Análise geoquímica de metais pesados em sedimentos de corrente na represa da CEMIG - Três Marias/MG: distribuição e influência dos processos naturais e antropogênicos

Abstract

The contamination of water bodies and their sediments is universal environmental adversity. The potentially toxic elements flows are a hazardous mechanism that transfers contaminants for the biosphere and the anthroposphere and consequently bringing massive ecological damage. In this scenario, constant assessment and monitoring of environmental processes to maintain the specificities of ecosystems becomes crucial. Environmental geochemistry evaluations should consider the trace elements concentration at sediments regarding all potential sources for it, even if it is a geogenic or an anthropogenic one. This research took as main goal to evaluate bottom sediments geochemistry in Três Marias reservoir – Minas Gerais – Brazil. The study area has crucial social and economical relevance in a national scale.There also is a very economically diversificate area. The area under study has high socioeconomic relevance on a national scale. Also, it has a wide variety of anthropogenic practices such as agriculture, livestock, fishing, fish farming, waterway transport, tourism, hotels, and forestry that can impact the environmental quality of the area. In February 2019, the most significant environmental South America hazard happened in Três Maria's vicinity. A rupture on a mining dam in Brumadinho – Minas Gerais throw tonnes of Fe water waste on Paraopeba river, one of the main Três Marias tributaries. The following results show a preterit ecological evaluation of Brumadinho's break down. The field trip was divided into two campaigns considering seasonal criteria, sampling a total of 78 sediments along the reservoir. The fine particle size (<0.063mm) was submitted to a single extraction with HNO3 following the USEPA-3051a method. Using an ICP-AES, the Fe; Al, Mg, Ca, Mn, Cr, Cu, Co, Cd, Ni, Pb, Zn, Ba. and Ti concentrations were measured. Data exploration were performed through box-plots, outliers evaluation, Spearman correlation rank, and factorial analysis using centered-log transformed data. Loading matrices concomitantly with multielementary geochemical mapping indicates three main geological structures that control the supply of sediments in Três Marias: Bambuí Group, Mata da Corda formation and Latossoils adjacent the reservoir. The trace elements evaluation was executed through geoaccumulation index, enrichment factor, contamination factor, degree of contamination, and using CONAMA 454/2012 as guidelines. Overall, Três Marias has acceptable environmental quality; however, exist punctual sources of pollution that should be monitored to ensure the maintenance of the ecosystem characteristics.