Pollution Characteristics And Partitioning Of Perfluoroalkyl Substances And Isomers In Humans And Environment

Perfluoroalkyl Substances（PFASs）are important artificial surfactants,and have been widely used in commerical and household products.Because PFASs are ubiquitous in the environment and may cause adverse biological effects,perfluorooctanoate（PFOA）and perfluorooctane sulfonate（PFOS）are regulated or restricted in many countries.Production of PFASs is mainly by electrochemical fluorine（ECF）and telomerization.PFASs produced by ECF method contain 20-30%of branched isomers,and PFASs derived from telomerization are characterized by pure linear isomers.PFAS homologues have different carbon chain lengths and ending functional groups（such as PFSAs and PFCAs）.Their partitioning behaviors in human body and environment directly influence their health effects and environmental fates.In this thesis,distribution of PFASs and their isomers in human blood and environmental matrices in a fluorine chemical industry park were investigated.Then,we further investigated their partitioning in human blood and between water and air,with a purpose of providing a theoretical base to understand the human health effects and environmental fate of PFASs.A sensitive analytical method was developed for quantification and quantitation of PFOA,PFOS,and seven PFOS precursors in human serum samples.The target compounds were separated on a FluoroSep RP Octyl column using methanol and ammonium acetate solution as mobile phase by gradient elution.Three different extraction methods were compared for the extraction efficiency of target perfluorochemicals in human serum samples,and finally acetonitrile/ethyl acetate（volume ratio 60:40）was selected as the best extraction solvent.This method has good stability,high accuracy,and could analyze different kinds of PFOS precursors and PFOA and PFOS isomers at the same time,which was also applicable to the quantitative analysis of actual human serum,blood cells and whole blood samples.The developed isomer–specific analytical method was applied to monitor native PFASs in 60 paired samples of human plasma and whole blood.Meanwhile,we also carried out an in-vitro experiment with fresh SD rats blood spiked with PFASs.In human samples,the partition coefficient between serum and whole blood(K_p/b)increased as the carbon chain length increased from C6（mean,0.5）to C11（1.8）among perfluoroalkyl carboxylates,indicating preference for the serum fraction with increasing chain–length.Conversely,for PFHx S（6 perfluorinated carbons）the K_p/b（mean,1.9）is larger than that for PFOS（1.7）（8 perfluorinated carbons）.Generally,PFOS–precursors display lower K_p/b values than PFOA,PFHx S,and PFOS,and perfluoroctane sulfonamide had the lowest K_p/b of any substance detected.Linear isomers of PFOS,PFOA,and PFOS–precursors have lower mean K_p/b than the corresponding branched isomers.PFASs,except PFHxS,the plasma only contains up to 90%,but as little as 25%,of the total amount in whole blood.The in-vitro test results were basically consistent with results of human blood monitoring.To study the impacts of PFASs manufacturing on surrounding environment,sampling was conducted around a major fluorochemical manufacturing park in China.Perfluoroalkyl sulfonates（PFSAs）were lower than perfluoroalkyl carboxylates（PFCAs）in all samples,and short-chain（C₄-C₆）PFCAs were predominant.Perfluoroalkyl phosphonates and phosphate diesters were occasionally detected,but at low detection frequency.Branched isomers of perfluorobutane sulfonate（PFBS）were reported for the first time,accounting for 15-27%of total PFBS in water.An enrichment of isopropyl-PFOA（28%）was found in WWTP influent,suggesting its manufacturing primarily by isopropyl telomerization.More numerous branched isomers were observed for the longer C₉-C₁₃ PFCAs(e.g.C₁₂ PFCA had 16 branched isomers),including high proportion of one major branched isomer（likely isopropyl）,possibly as impurities from isopropyl-PFOA manufacturing.Overall,short-chain perfluorinated acids were the predominant PFASs being released,but PFOA was still a major chemical in use at this site,primarily from isopropyl telomerization.We adopted a static equilibrium method to investigate the partitioning of PFCAs,including the isomers of PFOS and PFOA,betwen water and air.The results showed that in water phase at pH 0.3,n-PFOA partitioned more to the gas phase than branched isomers.For branched PFOA isomers,the water-to-air transfer potentials followed the order of iso-≈5m->4m->3m-PFOA.In the water phase at pH 7.3,C4-C12 PFCAs were all dissociated（i.e.no obvious water-to-air volatilization found）,and the isomer signatures of perfluorooctanoate anion in water phase did not（p>0.05）chang distinctly over time.PFOS was used as a negative control at both pH values and was not volatilized at all.The isomer-specific transport of PFOA may provide a new tool for tracing the source of PFCAs detected in atmosphere（especially in remote regions）.Knowledge of isomer-specific water-air partitioning of PFCAs is vital for source tracking,and for understanding their atmospheric transport and fate,but is not well known.