Chromium has long been recognized as a toxic, mutagenic and carcinogenic metal. It is toxic to microorganism, plants, animals and humans. Chromium exists in environment in two stable forms: Cr(VI) and Cr(III). Cr(III) is less toxic and insoluble, while Cr(VI) is extremely toxic and highly soluble. Chromium is used in many industrial applications, but it poses a threat to local environment. The effluents and solid wastes from the mining, chrome-plating, leather-tanning, and dye-manufacturing industries are high in chromium concentration and identified as a major health hazard because of pollution to the environment. Industrial waste is used in landfilling, which causes the seepage, and the leaching of toxic chromium from soil into water bodies poses a threat to the environment. Ferrochrome industry is one of the biggest contributors of the chromium pollution to the water bodies. South Africa has the world’s largest chromium reserve. The waste materials produced by ferrochrome industry are slag, dust and processed water. These wastes have high chromium concentration that can cause pollution to the environment. Inhalation is the major exposure route of the Cr(VI) toxicity in humans. The bioremediation of Cr(VI) to Cr(III) in the polluted site is a cost-effective and ecofriendly solution for preventing chromium detoxification. Bioremediation can be in situ or ex situ, and choice of remediation method depends upon the extent of pollution and the nature of the site. This paper summarizes the chromium pollution caused by ferrochrome industries, current remediation method adopted by ferrochrome industries, and the possible new methods for effective bioremediation. This paper focuses mainly on bioremediation techniques to convert the high-toxic form of chromium to less-toxic and mobile form of chromium.

中文翻译：

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环境中的铬，铬铁矿开采和铬铁行业的毒性作用及其可能的生物修复

长期以来，铬一直被认为是有毒，致突变和致癌的金属。它对微生物，植物，动物和人类有毒。铬以两种稳定的形式存在于环境中：Cr（VI）和Cr（III）。Cr（III）的毒性小且不溶，而Cr（VI）的毒性大且易溶。铬被用于许多工业应用中，但对当地环境构成威胁。采矿，镀铬，皮革鞣制和染料制造行业的废水和固体废物中的铬浓度很高，由于对环境的污染，被确定为主要的健康危害。工业垃圾被用于填埋，导致渗漏，有毒铬从土壤中浸入水体对环境构成威胁。铬铁行业是水体中铬污染的最大贡献者之一。南非拥有世界上最大的铬储量。铬铁行业产生的废料是炉渣，粉尘和加工水。这些废物的铬含量很高，可能对环境造成污染。吸入是人体六价铬（VI）毒性的主要暴露途径。在受污染的地点将Cr（VI）修复为Cr（III）是一种经济高效且环保的解决方案，可防止铬的解毒。生物修复可以是原位或异位的，修复方法的选择取决于污染程度和现场性质。本文概述了铬铁行业引起的铬污染，铬铁行业目前采用的补救方法，以及可能进行有效生物修复的新方法。本文主要集中在生物修复技术上，以将高毒性形式的铬转化为低毒性和可移动形式的铬。