Reinforced human intervention drives microplastic pollution in estuarine beaches and nearshore sediments of Dongshan Bay, China

Abstract

Sediments are generally recognized as a critical source and sink of microplastics (MPs), yet sedimentary MPs in the coastal areas are relatively overlooked. This study investigated MP pollution in estuarine beaches and nearshore sediments in Dongshan Bay in Southeastern China. The 23 sampling sites encompass the mangrove zone, west coast, south coast, east coast, and shipping-lane zone. MPs were evaluated by abundance, size, shape, color, composition, and morphology using microscopic identification, micro-Raman spectroscopy, and scanning electron microscopy. The abundance of MPs in surface sediments across Dongshan Bay manifested spatial heterogeneity, ranging from 31 to 971 items per kg d.w. The prominent concentration of MPs in the mid-west coast seemed to be driven by reinforced human intervention, namely, a giant facility under construction in the vicinity of the west coast. The major shape, color, and type of MPs were fiber, white and black, PES, PET, and PS, respectively. Friction, abrasions, scratches, and depressions were often present at the surfaces of MPs. The distribution patterns and hotspots of sedimentary MPs mirrored profound human footprints. This study provided insights into the assessment of estuarine ecosystem vulnerability and mitigation strategies against pressing sedimentary MP issues.