Adsorption-desorption behaviors of hydrophobic organic compounds in sediments of Lake Charles, Louisiana, USA

Neutral organic contaminants commonly reside,on the solid portion of soils and sediments. The extent of desorption from these solids determines the fa te, reactivity, and toxicity. Numerous researchers have observed that, afte r an initial exposure of a few days, desorption takes place in two phases, namely, an initial rapid release followed by a long-term resistant phase. R esistant desorption has been highly unpredictable. In this research, the ad sorption and desorption of chlorobenzenes, hexachlorobutadiene, and naphtha lene have been studied using historically and freshly contaminated bayou se diments from Lake Charles, Louisiana, USA. After an initial release period, both laboratory-spiked and historically contaminated sediments exhibit sim ilar desorption profiles. The simulations compare favorably with previous i n situ measurements. All desorption results, both laboratory and field, cou ld reasonably be interpreted using a single irreversible isotherm. Conseque nces of these results in terms of sediment quality criteria (SQC) are also discussed. Finally, an index of fractional irreversible adsorption is propo sed and tested.