Rise of mercury emissions in the Amazon rainforest: an evaluation of artisanal and small-scale gold mining and biomass burning sources

Two important global sources of mercury emissions to the atmosphere are biomass burning (BMB) and artisanal and small-scale gold mining (ASGM) operations. These activities, prevalent in the Amazon rainforest, are driven by agricultural and cattle ranching expansion and rising international gold prices, respectively. Although there are indications of increasing ASGM activities in the Amazon, there are no studies of corresponding mercury consumption and emissions within this context. In this study, a regional assessment of mercury consumption and emissions from ASGM activities is made for the period between 2001 and 2014. Mercury consumption and emissions are derived from analyses of official and illegal gold production estimates and mercury imports. Between 2001 and 2014, annual ASGM mercury emissions from the region increased approximately 155% from 57.4 metric tons to 146.1 metric tons. If illegal gold mining occurring in the Amazon rainforest is considered, mercury emissions increase to 242 tons in 2014. Between 2001 and 2014, ASGM mercury emissions (excluding emissions from illegal gold mining) for the whole region were 1,339 metric tons. Similarly, over 3,420 metric tons of mercury were consumed and released to the environment as tailings and emissions with almost 65% coming from just 3 countries (Colombia, Peru, and Suriname) out of 8 countries and 1 overseas territory evaluated. In contrast, BMB mercury emissions derived from deforestation rates in the Amazon decreased 80% from 12.7 tons to 2.6 tons in the same period. Decrease of BMB emissions was driven by lower deforestation rates in Brazil. Between 2001 and 2014, approximately 105 tons of mercury were released to the atmosphere from deforestation activities. These results show the significant increase of ASGM mercury emissions in the Amazon rainforest, which would represent 12% of global mercury emissions from anthropogenic sources