Rapid mineralization of biogenic volatile organic compounds in temperate and Arctic soils

Abstract

<p><strong>Abstract.</strong> Biogenic volatile organic compounds (BVOCs) are produced by all life forms. Their release into the atmosphere is important with regards to a number of physical and chemical processes and great effort has been put into determining sources and sinks of these compounds in recent years. Soil microbes as a possible sink for BVOCs in the atmosphere has been suggested, however, experimental evidence for this sink is scarce despite its potentially high importance to both carbon cycling and atmospheric concentrations of these gases. We therefore conducted a study with a number of commonly occurring BVOCs labelled with <sup>14</sup>C and modified existing methods to study mineralization of these compounds to <sup>14</sup>CO<sub>2</sub> in four different top soils. Five of the six BVOCs were rapidly mineralized by microbes in all soils. However, great differences were observed with regards to speed of mineralization, extent of mineralization and variation between soil types. Methanol, benzaldehyde, acetophenone and the oxygenated monoterpene geraniol were mineralized within hours in all soils. The hydrocarbon monoterpene p-cymene was mineralized rapidly in soil from a coniferous forest but slower in soil from and adjacent beech stand while chloroform was mineralized slowly in all soils. From our study it is clear that soil microbes are able to degrade completely BVOCs released by aboveground vegetation as well as BVOCs released by soil microbes and plant roots. In addition to the possible atmospheric implications of this degradation the very fast mineralization rates are likely important in shaping the net BVOC emissions from soil and it is possible that BVOC formation and degradation may be an important but little recognized part of internal carbon cycling in soil.</p>

Volatile emissions from thawing permafrost soils are influenced by meltwater drainage conditions

“…Hence, it is possible that differences in microbial community composition will cause emission profiles to vary, and that fungal emissions were more important in the B horizon compared to permafrost in our study. Arctic mineral and permafrost soils have previously been shown to house different microbial communities, and while bacteria to fungal ratio is higher in permafrost soils compared to Arctic mineral soils (Kramshøj et al., ), the bacteria to fungal ratio in Arctic active layer tundra soil is comparable to that of a temperate beech soil (Albers et al., ). Even though microbial community composition in permafrost soils changes rapidly following thaw (Gittel, Bárta, Kohoutová, Mikutta, et al., , Gittel, Bárta, Kohoutová, Schnecker, et al., ; Mackelprang et al., ; Wilhelm, Niederberger, Greer, & Whyte, ), it remains distinct from that in the active layer (Mackelprang et al., ).…”

“…In oxic soils, the largest source for BVOCs is secondary metabolite production, while BVOC production under anaerobic conditions is coupled to the energy chain of fermentative processes. At the same time, soil microorganisms utilize BVOCs as a carbon source (Albers, Kramshøj, & Rinnan, ; Owen, Clark, Pompe, & Semple, ); a process likely decelerated in anoxic soils with lower redox potential (Bridgham et al., ). The net emission from soils that become waterlogged will therefore likely increase in magnitude (Faubert et al., , ).…”

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

“…Spielmann et al () exposed mountain grassland mesocosms and bare soils to increasing concentrations of isoprene and α‐pinene (0–10 ppbv) in a laboratory setting and found soils to be the dominant sink for both compounds. Albers et al (), through isotopic labelling, found that five out of six investigated BVOCs were rapidly mineralized by microbes in four different soils and illustrated that microbes could completely degrade BVOCs to CO 2 . Gray et al () found that a large fraction (~68%) of isoprene was consumed by soils after 45 days of incubation and Cleveland & Yavitt.…”

“…Albers et al () discussed a potential overestimation of BVOC uptake rates in experiments when soils are exposed to BVOC concentrations that are a few orders of magnitude higher than ambient concentrations, which is likely to stimulate BVOC degradation. Using isotopic labelling and exposing soils to natural mixing ratios is needed for quantification of microbial uptake rates of BVOCs.…”

“…Methylotrophic bacteria are common inhabitants in soils (Fall & Benson, 1996) and they can consume methanol, causing a net uptake in soil in different ecosystems (Asensio, Peñuelas, Filella, et al, 2007;Kramshøj et al, 2018). Albers et al (2018) showed very high and rapid methanol mineralization rates by microbes in four soil types.…”