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Transitioning From GCIP to GAPP: Opportunities and Challenges

 

 Environmental Sciences Seminar Abstract

In-Situ PCB Dechlorination in Sediments Using Nanoscale Zero-Valent Iron
Kevin Gardner
Environmental Research Group
University of Hampshire
 

This presentation will begin by providing an overview of various research initiatives that are currently underway. These include a number of projects related to contaminated sediments, and a couple related to chemical weathering, leaching, and risk analysis of recycled materials. The focus of the presentation will be the development of a treatment technology that uses colloidal elemental iron to affect the reductive dechlorination of PCBs to biphenyl, the objective of which is to remediate PCBs in marine and fresh water sediments in-situ in a cost-effective manner.

Experiments are being conducted using PCB-contaminated sediment from the Housatonic River and the New Bedford Harbor, both in Massachusetts, under ambient conditions approximating those of in-situ sediment. Laboratory studies are investigating a number of different types of iron, and optimizing the amount added and frequency of application. A mass balance is being developed to determine the breakdown mechanisms and if PCB reduction can be accounted for by lesser chlorinated congeners and biphenyl. Results have shown that PCBs can be reduced by 63% in a fine-grained, organic-rich marine sediment and by 95% in a sandy river sediment in approximately one day with one application of 3% zero-valent iron to sediment. Rate constants for dechlorination were estimated to be 0.1422 d-1 and 3.2871 d-1, respectively. Adding a greater concentration of ZVI did not increase removal proportionally, and no substantial reduction takes place after approximately one week. It is hypothesized that PCB dechlorination in fine-grained, organic-rich sediments is limited by desorption of the strongly bound fraction of PCBs. Preliminary results also indicate that higher chlorinated PCBs do indeed become dechlorinated to lower chlorinated PCB congeners and biphenyl upon reaction with colloidal ZVI. Full scale application of the technology is being planned in collaboration with the private sector, and this aspect of the work will also be discussed

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