DESORPTION OF CHLOROBENZENES FROM NATURAL SUSPENDED-SOLIDS AND SEDIMENTS

The desorption of chlorobenzenes from heterogeneous suspended solid mi xtures and sediments at nonequilibrium conditions was investigated, us ing a gas purge method. This technique offers the possibility to measu re equilibrium and rate data from adsorbent suspensions, without phase separation. The desorption patterns were interpreted and fitted in te rms of multiple box models. The results show that when the equilibrati on time for sediment suspensions contaminated in the laboratory is lon ger, desorption is slower. At nonequilibrium conditions, the more hydr ophobic chlorobenzenes are released faster than the less hydrophobic o nes. For ten suspended solid samples the model parameters were related to adsorbent characteristics, such as organic matter, phytoplankton a nd clay content by means of correlation analysis, and compared to simi lar desorption data for algal cultures obtained in earlier studies in our laboratory. It was found that all desorption data could be describ ed with a two-compartment desorption model. The partition coefficient was proportional to the content of organic matter, which in turn was m ainly determined by the concentration of phytoplankton in the samples. The desorption rate was positively correlated with the phytoplankton content as well. This suggests that phytoplankton cells form an easily accessible fraction of the total adsorbent.