Interactive effects of 1,4-dichlorobenzene and heavy metals on their sorption behaviors in two Chinese soils.

Organic contaminants and toxic heavy metals often coexist in contaminated soils. However, little information concerning the interactive effects of organic contaminants and heavy metals on their sorption behaviors on soils is available. In this study, the competitive sorption effects of 1,4-dichlorobenzene (1,4-DCB) and typical heavy metals, cadmium (Cd) and copper (Cu), on their sorption characteristics on two Chinese soils were examined using a batch equilibration method. The results indicated that the coexistence of Cd and Cu inhibited the sorption of 1,4-DCB on soils and the inhibitive effects increased with increasing concentrations of Cd and Cu. This can be attributed to the inner-sphere complexation of Cd and Cu to form hydration shells of dense water that directly compete for surface sorption sites with 1,4-DCB. Additionally, pore blockage is presumed to be an alternative mechanism for the inhibitive effect. The extent of inhibitive effects depends on not only the relatively chemical characteristics of metals but also on the types of soils. However, the concurrence of 1,4-DCB (50 mg/L) in soils has little effects on the sorption capacity of Cd and Cu due to their higher sorption affinity for the soils than 1,4-DCB. These findings indicated that the coexistence of metals can greatly affect sorption behaviors of hydrophobic organic compounds on soils and thus their fate, transportation, and bioavailability.