Characterization, mapping, and mitigation of mercury vapour emissions from artisanal mining gold shops

Artisanal miners sell their gold to shops that are usually located in the urban core, where the mercury-gold amalgam is burned to evaporate the mercury that was added during ore processing. People living and working near these gold shops are exposed to intermittent and extreme concentrations of mercury vapour. In the urban centres of Segovia, Colombia, and Andacollo, Chile, the average concentrations measured by mobile mercury vapour analyzer transects taken repeatedly over several weeks were 1.26 and 0.338μgm(-3), respectively. By World Health Organization standards, these towns are exposed to significant health hazard, and globally, the millions of miners, as well as non-miners who live near gold shops, are at serious risk of neurological and renal deficits. Measurements taken in Suriname, Ecuador and Peru reveal this to be a widespread phenomenon with unique regional variations and myriad attempts at remediation. Maps of average mercury concentrations show the spatial distribution of the hazard in relation to residential buildings and schools. Measurements from towers show the temporal variability of mercury concentrations, and suggest that large quantities of mercury are available for long-range atmospheric transport. Mercury mapping in Segovia in 2011 suggest a 10% reduction in airborne mercury concentrations over 2010, despite a 30% increase in gold production. This is attributable to the adoption of retorts by miners and regulations banning new processing centres to the rural periphery. This is the first full description of artisanal mining gold shop practices and of the character, quantity, and remediation of mercury emissions within urban mining centres.