Abstract
Acid mine drainage (AMD) is one of the main environmental issue caused by chemical and bacterial oxidation of pyrite (FeS2) and other sulfite minerals when exposed to atmospheric conditions during mining. In Brazil, AMD occurs in a former uranium mine and contains radionuclides and other elements, which are precipitated from acidic water by liming. Due to the inefficiency of the treatment, contaminants overflow to the water reservoir of Indústrias Nucleares do Brasil – INB in Caldas. The multiplicity of interactions that can occur between the contaminants and the sediments of the reservoir requires a broader approach in order to understand the fixation and/or transport of these elements. In this work the natural remediation approach is reviewed and an initial chemical and radiochemical characterization of the reservoir sediments is presented. Uranium was determined by spectrophotometry, Ra-226, Ra-228 and Pb-210 by gamma spectrometry and zinc by ICP-OES. Twenty-six sediment samples were collected in the reservoir and a bathymetry survey by sonar was performed to determine the thickness of the sediment layer. All the data were processed using the ArcGIS program. To assess the potential mobility and bioavailability of contaminants and to study the role of bacterial sulfate reduction in the immobilization of these contaminants, Acid-volatile sulfide (AVS) analyzes will be performed as a further step.
Highlights
Mining is a strategic activity in the world economy and has its importance recognized for the development of Brazil, which is one of the main exporters of several minerals
This study investigated the sediments of one water reservoir, highly affected by uranium mining activities, in order to determine the capacity of the system to undergo natural attenuation
Twenty-six sediment samples were collected in different points including the point of discharge of the treated water and two background points upstream of the water reservoir
Summary
Mining is a strategic activity in the world economy and has its importance recognized for the development of Brazil, which is one of the main exporters of several minerals. If appropriate environmental practices are not adopted, mining activities could be sources of inorganic contamination [1]. One environmental problem of great concern is acid mine drainage (AMD). It is caused mainly by oxidation of pyrite (FeS2) when exposed to air and water during the mining process causing the generation of acidity (H+). AMD sources include waste rock piles, ore stockpiles, tailings storage facilities and tailings dams, open cuts, underground mines and heap and dump leach piles. This problem is not exclusive to mining activities and can occur in any operation that results in a large movement of soil and rocks containing FeS2. The focus should be on prevention or minimization rather than on treatment [3]
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