GLOBAL MERCURY EMISSIONS FROM GOLD AND SILVER MINING

Mercury has been used in gold and silver mining since Roman times. Wit h the invention of the ''patio'' process in Spanish colonial America, silver and gold were produced in large scale, mostly in the Americas h ut also in Australia, Southeast Asia and even in England. Mercury rele ased to the biosphere due to this activity may have reached over 260,0 00 t from 1550 to 1930, when silver reserves in Spanish colonial Ameri ca were nearly exhausted and Hg-amalgamation was replaced by the mon e fficient 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, involv ing over 10 million people in all continents. Presently, Hg amalgamati on is used as a major technique for gold production in the South Ameri ca especially the Amazon, China, Southeast Asia and in some African co untries. Mercury inputs to the environment from this activity may reac h up to 460 t.yr(-1). Compared with other anthropogenic Hg sources, go ld mining is presently responsible for approximately 10% of the global anthropogenic Hg emissions, but has never been included in global mod els of Hg cycling in the biosphere. Further; most of the Hg released t o the biosphere through gold and silver mining during the last 500 yea rs, roughly 300,000 t, may still participate in the global Hg cycle th rough remobilization from abandoned tailings and other contaminated ar eas.