Volatile Organic Compound Emissions From Soil Following Wetting Events

Abstract

Dynamics of carbon dioxide (CO2) emissions following the wetting of dry soil have been widely studied in field and laboratory settings. Nonmethane volatile organic compounds (VOCs) are also emitted from soil following a rain event and are evident from the characteristic smell of wet soil. Few studies have documented VOC emissions before and after soil rewetting. Soil emissions were studied using a dynamic flux chamber system purged with VOC‐free air, with identification and quantification of emissions performed by gas chromatography/mass spectrometry. All soils exhibited a rewetting‐induced pulse of VOC emissions, with VOC emissions 14 times higher (on average) in the few hours after rewetting compared to moist soils 2 days after rewetting. This VOC rewetting pulse mirrored the CO2 rewetting pulse (the so‐called “Birch Effect”) but was shorter in duration. Average VOC emissions were 5.0 ± 2.0% of CO2 emissions (molar C equivalent) and increased with increasing soil organic matter content (ρ = 0.40, ρ = 0.99 with one soil excluded). The amounts and types of VOCs varied with time since rewetting and across the five studied soil types, though acetone and small hydrocarbons were the dominant compounds emitted from all soils. Some of the VOCs emitted are likely important mediators of microbial activities and relevant to atmospheric chemical dynamics. Soil VOC emissions, similar to CO2 emissions, are strongly affected by rewetting events, and it is important to consider these rewetting dynamics when modeling soil and ecosystem VOC emissions and understand their relevance to terrestrial ecosystem functioning and atmospheric processes.

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

“…This relationship depicts an initial peak of sesquiterpenes at high WFPS, potentially linked to anaerobic production, and a second peak at moderate WFPS associated with aerobic production. 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, ).…”

Systematic bias in evaluating chemical transport models with maximum daily 8 h average (MDA8) surface ozone for air quality applications: a case study with GEOS-Chem v9.02

“…The nighttime depletion cannot be due to chemical titration by anthropogenic NO emissions since the selected CASTNET sites are rural and not located near major roadways or industrial sources. It must instead be due to deposition, including possible titration by short-lived biogenic VOCs (Goldstein et al, 2004;Ruuskanen et al, 2011;Rossabi et al, 2018) under stratified surface layer conditions. The model diurnal cycle at 65 m of altitude (lowest model level) has the correct phase but the amplitude is much too weak.…”

Long-term total OH reactivity measurements in a boreal forest

“…Forest floor emissions of monoterpenes are known to be high in spring after snow has melted (Hellén et al, 2006;Aaltonen et al, 2011;Mäki et al, 2017) and VOC emission bursts have been observed after wetting events (e.g. Rossabi et al, 2018). There has also been some indication that thawing 5 snow/soil could be a source of volatile organic amines (Hemmilä et al, 2018).…”