Interaction And Mechanism Between Microplastics And Typical Environmental Endocrine Disrupting Compounds

Microplastics?MPs,with a diameter of<5 mm?are emerging pollutants that have been extensively detected in almost all the environmental media.It has been regarded as vectors for contaminants owing to their strong hydrophobicity,large surface area and large amount of contained plastics additives,causing potential environmental risk.However,the mechanism of MPs-contaminants interaction and their potential risks are not fully understood.A comprehensive study of the interaction mechanisms between EDCs and different types of MPs is therefore conducted to elucidate the potential risk of MPs-contaminants compound.The main contents and results are as follows:?1?The effect of MPs'physicochemical properties on their sorption ability was explored by investigating the sorption behavior of E2 on twelve types of MPs.The adsorption or partition contribution of E2 sorption on MPs was quantified with dual-mode sorption model mechanism.Notably,polyamide?PA?and polyurethane?PU?has the highest sorption for binding E2 due to the great contribution of hydrogen bonding.The hydrophobic interaction dominantly regulates the sorption of E2 on the other ten kinds of MPs due to the high crystallinity of MPs and high accessibility of amorphous domain of rubbery MPs.Hydrophobic partition-dominating sorption mechanism of E2on MPs was therefore obtained through applying the dual mode model.In addition,it was proved that the sorption differences of different EDCs?estrone,estradiol,17?-ethinyl estradiol and bisphenol A?on the same type MPs were mainly caused by the different hydrophobicity of EDCs.And the contribution percentage of hydrophobic interaction on BPA sorption to glassy MPs is larger than that to rubbery MPs.?2?In order to comprehensively evaluate the potential environmental risks of MPs as both source and sink for toxic chemicals,sorption/desorption/release behaviors between BPA and twelve types of MPs were therefore explored.PA and PU were found to exhibit the highest sorption capacity for bisphenol A,and it was almost irreversible,due to hydrogen bonding.Rubbery polyethylenes?PE?and polypropylene?PP?exhibited high and reversible sorption without noticeable desorption hysteresis.Glassy polystyrene?PS?,poly?vinyl chloride??PVC?,poly?methyl methacrylate??PMMA?,and poly?ethylene terephthalate??PET?exhibited low sorption capacity and only partial reversibility.Low-density polyethylene and polycarbonate MPs particles were for the first time proved to be a persistent source releasing bisphenol A into aquatic environments.Salinity,pH,coexisting estrogens,and water chemistry influence the sorption/desorption/release behaviors to different degrees.Plastic particles can serve as transportation vectors for BPA,which may constitute an ecological risk.?3?Virgin PS,LDPE and PC MPs were exposed to different aging conditions including UV/H₂O,UV/H₂O₂,and UV/Chlorine aqueous systems,and their subsequent interaction with BPA were investigated.The results revealed that aging process causes apparent degradation and surface oxidation of PS,and the surface hydrophicility of aged PS dramatically decreased compared with that of the virgin one.Obviously deteriorative BPA sorption capacity on aged PS was observed compared with that of virgin PS,mainly attributed to the weaker hydrophobic and?-?interaction between them.Aging has no obvious effect on the hydrophilicity and surface polarity of LDPE,but the crystallinity of aged LDPE increased to different degrees.Aging process leads to significant leakage of BPA additives from LDPE,and no BPA leakage from aged LDPE was observed.Strikingly,aged LDPE was found to have strong sorption ability towards BPA,and the sorption capacity found a significant negative correlation with the crystallinity of aged LDPE.The aged PC can also serve as a persistent source releasing BPA into aquatic environments,but the release rate was clearly slower than the virgin one.?4?The potential risks of many types of environmental sorbents?PA,HDPE,active carbon,graphene oxide,carbon nanotubes,soil and sediment?were evaluated by investigating their BPA sorption and desorption behavior.The sorption capacity of PA and carbon sorbents are found to be about equal,while the desorption percentage of BPA from PA is significant higher.As a result,the potential environmental risk caused by the migration of BPA via PA was clearly higher than that of carbon sorbents.The BPA sorption capacity on the other three kinds of sorbents was in the sequence of soil>HDPE>sediments,while the BPA desorption capacity from HDPE was equal to that of soil.It suggested that the environmental risks caused by the migration of BPA via MPs are far less than those caused by soil and sediment,while it still deserves attentions.