| As a new kind of environmental pollutant,microplastic(MP)has attracted more and more attention.Apart from the negative effects on both environment and biota caused by microplastic,it can also release additives to environment and sorb organic pollutants from environment,bringing potential risk to nature.Many kinds of additives are added to polymer during manufacture process,which can leach out during the aging processes of MPs,and will migrate with the transportation of MPs.Therefore,more attention should be paid to the release of additives from MPs.In recent years,a large amount of PVC pipes has replaced traditional metal pipes,as well as the wide use of disposable infusion tubes in medical industry,leading to a lot of waste plastic at the same time.And phthalate ester(PAE),a kind of plasticizers,is one of the most widely used additives in PVC plastic,which can account for 60% by weight.In addition,it is physically added to polymer matrix,not chemically bonded,so it is very easy to migrate to environment.Therefore,it is essential to pay attention to the release of additives from MPs.The information about the release behavior of a certain kind of additives from MPs in environment is limited.So in this paper,the release behavior of PAEs from PVC pipe MPs in water environment was studied.It mainly includes the following contents:(1)A pretreatment method based on LDPE membrane passive sampler to analyze the contents of PAEs in water was established.Through the determination of membrane-water partition coefficients,a fast and dynamic monitoring method for the dissolved PAEs contents in water phase was established.This method greatly simplified the operation process,reduce the difficulties detection,and provided a technical support for the determination of the contents of additives released from MPs in water environment.(2)The release behavior of PAEs from PVC pipe MPs in aquatic environment.Through the release experiments of PAEs from PVC plastic fragments,DMP,DBP and DEHP were detected with high contents.DBP showed a certain release pattern with the first increasing stage until a short equilibrium followed by a second increasing part.The release kinetics and the rate-limiting steps were also discussed.For the whole migration period,the release process was better fitted to Pseudo-second order which was participated by both intraparticle and plastic-water film diffusion processes while the two separated parts had different results.The two separated periods were better fitted to Pseudo-first order,and the first part was controlled by plastic-water film diffusion while the other was the results of intraparticle and plastic-water film diffusions.(3)The factors that influence the release behavior of additives.Under the modelled laboratory conditions,the effects of light,temperature,and plastic size on the release behaviors of additives were also investigated.The three factors can all affect the release rates and amounts,but did not change the kinetic mechanisms.More exposure to light radiation,smaller plastic fragments and higher ambient temperatures all accelerated the aging process of plastic,and thus promoted the release of additive molecules.Among these three factors,the influence of temperature was the most significant,and higher temperature with more significant effects.Through the release behavior of additives from MPs,we can understand the behavior of MPs in environment more comprehensively,which will help assess the risk to environment and the potential influence on biota brought by MPs. |
