Modeling and Decision Support Tools Based on the Effects to Sediment Geochemistry and Microbial Populations on Contaminant Reactions in Sediments

摘要

The proper management of polychlorinated biphenyl (PCB)-contaminated sediment has proven to be a wide-spread, complex, and costly issue. PCBs are a primary contaminant driving risk at many Department of Defense facilities. There is a need for sound science and effective tools to characterize and manage these sites and their associated risks. The focus of this project was on the role of site-specific differences in geochemistry and microbial populations in the transformation of polychlorinated biphenyls (PCBs) in sediments. Laboratory analysis of sediment samples and microcosm-based PCB dechlorination experimentation were used to enhance our understanding of microbial populations that are capable of dechlorinating PCBs. Undisturbed sediments from the Grasse River in Massena, New York, show extensive dechlorination and the presence of PCB dechlorinating bacteria throughout the sampled core, suggesting monitored natural attenuation has significant potential as a remediation strategy. Two rivers sediments (Grasse and Hudson) show significantly different native microbial populations and different concentrations of organic materials, iron and sulfate. Amended microcosm studies indicate the concentration of iron and sulfate affect rate, extent and pathways of dechlorination. The development of advanced modeling tools was used to enhance prediction of dechlorination and evaluate the likelihood of natural attenuation at specific sites. Classification trees were developed to predict PCB pathways that are likely to be observed when specific processes are active in contaminated sediments. A dechlorination process estimator was developed to enable more accurate identification of processes occurring in PCB-contaminated sediments.