Mapping critical loads of acid deposition for soils in China

A method described is to produce critical load maps of acid deposition for soils in China. Critical loads were assigned to the most sensitive soil in each 0.1° × 0.1° grid square of China based on the Skokloster classification
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and adjusted for temperature and land use. The map shows that soils with small critical load (< 0. 5 keq • ha-1 • a-I) i. e., highly sensitive to acid deposition, dominate in the south and northeast China. As a result of the adjustment, much of the acid sensitive area in the south estimated by the Skokloster method is lost. This reflects the decreased sensitivity as a result of agricultural activities and increased weathering rate in response to high temperature. Based on the 0. 1° × 0. 1° 0 map, a series of percentile critical load maps at 1° × 10 scale-were compiled for integrated assessments, as well as a critical load map using the minimum critical load for each grid. Comparison of critical loads with sulphur deposition in 1995 led to the critical load exceedance maps for sulphur deposition, which show that high exceedance areas do not correlate well with the low criiical load areas, and almost one fourth of the land area, mainly in the southeast, is subject to the risk of acidification.