How do redox and temperature fluctuations influence mineral protection of organic matter during permafrost thaw?

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High latitude permafrost peatlands lock up vast amounts of Earth's soil carbon. There is much concern that this will be released as CO2 and CH4 following permafrost thaw, further exacerbating the climate crisis on a global scale (1). There is therefore urgent need to understand the factors which dictate whether carbon is stored or released in these regions as the Arctic rapidly warms (2). Previous work has demonstrated that carbon can be, in part, protected from degradation by reactive minerals such as poorly crystalline Fe(III) (oxyhydr)oxides (3-5). However, these minerals are very sensitive to microbial dissolution under anoxic conditions (6), suggesting the stability of this carbon sink will be highly dependent on redox conditions and microbial communities in the soils. Since permafrost peatlands are dynamic environments with redox conditions varying on a range of timescales, it is not yet clear whether with these reactive minerals provide a stable sink for old carbon over for long periods, or if observed Fe-C associations consist of "young" carbon which is periodically trapped at redox interfaces under dynamic conditions. This project will identify how temporal variation in redox conditions in permafrost peatlands impacts the stability of Fe(III) (oxyhydr)oxide minerals and how this, in turn, influences the mobility, bioavailability and turnover of organic matter during permafrost thaw.