First evidence of microplastic contamination in the freshwater of Lake Guaiba, Porto Alegre, Brazil

The ubiquitous presence ofmicroplastics in the aquatic environment has raised concern about their potential impacts on and risks to the biota. While the presence of microplastics in a marine environment has been well studied, the impact ofmicroplastic contamination in freshwater bodies is understudied. In the present study, baseline data about contamination with microplastics in Lake Guaiba in southern Brazil are presented. The abundance, distribution, and composition of microplastics in the surface of this freshwater body were investigated, and these parameters were correlated with population density, land occupation, wind, and geohydrologic processes. The samples were collected with a manta net (60 mu m mesh size). Microplastics were found in all the samples, with an average of 11.9 +/- 0.6 to 61.2 +/- 6.1 items m(-3), which indicates the widespread contamination of the lake with plastic particles. The most frequent microplastic morphology was the fragment type in the size range of 100 to 250 mu m, and the predominant colours were white/transparent and red. Measurement uncertainty of the visual microplastic counts showed that black colour microplastics is more susceptible to be mistaken, whichmight lead to an underestimation and/or overestimation of the total number ofmicroplastics. Polypropylene and polyethylene together comprised most of the polymer types (98%). Micro-Fourier transform infrared (micro-FTIR) spectroscopy analyses showed that 58% of the analysed polymers were highly oxidised, indicating long residence of this particles in the water. In addition, our data show that the distribution of microplastics is strongly influenced by the geohydrological characteristics of the lake. Therefore, this researchmay provide information for further investigations of microplastic distribution in Lake Guaiba and can serve as a base to improve the regulations regardingwaste management to effectively reducemicroplastic pollution in freshwater systems. Additionally, the measurement uncertainty showed that blackmicroplastics aremore susceptible to variations in their measurements. (C) 2020 Published by Elsevier B.V.

Automated summary

This study investigated the contamination of microplastics in Lake Guaiba in southern Brazil and found widespread pollution of the lake with plastic particles. Fragment type was the most common morphology of microplastics, with white/transparent and red being the predominant colors. Additionally, the research indicated that the distribution of microplastics is strongly influenced by the geohydrological characteristics of the lake, emphasizing the need for improved waste management regulations to reduce microplastic pollution in freshwater systems.