铅污染不同粒径土壤的重金属地球化学行为与风险

摘要

In this report, fine particle fractions of sand, silt, coarse clay, and fine clay in lead-polluted soil were extracted through wet extraction. Particle size distribution, heavy metal content, mineral composition, and morphology, as well as their chemical mobility, accumulation factor and ecological health risk were studied using laser particle size analyzer, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectrometer (FTIR) and BCR sequential extraction methods. It is found that the amount of total organic carbon (TOC) and heavy metals in different size fractions of the fine particles increases as the particle size decreases. Accumulation factor, mobility factor and ecological health risk follow the same trend. More importantly, the amount of oxidizable lead also increases as the particle size decreases. Whereas, exchangeable chromium, copper and zinc are mostly accumulated in larger sized soil fine particles. In general, heavy metals in finer particles of lead-polluted soil have higher ecological risk, but especially for Cu and Pb in nano-sized clay particles, which have the greatest accumulation factor and mobility. Therefore, effective remediation and control of heavy metal pollutants in Lead-Polluted Soil should be carried out.%通过湿法提取铅污染土壤中的细砂粒、粉粒、粗粘粒和细粘粒组分,利用激光粒度分析仪、透射电镜(TEM)、X射线衍射仪(XRD)、傅里叶红外光谱(FTIR)和重金属形态连续提取的 BCR 方法,研究不同粒径细砂粒、粉粒、粗粘粒和细粘粒组分的重金属含量分布、矿物组成、形态分布与化学活性、迁移累积特征、生态健康风险等.结果表明,铅污染土壤中细砂粒、粉粒、粗粘粒和细粘粒组分随着颗粒物粒径的减少,总有机碳和重金属含量升高,其累积因子、活性系数和潜在生态风险指数也相对增大,特别是重金属铅的可氧化态含量显著升高.而可交换态重金属 Cr、Cu、Zn 则在大粒径组分中的含量较高.从综合潜在生态风险来看,铅污染土壤重金属元素在不同粒径细颗粒组分中,具有极强的潜在生态风险,在粒径特别小的纳米级天然细粘粒组分中重金属Pb和Cu具有更大的累积因子、活性系数和潜在生态风险,应采取有效措施对铅污染土壤重金属污染进行修复与治理.