| In recent years,with the rapid development of economy,industrialization and urbanization,the pollution of urban streams has been becoming ever more serious.A variety of pollutants flow into urban streams and it is challenging to remade the streams with a mixture of pollutants.It is urgent to analyze ecological risks of the streams and identify the key toxic contributors,which are the purposes of this thesis.To conduct ecological risk assessment for urban streams,chemical analysis and biological testing are needed,and both analyses require effective water sampling methods.Traditional active sampling methods were time and labor-intensive,and it only provided instantaneous water concentrations,which were difficult to reflect the pollution of surface water in a period of time.Meanwhile,the exhaustive extraction ignored the bioavailability and may overestimate the toxicity of pollutants.On the other hand,passive sampling methods are cumulative sampling,saving time and effort.In addition,the methods provided average water concentrations over a period of time,which well simulated the exposure of organisms in aquatic environment at low dose for a long time.At present,passive sampling methods were mostly used for hydrophobic compounds in aquatic environment,while polar organics were rarely studied.The POCIS was designed as a passive sampling device for polar organics.Solid phase adsorbents of POCIS would affect the efficiency of sampling,thus it is necessary to develop adsorbents which worked for chemicals with a wide range of polarity in order to effectively reveal the main toxicants in a mixture of pollutants.Accordingly,a solid phase extraction adsorbent was developed in the laboratory.In this thesis,the synthesized adsorbent was used for passive sampling adsorbents for aquatic risk assessments along the combination of chemical analysis and biological tests using zebrafish embryos.Aquatic risk and main toxicants were analyzed at the selected sampling sites of Guangzhou streams and a typical sewage treatment plant.First,the adsorbent for passive sampling was synthesized according to a previously developed method in the laboratory.The affinity of the absorbent to various compounds with a wide range of polarity(log Kow:-0.13 to 8.15)was verified,and the toxicity of the clean adsorbent was also assessed.Results showed that the recovery of the 47 target compounds was29.2%132%,with only 6 compounds having a recovery less than 50%.In summary,the synthesized adsorbents had good a adsorption capacity for compounds with wide polarity,and could be used as passive sampling adsorbent in waterbody with a mixture of pollutants.The results showed that the embryos exposed to the control samples were 100%normal,and the embryos in the clean synthetic adsorbent group had 2.78%mortality and abnormality,which suggested that the synthetic adsorbent can be used for biological testing.Secondly,water samples were collected from Guangzhou urban streams using POCIS with the synthetic adsorbent,and the toxicity of adsorbent elutes to zebrafish embryos was tested.Meanwhile,contaminants in the samples were also analyzed.Aquatic risk in urban streams was then assessed by incorporating exposure and effect information.As shown by the result of chemical analysis,the concentrations of neonicotinoid and organochlorine pesticides,polycyclic aromatic hydrocarbons and synthetic musks were found with relatively high concentrations in most samples from Guangzhou urban streams,while organophosphate pesticides were also detected at some sites.Compared with active sampling,the results of POCIS reflected exposure within a period of time,and passive sampling was more sensitive.Therefore,in some cases,POCIS and active sampling served as complementary means.In terms of biological tests,some sites showed high toxicity to zebrafish embryos.Abnormality at site S7?Haizhu stream?,S9?Sha stream?and S10?Nantai stream?was 52.8%,61.1%and 50.0%,respectively.Compared with other sites,S7,S9 and S10 which locate in the downstream of the west Pearl River waterway in Liwan District showed higher toxicity than other sites.Overall,the spatial distribution of organochlorines were significantly correlated with the biological effects in zebrafish embryos,suggesting that organochlorines may be one of the contributors to the toxicity of zebrafish embryos.Spatially,there was relatively high aquatic risk in the downstream of the west Pearl River.Finally,to evaluate the effectiveness of sewage treatment plants for different organic pollutants,the POCIS with synthetic adsorbent was deployed at different stages in a sewage treatment plant.The elutes of the adsorbent was tested for zebrafish embryo toxicity and chemicals,and aquatic risk was assessed using exposure and effect data.It was found that chemical profiles in the sewage treatment plant were similar to those in the urban streams.The efficiency of treatment was quite poor for neonicotinoids,synthetic musks,and most PCBs,while the concentrations of sulfonamide antibiotics,some organochlorines,pyrethroids,polycyclic aromatic hydrocarbons and some PCBs were greatly reduced after the treatment.In addition,the levels of organophosphate and phenylpyrazole pesticides in the sewages were low.Toxicity tests showed that the toxicity of water samples to fish embryos gradually decreased from the sedimentation pond to the outlet,and the toxicity of the effluent from the sewage treatment plant was lower than the toxicity of water samples from most stream sites.With the degradation of organic compounds in the sewage treatment plants,the toxicity gradually decreased,and the reduction was the most obvious in the anaerobic and anoxic pools.Consistent with the results in the streams,the distribution of organochlorines was related to the results of biological tests,implying partial contribution to the toxicity to zebrafish embryos.There may be other toxicity contributors and they were difficult to be identified as the limited selections of test organisms and target analytes,calling for effect-directed analysis to identify non-target compounds. |
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