ADSORPTION AND DESORPTION-KINETICS OF PYRENE ONTO A GREAT-LAKES SEDIMENT

The rate of adsorption and desorption of hydrophobic pollutants with l ake sediments, or other particulate matter, may influence the ultimate fate of these chemicals. This study examined the kinetics of pyrene a dsorption onto, and desorption from, a Great Lake sediment. The data w ere evaluated by two separate mathematical models. The batch pore surf ace diffusion model (BPSDM) predicted initial kinetics much better tha n a radial diffusion model (RDM). This is because the BPSDM incorporat es film diffusion which the RDM neglects. In nonturbulent environments , or systems of low particle concentration, film diffusion has been sh own to be the rate limiting step for the initial adsorption rate. Hyst eresis was experimentally observed for pyrene desorption; therefore, b oth models overpredicted the rate of pyrene desorption. These results indicate that 1) hydrophobic chemicals may be less available for biolo gical degradation and 2) particle concentration may influence the init ial rates of adsorption and desorption.