Microplastic contamination in surface water and sediments of Lake Canaçari, Central Amazon, during the dry season

Abstract Contamination by microplastics is an emerging environmental problem that is widely distributed across continental aquatic environments and may cause ecological impacts. This study evaluated the occurrence, concentration, and chemical and morphological characteristics of microplastics in surface waters and sediments from Lake Canaçari, comparing two areas with different land-use patterns within a floodplain system in the Central Amazon. Microplastics were detected in all sampled areas. In surface water, concentrations ranged from 0 (no microplastic particles detected in one sample) to 1,000 microplastics·m⁻ 3 (405 ± 298 microplastics·m⁻ 3 ), while in sediments, they ranged from 7 to 307 microplastics·kg⁻ 1 (77 ± 104 microplastics·kg⁻ 1 ). No significant differences in microplastic concentrations were observed between fishing and human-settlement areas. The particles were predominantly blue fibers (< 1,000 μm). Among the spectroscopically analyzed particles, polyethylene was the most frequently identified polymer, while copper phthalocyanine pigments, including Pigment Blue 15 and Pigment Green 7, were also detected by FTIR and/or Raman spectroscopy. Overall, the results suggest that Lake Canaçari may act as a transport pathway, redistribution zone, and retention compartment for microplastics; however, seasonal sampling is needed to confirm how these processes vary throughout the hydrological cycle. These results reinforce the role of Amazonian floodplain systems in the regional dynamics of microplastics and highlight the need for monitoring and management strategies that incorporate seasonal hydrological connectivity at the basin scale.