Zero-valent iron's effectiveness at dehalogenating chlorobenzenes and its feasibility as a reactive cap
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Through the deliberate or inadvertent release to the environment, contaminants have polluted the nation's waterways leaving a residual of refractory pollutants that reside in sediments. The Bayou d'Inde is a tributary of the Calcasieu River outside Lake Charles, Louisiana that has been contaminated by several industrial pollutants including hexachlorobenzene (HCB). Due to HCB's high organic carbon partition coefficient (Koc), its availability to reducing microorganisms is extremely limited and natural attenuation has been found to be ineffective at reducing HCB concentrations in-situ. The effectiveness of an active cap is being evaluated to reduce contaminant flux to the benthos and water column. This study was designed to explore the fate of chlorinated benzenes during capping of the contaminated sediment, specifically the fate associated with zero-valent iron in an active capping layer. Experiments exploring the degradation of chlorinated benzenes with mirco-scale and nano-scale zero-valent iron and the potential for zero-valent iron as an active capping material to encourage dechlorination under environmentally relevant and ideal conditions were carried out. Less than 1% of the chlorinated benzenes were observed to dechlorinate within 48 hours by micro-scale zero-valent iron and transport through a 1.25 cm thick CETCO mat would dechlorinate 8% of the mobile hexachlorobenzene before release to the water column. That is why zero-valent iron should not be employed as an active capping material in the Bayou d'Inde for the purposes of reductively dechlorinating chlorinated benzenes.