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Reductive Degradation of p,p'-DDT by Fe(II) in Nontronite NAu-2

Lookup NU author(s): Dr Claire Fialips, Dr Martin Jones, Maggie White, Dr Neil Gray

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Abstract

Clay minerals are abundant in soils and sediments and often contain Fe. Some varieties, such as nontronites, contain as much as 40 wt.% Fe2O3 within their molecular structure. Several studies have shown that various Fe-reducing micro-organisms can use ferric iron in Fe-bearing clay minerals as their terminal electron acceptor, thereby reducing it to ferrous iron. Laboratory experiments have also demonstrated that chemically or bacterially reduced clays can promote the reductive degradation of various organics, including chlorinated pesticides and nitroaromatics. Therefore, Fe-bearing clays may play a crucial role in the natural attenuation of various redox-sensitive contaminants in soils and sediments. Although the organochlorinated pesticide p,p'-DDT is one of the most abundant and recalcitrant sources of contamination in many parts of the world, the impact of reduced Fe-bearing clays on its degradation has never been documented. The purpose of the present study was to evaluate the extent of degradation of p,p'-DDT during the bacterial reduction of Fe(III) in an Fe-rich clay. Microcosm experiments were conducted under anaerobic conditions using nontronite (sample NAu-2) spiked with p,p'-DDT and the metal-reducing bacteria Shewanella oneidensis MR-1. Similar experiments were conducted using a sand sample to better ascertain the true impact of the clay vs. the bacteria on the degradation of DDT. Samples were analyzed for DDT and degradation products after 0, 3, and 6 weeks of incubation at 30°C. Results revealed a progressive decrease in p,p'-DDT and increase in p,p'-DDD concentrations in the clay experiments compared to sand and abiotic controls, indicating that Fe-bearing clays may substantially contribute toward the reductive degradation of DDT in soils and sediments. These new findings further demonstrate the impact that clay materials can have on the natural attenuation of pollutants in natural and artificial systems and open new avenues for the passive treatment of contaminated land.


Publication metadata

Author(s): Fialips CI, Cooper NGA, Jones DM, White ML, Gray ND

Publication type: Article

Journal: Clays and Clay Minerals

Year: 2010

Volume: 58

Issue: 6

Pages: 821-836

Print publication date: 01/12/2010

ISSN (print): 0009-8604

ISSN (electronic): 1552-8367

Publisher: The Clay Minerals Society

URL: http://dx.doi.org/10.1346/CCMN.2010.0580610

DOI: 10.1346/CCMN.2010.0580610


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