关键词: ：铅污染土壤, 柠檬酸, 苹果酸, 复配淋洗

Abstract: To explore the effect of environmentally friendly organic acids on the washing repair effect and washing mechanism of lead-contaminated soil, this paper investigates the effect of eluent on the lead elution effect in soil under different parameters (concentration, liquid-to-solid ratio, time, pH value) by oscillating washing method, and conducts compound washing of citric acids and malic acids under optimal conditions. The results show that the removal rates of lead by single washing of citric, malic and tartaric acids are 76.87%, 69.73% and 61.39% respectively. When the compound ratio of citric and malic acids is 3∶2, the washing rate of lead is as high as 87.31%, and the washing toxicity concentration of lead in soil reduces to 3.71 mg/L after compound washing, which is lower than the identification standard value of hazardous waste. The results of the mechanism analysis show that compound washing can effectively reduce the content of extractable state, reducible state and oxidizing state in the weak acids of the lead-contaminated soil, increase the content of the residuary fraction, and reduce the subsequent environmental risks.Possible mechanisms of Pb removal by compound washing include acid dissolution, ion exchange, and surface complexation. The compound of citric and malic acids is an efficient and environmentally friendly washing agent, which provides a reference for the remediation of lead-contaminated soil in the future.