Dynamics Of Perfluoroalkyl Substances In Farmland Around Fluorinated Industrial Parks

Perfluoroalkyl substances have been detected in various levels in different environmental media around the world since they were produced and used extensively from the 1950 s.In recent years,to meet both domestic and international demand,a large number of fluorinated industrial enterprises have been transferred to developing countries including China.As a result,the levels of perfluoroalkyl substances in China's environment are relatively higher compared to other countries.Their impacts on crops and ecosystems are not clear yet,and the relevant risk assessment standards and regulatory measures are relatively scarce.As a major source of food,crops accumulated PFAAs from contaminated environments and thus their potential health risks cannot be ignored.In response to this problem,based on the existing data and field monitoring,the soil and winter wheat around the fluorinated industrial parks were taken as the research objects,with PFAAs as the target contaminants.Field sampling and indoor experimental research were conducted.Based on the temporal and spatial analysis of the distribution of PFAAs in farmland soil and winter wheat,the occurrence,dynamics,compositional changes,and potential risks of PFAAs on farmland ecosystems and human health were discussed.The predominant findings were as follows:(1)In terms of the temporal variation,the highest average concentration of PFAAs in farmland soil(224.73 ng/g)occurred in the winter period,and the lowest concentration appeared in the maturation period of winter wheat(35.38 ng/g).Throughout the growth period,the average concentrations showed a gradually decreasing trend.PFOA contributed most to the PFAAs of farmland soil,and its highest concentration(1563.05 ng/g)also appeared in the wintering period,which was the highest soil concentration reported so far.The concentration of PFOA decreased gradually with the growth stages,while the concentration of PFBA and PFHxA appeared rising fluctuations during the green period and heading period probably affected by the irrigation.The concentrations of long-chain PFCAs(except PFOA)and PFSAs including PFBS,PFHxS,PFOS,and PFDS were all at low levels or even below detection limits.(2)In terms of the spatial distribution,the main pollution hot-spot of PFAAs in soil was located at the nearest farmland to the fluorinated industrial parks.As the distance from the pollution source increased,PFAAs showed a sharp decline and then a slowly decrease.And within 2-10 km from the fluorination industrial parks,the average concentrations of PFAAs in the northward soil were higher than that in the southward.PFOA was still the highest component of PFAAs in farmland soil.The highest average concentration(592.27 ng/g)was detected in the farmland soil within the distance of 0-1 km from the fluorinated industrial parks,and gradually decreasing with the distance increasing.However,the proportions of short-chain PFCAs(C4-C6)with strong environmental transportability have increased as the distances from the industrial parks increased.(3)In terms of the temporal variation,the concentrations of PFAAs in different organs of winter wheat showed: ears>stems and leaves>roots>grains.The average concentrations of short-chain PFCAs in roots,stems,ears,ears(-)and grains showed: PFBA>PFPeA>PFHxA>PFHpA.Only the higher concentrations of PFOA were detected among long-chain PFCAs,and the concentrations of the other long-chain PFCAs and PFSAs were both at trace level or below the detection limits.(4)In terms of the spatial distribution,the concentrations of PFAAs in the roots,stems and leaves,ears,ears(-),and grains in winter wheat tended to decrease with the south distances from the fluorinated industrial parks increased.But in the range of 4-7 km to the north from the industrial site,the concentrations of PFAAs in winter wheat first showed a decreasing trend,followed by a rise and then a decrease.The relative concentrations of long-chain PFUnDA,PFDoDA,PFTrDA,PFTeDA,PFHxDA,PFODA,and PFOS in the grains were significantly higher than those in other organs.(5)The accumulation of contaminants in various parts of wheat was as follows: ears>stems and leaves>roots>grains,and it gradually decreased with the extension of carbon chain of PFAA components.The logarithm of the concentrations of PFAAs and PFAA congeners in different organs of winter wheat showed a positive correlationwith the logarithm of soil concentrations.(6)Compared with soil concentrations,the concentrations of PFBA,PFPeA,PFHxA,and PFHpA in winter wheat were significantly higher.Short-chain PFCAs and PFOA were the main components of PFAAs in roots,stems and leaves,ears,and ears(-).Short-chain PFCAs were the main components in grains.The concentrations of PFBA,PFPeA,PFHxA,PFHpA,PFOA,PFNA,and PFDA in winter wheat were highly correlated with each other and were almost consistent with the correlation of PFAAs in farmland soil.(7)The EDIs of total PFAAs and the main PFAA components in winter wheat grains for infants and children were similar,and all were higher than those for adults.The highest EDIs of total PFAAs and major PFAAs in different age groups occurred in the 0-1 km range around the fluorinated industrial parks and the EDIs of PFAA congeners showed a trend: PFBA>PFPeA>PFHxA>PFOA>PFHpA.(8)Within 1 km range around the fluorinated industrial parks,the EDIs of PFOA for infants,children,adolescents and adults were 148.16 ng/kg·bw/day,150.11 ng/kg·bw/day,113.99 ng/kg·bw/day and 101.18 ng/kg·bw/day,which have exceeded the health guideline value(HBGV)(ng/kg·bw/day)published by Germany and pose health risks to local residents.