| The effect of acid deposition on base cation cycling in a karstic-forested catchment： Evidence from strontium isotopes |
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| 作者姓名： | Houyi ZHENG Congqiang LIU Zhongliang WANG |
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| 作者单位： | [1]State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China [2]Graduate School of the Chinese Academy of Science, Beijing 100039, China |
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| 摘 要： | Bedrock weathering and atmospheric deposition are the two primary sources of base cations （K^＋, Na^＋, Ca^2＋ and Mg^2＋） to forest ecosystems. Therefore, the key problem is to understand the relative inputs from these two sources and the cycling in the ecosystem. This study focuses on the effects of acid deposition on cation cycling in a small-forested karstic catchment in Guizhou Province. Sr isotope ratios were used as a tracer for understanding the transport process between the different cation pools： rock, soil, surface water, atmospheric deposition and plant. The samples of wet deposition, total deposition, throughfall, surface and ground waters, vegetation, and soil were monthly collected. The exchangeable Sr^2＋ and Ca^2＋ in soil samples were extracted by using 1 M ammonium acetate. The leaf-tissue samples were ashed at 550℃, and the residue was digested in ultrapure HClO4 and HNO3. All water samples were filtrated through 0.45 μm aperture filter paper. Base cation concentrations and Sr isotopic composition were analyzed for all the samples. The results show that acid deposition （average pH 4.9） frequently occurred in the studied region. Cation abundance follows an increasing manner from rainwater, throughfall, to surface water or ground water samples, suggesting that acid deposition at first eiuviates Ca^2＋ , Mg^2＋ and Sr^2＋ from leaf, then the exchangeable cations from soil, and at last cations accumulate in surface water or ground water.
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| 关 键 词： | 酸性沉积作用 喀斯特 锶 同位素 雨水 地表水 地下水 |
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