Speciation and Isotopic Composition of Sulfur in Limestone Soil and Yellow Soil in Karst Areas of Southwest China: Implications of Different Responses to Acid Deposition
- Wei Zhang *a,
- Cong-Qiang Liubc,
- Zhong-Liang Wangb,
- Li-Li Zhang *c and
- Xu-Qiang Luoa
- a Luo, School of Geography and Tourism, Guizhou Normal College, Gaoxin Road No. 115 Wudang District Guiyang 550018, China
b Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal Univ., Binshuixidao Road No. 393 Xiqing District Tianjin 300387, China
c State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guanshui Road No. 42 Nanming District Guiyang 550002, China
a School of Geography and Tourism, Guizhou Normal College, Gaoxin Road No. 115 Wudang District Guiyang 550018, China
The contents and stable S isotope ratio (δ34S) values of total S, organic S, SO42−–S, and total reduced inorganic S (TRS) in typical limestone soil and yellow soil were analyzed in this study to examine the general distributions of S forms and their δ34S values in soils in karst areas of southwest China. Under a similar level of acid deposition, the vertical profiles of the S forms and their δ34S values differed in limesto\ne soil and yellow soil, indicating the different geochemical responses of these soils to acid deposition. The deposited SO42− was retained as organic S in both soils. The depletion in 34S of TRS relative to SO42− and the parallel increasing δ34S values of TRS and SO42− indicate a bacterial reduction process of sulfate in both soils. The different extents of C-bonded S mineralization and organic sulfate transport explain the different vertical profiles of total S and organic S contents in both soils. Sulfate adsorption in limestone soil was negligible because of high pH values. Sulfate adsorption in yellow soil was another important S retention process in addition to biological S retention to form organic S and TRS because of low pH values. The effect of acid deposition on yellow soil appeared more serious because of the accumulation and leaching of deposited SO42−, which can result in soil acidification and accelerate the loss of basic cations from yellow soil. However, compared with yellow soil, limestone soil released more S into rivers by organic S mineralization after a large decrease in annual S deposition rate.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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