The Fate And Transport Of POPs In Dagu Drainage River

Rivers have been severely polluted with high loads of persistent organic pollutants(POPs) in our country. But the research about the fate and transport of POPs in river is less systematically studied, presently. The environmental transport of POPs in Dagu Drainage River(DDR) selected as a typical example is reasonedly investigated in this article.Characteristics of sediment from DDR in Tianjin are analyzed. The mean value of TOC in sediments is as high as 8%, which is in favor of sorption POPs. The particle sizes of both suspended sediment and bottom sediment are mensurated by Malven Mastersizer. Silt accounts for about 60% in mass, while clay is about 10%. Particles of sediments belong to fine granule. Suspended sediment and bottom sediment mensurated by XRD mainly consist of quartz and illite, both account for 75.5% and 62.2%, respectively. The conformation of suspended sediment is very similar to bottom sediment from SEM photo.The distribution of POPs in sediments from DDR is investigated. OCPs are analyzed by GC-MS qualitatively and GC-ECD quantificationally. The result shows that DDR is severely polluted with POPs. Mean concentrations of OCPs in surface sediments are 113.73ng/g for HCHs and 40.86ng/g for DDTs, respectively, in 2005. Concentrations of HCB residues in surface sediments are higher than other OCPs residues. Concentrations of HCB range from 17.50 ng/g to 1315ng/g (mean 240 ng/g). Obviously, HCB is chief POPs in sediments from DDR. Sediments suspended from bottom are mainly source bringing POPs into river water.Sediment erosion, sorption-desorption, sedimentation environmental behaviors that closely relate to the fate and transport of POPs are investigated. Effects of bulk density and shear stress on erosion rate are researched by hydrodynamic equipment. The erosion rate formula as function of bulk density and shear stress is regressed. Experimental data of HCB desorption were simulated better by fast-slow two stage first-order kinetics model and dynamic parameters of HCB desorption were also calculated. Sorption-desorption mathematic model is built that can illustrate variation of POPs concentrations in different media with time. The concentration of suspended sediment is main factor deciding the balance time. Through the experimental data regression, the power function about Kp and SPM is regressed. Mass settling velocity of suspended sediment through experiment is similar to the calculated value withmean particle size by one particle settling in fresh water. For rivers with lower concentration of suspended sediment, effect of concentration on settling velocity is inapparent.Based on theories of pollutants movement in river and integrated with sediment erosion, sedimentation, sorption-desorption processes, the fate and transport of POPs mathematic model is built. The calibration model is used to simulate the transport of POPs in the DDR. POPs flux into bohai gulf is 4.32 Kg/d after calculation. The model prediction results will be a powerful tool for the environmental management.