Abstract |
Average precipitation pH, 1979-1982, declines from west to east from 5.3 to 4.3 along a cross section of sites in Minnesota, Wisconsin, and Michigan. The answers questions about the seasonal and geographic pattern of anthropogenic acid precursor emissions and reaction products (SO4(2), NO3(-), H(+), NH4(+)) that increase from west to east. Except for higher concentrations of Ca(2+) and Mg(2+) observed at one site in the cultivated area of southwestern Minnesota, the contribution of soil-related metal cations to the total ions in solution is small (17%) and relatively uniform across the region. Significant seasonal and geographic patterns in precipitation chemistry and deposition values are observed. Close correspondence of the sums of strong acid anions with the sums of hydrogen and ammonium ions in precipitation is observed, indicating anthropogenic sources of sulfur and nitrogen oxides. (Copyright (c) 1985 American Chemical Society.) |