Peat fires and the unknown risk of legacy metal and metalloid pollution

Introduction. Peatlands have persisted for millennia, acting as globally-important sinks of atmospheric carbon dioxide (Yu 2012) and regionally-important role sinks of pollutants, such as lead, arsenic, or mercury (toxic metals and metalloids, TMMs) (Bindler 2006). The role peatlands play in atmospheric carbon sequestration often overshadows their role in storing pollutants despite, for example, peat mercury accumulation rates increasing 60–130× relative to pre-industrial rates (Bindler 2006). Peatlands sustain their carbon and TMM sink persistence through a suite of ecohydrological feedbacks and plant traits (Souter and Watmough 2016, McCarter et al 2020). However, the interaction of climate change, land-use change and wildfire are testing peatland resilience (Wilkinson et al 2023), potentially placing their longterm stores of recent and legacy carbon and TMMs on the edge of catastrophic release.