Bioremediation of toxic metals and metalloids for cleaning up from soils and sediments

Abstract

Pollution of soils and sediments by metals and metalloids is a serious environmental problem and threat to the ecological health and environmental quality. Microorganisms are known capable of detoxifying metals and metaloids into insoluble or non-bioavailable forms so that bioaccumualtion can be prevented under selective conditions. A key issue involved in bioremediation is the very poor understanding on the chemistry of the pollutants, specifically the bioavailable concentartions of metals and metalloids in the environmental matrices, especially soils and sediments and at the relevant pH value. Chemical states of the pollutants in terms of speciation are crucial to the possible success of any remediation practice, but it is impossible to conduct an effective operation for cleaning up without such information in mind. In the literature available, it is a common trend and practice to justify bioremediation for in situ application by using pure cultures of microorganisms, but this is a very prematured and bold attempt to applying microorganisms for in situ cleaning up without any scientific ground to support. For polluted soils and sediments, microorganisms have no role for cleaning up but phytoremediation is an effective means to remove and extract toxic metals and metallods from the complex soil matrices. This has been demonstrated successfully with a number of metals and organics as well as organic pollutants in both laboratory and also field trials.