Grantee Research Project Results

2001 Progress Report: Regional scale impacts of Phases I and II of the Clean Air Act Amendments of 1990: The relationship between changes in emissions of SO2 and NOx, and wet and dry deposition of hydrogen ion, and sulfur and nitrogen compounds

EPA Grant Number: R826760
Title: Regional scale impacts of Phases I and II of the Clean Air Act Amendments of 1990: The relationship between changes in emissions of SO2 and NOx, and wet and dry deposition of hydrogen ion, and sulfur and nitrogen compounds
Investigators: Likens, Gene E. , Butler, Thomas J.
Institution: Cary Institute of Ecosystem Studies
EPA Project Officer: Chung, Serena
Project Period: September 21, 1998 through September 20, 2001
Project Period Covered by this Report: September 21, 2000 through September 20, 2001
Project Amount: $172,860
RFA: Regional Scale Analysis and Assessment (1998) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration

Objective:

The objective of this project is to assess the impact of the Clean Air Act Amendments (CAAA) of 1990 on precipitation and air chemistry for the eastern United States.

Progress Summary:

A comparison of data records in the 1990s, both before (1991-94) and after (1995-97) implementation of Phase I of the CAAA of 1990 for seven regions of the eastern United States, shows a significant reduction in SO2 emissions for most states, except for Texas, North Carolina, Illinois, Florida, and Alabama. However, of the major NOX-emitting states, only two eastern states (New York and Pennsylvania) show significant declines in NOX.

A pattern of large declines in SO2 emissions (>20%) after CAAA implementation and large declines in precipitation SO4^2- and H+, as well as air concentrations of SO2 and SO4^2- (components of dry deposition), exists for most regions of the eastern United States. The regions examined include: Northern New England and the Adirondack Mountains (NE); New York, excluding the Adirondack Mountains (NY); Pennsylvania, northern West Virginia, and eastern Ohio (PA); Delaware, Maryland, and eastern Virginia (M-A); Ohio, eastern Indiana, and northern Kentucky (OH); Illinois and western Indiana (IL); and the southern Appalachian Mountains and surrounding area (SA).

In most cases, the emission/concentration relations are close to 1:1 (a near equal percent decline in concentrations for a given percent decline in emissions) when the source region based on 15-hour air mass back trajectories is used for the NE region, and source regions based on 9-hour back trajectories are used for the other eastern regions. The SA region, an acid-sensitive area receiving high levels of acidic deposition, has not seen an appreciable improvement in precipitation acidity. Of the areas examined, this area also has seen the least improvement in wet and dry sulfur concentrations (see Table 1 and Butler et al., 2001).

Base cations (Ca⁺⁺ and Mg⁺⁺) in precipitation show a pattern of increasing or level concentrations when comparing 1990-94 and 1995-98 data for six of the seven regions examined. Ammonium concentrations generally have changed <10 percent, except for the IL and SA region, which increased >15 percent.

While Phase I of the 1990 CAAA has continued the reduction in SO2 emissions and precipitation concentrations of SO4^2- , long-term records from the Hubbard Brook Experimental Forest indicate that decreases in precipitation SO4^2- since 1990 are neither unusual nor large relative to the long-term trend beginning in 1964 (Likens et al., 2001). Moreover, these changes have not translated into significant decreases in acidification for many sensitive ecosystems (Driscoll et al., 2001). The long-term (1964-97) declines in precipitation SO4^2- concentration at the Hubbard Brook Experimental Forest and SO2 emissions based on 15-hour air mass back trajectories are strongly related (R² = 0.74).

Table 1:
Changes in emissions (a, b, and c), precipitation concentrations (d and f), and air concentrations (e) for several regions of the eastern United States between 1991-94 and 1995-97.

Future Activities:

Future efforts will focus on: (1) establishing the relation between NOx emissions and their impacts on precipitation NO3- (a major source of acid deposition); and (2) how implementation of Phase II may translate to improvements in surface water quality.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views

Other project views:	All 7 publications	3 publications in selected types	All 3 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Butler TJ, Likens GE, Stunder BJB. Regional-scale impacts of Phase I of the Clean Air Act Amendments in the USA:the relation between emissions and concentrations, both wet and dry. Atmospheric Environment 2001;35(6):1015-1028.	R826760 (2001) R826760 (Final)	Full-text: Science Direct Exit Abstract: Science Direct Exit Other: Science Direct PDF Exit
Journal Article	Likens GE, Butler TJ, Buso DC. Long-and short-term changes in sulfate deposition: effects of the 1990 Clean Air Act Amendments. Biogeochemistry 2001;52(1):1-11.	R826760 (2000) R826760 (2001) R826760 (Final)	Abstract: SpringerLink Exit

Supplemental Keywords:

acid rain, acidic deposition., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Water, Restoration, Ecological Indicators, Ecological Risk Assessment, Ecosystem Protection, Aquatic Ecosystem Restoration, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecological Effects - Environmental Exposure & Risk, Nutrients, Ecology and Ecosystems, Environmental Monitoring, bioavailability, precipitation, regional economies, ecological impact, Clean Air Act, emissions, hydrogen ion, climatology, nutrient stress, water quality, ecosystem, precipitation chemistry, aquatic ecosystem, nutrient sensitive ecosystems, wet and dry deposition, monitoring, nitrogen compounds, atmospheric nitrogen deposits, sulfur, SO2, public policy, sulfur compounds, ecosystem stress, hydrological stability, nitrogen oxide, ecological exposure, dry deposition, chemical transport, rainfall, nitrogen, regulations, acid rain

Progress and Final Reports:

Original Abstract

1999 Progress Report

2000 Progress Report

Final Report