Method for mapping Hg0 emissions from gold shops in artisanal and small-scale gold mining communities

Miners add elemental mercury (Hg 0 ) to amalgamate gold directly to the ore prior to concentration or to the concentrate, separating it from unwanted gangue minerals. The resulting solid amalgam is 40-60% by mass Hg 0 when isolated and is heated with an open flame to remove the majority of Hg 0 , revealing the sponge gold. However, the heating process is inefficient, and the sponge gold can still contain 2-5% Hg 0 by mass. Gold shops in ASGM communities are the major source of Hg 0 pollution and represent a threat to both human and environmental health. The Minamata Convention on Mercury, an international treaty, was enacted to encourage signatory nations to decrease their reliance upon Hg and its related compounds. Under the Convention, nations with significant ASGM activity must develop a National Action Plan specifying Hg pollution reduction targets for this sector, highlighting actions to be taken to eliminate the open burning of amalgams and sponge gold, particularly in residential areas. A series of training programs and environmental assessments in Peru have allowed for the formalization of a mapping technique that can be used to map ASGM communities over multiple days. This screening technique plots the maximum Hg 0 concentration determined during the monitoring period at each unique set of geographical coordinates. The maps generated during this process can be used to streamline the quantification of Hg 0 concentrations in and around these shops. The method for mapping Hg 0 emissions from gold shops in ASGM communities involves the use of a portable atomic absorbance spectrometer (AAS) with Zeeman correction to determine Hg 0 concentrations. These measured Hg 0 concentrations can then be correlated to position as determined by a hand-held GPS unit, and the resulting data mapped using a Geographic Information System (GIS). The method has been tested in ASGM communities in Peru and has been found to be effective in identifying point sources of Hg 0 contamination. The maps generated using this method can be used to identify areas where people may be exposed to elevated Hg 0 concentrations and/or occupational mercury vapor exposure, targeted enforcement, or outreach to limit Hg 0 pollution. The method has been made available to the public, along with a video walkthrough and authentic data set, to allow for the practice of data analysis and generation of the map using a free geographic information system.