Contribution of Spanish–American silver mines (1570–1820) to the present high mercury concentrations in the global environment: a review

In this review I evaluate the contribution of Spanish–American silver mines during the period 1570–1820 (a Spanish colonial period of 250 years) to the present high mercury concentrations in the global environment. The evaluation is based upon the following bibliographic information: (1) total amount of mercury consumed in Spanish–American silver mines between 1570 and 1820; (2) percentage of the total amount of mercury consumed in Spanish–American silver mines that may have been emitted to the atmosphere; (3) global natural input of mercury to the atmosphere; (4) world-wide anthropogenic emissions of mercury to the atmosphere; (5) residence time of mercury in the atmosphere; and (6) capacity of mercury to be deposited in the sediments of aquatic systems. From all this information, and owing to the relatively long time that has passed since Spanish–American silver mines were operational, I conclude that most of the mercury lost during the refining of silver via the patio amalgamation process is now sequestered into the sediments of aquatic systems, mainly in marine sediments. The high mercury concentrations now being reported in the global environment essentially are a consequence of the huge pollution caused by human activities during the past 20th century.