Longitudinal, vertical, and temporal distribution of microplastics in Igarapé do Mindu in Manaus, Amazonas

Abstract

The incorrect disposal of plastic materials in the environment, especially in water bodies, where they are exposed to different environmental conditions for long periods, favors fragmentation and originates debris called microplastics (< 5 mm). These are present in different environmental matrices. In freshwater environments, such as rivers and streams, microplastic pollution is influenced by urban concentration, hydrodynamics, and riparian vegetation. To demonstrate contamination by microplastics in the Mindu creek, in Manaus, water samples collected from two profiles (surface and depth) were analyzed according to the hydrological regime of the Negro River (CPRM, 2020) under the Cetesb (2011) and Masura et al. (2015) methodologies. The results confirmed the microplastic pollution in the waters of the Mindu creek with concentrations in greater evidence for the depth profile (0 to 0.40 g.L-1) compared to the surface profile (0 to 0.12 g.L-1) and an emphasis on the flood and full hydrological regimes. As for the qualitative characteristics, the Fourier transform infrared spectroscopy (FTIR-ATR) analysis, whose objective is to identify absorption bands (cm-1) of virgin polymer molds, returned eight polymeric compounds, among which elastomers, monomers, wetting agents and surfactants used in the manufacture of plastic materials. These characterizations highlight the negative impacts of microplastics on water bodies, reinforced through the release of these compounds into the environment. It emphasizes the need for further studies in urban water bodies on the inherited consequences of the interaction between microplastics and the biotic and abiotic components of the environment.