Mobilization of soil organic matter by complexing agents and implications for polycyclic aromatic hydrocarbon desorption

Complexing agents are frequently used in treatment technologies to remediat e soils, sediments and wastes contaminated with toxic metals. The present s tudy reports results that indicate that the rate and extent of soil organic matter (SOM) as represented by dissolved natural organic carbon (DNOC) and polycyclic aromatic hydrocarbon (PAH) desorption from a contaminated soil from a manufactured gas plant (MGP) site can be significantly enhanced with the aid of complexing agents. Desorption of DNOC and PAH compounds was pH dependent, with minimal release occurring at pH 2-3 and maximal release at pH 7-8. At pH similar to6, chelate solutions were shown to dissolve large a mounts of humic substances from the soil compared to controls. The complexi ng agents mobilized polyvalent metal ions, particularly Fe and Al from the soil. Metal ion chelation may disrupt humic-(metal ion)-mineral linkages, r esulting in mobilization of SOM and accompanying PAH molecules into the aqu eous phase; and/or reduce the degree of cross-linking in the soil organic m atter phase, which could accelerate PAH diffusion. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.