The Fate Of Organophosphorus Flame Retardants As Well As Exposure Risks Of Marine Fish Intake In The Offshore Environment Of China

As an alternative to brominated flame retardants(BFRs),organophosphorus flame retardants(OPFRs)have been increasingly used worldwide in industrial and household products.To meet the growing demand for alternative flame retardants(FRs)in many commercial products,the production and use of OPFRs continue to grow.There are currently no restrictions on the production and use of OPFRs in China.And China has become the largest producer of OPFRs in the world,with the production of more than200,000 tons of OPFRs in 2013,which has the highest market share in the world,accounting for 35% of the global OPFRs market.The atmospheric emission of OPFRs during production and use not only poses certain environmental risks to terrestrial and aquatic ecosystems but also poses health risks to humans at the top of the food chain due to their bioaccumulation along the food chain.Numerous studies have been conducted to demonstrate the adverse effects of OPFRs on human health:developmental toxicity,carcinogenicity,neurotoxicity,endocrine disruption,and reproductive toxicity.It has been shown that chlorinated OPFRs(Cl-OPFRs)have stronger toxicity than that of brominated flame retardants such as polybrominated diphenyl ethers(PBDEs)as well as several other common characteristics of POPs.Based on the activity level data related to the provincial production and use of organophosphorus flame retardants in China,firstly,this dissertation established the gridded atmospheric emission inventory of OPFRs in China from 2019 to 2021 using the updated emission factor method;Secondly,based on this gridded emission inventory,the atmospheric transport model of Chn METOP was adopted to simulate the atmospheric transport behavior of OPFRs in the main environmental media of OPFRs in China.Thirdly,the flux contributions of OPFRs to the Bohai Sea via both of atmospheric transport and deposition as well as the surface river pathways were compared by combining the river model of Delft3 D.In addition,the sensitivity response of OPFRs concentration levels in the seawater of Bohai Sea to two flux input pathways including input via atmospheric transport,deposition,and surface river were estimated.Moreover,the bioaccumulation of OPFRs along the marine food web model and the resident health risks via fish consumption were assessed numerically.Based on the above studies,the results of this thesis are as followings:(1)Atmospheric emissions derived from production and use of OPFRs at the provincial level in China from 2019 to 2021: the total emissions from the production and use of OPFRs in Jiangsu,Zhejiang,Shandong,and Jiangxi in eastern China were much higher than those in other regions of China,with 1356.22,356.09,197.83 and149.19 t,respectively,accounting for 56.98% of the total national emissions.Among them,the production of these four provinces resulted in 83.04% of the total production emissions in the country,which is related to the fact that these four provinces are the major OPFRs producers in China.For use emissions of OPFRs,textiles are the largest emitting sector at 737.42 t in China,followed by: plastics,rubber,paints,wood,and pape.This sequence order is attributed to the high emission factor of textiles(1.9%)and the low emission factor of plastics(0.255%).Although the emission factor of rubber is smaller than that of paints and paper,the OPFRs use in the rubber industry is much higher than that of the paints and paper industries.(2)Annual gridded emission inventory of OPFRs in China: The annual gridded emission inventory of OPFRs in China with high resolution(1/4°×1/4°)was updated and established from 2019 to 2021.The production emissions of OPFRs are mainly concentrated in Jiangsu,northern Zhejiang,Shandong,and parts of Jiangxi.The area with the highest production emissions from 2019 to 2021 is also in Shanghai,followed by higher distribution in southern Jiangsu.The use emission characteristics indicate that most provincial areas of China exhibited the higher emission,and the highest use emissions of OPFRs were found at Shanghai,in addition,some other regions in China including the Yangtze River Delta,Pearl River Delta,Beijing,Tianjin,Shanxi,southern Hebei,Hubei,etc also showed,high emissions distributions.(3)The gridded distribution of OPFRs in the atmospher and soil in 2021 in China:The particle phase concentrations of OPFRs were higher than that of gas phase concentrations,indicating that OPFRs have higher fugitive concentrations in the particle phase.The atmospheric concentration characteristics of OPFRs simulated by Chn METOP are consistent with their emission and use,indicating the atmospheric emission and transport of OPFRs were the dominant roles for the pollution.Considering the prevailing westerly winds across China,it is assumed that OPFRs emissions from the upstream areas of western and central China or the eastern coastal region also contribute to some extent to OPFRs pollution in eastern China.The highest soil concentration levels were found in coastal cities of Zhejiang Province.The spatial distribution characteristics of the simulated soil OPFRs concentrations were consistent with those of their atmospheric emissions and atmospheric concentrations.The spatial distribution characteristics of OPFRs in soil and atmospheric environment in some regions of southern China are somewhat different,which are mainly related to the influencing factors such as atmospheric transport and deposition and soil organic carbon content.(4)Source-sink relationship of OPFRs from land source emissions via atmospheric transport in Chin’s oceans: Atmospheric deposition of OPFRs simulated based on the atmospheric transport model Chn METOP in 2021 shows that the wet deposition contributes to atmospheric major deposition fluxes of OPFRs.The concentrations of OPFRs in seawater and sediment decreased rapidly eastward,with a decrease of three orders of magnitude from the coastal region to the deep ocean.With an eastward diffusion trend and higher sedimentation rate under the action of the westerly zone,led to the higher concentrations of OPFRs in the coastal and marine environment.The analysis of the source-sink relationship of OPFRs in the four major seas shows that: the main land source emission areas varies in different seas,all of them are dominated by the contribution of emission sources adjacent to the coastal zone and offshore land,and the contribution load of the southern coast to the seawater concentration in the South China Sea in 2021 is 99.7%;the central coast is the region with the largest national emissions and has input to all four major seas;the northern coast has atmospheric transport of OPFRs to the East China Sea and the South China Sea The input is negligible,which may be related to the lower temperature and farther distance of the northern coast compared with the East China Sea and South China Sea;the input of OPFRs from the western inland to the Chinese sea is negligible.(5)Comparison of flux contributions of OPFRs to the Bohai Sea via atmospheric deposition and river input: The contributions of atmospheric deposition and river to OPFRs in the Bohai Sea environment were quantitatively assessed using the Chn METOP atmospheric transport model and Delft3 D river transport model.The river and atmospheric transport model simulations reveal that atmospheric transport and deposition(including dry,wet,and diffuse gaseous deposition)dominate the main fluxes of OPFRs into the Bohai Sea,being 23 times greater than riverine input in 2013.The dry deposition flux was the highest in winter and lowest in spring.The largest wet and river loadings of OPFRs occurred in summer,which was attributed to high precipitations over the Bohai sea region during the East Asian summer monsoon season.(6)Bioaccumulation of OPFRs in the marine food web and exposure risk of marine fish intake: The exposure risk due to consumption of these 10 species of marine fish in different populations was assessed.Consumption of OPFRs contaminated fish was higher in females than in males in the same age group,and the values of EDIs increase with age in men and decrease and then increase with age in women.However,among the 10 marine fish species estimated in this study,the intake of OPFRs from the consumption of these fish in the Bohai Sea was far from the reference dose(Rf D)set by USEPA for human health risk through animal studies.Although no health risk has been shown for all populations via ingestion of marine fish,OPFRs are multi-pathway exposure contaminants and their POPs-like physicochemical properties allow them to accumulate and amplify in the human body,therefore,the potential exposure risk and health hazards still need to be considered.The major innovation of this thesis is a comparison of the relative contribution of OPFRs to the Bohai Sea via atmospheric transport deposition fluxes and riverine input fluxes based on the atmospheric transport model and river input model: the contribution of atmospheric transport of OPFRs to the Bohai sea is two orders of magnitude higher than that of surface river input fluxes,where OPFRs are more easily traceable.However,the diversity of sources of atmospheric emissions via the atmosphere,the complex atmospheric circulation upon entry,the dispersive behaviour of turbulent activity,and the uncertainty of physical and chemical processes make pollution prevention,control,and management of OPFRs in the Bohai Sea ecosystem more difficult.In order to mitigate OPFRs pollution in the Bohai Sea more effectively,more attention should be given to identifying and reducing atmospheric emission sources and identifying the main atmospheric pathways.