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Trends of Nitrogen and Sulfur in U.S. Precipitation: Emissions and Environmental Impact

This study examines the trends of nitrogen and sulfur in U.S. precipitation from 1985 to 2004, focusing on the roles of combustion-related and agricultural emissions. It utilizes data from 159 National Atmospheric Deposition Program sites, analyzing seasonal sulfate, nitrate, and ammonium concentrations. The findings indicate significant decreases in sulfate concentrations and SO2 emissions, highlighting important environmental improvements. By utilizing trend tests and evaluating emission sources, this research underscores the impact of policy and practice on atmospheric deposition.

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Trends of Nitrogen and Sulfur in U.S. Precipitation: Emissions and Environmental Impact

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  1. Trends of Nitrogen and Sulfur in U.S. Precipitationthe roles of combustion-related and agricultural emissions Van Bowersox & Chris Lehmann

  2. ` 2002-39138-11964

  3. NTN Sites – June 2006

  4. NTN Sites – June 2006 159 sites : 1985 – 2004 trends 255 sites + 3 “precision” sites

  5. Sulfate Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  6. Sulfate Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  7. Evaluating Trends(See: Lehmann, Bowersox, & Larson. 2005.Environmental Pollution. 135: 347-361.) • Precipitation-weighted-mean (high-V class & low-V class) seasonal concentrations • Seasonal Kendall Trend Test • Null Hypotheses: • Trend is zero (no trend) • Trends are homogeneous (same in every season) • Significance Level • p ≤ 0.1 for trend significance • p > 0.1 for homogeneity • Trend magnitude by Sen's Median Estimator

  8. NADP/NTN Sulfate Trend 1985-2004 NADP/NTN Sulfate Trend 1985-2004 The National Trend -46% (median change) The National Trend -46% (median change)

  9. Total Emissions Measured // Modeled 1985-2004 SO2emissions SO2 emissions trend(p < .001) ▼38%44%52%▼ SO4 concentration trends ▼43%46%48%▼ Ag emissions of SO2< 0.5% of total Source: U.S. EPA

  10. Nitrate Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  11. Nitrate Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  12. NADP/NTN Nitrate Trend 1985-2004 The National Trend -3% (median change)

  13. Total Emissions Measured // Modeled NO2 emissions trend(p < .001) ▼12%20%27%▼ NO3 concentration trends ▼6%3%1%▲ Ag emissions of NO2< 3% of total Source: U.S. EPA

  14. NOx Emissions Changes 1990-2000

  15. ??? 2000 - 1990 Emissions Differences • mismatch in time periods • undocumented emissions increases • changes in species scavenged (NH4NO3) 1985 to 2004 Trend Estimates

  16. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  17. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  18. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  19. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  20. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  21. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  22. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  23. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  24. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  25. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  26. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  27. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  28. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  29. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  30. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  31. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  32. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  33. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  34. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  35. NADP/NTN Ammonium Concentrations 1985 - 2003 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 National Atmospheric Deposition Program/National Trends Network

  36. NADP/NTN Ammonium Trend 1985-2004 Ammonium Trend, 1985-2004 The National Trend + 30% (median change)

  37. CMU w/ soils  CMU w/o soils  EPA method change Total Emissions Measured // Modeled Source: U.S. EPA

  38. CMU-model Ammonia-N Emissions 2002 (includes soil emissions)

  39. Ammonium/Sulfate Ratio, 1984-1986

  40. Ammonium/Sulfate Ratio, 2002-2004

  41. Ammonium/Sulfate Ratio, 2002-2004

  42. Sulfur // Nitrogen Chemistry: SO4/NH4/NH3/NO3/HNO3 • Inorganic SO4 has low volatility & reacts readily with NH3 to form stable salts compoundNH4/SO4 (NH4)2SO4 1.00 (NH4)3H(SO4)2 0.75 (NH4)HSO4 0.50 H2SO4 0.00 • Ammonia-rich environment: NH4/SO4>1.00 (Seinfeld, Saxena, Tanner, etal.)

  43. Sulfur // Nitrogen Chemistry: SO4/NH4/NH3/NO3/HNO3 • NH4/NH3/NO3/HNO3 : distribution between aerosol (NH4NO3)& gas (NH3 & HNO3) phases depends on T, TD, PHNO3, PNH3 • Effects: • scavenging ratios • wet deposition // dry deposition • transport distances // atmospheric lifetimes • visibility

  44. Based on a 20-year data record (1985-2004) at 159 NADP sites: • Significant trends of sulfur and nitrogen in U.S. precipitation. • SO4 decreased at ~97% (89% sig) of sites. Decreases ~ consistent with emissions • NH4 increased at ~90% (58% sig) of sites. NO3 decreased in NE and increased in MW & W. Need emissions and AQ data to evaluate S/R relationships. • Trends have resulted in increasingly ammonia-rich precipitation from which we infer a change in the particle // gas relationships of NH4, SO4, NO3, NH3, and HNO3

  45. The NADP provides long-term high-quality data for studying chemical climate.

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