Sorption of chlorobenzenes to mineralizing phytoplankton

Abstract

AbstractThe influence of mineralization of phytoplankton (laboratory Scenedesmus spp.) on the desorption characteristics of 1,2,3,4‐tetrachlorobenzene (TeCB) and hexachlorobenzene (HCB) was studied using a purge and trap 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 models similar to those generally used for desorption from sediments. It was found for all adsorbents that the desorption could adequately be described using a two‐compartment nonequilibrium biosorption model. Generally, HCB was bound more strongly and released more slowly than TeCB. Aging and mineralization of unicell and coenobian forms of the algal species 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 desorption kinetics faster for algae than for soils and sediments. Evaluation of the biosorption rate parameters using a log k2 vs. log Kp plot showed that in contrast to sediments and soils, no clear inverse relationship between Kp 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 the bioconcentration factor with the octano1/water partition coefficient.