Effects of dissolved organic matters(DOMs) on the sorption and desorption behaviors of phenanthrene by sediments

The sorption and desorption behaviors of phenanthrene were investigated on two representative sediments collected from Dongjiang(D) and Liangshuihe(L) rivers,respectively,using a batch method.The effects of dissolved organic matters(DOMs) in the sediment extracts on the sorption and desorption performance were studied.The inhibitory sorption of phenanthrene was significant when using DOMs as the aqueous medium of batch experiments,in which an inverse linearity between the adsorption capacity and DOMs content was evident in the DOC concentration range used(0~110mg/L).The higher the DOC concentration was used,the stronger the inhibitory sorption of phenanthrene was identified.With the DOMs added as the medium of batch experiments a linear sorption behavior of phenanthrene on the sediments was obvious,the Kd values of which increase as the DOC concentration was diminished,while desorption hysteresis of phenanthrene could be characterized by the hysteresis indices(TII).As the initial concentration of phenanthrene increases,the TII index decreased first and then went up,which could be explained with the makeup ratios of phenanthrene molecules on the high and low adsorption sites and the extent to which they were confined inside the micropores of adsorbent.The occurrence of DOMs in the adsorption system could facilitate desorption of phenanthrene from the sediments and thus attenuate their desorption hysteresis,promoting the transport and migration ability of contaminants in the aquatic environment medium.