Distribution characteristics and transport pathways of soil microplastics in coral reef islands with different developmental stages and human activities

Microplastics have attracted substantial attention on remote coral sand islands owing to their delicate ecosystems. However, the distribution, transport pathways, and control mechanisms of soil microplastics on these islands are yet to be elucidated. The coral reef islands of China's Xisha Archipelago in the South China Sea are at varying stages of development and experience differing levels of human activity, rendering them an ideal location to investigate the environmental characteristics of microplastics. This study conducted a comparative analysis of the distribution characteristics of microplastics in surface soils and beach sands, which were collected from coral cays and islands. We further analyzed the potential impacts of plant cover, geomorphology, soil environmental factors and human activities on accumulation and transport of microplastics. The results show that their abundance varies from 1068 to 1616 particles/kg on the different reef islands. Total organic carbon and dissolved organic carbon in the soils exert a significant influence on the accumulation of microplastics. The abundance of microplastics in the exposed areas showed an increasing trend with the degree of island development, and the human activities have a significant impact on the distribution of microplastics across the islands. Analysis of the microplastic abundance at different locations of the atoll reveals that ocean currents and monsoons are the primary drivers of microplastic accumulation on the coral reef islands. This study provides a scientific basis for the management of microplastic pollution and environmental conservation on remote islands.