Impacts of mining in artificial lake of Iron Quadrangle-MG : past marks and changes of the present.

Abstract

A locus of intense mining activity since the seventeenth century, the Iron Quadrangle, corresponds to one of the most important mineral provinces in the world. Located in Minas Gerais, Brazil, it keeps in its territory marks of past mining activities still in expansion. Such changes, recorded in water bodies of the region’s watersheds, impact not only locally, but also reach adjacent ecosystems as well as those located downstream of mining companies. In this situation, an artificial lake is found in the upper course of the Mata Porcos creek sub-basin. The area was once an old place of gold exploration in the eighteenth and nineteenth centuries, and is currently influenced by active iron mining and inactive iron–manganese mining upstream. With the aim of evaluating this reservoir and contributing to the understanding of lentic systems under the influence of mining, this study analyzed the physical and chemical characteristics of sediments from the bottom of this lake, identifying the possible contributions of anthropic origin. Sediment samples were collected at nine points along two hydrological years and then submitted to granulometric, mineralogical and geochemical analyses. The geochemical signature of this lake is marked by As, Fe and Mn elements associated with both the local geological substrate and anthropic activities undertaken in the surroundings. Due to the high As concentrations, distribution maps were made using the IDW interpolation method to understand the distribution of this potentially toxic element that has a strong correlation with gold mining practiced for more than 300 years at the site.