An Enlarging Ecological Risk: Review on Co-Occurrence and Migration of Microplastics and Microplastic-Carrying Organic Pollutants in Natural and Constructed Wetlands

Wetlands are a key hub for the accumulation of microplastics (MPs) and have great load capacity to organic pollutants (OPs), thus, have been a hot research topic. It has shown that OPs adsorbed on MPs could be transported to anywhere and MP-associated biofilms also affects the co-occurrence of MPs and OPs. This would induce the desorption of MP-carrying OPs into environment again, increasing latent migration and convergence of MPs and OPs in wetlands. Considering MPs vector effect and MP-associated biofilms, it is necessary to integrate MPs information on its occurrence characteristics and migration behavior for an improved assessment of ecological risk brought by MPs and MP-carrying OPs to whole wetland ecosystems. In this review, we studied papers published from 2010 to 2020, focused on the interaction of MPs with OPs and the role of their co-occurrence and migration on ecological risk to wetlands. Results suggested the interaction between MPs and OPs dominated by adsorption altered their toxicity and environmental behavior, and the corresponding ecological risk induced by their co-occurrence to wetlands is various and complicated. Especially, constructed wetlands as the special hub for the migration of MPs and MP-carrying OPs might facilitate their convergence between natural and constructed wetlands, posing a potential enlarging ecological risk to whole wetlands. Since the study of MPs in wetlands has still been in a primary stage, we hope to provide a new sight to set forth the potential harm of MPs and MP-carrying OPs to wetlands and useful information for follow-up study.