Study On The Occurrence And Sorption Of PFAS In Soils From Different Functional Areas In Shanghai

Perfluorinated and polyfluoroalkyl compounds(PFAS)were a new class of pollutants that have been detected in soil,air,surface water,groundwater,animals and humans,resulting harm to human health and ecological safety.There was still a lack of research on PFAS in soils,and it was important to systematically investigate the characteristics and environmental behaviour of PFAS in soils from different functional areas.In this thesis,a pretreatment(Ultrasonic extraction combined with solid phase extraction)and instrumental detection method(Ultraperformance liquid chromatography/mass spectrometry)for 18 PFAS in soil was developed and optimised.The characteristics and contamination sources of PFAS in soils from different functional areas of Shanghai-fire stations,industrial areas,airports,landfills,and agricultural areas(referring to agricultural areas around industries)were investigated.The sorption behaviour of PFAS with different chain lengths in soils was investigated.The main findings of this paper were as follows:(1)The optimum pretreatment conditions were determined for 60 mesh size soil,40℃sonication temperature,10 min sonication time,WAX Oasis(150 mg/6 mL)size extraction column and 2 mL methanol/4 mL 0.1%ammonia-methanol gradient eluent.PFAS showed good linearity over the concentration range of 0.1-200 μg/L,with correlation coefficients(R2)all greater than 0.996.The method had a limit of detection(LOD)of 0.003-0,100 μg/L and a limit of quantification(LOQ)of 0.010-0.300μg/L.PFAS recoveries ranged from 76.3%to 132%with relative standard deviations(RSD)of 0.35%to 10.7%.(2)Total PFAS concentrations in Shanghai soils ranged from 0.64-294 μg/kg,with the following trends in different functional areas:fire stations(mean=57.9 μg/kg)>industrial areas(mean=8.53 μg/kg)>agricultural areas(mean=6.52 μg/kg)>airports(mean=6.14μg/kg)>landfills(mean=5.04 μg/kg).The waste treatment area in the industrial area(mean=11.4 μg/kg)>the electroplating industrial area(mean=8.46 μg/kg)>the chemical industry area(mean=8.01 μg/kg).Fire stations and industrial areas were the main sources of PFAS in the surrounding soils.PFOA,PFOS and PFBA were the most dominant PFAS components in soils.Long-chain PFCA,PFSA and GenX were less concentrated and detected in soils.Highly correlated PFCA(C5-C7,C9-C12 and C14-C18)in soils may have the same input and migration pathways.(3)The sorption capacity and rate of four typical PFAS(PFBA,PFHxA,PFOA and PFDA)in soil were related to their carbon chain length.Overall,the longer the length of the PFAS carbon chain,the higher the sorption capacity and sorption rate.The quasi-secondary kinetic and biconstant models for the four PFAS in soils fitted well(R2>0.993).Lsothermal sorption of the Freundlich model fitted well(R2>0.902).PFAS were mainly dominated by chemisorption.There was a competitive effect of PFAS in soil sorption,related to its carbon chain length,the longer the chain,the stronger the competitive effect.The adsorption rate of PFAS in a single system was less than in a multiple system.The adsorption capacity of PFAS in the single system was greater than that of the multiple system,and the adsorption capacity decreases as the number of PFAS species in the system increases.