Temperature Dependence of the Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide

He, Hong; Ma, Qingxia

doi:10.1021/jp711302r

Cited by 32 publications

(34 citation statements)

References 40 publications

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“…Destruction of OCS can also occur in the solid phase and was observed on pure mineral oxides with high basicity (Liu et al, 2008(Liu et al, , 2009(Liu et al, , 2010a. However, such catalytic reaction should be significant only in very dry soils (with only a few molecular layers of water) and in the absence of other competitive adsorbents such as CO 2 (Liu et al, 2008(Liu et al, , 2010b and is therefore neglected in our model.…”

Section: Consumption and Production Ratesmentioning

confidence: 96%

“…However these relationships obtained for organic vapours are unlikely to be applicable for OCS because the adsorption mechanisms may be completely different. Liu and colleagues have estimated OCS adsorption capacities of several mineral oxides and found that quartz (SiO 2 ) and anatase (TiO 2 ) did not adsorb OCS but other oxides with higher basicity adsorbed, reversibly or not, rather large quantities of OCS (Liu et al, 2008(Liu et al, , 2009(Liu et al, , 2010a. They also recognised that these estimates of the adsorption capacity of the minerals were an upper limit owing to the competitive adsorption of other gases such as CO 2 , H 2 O and Burnell et al (1988) This study Sun et al (2015) (d) NO x that occur in the real Earth's atmosphere (Liu et al, 2009(Liu et al, , 2010a and the somewhat lower OCS partial pressure in ambient air compared to that used in their experimental setup.…”

Section: Partitioning Of Ocs In the Different Soil Phasesmentioning

confidence: 99%

“…However, such catalytic reaction should be significant only in very dry soils (with only a few molecular layers of water) and in the absence of other competitive adsorbents such as CO 2 (Liu et al, 2008(Liu et al, , 2010b and is therefore neglected in our model. The total soil OCS uptake rate is thus computed as S = kB θ C:…”

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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Section: Consumption and Production Ratesmentioning

confidence: 96%

Section: Partitioning Of Ocs In the Different Soil Phasesmentioning

confidence: 99%

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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“…In our previous work, we have measured the linear range for the observed uptake coefficient of OCS on α-Al 2 O 3 to be 0-70 mg (Liu et al, 2008b), and to be 0-100 mg on MgO (Liu et al, 2008a). In this study, we kept the sample mass to be 70.0 mg for α-Al 2 O 3 and 90.0 mg for MgO to ensure OCS molecules accessing all of the layers of particle samples within the time scale of the KCMS measurement, and BET area of sample was used to calculate γ t .…”

Section: Kcms Experimentsmentioning

confidence: 99%

“…Nonetheless, information on the kinetics of the heterogeneous reaction of OCS on mineral oxides is limited. We recently reported uptake coefficients of OCS on MgO (Liu et al, 2008a), α-Al 2 O 3 and γ -Al 2 O 3 (Liu et al, 2008b). All of these studies were performed under dry conditions.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

Liu

2009

Atmos. Chem. Phys.

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Abstract.Here we compared the heterogeneous reactions of carbonyl sulfide (OCS) on the surface of α-Al 2 O 3 and MgO and the effect of water on the reactions at 300 K using Knudsen cell -mass spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, and temperature programmed reactions. H 2 S and CO 2 were found to be hydrolysis products of OCS on both α-Al 2 O 3 and MgO at ambient temperature. At low water vapor pressure (<6.8×10 −6 Torr), when water vapor pressure in the Knudsen cell reactor increased from 2.3×10 −6 to 6.8×10 −6 Torr, the initial true uptake coefficient of OCS on α-Al 2 O 3 decreased from 4.70±0.45×10 −7 to 3.59±0.34×10 −7 ; while it increased from 5.19±0.49×10 −7 to 6.48±0.62×10 −7 on MgO under the same conditions. At high relative humidity (0.07-0.67), the observed uptake coefficients of OCS on α-Al 2 O 3 and MgO, which were measured using an in situ DRIFTS, decreased from 4.63±0.22×10 −6 to 1.00±0.47×10 −6 and from 9.72±0.46×10 −5 to 7.68±0.36×10 −5 , respectively, when RH increased from 0.07 to 0.67 corresponding to 1.7-15.9 Torr of water vapor pressure. In the RH region of 0.17-0.67, the average observed uptake coefficient of OCS on α-Al 2 O 3 and MgO was equal to 8.34±2.19×10 −7 and 8.19±0.48×10 −5 , respectively. The restrictive effect of water on the heterogeneous reaction of OCS on the surface of α-Al 2 O 3 and MgO was found to be related to competitive adsorption between water and OCS molecules; while the promotive effect of water on the heterogeneous reaction of OCS on the surface of MgO at low coverage was ascribed to the formation of surface hydroxyl groups. When the environmental RH was greater than the RH of the monolayer, Correspondence to: H. He (honghe@rcees.ac.cn) which occurred readily at the atmospherically relevant humidity in the troposphere, thick water layer formed on the mineral dusts, especially, the basic thick water layer formed on the basic component of mineral dusts may be the primary contributor to the heterogeneous hydrolysis of OCS in the troposphere.

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Impacts of climate warming on atmospheric phase transition mechanisms

Varotsos

Ghosh

2016

Theor Appl Climatol

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Temperature Dependence of the Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide

Cited by 32 publications

References 40 publications

A new mechanistic framework to predict OCS fluxes from soils

A new mechanistic framework to predict OCS fluxes from soils

Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

Impacts of climate warming on atmospheric phase transition mechanisms

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Temperature Dependence of the Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide

Cited by 32 publications

References 40 publications

A new mechanistic framework to predict OCS fluxes from soils

A new mechanistic framework to predict OCS fluxes from soils

Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; and MgO

Impacts of climate warming on atmospheric phase transition mechanisms

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Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO