UK peatlands have spent millennia soaking up mercury pollution from the air, and climate change could now unlock that toxic stockpile. This matters because peatlands store not only vast amounts of carbon but also mercury deposited from Bronze Age smelting, coal burning, and modern industry. Microbes in the soil can convert this mercury into methylmercury—a potent neurotoxin that builds up in fish and threatens food webs from rivers to coastal seas. No one knows whether warming temperatures, shifting water levels, or changes in soil chemistry will turn peatlands into a net source of this toxin. The team will combine field sampling, lab experiments, and computational models across three UK peatlands to map how much mercury is stored, in what chemical forms, and how it transforms under different environmental conditions. If the research succeeds, it will give policymakers and land managers the first reliable tools to predict whether draining or rewetting a peatland will release methylmercury into downstream fisheries. The work is fundamentally curiosity-driven—unravelling the molecular and microbial mechanics of mercury cycling—but its practical payoff could be protecting coastal seafood from a centuries-old pollution legacy.
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Context: Peatlands play a critical role in mitigating global warming by storing disproportionately large amounts of carbon for their area. Unfortunately, in the UK and parts of Europe, peatlands have also been accumulating atmospherically deposited mercury pollution for millennia. This mercury originated from both natural (e.g., volcanoes) and anthropogenic sources including mining and smelting, fossil fuel combustion, and chemicals manufacturing, from the Bronze Age to the present day. Although adoption of the Minamata Convention in 2017 (148 countries) mandates phasing out of industrial and artisanal mercury sources through 2032, “legacy” mercury stored in peatlands can potentially be remobilised into the atmosphere or downstream ecosystems. Much of this legacy mercury is bound to organic matter and therefore intimately linked to the fate of peatland carbon stores. If global warming and/or land management practices impact peatland carbon cycling, then this will almost certainly impact mercury cycling as well. Challenge: An emerging “frontier” in peatlands research is to unravel the complex environmental and microbial factors determining the mobility and toxicity of accumulated mercury. Organic matter and inorganic molecules like sulphate from rain or iron-oxide minerals in soil can influence the form and fate of mercury. Soil and water microbes can volatilise dissolved mercury into mercury vapour (returning it to the atmosphere) or convert it to methylmercury, a neurotoxin that threatens terrestrial and marine food webs. Microbes evolved the ability to volatilise mercury as a defence against its toxicity, while the true function of mercury methylation is unknown. To advance this scientific frontier requires application of complementary cutting-edge techniques for determining the forms and chemical interactions of peatland mercury. To predict how much and how quickly methylmercury is formed, for example, requires a molecular-scale understanding of mercury-organic matter interactions that control the availability of mercury for methylation and genome-level resolution of the metabolic capabilities of microbial methylators, in the context of peatland hydrology and biogeochemistry. With this knowledge, we can envision and construct a new and more accurate conceptual model for peatland mercury cycling as a first step towards building predictive tools. Aims and objectives: With this proposal, we aim to address the overarching question: Will peatlands act as a source or sink for methylmercury under climate change?”. We will do this by combining advanced field, laboratory and computational approaches to determine how much mercury is potentially stored in UK peatlands, and in what form; and how this stored mercury will respond to environmental factors such as changes in temperature; water level; acidity; and dissolved organic carbon and other nutrients. This project will fill fundamental knowledge gaps, using three representative peatlands across the UK where both new and stored mercury can be feasibly evaluated with respect to abundance, forms and chemical transformations. Our research team draws together groundbreaking interdisciplinary expertise, tools and techniques from across the atmospheric, earth, environmental and life sciences to work on this challenging problem. Potential applications and benefits: This project will build the foundation for constructing new process-based models for scientists, policy makers, land managers and other stakeholders needed to predict the short- and long-term fates of mercury in peatlands. The insights generated by this project will help adapt and improve practices for optimising carbon storage and mitigating the export of methylmercury from peatlands to sensitive coastal food webs, in alignment with NERC’s “catchment to coasts” paradigm for ecosystem science.
Casey Bryce (Co-Investigator)Chiara Di Marco (Co-Investigator)John Moreau (Principal Investigator)Nicholle Bell (Co-Investigator)Roxane Andersen (Co-Investigator)
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