Large-scale monitoring and risk assessment of microplastics in the Amazon River

Microplastics (MPs) a iota e one of me most widespread c sigma ntania omega iota ts worldwide, yet their iisks for freshwater ecosystems have seldom been investigated. In this study, we performed a large monitoring campaign to assess the presence and risks o- MPs in Amazonian freshwater ecosystems. We investigated MP pollution in 40 samples collected along 1500 km in the Brazilian Amazon, including the Amazon River, three major tributaries, and several streams next to the most important urban areas. MPs in the 55-5000 gm size range were characterized (size, shape, color) by microscopy and identified (polymer composition) by infrared spectroscopy. Ecotoxicological risks were assessed using chronic Species Sensitivity Distributions for effects triggered by food dilution and tissue translocation using data alignment methods that correct for polydispeisity of environmental MPs and bioaccessibility. This study shows that MPs are ubiquitous contaminants in Amazonian freshwater ecosystems, with measured concentrations (55-5000 gm) ranging between 5 and 152 MPs/m3 in the Amazon River and its main cibutaiies, and between 23 and 74,550 MPs/m3 in urban streams. The calculated Hazardous Concentration for the 5% of species (:105) derived from the SSDs for the entire MP range (1-5000 pm) were 1.6 x 107 MPs/m3 (95% CI: 1.2 x 106 - 4.0 x 108) for food dilution, and 1.E >: 101 MPs/m3 (35a/o CI: 1.5 x 106 - 4.3 z 108) for translocation. Resealed exposure concentrations (1-5000 gm) in the Amazon River and tributmies ranged between 6.0 x 10- and 1.8 x 105 MPs/m3, and were significantly lower than the calculated HC5 values. Resealed concentrations in urban streams ranged between 1.7 x 105 and 5.7 x 108 MPs/m3, and exceeded both calculated HC5 values in 20% of the locations. This study shows that ecological impacts by MP contamination are not likely to happen in the Amazon River and its major tributaries. However, risks for freshwater organisms may be expected in near densely populated areas, such as the cities of Manaus or Belem, which have limited wastewater treatment facilities.

Automated summary

This study investigated the presence and risks of microplastics in Amazonian freshwater ecosystems. Microplastics were found to be ubiquitous contaminants in the Amazon River and its tributaries, with concentrations ranging from 5 to 152 microplastics particles/m3. However, the exposure concentrations were lower than the calculated hazardous concentrations, suggesting that ecological impacts are not likely to occur.