Soil Vulnerability and Sensitivity to Acid Deposition in China

Sensitivity, in this context, refers to `the degree to which a system will respond to acid deposition', while vulnerability is `the extent to which acid deposition may damage or harm system'.Thus, sensitivity stresses the risk of an increase in the rateof change of the soil chemistry (the acidification rate), and vulnerability stresses the risk of damage to an organism or system (the acidification state). With regard to acid depositioneffects, both vulnerable and sensitive ecosystems are of concern;however, they are usually not well distinguished. The identification of ecosystems vulnerable (at risk for damage) or sensitive (high degree of response) to acid deposition is very important if policy makers are to derive cost-effective pollutioncontrol strategies. In this paper, the relative vulnerability andsensitivity of soils in China are assessed on the basis of soil base saturation and cation exchange capacity. Vulnerable and sensitive soils, as well as the risks associated with acid deposition, are identified. The characteristics of these two types of soils and their responses to acid deposition are discussed. Finally, results obtained by using different approaches are compared. The results show that the most vulnerable areas are located mainly in Guangdong, Guangxi, Guizhou, and Sichuan provinces andin the southern part of Yunnan province. On the other hand, themost sensitive areas are located mainly in Zhejiang, Jiangxi, Hunan, and Fujian provinces and in the northern part of Yunnanprovince. Combining the distribution of vulnerability and sensitivity with the sulfur deposition shows that the areas around Chongqing City and central Guizhou province are at highrisk for damage by acid deposition; central Zhejiang province andthe boundary region between Hunan and Jiangxi provinces would be at high risk for a high rate of acidification if acid depositionwere to increase.