SORPTION OF CHLOROBENZENES TO MINERALIZING PHYTOPLANKTON

The influence of mineralization of phytoplankton (laboratory Scenedesm us spp.) on the desorption characteristics of 1,2,3,4-tetrachlorobenze ne (TeCB) and hexachlorobenzene (HCB) was studied using a purge and tr ap method. For comparison several field samples, including a sediment, algae at different growth stages, and freeze-dried algae, were used. The desorption characteristics were evaluated using multiple box model s similar to those generally used for desorption from sediments. It wa s found for all adsorbents that the desorption could adequately be des cribed using a two-compartment nonequilibrium biosorption model. Gener ally, HCB was bound more strongly and released more slowly than TeCB. Aging and mineralization of unicell and coenobian forms of the algal s pecies resulted in a significant 60 to 100% increase of OC-normalized partition coefficients. Generally, sorption affinity as quantified by the OC-normalized partition coefficient (K(oc)) was lower, and desorpt ion kinetics faster for algae than for soils and sediments. Evaluation of the biosorption rate parameters using a log k2 vs. log K(p) plot s howed that in contrast to sediments and soils, no clear inverse relati onship between K(p) and k2 exists. A bioconcentration experiment with four chlorobenzenes showed good agreement with the sorption parameters measured with the purge method, and showed a linear correlation of th e bioconcentration factor with the octanol/water partition coefficient .