Critical loads of acid deposition on soil in China

Critical loads of acid deposition have been mapped for Chinese soils using a modified semi-quantitative method, which is based on the minerals controlling weathering and soil development, and corrected by introducing an Arrhenius relationship to describe the effect of temperature and a weighted averaging approach to evaluate the effect of soil texture, land use and precipitation. As a consequence of these modifications, the method has been quantified and can be more widely used. Results from this study show that the lowest critical loads of acid deposition in China, i.e., those areas most sensitive to acid deposition, occur in the Podzolic soils in the Northeast, followed by Latosol, Dark brown forest soil and Black soil areas. The Ferralsol areas in South China are intermediate, tolerating about 0.8-1.6 g m(-2) yr(-1) sulfur deposition. The highest critical loads of acid deposition are mainly located in the Alpine soil areas on the Plateau of Tibet and areas of Xerosol and Podocal soil in Northwest China. The reason for lower critical loads in the Northeast relative to South China can be attributed to the difference of temperature, soil moisture and soil texture. Comparison of critical loads with the sulfur deposition in 1995 identifies almost one fourth of the land area in southeast China to be subject to risk of acidification.