Analytical Methods Of Typical Perfluorotelomers And Their Degradation Products And Their Metabolic Transformation And Accumulation In High/Low Accumulation Lettuce Varieties

Perfluorinated polyhydric alcohols(FTOHs)are widely used chemical products,which are released into the environment in large quantities during production and use,and are easily degraded into persistent perfluorocarboxylic acids with higher toxicity.For example,8: 2FTOH is an important precursor of perfluorooctanoic acid(PFOA).At present,researches on FTOHs and their degradation products are mainly concentrated in the field of water environment,but their analytical methods in soil-crop and the law of degradation,transformation and accumulation are still rarely reported.To this end,this project took typical FTOHs(6: 2FTOH,8: 2FTOH,10: 2FTOH)as the target compounds,established its own and intermediate product efficient analysis methods in soil and crops,and further discussed on this basis 8: 2FTOH accumulation and degradation transformation in soil-perfluorooctanoic acid(PFOA)high / low accumulation lettuce varieties.Obtained the following main research results:(1)Based on surface optimization design,ultrasonic extraction and gas chromatography-mass spectrometry(GC-MS)were established to simultaneously determine three typical FTOHs(6:2FTOH,8:2FTOH,10:2FTOH)in different crops(lettuce,carrot,cucumber,celery,potato)and soil with different physical and chemical properties.A high-efficiency analysis method that had achieved a single efficient extraction and analysis of the target FTOHs without concentration conditions and quantitative analysis.The optimal pretreatment conditions for extracting FTOHs in crops are:ultrasonic extraction with 4 m L methanol for 30 min,and then purification with ENVI-carb 50 mg;the optimal pretreatment conditions for extracting FTOHs in soil are:ultrasonic extraction with 5 m L methanol for 40 min.Then use 20 mg ENVI-carb for purification.Under the optimal treatment conditions,the detection limit of the target FTOHs matrix in the crop is 0.025 ng/g～0.897 ng/g,and the recovery rate of spiked at different concentrations(2,10,20 ng/g)is 86%～118%,standard deviation both are less than 19.4%;the detection limit of the target FTOHs matrix in the soil is 0.083 ng/g～0.825 ng/g,the recovery rate of the spiked with different concentrations(2,10,20 ng/g)is 81%～118%,and the standard deviations are all less than 17.7%.Using this method,the target FTOHs content in the farmland soil-crop system around the typical fluorination plant in the Pearl River Delta was analyzed,and it was found that the detection rate in the soil was 50.0%～75.0%,and the detection concentration was 1.6～44.3 ng/g.The detection rate in crops is 55%～70%,and the detection concentration is 1.5～37.9 ng/g.(2)Based on the optimized design of the surface,the ultrasonic extraction,liquid chromatography-tandem mass spectrometry(HPLC-MS / MS)was established to simultaneously determine 8:2FTOH and its degradation products in different crops(lettuce,carrot,cucumber,celery,potato)and soil with different physical and chemical properties.The high-efficiency analysis method of polyalcohol has realized the quantitative analysis of typical FTOH and its degradation products by simultaneous chromatography-mass spectrometry.For crop substrates,the optimal pretreatment conditions are: 3 m L methanol extraction for 30 min,then 50 mg ENVIcarb purification;soil substrate optimal pretreatment conditions: 4 m L methanol extraction for 35 min,and then 20 mg ENVI-carb purification.Under the optimal treatment conditions,the detection limit of the target compound matrix in the crop is 0.004 ng/g ～ 0.222 ng/g,and the recovery rate at different concentrations(2,10,20 ng/g)is 77% ～ 121%,standard deviation Both are less than 20%;the detection limit of the target compounds matrix in the soil is 0.003 ng/g ～ 0.441,the recovery rate of the spiked with different concentrations(2,10,20 ng/g)is 82% ～ 119%,and the standard deviation Less than 20%.This method was used to analyze the content of 8: 2FTOH and its degradation products in the farmland soil-crop system around the typical fluorination plant in the Pearl River Delta.The detection rate and concentration of 8: 2FTOH were 90% and 0.68 ～ 17.84 ng/g,the detection rate of its degradation products(8: 2FTUCA,8: 2FTCA,7: 3FTCA,PFHx A,PFOA)is 100%,100%,100%,95%,45%,100%,and the detection concentration is 0.48 ～ 2.59 ng/g,0.84 ～ 7.66 ng/g,0.45 ～ 5.94 ng/g,0.14 ～ 4.88 ng/g,0.14 ～ 2.82 ng/g.(3)Through the pot experiment,and setting the soil sterilization and non-sterilization treatment,the treatment with no addition of 8:2FTOH was used as a control to discuss the absorption and accumulation of 8:2FTOH by lettuce varieties with high and low accumulation of PFOA under different 8:2FTOH exposure,rhizosphere degradation and metabolism in the body.The results showed that the lettuce planting treatment significantly promoted the degradation of 8:2 fluorotelomer alcohol in soil.The main degradation products of 8:2fluorotelomer in soil are PFOA(10～106 ng/g),followed by PFHx A(0.17～1.49 ng/g),FTCA(0.5～0.63 ng/g)and 8:2FTCA(0.1～0.66 ng/g).The detection amount is low;overall,the content of 8:2 fluorotelomers in the soil of high-accumulation lettuce varieties is lower than that of low-accumulation lettuce varieties,and the content of its main degradation products PFOA and PFHx A is higher.In the latter case,it shows that the high-accumulation varieties have a stronger rhizosphere degradation effect on 8:2 fluorotelomers than low-accumulation varieties.The sterilization treatment greatly reduced the degradation and transformation of 8:2fluorotelomers by high and low accumulation lettuce varieties.High and low accumulation lettuce varieties have significant accumulation effects on 8:2 fluorotelomers and their degradation products(PFOA,PHFx A,8:2FTCA,etc.),with PFOA(109～401 ng/g,dw)and PFHx A as Main(25～359 ng/g,dw);the accumulation of these two compounds in high-accumulation lettuce varieties is higher than that in low-accumulation lettuce varieties.Alcohol dehydrogenase(ADH),acetaldehyde dehydrogenase(ALDH),glutathione(GST),and cytochrome(CYP450)are all involved in the degradation of 8:2FTOH by lettuce,and these enzymes are not sterilized Medium activity is higher.It can be seen that microorganisms not only play an important role in the degradation and transformation of 8:2 fluorotelomers in lettuce rhizosphere soil,but also significantly affect the absorption and accumulation of different lettuce varieties on their precursors and degradation products(ie PFOA and PFHx A).