Abstract：
Low molecular weight organic acids (LMWOAs) are important soil components and play a key role in regulating the geochemical behavior of heavy metal(loid)s. Biochar (BC) is a commonly used amendment that could change LMWOAs in soil. Here, four LMWOAs of oxalic acid (OA), tartaric acid (TA), malic acid (MA), and citric acid (CA) were evaluated for their roles in changing Cd and SB desorption behavior in contaminated soil with (S1-BC) or without BC (S1) produced from Paulownia biowaste. The results showed that OA, TA, MA, and CA reduced soil pH with rising concentrations, and biochar partially offset the pH reduction by LMWOAs. The LMWOAs reduced Cd desorption from the soil at low concentrations but increased Cd desorption at high concentrations, and CA was the most powerful in this regard. The LMWOAs had a similar effect on Sb desorption, and CA was the most effective species of LMWOAs. Adding BC to the soil affects Cd and Sb dynamics by reducing the Cd desorption but increasing Sb desorption from the soil and increasing the distribution coefficient (Kd) values of Cd but lowering the Kd values of Sb. This study helped understand the effects of LMWOAs on the geochemical behavior of Cd and Sb in the presence of biochar, as well as the potential risks of biochar amendment in enhancing Sb desorption from contaminated soil.
摘要：
低分子量有机酸(LMWOAs)是土壤的重要组分,在调控重金属地球化学行为中起着关键作用。生物炭（BC）是一种常用的改良剂，可以改变土壤中的LMWOA。这里,草酸（OA）的四种LMWOA，酒石酸(TA),苹果酸（MA），评估了柠檬酸（CA）在使用（S1-BC）或不使用泡桐生物废弃物产生的BC（S1）的污染土壤中改变Cd和SB解吸行为中的作用。结果表明,OA,TA,MA,随着浓度的增加，CA降低了土壤的pH值，和生物炭部分抵消了LMWOAs的pH降低。LMWOAs在低浓度时减少了土壤中Cd的解吸，但在高浓度时增加了Cd的解吸。CA在这方面是最强大的。LMWOAs对Sb解吸有类似的影响，CA是LMWOA中最有效的物种。向土壤中添加BC通过减少Cd解吸但增加Sb从土壤中解吸并增加Cd的分配系数（Kd）值但降低Sb的Kd值来影响Cd和Sb的动力学。这项研究有助于了解在生物炭存在下LMWOAs对Cd和Sb地球化学行为的影响，以及生物炭改良剂增强Sb从污染土壤中解吸的潜在风险。
