土壤污染具有隐蔽性、 滞后性、 累积性和不可逆转性的特点, 其毒性危害要通过长时间的作物富集和食物链循环才能显现出来。 现阶段, 土壤污染多具有复合污染属性, 如何对典型地区复合污染土壤进行修复和治理, 具有重要的现实意义和理论价值。 西北黄土区是我国重要的黄土分布区, 以模拟Pb和氯吡硫磷复合污染旱田黄土为研究对象, 通过异位柱淋洗实验考察乙二胺四乙酸 (EDTA)对污染黄土的修复效果, 采用紫外分光光度法 (UV)、 原子吸收 (AAS)、 扫描电镜-X射线能谱 (SEM-EDS)、 傅里叶变换红外光谱(FTIR)等光谱手段揭示黄土淋洗特性和机制。 实验结果表明: 淋洗液流速和pH值能不同程度地影响淋洗曲线。 在实验条件下, 经过240 min的淋洗反应, 能去除黄土中70%以上的Pb和90%以上的氯吡硫磷, 淋洗后黄土Pb的有效性大幅度降低。 黄土形貌从淋洗前的表面致密、 凹凸不平变为淋洗后的轮廓不清、 颗粒分散, EDS数据初步解释了淋洗过程Pb的去除和部分土壤元素的淋洗损失。 淋洗过程导致FTIR图谱中部分波峰位移、 消失或峰强减弱, 体现出黄土体系化学环境的变化, 推测淋洗过程对以物理吸附方式与土壤结合的污染物处理效果更好。 应用EDTA异位柱淋洗修复Pb和氯吡硫磷复合污染黄土是可行的, 具有一定实际应用潜力。

The arid loess in northwestern China is one of the dominant soil types nationwide, the removal efficiency of Pb and chlorpyrifos in simulated co-contaminated loess was investigated by ethylene diamine tetra-acetic acid (EDTA) in ex-situ column experiment, and methods of ultraviolet spectroscopy (UV), atomic absorption spectroscopy (AAS), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR) were used to reveal the remediation characteristics and mechanism. The results showed that the flow rate and pH value of EDTA are responsible for the reaction curves. In the experimental conditions, the removal rates of Pb and chlorpyrifos are more than 70% and 90%, respectively, and the bioavailability of heavy metals decreases greatly. The SEM micrographs indicate the dense and rough surface of loess, and unclear surface and enhanced dispersion of particles appear after the reaction. The EDS results explain the phenomenon of Pb removal and elemental loss. The move, disappearance and decrease of wave peaks, shown from FTIR spectra, are the effect of various chemical environment in loess, and the reaction is more appropriate for physisorbed pollutants removal. The achievements are acceptable for co-contaminated loess remediation by EDTA in ex-situ column, showing potential for future application.