Acid deposition and acidification of soil and water in the Tie Shan Ping area, Chongqing, China

Chongqing is among the heaviest polluted cities in China- Combustion of coa l with relatively high sulfur content causes high sulfur emission and depos ition in the area. Effects on soils and waters of the acid deposition in th e Chongqing area have been studied in the field at a forested site outside the city. Deposition chemistry and fluxes, soil and soil water chemistry as well as surface water chemistry are presented for the period 1996-1998. Th ere are some stress symptoms at the forest in the area and severe forest da mage has been reported at Nanshan, closer to Chongqing center. Monitoring o f the acidification situation in the area must be followed closely as impac ts may be expected if the deposition is not reduced in the future. The deposition of sulfur, H+ as well as calcium at the site is high. Wet de position of sulfur is estimated to 4.7 - 5.7 g S m(-2) yr(-1) during the th ree years sampled; dry deposition is probably of similar size. Annual volum e-weighted pH in bulk deposition was 4.0 - 4.2 and the calcium wet depositi on flux was 2.6 - 3.6 g Ca2+ m(2). There are considerable seasonal variatio ns in the concentrations, related to the seasonal variations in precipitati on amount (dry winter, wet summer). The soils at the site are acid with med ian base saturation of 12% and 8% in the topsoil and subsoil, respectively. In soil water, aluminum concentrations are typically in the range 3-8 mg L -1. However, due to the high base cation deposition, the Al/(Ca2++Mg2+) mol ar ratio is below unity in most samples, indicating little damage of forest due to aluminum in soil water.