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

Magnus Kramshøj,Christian N Albers,Bo Elberling,Riikka Rinnan,Rupert Holzinger,Thomas Holst

doi:10.1038/s41467-018-05824-y

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.

Highlights

Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere
In three separate laboratory experiments, we examine the release of biogenic volatile organic compounds (BVOCs) from thawing permafrost soils and follow the fate of these compounds in the active layer soil
The results show that the majority of BVOCs released from the permafrost were retained in the active layer soil

Summary

Introduction

Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere. We incubate frozen permafrost soils in a dynamic flow-through system and use a proton transfer reaction–time of flight–mass spectrometer (PTR-TOF-MS) instrument to detect 316 organic ions being released To assess whether these compounds are likely to end up in the atmosphere or be retained in the active layer soil overlaying the permafrost, we perform a second experiment, estimating the BVOC uptake capability of organic and mineral horizon soils. We go on to investigate whether microbial consumption of the two dominating BVOCs, ethanol and methanol, occurred in the studied active layer soils as well as the permafrost soil at low temperatures and realistic mixing ratios. We find that both ethanol and methanol were rapidly consumed by microbes. Our results show that thawing permafrost releases significant amounts of BVOCs and that these compounds are consumed by microbes in soil from the active layer

Methods

Results

Conclusion