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1.
Biocovers are an alternative for mitigating fugitive and residual emissions of methane from landfills. In this study, we evaluated the performance of two experimental passive methane oxidation biocovers (PMOBs) constructed within the existing final cover of the St-Nicéphore landfill (Quebec, Canada). The biocovers were fed in a controlled manner with raw biogas and surface fluxes were obtained using static chambers. This enabled calculating mass balances of CH4 and oxidation efficiencies (f o_MB). Most of the time, f o_MB????92?% were obtained for loadings as high as 818?g?CH4?m?2?day?1 (PMOB-2) and 290?g?CH4?m?2?day?1 (PMOB-3B). The lowest efficiencies (f o_MB?=?45.5?% and 34.0?%, respectively) were obtained during cold days (air temperature ~0?°C). Efficiencies were also calculated using stable isotopes (f o_SI); the highest f o_SI were 66.4?% for PMOB-2 and 87.3?% for PMOB-3B; whereas the lowest were 18.8?% and 23.1?%, respectively. However, f o_SI values reflect CH4 oxidation up to a depth of 0.10?m, which may partly explain the difference in regards to mass balance-derived efficiencies. Indeed, it is expected that a significant fraction of the total CH4 oxidation occurs within the zone near the surface, where there is greater O2 availability. The influence of the values of fractionation factors ?? ox and ?? trans were also evaluated in this paper.  相似文献   

2.
The microbial oxidation of methane in landfill cover soils offers great potential to reduce methane emissions from landfills. High methane degradation rates can only be accomplished if the supply of atmospheric oxygen to the methanotrophic community is adequate. Thus, if environmental variables such as pH or nutrient status are not limiting, system performance is suggested to be governed by the share of pores available for gas transport. Diffusion tests as well as column studies were conducted to investigate the effect of air-filled porosity and degree of compaction on diffusivity and methane oxidation efficiency. Results show that the effective diffusion coefficient governing oxygen migration through soil is exponentially related to air-filled porosity space and can be significantly decreased by compaction. Discontinuity and tortuosity of the pore system strongly impeded diffusive migration at air-filled porosities below 10%. In the column study, soil gas composition and methane oxidation rates correlated with both the degree of compaction and the magnitude of advective bottom flux. Low aeration and hence low methane oxidation rates prevailed at high compaction rates and/or high bottom fluxes whereas high rates could be maintained at lower fluxes and/or low compaction rates. At a low degree of compaction (75% of the Proctor density), fluxes of 3.5 g CH4 m−2 h−1 could be fully oxidized at all times by a sandy loam, the capacity limit of which was not reached during the experiment. Our studies suggest that soils intended for use as methane-oxidizing biocovers are to maintain an air-filled porosity of at least 14 vol.%. At low and medium degree of compaction, this is provided by sands, loamy sands, sandy loams and some of the coarsely textured loams.  相似文献   

3.
Intermittent irrigation is an important option for mitigating CH4 emissions from paddy fields. In order to better understand its controlling processes in CH4 emission, CH4 fluxes, CH4 production and oxidation potentials in paddy soils, and 13C-isotopic signatures of CH4 were observed in field and incubation experiments. The relative contribution of acetate to total CH4 production (fac) and fraction of CH4 oxidized (fox) in the field was also calculated using the isotopic data. At the beginning of the rice season, the theoretical ratio of acetate fermentation: H2/CO2 reduction = 2:1 was reached, however, in the late season H2/CO2-dependent methanogenesis became dominant. Compared to continuous flooding, intermittent irrigation significantly reduced CH4 production potential and slightly decreased fac-value, indicating methanogens, particularly acetate-utilizing methanogens, were inhibited. CH4 oxidation was very important, especially in paddy fields under intermittent irrigation where 19–83% of the produced CH4 was oxidized. Intermittent irrigation enhanced CH4 oxidation potential slightly and raised fox-value significantly relative to continuous flooding. Intermittent irrigation significantly decreased CH4 flux creating a more positive δ13C-value of emitted CH4 by 12–22‰. A significant negative correlation was found between CH4 fluxes and values of δ13CH4 suggesting that the less the CH4 oxidation, the higher the CH4 emission, and the lower the δ13C-value of emitted CH4. Collectively, the findings show that intermittent irrigation reduced the seasonal CH4 production potential by 45% but increased the fraction of CH4 oxidized by 45–63%, thus decreasing the seasonal CH4 emission from the paddy fields by 71%, relative to continuous flooding.  相似文献   

4.
Methanotrophy of arable soils is affected by N fertilization, but the knowledge about the effect of oxygen level is poorly understood; soil aeration can fluctuate and zones of low oxygen are widespread in soil. We monitored CH4 oxidation in three mineral soils (Eutric Cambisol, Haplic Podzol, Mollic Gleysol) under laboratory conditions by varying the O2 level (from 20 to 2% O2), with or without NH4+ (100 mg N kg?1). In controls (without NH4+), CH4 was oxidized completely in the O2 range from oxia (20% O2) to high hypoxia (5% O2), while the process was inhibited under microoxia (2% O2). Ammonium application decreased CH4 consumption in all soils. This negative effect was stronger at 20% and 2% O2 than under hypoxia. The highest CH4 oxidation rates and the shortest initial (lag) phases in both control and NH4+-amended soils were observed under high (5% O2) and low (10% O2) hypoxia.  相似文献   

5.
Methane oxidation in a cover soil of a landfill located in a boreal climate was studied at temperatures ranging from 1-19 °C and with water content of 7-34% of dry weight (dw), corresponding to 17-81% of water-holding capacity (WHC) in order to better understand the factors regulating CH4 oxidation at low temperatures. CH4 consumption was detected at all the temperatures studied (1-19 °C) and an increase in CH4 consumption rate in consecutive incubations was obtained even at 1 °C, indicating activation or increase in enzymes and/or microorganisms responsible for CH4 oxidation. CH4 consumption was reduced with low water content (17%WHC) at all temperatures. The response of CH4 consumption to temperature was high with Q10 values from 6.5 to 8.4 and dependent on water content: at 33%WHC or more an increase in water content was accompanied by a decrease in Q10 values. The responses of CH4 consumption to water content varied at different temperatures so that at 1-6 °C, CH4 consumption increased along with water content (33-67%WHC) while at 12-19 °C the response was curvilinear, peaking at 50%WHC. CH4 consumption was less tolerant (higher Q10 values; 6.5-8.4) of low temperatures compared to basal respiration (Q10 values for CO2 production and O2 consumption 3.2-4.0). Overall, the present results demonstrate the presence of CH4-oxidizing microorganisms, which are able to consume CH4 and to be activated or grow at low temperatures, suggesting that CH4 oxidation can reduce atmospheric CH4 emissions from methanogenic environments even in cold climates.  相似文献   

6.
Straw application is a common practice in rice agriculture, but its effect on stable carbon isotopes (δ13C) in each process of CH4 emission, relative contribution of acetate to CH4 production (Fac), and fraction of the CH4 that is oxidized (Fox) in the winter season is not well known. We investigated CH4 production and oxidation potentials in paddy soil, CH4 concentrations in soil pore water and floodwater, and CH4 emission as well as their δ13C from a continuously flooded paddy field with rice straw application (RSA) during the 2007 and 2008 winter seasons and quantified the Fac and Fox using the isotopic data. RSA significantly increased CH4 emission (p < 0.05) but made δ13CH4 (emission) lower by 5–8‰. RSA obviously increased CH4 concentrations in soil pore water and floodwater, but it played a slight role in porewater δ13CH4 while caused floodwater δ13CH4 4‰ lower. A relatively low contribution of acetate-dependent methanogenesis (about 50%) was observed, and RSA slightly increased Fac (about 0–10%) at a relatively low temperature whereas greatly decreased it (about 10–20%) at a high temperature. Floodwater CH4 was much more 13C-enriched than porewater CH4 (p < 0.05), suggesting that about 60–70% of the CH4 was oxidized at the soil–water interface. Fox generally decreased in the winter season and it was reduced by RSA (about 10%). Soil temperature was positively correlated with CH4 flux and CH4 flux was negatively related to δ13CH4 (emission), suggesting that temperature might be an important factor influencing Fox, thus CH4 emission and δ13CH4 (emission). The findings suggest that RSA significantly increased CH4 production while little affected CH4 oxidation, thus decreasing Fox. Moreover, the effect of RSA on methanogenic pathway might be controlled by soil temperature, and RSA generally reduced Fac and Fox was the main reason for the emitted CH4 depleted in 13C.  相似文献   

7.
We describe experiments to better understand how CH4 oxidation rates by different methanotroph communities respond to changing CH4 concentrations. We used a novel system of automatically monitored chambers to investigate the response of CH4 oxidation rates in a New Zealand pasture and adjacent pine forest soil exposed to varying atmospheric CH4 concentrations.Type II methanotrophs that dominate CH4 oxidation in the forest soil became progressively saturated as CH4 concentrations rose from ambient (1.8 ppmv) to 570 ppmv, as shown by a decrease in uptake efficiency from 20% to 2% removal. By contrast, CH4 oxidation in the pasture soil where Type I methanotrophs dominate increased in proportion to the increase in CH4 inlet concentration, oxidising about 2% of the inlet CH4 flux throughout. Modelling based on Michaelis-Menten kinetics revealed that low-affinity (Type I) methanotrophs were solely responsible for CH4 oxidation in pasture soils, whereas high affinity (Type II) methanotrophs only contributed about 10% of the CH4 oxidation in the forest soil. Increased aeration status using a soil–perlite (1:1) mixture doubled CH4 oxidation rates at both ambient (1.8 ppmv) and 40 ppmv atmospheric CH4. A similar volcanic soil previously exposed for 8 y to high CH4 fluxes from a landfill had removal efficiencies consistently above 95% for atmospheric CH4 concentrations up to 7500 ppmv when the CH4 oxidation rate was7000 μg CH4 kg−1soil h−1.  相似文献   

8.
In soil incubation experiments we examined if there are differences in the kinetic parameters of atmospheric methane (CH4) oxidation in soils of upland forests and forested peatlands. All soils showed net uptake of atmospheric CH4. One of the upland forests included also managed (clear-cut with or without previous liming or N-fertilization) study plots. The CH4 oxidation in the forested peat soil had a higher Km (510 μl l−1) and Vmax (6.2 nmol CH4 cm−3 h−1) than the upland forest soils (Km from 5 to 18 μl l−1 and Vmax from 0.15 to 1.7 nmol CH4 cm−3 h−1). The forest managements did not affect the Km-values. At atmospheric CH4 concentration, the upland forest soils had a higher CH4 oxidation activity than the forested peat soil; at high CH4 concentrations the reverse was true. Most of the soils oxidised CH4 in the studied pH range from 3 to 7.5. The pH optimum for CH4 oxidation varied from 4 to 7.5. Some of the soils had a pH optimum for CH4 oxidation that was above their natural pH. The CH4 oxidation in the upland forest soils and in the peat soil did not differ in their sensitivities to (NH4)2SO4 or K2SO4 (used as a non-ammonium salt control). Inhibition of CH4 oxidation by (NH4)2SO4 resulted mainly from a general salt effect (osmotic stress) though NH4+ did have some additional inhibitory properties. Both salts were better inhibitors of CH4 oxidation than respiration. The differences in the CH4 oxidation kinetics in the forested peat soil and in the upland forest soils reveal that there are differences in the physiologies of the CH4 oxidisers in these soils.  相似文献   

9.
《Soil biology & biochemistry》2001,33(12-13):1625-1631
Forest soils are an important sink for atmospheric CH4 but the contribution of CH4 oxidation, production and transport to the overall CH4 flux is difficult to quantify. It is important to understand the role these processes play in CH4 dynamics of forest soils, to enable prediction of how the size of this sink will respond to future environmental change. Methane oxidation, production and transport were investigated for a temperate forest soil, previously shown to be a net CH4 consumer, to determine the extent to which physical and biological processes contributed to the net flux. The sum of oxidation rates for soil layers were significantly greater (P<0.05) than for the intact soil cores from which the layers were taken. Combined with the immediate inhibition of CH4 uptake on waterlogging soils, the findings suggested that soil CH4 diffusion was an important regulator of CH4 uptake. In support of this, a subsurface maximum for CH4 oxidation was observed, but the exact depth of the maximum differed when rates were calculated on a mass or on an areal basis. Markedly varying potential CH4 uptake activities between soil cores were masked in intact core rates. Potential CH4 oxidation conformed well to Michaelis–Menten kinetics but Vmax, Kt and aA○ values varied with depth, suggesting different functional methanotrophic communities were active in the profile. The presence of monophasic kinetics in fresh soil could not be used to infer that the soil was exposed only to CH4 mixing ratios ≤ atmospheric, as challenging soils with 20% CH4 in air did not induce low-affinity oxidation kinetics. Atmospheric CH4 oxidation potentials exceeded production potentials by 10–220 times. The results show that the forest soil CH4 flux was dominated by CH4 oxidation and transport, methanogenesis played only a minor role.  相似文献   

10.
Methane oxidation in temperate soils: effects of inorganic N   总被引：1，自引：0，他引：1  
Additions of inorganic nitrogen (N) to an oak soil with significant potential for methane (CH4) oxidation resulted in differential reduction in CH4 oxidation capacity depending on N species added. Nitrate, rather than nitrite or ammonium, proved to be the strongest inhibitor of CH4 oxidation in oak soil. Both high (CH4 at 10 μl l−1) and low (CH4 at 5 ml l−1) affinity CH4 oxidation in oak soil was completely inhibited at a nitrate concentration similar to that present in an alder soil from the same experimental site. The alder soil showed no capacity for low affinity CH4 oxidation. A ‘low nitrate’ forest soil (oak) showed high affinity, low capacity CH4 oxidation upto around 1 ml l−1 CH4, above which both high and low affinity CH4 oxidation became apparent following a lag phase, indicating either an induced high affinity uptake mechanism or the existence of distinct low affinity and high affinity methanotroph populations. High affinity CH4 oxidation became saturated at CH4 concentrations >500 μl l−1, while low affinity CH4 oxidation became saturated at ∼30 ml l−1 CH4. In a ‘high nitrate’ forest soil (alder), CH4 oxidation appeared to be due to high affinity CH4 oxidation only and became undetectable at CH4 concentrations >5 ml l−1.  相似文献   

11.
Emissions of N2O and CH4 and CH4 oxidation rates were measured from Lolium perenne swards in a short-term study under ambient (36 Pa) and elevated (60 Pa) atmospheric CO2 at the Free Air Carbon dioxide Enrichment experiment, Eschikon, Switzerland. Elevated pCO2 increased (P<0.05) N2O emissions from high N fertilised (11.2 g N m−2) swards by 69%, but had no significant effect on net emissions of CH4. Application of 13C-CH4 (11 μl l−1; 11 at.% excess 13C) to closed chamber headspaces in microplots enabled determination of rates of 13C-CH4 oxidation even when net CH4 fluxes from main plots were positive. We found a significant interaction between fertiliser application rate and atmospheric pCO2 on 13C-CH4 oxidation rates that was attributed to differences in gross nitrification rates and C and N availability. CH4 oxidation was slower and thought to be temporarily inhibited in the high N ambient pCO2 sward. The most rapid CH4 oxidation of 14.6 μg 13C-CH4 m−2 h−1 was measured in the high fertilised elevated pCO2 sward, and we concluded that either elevated pCO2 had a stimulatory effect on CH4 oxidation or inhibition of oxidation following fertiliser application was lowered under elevated pCO2. Application of 14NH415NO3 and 15NH415NO3 (10 at.% excess 15N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N2O emissions. Inhibition of CH4 oxidation in the high fertilised ambient pCO2 sward, due to competition between NH3 and CH4 for methane monooxygenase enzymes or toxic effects of NH2OH or NO2− produced during nitrification, was hypothesised to increase gross nitrification (12.0 mg N kg dry soil−1) and N2O emissions during nitrification (327 mg 15N-N2O m−2 over 11 d). Our results indicate that increasing atmospheric concentrations of CO2 may increase emissions of N2O by denitrification, lower nitrification rates and either increase or decrease the ability of soil to act as a sink for atmospheric CH4 depending on fertiliser management.  相似文献   

12.
《Soil biology & biochemistry》2001,33(12-13):1613-1623
Methane is an important greenhouse gas and CH4 oxidation in soil represents a significant sink for this gas. High capacity CH4 oxidation potentials and molecular profiles of CH4 oxidizing bacteria in soil were compared for five land-use treatments at a fully replicated experimental site within the Gisburn Forest Experiment, to assess the effects of land-use on both the potential activity of CH4 oxidizing bacteria and their diversity. Forestry land-use was found to have a highly significant effect on CH4 oxidation potentials. Highest CH4 oxidation potentials were found in soils collected under stands of oak, in grassland plots, and in one soil under Norway spruce. A negative relationship between soil water nitrate concentration and CH4 oxidation capacity was evident across the experimental site, with the high nitrate soils under stands of alder exhibiting little or no capacity for CH4 oxidation even at optimal temperature and water content. Molecular profiles indicated that a diverse range of bacteria with the potential to oxidize CH4 were present in all soils, however no clear correlation with CH4 oxidation potential was identified.  相似文献   

13.
《Soil biology & biochemistry》2001,33(7-8):965-971
Laboratory experiments were conducted to find out under which conditions the soil from Italian rice fields could change from a source into a sink of atmospheric CH4. Moist (30% H2O=68% of the maximum water holding capacity (whc)) rice field soil oxidized CH4 with biphasic kinetics, exhibiting both a low (145 ppmv CH4) and a high (20,200 ppmv CH4) Km value and Vmax values of 16.8 and 839 nmol gdw−1 h−1, respectively. The activity with the low Km allowed the oxidation of atmospheric CH4. Uptake rates of high CH4 concentrations (16.5% v/v) and of O2 linearly decreased with aggregate size of soil between 2 and 10 mm. Atmospheric CH4 (1.8 ppmv) was consumed in soil aggregates <6 mm, but soil aggregates >6 mm released CH4 into the atmosphere. Similarly, net uptake of atmospheric CH4 turned into net release of CH4 when the soil moisture was decreased below a water content of about 20% whc. The uptake rate of atmospheric CH4 increased threefold when the soil was amended with sterile quartz sand. Flooded microcosms with non-amended and quartz-amended soil emitted CH4 into the atmosphere. The CH4 emission rate increased when the flux was measured under an atmosphere of N2 instead of air, indicating that 30–99% of the produced CH4 was oxidized in the oxic soil surface layer. Removal of the flood water resulted in increase of CH4 emission rates until a water content of about 75–82% whc was reached, and subsequently in a rapid decrease. However, the soil microcosms never showed net uptake of atmospheric CH4. Our results show that the microorganisms consuming atmospheric CH4 were inactivated at an earlier stage of drainage than the microorganisms producing CH4, irrespective of the soil porosity which was adjusted by addition of quartz sand. Hence, it is unlikely that the Italian rice fields can act as a net sink for atmospheric CH4 even when drained.  相似文献   

14.
Methane emissions from soils are the net result of two processes: methane (CH4) production and CH4 oxidation. In order to understand how both processes respond to environmental changes, it is necessary to distinguish between CH4 production and oxidation. In bacterial cultures and small soil samples, difluoromethane (CH2F2) was found to inhibit CH4 oxidation reversibly, without affecting CH4 production. Hence, CH2F2 allows the study of CH4 production directly and of CH4 oxidation indirectly. To our knowledge, however, the inhibitory effect of CH2F2 within soil columns has not yet been evaluated. We therefore tested which CH2F2 concentration is needed for complete inhibition of CH4 oxidation in reconstructed 28 cm high peat soil columns under different water levels (WL). We found that soil columns require considerably higher headspace CH2F2 concentrations for complete inhibition of CH4 oxidation than small soil samples. Inhibition remained complete until ca. 24 h after CH2F2 exposure. Then, the inhibitory effect diminished. The time needed for the inhibitory effect to disappear depended on WL; at a low WL of −15 cm, the inhibitory effect declined slowly and oxidation rates recovered by 90% only after 12 days. At WL = −5 cm, CH4 oxidation recovered much faster (90% recovery after ca. 3 days). Last, CH2F2 addition significantly decreased the N2O emissions, whereas CO2 emissions remained unaltered.  相似文献   

15.
Concentrations of CH4, a potent greenhouse gas, have been increasing in the atmosphere at the rate of 1% per year. The objective of these laboratory studies was to measure the effect of different forms of inorganic N and various N-transformation inhibitors on CH4 oxidation in soil. NH 4 + oxidation was also measured in the presence of the inhibitors to determine whether they had differential activity with respect to CH4 and NH 4 + oxidation. The addition of NH4Cl at 25 g N g-1 soil strongly inhibited (78–89%) CH4 oxidation in the surface layer (0–15 cm) of a fine sandy loam and a sandy clay loam (native shortgrass prairie soils). The nitrification inhibitor nitrapyrin (5 g g-1 soil) inhibited CH4 oxidation as effectively as did NH4Cl in the fine sandy loam (82–89%), but less effectively in the sandy clay loam (52–66%). Acetylene (5 mol mol-1 in soil headspace) had a strong (76–100%) inhibitory effect on CH4 consumption in both soils. The phosphoroamide (urease inhibitor) N-(n-butyl) thiophosphoric triamide (NBPT) showed strong inhibition of CH4 consumption at 25 g g-1 soil in the fine sandy loam (83%) in the sandy clay loam (60%), but NH 4 + oxidation inhibition was weak in both soils (13–17%). The discovery that the urease inhibitor NBPT inhibits CH4 oxidation was unexpected, and the mechanism involved is unknown.  相似文献   

16.
Experimental results from a study of the gas and aqueous phase reactions of elemental mercury (Hg0) with methyl iodide (CH3I) and dimethyl sulfide (DMS) are presented. In aqueous phase experiments with CH3I we found no observable increase in methyl mercury (MeHg). A small formation of MeHg, however, was observed in some (but not all) gas phase experiments in sunlight. A loss of Hg0 and a simultaneous formation of oxidized mercury (Hg(II)) was also observed in these experiments. No reaction, neither methylation or oxidation, was found between Hg0 and DMS under any conditions investigated. These experiments suggest that a simple homogeneous gas or aqueous phase methylation of Hg0 by DMS or CH3I in the atmosphere cannot account for the significant levels of MeHg observed in precipitation.  相似文献   

17.
Rice fields are an important source for atmospheric CH4, but the effects of fertilization are not well known. We studied the turnover of CH4 in rice soil microcosms without and with addition of potassium phosphate. Height and tiller number of rice plants were higher in the fertilized than in the unfertilized microcosms. Emission rates of CH4 were also higher, but porewater concentrations of CH4 were lower. The δ13C values of the emitted CH4 and of the CH4 in the porewater were both 2-6% higher in the fertilized microcosms than in the control. Potassium phosphate did not affect rate and isotopic signature of CH4 production in anoxic soil slurries. On the other hand, roots retrieved from fertilized microcosms at the end of incubation exhibited slightly higher CH4 production rates and slightly higher CH4-δ13C values compared to roots from unfertilized plants. Addition of potassium phosphate to excised rice roots generally inhibited CH4 production and resulted in increasingly lower δ13C values of the produced CH4. Fractionation of 13C during plant ventilation (i.e. δ13C in pore water CH4 versus CH4 emitted) was larger in the fertilized microcosms than in the control. Besides plant ventilation, this difference may also have been caused by CH4 oxidation in the rhizosphere. However, calculation from the isotopic data showed that less than 27% of the produced CH4 was oxidized. Collectively, our results indicate that potassium phosphate fertilization stimulated CH4 emission by enhancing root methanogenesis, plant ventilation and/or CH4 oxidation, resulting in residence times of CH4 in the porewater in the order of hours.  相似文献   

18.
A four-year(2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier(CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4ha-1in treatments CK(zero N), U(urea) and C(CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7%(P 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration(MSA) starting on D30(30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.  相似文献   

19.
Dimethyl sulphoxide (DMSO) at 14 mM inhibits CH4 oxidation in forest soil, but the inhibition mechanism is unknown. When soil slurries are incubated in gas tight flasks, there is a lag of about 45 h before DMSO inhibits CH4 oxidation. We tried to determine if some metabolic compound derived from DMSO, as a result of microbial activity, is responsible for the inhibition. Dimethyl sulphide (DMS) accumulated in the sealed flasks up to 5-83 μl l−1 in the headspace during a 2-week period. DMS at 1 μl l−1 in the headspace (0.64 μM in soil-water slurry) had a negligible effect on CH4 oxidation but 50 μl l−1 DMS (32 μM) inhibited CH4 oxidation completely. However, the inhibition by DMSO was already evident after 45 h, when DMS concentrations were generally non-inhibiting (0.1-0.7 μl l−1). DMSO was also shown to inhibit CH4 oxidation when the DMS produced was continuously removed. Results suggest that the production of DMS from DMSO makes a minor contribution to the inhibition of CH4 oxidation by DMSO with incubation times relevant in CH4 oxidation studies.  相似文献   

20.
Summary The CH4 flux from intact soil cores of a flooded rice field in Italy was measured under aerobic and anaerobic incubation conditions. The difference between the anaerobic and aerobic CH4 fluxes was apparently due to CH4 oxidation in the oxic soil surface layer. This conclusion was supported by measurements of the vertical CH4 profile in the upper 2-cm layer, and of the V max of CH4 oxidation in slurried samples of the soil surface layer. About 80% of the CH4 was oxidized during its passage through the soil surface layer. CH4 oxidation was apparently limited by the concentration of CH4 and/or O2 in the active surface layer. The addition of ammonium to the water layer on top of the soil core reversibly increased the aerobic CH4 fluxes due to inhibition of CH4 oxidation in the soil surface layer.  相似文献   

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