Spatial–Temporal Distribution and Ecological Risk Assessment of Microplastic Pollution of Inland Fishing Ground in the Ubolratana Reservoir, Thailand

Microplastic pollution has been identified as a potential threat to the aquatic environment and humans globally, with widespread occurrence in ecosystems, including reservoirs that constitute a key role in ecosystem services for humans. However, the evaluation of microplastic pollution in reservoirs is limited, especially in inland fishing ground reservoirs. The spatial and temporal distributions of microplastics in surface water and sediment at 13 stations of the Ubolratana Reservoir, Thailand, were assessed during the wet and dry seasons. The abundance and morphological characteristics of the microplastics were identified and classified by color, shape, size and polymer type. Microplastic abundance in surface water and sediment ranged between 25 and 3363 particles/m3 and 6 and 81 particles/kg, respectively. Seasonal variations impacted microplastic abundance in surface water, while tourism activity in the reservoir also influenced the abundance and morphological characteristics of microplastics. A microplastic risk assessment showed that the pollution load index reached extremely high levels in surface water during the dry season in tourist areas. The results provide a database to assess the risk of microplastic contamination and to monitor plastic pollution in lentic ecosystems, including preserving the health of aquatic habitats.