Chemical composition of bulk precipitation in the North-Central and Northeastern United States, December 1980 through February 1981

Abstract

Samples of bulk precipitation were collected at 179 sites in the North-Central and Northeastern United States for 3 months during winter 1980-81 to provide data on the distribution of chemical constituents. Concentrations and average daily loads of 29 dissolved constituents were determined. Sodium and chloride deposition was relatively high in coastal areas and adjacent to some urban centers. Regional patterns of to daily loads of hydrogen ion, nitrate, lead, and iron correlate well with one another and form a concentric pattern around the center of high deposition in eastern Ohio and western Pennsylvania, suggesting an urban-industrial source. Samples from this area had low pH (<4.2), whereas samples from southern Minnesota and Illinois had a more neutral pH (>5.7). The latter samples had high concentrations of calcium and total inorganic carbon, suggesting pH control by soil-derived carbonate minerals. Deposition patterns of ammonium, nitrate, and sulfate display regional highs in Illinois, Indiana, and southwestern Michigan, suggesting agricultural sources such as fertilizer. Median loads of zinc, iron, and lead were lower than reported in previous studies for North America. The apparent decrease in lead since 1950 throughout the area is attributed to reduced consumption of leaded fuels and lower deposition in winter.