Numerical Simulation Of Short Chain Chlorinated Paraffins In The Chinese Environment And Exposure Risks Of Marine Food

Short-chain chlorinated paraffins(SCCPs)are a group of chlorinated paraffins(CPs)with 10-13 carbon chain number.With typical characters of persistent organic pollutants(POPs)such as high toxicity,bioaccumulation,semi-volatility,and persistence,SCCPs can reach remote pristine regions by long range transport,resulting in environmental pollution globally.In 2017,SCCPs were listed in Annex A of the Stockholm Convention by the POPs Review Committee(POPRC).China accounted approximately for 20%-30% of the total global CPs production,which mainly came from coastal areas of China.Since the high lipophilicity and resistance to metabolism of SCCPs,ocean is an ultimate sink where SCCPs may behave with potential bioaccumulation for the marine species through the transfer and biomagnification of the marine food web,as a result of diverse pollution to marine environment and creatures.The intake of SCCPs contaminated seafood is one of the main pathways of human exposure to SCCPs,especially the intake of fish species at high trophic levels of marine food web,which would bioaccumulate SCCPs via the marine food web.Marine fish is caught in coastal provinces in China and transported to other regions through provincial fish trade and logistics.In particular,as the provincial trade is becoming increasingly wide,food trade provides another transfer route for contaminants among regions besides the atmospheric transport and ocean current,rendering higher risks embodied in trade.To date,given that food origins were not taken into consideration in the human exposure assessment to chemicals induced by food intake,concerns might be raised for large uncertainties in the estimate of health exposure,typically when there were big gaps of contamination levels between production area and consumption area.To confirm the environmental behavior,exposure risks,and human exposure of SCCPs embodied in the provincial fish trade,in the present study,firstly,we developed a SCCPs atmospheric emission inventory in China with a high spatial resolution.Secondly,an atmospheric transport model for POPs was adopted to simulate the distribution,environmental behavior,and sourcereceptor relationship of SCCPs in China and its marine environment,including the Bohai Sea(BS),Yellow Sea(YS),East China Sea(ECS),and South China Sea(SCS).Thirdly,by coupling a marine food web model and exposure risk assessment model with the atmospheric transport model,SCCP levels in marine biota were simulated and human exposure to SCCPs through the intake of contaminated marine fish species by SCCPs are assessed numerically.Finally,the human exposures to SCCPs embodied the provincial seafood trade were estimated,taking hairtail as an example.The major findings from this study and results in this thesis are summarized below:(1)The national total emissions of SCCPs into atmosphere were 1068.4,968.6,1042.9,1127.6 and 1444.0 tons from 2008 to 2012,respectively.Among five emission categories,as an additive in metal cutting fluids was the most primary emission source of SCCPs,emitted 2680.2 tons of SCCPs during these five years,followed by the production of CPs(2281.8 tons),use as plasticizers(514.3 tons),use as flame retardants(108.6 tons),and net import(66.6 tons).The eastern and southern seaboard regions were primary SCCP emission sources.During the five years,Shandong emitted most SCCPs at 742.3 tons,followed by Jiangsu(724.0 tons),Zhejiang(573.4 tons),Henan(456.7 tons),and Guangdong(441.7 tons).The spatial distribution of gridded emissions of SCCPs agreed with the gridded SCCP emissions released from metal cutting fluid industries,which centered in the well-developed eastern and southern China with concentrated night light and high population density.(2)Modeled SCCPs levels in air,seawater,aquatic sediment,and total depositions displayed a declining trend towards offshore.Under the influence of the prevailing westerly wind of free atmosphere,SCCPs were delivered from the eastern seaboard sources with high depositions to the Eastern China Sea,paving a major pathway(plume)of SCCPs loadings and transport which caused the contamination to marine environment.Given that SCCPs were still widely used in China,the dynamic equilibrium status between soil and air as well as air and water in coastal regions and waters were not reached yet,instead of discerning SCCP loadings to the soil and marine surfaces.The source-receptor relationships over the four sea bodies were identified,showing different source regions for various sea bodies.The modeling results revealed that the nearby emissions in eastern and southern China contributed at least 64% to the total deposition and air-water exchange flux for these four marine bodies,especially the SCS,with the nearby sources around the southern seaboard region accounting almost 100% for SCCPs pollution to the SCS.By investigating the monthly contribution of dry and wet deposition of SCCPs from the two major source areas across the BS in 2011,we found that the local emissions contributed most,followed by meteorological conditions.(3)Modeled SCCP concentrations in 11 marine fish species in China ranged from 31 to 1337 ng/g.The Estimated Daily Intake(EDIs,ng/(kg?day))index was applied to conduct the risk assessment of human exposure to SCCPs via consumption of SCCP contaminated marine fish species.The results indicated that the EDIs for the groups of age 1-5,6-18 and >18 were 21.7-1033.0,21.8-1082.7,and 23.0-1133.4 ng/(kg?day),respectively.Seniors and females might suffer higher exposure risk.Overall,our results also showed that SCCPs dose in the selected marine fish species would not result in obvious exposure risks to fish consumers at different age groups or genders.(4)An investigation of human exposure to SCCP embodied in provincial seafood trade indicated that Zhejiang,Fujian and Shandong were the top three provinces with highest production of hairtail in China,the corresponding caught EDIs of SCCPs in hairtail fish in these four provinces accounting for 38-41%,26-29%,and 6-8% of the national total caught EDIs of SCCPs,respectively.Shanghai and Tianjin were the regions with the highest consumption EDIs of SCCPs via hairtail consumption at 1.6-7.8 and 0.7-2.8 ng/(kg?day),respectively.If hairtail consumed by Shanghai residents was entirely imported from Zhejiang,the EDIs of SCCPs in Shanghai residents would decrease 50.5-62.8%.In the other case,if hairtail fish consumed by Tianjin residents was imported half from Shandong and the other half from Zhejiang,the EDIs of SCCPs for Tianjin residents would increase 276.8-361.2%.The results revealed that both marine environment and caught fish origins would affect the human exposure risk to SCCPs.