Microplastics in surface water and surface sediments of the Huangáscar sub-basin in Cañete River, Peru

The Cañete River basin, located in the Lima region of Peru, is an area of intense agricultural activity, the primary socioeconomic source of the valley, and subject to high water demand. In the Huangáscar sub-basin, this activity generates waste, including plastics, which are discharged into creeks and water bodies. Microplastics (MPs) are transported by river flow and accumulate in sediments along the channel. This study aimed to determine the abundance and predominant characteristics of MPs in terms of size, color, and shape in surface water and sediments of the Huangáscar River. Samples were collected from nine sites (SH-1 to SH-9) and analyzed in the laboratory. MP abundance in surface water ranged from median values of 55 to 170 items/m³, while in surface sediments it ranged from 133.33 to 800 items/kg of dry sediment. No significant differences were found in MP abundance in surface water. However, a significant difference was observed in sediments between sites SH-01 and SH-03. Correlation analysis did not show a relationship between MP concentrations in water and sediment. The predominant characteristics of MPs were sizes < 1 mm (60.64 % in water; 5.44 % in sediments); blue color (54.19 % in water; 56.38 % in sediments), and fiber shape (61.72 % in water; 66.43 % in sediments). It is concluded that MP presence in the sampling sites was low, with particles predominantly small, blue, and fibrous, both in surface water and sediments.