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ACID RAIN MODELING
Citation:
Holland, D M. ACID RAIN MODELING. Encyclopedia of Environmetrics. John Wiley & Sons, Ltd., Chichester, Uk, (2001).
Impact/Purpose:
Our main objective is to assess the exposure of selected ecosystems to specific atmospheric stressors. More precisely, we will analyze and interpret environmental quality (primarily atmospheric) data to document observable changes in environmental stressors that may be associated with legislatively-mandated emissions reductions.
Description:
This paper provides an overview of existing statistical methodologies for the estimation of site-specific and regional trends in wet deposition. The interaction of atmospheric processes and emissions tend to produce wet deposition data patterns that show large spatial and temporal variability. We conclude that a number of approaches are useful for trend estimation, but no one method is appropriate for all purposes.
Tile reliable estimation of temporal trends in acidic deposition is an important concern to environmental managers for evaluating the effectiveness of legislated emission control Programs, Acidic compounds are formed in the atmosphere by the oxidation of sulfur dioxide and nitrogen oxides emitted to the atmosphere from both natural and anthropogenic sources- Acidic compounds and their precursors can reside in the atmosphere for many days and undergo long-range transport bcfore returning to earth in precipitation. Acid deposition compounds in the atmosphere have deleterious effects on both visibility and natural ecosystems.
Since the beginning of the 1980's, S02 emissions have been decreasing in both Europe and North America. Although a net decrease between 1980 and 1997 could be found in both regions, the magnitude and form of the decreases are quite different. It has been estimated that S02 emissions in Europe have been decreasing steadily since 1980 (Mylona, 1999) with the 1997 estimated emissions representing about 45% of the 1980 level. In the U.S., S02 emissions remained constant during most of the 1980's except for a net decrease in the beginning of the decade. Emissions decreased during to beginning of the 1990's reaching a minimum in 1995 (representing about 70% of the 1980 emissions based on Lynch et at, 2000). The sudden emission reduction observed in 1994-1995 is believed to be the consequence of the implementation of Phase I of the Acid Rain Program established bv Title IX of the 1990 Amendments to the Clean Air Act in the United States.
To determine whether emission reductions have had the intended effect of reducing wet deposition, measurement data can be statistically modeled to reveal the magnitude and spatial distribution of reductions in wet deposition. Previous studies show that the estimation of emission-related trend requires statistical techniques that account for the sources of variability underlying the wet deposition such as seasonal changes and precipitation amounts. Certainly these effects can vary from site to site, As environmental decisions are Often based on the results of trend analyses, achieving the most accurate and precise site-specific and regional trend estimates in the shortest possible