THE RELATIONSHIP BETWEEN UPWIND SO2 EMISSIONS AND SO4(2-) CONCENTRATIONS IN PRECIPITATION AT 6 SITES IN THE EASTERN USA

A method for estimating the upwind SO2 emissions associated with individual wet SO42-deposition events has been developed. The relationship between these estimates and wet SO42- concentrations was examined at six Utility Acid Precipitation Study Program Sites (UAPSP) for the 1979-1986 period. Using Spearman correlation coefficients and the Bonferroni experimentwise criterion for statistical significance it was found that upwind emissions and concentrations were significantly related (p<0.05). However, correlation's were sensitive to site location, time upwind of the emissions and season, and ranged from -0.03 to 0.50. Correlations were weaker at sites located west of the high emission region in the midwestern U.S.A. and stronger at sites further away and to the east of this region. There was a decrease in the strength of the correlations from the warm season to the cold season. It was also found that differences in meteorology between events obscured the relationship between emissions and concentrations. The effects of variations in ambient temperature and precipitation amount on wet SO42- concentrations were taken into account by calculating partial correlation coefficients. A higher percentage of the resulting correlations were found to be statistically significant and the differences between sites decreased. This suggested that meteorological variability had a confounding influence on the detection of a link between concentrations and emissions. This influence should be considered when studying source-receptor relationships.