APPLICATION OF A PERMEANT POLYMER DIFFUSIONAL MODEL TO THE DESORPTION OF POLYCHLORINATED-BIPHENYLS FROM HUDSON RIVER SEDIMENTS

The desorption of polychlorinated biphenyls (PCBs) from Hudson River sediments was examined using XAD-4 resin as a PCB adsorbent. Both a rapidly desorbing labile component and a more slowly desorbing resistant component were observed. The fraction of PCBs in the resistant component was found to be a function of PCB concentration and total organic carbon in the sediment, independent of inorganic particle size. Milling the sediment had no effect on PCB desorption, while pretreatment of the sediment using heat (with and without caustic addition) enhanced the rate of desorption and significantly decreased there distant fraction. We propose that the labile and resistant fractions arise from disparate diffusional rates of PCBs from the swollen and condensed phases of the sediment organic matter. Diffusion coefficients of 2.6 X 10(-18) and 7.3 X 10(-21) cm2/s for PCBs in the condensed and swollen humic polymer are calculated using a permeant/polymer diffusional model, with calculated diffusional distances on the order of 1 x 10(-6) cm.