| Antibiotics are widely used in medical treatment,livestock and poultry breeding,aquaculture and other fields because of their good clinical therapeutic effect and promoting body growth.However,the excessive use of antibiotics will lead to antibiotics and their metabolites can eventually flow into the river basin through domestic sewage,industrial wastewater and other ways.Because antibiotics are highly soluble and difficult to degrade,they can remain and accumulate in the basin for a long time,and the basin becomes the final destination of antibiotics.Antibiotics in the basin can cause harm to the microbial community and aquatic organisms,improve the drug resistance of bacteria,and eventually bring risks to the ecology and human health.This study investigated 26 antibiotics of five classifications in surface water and sediment samples at 23 sites in wet season and dry season of Fenhe River.The distribution,partitioning,fate and seasonal variation of antibiotics were studied,and the spatial-temporal characteristics of pollution sources were also analyzed quantitatively.Finally,the ecological risk was evaluated and the risk sources were further revealed.The main conclusions were as follows:The content of antibiotics in water and sediment of Fenhe River was higher in dry season than that in wet season.In wet season,21 antibiotics were detected in water,with the total concentration range of 113.8-1106.0ng/l,and 15 antibiotics were detected in sediment,with the content range of 25.11-73.22 μg/kg.In dry season,25 antibiotics were detected in water,with the concentration range of 130.41-1614.88ng/L,and 17 were detected in sediment,with the content range of 12 0.98-426.2μg/kg.SAs were the main species in water of wet season and dry season.But in sediment,SAs were the main species in wet season,while CAs were the main species in dry season.Spatially,the concentrations of antibiotics were the highest in the middle stream in the wet season and dry season.However,in the sediment,the concentrations of antibiotics were the highest in the down stream in wet season,but they were the highest in the middle stream in dry season.As far as the partitioning coefficients(Kp),it was higher in dry season than that in wet season.The range of Kp was 15.9-16687 L/kg in wet season and 17.4-16106 L/kg in dry season.Due to the influence of climate and water conservancy conditions,the spatial distribution of Kp was very different.In wet season,the Kp of some antibiotics was lower in the middle stream,and higher in the lower stream,but opposite in dry season.By calculating the partition coefficient of water-suspended and suspendedsedimentary,the results showed that the migration path of antibiotics in the basin was that antibiotics will eventually enter the sediment through suspended matter when they enter the water.The migration trend of most antibiotics to suspended matter in dry season is weaker than that in wet season.Through the correlation analysis,it was found that there was a significant correlation between Kp and water temperature,water conservancy conditions,nutrient content in water,p H of sediment and sediment particle size distribution,which can be used to establish the accurate prediction model of Kp.The source apportionment results based on positive matrix factorization(PMF)model showed that antibiotics in Fenhe River Basin mainly came from livestock and poultry breeding,aquaculture,sewage treatment plant,domestic sewage and medical wastewater.In addition,farmland drainage was also one of the main pollution sources in wet season.In wet season,antibiotics mainly came from medical wastewater,accounting for 40.2%.While in dry season,antibiotics mainly came from aquaculture,accounting for 33.0%.In terms of spatial distribution,the upstream area was dominated by medical wastewater in wet season and dry season,while the sources in the middle and downstream areas were more complex.In wet season,the main sources in the middle and downstream are wastewater treatment plants,medical wastewater and aquaculture,while in dry season,the main sources in the middle and downstream were aquaculture,domestic wastewater and medical wastewater.The sources of antibiotics in the tributaries were different.Yangxing River was mainly from livestock and poultry breeding and aquaculture,while Taiyu channel was mainly from domestic sewage.The results of ecological risk assessment based on assessment factor(AF)method showed that antibiotics in Fenhe River was medium risk level in wet season and dry season.In terms of specific antibiotic substances,sulfamethoxazole and roxithromycin were the high risk level in wet season and dry season,while the five antibiotic substances of QNs were the medium risk level.In addition,tetracycline in wet season and sulfadiazine,thiamphenicol,clarithromycin in dry season also were the medium risk level.In terms of spatial distribution,the upper stream of the main stream were low risk in dry season and wet season,while the risk in the middle and lower stream of the main stream,tributaries were different in dry season and wet season.In dry season,Yangxing River was the high risk area,while other areas were medium risk area.In wet season,78% of the areas were medium risk area,but there were no high risk area.As the source-specific risk,there was no high risk source of antibiotics in wet season and dry season.In wet season,medical wastewater was the medium risk source,while in dry season,aquaculture and domestic sewage were the medium risk source.Based on the investigation of aquatic organisms in Fenhe River Basin,the standard values of antibiotics obtained by SSD method were generally higher,which were 10-100 times higher than those determined by AF method.Compared with AF method,SSD method takes into account the local aquatic organisms and integrates the species of multiple nutrient levels,and selects 95% of the species to be protected.The process of obtaining the baseline value by SSD was more scientific and holistic.Based on this,the risk assessment results showed that only norfloxacin and trimethoprim were low risk level in wet season and dry season,while other substances did not reach risk level.In terms of spatial distribution,52% of the areas in wet season and dry season were the low risk level area,which mainly distributed in the Yangxing River,the tributaries of Taiyu canal and the areas in the middle stream of Qixian County.In summary,antibiotic pollution in Fenhe River Basin was at a medium to high level,mainly distributed in the midstream and downstream of mainstream,and some tributaries such as Yangxing River and Taiyu backwater channel.The antibiotics could cause risks to the ecological environment.Among all the antibiotics,sulfamethoxazole and roxithromycin were the two main risk substances.In the view of sources,aquaculture,livestock and poultry breeding and domestic sewage were the three main risk sources.This research could provide technical support for antibiotic management in Fenhe River Basin. |
PDF Full Text Request