Calculating of Critical Loads of Sulfur Deposition for Surface Waters in Southern China Using a Steady-state Acidification Model
应用稳态模型计算中国南方地表水的硫沉降临界负荷

In order to study the response of Chinese surface waters to acid deposition, a steady state model based on acidity balance was applied in this paper to calculate critical loads of sulphur deposition for surface waters in southern China. An empirical equation for Chinese surface waters was obtained to calculate the background sulfate concentration. The results showed that the critical loads of sulphur deposition for most surface waters in southern China were more than 2.0 keq·(hm2·a)-1, indicating that they were not sensitive to acidification. Surface waters with critical loads less than 2.0 keq·(hm2·a)-1 were those waters located on mountains. Except these mountain waters, the critical loads of sulphur depositionf for other surface waters were not exceeded by the present sulphur deposition, indicating acidification will not occur in the near future for these waters. The spatial distribution of critical load exceedance was similar with that of the critical loads, showing the trend of increasing from the southeastern provinces, such as Fujian, Guangdong and Jiangxi, to the southwestern and the central region. The uncertainty analysis of the model results indicated that, the errors of the results caused by the uncertainty of parameters and the input data were minor and acceptable so long as the input data were among the appropriate ranges.