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(16-03) Effect of adsorption/desorption on bioavailability of chemical pollutants in soil. Kawamoto, Katsuya*,1, 1 Dept. of Architectural and Environmental Engineering, Kanto Gakuin University, Yokohama, Japan ABSTRACT- In general, biodegradation of organic pollutant in soil and sediment is affected by adsorption phenomenon, which results in apparent slow degradation rate and wide variation of degradation profiles. Aging of a pollutant in soil further cause a possibility of decreasing degradation rate. Therefore, it is important to elucidate the relationship between adsorption/desorption and biodegradation. Bioavailability of environmental chemicals is usually discussed in relation to how easy the chemicals desorb from the soil surface. Then, emphasis is placed on the investigation of desorption profile and the desorbed amount of chemical after adsorption. The adsorption experiment employs several pesticide chemicals (fenitrothion and diazinon, and so on) and PAHs (naphthalene, acenaphthene and phenanthrene, and so on) whose log KOW are from 3 to 5 followed by desorption test. Biodegradation experiment in water that simulates pore water of soil is also conducted using water system prepared from soil slurry. The results show that there exists a fraction which is easy to desorb whereas exists a fraction which is hard to desorb, and accumulated amount of desorption is 40-60 % of adsorbed amount. Further, the amount of desorbed chemical did not depend on the duration of desorption test but also on the number of times of butch experiment. A test and evaluation method is proposed by using a ratio of desorption amount to adsorption amount and first order biodegradation rate constant in water. Key words: bioavailability, soil, adsorption, desorption |
