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TRENDS IN RURAL SULFUR CONCENTRATIONS
Citation:
Holland, D M., P. Caragea, AND R. L. Smith. TRENDS IN RURAL SULFUR CONCENTRATIONS. Presented at International Conference on Environmental Statistics and Health, Santiago de Compostela, Spain, July 16-18, 2003.
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:
As the focus of environmental management has shifted toward regional- scale strategies, there is a growing need to develop statistical methodology for the estimation of regional trends in air pollution. This information is critical to assessing the effects of legislated emission control programs. This paper presents an analysis of trends in atmospheric concentrations of sulfur dioxide (SO2) and particulate sulfate (SO,'-) at rural monitoring sites in the Clean Air Act Status and Trends Monitoring Network (CASTNet) from 1990 to 1999. A two-stage approach is used to estimate regional trends and standard errors in the Midwest and Mid-Atlantic regions of the U.S. In the first stage, a linear regression model is used to estimate site-specific trends in data adjusted for the effects of season and meteorology. In the second stage, kriging methodology based on maximum likelihood estimation is used to estimate regional trends and standard errors. This method is extended to include a Bayesian analysis to allow more accurate determination of the prediction error variance that accounts for uncertainty in estimating the spatial covariance parameters. For both pollutants, significant improvement in air quality was detected that appears similar to the large drop in S02 power plant emissions. Spatial patterns of trends in S02 and SO,2- concentrations vary by location over the eastern United States. Both spatial prediction techniques produced similar results in terms of regional trends and standard errors.