| The five rivers with unconventional water sources supply,including the Chaobai River(one of the five largest tributaries of the Haihe River)and four urban rivers with water recharge from sewage treatment plants in Beijing(the Qinghe River,the Liangmahe River,the Beixiaohe River and the Liangshuihe River),were selected as study waters in the Haihe River basin in May 2017 and May 2018.The chironomid larvae and a species of snail,Bellamya aeruginosa were collected for biomarker determination and transcriptome sequencing and chemical pollution concentration of sediment samples was analyzed in the five study areas.With the combination of physical,chemical and biological monitoring,the toxic effects of the tested organisms were evaluated and the mechanism of toxicity was identified with transcriptome sequencing techniques.The main results are as follows:1)Analysis of chemical pollutants in surface sediments of four urban rivers with typical water recharge from sewage treatment plants in Beijing.In 12 sampling sites,the highest concentrations of Polycyclic Aromatic Hydrocarbons(PAHs),Phthalic Acid Ester(PAEs)and Endocrine Disrupting Chemicals(EDCs)was observed in the upstream of Beixiaohe with typical water recharge from sewage treatment plant,with concentration of ?18PAHs reached 1013 ng/g.The concentration of the three pollutants showed a decreasing trend from the upstream to sampling points of water recharge outlet and then to the downstream sampling points in each river.These results indicate that the discharge of water from the sewage plant played a dilution role in chemical pollutants of surface sediments of four urban rivers.2)Biomarkers and IBRv2 index analysis of benthic invertebrate samples of river reach supplied by the discharged water from sewage treatment plants.The significant spatial distribution differences were found of six biomarkers levels in benthos samples,and the biomarkers levels were significantly correlated with pollutants concentration in sediments.Except for the Qinghe with water recharge reach from sewage treatment plant in 2018,the enzyme activity related to antioxidant defense system was activated in the river where the water discharged from four sewage treatment plants in both years.According to IBRv2,the severity of the impact in sampling sites in 2017 ranked as: upstream of the Beixiaohe River > upstream of Xiaohongmen > outlet of the Beixiaohe River > upstream of Xiaohongmen > outlet of Xiaohongmen > outlet of Jiuxianqiao > downstream of Beixiaohe > downstream of Xiaohongmen > downstream of Jiuxianqiao.The IBRv2 in study region in 2018 is basically the same trend as that of 2017.These findings indicate that pollution is more serious in the upstream than that in the downstream,which may be related to the replenishment of intermediate water in the downstream.3)Transcriptome sequencing analysis of benthic invertebrate of the river reach replenished by intermediate water from four major sewage treatment plants.In this study,a large number of differentially expressed genes were obtained using RNA-SEQ sequencing technology.Furthermore,our results indicates that some of the runoff pollution affected multiple signaling pathways of the oxidation in chironomid larvae and Bellamya aeruginosa including cell cycle,apoptosis signaling pathway,p53 signaling pathway,oxidative phosphorylation.These signaling pathways were closely related to DNA damage,carcinogenesis and cell metabolism.Additionally,the annotation rate of transcript obtained from benthic transcriptome sequencing was low through comparing and annotating the assembled transcript sequences.4)Chemical analysis of surface sediments in the Chaobai River.In 2017 and 2018,the highest PAHs content of the sediment sampling sites was occurred at Daliopo of downstream agricultural area,with a value of 411.25ng/g and 482.38 ng/g,;The lowest content of thatwas found in the Shuiquanyu of the upstream mountainous area,with a value of 69.66 ng/g and 67.22 ng/g.Similarly,the highest concentrations of PAEs in the two years was monitored in Manshuiqiao of downstream agricultural area,with a value of 2961.5 ng/g and 12194.1ng/g,and the lowest content of that was found in the Shuiquanyu of the upstream mountainous area,with a value of 1017.1 ng/g and 2713.16 ng/g..The spatial patterns in content of EDCs exhibited agreement with the PAHs and PAEs results,with more serious pollution level in downstream agricultural areas than that in upstream mountainous areas.5)Biomarkers and IBRv2 analysis of benthic invertebrate chironomid larvae from the Chaobai River.The responses of the biomarkers of chironomid larvae in different sampling sites showed great differences.ACh E activity of chironomid larvae showed a high level in the five sampling sites of urban and agricultural areas.Similarly,the activities of CAT,SOD,GST and other enzymes in the five sampling sites significantly increased,indicating that the biological function of oxidative stress was stimulated by exogenous pollutants.According to IBRv2,the severity of the impact in sampling sites in 2017 and 2018 ranked as: Daliupo > Manshuiqiao > Houduli > Baimiao village > Wanfuxin village > Gubeikou > Shuiquanyu.These findings demonstrated that pollutantion concentration and ecological risks increase in downstream sediments for the inflow from unconventional water sources supply.In this study,the number of unigenes in disease-related signaling pathways was the largest,mainly including viral myocarditis which are related to disease occurrence,cell apoptosis and cell ion exchange.Secondly,it contained related metabolic system pathways,including citric acid cycle,protein processing in endoplasmic reticulum,glycolysis/gluconeogenesis,oxidative phosphorylation,etc.By sorting out the KEGG signaling pathways,metabolic signaling pathways reduced and signaling pathways such as oxidative damage,inflammatory response and cancer effect gradually increased from the upstream to downstream sampling sites,the transcriptome results could well validate for chemical analysis and biomarker analysis.In summary,unconventional water sources supply has a diluting effect of pollution on chemical pollutants of surface sediments of four urban rivers with serious chemical pollutants lever,while having an aggravating influence of pollution on the less polluted Chaobai River;These results suggest that there are difference in the influence of unconventional water supply on the received river or reach with different degree of pollution.The biomarkers of chironomid larvae and Bellamya aeruginosa are highly sensitive to the pollutants change and was promising and reliable for evaluate the ecological risk of persistent pollutants in surface sediment of aquatic ecosystem. |
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