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1.
由于还原剂甲烷价廉易得,甲烷选择性催化还原NO x(简称CH 4-SCR)被认为是最有潜力替代NH 3-SCR的催化还原技术。现有的CH 4-SCR催化剂中,分子筛类催化剂因催化活性高而被广泛研究,但由于其水热稳定性不好,使得非分子筛负载的催化剂成为近年来的研究热点,其中主要包括固体超强酸和氧化物两大类。综述了这两类催化体系在催化活性、反应机理及掺杂改性等方面的研究现状,比较了各种催化剂的优缺点,并对CH 4-SCR的发展前景进行了展望。 相似文献
2.
Hydrocarbon vapors associated with spilled petroleum products arouse regulatory concern and can pose a significant health and safety risk. While petroleum products do not contain a significant amount of methane (CH 4), high CH 4contents in soil gas near petroleum spills have been reported. While CH 4is nontoxic, its accumulation in shallow soil gas represents a potential explosion and asphyxiation hazard, especially in confined spaces. Identifying the source and origin of shallow CH 4accumulations is an important part of evaluating potential exposure pathways, selecting appropriate remedial measures, and determining environmental liability. This paper discusses the potential nature and anthropogenic sources for shallow CH 4and how integration of geological, geochemical, and land use data can be used to determine its origin and identify its source. Two case studies are presented, one where CH 4associated with a gasoline spill is shown to be derived from a natural source rather than the gasoline, and a second where CH 4associated with spilled crude oil is shown to be produced in the vadose zone by biodegradation of the oil. 相似文献
3.
Liquid manure storages are a significant source of methane (CH 4) emissions. Farmers commonly agitate (stir) liquid manure prior to field application to homogenize nutrients and solids. During agitation, manure undergoes mechanical stress and is exposed to the air, disrupting anaerobic conditions. This on-farm study aimed to better understand the effects of agitation on CH 4 emissions, and explore the potential for intentional agitation (three times) to disrupt the exponential increase of CH 4 emissions in spring and summer. Results showed that agitation substantially increased manure temperature in the study year compared to the previous year, particularly at upper- and mid-depths of the stored manure. The temporal pattern of CH 4 emissions was altered by reduced emissions over the subsequent week, followed by an increase during the second week. Microbial analysis indicated that the activity of archaea and methanogens increased after each agitation event, but there was little change in the populations of methanogens, archaea, and bacteria. Overall, CH 4 emissions were higher than any of the previous three years, likely due to warmer manure temperatures that were higher than the previous years (despite similar air temperatures). Therefore, intermittent manure agitation with the frequency, duration, and intensity used in this study is not recommended as a CH 4 emission mitigation practice. Implications: The potential to mitigate methane emissions from liquid manure storages by strategically timed agitation was evaluated in a detailed farm-scale study. Agitation was conducted with readily-available farm equipment, and targeted at the early summer to disrupt methanogenic communities when CH 4 emissions increase exponentially. Methane emissions were reduced for about one week after agitation. However, agitation led to increased manure temperature, and was associated with increased activity of methanogens. Overall, agitation was associated with similar or higher methane emissions. Therefore, agitation is not recommended as a mitigation strategy. 相似文献
4.
Recent experiments have shown that dry and fresh leaves, other plant matter, as well as several structural plant components, emit methane upon irradiation with UV light. Here we present the source isotope signatures of the methane emitted from a range of dry natural plant leaves and structural compounds. UV-induced methane from organic matter is strongly depleted in both 13C and D compared to the bulk biomass. The isotopic content of plant methoxyl groups, which have been identified as important precursors of aerobic methane formation in plants, falls roughly halfway between the bulk and CH 4 isotopic composition. C3 and C4/CAM plants show the well-established isotope difference in bulk 13C content. Our results show that they also emit CH 4 with different δ13C value. Furthermore, δ13C of methoxyl groups in the plant material, and ester methoxyl groups only, show a similar difference between C3 and C4/CAM plants. The correlation between the δ13C of emitted CH 4 and methoxyl groups implies that methoxyl groups are not the only source substrate of CH 4.Interestingly, δD values of the emitted CH 4 are also found to be different for C3 and C4 plants, although there is no significant difference in the bulk material. Bulk δD analyses may be compromised by a large reservoir of exchangeable hydrogen, but no significant δD difference is found either for the methoxyl groups, which do not contain exchangeable hydrogen. The δD difference in CH 4 between C3 and C4 plants indicates that at least two different reservoirs are involved in CH 4 emission. One of them is the OCH 3 group, the other one must be significantly depleted, and contribute more to the emissions of C3 plants compared to C4 plants. In qualitative agreement with this hypothesis, CH 4 emission rates are higher for C3 plants than for C4 plants. 相似文献
5.
The littoral zones of lakes have been regarded as hotspots of methane (CH 4) fluxes through several studies. In the present study, we measured CH 4 fluxes in six kinds of littoral zones of Huahu Lake on the Qinghai-Tibetan Plateau in the peak growing season of 2006 and 2007. We found that CH 4 efflux (ranging from −0.1 to 90 mg CH 4 m −2 h −1) from the littoral zones of this lake was relatively high among those of boreal and temperate lakes. Our results also showed that emergent plant zones ( Hippuris vulgaris and Glyceria maxima stands) recorded the highest CH 4 flux rate. The CH 4 flux in the floating mat zone of Carex muliensis was significantly lower than those of the emergent plant zones. CH 4 fluxes in the floating-leaved zone of Polygonum amphibium and bare lakeshore showed no significant difference and ranked last but one, only higher than that of the littoral meadow ( Kobresia tibetica). Plant biomass and standing water depths were important factors to explain such spatial variations in CH 4 fluxes. No significant temporal variations in CH 4 fluxes were found due to the insignificant variations of physical factors in the peak growing season. These results may help in our understanding of the importance of the littoral zone of lakes, especially the emergent plant zone, as a hotspot of CH 4 emission. 相似文献
6.
Landfill fugitive methane emissions were quantified as a function of climate type and cover type at 20 landfills using U.S. Environmental Protection Agency (EPA) Other Test Method (OTM)-10 vertical radial plume mapping (VRPM) with tunable diode lasers (TDLs). The VRPM data were initially collected as g CH 4/sec emission rates and subsequently converted to g CH 4/m 2/day rates using two recently published approaches. The first was based upon field tracer releases of methane or acetylene and multiple linear regression analysis (MLRM). The second was a virtual computer model that was based upon the Industrial Source Complex (ISC3) and Pasquill plume stability class models (PSCMs). Calculated emission results in g CH 4/m 2/day for each measured VRPM with the two approaches agreed well ( r 2 = 0.93). The VRPM data were obtained from the working face, temporary soil, intermediate soil, and final soil or synthetic covers. The data show that methane emissions to the atmosphere are a function of climate and cover type. Humid subtropical climates exhibited the highest emissions for all cover types at 207, 127, 102, and 32 g CH 4/m 2/day, for working face (no cover), temporary, intermediate, and final cover, respectively. Humid continental warm summers showed 67, 51, and 27 g CH 4/m 2/day for temporary, intermediate, and final covers. Humid continental cool summers were 135, 40, and 26 g CH 4/m 2/day for the working face, intermediate, and final covers. Mediterranean climates were examined for intermediate and final covers only and found to be 11 and 6 g CH 4/m 2/day, respectively, whereas semiarid climates showed 85, 11, 3.7, and 2.7 g CH 4/m 2/day for working face, temporary, intermediate, and final covers. A closed, synthetically capped landfill covered with soil and vegetation with a gas collection system in a humid continental warm summer climate gave mostly background methane readings and average emission rates of only 0.09 g CH 4/m 2/day flux when measurable. Implications The OTM-10 method is being proposed by EPA to quantify surface methane emissions from landfill covers. This study of 20 landfills across the United States was done to determine the efficacy of using OTM-10 for this purpose. Two recently published models were used to evaluate the methane flux results found with VRPM optical remote sensing. The results should provide a sense of the practicality of the method, its limitations at landfills, and the impact of climate upon the cover's methane flux. Measured field data may assist landfill owners in refining previously modeled methane emission factor default values. 相似文献
7.
Novel aerial methane (CH 4) detection technologies were used in this study to identify anomalously high-emitting oil and gas (O&G) facilities and to guide ground-based “leak detection and repair” (LDAR) teams. This approach has the potential to enable a rapid and effective inspection of O&G facilities under voluntary or regulatory LDAR programs to identify and mitigate anomalously large CH 4 emissions from a disproportionately small number of facilities. This is the first study of which the authors are aware to deploy, evaluate, and compare the CH 4 detection volumes and cost-effectiveness of aerially guided and purely ground-based LDAR techniques. Two aerial methods, the Kairos Aerospace infrared CH 4 column imaging and the Scientific Aviation in situ aircraft CH 4 mole fraction measurements, were tested during a 2-week period in the Fayetteville Shale region contemporaneously with conventional ground-based LDAR. We show that aerially guided LDAR can be at least as cost-effective as ground-based LDAR, but several variable parameters were identified that strongly affect cost-effectiveness and which require field research and improvements beyond this pilot study. These parameters include (i) CH 4 minimum dectectable limit of aerial technologies, (ii) emission rate size distributions of sources, (iii) remote distinction of fixable versus nonfixable CH 4 sources (“leaks” vs. CH 4 emissions occurring by design), and (iv) the fraction of fixable sources to total CH 4 emissions. Suggestions for future study design are provided. Implications: Mitigation of methane leaks from existing oil and gas operations currently relies on on-site inspections of all applicable facilities at a prescribed frequency. This approach is labor- and cost-intensive, especially because a majority of oil and gas–related methane emissions originate from a disproportionately small number of facilities and components. We show for the first time in real-world conditions how aerial methane measurements can identify anomalously high-emitting facilities to enable a rapid, focused, and directed ground inspection of these facilities. The aerially guided approach can be more cost-effective than current practices, especially when implementing the aircraft deployment improvements discussed here. 相似文献
8.
Knowing the fraction of methane (CH 4) oxidized in landfill cover soils is an important step in estimating the total CH 4 emissions from any landfill. Predicting CH 4 oxidation in landfill cover soils is a difficult task because it is controlled by a number of biological and environmental factors. This study proposes an artificial neural network (ANN) approach using feedforward backpropagation to predict CH 4 oxidation in landfill cover soil in relation to air temperature, soil moisture content, oxygen (O 2) concentration at a depth of 10 cm in cover soil, and CH 4 concentration at the bottom of cover soil. The optimum ANN model giving the lowest mean square error (MSE) was configured from three layers, with 12 and 9 neurons at the first and the second hidden layers, respectively, log-sigmoid (logsig) transfer function at the hidden and output layers, and the Levenberg-Marquardt training algorithm. This study revealed that the ANN oxidation model can predict CH 4 oxidation with a MSE of 0.0082, a coefficient of determination ( R 2) between the measured and predicted outputs of up to 0.937, and a model efficiency ( E) of 0.8978. To conclude, further developments of the proposed ANN model are required to generalize and apply the model to other landfills with different cover soil properties. Implications: To date, no attempts have been made to predict the percent of CH4 oxidation within landfill cover soils using an ANN. This paper presents modeling of CH4 oxidation in landfill cover soil using ANN based on field measurements data under tropical climate conditions in Malaysia. The proposed ANN oxidation model can be used to predict the percentage of CH4 oxidation from other landfills with similar climate conditions, cover soil texture, and other properties. The predicted value of CH4 oxidation can be used in conjunction with the Intergovernmental Panel on Climate Change (IPCC) First Order Decay (FOD) model by landfill operators to accurately estimate total CH4 emission and how much it contributes to global warming. 相似文献
9.
Methane biofiltration (MBF) is a novel low-cost technique for reducing low volume point source emissions of methane (CH 4). MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting CH 4 to carbon dioxide (CO 2) and water (H 2O). A field research program was undertaken to evaluate the potential to treat low volume point source engineered CH 4 emissions using an MBF at a natural gas monitoring station. A new comprehensive three-dimensional numerical model was developed incorporating advection-diffusive flow of gas, biological reactions and heat and moisture flow. The one-dimensional version of this model was used as a guiding tool for designing and operating the MBF. The long-term monitoring results of the field MBF are also presented. The field MBF operated with no control of precipitation, evaporation, and temperature, provided more than 80% of CH 4 oxidation throughout spring, summer, and fall seasons. The numerical model was able to predict the CH 4 oxidation behavior of the field MBF with high accuracy. The numerical model simulations are presented for estimating CH 4 oxidation efficiencies under various operating conditions, including different filter bed depths and CH 4 flux rates. The field observations as well as numerical model simulations indicated that the long-term performance of MBFs is strongly dependent on environmental factors, such as ambient temperature and precipitation. 相似文献
10.
在优势菌生物除铬系统中悬挂表面磁场分别为0~6 mT和0~20 mT的磁片,分别控制磁片之间的磁场强度介于0~4.5 mT和0~14 mT,以未加磁场的对照系统作为参照,考察试验污泥活性的变化.试验结果表明,反应器中磁场强度为0~4.5 mT时,对厌氧活性污泥活性的促进效果较好,最大产甲烷速率(Umax.CH4)达64.3 mL CH4/g VSS·d,比非磁场系统提高20.6%,消耗单位COD产甲烷量为0.140 mL CH4/mg COD,比系统非磁场系统提高70.7%.同时发现了磁场的引入,提高了试验污泥利用COD物质生成甲烷的效率,对于低有机负荷重金属废水的生物净化尤其意义重大. 相似文献
11.
We have constructed a record of atmospheric methane (CH 4) over the last 10,000 γ which shows that CH 4 has increased to more than double the natural levels of a century ago. This record is based on systematic global measurements taken since 1975, the occasional measurements taken by various scientists between 1962 and 1981, and the record of CH 4 in bubbles of air trapped in polar ice. Our observations and calculations show that the concentrations of CH 4 remained virtually unchanged over thousands of years until about a few hundred years ago. Until the beginning of the 18th century there is no evidence of significant trends. Between 1700 and 1900 CH 4 increased slowly at an average rate of about 1.5 ppbvy −1, between 1900 and 1925 CH 4 increased by about 2.2 ppbvy −1, between 1927 and 1956 by 6.4 ppby y −1, between 1962 and 1973 by about 11 ppbvy −1 and during the last decade it has increased at a rate of about 17 ppbvy −1. We explain these rates of increase by a global mass balance model. In the model, the increase of emissions from sources affected by human activities is taken to be proportional to the population and the atmospheric lifetime of CH 4 is taken to be increasing if human activities are slowly depleting OH radicals that remove CH 4 from the atmosphere. 相似文献
12.
ABSTRACT The increase in solid waste generation has been a major contributor to the amount of Greenhouse gases (GHGs) present in the atmosphere. To some extent, a great chunk of these GHGs in the atmosphere is from landfill. This study assesses two theoretical models (LandGEM and Afvalzorg models) to estimate the amount of landfill gas (LFG) emitted from Thohoyandou landfill site. Also, the LFGcost Web model was used to estimate the cost and benefits of the implementation of an LFG utilization technology. The Thohoyandou landfill started operations in the year 2005 and it is proposed to reach its peak at approximately in the year 2026. The LandGEM calculates the mass of landfill gas emission using methane generation capacity, mass of deposited waste, methane generation constant and methane generation rate. Meanwhile, the Afvalzorg model determines the LFG emissions using the Methane correction factor, yearly waste mass disposal, waste composition, Degradation Organic Carbon, methane generation rate constant, LFG recovery efficiency. The study findings indicate that the methane (CH 4) and carbon dioxide (CO 2) emitted from the landfill estimated from LandGEM will peak in the year 2026 with values of 3517 Mg/year and 9649 Mg/year, respectively. Results from the Afvalzorg model show that CH 4 emission will peak in the year 2026 (3336 Mg/year). The LandGEM model showed that the total LFG, CH 4 and CO 2 emitted from the landfill between 2005 and 2040 are 293239.3 Mg/year, 78325.7 Mg/year and 214908.6 Mg/year, respectively. The simulation from the Afvalzorg model found that the CH 4 emitted from the years 2005– 2040 is 74302 Mg/year. The implementation of an LFG utilization technology was economically feasible from consideration of the sales of electricity generated and Certified Emission Reductions (CER) (carbon credits). 相似文献
13.
Methane (CH 4) is the dominant greenhouse gas emitted by animal agriculture manure. Since the gas is relatively insoluble in water, it is concentrated in discrete bubbles that rise through waste lagoons and burst at the surface. This results in lagoon emissions that are inhomogeneous in both space and time. Emissions from a midwestern dairy waste lagoon were measured over 2 weeks to evaluate the spatial homogeneity of the source emissions and to compare two methods for measuring this inhomogeneous emission. Emissions were determined using an inverse dispersion model based on CH 4 concentrations measured both by a single scanning tunable diode laser (TDL) aimed at a series of reflectors and by flame ionization detection (FID) gas chromatography on line-sampled air. Emissions were best estimated using scanned TDL concentrations over relatively short optical paths that collectively span the entire cross-wind width of the source, so as to provide both the best capture of discrete plumes from the bursting bubbles on the lagoon surface and the best detection of CH 4 background concentrations. The lagoon emissions during the study were spatially inhomogeneous at hourly time scales. Partitioning the inhomogeneous source into two source regions reduced the estimated emissions of the overall lagoon by 57% but increased the variability. Consequently, it is important to assess the homogeneity of a source prior to measurements and final emissions calculation.Implications: Plans for measuring methane emissions from waste lagoons must take into account the spatial inhomogeneity of the source strength. The assumption of emission source homogeneity for a low-solubility gas such as CH4 emitted from an animal waste lagoon can result in significant emission overestimates. The entire breadth and length of the area source must be measured, preferably with multiple optical paths, for the detection of discrete plumes from the different emitting regions and for determining the background concentration. Other gases with similarly poor solubility in water may also require partitioning of the lagoon source area. 相似文献
14.
We have recently completed a methane emissions inventory for the New England region. Methane emissions were calculated to be 0.91 Tg yr -1, with wetlands and landfills dominating all other sources. Wetlands are estimated to produce 0.33 Tg CH 4 yr -1, of which 74% come from Maine. Active landfills emit an estimated 0.28 Tg CH 4 yr -1, 60% of which are generated from twelve landfills. Although uncertainty in the estimate is greater, emissions from closed landfills are on the same order of magnitude as active landfills and wetlands; 0.25 Tg CH 4 yr -1. Sources of moderate magnitude include ruminant animals (0.05 Tg CH 4 yr -1) and residential wood combustion (0.03 Tg CH 4 yr -1). Motor vehicles, natural gas, and wastewater treatment make only minor contributions. New England is heavily forested and the soil uptake of atmospheric methane in upland forests, 0.06 Tg CH 4 yr -1, decreases emissions from soils by about 18%. Although uncertainties remain, our estimates indicate that even in a highly urbanized region such as New England, natural sources of methane make the single greatest contribution to total emissions, with state totals varying between 8% (Massachusetts) and 92% (Maine). Because emissions from only a few large landfills dominate anthropogenic sources, mitigation strategies focused on these discrete point sources should result in significant improvements in regional air quality. Current federal regulations mandate landfill gas collection at only the largest sites. Expanding recovery efforts to moderately sized landfills through either voluntary compliance or further regulations offers the best opportunity to substantially reduce atmospheric methane in New England. In the short term, however, the large contribution from closed, poorly regulated landfills may make the attribution of air quality improvements difficult. Mitigation efforts toward these landfills should also be a priority. 相似文献
15.
ABSTRACT Oil and natural gas wells are a prominent source of the greenhouse gas methane (CH 4), but most measurements are from newer, high producing wells. There are nearly 700,000 marginal “stripper” wells in the US, which produce less than 15 barrels of oil equivalent (BOE) d ?1. We made direct measurements of CH 4 and volatile organic carbon (VOC) emissions from marginal oil and gas wells in the Appalachian Basin of southeastern Ohio, all producing < 1 BOE d ?1. Methane and VOC emissions followed a skewed distribution, with many wells having zero or low emissions and a few wells responsible for the majority of emissions. The average CH 4 emission rate from marginal wells was 128 g h ?1 (median: 18 g h ?1; range: 0– 907 g h ?1). Follow-up measurements at five wells indicated high emissions were not episodic. Some wells were emitting all or more of the reported gas produced at each well, or venting gas from wells with no reported gas production. Measurements were made from wellheads only, not tanks, so our estimates may be conservative. Stochastic processes such as maintenance may be the main driver of emissions. Marginal wells are a disproportionate source of CH 4 and VOCs relative to oil and gas production. We estimate that oil and gas wells in this lowest production category emit approximately 11% of total annual CH 4 from oil and gas production in the EPA greenhouse gas inventory, although they produce about 0.2% of oil and 0.4% of gas in the US per year. Implications: Low producing marginal wells are the most abundant type of oil and gas well in the United States, and a surprising number of them are venting all or more of their reported produced gas to the atmosphere. This makes marginal wells a disproportionate greenhouse gas emissions source compared to their energy return, and a good target for environmental mitigation. 相似文献
16.
Landfills are among the major sources of anthropogenic methane (CH 4) estimated to reach 40?×?10 9kg per year worldwide by 2015 ( IPCC, 2007 IPCC. 2007. Intergovernmental Panel on Climate Change, Synthesis Report on Contributions of Work Groups 1, 2, and 3 to the Fourth Assessment Report Core Writing Team, Edited by: Pauchar, R.K. and Reisinger, A. Geneva, Switzerland: IPCC. [Google Scholar]). A 2½-year field experiment was conducted at a closed landfill in western Michigan where methanotrophs, methane-consuming bacteria, were stimulated by nutrient addition to the soil without significantly increasing biogenic nitrous oxide (N 2O) production. The effects of the nitrogen amendments (KNO 3 and NH 4Cl), phenylacetylene (a selective inhibitor of nitrifying bacteria that contribute to N 2O production), and a canopy (to reduce direct water infiltration) on the vertical soil gas profiles of CH 4, CO 2, and O 2 were measured in the top meter of the soil. Methane and nitrous oxide fluxes were calculated from the corresponding soil gas concentration gradients with respect to depth and a Millington–Quirk diffusivity coefficient in soil derived empirically from soil porosity, water content, and diffusivity coefficients in air from the literature. Methane flux estimates were as high as 218.4 g m ?2 day ?1 in the fall and 12.8 g/m ?2 day ?1 in the summer. During the spring and summer, CH 4 fluxes were reduced by more than half by adding KNO 3 and NH 4Cl into the soil as compared to control plots, while N 2O fluxes increased substantially. The concurrent addition of phenylacetylene to the amendment decreased peak N 2O production by half and the rate of peak methane oxidation by about one-third. The seasonal average methane and N 2O flux data were extrapolated to estimate the reduction of CH 4 and N 2O fluxes into the atmosphere by nitrogen and inhibitor addition to the cover soils. The results suggest that such additions coupled with soil moisture management may provide a potential strategy to significantly reduce greenhouse gas emissions from landfills. Implications The results of a 2½-year study of effects of nutrient stimulation on methane oxidation in landfill cover soils demonstrates that nutrient addition does decrease methane emissions. The work further underscores the control which soil moisture exerts on methane oxidation. Water management is critical to the success of methane oxidation strategies. 相似文献
17.
ABSTRACT In this paper, methane emissions from municipal wastewater treatment plants and municipal solid waste (MSW) landfills in Jordan for 1994 have been estimated using the methodology developed by the Intergovernmental Panel on Climate Change (IPCC). For this purpose, the 14 domestic wastewater treatment plants in the country were surveyed. Generation rates and characterization of MSW components as well as dumping and landfilling practices were surveyed in order to estimate 1994 CH 4 emissions from these sites. Locally available waste statistics were used in cases where those of the IPCC guidelines were not representative of Jordan's statistics. Methane emissions from domestic wastewater in Jordan were estimated at 4.66 gigagrams (Gg). Total 1994 CH 4 emissions from MSW management facilities in Jordan are estimated at 371.76 Gg—351.12 Gg (94.45%) from sanitary landfills, 19.83 Gg (5.33%) from MSW open dumps, and 0.81 Gg (0.22%) from raw sewage-water dumping ponds. Uncertainties associated with these estimations are presented. 相似文献
18.
To investigate the impacts of major factors on carbon loss via gaseous emissions, carbon dioxide (CO 2) and methane (CH 4) emissions from the ground of open dairy lots were tested by a scale model experiment at various air temperatures (15, 25, and 35 °C), surface velocities (0.4, 0.7, 1.0, and 1.2 m sec ?1), and floor types (unpaved soil floor and brick-paved floor) in controlled laboratory conditions using the wind tunnel method. Generally, CO 2 and CH 4 emissions were significantly enhanced with the increase of air temperature and velocity ( P < 0.05). Floor type had different effects on the CO 2 and CH 4 emissions, which were also affected by air temperature and soil characteristics of the floor. Although different patterns were observed on CH 4 emission from the soil and brick floors at different air temperature-velocity combinations, statistical analysis showed no significant difference in CH 4 emissions from different floors ( P > 0.05). For CO 2, similar emissions were found from the soil and brick floors at 15 and 25 °C, whereas higher rates were detected from the brick floor at 35 °C ( P < 0.05). Results showed that CH 4 emission from the scale model was exponentially related to CO 2 flux, which might be helpful in CH 4 emission estimation from manure management. Implications: Gaseous emissions from the open lots are largely dependent on outdoor climate, floor systems, and management practices, which are quite different from those indoors. This study assessed the effects of floor types and air velocities on CO 2 and CH 4 emissions from the open dairy lots at various temperatures by a wind tunnel. It provided some valuable information for decision-making and further studies on gaseous emissions from open lots. 相似文献
19.
The spatial and temporal behavior of atmospheric methane (CH 4) in the Nagoya metropolitan area was investigated in relation to the regional meteorological and topographical characteristics. It was found that the daily maximum CH 4 concentrations in the central city area were observed when the northeast wind blew from the foothill of the northeastern mountainous area down into the central city areas, under stable atmospheric conditions. The large and active landfills are the major anthropogenic CH 4 sources and are located at the hill sites in the northeast. Therefore, it was considered that the air mass with the high concentration of CH 4 flowed from the landfill sites into the urban area, and exerted substantial influences on the spatial and temporal variations of atmospheric CH 4 concentrations in the central city area. 相似文献
20.
Ammonia, nitrous oxide, and methane emission from animal farming of South, Southeast, and East Asia, in 2000, was estimated at about 4.7 Tg NH 3–N, 0.51 Tg N 2O–N, and 29.9 Tg CH 4, respectively, using the FAO database and countries’ statistic databases as activity data, and emission factors taking account of regional characteristics. Most of these atmospheric components, up to 60–80%, were produced in China and India. Pakistan, Bangladesh, and Indonesia, which were large source countries next to China and India, contributed more than a few percent of total emission of each atmospheric component. The largest emission livestock were cattle whose contribution was considerably high in South, Southeast, and East Asia; more than one-fourth of ammonia and nitrous oxide emissions: more than half of methane emission. The other major livestock for nitrous oxide and ammonia emissions were pigs. For methane emission, buffaloes were second source livestock. To provide spatial distributions of these gases, the emissions of county and district level were allocated into each 0.5° grid by means of the weighting by high-resolution land cover datasets. The regions with considerable high emissions of all components were able to be found at the Ganges delta and the Yellow River basin. The spatial distributions for ammonia and nitrous oxide emissions were similar but had a substantial difference from methane distribution. 相似文献
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