Attenuation of a Mixed Chromium and Chlorinated Ethene Ground Water Plume in Estuarine Influenced Glaciated Sediments

• Published in: Ground water monitoring & remediation 2003, Vol.23 (3), p.74-84
• Main Authors: Hellerich, LA, Panciera, MA, Nikolaidis, N P, Smets, B F, Dobbs, G M
• Format: Article
• Language: English
• Subjects: Brackish; ethene
• ISSN: 1069-3629
• DOI: 10.1111/j.1745-6592.2003.tb00685.x

The natural attenuation behavior of a ground water contaminant plume containing chromium and chlorinated ethenes in glaciated sediments was assessed using traditional and nontraditional methods. The mixed waste is transported through and attenuated within an estuarine influenced ground water aquifer of spatially varying redox character and organic carbon content. Contaminant fate and speciation were assessed as a function of geochemical conditions. Total, speciation-based, and sequential chemical extraction analyses were performed to determine contaminant partitioning and the redox capacity of the aquifer. Chromium speciation and partitioning were correlated with the reductive capacity and redox conditions of the aquifer sediments spatially distributed within the aquifer. Reductive dechlorination and partitioning of chlorinated ethenes were correlated with the organic carbon content and redox conditions of the aquifer sediments. The data showed that sharp redox gradients existed within the aquifer. Active reduction and retardation of both chromium and chlorinated ethenes was exhibited. The aqueous hexavalent chromium concentrations decreased to near nondetect levels in the vicinity of the receptor, whereas degradation products of higher-order chlorinated ethenes increased as a fraction of the total chlorinated ethene concentrations along the length of the plume. The potential for competition for reducing power under specific cases within the aquifer was suggested by the data, highlighting the need to include contaminant interactions in natural attenuation assessments.