Biogenic volatile release from permafrost thaw is determined by the soil microbial sink

Abstract

Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere. We do not know whether permafrost thaw also releases non-methane volatile organic compounds that can contribute to both negative and positive radiative forcing on climate. Here we show using proton transfer reaction–time of flight–mass spectrometry that substantial amounts of ethanol and methanol and in total 316 organic ions were released from Greenlandic permafrost soils upon thaw in laboratory incubations. We demonstrate that the majority of this release is taken up in the active layer above. In an experiment using 14C-labeled ethanol and methanol, we demonstrate that these compounds are consumed by microorganisms. Our findings highlight that the thawing permafrost soils are not only a considerable source of volatile organic compounds but also that the active layer regulates their release into the atmosphere.

Process Understanding of Soil BVOC Fluxes in Natural Ecosystems: A Review

“…In plant leaves, ethanol is easily oxidized to acetaldehyde and further, to acetic acid (Kreuzwieser & Rennenberg, ) and its high water solubility makes it easily accessible to microorganisms. The uptake of ethanol by organic and mineral soils has been shown by Kramshøj et al ().…”

“…Bourtsoukidis et al () found that acetone emissions from SOC in aerobic conditions were an order of magnitude higher than those from the canopy. In contrast, Kramshøj et al () found that permafrost‐released acetone can be taken up by overlying mineral and organic soils.…”

“…Mancuso et al () explained that formation of formaldehyde was most probably linked to methylotrophic bacteria and occurred as a result of demethylation reactions. However, soil uptake of formaldehyde has also been shown both by soil samples under laboratory conditions (Kramshøj et al, ) and in a field setting (Gray et al, ). Formaldehyde, together with isoprene, was the two dominant compounds taken up by sandy soil in a subalpine ecosystem (Gray et al, ).…”

“…This alcohol has also been detected in litter emissions of beech (Warneke et al, ), pine, and spruce (Isidorov et al, ). Kramshøj et al () reported that ethanol was the compound emitted from permafrost soils upon thawing at the highest rates. They speculated that the source of ethanol was likely fermentative decomposition of plant materials in anoxic soils.…”

“…Similar peaks in emissions have been found by Rossabi et al () after rewetting of dry soils. At relatively high WFPS, emissions have been observed to decrease when anaerobic conditions shift to aerobic (and hence fermentation decreases) in permafrost soils (Kramshøj et al, ) and peat (Faubert et al, ; Tiiva et al, ). In general, WFPS is often used for modelling soil N 2 O fluxes (Tian et al, ) and we would suggest including WFPS to account for the impacts of soil water content on BVOC production.…”