Deterioração ambiental no estado natural da bacia do Rio Paraopeba, avaliada com Modelagem Caminho de Mínimos Quadrados Parciais.

Abstract

On January 25, 2019, the B1 tailings dam of Córrego do Feijão broke in the city of Brumadinho (Minas Gerais, Brazil), where approximately 2.8 Mm3 of tailings were released into the environment. The advance of the tailings reached the Córrego do Feijão and the Paraopeba River, the main source of drinking water in the region. However, several tributaries that flow into the Paraopeba River were not directly impacted by the accident, maintaining the natural conditions existing in the basin before the event. To characterize the water quality of these tributaries and associate it with the natural deterioration of the basin, we evaluated through partial least squares path modeling (PLS-PM), the intervening variables of a dense set of space-time data (daily to weekly), collected at 7 points in confluence with the Paraopeba River, for the hydrological year 2019. In the Water Quality model, the independent latent variables are "Soil Class" (comprising Latosols), "Occupation in Soil conservation" (comprising Forest, Reforestation). The environmental latent variables are "Water Quality" (comprising Total Alkalinity, Total Magnesium and Dissolved Oxygen) and "Environmental Deterioration" (comprising Fitness/Weight). Thus, it is shown that 51.1% of "Environmental Deterioration" is predicted by "Water Quality", in which deterioration is inversely proportional to quality (β =-0.715), 52.4 % of "Water Quality" is predicted by "Surface Runoff" (β =-0.724), and 80.9% of "Surface Runoff" is predicted by "Soil Class" (β= -0.649) and "Occupancy in Soil Conservation" (β = -0.273). This study made it possible to identify and quantify the intervening variables in water quality and consequent natural environmental deterioration in the tributaries, being a promising method to identify the natural condition of the basin before the occurrence of the dam breach.