ASSESSMENT OF CRITICAL LOADS IN LIUZHOU, CHINA USING STATIC AND DYNAMIC-MODELS

The project Comprehensive Control and Demonstration for Acid Depositio n in Liuzhou area is a national key project in the 8th Five-year-plan, and the study on critical loads will provide scientific and quantitat ive accordance for formulating control strategy. In this paper, critic al loads of acid deposition to soil in Liuzhou area, China, were calcu lated using the Steady State Mass Balance method (SMB and PROFILE) and dynamic modeling methods(MAGIC), based on data obtained from field in vestigations and physiochemical properties measured through experiment s such as the organic content, cation exchange capacity, base saturati on, sulfate adsorption capacity, gibbsite coefficient, biomass base ca tion uptake and selectivity coefficient for cations Weathering rates n ecessary to calculate soil chemistry in applying SMB and MAGIC model w ere determined by computation with PROFILE using independent geophysic al properties such as soil texture and mineralogy as the input data, o r by the total soil base cation content correlation. The results have shown that the critical loads of acidity in this area are in the range of 0.76.0 keq ha(-1)yr(-1),indicating sulfur deposition should be cut down by 50-90 percent of the present level The upper soil layer is th e most sensitive. The maximum allowable deposition loading of this are a is also presented in the paper.