Microplastic acts as a vector for contaminants: the release behavior of dibutyl phthalate from polyvinyl chloride pipe fragments in water phase

The pollution of contaminants brought by plastic fragments is worth paying attention in the study of microplastic. The additives, like phthalates (PAEs), introduced during manufacture, are physically dispersed and can easily release into environment. Polyvinyl chloride pipes are widely used in China, and DBP is also a typical kind of additives in PVC materials. Here, the release behavior of DBP from PVC plastic pipe fragments was investigated in water environment under different conditions. Low-density polyethylene (LDPE) passive sampler was used to monitor the contents of DBP. The curve of DBP concentration started from the first increasing stage until a short equilibrium after 45 days' incubation followed by a second increasing part. The release kinetics and the rate-limiting step were 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. Moreover, light, smaller fragments, and higher temperature could all accelerate the release rate and increase the migration amount of DBP. The effect of temperature was the most significant of all, and higher temperature showed more significant effects. Besides, DBP tended to migrate in a long-time continuously. However, the release of additives will be promoted by various physical and chemical processes in nature compared to laboratory tests. Consequently, microplastic (plastic fragments with sizes smaller than 5 mm) with additives acts as a vector for pollutants, and will bring more threat to both environment and organisms.