The Research Of Pollution Status And Ecological Risk About Microplastics And Three POPs In Zhanjiang Mangroves,China

In order to detect the contents,distribution patterns and possible sources of three persistent organic pollutants?PAHs,PBDEs and PCBs?,surface sediment samples collected from 12different sites were investigated in Zhanjiang Mangrove NNR,a largest natural mangrove forest in China,covering the area of five cities.In addition,microplastics was also analyzed to evaluate the co-relationship with the above organic pollutants,ecological risk and environmental driven factors in mangrove coast ecosystem were conducted in this study.The main conclusions are as follows:?1?The abundance of microplastics in Zhanjiang mangrove sediments varies between 108n/kg to 486 n/kg.The average value is 333±127.60 n/kg.A size spectrum of 200-500?m of microplastics accounts for the highest proportion?29.73%?,while fibrous type is dominant which accounts for61.57%,and both hyaline and red particulates are most common.Microscopic infrared results showed that PE?59.87%?is the major component,which accounts for half proportion,followed by PP?26.32%?,Rayon?10.53%?,and Polyester?5.26%?.The sources of microplastics in the sediments mainly come from fisheries and rivers.?2?A total of fourteen homologues of PBDEs were identified.The content of PBDEs ranged from 2.26 to 67.91 ng/g?mean value:23.32±18.18 ng/g?,and the highest value existed in Zhanjiang urban district.Among 14 homologues,penta-BDE and deca-BDE are in higher risks,while Nona-BDE is in medium risk which should be paid more attention on.Most studied sites are evaluated as"high risk",except two sites,ZJ₁ and ZJ₁₀,with"medium risk".?3?Sixteen strictly-controlled PAHs by the US EPA were detected,which ranged from249.00 to 1079.84 ng/g with the mean value of 494.30±259.33 ng/g.The results of the homologous ratio method indicated that the main sources of PAHs come from combustion of petroleum products,and also plants and coal.Based on the sediment quality guidelines?SQGs?proposed by Canada EPA,the probability of PAHs in sediments is less than 10%with low ecological risk.The criteria of sediment quality standards showed that Flu had a moderate ecological risk.Overall,the ecological risk of PAHs in Zhanjiang mangrove sediments is lower.?4?A total of eleven PCBs compounds were detected in Zhanjiang mangrove forest.The concentration ranged from 0 to 18.30 ng/g,with an average of 5.89 ng/g.The content of PCBs meets the first standard of my country's marine sediment quality standards.SQGs analysis shows that ecological risk of PCBs has no risk.?5?Redundancy Analysis?RDA?showed that microplastics are positively correlated with PBDEs significantly,indicating their similar sources,or microplastics could be regarded as vectors of PBDEs into the sediment.Similarly,a significant positive correlation is also found between PAHs and rainfall or TOC?P<0.05?,indicating that the possible source of PAHs is from atmospheric pollution deposition.What's more,the higher the organic matter is present in the sediments,the better the accumulation of PAHs does.PCBs content was positively correlated with anthropogenic factors,such as GDP,average GDP,industrial output value,gross output value of agriculture,forestry,animal husbandry and fishery,population,urbanization rate,total water use,etc.?P<0.05?,indicating that the contents of PCBs is significantly affected by human activities and socio-economic factors.Compared with other areas,the content of PBDEs,PCBs,and microplastics is at the lower middle level,and PAHs is at a higher level.Among the POPs,the ecological risk of PBDEs is relatively high.Combating the use of commercial deca-BDEs and penta-BDEs is a feasible measure to reduce the ecological risk of PBDEs.Reducing the pollution of microplastics attached to fishery and improving the treatment efficiency of village domestic wastewater in coastal areas is a way to reduce microplastic pollution.Controlling the content of microplastics can reduce the carrying of organic pollutants into sediments.