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New research from Faculty of Arts and Science researcher David McLagan and his research group, the Fire, Earth, Water, Air Contaminant Biogeochemistry () Lab, was recently published in the (EGU) journal .

He and the FEWALab team have confirmed that mercury pollution from artisanal and small-scale gold mining (ASGM) is contaminating food crops not through the soil, as previously believed, but directly from the air.

“Mercury is a global problem. Used to extract gold from raw ore, mercury is a powerful neurotoxin. Long-term exposure, even at low levels, can damage the nervous system, impair cognitive development in children, and cause serious cardiovascular and reproductive problems,” Dr. McLagan explains. “Releases/emissions of mercury from ASGM activities can undergo long-range transport around the world and contribute to health-related mercury issues particularly in aquatic systems. Canada's abundance of lake and wetlands systems, in which methylmercury [the most bioaccumulative and toxic form of mercury], make Canada a country particularly vulnerable to increasing global emissions of mercury.”

Faculty of Arts and Science MSc. graduate Excellent Eboigbe was the first author on the research paper. Dr. Abiodun Odukoya (University of Lagos) and Mr. Nnamdi Anene (University of British Columbia) were also instrumental in undertaking the field work associated with this research and have on-going plans to connect this data and knowledge with the impacted community of Uke, Nasarawa State in Nigeria.

“In this research we examined the impacts of mercury use and emissions in Artisanal and Small-scale Gold Mining [ASGM] on local agricultural systems, which ASGM is now directly competing against for land resources,” Dr. McLagan (School of Environmental Studies, Department of Geological Sciences and Geological Engineering) explains. “We compared both mercury concentrations and mercury stable isotope ratios in crops from a field located 500 meters from the ASGM site with those grown eight kilometres away. We also measured mercury concentrations and stable isotope ratios in soil and air at the ASGM site and the two farms.

“The stable isotope data is important here as they tell us critical information about sources and transformation processes that allow us to examine where the mercury found in crops comes from - soil (uptake into roots) or air (uptake into foliage).”

What Dr. McLagan and the FEWALab team discovered was striking. “Mercury concentrations in leaves and grains were approximately 10-50 times higher in the farm closer to the mining site. The stable isotope data also confirmed the atmosphere was the source of the majority of mercury found within plant tissues. While the concentrations measured in edible parts of these plants were below health consumption thresholds, this is a relatively small, but legal ASGM operation. There are many sites that are substantially larger, operate illegally and are an increased risk to the public.”

The atmospheric mercury measurements were collected using the Mercury Passive Air Sampler (MerPAS) technology. Dr. McLagan was awarded the Governor General's Innovation Award for his role in the development of this new technology. The system operates without the need for electricity or gas, using natural movements of air and a carbon material to capture mercury from air.

“These atmospheric measurements were critical in establishing the level of mercury being emitted to air from the ASGM site and to quantify the stable isotope signature of those emissions. Our knowledge of atmospheric mercury and mercury uptake and cycling within plants, and experience working previously in ASGM areas (in Peru) provided the basis for why we wanted the FEWA Lab to pursue this important research.”

Dr. McLagan explains why these research findings are so important.

“ASGM is a huge issue. It is widely reported as now the largest source of mercury emissions globally, and the sector is growing exponentially as the price of gold skyrockets. In 2005, gold was valued at $400 US/oz, while in 2025 it just surpassed $4,000 US/oz. It is the demand for gold in the Global North that drives people to ASGM in the Global South. And mercury-use in ASGM is not the only issue. ASGM activities cause vast deforestation, river siltation, and as these activities are largely illegal, it results in them being run by criminal syndicates and causing social upheaval in affected communities. Nonetheless, ASGM provides critical income to many who would otherwise be impoverished. This is a very socially and environmentally complex issue.”

Looking to the future, he says the work provides a basis for better understanding the impacts of mercury on farming communities affected by ASGM and provides critical data to communities to make more informed decisions regarding ASGM and mercury use.

“In addition, this clarifies to the scientific community the importance of mercury uptake from air in farming systems and will provide an improved basis for estimated emissions and releases of mercury from ASGM, which is currently poorly constrained despite this sector now being the largest source of mercury.”

In follow up work, Dr. McLagan, MSc. Graduate Ms. Eboigbe, and another collaborator, Dr. Rachel Strickman have had a accepted in Biogeosciences. This article provides an excellent basis for diving deeper into this issue as well as presenting some solutions and pathways forward.