Microplastics contamination in the proximities of a water treatment station for human supply: Guandu River (Brazil)

Microplastics (MPs) are emerging contaminants (i.e., not commonly monitored or eliminated in drinking or waste treatment process, and present potential risks to environmental or human health). This study assessed MPs contamination in Guandu river, the largest source of freshwater supplying the water treatment station that serves the population of Rio de Janeiro metropolitan region (Brazil). Sampling was conducted using a Manta trawl, with a net mesh size of 68 μm, deployed from the side of a motorized vessel. Two independent samplings with a flowmeter coupled in the trawl were conducted in five areas at lower Guandu region (proximities WTS) after dry and rainy seasons. MPs extraction steps were performed using KOH and H2O2 solutions at low temperature (40°C), followed by density separation. Procedures to prevent cross contamination were performed, as well as procedural blanks and control membranes. No microplastic particle was detected in blanks (n = 5) and controls (n = 5). For the first time, MPs were detected in surface waters of Guandu river ranging from 0.008 to 0.015 MPs L-1 ( = 0.006 ± 0.004). Significant differences in MPs were detected for areas (PERMANOVA, F(4,19)= 12.09, p= 0.001), seasons (PERMANOVA, F(1,19)=5.73, p=0.015) and interaction area*season (PERMANOVA, F(4,19)= 2.86, p= 0.035). Samples collected after dry season showed significantly higher concentrations compared to post-rainy season. Pronounced differences in MPs concentrations among seasons were detected in more lentic areas (no water flow) and a lotic area (i.e., high water flow). MPs were classified in five shapes and twelve colors. Fragments (57-83 Also see: https://micro2024.sciencesconf.org/559197/document