制革场地土壤和地下水中铬污染来源及污染特征研究进展

近年来，制革场地土壤和地下水中的铬污染引起了国内外广泛关注。通过分析制革工艺流程、废水和固废的性质及其处置的历史与现状，提出制革场地的铬污染源自含铬浴液和废水的滴漏以及固废和污泥的不当堆置与填埋。制革场地土壤铬污染以三价铬为主，六价铬含量相对较低，但部分仍远超国家标准限值。污染主要集中于生产车间、污泥存放点和废水排放点，场地表层土壤全铬远高于深层土，且污染时间短的场地土壤中有效态铬（交换态铬和水溶态铬）含量较高；而地下水中的总铬和六价铬，受土壤铬分布、污染时间、水文地质等多种因素影响。针对制革场地伴有酸碱和有机物污染的特点，进一步论述了有机物和土壤pH对铬在土壤中环境效应（迁移、形态转化和氧化）的影响，指出应重点关注有效态铬和六价铬的含量和形成机制。最后讨论了制革场地铬的环境风险防控主要面临的挑战和对策。

Progresses in Research on Sources and Characteristics of Chromium Pollution in Soils and Groundwater of Tannery Sites

In recent years, the issue of chromium pollution in tannery sites has attracted widespread attention. Through analyzing their tanning process, properties of the wastewater and solid waste discharged from tanning and history and status quo of their disposal, this paper points out that irrational disposal of these chromium-containing wastes and inadvertent dripping and leaking of chromium-containing liquor are the main sources of chromium pollution in tannery sites, and characterizes the chromium pollution in their soils and groundwater. The soils are mainly polluted by trivalent chromium rather than hexavalent chromium. However, the contents of total chromium and hexavalent chromium in some tannery sites far exceed the limit set in the national standards for soil environmental safety. Soil chromium content is characterized by site regional distribution, vertical distribution, and fractionation. Chromium polluted soil is mainly located in sludge disposal sites, workshops, and waste water discharge sites. The content of total chromium is high in the surface soil, and decreases gradually with soil depth. In the soils short in exposure to pollution, the content of available chromium (e.g., water soluble and exchangeable) is higher, while in the soils long in exposure to pollution, stable fractions, such as residue, dominate in content. Total chromium and hexavalent chromium are detected in groundwater, and the content of chromium is affected by factors, such as soil chromium content, time of exposure to pollution, and hydrogeology. As tannery sites are also exposed to organic pollution and acid-base pollution, this paper further elaborates effects of organic pollutants and soil pH on chromium behaviors, such as redox, fractionation, and transport in the soil. This paper points out that researches should be focused on contents and formation mechanism of available chromium and hexavalent chromium. In the end, the paper discusses the main challenges faced and countermeasures to be adopted in preventing the environmental risk of chromium pollution in tannery sites.