Study On The Pollution Characteristics Of New Pollutants Such As Phthalates And Their Toxic Effects On Zebrafis

Phthalic acid esters,PAEs,are typical endocrine disruptors.They are widely used as plastics modification additives in the production of pesticides,coatings,printing and dyeing,cosmetics,and fragrances.PAEs are easy to migrate from plastic contact materials in the process of production or transportation and are not easily decomposed for a long time.They not only have liver toxicity,growth and development toxicity,reproductive toxicity,etc.,but also have carcinogenic risks,among which,phthalate(di（2-ethylhexyl）phthalate（DEHP）in PAEs has been detected in many water bodies at home and abroad,and the concentration of DEHP in many water bodies exceeds the limit specified in the Environmental Quality Standards for Surface Water（GB3838-2002）.Therefore,its health hazard should be paid great attention.Our research group had investigated Hongfeng Reservoir,a drinking water source protection area in Guiyang,Guizhou Province,and found that the content of DEHP in the reservoir exceeded the standard.Therefore,DEHP was selected as the target pollutant,and the measured value was used as a reference to investigate the toxic effect of DEHP exposure with zebrafish as the model organism.The potential toxic effects of DEHP were investigated using biological methods such as reproductive morphological indexes,enzyme activity,histopathology and intestinal microflora to provide theoretical basis for the ecological and health risks of PAEs pollutants.The main conclusions are as follows:（1）Study on PAEs pollution level,human health risk and ecological risk in Hongfeng Reservoir.The components to be measured in surface water samples were extracted by liquid-liquid extraction,and 16 kinds of PAEs were detected by gas chromatography-mass spectrometry（GC-MS）.The results showed that 11 of the 16species of PAEs were detected,and the distribution of∑11PAEs concentration at each sampling site was as follows:Pianshanzhai>Huayudong>Houwu>Daba>Sanchahe>Xijiao waterworks>Yaodong.The concentration of∑11PAEs at each monitoring site ranged from 975.14 to 18917.07 ng/L.The average concentration of PAEs detected by11 species showed the highest DEHP（4416.80 ng/L）,and the DEHP content at Houwu,Huayudong and Pianshanzhai sampling sites was 8.95μg/L,9.24μg/L and 9.38μg/L,respectively.All of them exceeded the limit value of 8.0μg/L stipulated in China’s"Surface water Environmental Quality Standard"（GB3838-2002）.The health risk assessment model of the United States Environmental Protection Agency（US EPA）was used to evaluate the human health risk of PAEs in Hongfeng Reservoir.The health risk value of DEHP for males and females in Hongfeng Reservoir was greater than the limit value(1.0（39）10^-6)of carcinogenic risk value of pollutants prescribed by US EPA.The ecological Risk assessment results using Risk entropy（RQ）method showed that the highest RQ value of DEHP was over 70,and the potential risk was the greatest.The safety threshold method showed that the safety threshold of DEHP is 4.41>1,indicating that the exposure concentration of DEHP had potential harm to the reservoir.（2）Through the study on the reproductive morphological indexes of male and female zebrafish,it was found that there was no significant change in the fatness（k）of male and female zebrafish,while the liver index（HSI）and gonad index（GSI）of male and female zebrafish were significantly changed（p<0.05）.These results indicated that DEHP stress may have certain effects on liver and gonad（testis/ovaries）tissue of zebrafish.（3）The enzyme activity study showed that MDA content in the testis of male fish showed a"stepwise rise"trend.Compared with CK control group,MDA content in the gut of female fish was significantly decreased in other groups（p<0.01）,and was the lowest at 1.0 mg/L.（4）Histopathological studies showed that DEHP exposure could delay the development of male zebrafish’s testis,and the influence on the development of male zebrafish’s testis was most obvious when DEHP stress concentration was 1.0 mg/L.In female fish,oocyte ripening was observed,and the higher the concentration was,the more obvious it was.When DEHP stress concentration was 1.0 mg/L,it had the most obvious effect on the intestinal tract of female fish,with large area vacuole and cell necrosis,but had no obvious effect on male fish,which was consistent with the results of enzyme activity studies.（5）The study on microbial diversity of zebrafish intestinal contents through microbial 16S r RNA sequencing found that DEHP could change the intestinal microbial diversity of Zebrafish,and when the DEHP stress concentration of zebrafish increased,the Cetobacterium in the body would increase accordingly to resist the attack of pollutants.