Speciation, distribution, and transport of mercury in contaminated soils from Descoberto, Minas Gerais, Brazil

Abstract

This work describes an investigation of mercury contamination in an abandoned gold mining site in the rural area of Descoberto, Minas Gerais, Brazil, whose inhabitants have reported “silver balls” present in the soil. Different granulometric fractions of soil samples and sedimented material from rainwater retention tanks in this area were analyzed for total mercury, organic matter, and mercury speciation by thermodesorption/atomic absorption spectrometry. The results showed mercury concentrations in the soils in the range of (0.0371–161) mg kg⁻¹, and the occurrence of Hg⁰ oxidation. Some samples had concentrations as high as 90 mg kg⁻¹ with the majority as Hg²⁺, which is important information in order to understand the biogeochemical behavior of mercury in contaminated sites and to apply the appropriate remediation technology. The retention boxes and tank samples showed that fine particles with high mercury content (3.3–90) mg kg⁻¹ are leached from the contaminated area, which reveals the need for efficient control of this material to prevent the contamination of stream waters. This study is an example that may be useful for other contaminated sites.