Carbonyl sulfide produced by abiotic thermal and photodegradation of soil organic matter from wheat field substrate

Whelan, Mary; Rhew, R. C.

doi:10.1002/2014jg002661

Cited by 45 publications

(111 citation statements)

References 51 publications

(91 reference statements)

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“…These modifications included replacing the chamber bowl and soil collar with stainless steel components, and removing or replacing other small COS-producing parts. Dark chambers were selected to prevent photochemical production of COS (e.g., Whelan and Rhew, 2015) or CO (e.g., van Asperen et al, 2015) at the soil surface during chamber measurements. The two chambers were placed in similar environments, about 10 m apart.…”

Section: Methodsmentioning

confidence: 99%

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Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

et al. 2018

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Abstract. Soil is a major contributor to the biosphereatmosphere exchange of carbonyl sulfide (COS) and carbon monoxide (CO). COS is a tracer with which to quantify terrestrial photosynthesis based on the coupled leaf uptake of COS and CO 2 , but such use requires separating soil COS flux, which is unrelated to photosynthesis, from ecosystem COS uptake. For CO, soil is a significant natural sink that influences the tropospheric CO budget. In the boreal forest, magnitudes and variabilities of soil COS and CO fluxes remain poorly understood. We measured hourly soil fluxes of COS, CO, and CO 2 over the 2015 late growing season (July to November) in a Scots pine forest in Hyytiälä, Finland. The soil acted as a net sink of COS and CO, with average uptake rates around 3 pmol m −2 s −1 for COS and 1 nmol m −2 s −1 for CO. Soil respiration showed seasonal dynamics controlled by soil temperature, peaking at around 4 µmol m −2 s −1 in late August and September and dropping to 1-2 µmol m −2 s −1 in October. In contrast, seasonal variations of COS and CO fluxes were weak and mainly driven by soil moisture changes through diffusion limitation. COS and CO fluxes did not appear to respond to temperature variation, although they both correlated well with soil respiration in specific temperature bins. However, COS : CO 2 and CO : CO 2 flux ratios increased with temperature, suggesting possible shifts in active COS-and CO-consuming microbial groups. Our results show that soil COS and CO fluxes do not have strong variations over the late growing season in this boreal forest and can be represented with the fluxes during the photosynthetically most active period. Well-characterized and relatively invariant soil COS fluxes strengthen the case for using COS as a photosynthetic tracer in boreal forests.

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Section: Methodsmentioning

confidence: 99%

“…Soils vary from COS sinks to sources depending on their physical and biogeochemical conditions Whelan and Rhew, 2015;Whelan et al, 2016;Devai and DeLaune, 1995). Aerated upland soils are primarily weak COS sinks, whereas anoxic wetland soils are COS sources (Whelan et al, 2013).…”

mentioning

confidence: 99%

Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

et al. 2018

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“…Soils can also emit OCS into the atmosphere as reported in some agricultural fields (Maseyk et al, 2014;Whelan and Rhew, 2015) or in anoxic soils (Devai and Delaune, 1995;Mello and Hines, 1994;Whelan et al, 2013;Yi et al, 2008) but the exact mechanisms for such emissions are still unclear (Mello and Hines, 1994;Whelan and Rhew, 2015). At the global scale, OCS consumption by soils seems to dominate OCS emission, and its contribution to the atmospheric budget is large, at about one third of the OCS uptake by vegetation, but with a large uncertainty (Berry et al, 2013;Kettle et al, 2002;Launois et al, 2015).…”

Section: J Ogée Et Al: a New Mechanistic Framework To Predict Ocs Fmentioning

confidence: 99%

“…(11a) In some situations the OCS uptake rates can be overridden by OCS production. This is the case when soil temperature rises above 25 • C (Maseyk et al, 2014;Whelan and Rhew, 2015) or soil redox potential falls below −100 mV (Devai and Delaune, 1995). Light has also been proposed as an important trigger of OCS production, assuming photoproduction processes similar to those observed in ocean waters can occur (Whelan and Rhew, 2015).…”

Section: Consumption and Production Ratesmentioning

confidence: 99%

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A new mechanistic framework to predict OCS fluxes from soils

Ogée¹,

et al. 2016

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Abstract.Estimates of photosynthetic and respiratory fluxes at large scales are needed to improve our predictions of the current and future global CO 2 cycle. Carbonyl sulfide (OCS) is the most abundant sulfur gas in the atmosphere and has been proposed as a new tracer of photosynthetic gross primary productivity (GPP), as the uptake of OCS from the atmosphere is dominated by the activity of carbonic anhydrase (CA), an enzyme abundant in leaves that also catalyses CO 2 hydration during photosynthesis. However soils also exchange OCS with the atmosphere, which complicates the retrieval of GPP from atmospheric budgets. Indeed soils can take up large amounts of OCS from the atmosphere as soil microorganisms also contain CA, and OCS emissions from soils have been reported in agricultural fields or anoxic soils. To date no mechanistic framework exists to describe this exchange of OCS between soils and the atmosphere, but empirical results, once upscaled to the global scale, indicate that OCS consumption by soils dominates OCS emission and its contribution to the atmospheric budget is large, at about one third of the OCS uptake by vegetation, also with a large uncertainty. Here, we propose a new mechanistic model of the exchange of OCS between soils and the atmosphere that builds on our knowledge of soil CA activity from CO 2 oxygen isotopes. In this model the OCS soil budget is described by a first-order reaction-diffusion-production equation, assuming that the hydrolysis of OCS by CA is total and irreversible. Using this model we are able to explain the observed presence of an optimum temperature for soil OCS uptake and show how this optimum can shift to cooler temperatures in the presence of soil OCS emission. Our model can also explain the observed optimum with soil moisture content previously described in the literature as a result of diffusional constraints on OCS hydrolysis. These diffusional constraints are also responsible for the response of OCS uptake to soil weight and depth observed previously. In order to simulate the exact OCS uptake rates and patterns observed on several soils collected from a range of biomes, different CA activities had to be invoked in each soil type, coherent with expected physiological levels of CA in soil microbes and with CA activities derived from CO 2 isotope exchange measurements, given the differences in affinity of CA for both trace gases. Our model can be used to help upscale laboratory measurements to the plot or the region. Several suggestions are given for future experiments in order to test the model further and allow a better constraint on the large-scale OCS fluxes from both oxic and anoxic soils.

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Litter dominates surface fluxes of carbonyl sulfide in a Californian oak woodland

et al. 2016

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Carbonyl sulfide (COS) is a promising tracer for partitioning terrestrial photosynthesis and respiration from net carbon fluxes, based on its daytime co-uptake alongside CO 2 through leaf stomata. Because ecosystem COS fluxes are the sum of plant and soil fluxes, using COS as a photosynthesis tracer requires accurate knowledge of soil COS fluxes. At an oak woodland in Southern California, we monitored below-canopy surface (soil + litter) COS and CO 2 fluxes for 40 days using chambers and laser spectroscopy. We also measured litter fluxes separately and used a depth-resolved diffusion-reaction model to quantify the role of litter uptake in surface COS fluxes. Soil and litter were primarily COS sinks, and mean surface COS uptake was small (∼1 pmol m −2 s −1 ). After rainfall, uptake rates were higher (6-8 pmol m −2 s −1 ), and litter contributed a significant fraction (up to 90%) to surface fluxes. We observed rapid concurrent increases in COS uptake and CO 2 efflux following the onset of rain. The patterns were similar to the Birch effect widely documented for soils; however, both COS and CO 2 flux increases originated mainly in the litter. The synchronous COS-CO 2 litter Birch effect indicates that it results from a rapid increase in litter microbial activity after rainfall. We expect that the drying-rewetting cycles typical for mediterranean and other semiarid ecosystems create a pronounced seasonality in surface COS fluxes. Our results highlight that litter uptake is an important component of surface COS exchange that needs to be taken into account in ecosystem COS budgets and model simulations.

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Carbonyl sulfide produced by abiotic thermal and photodegradation of soil organic matter from wheat field substrate

Cited by 45 publications

References 51 publications

Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

A new mechanistic framework to predict OCS fluxes from soils

Litter dominates surface fluxes of carbonyl sulfide in a Californian oak woodland

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