Nanobioremediation of soils contaminated with lindane: Overview and research challenges

Abstract

γ-hexachlorocyclohexane (γ-HCH, also called γ-BHC and lindane) as a halogenated organic insecticide has become an issue of environmental concern over the years. The isomers of hexachlorocyclohexanes (HCHs) mainly consist of α-HCH, β-HCH, γ-HCH, and δ-HCH. Among these isomers, only γ-HCH has insecticidal applications and thus, leading to cumulative toxic effects through bioaccumulation in food chains. The demand for techniques to decontaminate γ-HCH in soils is gradually growing. The previous studies investigated integrated nanobioremediation techniques involving the use of nanoparticles and indigenous microbes, on the degradation of halogenated organic contaminants, especially lindane, in soils and groundwater. The application of nanomaterials, for instance nanoscale zero-valent iron (nZVI), has recently been researched extensively. However, its efficiency is limited by low aqueous solubility and high hydrophobicity of the contaminants. Moreover, the degradation of contaminants by nanomaterials may not be complete resulting relatively high levels of toxic intermediates. This critical review highlights (i) the applications of nanoparticles for the degradation of γ-HCH (nanoremediation); (ii) the applications of microorganisms for γ-HCH remediation (bioremediation); and (iii) the combination of nanoremediation and bioremediation through the application of nanomaterials and microbes, respectively, in order to achieve effective remediation of γ-HCH (nanobioremediation). Further research on effective biological methods complementing nanoremediation is needed to the development of effective and efficient remediation strategies for recalcitrant halogenated organic contaminants in the subsurface environments.