Detection And Analysis Of Perfluorinated And Polyfluorinated Substances In The Environmental Multi-media Of Lake NamCo And The Contamination Characteristics

Perfluorinated and polyfluorinated substances(PFASs)are a new class of persistent pollutants.Long-chain PFASs are persistent,long-range transportable,toxic and bioaccumulative,so their production and use are gradually being restricted.Shortchain and even ultra-short-chain PFASs have been widely produced and used as alternatives.The cryosphere is a key component of the chemical cycle and an important reserve for PFASs.Under the background of global warming,more than 50%of the lakes on the Tibetan Plateau(TP)have expanded and 80%of the glaciers have retreated.Contamination characteristics of PFASs in glacial and lake waters have raised considerable concern.Therefore,this study was investigated on PFASs in the multienvironmental media of Lake Nam Co.A two-step elution method using solid phase extraction(SPE)and ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS)detection instrument were used to establish an experimental method that can analyze ultrashort,short and long chain perfluoroalkyl acids(PFAAs)and the precursor substance perfluorohexane sulfonamide(FHxSA)in different environmental media.The type of filter membrane,two-step elution method,type of mobile phase and the concentration of added salt were examined,and the performance parameters such as recovery and detection limits were evaluated.This method was applied to the analysis of trace PFASs in environmental multi-media samples of Lake NamCo.The conclusions are as follows:1、Firstly,acetate membrane was selected as the filtration material in this study,followed by the selection of a volume of 2 ml of methanol eluate in the first step and a concentration of 1%of ammonia in the ammonia-methanol eluate in the second step.Then methanol/water(V/V,9:1)was selected as dissolving solvent.Then then 2 mmol of ammonium acetate was selected as the added salt of the mobile phase.Finally,a low detection limit(0.01-3 ng/L)and high recovery(71.43-119.10%)analytical method that can analyze ultrashort-chain,short-chain and long-chain PFAAs and FHxSA simultaneously was established.2、The mean concentrations of ∑PFASs(C2-16)in glacial runoff were higher than those in non-glacial runoff(19,533 pg/L).The most dominant substance in both glacial and non-glacial runoff was(Trifluoroacetate)TFA,followed by(Perfluoro-n-butanoic acid)PFBA,the percentage of PFBA in glacial runoff(31.2%)was significantly higher than that in non-glacial runoff(14.1%).The mean concentration of ∑PFASs(C2-18)in lake Nam Co water was 6489 pg/L.PFBA was the dominant substance,followed by PFPeA.The mean concentration of ∑PFASs(C3-12)in soil was 1.1(ng/g dw)and in sediment was 0.61(ng/g dw).(Perfluoropropanoic acid)PFPrA was the dominant in sediments and soils,followed by PFBA.There is similar spatial variation in PFASs in Namucuo Lake,sediments and soils,with the mean concentration in the south side of Namucuo Lake(LW 1-4)being significantly higher than the north side(LW 9-10).The partition coefficients of PFASs in lake and sediment increased with increasing carbon chain length,and longer chains were more likely to be adsorbed in the solid phase.3、From 2017 to 2020,the mean concentration of ∑PFASs(C4-16)in glacial runoff increased from 1336 pg/L to 9836 pg/L from 2017 to 2020.The mean concentration of ∑PFASs(C4-18)in Lake NamCo increased from 980 pg/L to 3603 pg/L,a 4-fold increase,and the south side of the lake PFBA percentage increased from 23.0%to 55.2%.It may be related to the release of PFASs from glacier melting in the context of global warming.In addition,the proportion of short-chain PFASs in glacial and non-glacial runoff and lake water also increased significantly,by 6.7,6.8 and 4.7 times,respectively,which may be related to the replacement of long-chain by shortchain into productive use.Correlation analysis of PFASs in lake water revealed that there was no significant correlation between PFBA and other PFASs,which might have special sources.This study established a method that can simultaneously analyze ultrashort-chain,short-chain and long-chain PFAAs(C2-C18)and the precursor FHxSA,and applied to the analysis of water,soil and sediment in the Namucuo environment.It provides the analytical basis for the simultaneous study of ultrashort-,short-and long-chain PFAAs as well as FHxSA for detection and analysis.