Mitigating Airborne PCB Emissions from Sediments with Black Carbon Materials and PCB-Degrading Biofilms

University Of Iowa, Iowa City IA

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Abstract

SUMMARY: PROJECT 5 – REMEDIATION IN SEDIMENTS Polychlorinated biphenyls (PCBs) are commonly encountered organic chemical pollutants of concern at Superfund sites, which are often found in river and lake sediments and in soils near areas of industrial and commercial activity. The Iowa Superfund Research Program (ISRP) has shown that airborne PCB emissions from open water associated with contaminated sediment sources could pose significant inhalation risk to nearby populations. Project 5 research is based on the critical need to develop, evaluate, and demonstrate innovative bioremediation approaches to disrupt the current flux of PCBs from sediments to air at Superfund sites and minimize direct inhalation exposure to humans. Project 5’s central hypothesis is that black carbon materials containing PCB-degrading biofilms will enhance aerobic biodegradation of LC-PCBs in contaminated sediments, thereby reducing their emission into the atmosphere. Our hypothesis builds on discoveries from the current funding cycle that bioaugmentation of suspended aerobic PCB-degrading bacteria into contaminated sediment microcosms, equipped with passive air samplers, results in significantly decreased airborne emission of several LC-PCBs. We also show that aerobic PCB-degrading bacteria form biofilms on black carbon materials, indicating their potential as delivery vehicles for introducing PCB-degrading bacteria into sediments. Guided by these findings, we will test our central hypothesis by: 1) identifying novel strategies for optimizing performance and extending the activity of PCB-degrading biofilm-coated black carbon materials in contaminated sediment microcosms, 2) determining important environmental factors and ecological interactions driving airborne PCB bioremediation performance of biofilm-coated black carbon in mesocosm- scale reactors, and 3) conducting a pilot-scale field demonstration of airborne PCB flux mitigation using biofilm- coated black carbon material bioaugmentation. Our work will rely on the support of ISRP cores for synthesis and analytical assessment of PCBs in study samples. The proposed research is innovative because the relationship between the removal of LC-PCB congeners from sediments and PCB emissions has not been studied. There are currently no developed or tested biotechnologies to decrease or prevent airborne PCB emissions from sediments. Our project is relevant to the SRP mandates because we will develop advanced methods to reduce the amount and toxicity of PCBs in the environment. Outcomes of this project will benefit human health by reducing human exposure to airborne PCBs and realize economic benefits by demonstrating breakthrough alternative PCB remediation approaches that minimize expensive and disruptive measures such as dredging.