| Jinshan District is located in the far southwest suburbs of Shanghai.It is located in the south wing of the Yangtze River Delta which one of China's major economic belts,and on the southeastern end of the Taihu Lake Basin.The river network in the area is staggered and dense,with a developed freshwater aquaculture industry.Jinshan District,as one of the three major aquaculture areas in Shanghai,has more breeding ponds,especially Macrobrachium rosenbergii breeding ponds.In recent years,freshwater shrimp farming in Jinshan District has become an emerging industry for agricultural transformation and development and farmers getting rich.Macrobrachium rosenbergii,also known as Malaysian prawn,is native to the Indian Ocean,Western Pacific Islands and other regions.Macrobrachium rosenbergii has become one of the main cultured shrimps in China because of its advantages such as fast growth rate,large individuals,wide food sources,and good meat quality.According to the China Fisheries Statistics Yearbook,the output of freshwater aquatic products in Shanghai in 2018 was about94,300 tons,of which the production of Macrobrachium rosenbergii was nearly 3480tons,next to the production of Macrobrachium rosenbergii in Jiangsu,Zhejiang and Guangdong.Polycyclic aromatic hydrocarbons?PAHs?,as a common persistent organic pollutant,have a great impact on human health.Therefore,PAHs pollution is more and more concerned by the environmental field.With the increasing attention of humans on the quality of aquatic products,it is of great significance to scientifically assess the pollution levels and potential risks of polycyclic aromatic hydrocarbons?PAHs?in Macrobrachium rosenbergii and its culture.This article takes the specialty farm of Macrobrachium rosenbergii in Jinshan District of Shanghai as an example.The main research objects are PAHs in water,soil,sediments,atmospheric deposition,phytoplankton,zooplankton,suspended matter and Macrobrachium rosenbergii.The content of 16 PAHs in the organism and the surrounding culture environment was analyzed systematically during the complete culture cycle of Macrobrachium rosenbergii,and the effects of various environmental factors on the content of PAHs in Macrobrachium rosenbergii were discussed.And on this basis,the risk assessment of aquatic product edible was carried out.Finally,aquaculture suggestions are proposed based on the pollution status of PAHs and the residual situation of aquatic products,with a view to providing data support and reference for the quality assessment of aquatic products and the protection of consumers'food safety.The findings are as follows:?1?Through the study of the culture environment and the content and composition of PAHs in Macrobrachium rosenbergii,the PAHs content and sedimentation flux in the solid and aqueous phases of atmospheric sedimentation were 5.52?9.45?g/g,47.99?100.42 ng/L and 3.750?6.420?g/m2·d,83.323?174.355 ng/m2·d.The solid phase is dominated by high rings,and the water phase is dominated by low rings.Compared with other studies in Jinshan District,the results are basically the same;The content of PAHs in the water is 342.76?1520.83 ng/L,mainly low ring,high ring has a small specific gravity,and low ring PAHs account for more than 50%.Compared with other domestic breeding areas in the study area,the PAHs pollution is at a moderate level;The content of PAHs in soil and sediment is 1000.45?2138.46 ng/g and 1767.70?3656.97ng/g respectively,and the content of high-ring PAHs is much higher than that of low-ring,which is at a higher level than other farming areas;The total contents of 16kinds of PAHs of zooplankton and phytoplankton are:46.18?134.63?g/g and26.13?145.39?g/g,all of which are mainly 4-ring PAHs;The average total content of16 PAHs of Macrobrachium rosenbergii in the three growth periods of juvenile,growth and rearing periods are:63.09 ng/g,111.89 ng/g,148.77 ng/g,and the content of PAHs in the 3 and 4 ring is relatively high.Compared with other aquatic products in the aquaculture area,PAHs in Macrobrachium rosenbergii in the study area were at a low level.During the growth process of Macrobrachium rosenbergii,PAHs are more obviously enriched,with an average growth rate of 201.7%.?2?LMW/?LMW+HMW?ratio,characteristic ratio method and principal component analysis method were used to analyze the source of polycyclic aromatic hydrocarbons in aquaculture water,soil,sediment and atmospheric deposition.The analysis results show that the petroleum source and the combustion source are the main sources of atmospheric deposition PAHs in the breeding area,and the pollution source in the atmospheric deposition water phase is mainly the petroleum source,with a contribution rate of 72.54%;The pollution source in the solid phase of atmospheric deposition is mainly the combustion source of coal and wood,with a contribution rate of 67.66%,the main cause of the difference between the water and solid phase pollution sources is the low solubility of high-ring PAHs,which are mostly adsorbed on solid particles;The main source of aquaculture water pollution is petroleum,with a contribution rate of 59.75%;The main source of coal combustion in the soil around the breeding area is 63.13%;The pollution sources in the sediments of breeding ponds are similar to those in the soil,mainly coal combustion and incomplete combustion of fossil fuels,with a contribution rate of 50.41%.Due to the complex land use types in the study area,the pollution sources of polycyclic aromatic hydrocarbons are also relatively complex.?3?Analyzed the ecological risk of PAHs in the water body through the risk entropy method,and the ecological risk of the water in this area is in the middle level;The ecological risk assessment of soil and sediment was carried out using the over-standard coefficient,and it was found that the ecological risk of polycyclic aromatic hydrocarbons in the soil and sediment in the breeding area was moderate to high;Using carcinogenic equivalent concentration TEQ?Ba P?with benzo[a]pyrene?Ba P?as a reference to evaluate the carcinogenic risk of polycyclic aromatic hydrocarbons in water,soil and sediment,it was found that the carcinogenic risk of sediment was higher than that of soil.The main carcinogens in water,soil and sediment are chrysanthemum?CHR?,benzo[a]anthracene?Ba A?,benzo[b]fluoranthene?Bb F?,benzo[a]pyrene?Ba P?,and dibenzo[a,h]anthracene?DBA?and indeno[1,2,3-cd]pyrene?IPY?;The lifelong carcinogenic risk value was used to evaluate the edible risk of Macrobrachium rosenbergii and the lifelong carcinogenic risk value of Macrobrachium rosenbergii in this area was 1.89×10-8?1.37×10-6,which basically met the standard value 1.0×10-6.The risk of cancer is low,but it cannot be ignored.?4?Combined with the growth habits and diet of Macrobrachium rosenbergii and correlation analysis,the benthic life of Macrobrachium rosenbergii growing up is in long-term contact with sediments,and at this time,predation of zooplankton,the suspended matter will also enter its body.Therefore,there is a significant correlation between the content of polycyclic aromatic hydrocarbons in shrimps and sediments,zooplankton and suspended solids during this period?P<0.05?,the correlation coefficients are 0.375,0.383 and 0.382 respectively.And the main source of polycyclic aromatic hydrocarbons in sediments,zooplankton and suspended matter is the pollutant emissions from surrounding factories,so the pollutant emissions from surrounding chemical plants have a greater impact on the content of polycyclic aromatic hydrocarbons in Macrobrachium rosenbergii.Phytoplankton only had a significant impact on Macrobrachium rosenbergii after it became an adult.?5?Based on the research results that the polycyclic aromatic hydrocarbon content in the sediments of the breeding ponds is at a relatively high level,this research recommends replacing the surface sediments of the culture pond or taking measures to reduce the polycyclic aromatic hydrocarbon content in the sediments about 1 month before the start of Macrobrachium rosenbergii breeding,control the amount of polycyclic aromatic hydrocarbons in the sediment,so as to ensure the quality of Macrobrachium rosenbergii products. |
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