ASGM Mercury Discharges in Tropical Basins: Assessment of the Criticality of Their Geographical Distribution

Abstract

The global-scale impacts of mercury discharged from Artisanal Small-scale Gold Mining (ASGM) on soils have been poorly studied, unlike atmospheric emissions. This is a key point to understand the potential exposure to mercury pollution of ecosystems and populations living in the river basins where ASGM is practiced, since the largest fraction of the pollutant is poured into soil, independently of the amalgamation technique employed. ASGM activities emit into the atmosphere mercury in its elemental form, which reacts very slowly with the major oxidants. Therefore, the exact location of the ASGM sites has a limited impact on the atmospheric mercury fate. Conversely, this cannot be applied to the mercury discharged on top of the soil. Two ASGM inventories and the related distributions available in the literature along with two novel distributions based on the intersection of zones characterized by low population density and rural areas were compared using a newly introduced Vulnerability Index. The results from this comparison showed that a precise distribution of ASGM is crucial to effectively evaluate the fate of mercury, and therefore the resulting effects on the local ecosystems.