title: The role of iron in hexavalent chromium reduction by municipal landfill leachate.
abstract: The function of iron (ferric (Fe(III)) and ferrous (Fe(II))) in the hexavalent chromium (Cr(VI)) reduction mechanism by bacteria in municipal landfill leachate (MLL) was assessed. Evidence of an "electron shuttle" mechanism was observed, whereby the Cr(VI) was reduced to trivalent chromium (Cr(III)) by Fe(II) with the resulting Fe(III) bacterially re-reduced to Fe(II). Typically, investigations on this electron shuttle mechanism have been performed in an artificial medium. As MLL comprises an elaborate mixture of bacteria, humic materials and organic and inorganic species, additional complexities were evident within the cycle in this study. Bioavailability of the Fe(III) for bacterial reduction, availability of bacterially produced Fe(II) for chemical Cr(VI) reduction and hydrolysis of Fe(II) and Fe(III) become prevalent during each phase of the shuttle cycle when MLL is present. Each of these factors contributes to the overall rate of bacterial Cr(VI) reduction in this media. This work highlights the need to consider local environmental conditions when assessing the bacterial reduction of Cr(VI).
authors.affiliation: School of Chemical Sciences and Engineering, The University of New South Wales, Sydney 2052, Australia.
authors.forename: Yarong
authors.initials: Y
authors.lastname: Li
authors.forename: Gary K-C
authors.initials: GK
authors.lastname: Low
authors.forename: Jason A
authors.initials: JA
authors.lastname: Scott
authors.forename: Rose
authors.initials: R
authors.lastname: Amal
mesh_terms: D001682:Biological Availability; D002857:Chromium / Q000032:analysis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D009930:Organic Chemicals; D012037:Refuse Disposal / Q000379:methods*; D012989:Soil Pollutants; D013431:Sulfates / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods
chemical_list: D007220:Industrial Waste; D009930:Organic Chemicals; D012989:Soil Pollutants; D013431:Sulfates; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D007501:Iron