GOLD MINING ACTIVITIES IN THE AMAZON - CLEANUP TECHNIQUES AND REMEDIAL PROCEDURES FOR MERCURY POLLUTION

Economic and social problems have increased informal mining operations (''garimpos'') in the developing countries of Central America, South America, Asia, Africa and Oceania. South America, in particular the Amazon region, accounts for more than 100 tonnes of gold annually, produced using gravity and amalgamation processes. Although mercury (Hg) is used illegally in these activities at a price five times above the international level, gold recovery by amalgamation is typically above 90% with a cost below 0.02 g of gold per tonne of ore treated. Mercury pollution, occurring at rates of about 1 kg per kg of gold produced, derives from inadequate amalgam distillation practices (80%) and from the dumping of amalgamation tailing into watercourses (20%). More than 1 million informal miners are working in the Legal Amazon Region. Some of the miners who burn amalgam show signs of mercurialism while fish-eating people living some distance from mining activities show high Hg concentrations in blood. Remedial procedures can be viewed from two perspectives: i) clean-up methods for highly polluted sites; ii) education and training of the miners and local population centers. This paper describes the clean-up methods most often used to control mercury pollution including selenium addition, covering polluted sites with adsorbent materials, cementation with iron scrap or dredging operations followed by mercury and residual gold extraction.