Comparison of precipitation chemistry data at a central Illinois site in 1954 and in 1977

In 1954 detailed precipitation chemistry measurements on samples from a manually operated wet-only collector provided data for the concentrations of the major ions for precipitation events. A comparison with data for the same location for 1977, collected with an automatic wet-only collector, showed that the median sulfate and nitrate concentrations were somewhat larger than in 1954 while the median calcium plus magnesium concentration was much lower. The precipitation event median pH was also much lower in 1977. Possible explanations for the present lower calcium plus magnesium concentrations and the correspondingly lower pH values are given.U. S. Department of Energy, Contract EY-1199Ope