Iron-induced reductive dechlorination: a sustainable remedial strategy to cleanup legacy dieldrin impacted groundwater

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Title: Iron-induced reductive dechlorination: a sustainable remedial strategy to cleanup legacy dieldrin impacted groundwater
Author: Fisher, Michael
Abstract: Fisher, Michael R. Master of Environmental Assessment. Iron-induced Reductive Dechlorination: A Sustainable Remedial Strategy to Cleanup Legacy Dieldrin?-A review An organo-chlorine compound is typically defined as a chlorinated hydrocarbon with a minimum of one chlorine atom covalently bonded to the structure. Organochlorines include solvents like tetrachloroethene (also known as perchloroethene, or PCE) and trichloroethene (TCE) as well as pesticides such as dichlorodiphenyltrichloroethane (DDT), chlordane, heptachlor, lindane, toxaphene, aldrin, and dieldrin. Organochlorines with more than four chlorine atoms are known as persistent organic pollutants (POPs). Over a period of nearly 25 years (1950 to 1974), dieldrin, and organochlorine pesticide, was widely applied to crops (cotton, corn and citrus), used to control locusts, mosquitoes and termites, and also used as a wood preservative. Dieldrin is also a degradation product of aldrin, another insecticide. Dieldrin has 6 chlorine atoms, is a known carcinogen, has a relatively high octanol-water partitioning coefficient (Kow) and moderate water solubility. Dieldrin’s soil adsorption coefficient, or Koc is log 6.77 (ATSDR) which demonstrates its strong affinity for carbon sorption. Due to these physico-chemical characteristics, dieldrin sorbs strongly to organic matter, desorbs very slowly, and, thus, naturally attenuates very slowly. Due to its high Kow , (approximately log 6.2, ATSDR) dieldrin will bioaccumulate throughout an ecosystem. Dieldrin’s widespread distribution and ecological concentration has led scientists to conclude that the detection of low concentrations of dieldrin in the environment misrepresents the overall toxicological risk (Wurster, 2010). Research on biotic and abiotic reductive dehalogenation of organochlorine pesticides and chlorinated solvents (PCE and TCE) spans 48 years (Castro and Belser, 1968) and 27 years (Freedman and Gossett. 1989), respectively. First implemented more than two decades ago, reductive dechlorination has become a commonly implemented, successful remedial strategy for cleanup of smaller organochlorine solvents, such as PCE or TCE, in groundwater. This paper addresses the prospect of reductive chlorination cleanup of organochlorine pesticides like dieldrin, specifically for groundwater. Both biotic and abiotic RD processes are considered as well as the reported synergistic effect that occurs between them. Because pesticides are created for the intended purpose of rendering toxic effects to biological organisms, the success of biotic reductive dechlorination is unpredictable. This paper reviews and discusses the research performed to date regarding the successes and efficacies of various processes for reductive chlorination of dieldrin in groundwater. Special focus is made on the use of iron (Fe) and iron-containing compounds. Additionally, sustainability indicators and applied typical remedial technologies to assess their comparative sustainability. A developed Sustainable Remedial Technology decision graphic tool is presented to assist stakeholders in their evaluation of remedial strategy sustainability. This paper also offers a relative spatial analysis of dieldrin-impacted sites in the southeastern U.S. This region’s history of agricultural (cotton and citrus crops) resulted in a heritage of former manufacturing plants, storage/distribution warehouses, and associated facilities (dumps) impacted by dieldrin. All of these sites are potential targets for application of the remedial strategy of RD. The persistence of dieldrin on agricultural lands, commercial and residential sites, and recreational facilities presents a barrier to redevelopment of these lands and future economic improvement.
Date: 2016-04

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