A Model Study of Soil Acidification in A SMall Catchment near Guiyang, Aouthwestern China

摘要

Soil acidification has been reported in southewstern china and may become a serious problem in large areas. In order to understand the effect of acid deposition on soild in this region, detailed studies of deposition ,throughfall, soils, soil waters and streamwater have bee ncarried out in a small ctchmetn near Guiyang Since 1992. in the present paper, the MAGIC model with two soil reservoirs was selected to investigate longterm changes in siils and soil waters due to acid deposition for four different plots in the catchment, and to estimate likely responses to assumed future depositio nscenarios. Data from the previous field an laboratory studies ware used as far as possible to determine model parameters and to check results. The model simulations indicate that long-term acid deposition has resulted in soil acidificatio nin the catchment, especially in the upper horizons. However, partly due to different topography and vegetation ,soil parametersary substantially resulting in large variations in sensitivity to acidifiction even within this small catchment. The model outputs depend heavily on values chosen for dry deposition factors for major ions, the solubility constant ofr AL(OH) sub 3, weathering rates of soil minerals, and to some extent on soil cation exchange capacity, sulfate absorption capacity, and ion concentrations in deposition in the background year. The model results predict that soil acidification well accelerate if deposition of basic metal cations decreases or deposition of SO sub 4 increases by 30