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PCB VOLATILIZATION FROM SEDIMENTS

by QI, SHUANG

Abstract (Summary)
In this research, the volatility of PCB was investigated. A simple microcosm of sediment, water and air that allowed for (pseudo) one-dimensional transport of PCB was established to conduct PCB volatilization studies. First, the rate and extent of PCB volatilization from sediment and other substrates spiked with two PCB congeners, 4,4'-dichlorobiphenyl (DCB) and 2,2', 4, 4', 5, 5'-hexachlorobiphenyl (HCB) were determined experimentally. Second, the rate of PCB volatilization from two types of Lake Hartwell sediments, uniformly naturally contaminated with PCBs, was measured. A relationship between the rate of volatilization and the extent of substitution of the PCB with chlorine was accessed. A fundamental mathematical model of PCB transport in a sediment-water-air system was developed. The data obtained from volatilization experiments were applied to validate the one-dimensional mathematical model. The calibrated model was run to simulate various scenarios that led to better understanding of the transport mechanism of PCBs. For all the scenarios investigated, experimental results revealed significant volatilization of DCB from all the different substrates studied. Important observations included: Volatilization of DCB from water was very fast, the higher the water level, the slower the volatilization rate; The rate of volatilization decreased when the sediment lost moisture; the rates of PCB volatilization from contaminated silica sand and betonite clay were very similar and faster than the rate observed for natural sediments but still slower than the rate of volatilization from water; volatilization of PCB was positively correlated with sediment contamination level; volatilization of solid PCBs from glass surfaces was surprisingly fast; PCBs volatilized faster from surfaces covered with a thin water layer than when no water was present; in all cases studied, the volatilization of HCB was dramatically lower than that of DCB. The data obtained from Lake Hartwell study showed significant volatilization of PCBs. PCBs volatilized faster from the deep layer sediment than from the top layer sediment. Results also indicated lower chlorinated congeners volatilized preferentially.
Bibliographical Information:

Advisor:

School:University of Cincinnati

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:pcb volatilization sediments

ISBN:

Date of Publication:01/01/2003

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