Preprints
https://doi.org/10.5194/egusphere-2025-3847
https://doi.org/10.5194/egusphere-2025-3847
19 Aug 2025
 | 19 Aug 2025
Status: this preprint is open for discussion and under review for Biogeosciences (BG).

Reviews and syntheses: Artisanal small-scale gold mining (ASGM)-derived mercury contamination in agricultural systems: what we know and need to know 

David S. McLagan, Excellent O. Eboigbe, and Rachel J. Strickman

Abstract. The escalating global demand for gold has fuelled the rapid expansion of artisanal and small-scale gold mining (ASGM), which has become the largest source of mercury (Hg) emissions worldwide. Here we synthesize current research on the pervasive contamination of agricultural systems by ASGM-derived Hg, identifying the key environmental pathways and subsequent risks to food security. Within these systems, Hg undergoes complex biogeochemical transformations, with the methylation of inorganic Hg into its highly neurotoxic form, methylmercury (MeHg), being a critical process. This is particularly pronounced in rice paddy systems, where microbial activity and favourable redox conditions facilitate Hg methylation, resulting in the bioaccumulation of MeHg in rice grains—a staple food for billions. However, this synthesis reveals that atmospheric uptake is important to total Hg loadings in rice, and more so in tissues of crops grown in unsaturated soils. Indeed, we stress the importance of assessing all potential uptake pathways of Hg in agricultural systems: foliar assimilation from air, uptake from soils/water (particularly MeHg in rice), direct deposition to surfaces, and consumption of contaminated crop tissues (by both humans and livestock/poultry), to delineate the source and ratios of the different pools of Hg within crops and their consumers. A common shortcoming in past studies of ASGM-derived Hg in agricultural systems is that they have commonly overlooked one or more of these uptake pathways. These findings underscore a significant threat to global food chains and human health through the consumption of Hg contaminated produce. Mitigating these risks requires an improved understanding of the quantity of emissions/releases from ASGM, input pathways, and Hg biogeochemical cycling and fate in agricultural landscapes, paving the way for targeted interventions and sustainable management strategies to protect vulnerable communities. We suggest that these goals can be achieved through strategic international and interdisciplinary collaborations, novel and accessible technologies, and care for the dissemination of scientific information to impacted communities.

Competing interests: D.S.M. is a member of the editorial board of the journal Biogeosciences. The authors declare that they have no other conflict of interest.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share
David S. McLagan, Excellent O. Eboigbe, and Rachel J. Strickman

Status: open (until 04 Oct 2025)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
David S. McLagan, Excellent O. Eboigbe, and Rachel J. Strickman
David S. McLagan, Excellent O. Eboigbe, and Rachel J. Strickman

Viewed

Total article views: 887 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
870 14 3 887 10 17
  • HTML: 870
  • PDF: 14
  • XML: 3
  • Total: 887
  • BibTeX: 10
  • EndNote: 17
Views and downloads (calculated since 19 Aug 2025)
Cumulative views and downloads (calculated since 19 Aug 2025)

Viewed (geographical distribution)

Total article views: 862 (including HTML, PDF, and XML) Thereof 862 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 09 Sep 2025
Download
Short summary
ASGM is rapidly expanding and Hg-use in the sector impacts agricultural system surrounding these spatially distributed activities. Contamination of crops from ASGM-derived Hg occurs via both uptake from both air and soil/water. In addition to risks to human consumers, Hg in staple crops can also be passed along to livestock/poultry further conflating risks. Research in this area requires interdisciplinary, collaborative, and adaptable approaches to improve our comprehension of these impacts.
Share