Presence of Phenolic Compounds in Porewater at Stordalen Mire

Stordalen Mire is located in the discontinuous permafrost zone in northern Sweden. Thawing permafrost has created an environmental gradient from palsa (permafrost) to bog (partially thawed) to fen (permafrost-free). Along this thaw gradient, the uptake of carbon dioxide from the atmosphere increases concurrently with methane emissions to the atmosphere. Organic matter reactivity and decomposability differs along this gradient as well. In waterlogged peat soils, naturally occurring phenolic compounds inhibit decomposition, which slows methane emissions and preserves organic matter. Porewater samples were collected from multiple depths within replicate palsa, bog, and fen environments at Stordalen Mire in July 2022. The concentration of phenols in porewater samples was determined using the Folin-Ciocalteu method. The samples were run through a spectrophotometer (630nm) to determine the absorbance of each sample, and the concentration of phenolic compounds was calculated relative to Gallic acid standard solutions. Comparing only the bog and fen environments, the concentration of gallic acid was the highest in the bog. The palsa environments also had higher concentrations of gallic acid relative to the fen. These findings support the idea that carbon sequestration in the bog and palsa is in part driven by the elevated concentrations of phenolic compounds and may partly explain why fen organic matter is more humified.