Estimation of mercury released from an abandoned gold mine in Minas Gerais, Brazil.

Abstract

Mining is very important to the economic, political and social development of the Minas Gerais State in Brazil ever since the time the country became a Portuguese colony in the early 1500s. However, few researches have been conducted to evaluate the environmental impacts associated with the mining activity at this time. There are many abandoned mines in Minas Gerais; these are mainly gold mines inherited from the colonial period, which have been considered to represent a considerable environmental liability. However, when a road was constructed in a rural area of the municipality of Descoberto, Minas Gerais, in 2002, a significant amount of mercury was detected in an abandoned gold mine. In 2014, the State Public Prosecutor’s Office found both the State of Minas Gerais and the State Environmental Agency liable and responsible for this occurrence and ordered them to design an intervention project for the contaminated area that involved mine closure. This article provides information on how mercury contamination occurred and estimates the amount of mercury present in the contaminated area, with the aim of supporting proposals of alternative remediation, monitoring and management therein. This study includes a historical survey of mining operations in the region and a brief history of the use of mercury in amalgamation. Estimations are made of the amount of gold produced and the amount of mercury released into the environment between 1850 and 1892. Results show an estimated mass of 820 kg of mercury contained in soils and sediments within an area smaller than 1 hectare.