases were widespread, with an SKT analysis indicating statistically significant decreases at 89% of sites evaluated. Ratios of chemical equivalent concentrations of ammonium to sulfate in precipitation have risen to the extent that ammonium now exceeds sulfate over more than half of the continental U.S. on a precipitation-weighted-mean annual basis. These trends in the concentrations of ammonium, sulfate, and other species have been accompanied by significant decreases in the frequency of acidic precipitation (pH∈<∈5.0) in the last decade.

Original languageEnglish (US)
Pages (from-to)59-66
Number of pages8
JournalWater, Air, and Soil Pollution: Focus
Volume7
Issue number1-3
DOIs
StatePublished - Mar 1 2007

Keywords

  • Chemical climate
  • Precipitation chemistry
  • Trend analysis

ASJC Scopus subject areas

  • Water Science and Technology
  • Pollution
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)

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