Sorption And Desorption Of Polyhalogenated Carbazoles(PHCZs)to Microplastics In Marine Environment

Microplastics and organic pollutants are two typical pollutants in the marine environment,and it is the key to assess the environmental risk whether they produce double toxic effects on the marine environment and marine life when microplastics and organic pollutants coexist.In addition to the pollution of microplastics itself to the ocean,as a carrier,it also has enrichment and migration effect on organic pollutants,causing changes in the spatial and temporal distribution of organic pollutants in the ocean.Therefore,The sorption of organic pollutants by microplastics has become a hot topic in Marine environment.Batch equilibrium experiments were conducted to investigate sorption characteristics of five Polyhalocarbazoles?3,6-dibromocarbazole?3,6-BCZ?,3,6-dichlorocarbazole?3,6-CCZ?,3,6-diiodocarbazole?3,6-ICZ?,2,7-dibromocarbazole?2,7-BCZ?and 3-bromocarbazole?3-BCZ??on polyethylene?PE?,polypropylene?PP?and polyvinyl chloride?PVC?.On the other hand,microplastics can adsorb and desorb organic pollutants and are easily taken up by marine organisms,which will seriously endanger the health of marine organisms.Therefore,in order to verify whether the microplastics ingested by marine organisms play the role of cleaner or polluter in the stomach,two microplastics?PP,PVC?were selected,and six Polyhalocarbazoles?carbazole?CZ?,3,6-BCZ,3,6-CCZ,2,7-BCZ,2-bromocarbazole?2-BCZ?and 1,3,6,8-tetrabromocarbazole?1,3,6,8-BCZ??were used as target substance to study the mechanism of the desorption process.The experimental results can provide a theoretical basis for the transfer and transformation of Polyhalocarbazole in the serious area of marine microplastic pollution.It also provides basic data for marine organisms feeding on microplastics and Polyhalocarbazole.The main results are as follows:?1?Sorption experiment.Sorption isotherms demonstrated that PVC had the maximum sorption capacity,As the octanol water distribution coefficient(log K_OW)of the five Polyhalocarbazoles is less than 6,the sorption effect of PVC with relatively large polarity is the strongest.The sorption kinetics model showed that the sorption process was controlled by both intraparticle and film diffusion.The sorption of Polyhalocarbazoles to microplastics was significantly influenced by temperature,the sorption capacity first increasd gradually and then decreased with the increasing temperature.Increasing the salinity decreased the sorption of Polyhalocarbazoles onto PP,PE,PVC microplastics.Our results indicated that all three kinds of microplastics can serve as carriers for Polyhalocarbazoles in the aquatic environment,which put marine ecosystems at higher risks.?2?Desorption experiment.Our experiment showed that chemical transfer is biphasic and reversible,with rapid exchange within hours and then slow transfer for weeks to months.The results showed that the bioavailability of 0.15 mm microplastics is higher than that of 5mm microplastics.the amount of polyhalocarbazoles desorbed from the PVC microplastic in the gastric fluid of vertebrates was smaller than that of invertebrates,indicating that different physiological conditions will affect the desorption experiment,but it did not have a great impact on PP,indicating that the digestive juice conditions have different effects on different microplastics.When food was present,the desorption of PP was inhibited due to competition,while the desorption amount of PVC was increased.The clean microplastics had a cleaning effect in contaminated gastric systems,which was capable of extracting polyhalocarbazoles from food in the gastric fluid.