Continental-scale variations in precipitation chemistry

Available data on precipitation chemistry in North America have been assembled and used to generate isopleth maps of ion concentrations in precipitation. Despite some deficiencies in the data and problems with combining data from different sources, the resultant isopleths can be used to identify regional patterns of major ions in North American precipitation. The information on trace-metal concentrations is less complete. The major conclusion of the peper is that precipitation chemistry is dominated by local and regional land use patterns and proximity of anthropogenic emissions. Acidity is highest in precipitation where emissions of precursor anthropogenic gases are highest and the concentrations of neutralizing soil components are the lowest. (JMT)