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Effects of low-molecular-weight organic acids and residence time on desorption of Cu, Cd, and Pb from soils

机译：低分子量有机酸和停留时间对土壤中铜，镉和铅解吸的影响

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Effects of low-molecular-weight organic acids (LMWOAs) and residence time on desorption of Cu, Cd, and Pb from two typical Chinese soils were studied. Citric, malic, and acetic acids were chosen as representatives of LMWOAs commonly present in soils. CaCl2 and NaNO3 were used in desorption as they were main soil background electrolytes for comparison. Desorption of Cu, Cd, and Pb from both soils followed the descending order: citric acid > malic acid > acetic acid > CaCl2 > NaNO3, which was consistent with the order of stability of Cu-, Cd-, and Pb-LMWOAs complexes from large to small and ion exchange ability of Ca2+ and Na+. Desorption of metals by inorganic salts decreased with increasing desorption solution pH. Whereas desorption of metals by LMWOAs showed different trend in response to pH change due to their different complexing abilities. Malic and acetic acids released less metals at low pH 3.1 compared with citric acid at pH 7, indicating that pH was not the dominant factor governing the release of metals. In addition, all LMWOAs desorbed more metals than inorganic salts, CaCl2 and NaNO3. Therefore, organic ligands played a dominant role in desorption of heavy metals. More metals were released from Jiangxi soil than from Heilongjiang soil due to lower soil pH, CEC, organic matter content and manganese oxide of Jiangxi soil. Generally, desorption of metals decreased with increasing residence time of metals in soils. (C) 2004 Elsevier Ltd. All rights reserved.
机译：研究了低分子量有机酸（LMWOA）和停留时间对两种典型中国土壤中Cu，Cd和Pb解吸的影响。选择柠檬酸，苹果酸和乙酸作为土壤中常见的LMWOA的代表。 CaCl2和NaNO3用作解吸的主要土壤背景电解质，用于比较。两种土壤中的Cu，Cd和Pb的解吸顺序依次为：柠檬酸>苹果酸>乙酸> CaCl2> NaNO3，这与Cu-，Cd-和Pb-LMWOAs络合物的稳定性顺序一致。 Ca2 +和Na +的离子交换能力大到小。无机盐对金属的解吸随着解吸溶液pH值的增加而降低。而LMWOA对金属的解吸由于其不同的络合能力而对pH的变化表现出不同的趋势。与pH为7的柠檬酸相比，苹果酸和乙酸在pH为3.1时释放的金属较少，这表明pH值不是控制金属释放的主要因素。此外，所有LMWOA都比无机盐CaCl2和NaNO3解吸更多的金属。因此，有机配体在重金属的解吸中起主要作用。由于土壤pH值，CEC，有机质含量和氧化锰含量降低，江西土壤释放的金属比黑龙江土壤释放的金属更多。通常，金属的解吸随着金属在土壤中停留时间的增加而降低。 （C）2004 Elsevier Ltd.保留所有权利。

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    Qin F; Shan XQ; Wei B;

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