Effects Of Freeze-thaw And Deicing Salts On The Environmental Behaviors Of Perfluoroalkyl Substances(PFASs) In Soil

As a new type of persistent organic pollutants,perfluoroalkyl substances(PFASs)are widely used in the production of industrial and daily products,which have chemical stability and thermal stability.PFASs are persistent in the environment,which can be biomagnified through the food chains with bioaccumulation and biotoxicity.There are few studies on the the effects of freeze-thaw and deicing salts on the environmental behaviors of organic pollutants.Therefore,on the background of the severe changes in global climate,exploring the environmental behaviors of PFASs in the soil,which was influenced by freeze-thaw and deicing salts,has a great significance to evaluate the ecological risks of PFASs and the sustainable development of society.The main research contents and related conclusions of the present study were presented as follows:(1)The effects of freeze-thaw on the environmental behaviors of PFASs in the soil-plant system were investigated using wheats(Triticum aestivum L.)as a model plant.The results indicated that the greatest influencing factor was freezing temperature at-10 ?,freeze-thaw frequency at 9 times,and freeze-thaw moisture at 120% of the maximum field water-holding capacity,based on the R software analysis.The effects of freezing temperature,freeze-thaw frequency and freeze-thaw moisture on the environmental behaviors of PFASs were investigated at the greatest influencing factor.The results proved that the change of freezing temperature could affect the environmental behaviors of PFASs in wheats.When the freezing happened at-10 ?,the concentrations of PFASs in wheat roots,shoots and whole plants could be promoted(P < 0.05),and the root concentration factor(RCF),shoot concentration factor(SCF)and bioconcentration factor(BCF)of PFASs in wheats reached the maximum value,compared with the blank.With the increasing of freeze-thaw frequency,the bioaccumulation of PFASs in wheats at lower concentrations was enhanced,and the weakening trend happened at higher concentrations.The maximum enhancement ability of PFASs was recorded at 9 times of freeze-thaw frequency.Compared with the blank,the bioaccumulation of PFASs in wheats was promoted significantly(P < 0.05).When the freeze-thaw happened on soil,the bioaccumulation of PFASs in wheat roots,shoots and whole plants was promoted with the increasing of freeze-thaw moisture(P < 0.05).The bioaccumulation factors(RCF,SCF,BCF)of PFASs in wheats reached the maximum when the freeze-thaw moisture at 120% of the maximum field water-holding capacity.(2)Based on the greatest influencing factor as the standard freeze-thaw condition,the effects of freezing temperature,freeze-thaw frequency and freeze-thaw moisture on the adsorption and desorption behaviors of PFASs were investigated.The results illustrated that the change of freezing temperature could affect the adsorption and desorption behaviors of PFASs in soil.Compared with the blank,the adsorption and desorption behaviors of PFASs were enhanced significantly at the-10 ? of freezing temperature except PFOS(P < 0.05),which could enhance the bioavailability of PFASs.And the desorption of PFASs was enhanced at the 9 times of freeze-thaw frequency.Compared with the blank,the desorption of PFASs in soil showed an upward trend with the increasing of freeze-thaw moisture.(3)The effects of deicing salt interference on the bioavailability of PFASs were explored in wheats.The results revealed that the bioavailability of PFASs in wheat roots and shoots could be promoted significantly with the increasing concentrations of deicing salts(P < 0.05).The bioaccumulation of PFASs in wheats could be enhanced by deicing salts,and with the increasing concentrations of deicing salts,the bioaccumulation of PFASs was enhanced in wheats,indicating that the ecological risks of PFASs in soil were enhanced by deicing salt interference.