The Distribution and Characteristics of Microplastics in Coastal Beaches and Mangrove Wetlands

Abstract

Microplastics found in coastal environments can be transported to and accumulate in different coastal environmental media by diverse driving factors and pathways. Increasing numbers of studies indicate that microplastics accumulate in coastal areas with highly intensive human activities. However, there are few discussions on the occurrence of microplastics in coastal sediments and coastal wetlands according to different land utilization patterns. In this chapter we investigate the distribution of shape, size, and abundance of microplastics in northern coastal beach sediments. We found that pellets, foams, fragments, flakes, films, fibers, and sponges occurred in beach sediments with different land utilization patterns. The abundances of microplastics were 344 particles kg−1 in tourist beaches, 1,226 particles kg−1 in beaches adjacent to mariculture areas, 98 particles kg−1 in beaches near fishing ports, and 1,302 particles kg−1 in undeveloped beaches. Foams were dominant in tourist beaches and beaches near fishing ports, while flakes dominated in beaches adjacent to mariculture areas and in undeveloped beaches. The differences are likely due to different anthropogenic influences in coastal zones. We then illustrate the characteristics and spatial distribution of microplastics in different mangrove sediments covering the main mangrove forest growing areas of south China. The abundance of microplastics was 1,302 particles kg−1, and foams and fibers were the dominant shapes in mangrove sediments. The differences in distribution of microplastics in mangrove sediments are related to anthropocentric influences such as mariculture and fisheries and to the density of vegetation. Moreover, different potential sources of microplastic are contributors of microplastic pollution in coastal zones and need to be evaluated. They include land sources and offshore marine sources together with coastal atmospheric deposition. The results contribute to our understanding of microplastic pollution in coastal sediments with different coastal land utilization patterns, and they provide a reference for the management and control of microplastic pollution in coastal environments.