[Nonlinear sorption behaviors of chlorobenzenes on sediments]

Sorption isotherms of chlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene on 5 sediments were examined to understand its sorption behavior. All systems examined exhibits nonlinear sorption. All sorption isotherms are nonlinear as evidenced by the Freundlich n values of 5 sediments being between 0.858 to 0.956. Sorption nonlinearity is found to be a function of the polarity index of sediments natural organic matter (NOM) with a high correlative coefficient of 0.9947, suggesting that the degree of condensation of NOM, characterized by its polarity index, is correlated with the sorption behavior of 1,2,4-trichlorobenzene. In addition, the sorption affinity (Koc) of the sediments for 1,2,4-trichlorobenzene increases with decreasing of NOM polar, indicating that a higher sorption affinity in the sediments is associated with a higher degree of condensation of NOM. The Freundlich n values of chlorobenzene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene are 0.755, 0.788, 0.858, 0.949 respectively, indicating that the smaller CBs molecule may result in more significant sorption nonlinearity.