Statistical Analysis of Precipitation Chemistry Measurements over the Eastern United States. Part I: Seasonal and Regional Patterns and Correlations

This paper describes the behavior of the chemical constituents in precipitation, including their typical concentrations and ranges, regional patterns, and seasonal changes. Daily precipitation measurements for the period 1978 through 1983 over the eastern United States were examined for 34 sites. The sites were operated by the Electric Power Research Institute and Utility Acid Precipitation Study Program (known as EPRI-UAPSP), the Multistate Atmospheric Power Production Pollution Study (MAP3S), and the Wisconsin Acid Deposition Monitoring Program (WADMP). Data from these three networks were combined into a single, uniform archive of daily rainfall records containing precipitation amounts, pH, and constituent concentrations. Various statistical analyses were made to determine the predominant characteristics of the data. In Part I of this series of papers, a seasonal analysis is made of the concentrations of hydrogen ion, sulfate, nitrate, and ammonium, and regional differences are described. Also, the statistical relationships of hydrogen ion concentrations to the other principal constituents are discussed. Other aspects of the study are given in Parts II through IV of the series. Part II uses an objective statistical interpolation method (Kriging) to evaluate the spatial patterns of constituents and their trends during the period of record. Part III discusses the ionic balance among the constituents, and Part IV describes the variations in concentrations that are attributable to meteorological factors.