ACID DEPOSITION AND LAKE CHEMISTRY IN SOUTHWEST CHINA

A water quality survey has been performed on selected lakes and stream s in southwest China. The purpose of the study was to measure the conc entrations of acidic deposition and surface water chemistry in a regio n of severe air pollution, forest decline, and relatively sensitive ge ology to acidic deposition. We show that, although there are some high elevation lakes of low acid neutralizing capacity (ANC < 150 mueq L-1 ), acidification of lakes has not occurred in southwest China due to p roduction of base cations in soil and dry deposition of dust that serv es to neutralize acidic deposition. Water chemistry is buffered by hig h base cation concentrations (Ca2+, Mg2+, Na+, and K+) greater than 30 0 mueq L-1, and pH values are always greater than 6.5.