Global Mercury Emissions from Gold and Silver Mining

Abstract

Mercury has been used in gold and silver mining since Roman times. With the invention of the "patio" process in Spanish colonial America, silver and gold were produced in large scale, mostly in the Americas but also in Australia, Southeast Asia and even in England. Mercury released to the biosphere due to this activity may have reached over 260,000 t from 1550 to 1930, when silver reserves in Spanish colonial America were nearly exhausted and Hg-amalgamation was replaced by the more efficient cyanidation process. Exceptional increases in gold prices and the worsening of social-economic conditions in the third world in the 1970's, resulted in a new gold rush in the southern hemisphere, involving over 10 million people in all continents. Presently, Hg amalgamation is used as a major technique for gold production in the South America especially the Amazon, China, Southeast Asia and in some African countries. Mercury inputs to the environment from this activity may reach up to 460 t.yr- 1. Compared with other anthropogenic Hg sources, gold mining is presently responsible for approximately 10% of the global anthropogenic Hg emissions, but has never been included in global models of Hg cycling in the biosphere. Further, most of the Hg released to the biosphere through gold and silver mining during the last 500 years, roughly 300,000 t, may still participate in the global Hg cycle through remobilization from abandoned tailings and other contaminated areas.