Historic Reconstruction of Mercury Releases and Emissions in Costa Rica: a Contribution for Compliance with the Minamata Convention

Abstract

Mercury global distribution is related to harmful effects on human health. As a preventive action, Costa Rica signed the Minamata Convention in 2013. The Convention´s guidelines drive important efforts aiming to mitigate liberations to water and soil, and emissions to the atmosphere. However, mitigatory actions should be complemented with the identification of historic sources of mercury. This implies the identification of activities that used mercury in the past but are no longer practiced; as well as potentially contaminated sites where such activities took place. Potential accumulation of historic mercury might contribute to present liberations and/or emissions. The country lacks records on this kind of historic information. For example, historic registries on gold and silver mining as a state policy at the end of the 19^th century is scarce. Another example is the unavailability of detailed records of land claims intended for mercury extraction. Such lands were supposed to supply mercury locally at a lower cost for amalgamation in the mines. An initial estimation of the amount of mercury used in past activities, or potentially accumulated in specific sites, might contribute to extend the scope of current mitigatory actions in the country. This work summarizes the most important findings on historic activities and sites that used mercury. It also reconstructs the approximate amounts of total elemental mercury potentially released and establishes a baseline of the minimum contributions per activity. Results show seven sites claimed for the extraction of mercury during the colonial period. Gold and silver mining were the activities that contributed with the largest amounts of mercury between 1860 and 1930, followed by a 30-year gap, until 1960. From 1960 to 1992 street lighting in the capital became a new potential source of mercury. A minimum amount of approximately 145 tons of mercury were estimated to be liberated between 1860 and 1992, being gold mining the major contributor.