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Carbonyl sulfide and dimethyl sulfide fluxes in an urban lawn and adjacent bare soil in Guangzhou, China
Abstract
Carbonyl sulfide (COS) and dimethyl sulfide (DMS) fluxes from an urban Cynodon dactylon lawn and adjacent bare soil were measured during April-July 2005 in Guangzhou, China. Both the lawn and bare soil acted as sinks for COS and sources for DMS. The mean fluxes of COS and DMS in the lawn (-19.27 and 18.16 pmol/(m2 sec), respectively) were significantly higher than those in the bare soil (-9.89 and 9.35 pmol/(m2 sec), respectively). Fluxes of COS and DMS in mowed lawn were also higher than those in bare soils. Both COS and DMS fluxes showed diurnal variation with detectable but much lower values in the nighttime than in the daytime. COS fluxes were related significantly to temperature and the optimal temperature for COS uptake was 29 degrees C. While positive linear correlations were found between DMS fluxes and temperature. COS fluxes increased linearly with ambient COS mixing ratios, and had a compensation point of 336 ppt.
... In the field, reported oxic soil OCS fluxes range from near zero up to −10 pmol m −2 s −1 , with average uptake rates typically between 0 and −5 pmol m −2 s −1 . Higher uptake fluxes of −10 to −20 pmol m −2 s −1 have been observed in a grassland soil (Whelan and Rhew, 2016), wheat field soils (Kanda et al., 1995;Maseyk et al., 2014), unplanted rice paddies (Yi et al., 2008), and bare lawn soil (Yi and Wang, 2011). However, under warm and dry conditions, fluxes approached zero in grasslands (Berkelhammer et al., 2014;Whelan and Rhew, 2016) and an oak woodland . ...
... i From Simmons et al. (1999). j Range from Whelan and Rhew (2016), encompassing observations of a grass field by Yi and Wang (2011). k Range reported in de Mello and Hines (1994), encompassing values observed by a bog microcosm by Fried et al. (1993). ...
For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important one. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies. More work needs to be done to generate global coverage for OCS observations and to link this powerful atmospheric tracer to systems where fundamental questions concerning the carbon and water cycle remain.
... While this study did not separate soil and plant components of the flux, light and dark flux estimates yielded similar sinks, suggesting either a large role for soils in the ecosystem flux or the presence of open stomata under dark conditions. In a similar study, Yi and Wang (2011) undertook chamber measurements over a grass lawn in subtropical China. Ecosystem fluxes of -10 19.2 pmol m -2 s -1 were observed. ...
... In the field, reported oxic soil OCS fluxes range from near zero up to -10 pmol m -2 s -1 , with average uptake rates typically between 0 and 5 pmol m -2 s -1 (see Fig. 5). Higher fluxes of -10--20 pmol m -2 s -1 20 have been observed in a grassland soil (Whelan and Rhew, 2016), wheat field soils (Kanda et al., 1995;Maseyk et al., 2014), unplanted rice paddies (Yi et al., 2008) and bare lawn soil (Yi and Wang, 2011). ...
For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies. More work needs to be done to generate global coverage for OCS observations and to link this powerful atmospheric tracer to systems where fundamental questions concerning the carbon and water cycle remain.
... The published data pointed out that the higher content of organic matter and microorganisms generate stronger biogenic sulfur emissions (Schäfer et al. 2010). Compared with the results from Yi et al. (2008Yi et al. ( , 2011, our value of results were slightly less which was caused by the low humus content. ...
... This was due to the fact that temperature at noon exceeded the optimal temperature for enzyme CA activity (Yi et al. 2008). According to previous studies, the optimal temperatures for enzyme CA activity were 15~20°C in wheat and forest soils in Shandong province (Liu et al. 2010) and 25°C in lawn soil in Beijing (Liu et al. 2007), and 29°C in urban lawn soil in Guangzhou (Yi and Wang 2011). The local temperatures at 14:00 ranged from 27~34°C, which were almost higher than the optimal temperature, and may be the likely cause for the reorganization and denaturation of enzyme structure and activity reduction. ...
Investigations about VOSCs (volatile organic sulfur compounds) have been received increasing attention for their significant contribution to the nonvolcanic background sulfate layer in the stratosphere and the earth’s radiation balance and as a potential tool to understand the carbon budget. In this study, COS and CS2 were always recorded throughout the entire rice cultivation season of 2014. COS fluxes appeared as emission in non-planted soil and as uptake in planted soil, the corresponding results were obtained as 2.66 and −2.35 pmol·m⁻²·s⁻¹, respectively. For CS2, both planted and non-planted paddy fields acted as sources with an emission rate of 1.02 pmol·m⁻²·s⁻¹ and 2.40 pmol·m⁻²·s⁻¹, respectively. COS emission or uptake rates showed a distinct seasonal variation, with the highest fluxes at the jointing-booting stage. COS and CS2 fluxes increased with increasing N fertilizer use because of improved plant and microbial growth and activity. Plots treated with both N and S reduced COS and CS2 fluxes slightly compared with plots with only-N treatment. Light, soil moisture or temperature showed no significant correlation with COS and CS2 fluxes, but revealed the important impacts on the magnitude and direction of gases fluxes. The results also showed that the (available) sulfur contents in soil and roots had a certain effect on VOSCs emission or uptake. Our results highlight the significance of biotic and abiotic production and consumption processes existing in the soil.
... This study revealed that OCS fluxes varied across the five biogeographical zones of the Antarctic tundra. Notably, soils from animal-free regions were observed to act as OCS sinks, a pattern consistent with soils from most other global ecosystems 34,[42][43][44] . On the other hand, soils from animal colonies were OCS sources, similar to anoxic soils of wetlands and some oxic soils 6,34,45 . ...
The Antarctic tundra, dominated by non-vascular photoautotrophs (NVP) like mosses and lichens, serves as an important habitat for sea animals. These animals contribute organic matter and oceanic sulfur to land, potentially influencing sulfur transformations. Here, we measured carbonyl sulfide (OCS) fluxes from the Antarctic tundra and linked them to soil biochemical properties. Results revealed that the NVP-dominated upland tundra acted as an OCS sink (−0.97 ± 0.57 pmol m⁻² s⁻¹), driven by NVP and OCS-metabolizing enzymes from soil microbes (e.g., Acidobacteria, Verrucomicrobia, and Chloroflexi). In contrast, tundra within sea animal colonies exhibited OCS emissions up to 1.35 ± 0.38 pmol m⁻² s⁻¹, resulting from the introduction of organosulfur compounds that stimulated concurrent OCS production. Furthermore, sea animal colonization likely influenced OCS-metabolizing microbial communities and further promoted OCS production. Overall, this study highlighted the role of sea animal activities in shaping the soil-atmospheric exchange of OCS through interacting with soil chemical properties and microbial compositions.
... 2,3 Concentrations of COS in various environments are summarized in Table S1. COS is naturally produced from sediments 4 and plants, 5,6 especially in coastal areas 7−12 and lakes. 13,14 Volcanos are geological sources of COS. ...
A portable chemical analysis system for monitoring ambient carbonyl sulfide (COS) was investigated for the first time. COS is paid attention to from the perspectives of photosynthesis tracer, breath diagnosis marker, and new process-use in the manufacture of semiconductors. Recently, the threshold level value of COS was settled at 5 ppm in volume ratio (ppmv) for workplace safety management. In this work, COS was converted to H2S by a small column packed with alumina catalyzer at 65 °C. Then, the H2S produced was collected in a small channel scrubber to react with fluorescein mercuric acetate (FMA), and the resulting fluorescence quenching was monitored using an LED/photodiode-based miniature detector. The miniature channel scrubber was re-examined to determine its robustness and easy fabrication, and conditions of the catalyzer were optimized. When the FMA concentration used was 1 μM, the limit of detection and dynamic range, which were both proportional to the FMA concentration, were 0.07 and 25 ppbv, respectively. Ambient COS in the background level and even contaminated COS in the nitrogen gas cylinder could be detected. If necessary, H2S was removed selectively by reproducible adsorbent columns. COS concentrations of engine exhaust were measured by the proposed method and by cryo-trap-gas chromatography-flame photometric detection, and the results obtained (0.5–5.9 ppbv) by the two methods agreed well (R² = 0.945, n = 19). COS in ambient air and exhaust gases was successfully measured without any batchwise pretreatment.
... physio- sorption; Conrad and Meuser, 2000). There are further stud- ies conducted in sub-tropical humid monsoon climates that have also reported COS compensation points above 100 ppt ( Geng and Mu, 2004;Yi and Wang, 2011), but still below at- mospheric concentrations (i.e. around 300 ppt). ...
Soils both emit and consume the trace gas carbonyl
sulfide (COS) leading to a soil–air COS exchange rate that is the net
result of two opposing fluxes. Partitioning these two gross fluxes and
understanding their drivers are necessary to estimate the contribution of
soils to the current and future atmospheric COS budget.Previous efforts to disentangle the gross COS fluxes from soils have used
flux measurements on air-dried soils as a proxy for the COS emission rates
of moist soils. However, this method implicitly assumes that COS uptake
becomes negligible and that COS emission remains steady while soils are drying.
We tested this assumption by simultaneously estimating the soil COS sources
and sinks and their temperature sensitivity (Q10); these estimates were based on soil–air COS flux
measurements on fresh soils at different COS concentrations and two soil
temperatures. Measurements were performed on 27 European soils from
different biomes and land use types in order to obtain a large range of
physical–chemical properties and identify the drivers of COS consumption and
production rates.We found that COS production rates from moist and air-dried soils were not
significantly different for a given soil and that the COS production rates
had Q10 values (3.96 ± 3.94) that were larger and more variable
than the Q10 for COS consumption (1.17 ± 0.27). COS production
generally contributed less to the net flux at lower temperatures but this
contribution of COS production increased rapidly at higher temperatures,
lower soil moisture contents and lower COS concentrations. Consequently,
measurements at higher COS concentrations (viz. 1000 ppt) always increased the
robustness of COS consumption estimates. Across the range of biomes and land
use types COS production rates co-varied with total soil nitrogen
concentrations (r = 0.52, P < 0.05) and mean annual precipitation
(r = 0.53, P < 0.05), whilst the gross COS uptake rate and the
first-order COS hydrolysis rate constant co-varied significantly with the
microbial biomass nitrogen (N) content of the soils (r = −0.74 and 0.64, P < 0.05 and P < 0.05, respectively). Collectively our findings suggest a strong interaction
between soil nitrogen and water cycling on COS production and uptake,
providing new insights into how to upscale the contribution of soils to the
global atmospheric COS budget.
... physio-sorption). Further studies conducted in sub-tropical monsoon humid climates have also reported COS compensation points above 100 ppt (Geng and Mu, 2004;Yi and Wang, 2011), but still below the atmospheric concentration (i.e. around 300 ppt, respectively). ...
Soils both emit and consume the trace gas carbonyl sulphide (COS) leading to a soil-air COS exchange rate that is the net result of two opposing fluxes. Partitioning these two gross fluxes and understanding their drivers are necessary to estimate the contribution of soils to the current and future atmospheric budget of COS.
Previous efforts to disentangle the gross COS fluxes from soils have used flux measurements on air-dried soils as a proxy for the COS emission rates of moist soils. However, this method implicitly assumes that COS uptake becomes negligible and COS emission remains steady while soils are drying. We tested this assumption by estimating simultaneously the soil COS sources and sinks and their temperature sensitivity (Q10) from soil-air COS flux measurements on fresh soils at different COS concentrations and two soil temperatures. Measurements were performed on 27 European soils from different biomes and land use types in order to obtain a large range of physical-chemical properties and identify the drivers of COS consumption and production rates.
We found that COS production rates from moist and air-dried soils were not significantly different for a given soil and that the COS production rates had Q10 values (3.96 ± 3.94) that were larger and more variable than the Q10 for COS consumption (1.17 ± 0.27). COS production generally contributed less to the net flux that was dominated by gross COS consumption but this contribution of COS production increased rapidly at higher temperature, lower soil moisture and lower COS concentrations. Consequently, measurements at higher COS concentrations (viz. 1000 ppt) always increased the robustness of COS consumption estimates. Across the range of biomes and land use types, COS production rates co-varied with total soil nitrogen (r = 0.68, P r = 0.64, P
Volatile organic compounds (VOCs) produced during the degradation of food wastes may harm to the health of people and create annoyance in adjacent communities. In this work, the VOCs emitted from the decomposition food wastes including fruit, meat and vegetable, and their microbial communities were measured in three individual 57-L reactors for 61 days. Total of 232.8, 373.5, and 191.1 μg·kg-1·h-1 VOCs with oxygenated VOCs (57.6%), volatile organic sulfur compounds (VOSCs, 58.6%) and VOSCs (54.9%) as the main group were detected during fruit, meat and vegetable fermentation, respectively. 2-Butanone (55.1%) and ethyl acetate (13.8%) were the two most abundant VOCs from fruit wastes, while dimethyl sulfide (68.0 and 26.6%) and dimethyl disulfide (89.2 and 10.1%) were in vegetable and meat wastes. The predominant Firmicutes represented 93.0-99.9% of the bacterial communities of meat decomposition, while Firmicutes and Proteobacteria were the dominant phyla throughout the fruit digestion process. Proteobacteria (16.9%-83.6%) was the dominant phylum in vegetable wastes, followed by Bacteroidetes, Firmicutes, and Actinobacteria. Malodorous VOCs emissions were highly affected by microbial activity, the abundant Weissella, Leuconostoc and Enterobacteriaceae in vegetable wastes showed correlation with carbon disulfide and dimethyl sulfide, while dominant Peptococcus, Bacteroides, Lactobacillales and Peptoniphilus in meat wastes was related to dimethyl disulfide. Overall, significant differences and correlation between VOCs emission profiles and bacterial communities among different food wastes decomposition were observed. These data contribute to a more comprehensive understanding the relationship between microbial community dynamics and malodorous VOCs emission.
Development of the high activity, promoter-free catalysts for carbonyl sulfide (COS) hydrolysis is important for the efficient utilization of various feedstocks. In this study, the Cu-based metal-organic framework HKUST-1 is synthesized by a simple and mild anodic-dissolution electrochemical method. The physical and chemical properties of the samples are characterized by several techniques, including scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis and X-ray photoelectron spectroscopy. The results reveal that the synthesis voltage plays a crucial role in controlling the morphology of the resulting HKUST-1. The obtained samples function as novel catalysts for the hydrolysis of COS. A high efficiency, approaching 100%, can be achieved for the conversion of COS at 150 °C over the optimal HKUST-1 synthesized at 25 V. This is significantly higher than that of the sample prepared by the traditional hydrothermal method. Additionally, the effects of the water temperature and the flow velocity on the hydrolysis of COS are also investigated in detail. Finally, a possible reaction pathway of COS hydrolysis over HKUST-1 is also proposed. This work represents the first example of MOFs applied to the catalytic hydrolysis of COS. The results presented in this study can be anticipated to give a feasible impetus to design novel catalysts for removing the sulfur-containing compounds. © 2017 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences
Carbonyl sulfide (COS) and dimethyl sulfide (DMS) are trace sulfur gases that contribute substantially to sulfate aerosols or cloud condensation nuclei in the upper and lower atmosphere and therefore play great roles in the earth's radiative balance. COS and DMS fluxes in rice (Oryza sativa L.) have been measured previously in rice paddies, and this study was designed to further investigate the role of aboveground plants, the rhizosphere and the root-free-soils in the exchange of COS and DMS by comparing COS and DMS fluxes among planted plots (PP), non-planted plots (NPP), plots with aboveground plants just cut before test (plants-cut plots, PCP) at three key growth stages (tillering, jointing-booting and mature stage). The average COS fluxes in NPP, PCP, and PP were 10.5 +/- 3.8,6.1 +/- 4.6, and -12.3 +/- 5.0 pmol m(-2) s(-1), suggesting that COS emission from root-free-soils (10.5 pmol m-2 s-1) was surpassed by uptake of the rhizosphere (-4.4 pmol m(-2) s(-1)) and aboveground plants (-18.4 pmol m(-2) s(-1)). DMS emission rates were 60.5 +/- 25.2, 20.2 +/- 7.3 and 30.8 +/- 10.8 pmol m(-2) s(-1) in PP, NPP and PCP, respectively. Calculated DMS emission from the aboveground plants, rhizosphere and the root-free-soils were 29.7, 10.6 and 20.2 pmol m(-2) s(-1), accounting respectively for 49.0%, 17.6% and 33.4% of total DMS emission. Directly measured COS and DMS fluxes from aboveground plants averaged -14.2 +/- 7.2 and 22.3 +/- 10.6 pmol m(-2) s(-1), approximating that of -18.4 and 29.7 pmol m(-2) s(-1) calculated by subtracting fluxes in PP and PCP, respectively. Preliminary diurnal flux observation at jointing-booting stage revealed significant linear correlation between COS uptake rates by above ground plants (MFCOS) and photosynthesis rates (Pn) with a MFCOS/Pn slope of 0.48 pmol mu mol(-1). DMS emission from the aboveground plants was also found to be significantly increased with temperature.
A series of Zn–Al hydrotalcite-like compounds (HTLCs) were synthesized by co-precipitation method. The mixed oxides derived from HTLCs were tested for the catalytic hydrolysis of carbonyl sulfide (COS) at relatively low temperatures of 50 °C. These catalysts were characterized by X-ray diffraction (XRD) and Thermogravimetry/Derivative Thermogravimetry Analysis (TG-DTA) and the results can help us to understand the effect of preparation conditions. The results showed that the Zn–Al hydrotalcite-like compounds were efficient precursor in preparing active and stable catalysts for hydrolysis of COS. The catalyst performance was strongly related to the synthesis pH and calcination temperature. The optimum condition was pH of 10, and calcination temperature of 400 °C. Although water was indispensable for hydrolysis of COS, the excess water would hinder the adsorption of COS. In general, COS was hydrolyzed to H2S, which is depending on the chemistry of the derived oxides. The end-products of hydrolysis were simple substance S and sulfate. The presence of oxygen will accelerate the formation of the final product.
The exchange of dimethyl sulfide (DMS), carbon disulfide (CS2), and dimethyl disulfide (DMDS) between soil and the atmosphere was investigated in three subtropical forests in south China, namely, a monsoon evergreen broadleaf forest (BF) in climax successional stage, a pine and broadleaf mixed forest (MF) in midsuccessional stage, and a pine forest (PF) in primary successional stage. The forest soils acted as sources for DMS with average flux in BF (1.27 ± 1.40 pmol m−2 s−1) significantly higher than those in MF (0.46 ± 0.30 pmol m−2 s−1) or in PF (0.47 ± 0.36 pmol m−2 s−1). Litter-removed plots showed 55%, 21%, and 53% lower DMS emission fluxes compared to litter-remained plots in BF, MF, and PF, respectively, suggesting the litter layer made evident contribution to DMS emission. DMS fluxes were significantly higher in rain seasons than in dry seasons. Dependence of DMS fluxes on soil temperature varied in the three forests, and significant correlations between DMS fluxes and soil temperature were only observed in BF and MF. No significant correlation was found between soil water content and DMS fluxes. However, DMS fluxes were found to be significantly correlated with soil temperature and water content together in polynomial forms with an order of 2. DMS fluxes were also exponentially correlated with CO2 fluxes. CS2 and DMDS fluxes showed no consistent direction. CS2 fluxes varied between −8.51 and 4.72 pmol m−2 s−1 and DMDS fluxes between −0.25 and 2.00 pmol m−2 s−1, respectively. No clear patterns were found for the influence of litter layer on the CS2 or DMDS fluxes.
We report the successful eddy-correlation (EC) measurement of dimethyl sulfide (DMS) fluxes using an atmospheric pressure ionization mass spectrometer (APIMS). Calculated hourly transfer velocities span the range of two widely used parameterizations. The results suggest that factors in addition to wind speed also control the flux, but some of the scatter in each wind speed interval is no doubt due to measurement uncertainties. We can at last measure the flux of a marine biogenic gas on a time scale of tens of minutes, with an accuracy of tens of percent. This enables investigations into the physical controls of air-sea gas transfer common to many important trace gas species.
The sensitivity of warm stratocumulus cloud albedo to changes in droplet
concentration, termed `cloud susceptibility,' is calculated using data
from the UKMO Meteorological Research Flight. Stratocumulus clouds in
the eastern Pacific, South Atlantic, subtropical regions of the North
Atlantic, and around the British Isles are studied. The range of
susceptibility measured is large and maritime clouds are shown to have
the largest susceptibility. Numerical simulations of the changes in
cloud radiative and microphysical properties with increasing droplet
concentration are carried out. These highlight the high sensitivity of
maritime clouds to changes in droplet concentration and the rapid
reduction in sensitivity as the cloud droplet concentration increases.
1] The uptake rates of carbonyl sulfide (COS) by soils in subtropical forests with different successional stages were measured using static chambers in Dinghushan Biosphere Reserve (DBR) in south China from July 2004 to March 2005. The three typical tropical forests studied included monsoon evergreen broad-leaf forest (BF), pine and broad-leaf mixed forest (MF) and pine forest (PF), representing forests with different succession stages in the region. COS exchange rates were also compared between the plots with litter-fall remaining (plots L) and those with litter-fall removed (plots S) in each forest. Results showed that these forest soils all acted as sinks for COS with exchange rates of À1.22 to À11.82 pmol m À2 s À1 . The MF in the midsuccessional stage had significantly higher uptake rates, and the mean exchange rates in the BF, MF, and PF were À3.90, À4.77, and À3.65 pmol m À2 s À1 , respectively. COS uptake rates at plots L were higher than those at plots S. Mean COS fluxes were significantly higher in March (À6.06 pmol m À2 s À1) than those in July (À3.60 pmol m À2 s À1), August (À3.82 pmol m À2 s À1), September (À3.45 pmol m À2 s À1), and October (À3.54 pmol m À2 s À1). Significant correlation was observed between the COS uptake rates and soil respiration rates or microbial biomass, indicating that microbial activity was an important factor controlling the soil uptake of COS. Significant correlations between COS fluxes and initial COS mixing ratios were only observed in the BF and MF. COS fluxes showed no correlation with soil temperature or water content alone in any of the three forests, but do correlate well with soil temperature and water content together in polynomial forms with an order of 2. (2007), Soil uptake of carbonyl sulfide in subtropical forests with different successional stages in south China, J. Geophys. Res., 112, D08302, doi:10.1029/2006JD008048.
1] We measured soil nitrogen (N) cycling and fluxes of N 2 O and NO in three land-use types across the metropolitan area of Phoenix, Arizona. Urbanization increased N 2 O emissions compared to native landscapes, primarily due to the expansion of fertilized and irrigated lawns. Fluxes of N 2 O from lawns ranged from 18 to 80 mg N m À2 h À1 and were significantly larger than managed xeric landscapes (2.5–22 mg N m À2 h À1) and remnant desert sites within the urban core (3.7–14 mg N m À2 h À1). In contrast, average NO fluxes from lawns were not significantly different from native desert when dry (6–80 mg N m À2 h À1 lawn; 5–16 mg N m À2 h À1 desert) and were lower than fluxes from deserts after wetting events. Furthermore, urbanization has significantly altered the temporal dynamics of NO emissions by replacing pulse-driven desert ecosystems with year-round irrigated, managed lawns. Short-term, pulse-driven emissions of NO from wetting of dry desert soils may reach 35% of anthropogenic emissions within a day after summer monsoon storms. If regional O 3 production is NO x -limited during the monsoon season, fluxes from warm, recently wet arid soils may contribute to summer O 3 episodes.
Reduced sulfur gases and optical properties were measured in the upper ocean during an Atlantic Meridional Transect cruise of the RRS James Clark Ross from England to the Falkland Islands in 1998. Sea surface concentrations of carbonyl sulfide (COS) exhibited a pronounced diel variation at low latitudes but no diel cycle at mid and high latitudes possibly because of oceanic fronts and the longer hydrolysis time constant in cold water. The highest COS concentrations were observed in coastal and upwelling areas. CS2 concentrations varied less than those of COS, and the highest concentrations were found in the North African upwelling area with decreasing concentrations both northward and southward of this maximum. Dimethylsulfide (DMS) had the largest concentrations in the upper ocean, but methyl mercaptan (CH3SH) was an important reduced sulfur species in some coastal and upwelling areas. This may be associated with high bacterial growth rates. Colored dissolved organic matter (CDOM) fluorescence and absorbance also exhibit the highest values in coastal and upwelling areas and the lowest values in the southern subtropical gyre. The results suggest that carbon disulfide (CS2) outgassed from the oceans and oxidized in the atmosphere may represent a larger source of COS to the atmosphere than the direct flux of COS across the sea-air interface.
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Using a dynamic enclosure, the exchange fluxes of carbonyl sulfide (COS) between the atmosphere and 18 soils from 10 provinces in China were investigated. The emission or uptake of COS from the soils was highly dependent on the soil type, soil temperature, soil moisture, and atmospheric COS mixing ratio. In general, with the only exception being paddy soils, the soils in this investigation acted as sinks for atmospheric COS under wide ranges of soil temperature and soil moisture. Two intensively investigated wheat soils and one forest soil, had optimal soil temperatures for COS uptake of around 15°C, and the optimal soil water content varied from 13 to 58%. The two paddy soils, exponentially COS emission fluxes increased with increasing soil temperature, and decreased COS emission fluxes with increased soil water content. However, negligible emission was found when the paddy soils were under waterlogging status. The observed compensation points for various soils were different and increased significantly with soil temperature. The laboratory simulation agreed with the preliminary field measurements for the paddy soil in Jiaxing, Zhejiang province.
COS uptake by trees, as observed under dark/light changes and under application of the plant hormone abscisic acid, exhibited a strong correlation with the CO<sub>2</sub> assimilation rate and the stomatal conductance. As the uptake of COS occurred exclusively through the stomata we compared experimentally derived and re-evaluated deposition velocities (V<sub>d</sub> for COS and CO<sub>2</sub>). We show that V<sub>d</sub> of COS is generally significantly larger than that of CO<sub>2</sub>. We therefore introduced this attribute into a new global estimate of COS fluxes into vegetation. The global COS uptake by vegetation as estimated by the new model ranges between 0.69-1.40 Tg a<sup>-1</sup>, based on the Net Primary Productivity (NPP). Taking into account Gross Primary Productivity (GPP) the deposition estimate ranges between 1.37-2.81 Tg a<sup>-1</sup> (0.73-1.50 Tg S a<sup>-1</sup>). We believe that in order to obtain accurate and reliable global NPP-based estimates for the COS flux into vegetation, the different deposition velocities of COS and CO<sub>2</sub> must be taken into account.
[1] The spatial and temporal variability of the global fluxes of carbonyl sulfide (COS) is discussed together with possible implications for total column atmospheric COS loading. The input of COS into the atmosphere is calculated as the sum of all known direct sources of COS plus the conversion of carbon disulfide (CS2) and dimethyl sulfide (DMS) to COS by atmospheric oxidation processes. Recent models are used to predict COS, CS2, and DMS release from the oceans and COS uptake by soils, plants, and oceans. This forward approach to constructing global integrated COS fluxes has a large associated range of uncertainty. The best guess global annual- integrated COS net flux estimate does not differ from zero within the range of estimated uncertainty, consistent with the observed absence of long-term trends in atmospheric COS loading. Interestingly, the hemispheric time-dependent monthly fluxes are very close in phase for the Northern and Southern Hemispheres. The monthly variation of the Northern Hemisphere flux seems to be driven primarily by high COS vegetation uptake in summer, while the monthly variation of the Southern Hemisphere flux appears to be driven mostly by high oceanic fluxes of COS, CS2, and DMS in summer.
Most of the global human population lives in urban areas where biogeochemical cycles are controlled by complex interactions between society and the environment. Urban ecology is an emerging discipline that seeks to understand these interactions, and one of the grand challenges for urban ecologists is to develop models that encompass the myriad influences of people on biogeochemistry. We suggest here that existing models, developed primarily in unmanaged and agricultural ecosystems, work poorly in urban ecosystems because they do not include human biogeochemical controls such as impervious surface proliferation, engineered aqueous flow paths, landscaping choices, and human demographic trends. Incorporating these human controls into biogeochemical models will advance urban ecology and will require enhanced collaborations with engineers and social scientists.
In situ measurements of stratospheric sulphate aerosol, reactive nitrogen and chlorine concentrations at middle latitudes confirm the importance of aerosol surface reactions that convert active nitrogen to a less active, reservoir form. This makes mid-latitude stratospheric ozone less vulnerable to active nitrogen and more vulnerable to chlorine species. The effect of aerosol reactions on active nitrogen depends on gas phase reaction rates, so that increases in aerosol concentration following volcanic eruptions will have only a limited effect on ozone depletion at these latitudes.
The green alga, Chlamydomonas reinhardtii, was grown under high and low CO2 regimes inducing significantly different activities of the extracellular carbonic anhydrase (CA). In close relation to the CA activities, the algae exhibited different consumption rates of the climatically relevant atmospheric trace gas, carbonyl sulphide (COS), thus indicating that CA is responsible for uptake of COS from the medium.
Emission rates of dimethyl sulfide (DMS), carbonyl sulfide (COS), and carbon disulfide (CS2) to the atmosphere from maize and wheat fields were measured by using the closed chamber method. DMS was a predominant sulfur gas emitted from these fields mainly through the plants. The highest DMS fluxes occurred just before the harvest of maize plants from plots treated with nitrogen fertilizer. Annual DMS emission rates were also higher in the plots treated with nitrogen fertilizer than in the plots without nitrogen fertilizer application. Annual emission rates of CS2 were higher than those of COS, because COS was absorbed by the plants. Annual sulfur emission rates from the fields were in the range of 5.6 to 17.0 mg S m y.
The exchange of carbonyl sulfide (COS) between lawn and the atmosphere was investigated by using a static enclosure under natural field conditions. The results indicated that the lawn acted as a sink for atmospheric COS and a source of dimethyl sulfide (DMS). The exchange fluxes of COS and DMS ranged between -3.24 pmol m-2 s-1 and -94.52 pmol m-2 s-1, and between 0 and 3.14 pmol m-2 s-1, respectively. The lawn was capable of continuously absorbing COS in nighttime as well as in daytime. The COS fluxes depended strongly on the ambient COS mixing ratios. The dependency of DMS emission fluxes on temperature was observed in November 2002. Soil also acted as a sink for COS during our study. However, the COS exchange fluxes of the lawn were much higher than that of the soil. The average COS and DMS fluxes were much higher in spring than in autumn and in summer. The daytime vertical profiles of COS also indicated that the lawn acted as a net sink for COS.
The uptake of atmospheric carbonyl sulfide (COS) by the lichen species Ramalina menziesii, representative for the open oak woodland in central California, was studied under laboratory conditions. By use of a dynamic cuvette system, the controlling parameters for the COS uptake were investigated under climate chamber conditions. The thallus water content, essential for the overall physiology of lichens, was found to be of basic importance for the trace gas exchange. A water content of 30% was the approximate minimum for COS uptake, with increasing activity up to a water content of 200%. Additionally, actual atmospheric mixing ratios have a significant influence on the exchange. The COS uptake was found to be a linear function of the ambient COS mixing ratio resulting in a compensation point as low as 37 ppt. A temperature optimum of 25°C was indicative of a physiological basis of the COS uptake. The inhibition of the COS consumption in the presence of a specific inhibitor for the enzyme carbonic anhydrase proved this enzyme to be of key relevance for the uptake. All these variables controlling the COS deposition were integrated into an uptake algorithm to model the exchange behavior of this lichen. The applicability of the model to field data is demonstrated. Uptake rates on a dry weight basis normalized to optimized conditions (25°C 450 ppt COS) reached 0.17+/-0.09pmolg-1s-1 (i.e. 4.2+/-2.2pmolm-2s-1 thallus surface area, respectively). The contribution of lichens to the global COS sink strength is assigned to be about 0.3 Tg a-1, representing not a major but a significant sink.
The flux of five sulfur gases to vegetation exposed to each gas individually at an ambient concentration of 0.12 μl ι−1 (5 μmoles m−3) was assessed using a whole-plant, gaseous exchange system. Total leaf flux of each gas was partitioned into leaf surface (adsorption) and internal (absorption) fractions. Internal flux varied four to sevenfold among gases, and the magnitude of flux was in the following order: sulfur dioxide > hydrogen sulfide > carbonyl sulfide > methyl mercaptan > carbon disulfide. The regression of internal flux on water solubility and molecular size accounted for 73 and 87 % of the variation in Glycine max and Phaseolus vulgaris, respectively. Leaf conductance, which was adjusted for each gas based on their respective diffusivities in air, did not improve the regression significantly. Estimates of internal flux based on the product of leaf conductance and ambient concentration may not be an accurate technique to assess the rate of absorption for all pollutant gases into the leaf interior under daylight conditions. For highly soluble and chemically reactive gases such as SO2, the latter technique tends to underestimate flux by 50%, which may result from a mean SO2 diffusive path length that is less than that for water vapor. The relationship between flux and the physicochemical properties of a gas may provide a technique for screening atmospheric emissions for their potential toxicity to vegetation.
The exchange of carbonyl sulfide (OCS) and CS2 between the atmosphere and the pedosphere was investigated in a temperate zone spruce forest in the Solling Mountains (51°N), Germany during three field campaigns in 1999. Dynamic (flow-through) chambers were used to measure the OCS and carbon disulfide (CS2) exchange fluxes between the soil and the atmosphere. All measurements showed a net OCS flux from the atmosphere into the soil. On average (± standard error of the mean), the OCS uptake rate of the soil was 0.81(±0.03)pmolm-2s-1 and the total range was between 0.23 and 1.38pmolm-2s-1. CS2 fluxes varied between an uptake of 0.11pmolm-2s-1 and an emission of 0.23pmolm-2s-1. Therefore, CS2 is emitted by the soil in a nearly balanced mean flux of 0.01(±0.01)pmolm-2s-1. Slight dependencies of the OCS flux on soil temperature and soil water content were detected. The fluxes varied by about a factor of 2 over a distance of 10m. A comparison of the OCS fluxes between soil and atmosphere with the fluxes observed simultaneously above the canopies revealed that only 1% of the OCS which was taken up by the whole forest ecosystem is deposited in the soil. The impact of the CS2 exchange between soil and atmosphere for the whole ecosystem flux of CS2 was even more negligible.
Soil samples from arable land were investigated for their exchange of carbonyl sulfide (COS) with the atmosphere under controlled conditions using dynamic cuvettes in a climate chamber. The investigated soil type acted as a significant sink for the trace gas COS. Atmospheric COS mixing ratios, temperature, and soil water content were found to be the physicochemical parameters controlling the uptake. Emission was never observed under conditions representative of a natural environment. The observed compensation point (i.e., an ambient concentration where the consumption and production balance each other and the net flux is zero) for the uptake was about 53 parts per trillion. Uptake rates ranged between 1.5 and 10.3 pmolm-2s-1. The consumption of COS by the soil sample depended on the physiological activity of the microorganisms in the soil, as indicated by a clear optimum temperature and by a drastic inhibition in the presence of the enzyme inhibitor 6-ethoxy-2-benzothiazole-2-sulfonamide (EZ), a specific inhibitor for carbonic anhydrase.
The flux of a trace gas between soil and atmosphere is usually the result of simultaneously operating production and consumption processes. The compensation concentration is the concentration at which the rate of production equals the rate of consumption so that the net flux between soil and atmosphere is zero. Production and uptake may be due to different processes, which are at least partially known for some of the trace gases, and which may be differently regulated. The direction and the magnitude of the flux between soil and atmosphere is a function of both the compensation concentration and the trace gas concentration in the ambient atmosphere. Compensation and/or ambient concentrations may fluctuate and thus may have a strong impact on the flux of CO, NO and NO2, and to a smaller extent also on that of H2. Compensation concentrations also exist for N2O and OCS, but are too high to affect the flux under field conditions. Compensation concentrations have so far not been demonstrated for the flux of CH4. However, the uptake of CH4 by soil exhibits a threshold concentration below which no uptake occurs.
Biogenic sulfur gases emitted from Chinese rice paddies were measured with a laboratory incubation and a closed chamber method in the field. Six speciations of sulfur-containing gases were detected in both conditions: hydrogen sulfide (H2S), carbonyl sulfide (COS), methyl mercaptan (CH3SH), carbon disulfide (CS2), dimethyl sulfide (CH3SCH3 or DMS) and dimethyl disulfide (CH3SSCH3 or DMDS). Among them, DMS comprised the major part of the sulfur emission. Emission of sulfur gases from different paddy soils exhibit high spatial and temporal variability. The emission of volatile sulfur gases increased with application of organic manure and positively correlated with the total sulfur content in the soil. The diurnal and seasonal variations of total volatile sulfur gases and DMS indicate that their emissions were greatly influenced by the air temperature and the activity of the rice plant. The annual emission of total volatile sulfur gases from the Nanjing rice paddy field ranged from 4.0 to 9.5 mg S m−2 year−1, that of DMS ranged from 3.1 to 6.5 mg S m−2 year−1.
This study investigates the distribution and magnitudes of the global sources and sinks of carbonyl sulfide (OCS), hydrogen sulfide (H2S), carbon disulfide (CS2), and dimethyl sulfide (DMS). For OCS, H2S and CS2, balanced mass budgets are proposed. An inventory of sources has been assembled for dimethyl sulfide (DMS). For OCS, total global sources and sinks are estimated as 1.31±0.25 and 1.66±0.79 Tg a−1, respectively. Global sources and sinks of H2S are estimated as 7.72±1.25 and 8.50±2.80 Tg a−1, respectively. Estimates of sources and sinks of CS2 are 0.66±0.19 and 1.01±0.45 Tg a−1, respectively. For DMS only a sources estimate has been prepared, 24.45±5.30 Tg a−1. The budgets for OCS and DMS seem relatively secure, whilst those for H2S and CS2 contain much greater uncertainty. For DMS, more information on emissions from plants is required. For the other three species, data on soils and vegetation emissions are sparse, although the most urgent priorities might be to establish the role of freshwater wetlands and soils in non-tropical areas.
Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism.
Carbonic anhydrase (CA), isolated from pea leaves, was found to consume carbonyl sulphide (COS), a climatic relevant trace gas in the atmosphere. The isolated enzyme, free of other carboxylases, showed a very high affinity towards this substrate. The experiments confirm that CA is the key enzyme for the consumption of COS in higher plants. Furthermore, the identification of this enzyme furthers our understanding of additional sinks for COS, which are needed to understand the balance of known global sources.
Emission of volatile sulfur gases from waterlogged paddy soils and upland soils of China and Japan was studied in the laboratory. Emission of hydrogen sulfide (H2S), carbonyl sulfide (COS), methyl mercaptan (CH3SH), dimethyl sulfide (DMS), carbon disulfide (CS2) and dimethyl disulfide (DMDS) were detected. Emission of sulfur gases from paddy soil was more than that from upland, and emission from the Chinese paddy soils was more than that from Japanese. At the same soil, emission of sulfur gases, when both organic manure and chemical fertilizer were applied was higher than when only organic manure or only chemical fertilizer was applied. Under anaerobic conditions, detected biogenic sulfur gases were far more than that under aerobic conditions, H2S was the most obvious. The results have also shown that, at higher temperature, emission and expiration rate of volatile sulfur gases were higher than that at lower temperature.
Carbonyl sulfide (COS) exchange fluxes between a lawn soil and the atmosphere as well as influencing factors (temperature and water content of soil) were investigated using a static cuvette. The optimal soil temperature and water content for COS consumption were about 298 K and 12.5%, respectively. The converting products of the consumed COS in the lawn soil were researched using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The peaks of gas-phase products of CO2 and surface , HS-, , , and species were observed. The possible mechanism of COS conversion in the lawn soil was discussed. The conversion rates of consumed COS into water-soluble sulfate in the lawn soil were studied by ion chromatography (IC). The experimental results show that about 50% sulfur from the soil consumed COS was eventually converted into water-soluble sulfate.
Carbonyl sulfide (OCS) and dimethyl sulfide (DMS) are important trace gases contributing to sulfate aerosol formation in the lower and upper atmosphere and hence greatly impacting global radiative balance. In the present study the exchange of OCS and DMS between rice (Oryza sativa L.) paddy fields and the atmosphere was studied in subtropical China from November 2004 to July 2005. OCS and DMS fluxes were compared between the planted and non-planted paddy fields, and between dry and waterlogged soils. The rice paddy fields were found to be a net sink for OCS and a source for DMS, with an uptake rate of 12.1 ± 16.0 pmol m−2 s−1 for OCS and an emission rate of 25.9 ± 35.2 pmol m−2 s−1 for DMS. OCS fluxes varied significantly between non-planted dry and waterlogged soils, with an uptake rate of 11.4 ± 7.1 pmol m−2 s−1 for non-planted dry soils and an emission rate of 9.0 ± 5.4 pmol m−2 s−1 for non-planted waterlogged soils. For DMS the variation between non-planted dry and waterlogged soils was not significant. Both OCS and DMS fluxes showed significant differences between the planted and non-planted waterlogged soils. For OCS, the planted waterlogged soil acted as a sink with an uptake rate of 29.0 ± 25.7 pmol m−2, but the non-planted waterlogged soil acted as a source with an emission rate of 9.0 ± 5.4 pmol m−2 s−1. For DMS, both the planted and non-planted waterlogged soils acted as sources, with an emission rate of 51.2 ± 37.5 pmol m−2 s−1 for the planted waterlogged soil, which was significantly higher than that for the non-planted waterlogged soil (3.8 ± 2.8 pmol m−2 s−1). OCS and DMS exchange rates differed significantly at different rice growth stages, with the highest fluxes at the jointing-booting stage. The potential factors causing the variations between the different treatments are also discussed. This work revealed that rice paddy field in subtropical China acts as a sink for OCS and an emission source for DMS as a whole and further investigation on the influence of soil microorganisms and soil redox potential on the OCS and DMS fluxes in rice paddy field are needed.
The exchange rates of carbonyl sulfide (COS) and dimethyl sulfide (DMS) between 19 tree species and the atmosphere were investigated under natural field conditions using a static enclosure. Most of the investigated trees acted as sinks for atmospheric COS and a few trees, such as Salix matsudana Koidz. and Ulmus pumila L. could emit COS. The distinct diurnal variations of COS uptake for the investigated trees indicated that COS uptake strongly depended on photosynthetically active radiation (PAR). The average COS uptake rates for most species were much higher in summer than in autumn, indicating leaf age and temperature also might be the important influencing factors for COS uptake. Platanus orientalis L., Sophara japonica var. P. loud., Magnolia denudata Desr. and Sophora japonica L. were capable of continuously absorbing COS in daytime as well as in nighttime. For Platanus orientalis L., the maximal COS uptake rate and DMS emission rate on a single leaf area basis were −15.29 and 0.42 pmol m−2 s−1, respectively. The COS exchange fluxes for the investigated tree species depended strongly on the ambient COS mixing ratios. Significant correlation between DMS emissions and temperature was observed in summer.
The major source of cloud-condensation nuclei (CCN) over the oceans
appears to be dimethylsulphide, which is produced by planktonic algae in
sea water and oxidizes in the atmosphere to form a sulphate aerosol.
Because the reflectance (albedo) of clouds (and thus the earth's
radiation budget) is sensitive to CCN density, biological regulation of
the climate is possible through the effects of temperature and sunlight
on phytoplankton population and dimethylsulphide production. To
counteract the warming due to doubling of atmospheric CO2, an
approximate doubling of CCN would be needed.
We show that the marine algae Mantoniella squamata, Prymnesium parvum, and Amphidinium klebsii take up carbonyl sulfide (COS) from their surrounding medium. Inhibitor studies confirm that this COS uptake is catalyzed by the enzyme carbonic anhydrase, which was not detectable with conventional methods. As shown for M. squamata, the COS uptake can be dependent on the growth conditions. Furthermore, COS uptake shows a clear positive correlation with the COS concentration in the growth medium. The value of K1/2 for the COS uptake was estimated to be around 222 mol/m3. The COS consumption by the marine algae species investigated was estimated to be negligible compared to the photoproduction and hydrolysis of COS in seawater.
The soil/plant/atmosphere exchange of carbonyl sulfide (COS) was investigated in an open oak woodland ecosystem at a rural site in northern California. Measurements of atmospheric concentrations of COS were made in June and in December 1994. We found a significant diel cycle with a drop of COS levels by approximately 150ppt during the night in both seasons. The mean COS daytime background mixing ratios showed a distinct seasonal difference with 465±77ppt in summer and 375±56ppt in winter. The nighttime bulk COS flux into the ecosystem was estimated using a micrometeorological model. To address the observed depletion of COS during stable nocturnal boundary layer conditions, the potential of various ecosystem compartments to act as a sink for COS was investigated. Studies using dynamic enclosures flushed with ambient air excluded vegetation as an important sink during nighttime due to high stomatal resistance. Results from soil chamber measurements indicate that the soil can act as a dominant sink for atmospheric COS.
Atmospheric aerosols play important roles in climate and atmospheric chemistry: They scatter sunlight, provide condensation
nuclei for cloud droplets, and participate in heterogeneous chemical reactions. Two important aerosol species, sulfate and
organic particles, have large natural biogenic sources that depend in a highly complex fashion on environmental and ecological
parameters and therefore are prone to influence by global change. Reactions in and on sea-salt aerosol particles may have
a strong influence on oxidation processes in the marine boundary layer through the production of halogen radicals, and reactions
on mineral aerosols may significantly affect the cycles of nitrogen, sulfur, and atmospheric oxidants.
Higher plants represent a significant sink for atmospheric carbonyl sulfide (COS) and a potential source of dimethyl sulfide (DMS). In the present work, COS uptake was investigated on various plant species (Quercus robur, Juniperus excelsa, Hibiscus spec., Sorghum bicolor) differing in the activities of carbonic anhydrase (CA), the enzyme recognized responsible for COS consumption. COS uptake was observed for all plant species, and the range of COS consumption was 1.5-25 pmol m-2 s-1 (deposition velocity 1.2-10.6 mm s-1). The COS uptake was found to be light-independent, but was strongly under stomatal control. For the C3 plant species the uptake rates were well correlated with the inherent capacity of CA, a fact that may confer a comfortable tool to model COS uptake by plants, and ultimately may help to decrease the uncertainty in estimates of the global COS sink strength of vegetation. S. bicolor, owing a C4 metabolism and respective low CA activity, exhibited a relatively high COS uptake rate as compared to the C 3 plants. Potential reasons for this deviation are discussed. Emission of DMS was species-specific and was only observed in case of Hibiscus spec. under light conditions.
Atmospheric carbonyl sulfide COS concentrations were measured by three analytical systems during the Chemical Instrumentation Test and Evaluation (CITE 3) project. The three systems all used cryogenic sample preconcentration and gas chromatographic (GC) separation but differed in the method of detection. The FPD system used a flame photometric detector, the MS system used a mass selective detector, and the ECD-S system used a fluorinating catalyst followed by an electron capture detector. With the FPD system, we found a mean COS concentration of 510 ppt over the North Atlantic and 442 ppt over the Tropical Atlantic. With the ECD-S system, we found a mean COS concentration of 489 ppt over the North Atlantic and 419 ppt over the Tropical Atlantic. All three systems registered a latitudinal gradient in atmospheric COS of between 1.6 and 2.0 ppt per degree of latitude, with increasing COS concentrations northward which was similar to the gradient measured by Bingemer et al. (1990). It is difficult to reconcile the measured latitudinal concentration gradient with present theories of the global COS budget since the largest sink of COS is thought to be a flux to land plants, most of which are in the northern hemisphere.
The analogues carbon dioxide (CO(2)), carbonyl sulfide (COS) and carbon disulfide (CS(2)) have been useful as substrate probes for enzyme activities. Here we explored the affinity of the enzyme carbonic anhydrase for its natural substrate CO(2), as well as COS and CS(2) (1) by in vitro kinetic metabolism studies using pure enzyme and (2) through mortality bioassay of insects exposed to toxic levels of each of the gases during carbonic anhydrase inhibition. Hydrolysis of COS to form hydrogen sulfide was catalysed rapidly showing parameters K(m) 1.86 mM and K(cat) 41 s(-1) at 25 degrees C; however, the specificity constant (K(cat)/K(m)) was 4000-fold lower than the reported value for carbonic anhydrase-catalysed hydration of CO(2). Carbonic anhydrase-mediated CS(2) metabolism was a further 65,000-fold lower than COS. Both results demonstrate the deactivating effect toward the enzyme of sulfur substitution for oxygen in the molecule. We also investigated the role of carbonic anhydrases in CO(2), COS and CS(2) toxicity using a specific inhibitor, acetazolamide, administered to Tribolium castaneum (Herbst) larvae via the diet. CO(2) toxicity was greatly enhanced by up to seven-fold in acetazolamide-treated larvae indicating that carbonic anhydrases are a key protective enzyme in elevated CO(2) concentrations. Conversely, mortality was reduced by up to 12-fold in acetazolamide-treated larvae exposed to COS due to reduced formation of toxic hydrogen sulfide. CS(2) toxicity was unaffected by acetazolamide. These results show that carbonic anhydrase has a key role in toxicity of the substrates CO(2) and COS but not CS(2), despite minor differences in chemical formulae.
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Air-soil exchange of DMS, CS 2 and DMDS in three subtropical forests in south China Exchange of carbonyl sulfide (OCS) and dimethyl sulfide (DMS) between rice paddy fields and the atmosphere in subtropical China
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- X M Wang
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Aerosols, their direct and indirect No. 5 Carbonyl sulfide (COS) and dimethyl sulfide (DMS) fluxes in an urban lawn and adjacent bare soil in Guangzhou, China 789 effects. In: IPCC, Climate Change 2001. The Scientific Basis
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Emissions of DMS, OCS, and CS 2 from maize and wheat fields
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Air-soil exchange of DMS, CS 2 and DMDS in three subtropical forests in south China
- Z G Yi
- X M Wang
- M A Ouyang
- D Q Zhang
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2010. Air-soil exchange of DMS, CS 2 and DMDS in three
subtropical forests in south China. Journal of Geophysical
Research, 115: D18302. DOI: 10.1029/2010JD014130.