Application of a Multivariate Exploratory Analysis Technique in the Study of Dissolved Organic Matter and Metal Ions in Waters from the Eastern Quadrilátero Ferrífero, Brazil

Abstract

Amostras de agua foram coletadas em 10 pontos em trechos do leste do Quadrilatero Ferrifero (QF), que e uma regiao mineira situada no sudeste do Brasil. Os objetivos deste estudo foram encontrar possiveis relacoes entre carbono orgânico dissolvido (COD), metais e outros parâmetros fisico-quimicos medidos utilizando a rede neural de Kohonen como ferramenta para analisar esses dados geoquimicos multivariados na area estudada. As analises fisico-quimicas foram feitas in situ e em laboratorio, onde as concentracoes de COD e varios ions metalicos foram determinadas. A rede de Kohonen permitiu a visualizacao e interpretacao mais amigaveis dos dados, alem de definir relacoes entre eles. Assim, para os dados analisados, foi verificada relacao entre COD e Fe e um possivel efeito da sazonalidade na distribuicao das amostras. Possiveis evidencias litologicas puderam ser detectadas pela analise exploratoria, especialmente se considerados os elementos Ca, Mg, Mn e Sr. Water samples were collected at 10 points in parts of the eastern Quadrilatero Ferrifero (QF), located in a mining region in the southeast of Brazil. The aims of this study were to find possible relationships among dissolved organic carbon (DOC), metals and other parameters measured in the region studied and evaluate the Kohonen neural network as a tool to analyse this geochemical multivariate data set. Physico-chemical analyses were performed in situ and in the laboratory, where concentrations of DOC and a suite of metal ions were determined. The Kohonen neural network allowed an easier visualisation and interpretation of the results and helped to define the relationships among them. In this way, a relationship between DOC and Fe and a possible effect of seasonality on the distribution of the samples were indicated. Signs of lithology were detected in the analyses, especially considering the elements Ca, Mg, Mn and Sr.