Estimating Losses of Mercury to the Environment

Abstract

The release of mercury from gold and silver mining is of great environmental significance, since this process of mining and production of precious metals is known to be of very low efficiency (Mallas and Benedicto 1986; Souza and Lins 1989; Nriagu 1993b). Correct estimates of the total amount of Hg released to the environment from these semi-artisanal mining processes, however, are very difficult to obtain. Gold and silver, on the other hand, are very precious metals and even in Roman times the quantities produced were carefully noted. Therefore, if the steps in the production and the Hg losses in each step are known, one could estimate more accurately the amount of Hg released into the environment using gold and silver production figures. Emission factors (EF), i. e. the amount of Hg released into the environment to produce 1.0 kg of silver or gold, are quite variable, depending on site, metal-containing material and concentration, and the extraction process used (Farid et al. 1991).