| Endocrine Disrupting Chemicals (EDCs) pollution has become a global environmental issue after ozone depletion and greenhouse effect. EDCs are defined as exogenous substances that not directly as toxic substances to bring any abnormal impact on organism, but they can imitate and disturb the physiological and biochemical action of natural hormone by interfering with their synthesis, secretion, transportation or clearance in the body, it will finally result in disastrous consequences to species and ecological environment. The EDCs has emerged as a hot and frontier topic of environmental science in international, and our environmentalists have also organized some major projects to study EDCs in key water areas of China, however, the study on Dianchi Lake is still relatively backward. At present, the research on EDCs in Dianchi Lake is limited to pollution investigation of individual kinds of pollutants in water, such as polychlorinated biphenyls (PCBs) and phenols. Due to the restriction of analysis method, it has not yet make a systematic research of typical EDCs in Dianchi Lake, especially for the international most concerned steroid EDCs, the study of which were not deeply and widely in the other waters in China. Because of the extremely low concentration and the interference of complex matrix, it is very difficult to determine steroid EDCs in environment. In addition, the standard methods about EDCs were not established in the contemporary world. So the research of analysis technology with high sensitivity and selectivity for the determination of steroid EDCs has become one of the most important tasks for the environmentalists.In consideration of the urgency and hysteresis of study on EDCs in Dianchi Lake, steroid EDCs is selected as research object in this paper and their environmental chemical behaviors in Dianchi Lake catchment are studied on the basis of the established analysis methods. Compared with previous studies, research areas in the paper have extended to the whole Dianchi Lake catchment including 10 national surface water quality monitoring section in Dianchi Lake,22 inflow and outflow rivers, as well as 8 sewage treatment plants (STPs) in Kunming City; research media have extended to water, sewage, sediment and sludgesamples; and research contents have deepened to migration behavior, removal efficiency, pollution load, pollution characteristics and environmental fate. This paper synthetically evaluated the pollution situation and environmental risk of steroid EDCs in Dianchi Lake, with the purpose of providing scientific basis for making treatment countermeasures of those pollutants.The analysis methods for the determination of four typical steroid EDCs, such as estrone (El),17-p-Estradiol (E2), estriol (E3) and 17-a-ethynylestradoil (EE2) in complicated environmental have been established. The results show that N,O-bis (trimethylsilyl)trifluoroacetamide (BSTFA) (Fluka 15243) was choosed as the optimal derivatization reagent under the condition of without heating and catalyst, and the best results were obtained when react at room temperature (20℃) for 10 min. Compared to the international commonly used derivatization method, this method solved the bottleneck problem of steroid EDCs determination with gas chromatography-mass spectrometry (GC-MS) by simplifying experimental operation and decreasing experimental time.A series of sample pretreatment methods were selected and optimized according to different kinds of environmental samples, and Gel Permeation Chromatography (GPC) was used to the purification of sewage, sludge and sediment samples. The analysis methods for the determination of steroid EDCs in surface water (such as river water and lake water), sediment, STPs influent, effluent and sludge were established with the detection limit to ng/L or ng/g level, recovery higher than 80%, and RSD lower than 10%. It satisfied the demands of environmental sample analysis and provided technological means for the comprehensive study of their environmental chemical behaviors in Dianchi Lake, besides that, it was also offered technical support for the relative research on other water areas.On the basis of the analysis of influent, effluent and sludge of Kunming main eight STPs, the discharge amount of steroid EDCs in influent were calculated, the removal efficiencies with different treatment processes in those STPs were evaluated, the environmental fate of steroid EDCs in STPs were investigated. Moreover, the pollution loads of effluent and sludge to environment were estimated. The results show that the high concentration of E1, E2, EE2 and E3 were detected in influent samples of all STPs with the total concentration of 146.96～230.47 ng/L. Additionally, the amount of steroid EDCs that enter those STPs was 190 g/d. There were great differences on removal efficiency among the STPs due to their different treatment processes or technical parameters. The best removal efficiency was obtained in the fourth STP adopted 3AMBR process with the removal rate of more than 88%. Biochemical degradation was the main removal way of steroid EDCs, and there was little removed by the adsorption on sludge. The total amount of steroid EDCs that discharged into water environment via STPs effluent was 39.57 g/d.The pollution characteristics of steroid EDCs in Dianchi Lake 22 main surround rivers were illustrated. The migration behavior of steroid EDCs in river was studied by the analysis of 11 sampling point of water from Panlong River. At last, the pollution loads of inflow rivers to Dianchi Lake were estimated. The results show that steroid EDCs were detected in water and surface sediment samples of all the rivers and the most serious were the ones in the north of Dianchi Lake that flow through Kunming main city zone.The water samples of Panlong River from Songhuaba reservoir to Dianchi Lake were analyzed combining with the effluents of the second, fourth and fifth STPs. The concentrations of steroid EDCs were lower upstream Panlong River, but middle reaches of which were serious polluted because of the discharge of STPs effluent and sewage. Due to the water self-purification, the pollution of middle and lower reaches was relieved; however, the concentrations of steroid EDCs in downstream were significantly increased again for effluent discharge from the second STP. The steroid EDCs in Dianchi Lake were mainly originated from the rivers in north, in which the maximum discharge amount was Panlong River with 5.84 kg/a. The total amount of steroid EDCs and EEQ amount that discharged into Dianchi Lake by those inflow rivers were 23.85 kg/a and 12.65 kg/a.Water and surface sediment samples of ten national surface water quality monitoring section from Dianchi Lake were analyzed in order to study the pollution characteristics of steroid EDCs in Dianchi Lake, and further to investigate their environmental fate. The results show that steroid EDCs were detected in all water samples of Dianchi Lake and the total concentration range from 5.53 to 39.00 ng/L, which was higher than the exposure concentration that can interfere the growth and development of aquatic organisms. Of all sampling points, the highest total concentrations of steroid EDCs were detected in Diaoqiao (39.00 ng/L) and Huiwan Zhong (21.79 ng/L), secondly was Dianchi Nan. As for the other sampling points, there had little difference in the concentrations of steroid EDCs. The total contents of steroid EDCs in sediment samples were 2.59～15.68 ng/g in which the major pollutants were El and E2, and the average conten was 8.87 ng/g. Because the photolysis and biodegradation were slow, the steroid EDCs discharged into Dianchi Lake have accumulated in the water and sediment, as well as amplified in organism by food chain, except some of which were discharge from Dianchi Lake via Haikou River and Xiyuan tunnel.In summary, steroid EDCs were ubiquitous contaminants in Dianchi Lake and mainly come from the inflow rivers, whose sources were effluent discharge of Kunming eight STPs because steroid EDCs can not be completely removed in those STPs. Further works will be planned to deeply study the biological effects of typical aquatic organisms of Dianchi Lake caused by steroid EDCs, as well as their potential adverse effects and environmental risk, on the base of which, reasonable and feasible treatment countermeasures should be explored. |
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