Sources and distribution of microplastics in China's largest inland lake – Qinghai Lake

Highlights: • Microplastics are detected in water, sediment, and fish samples collected from Qinghai Lake. • Microplastics is more abundant in Qinghai Lake than the inflowing rivers. • High microplastic abundance near the tourist sites implies tourism as an important contributor. • Microplastic distribution in the lake is influenced by lake current. Microplastic pollution was studied in China's largest inland lake – Qinghai Lake in this work. Microplastics were detected with abundance varies from 0.05 × 10⁵ to 7.58 × 10⁵ items km⁻² in the lake surface water, 0.03 × 10⁵ to 0.31 × 10⁵ items km⁻² in the inflowing rivers, 50 to 1292 items m⁻² in the lakeshore sediment, and 2 to 15 items per individual in the fish samples, respectively. Small microplastics (0.1–0.5 mm) dominated in the lake surface water while large microplastics (1–5 mm) are more abundant in the river samples. Microplastics were predominantly in sheet and fiber shapes in the lake and river water samples but were more diverse in the lakeshore sediment samples. Polymer types of microplastics were mainly polyethylene (PE) and polypropylene (PP) as identified using Raman Spectroscopy. Spatially, microplastic abundance was the highest in the central part of the lake, likely due to the transport of lake current. Based on the higher abundance of microplastics near the tourist access points, plastic wastes from tourism are considered as an important source of microplastics in Qinghai Lake. As an important area for wildlife conservation, better waste management practice should be implemented, and waste disposal and recycling infrastructures should be improved for the protection of Qinghai Lake.