Occurrence and Characteristics of Microplastic Pollution in Xiangxi Bay of Three Gorges Reservoir, China

TLDR

Microplastic pollution in inland waters is increasingly recognized, yet reservoirs—particularly the Three Gorges Reservoir tributaries—remain poorly characterized in terms of microplastic abundance and distribution. The study aimed to map the distribution and characterize the types of microplastics in the backwater area of the Xiangxi River, a key tributary of the Three Gorges Reservoir. Researchers sampled surface water and sediment in the Xiangxi River backwater, quantified microplastic concentrations, identified polymer types, and examined correlations with water quality and hydrodynamic variables. Microplastics were found in surface water and sediment (0.55–342 × 10⁵ items km⁻² and 80–864 items m⁻²), mainly polyethylene, polypropylene, polystyrene, and PET, and were present in 25.7 % of fish guts, with concentrations weakly linked to water quality but negatively correlated with reservoir water level and Secchi depth, indicating that hydrodynamics and nonpoint inputs drive accumulation.

Abstract

Microplastic pollution in inland waters is receiving growing attentions. Reservoirs are suspected to be particularly vulnerable to microplastic pollution. However, very limited information is currently available on pollution characteristics of microplastics in reservoir ecosystems. This work studied the distribution and characteristics of microplastics in the backwater area of Xiangxi River, a typical tributary of the Three Gorges Reservoir. Microplastics were detected in both surface water and sediment with concentrations ranging from 0.55 × 105 to 342 × 105 items km-2 and 80 to 864 items m-2, respectively. Polyethylene, polypropylene, and polystyrene were identified in surface water, whereas polyethylene, polypropylene, and polyethylene terephthalate, and pigments were observed in sediment. In addition, microplastics were also detected in the digestion tracts of 25.7% of fish samples, and polyethylene and nylon were identified. Redundancy analysis indicates a weak correlation between microplastics and water quality variables but a negative correlation with water level of the reservoir and Secchi depth. Results from this study confirm the presence of high abundance microplastics in reservoir impacted tributaries, and suggest that water level regulated hydrodynamic condition and input of nonpoint sources are important regulators for microplastic accumulation and distribution in the backwater area of reservoir tributaries.