Amazon forests capture high levels of atmospheric mercury pollution from artisanal gold mining

Giancarlo Inga,Heileen Hsu‐Kim ,Miles R Silman ,Gideon Erkenswick,Natalie Szponar,Caroline Moore,Luis E Fernandez,David C Evers,Raúl Pérez Purizaca,Jacqueline R Gerson,Cláudia M Vega ,Mrinalini Watsa,Emily A Ury,Melissa J Marchese ,Emily S Bernhardt,Bridget A Bergquist ,A Salvador Martínez ,Angelica Almeyda Zambrano,William Pan ,Kelsey N Lansdale ,Charles T Driscoll,Eben N Broadbent ,Victor Arostegui Sánchez

doi:10.1038/s41467-022-27997-3

Abstract

Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury. We examined mercury deposition and storage in an area of the Peruvian Amazon heavily impacted by artisanal gold mining. Intact forests in the Peruvian Amazon near gold mining receive extremely high inputs of mercury and experience elevated total mercury and methylmercury in the atmosphere, canopy foliage, and soils. Here we show for the first time that an intact forest canopy near artisanal gold mining intercepts large amounts of particulate and gaseous mercury, at a rate proportional with total leaf area. We document substantial mercury accumulation in soils, biomass, and resident songbirds in some of the Amazon’s most protected and biodiverse areas, raising important questions about how mercury pollution may constrain modern and future conservation efforts in these tropical ecosystems.

Highlights

Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury
There are three main pathways by which atmospheric Hg released from ASGM as gaseous elemental Hg (GEM) can return to the terrestrial landscape[20] (Fig. 1): GEM can sorb to particles in the atmosphere, which are intercepted by surfaces; GEM can be taken up directly by plants and incorporated into their tissues; GEM can be oxidized to Hg(II) species, which can be dry deposited, sorbed to atmospheric particles, or entrained in rainwater
Our investigation occurred in the southeastern Peruvian Amazon in the department of Madre de Dios, where over 100,000 hectares have been deforested for alluvial ASGM3 adjacent—and sometimes within—protected land and national reserves

Summary

Introduction

Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury. This study is the first to examine Hg depositional inputs near ASGM activity and how canopy cover correlates with these patterns, as well as the first to measure methylmercury (MeHg) concentrations in terrestrial landscapes of the Peruvian Amazon.

Results

Conclusion