Occurrence Characteristics And Source Identification Of Polycyclicaromatic Hydrocarbons In Sediments Of Typical Sea Areas Of The East China Sea

As a kind of organic pollutants,polycyclic aromatic hydrocarbons(PAHs)are difficult to degrade and easily accumulate in living organisms,have attracted much attention because of the serious "three-way" risk to marine organisms and even human health.Shengsi Sea area is located in the north-south shipping channel and the Yangtze River pivot point,which is the busiest trade transportation in China.It has a superior geographical position and is a natural outer port of Shanghai port.Shengsi Sea area is also an important part of Zhoushan Fishing Ground,which is an excellent habitat for marine life such as groupers and yellow croakers,and an important breeding base for marine economic crops such as mussels;In the shipwreck area of the “SANCHI”of accidents,due to the leakage of a large amount of condensate oil and heavy fuel oil,it might affect the marine life and ecological environment of the sea area.This paper selected two special research areas in the sea area of Shengsi Sea and the “SANCHI” shipwreck,qualitatively identified the pollution source and evaluates the ecological risk of PAHs in surface sediments,which might provide basic datas and scientific basis for ecological environmental protection in the sea.In June 2017 and February 2018,surface sediment samples from the sea area of Shengsi Sea and the “SANCHI” shipwreck were collected respectively.The content of PAHs and theirs molecular composition were determined by gas chromatography-mass spectrometry.Identification of sources of PAHs based on molecular weight-to-weight ratio method,characteristic molecular ratio method and principal component analysis.The potential ecological risk of PAHs in sediments was evaluated using the quality benchmark method and the quality standard method.The main conclusions are summarized as follows:(1)Except acenaphthylene and acenaphthene,14 PAHs were detected in the surface sediments of ShengsiSea,.The total concentration of PAHs in the site ranged from 46.38 to 196.36 ng/g with an average of 109.40 ng/g.The lowest and highest total content appeared at two sites,A9 and A5,respectively.Among the 14 priority PAHs detected,the content of phenanthrene was the highest(17.18 ~ 67.66 ng/g),followed by fluoranthene,the content was between 5.38 and 37.93 ng / g,and the dibenz[a,h]anthracene content was the lowest.The concentration is 0.01~0.71 ng/g.Among the 14 PAHs detected,3 rings and 4 rings were dominant,accounting for 71.21% of the total.The percentage composition of different ring numbers PAHs is: 3 rings > 4 rings > 5 rings > 2 rings > 6 rings.The spatial distribution characteristics show that the distribution of PAHs in the surface sediments of the Shengsi Sea area shows an increasing trend of offshore distance and decreasing content,indicating that land-source pollution is the main source of PAHs in this area.(2)In addition to Chrysene,benzo[a]pyrene and dibenz[a,h]anthracene,13 other PAHs in surface sediments of various sites in the "SANCHI " shipwreck area were detected in different degrees.The total content was between 26.70~227.11 ng/g,with an average of 107.05 ng/g.The highest component is indeno[1,2,3-cd]pyrene,followed by benzo[k]fluoranthene and benzo[b]fluoranthene.The PAHs detected were mainly high-rings.The PAHs content of 5 and 6 rings accounted for 76.02% and 12.73% of the total content of PAHs,respectively.The proportion of PAHs in 2,3 and 4 rings in the total content was 0.91%,3.84% and 6.50%.The contribution of different ring number PAHs to the total content of PAHs is from large to small: 5 rings > 6 rings > 4 rings > 3 rings > 2 rings.From the perspective of spatial distribution characteristics,Affected by the shipwreck accident,the distribution trend of the PAHs content is radiated outward by the shipwreck point.(3)Analysis and identification of PAHs pollution sources: The molecular weight method has found that the PAHs in the Shengsi Sea area are mainly from fossil fuel combustion.Further analysis found that in the sites of petroleum sources,except for the proportion of low-ring PAHs,the high-ring PAHs molecules are as high as 40%,indicating that there are some pyrolysis sources in PAHs at these sites,so the surface sediments in the Shengsi Sea area.The source of PAHs pollution might be a mixture of oil leakage and combustion.The PAHs in the surface sediments of the “SANCHI” shipwreck sea area were greatly affected by the burning of fossil fuels;The study of characteristic molecular ratio method found that PAHs pollution in the study area mainly came from coal,wood,grass and gasoline,diesel and other combustion sources and mixed sources,while oil sources contributed less.The PAHs pollution in the surface sediments of the “SANCHI” shipwreck sea area is mainly affected by natural gas,diesel oil and petroleum combustion sources.;Principal component analysis showed that the PAHs in the sediments of the ShengsiSea area were mainly affected by combustion sources and mixed sources such as coal,natural gas,diesel and petroleum,and the oil leakage was less polluted.The source of PAHs pollution in the surface sediments around the shipwreck of the “SANCHI” ship indicates that most of the PAHs pollution in the surface sediments of the sea area comes from high-temperature combustion of fuel,accompanied by partial fuel leakage,so The PAHs pollution of thethe “SANCHI” shipwreck sea area mainly comes from the mixed source of high temperature combustion.(4)The potential ecological risk level of PAHs in sediments: The content of PAHs in the surface sediments of the sea area and the shipwreck of the “SANCHI” was at a low-level pollution level.The results of ecological evaluation showed that the PAHs in the surface sediments of the Shengsi Sea area did not exceed the low ecological effect.The potential ecological risk of PAHs in the surface sediments of this area was small,but it was necessary to strengthen the monitoring of the sea area in the marine special protection area.The PAHs in the surface sediments of the "SANCHI " shipwreck sea area have less adverse effects on marine life,but due to the occurrence of the collision accident,it is necessary to strengthen monitoring and speed up the cleaning,which will minimize the damage.(5)The results of pollution characteristics show that the PAHs in the surface sediments of the Shengsi Sea area are dominated by the middle and high rings,while the " SANCHI " Wheel is dominated by the high rings.The difference in content between the two is small,indicating that the " SANCHI " wheel collision incident may be the reason for the large difference in pollutant composition in the sea area..Compared with the PAHs pollution characteristics in surface sediments of other areas,the PAHs content in the surface sediments of the Shengsi Sea is generally at a lower pollution level.The anthropogenic source is the main source of pollution.By actively carrying out industrial pollution control and optimization in cities such as Jiangsu,Zhejiang and Shanghai.Measures such as urban energy structure and control of coal use by residents ensure that PAHs in surface sediments of the Shengsi Sea are at a lower pollution level.The content of PAHs in the surface sediments of the “SANCHI” shipwreck is also at a low pollution level.Relevant departments can take appropriate measures to repair the surface sediments in the sea area surrounding the shipwreck of the “SANCHI” ship.