Effect of dissolved organic matter on sorption and desorption of phenanthrene onto black carbon.

Sorption and desorption of phenanthrene (PHE) onto black carbon (BC) extracted from sediments were studied in the presence of three types of dissolved organic matter (DOM), including L-phenylalanine (L-PH), peptone and citric acid. The nonlinearity of the sorption isotherms increased in the presence of DOM. The presence of L-PH reduced the sorption capacity and desorption hysteresis because of the solubilization of PHE in L-PH solution. Peptone at 50-500 mg/L also led to a decrease in sorption attributed to solubilization, although the sorbed peptone on the BC surface could slightly increase PHE sorption. Unlike L-PH and peptone, citric acid enhanced the sorption capacity and irreversibility of PHE on BC mainly due to the strong sorption of citric acid on the BC surface. Our results may help to understand the different impacts of DOM on the distribution and transport of PAH in the environment.