Discipline of Microbiology, School of Biochemistry, Genetics and Microbiology, Faculty of Science and Agriculture, University of KwaZulu-Natal (Westville Campus), Durban 4000, South Africa.
Chemosphere. 2011 Oct;85(5):839-47. doi: 10.1016/j.chemosphere.2011.06.091. Epub 2011 Jul 16.
1,2-Dichloroethane (1,2-DCA) is one of the most hazardous pollutant of soil and groundwater, and is produced in excess of 5.44×10⁹ kg annually. Owing to their toxicity, persistence and potential for bioaccumulation, there is a growing interest in technologies for their removal. Heavy metals are known to be toxic to soil microorganisms at high concentrations and can hinder the biodegradation of organic contaminants. In this study, the inhibitory effect of heavy metals, namely; arsenic, cadmium, mercury and lead, on the aerobic biodegradation of 1,2-DCA by autochthonous microorganisms was evaluated in soil microcosm setting. The presence of heavy metals was observed to have a negative impact on the biodegradation of 1,2-DCA in both soil samples tested, with the toxic effect being more pronounced in loam soil, than in clay soil. Generally, 75 ppm As³⁺, 840 ppm Hg²⁺, and 420 ppm Pb²⁺ resulted in 34.24%, 40.64%, and 45.94% increase in the half live (t½) of 1,2-DCA, respectively, in loam soil, while concentrations above 127.5 ppm Cd²⁺, 840 ppm Hg²⁺ and 420 ppm of Pb²⁺ and less than 75 ppm As³⁺ was required to cause a >10% increase in the t½ of 1,2-DCA in clay soil. A dose-dependent relationship between degradation rate constant (k₁) of 1,2-DCA and metal ion concentrations was observed for all the heavy metals tested, except for Hg²⁺. This study demonstrated that different heavy metals have different impacts on the degree of 1,2-DCA degradation. Results also suggest that the degree of inhibition is metal specific and is also dependent on several factors including; soil type, pH, moisture content and available nutrients.
1,2-二氯乙烷（1,2-DCA）是土壤和地下水中最危险的污染物之一，每年的产量超过 5.44×10⁹kg。由于其毒性、持久性和生物累积潜力，人们越来越关注去除这些污染物的技术。重金属在高浓度下对土壤微生物是有毒的，并会阻碍有机污染物的生物降解。在这项研究中，评估了重金属（砷、镉、汞和铅）对土著微生物有氧生物降解 1,2-DCA 的抑制作用，实验是在土壤微宇宙环境中进行的。研究结果表明，重金属的存在对两种土壤样品中 1,2-DCA 的生物降解均有负面影响，且在壤土中，其毒性效应比在粘土中更为明显。一般来说，在壤土中，75ppm 的 As³⁺、840ppm 的 Hg²⁺和 420ppm 的 Pb²⁺分别使 1,2-DCA 的半衰期（t½）增加了 34.24%、40.64%和 45.94%，而在粘土中，Cd²⁺浓度超过 127.5ppm、Hg²⁺浓度超过 840ppm 和 Pb²⁺浓度超过 420ppm，以及 As³⁺浓度低于 75ppm 就会导致 1,2-DCA 的 t½增加超过 10%。除 Hg²⁺外，所有测试的重金属的 1,2-DCA 降解速率常数（k₁）与金属离子浓度之间均存在剂量依赖性关系。该研究表明，不同的重金属对 1,2-DCA 降解程度的影响不同。结果还表明，抑制程度是特定于金属的，还取决于土壤类型、pH 值、含水量和可用养分等多个因素。
