[Estimating critical loads of sulfur and nitrogen for Chinese soils by steady state method]

Supported by the geographical information system (GIS), critical loads of sulfur and nitrogen of Chinese soils were estimated through the steady state method. Results showed that the lowest critical loads of sulfur [< 0.3 g.(m2.a)-1] occurred on the Daxingan Mountain, Xiaoxingan Mountain and Changbai Mountain in northeast China, the valley of the Yaluzangbu River on the south of the Tibetan Plateau, and the catchments of the Nu River and the Lancang River in the southwest of Yunan province. However, the critical loads of southeast China, where acid deposition was very high, were intermediate and in the range of 0.8-3.2 g.(m2.a)-1. According to the critical loads of sulfur, China might be divide into two parts approximately by the 400 mm isohyet-the northwest part could generally tolerate more than 3.2 g.(m2.a)-1 sulfur deposition, but the southeast one could not. Dislike the distribution of the critical loads of sulfur, the critical loads of nitrogen were low in the west China and high in the east. The lowest critical loads of nitrogen [< 1.0 g.(m2.a)-1] occurred on the west of the Tibetan Plateau and on the Alashan Plateau, and the highest [> 4.0 g.(m2.a)-1] on the Dongbei Plain, the Huabei Plain, the Changjiangzhongxiayou Plain, and the Sichuan Basin, etc.