Danny
Reible
Chevron
Professor of Chemical Engineering
Director,
Hazardous Substance Research Center
Louisiana
State University
3221
CEBA, Louisiana State University, Baton Rouge, LA 70803
Abstract
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Monitoring of release or degradation of organic contaminants in soils and sediments often shows a period of relatively rapid change followed by a period of slow or no change. The desorption-resistant nature of these contaminants has been attributed to sequestration of the contaminants in the soil or sediment matrix. Studies have suggested that this sequestration may be associated with the nature of the sorbing media or with conformational or other changes of the contaminants in the media. Regardless of the cause, however, the observation of desorption-resistance has led to suggestions that these contaminants may not be available to organisms and therefore may not need to be included when assessing potential contaminant uptake and risk to human and ecological health and the natural recovery of contaminated sediment systems. This hypothesis is tested by preparing and characterizing the desorption-resistant fraction of sediments contaminated with polynuclear aromatic hydrocarbons and challenging this desorption-resistant fraction with biological assays. The presentation will focus on the availability and mobility of these contaminants to benthic worms. Deposit-feeding benthic worms represent an intense sediment processing environment that can overcome mass transfer resistances that may complicate assessment of bioavailability in other organisms. Deposit-feeding benthos also contribute significantly to the transport of contaminants from sediments to the overlying water and into the food chain. Mathematical models describing the observed sorption-desorption phenomena as well as the uptake and elimination in the benthic organisms will also be discussed.
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