Pedosphere 5(3): 193--202, 1995
ISSN 1002-0160/CN 32-1315/P
©1995 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Factors affecting sensitivity of variable charge soils to acid rain
WANG Jing-Hua
Institute of Soil Science, Academia Sinica, Nanjing 210OO8 (China)
ABSTRACT
      The sensitivity of a large number of variable charge soils to acid rain was evaluated through examining pH-H2SO4 input curves. Two derivative parameters, the consumption of hydrogen ions by the soil and the acidtolerant limit as defined as the quantity of sulfuric acid required to bring the soil to pH 3.5 in a 0.001mol L-1 Ca(NO3)2 solution, were used. The sensitivity of variable charge soils was higher than that of constant charge soils, due to the predominance of kaolinite in clay mineralogical composition. Among these soils the sensitivity was generally of the order lateritic red soil > red soil > latosol. For a given type of soil within the same region the sensitivity was affected by parent material, due to differences in clay minerals and texture. The sensitivity of surface soil may be lower or higher than that of subsoil, depending on whether organic matter or texture plays the dominant role in determining the buffering capacity. Paddy soils consumed more acid within lower range of acid input when compared with upland soils, due to the presence of more exchangeable bases, but consumed less acid within higher acid input range, caused by the decrease in clay content.
Key Words:  acid-tolerant limit, sensitivity to acid rain, variable charge soil
Citation: Wang, J. H. 1995. Factors affecting sensitivity of variable charge soils to acid rain. Pedosphere. 5(3): 193-202.
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