BIPHASIC DESORPTION OF HYDROPHOBIC ORGANIC CONTAMINANTS IN HIGHLY ORGANIC WETLAND SOILS

摘要

Sorption/desorption studies were conducted to determine desorption-resistance of hydrophobic organic compounds (HOCs) in recently deposited wetland peat soils. Sorption/desorption characteristics of chlorobenzene and phenanthrene were investigated for highly organic surface (top 0-2 cm) and deeper fresh marsh soil (below 10-cm) and low organic Petro Processors, Inc. Superfund site Devil's Swamp wetland soil (PPI soil) and Bayou Manchac soil (BM soil). A biphasic desorption model was used to fit the sorption/desorption data to explain the desorption-resistance in wetland soils. The results of biphasic desorption model indicated the presence of appreciable desorption-resistant phase in wetland soils. A finite maximum capacity of desorption-resistant fraction (q_(max)~(irr)) was observed after several desorption steps. When organic carbon normalized, q_(max,oc)~(irr) of the wetland soils was smaller than those of PPI and BM soils. The apparent organic carbon based partition coefficient (K_(oc)~(irr)) for the desorption-resistant compartment was increasing in order of surface (10~(5.49 +- 0.04)) < deeper (10~(4.75 +- 0.13)) < PPI (10~(5.39 +- 0.09)) < BM (10~(5.49 +- 0.04)) soil. The results suggest that the effect of desorption-resistance on the bioavailability of sorbed HOCs should be considered in remediation and risk assessments in wetlands.