Quantificação e avaliação ambiental da contaminação por metais e arsênio em sedimentos da bacia do Rio Doce - MG

Exportado OPUSMade available in DSpace on 2019-08-10T23:26:58Z (GMT). No. of bitstreams: 1 tese_impress_o_final.pdf: 3943999 bytes, checksum: de3bcc4d13b8aef92b4fc44d93385ca5 (MD5) Previous issue date: 26A bacia hidrográfica do Rio Doce (BHRD) situa-se na região sudeste do Brasil, e várias atividades econômicas são desenvolvidas em toda sua extensão, como mineração, agropecuária e indústria alimentícia. A atividade de mineração engloba a exploração de vários minerais, além de atividades de garimpo de ouro, nas quais se utiliza mercúrio para aumentar a eficiência de extração. A qualidade das águas na bacia é monitorada desde 1997 pelo órgão estadual de controle ambiental. No entanto, existem poucas publicações relatando análise de metais e As nos sedimentos da bacia. Neste trabalho foram investigados 8 metais e As nos sedimentos de 19 pontos da BHRD, em três diferentes períodos de coleta. O estudo foi dividido em cinco etapas para a melhor avaliação ambiental da bacia. Na primeira etapa foi realizada a caracterização físicoquímica dos sedimentos, identificando os mesmos como de característica arenosa e mineral, ricos em aluminossilicatos e oxi-hidróxidos de Fe e Mn, apresentando baixa capacidade de troca catiônica. Na segunda etapa foram determinadas as concentraçõestotais dos elementos Al, As, Cr, Cu, Fe, Hg, Mn, Ni e Zn, além de parâmetros físicoquímicos como pH, matéria orgânica e % fração < 63 um. Observou-se que 47% do total de amostras coletadas encontraram-se acima dos limites de qualidade para sedimentos estabelecidos pela Resolução CONAMA nº344/2004, com destaque para o elemento Cr, de forma generalizada na bacia. A extração parcial com HCl 1 mol L-1 a frio foi realizada na 3ª etapa, para identificação da disponibilidade ambiental dos elementos investigados, tendo os metais Cu, Mn e Zn apresentado as maiores labilidades nos pontos da BHRD. A quarta etapa envolveu a avaliação ambiental da BHRD, através de parâmetros geoquímicos e análises quimiométricas dos dados. Os parâmetros geoquímicos de qualidade de sedimentos índice de geoacumulação (Igeo) e fator de enriquecimento (FE) foram calculados, identificando Cr, Cu, Ni e Zn como possivelmente provenientes de fontes antropogênicas de contaminação, de uma forma geral na BHRD, e As em pontos localizados. As análises estatísticas de Análise de Componentes Principais (PCA) e Análise Hierárquica de Agrupamentos (HCA) identificaram o Zn como proveniente de despejos de efluentes nos rios da bacia, As e Hg associados a oxihidróxidos de Fe e Mn e Ni, Cr e Cu a argilominerais contendo Al. Por fim, na quinta etapa a especiação qualitativa por termodessorção acoplada a absorção atômica (TDAAS) e quantitativa por Analisador Direto de Mercúrio (DMA) foi realizada, sendo verificada a predominância de espécies oxidadas de Hg na BHRD, com alguns pontos contendo relevante quantidade de espécies reduzidas, indicando contaminação recente por Hg elementar. De maneira geral, os sedimentos da BHRD são impactados por Cr, Cu, Ni e Zn, além de As e Hg de forma localizada. Através do estudo pode-se identificar que dez pontos, dentre os 19 pontos selecionados, foram considerados os mais impactados da BHRD, devido aos elementos investigados, em diferentes combinações e proporções.  The Doce River Basin (DRB) is located in southeastern Brazil, and several economic activities are performed along its entire length, including mining, agriculture and food industry. The mining activity involves the exploration of a range of minerals, in additionto gold mining in which mercury is used to increase the extraction efficiency. The quality of water in the basin has been monitored since 1997 by the state agency for environmental control. However, there are few publications about metals in sediments of this basin. This work investigated 8 metals and As in sediments from19 points of DRBin three different sampling periods. The study was divided into five steps for better environmental assessment of the basin. In the first stage, it was carried out physicochemical characterization of the sediments, identifying them as sandy mineral, rich in aluminosilicate and oxy-hydroxides of Fe and Mn, with low cation exchange capacity. In the second step, it was determined the total concentrations of the elements Al, As, Cr,Cu, Fe, Hg, Mn, Ni and Zn, and physical and chemical parameters. It was observed that 47% of determinations are above the acceptance limits for sediment established by national Resolution CONAMA nº 344/2004, especially for Cr, across all basin. The partial cold extraction with 1 mol L-1 HCl in the Step 3 was performed to identify the availability of environmental factors investigated, with the metals Cu, Mn and Zn appear larger in labilities of DRB points. The fourth step involved the environmental assessment of DRB through geochemical parameters and chemometric data analysis. The geochemical parameters quality, geoaccumulation index (Igeo) and enrichment factor (EF), werecalculated identifying Cr, Cu, Ni and Zn as possibly from anthropogenic sources of contamination, generally in DRB, and As in localized points. Statistical analysis using PCA and HCA identified Zn from waste dumps in the basin rivers, As and Hg associated with oxy-hydroxides of Mn and Fe, and Ni, Cr and Cu in clay containing Al. Finally, in the fifthstep the qualitative and quantitative speciation of Hg was performed by TDAAS and DMA, verifying the predominant species in the oxidized form in DRB, with a few spots containing relevant amount of reduced species, indicating contamination by recent elementary Hg. In general, DRB are impacted by Cr, Cu, Ni and Zn, and As and Hg localized. Through this study, ten points of the basin were considered the most affectedby the investigated elements, in different combinations and ratios

Speciation and quantification of Hg in sediments contaminated by artisanal gold mining in the Gualaxo do Norte River, Minas Gerais, SE, Brazil.

The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particularinterest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CH3Hg+) concentrations in samples ranged from 209 to 1207 ?g kg?1 and from 0.07 to 1.00 ?g kg?1, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CH3Hg+ are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fund?o Dam disaster. The results are also a record of the characteristics of the sediment prior to that event

Speciation and quantification of Hg in sediments contaminated by artisanal gold mining in the Gualaxo do Norte River, Minas Gerais, SE, Brazil

The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particularinterest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CH3Hg+) concentrations in samples ranged from 209 to 1207 ?g kg?1 and from 0.07 to 1.00 ?g kg?1, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CH3Hg+ are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fund?o Dam disaster. The results are also a record of the characteristics of the sediment prior to that event