Screening Analysis Of Riverine Organic Pollutants And The Adsorption And Desorption Behaviors Of Phenanthrene Onto The Sediments In East River Basin

East River is one of three major river systems in the Pearl River Basin, located in Guangdong Province by the Middle Eastern region. It has a subtropical climate with, the seasonal variation. In addition to provide water for production and livings for the local residents, it is also charged with the task of water supply to the basin outside including several industrialized cities such as Shenzhen and Hongkong. With the booming economy and the acceleration of urbanization in the East River Basin in recent years, huge amounts of industrial wastewater and the surrounding sewages are poured directly into the river, together with the nonpoint source pollutions from agriculture and large transportation vessels, making the river basin facing serious environmental pollution threats.In this thesis screening analysis of organic pollutants in the riverine waters from East river basin in Guangdong province has been carried out, together with the monitoring of other water quality indices as pH, Temperature, Dissolved Oxygen, ORP, Conductivity, Salinity, Cl^-, NH₄⁺-N, NO₃^--N, etc. The types and content level of organic pollutants in the suspended solids, and sediments are also investigated in order to get a basic understanding of the organic pollutions in the region. Taken phenanthrene as an example of Polycyclic aromatic hydrocarbons (PAHs), the adsorption and desorption behaviors of PAHs on the sediments collected from both East river basin and Liangshui river have been studied, and the effects of the dissolved organic matters (DOMs) on the adsorption and desorption hysteresis of phenanthrene are discussed.Analysis of organic pollutants in both the riverine water and wastewater samples collected from East river basin in Guangdong province show that 26 species in total are detected in the 61 riverine water samples, in which 7 of them belong to the priority pollutants, while for the 6 discharging-port wastewater samples there exsist 44 organic substances, in which 6 priority pollutants and 18 species with larger toxicity are included. Specifically, in the discharging port of No. 23, all the 44 organic compounds are found to be present in the wastewater, indicating a serious pollution in that region. For the sediment samples collected in East River Basin, 25 organic pollutants are detected and 10 of them with priority, while in the suspended solids 29 organic contaminants are found and 11 species belong to the priority pollutants. Among lots of mixed organic pollutants detected in the aquatic environmental systems in East river basin, polycyclic aromatic hydrocarbons (PAHs), alkanes, olefins, benzene, phthalate esters, nitrogen heterocycles, etc. are found to be the main contaminant types.The results for batch experiments of phenanthrene adsorption and desorption on the two sediments of both Dongjiang and Liangshui rivers show that the inhibitory sorption of phenanthrene on the sediments is significant when using DOMs as the aqueous medium of batch experiments, in which an inverse linearity between the adsorption capacity and DOMs content is evident with the correlation coefficients of rD=-0.99873 and rL = -0.9987, respectively, in the range of the DOC concentration used(0～110mg/L). The higher the DOC concentration is used, the stronger the inhibitory sorption of phenanthrene is identified. With the DOMs added as the medium of batch experiments a linear sorption behavior of phenanthrene on the sediments is obvious, the Kd values of which increase as the DOC concentration is diminished, while desorption hysteresis of phenanthrene was,however,found to be universal for the two sediments, which can be characterized by the hysteresis indices(Tâ…¡). As the initial concentration of phenanthrene increases,the TII index decreases first and then goes up,which can be explained with the makeup ratios of phenanthrene molecules on the high and low adsorption sites and the extent to which they are confined inside the micropores of the adsorbent. It is therefore concluded that the occurrence of DOMs in the adsorption system can facilitate the 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.