Carbon Dioxide, Methane, and Nitrous Oxide Emissions from a Rice-Wheat Rotation as Affected by Crop Residue Incorporation and Temperature

Field measurements were made from June 2001 to May 2002 to evaluate the e?ect of crop residue application and temperature on CO2, CH4, and N2O emissions within an entire rice-wheat rotation season. Rapeseed cake and wheat straw were incorporated into the soil at a rate of 2.25 t hm?2 when the rice crop was transplanted in June 2001. Compared with the control, the incorporation of rapeseed cake enhanced the emissions of CO2, CH4, and N2O in the rice-growing season by 12.3%, 252.3%, and 17.5%, respectively, while no further e?ect was held on the emissions of CO2 and N2O in the following wheat- growing season. The incorporation of wheat straw enhanced the emissions of CO2 and CH4 by 7.1% and 249.6%, respectively, but reduced the N2O emission by 18.8% in the rice-growing season. Signi?cant reductions of 17.8% for the CO2 and of 12.9% for the N2O emission were observed in the following wheat- growing season. A positive correlation existed between the emissions of N2O and CO2 (R2 = 0.445,n = 73,p < 0.001) from the rice-growing season when N2O was emitted. A trade-o? relationship between the emissions of CH4 and N2O was found in the rice-growing season. The CH4 emission was signi?cantly correlated with the CO2 emission for the period from rice transplantation to ?eld drainage, but not for the entire rice-growing season. In addition, air temperature was found to regulate the CO2 emissions from the non-waterlogged period over the entire rice-wheat rotation season and the N2O emissions from the non- waterlogged period of the rice-growing season, which can be quantitatively described by an exponential function. The temperature coe?cient (Q10) was then evaluated to be 2.3±0.2 for the CO2 emission and 3.9±0.4 for the N2O emission, respectively.

Methane emissions from natural and drained peatlands in the Zoigê, eastern Qinghai-Tibet Plateau

Peatlands are one of the major natural sources of methane （CH4）, but the level of CH4 efflux is uncertain, especially in alpine peatlands. In this study, CH4 emission fluxes from natural and drained peatlands on the Qinghai- Tibet Plateau, southwest China, were measured from June to October in 2013 using the opaque static chamber technique and the Fast Greenhouse Gas Analyzer （DLT-100, Los Gatos Research Corp.）. CH4 emission fluxes ranged from 2.07 to 56.33 mg m^-2 h^-1 in natural peatlands and from 0.02 to 0.42 mg m^-2 h^-1 in drained peatlands. Mean CH4 emission flux was 19.13 mg m^-2 h^-1 in natural peatlands and 0.14 mg m^-2 h^-1 in drained peatlands. These results showed that drainage led to a significant decrease in CH4 emissions. CH4 emission fluxes for all sampling plots were significantly correlated with variation in water table depth for linear （R^2 = 0.453, P 〈 0.01） and exponential functions （R^2 = 0.429, P 〈 0.01）.

Estimation of Methane Emissions from Municipal Solid Waste Landfills in China Based on Point Emission Sources

The methane(CH4) emissions from municipal solid waste(MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD(firstorder decay) model. The location, capacity and age of landfills constitute the three dimensions of the emission factors matrix, which were obtained by laboratory analysis and in situ investigation. Key parameters such as waste composition,degradable organic carbon ratio, CH4 correction factor, oxidation factor and recovery rate, were carefully analyzed in terms of these three dimensions. The point sources database consists of 2,107 MSW landfills in cities and towns of China in 2007. The results show that the CH4 emissions from MSW landfills were 1.186 Mt in 2007. Compared with the CH4 emissions of 2.20 Mt in 2005, the significant discrepancy mainly comes from statistical data of landfills, e.g., number of landfills and amount of waste disposed in landfills. CH4 emissions were lower than 700 t for most of the landfills, whereas there were 279 landfills with emissions larger than 1,000 t, and only 10 landfills with emissions larger than 10,000 t.Jiangsu province ranks the largest emitter with 98,700 t while Tibet is the smallest emitter with 2,100 t. In general,the emissions from eastern provinces, such as Jiangsu, Guangdong and Zhejiang, were larger than those from western provinces, such as Ningxia, Tibet and Qinghai.

ESTIMATE OF METHANE EMISSIONS FROM RICE FIELDS IN CHINA BY CLIMATE-BASED NET PRIMARY PRODUCTIVITY

Rice fields provide food for over half of the world population but are also an important source of atmospheric CH4. Using the climate-based GIS empirical model and the meteorological data collected from 600 meteorological stations in China, with county as the basic unit, the net primary productivity (NPP) of rice fields in China in 1990, 1995, 1998, and 2000 were estimated to be in the range from 202.19×1012g C in 1990 to 163.46×1012g C in 2000. From the measured data of the factors affecting CH4 emission and NPP, the conversion ratio of the NPP into CH4 emission for the rice fields of China was determined to be 1.8%. Using this ratio and estimated NPP, the CH4 emissions from rice fields of China in 1990, 1995, 1998, and 2000 were estimated to be 7.24×1012, 6.31×1012, 6.77×1012 and 5.85×1012g CH4, respectively.

Modeling Methane Emissions from Paddy Rice Fields under Elevated Atmospheric Carbon Dioxide Conditions

Abstract Methane （CH4） emissions from paddy rice fields substantially contribute to the dramatic increase of this greenhouse gas in the atmosphere. Due to great concern about climate change, it is necessary to predict the effects of the dramatic increase in atmospheric carbon dioxide （CO2） on CH4 emissions from paddy rice fields. CH4MOD 1.0 is the most widely validated model for simulating CH4 emissions from paddy rice fields exposed to ambient CO2 （hereinafter referred to as aCO2）. We upgraded the model to CH4MOD 2.0 by： （a） modifying the description of the influences of soil Eh and the water regime on CH4 production; （b） adding new features to reflect the regulatory effects of atmospheric CO2 upon methanogenic substrates, soil Eh during drainages, and vascular CH4 transport; and （c） adding a new feature to simulate the influences of nitrogen （N） addition rates on methanogenic substrates under elevated CO2 （hereinafter referred to as eCO2） condition. Validation with 109 observation cases under aC02 condition showed that CHaMOD 2.0 possessed a minor systematic bias in the prediction of seasonally accumulated methane emissions （SAM）. Validation with observations in free-air CO2 enrichment （FACE） experiments in temperate and subtropical climates showed that CH4MOD 2.0 successfully simulated the effects of eCO2 upon SAM from paddy rice fields incorporated with various levels of previous crop residues and/or N fertilizer. Our results imply that CH4MOD 2.0 provides a potential approach for estimating of the effects of elevated atmospheric CO2 upon CHa emissions from regional or global paddy rice fields with various management practices in a changing climate.

STUDY ON FLUXES OF CH4 EMISSION FROM PADDY FIELDS IN CHANGCHUN AREA

Little has been done in measurement and research of the flux of CH4 emission from paddy fields in Changchun area, Jilin Province, China before 1994. So the purpose of the study is to offer available regional data of CH4 emission flux and to discuss the factors which affect CH4 emission from paddy fields. Experimental paddy fields are chosen using TM pictures respectively in Xinlicheng (43° 49′ N, 125° 20′ E) of the Yitong River’s and in Wanchang (43° 44′ 10″ N, 125° 53′ 11″ E) of the Yinma River’s alluvial plain. The fluxes of CH4 emission from paddy fields are measured by the method of static chamber in Changchun area in 3 consecutive years. The research results show that the peak of CH4 emission from paddy fields occurs during the booting stage. The mean fluxes of CH4 emission are 7.056 mg/(m2· h) and 0.489 mg/(m2· h) in the paddy fields of flood and discontinuous irrigation respectively. The contrastive study holds that climate condition, the way of water management and fertilizer variation have significant influence on fluxes of CH4 emission from paddy fields. The difference of climatic conditions causes the interannual change of the flux of CH4 emission from paddy fields. In general, the flux of CH4 emission from paddy fields of flood irrigation is greater than that from paddy fields of discontinuous irrigation. To change the way of water management perhaps is an available way to reduce CH4 emission flux from paddy fields.

Short-term effects of fire disturbance on CH4 emission from forested wetlands in the Xiaoxing’an Mountains, Northeast China

Using static chamber gas chromatography, we determined the seasonal dynamics, controlling factors, and distribution patterns of forest swamp CH4 levels and related environmental factors (temperature, water level) after fire disturbance in the Xiaoxing’an Mountains. The results showed the following: during the growing season, the annual CH4 emission distribution ranged from - 0.001 ± 0.012 to 22.373 ± 3.650 mg m^-2 h^-1;mild fire caused the swamp CH4 emission flux of tussock, shrub, Alnus sibirica and birch swamp to increase by 56.0–524.7%;at low water levels, temperature had a significant influence on the swamp type, and the correlation between the methane emission flux and temperature was significantly strengthened;after a fire disturbance, methane emissions from all types of marsh were highest in summer and second highest in autumn, with a weak absorption in spring;and along the water environment gradient of the transition zone, the CH4 emission flux presented a decreasing trend in its spatial distribution pattern.

Recovering methane from quartz sand-bearing hydrate with gaseous CO2

The replacement method by CO;is regarded as a new approach to natural gas hydrate（NGH） exploitation method, by which methane production and carbon dioxide sequestration might be obtained simultaneously. In this study, CO;was used to recover CH;from hydrate reservoirs at different temperatures and pressures. During the CO;–CH;recovery process, the pressure was selected from 2.1 to 3.4 MPa, and the temperature ranged from 274.2 to 281.2 K. Calculating the fugacity differences between the gas phase and the hydrate phase for CO;and CH;at different conditions, it has found rising pressure was positive for hydrates formation process that was helpful for the improvement of CH;recovery rate. Rising temperature promoted the trend of CH;hydrate decomposition for the whole process of CO;–CH;replacement.The highest recovery rate was 46.6 % at 3.4 MPa 281.2 K for CO;–CH;replacement reaction in this work.

Super Rice Cropping Will Enhance Rice Yield and Reduce CH_4 Emission:A Case Study in Nanjing,China

A pot experiment was performed to learn the differences in plant productivity and OH4 emission between two rice cultivars, super rice variety Ningjing 1 and traditional variety Zhendao 11, which were currently commercially appUed in Nanjing, China. Similar seasonal changes of CH4 emission fluxes and soil solution CH4 contents were found between the tested cultivars. Although there was no significant difference in plant biomass production between the cultivars, the grain yield of Ningjing 1 was significantly higher by 35.0% （P 〈 0.05） than that of Zhendao 11, whereas the total CH4 emission from Ningjing 1 was 35.2% lower （P 〈 0.05）. The main difference in the amounts of CH4 emission between the cultivars occurred in the period from the tillering stage to the heading stage. The biomass-scaled and yield-scaled CH4 emissions were respectively 3.8 and 5.2 mg/g for Ningjing 1, significantly lower than those for Zhendao 11 （7.4 and 12.8 mg/g, respectively）. According to the relationships between the plant growth characteristics and the CH4 emission, a stronger root system contributed mainly to the lower CH4 emission of Ningjing 1, as compared with Zhendao 11. Our results demonstrated that super rice has advantages not only in grain productivity but also in CH4 emission mitigation. Further expansion of super rice cropping will enhance rice yield and reduce greenhouse gas emission in China.

Methane dehydroaromatization with periodic CH_4-H_2 switch:A promising process for aromatics and hydrogen

Long-term stability test of Mo/HZSM-5-N catalysts（HZSM-5-N stands for nano-sized HZSM-5） in methane dehydroaromatization（MDA）reaction has been performed with periodic CH4-H2 switch at 1033-1073 K for more than 1000 h.During this test,methane conversion ranges from 13% to 16%,and mean yield to aromatics（i.e.benzene and naphthalene） exceeds 10%.N2-physisorption,XRD,NMR and TPO measurements were performed for the used Mo/HZSM-5 catalysts and coke deposition,and the results revealed that the periodic hydrogenation can effectively suppress coke deposition by removing the inert aromatic-type coke,thus ensuring Mo/HZSM-5 partly maintained its activity even in the presence of large amount of coke deposition.The effect of zeolite particle size on the catalytic activity was also explored,and the results showed that the nano-sized zeolite with low diffusion resistance performed better.It is recognized that the size effect was enhanced by reaction time,and it became more remarkable in a long-term MDA reaction even at a low space velocity.

Simulation of a NGCC Power Generation Plant for the Production of Electricity from CO₂Emissions Part I: The Methanation Reactor

The final goal of this applied research is to simulate a Natural Gas Combined Cycle (NGCC) power plant with a CO2 capture unit. The originality of this investigation is the integration of a methanation process to produce the natural gas of the power plant from the captured CO2. The objective of this first part of the investigation is to simulate a methanation reactor for the production of methane using 1 kg/hr. of captured carbon dioxide containing 95% mol. CO2 and 5% mol. H2O. To reach this goal, Aspen Plus software and the Redlich-Kwong-Soave equation of state with modified Huron-Vidal mixing rules are utilized. Three parameters are considered in order to maximize the production of CH4 production: 1) temperature, varying from 250°C to 300°C, 2) pressure varying between 10 atm to 40 atm and 3) [H2/CO2] ratio which varies between 2 to 6. The maximum production of methane of 0.875 kmol/hr. was obtained for the following operating conditions: [H2/CO2] ratio of 3.5, at relatively low temperature (250°C - 270°C) and high pressures 30 and 40 atm.

The Spatial and Temporal Variation Characteristics of CH₄and CO₂Emission Flux under Different Land Use Types in the Yellow River Delta Wetland

The Yellow River Delta Wetland is one of the youngest wetlands, and also the most complete, extensive wetlands in China. The wetland in this delta is ecologically important due to their hydrologic attributes and their roles as ecotones between terrestrial and aquatic ecosystems. In the study, the spatial and temporal variation characteristics of CH4 and CO2 emission flux under five kinds of land use types in the wetland were investigated. The results indicated that the greenhouse gas emission flux, especially the CO2 and CH4, showed distinctly spatial and temporal variation under different land use types in the wetland. In the spring, the emission flux of CO2 was higher than that of CO2 in the autumn, and appeared negative in HW3 and HW4 in the autumn. CH4 emission flux of HW4 and HW5 was negative in the spring and autumn, which indicated that the CH4 emission process was net absorption. Among the five kinds of land use types, the CO2 emission flux of HW4 discharged the largest emission flux reaching 29.3 mg.m-2.h-1, but the CH4 emission flux of HW2 discharged the largest emission flux reaching 0.15 mg.m-2.h-1. From the estuary to the inland, the emission flux of CO2 was decreased at first and then appeared increasing trend, but the emission flux of CH4 was contrary to CO2.

Methane Adsorption on Montmorillonite, Kaolinite and Illite at High Pressures

Shale gas, which is derived from organic matters in shale and stored in shale deposits, is an important unconventional gas resource and attracts attention due to its significant requirement in the hydrocarbon production. Methane (CH4) is the dominant component of shale gas, and adsorbed gas is an important reservoir form. Many studies have investigated the adsorption capacities and adsorption mechanisms of CH4 in shale. Organic matters and clay minerals have been proposed to be the two major components for CH4 adsorption. Adsorption of CH4 in organic matters, such as the adsorption capacity and effects of characteristics of the organic matters, has been well investigated. However, studies on CH4 adsorption on clay minerals have mainly focused on evaluating the adsorption capacity, and very little information about the adsorption mechanism has been provided. For example, the adsorption sites and factors influencing CH4 adsorption on clay minerals remain unclear. Three main reasons account for this: (1) the co-existence of organic matters in samples affects the evaluation of CH4 adsorption on clay minerals; (2) the pressures used during adsorption are not representative of actual reservoir pressures; and (3) the clay minerals selected have low swelling capacity and a smaller interlayer distances than a CH4 size, resulting in the misunderstanding of the CH4 adsorption sites.

Carbon and Hydrogen Isotopes as Tracers of Methane Dynamic in Wetlands

This work presents a review of the main processes leading to the production and sinking of methane in wetlands and how they affect the stable isotope composition of carbon and hydrogen. Isotope fractionation factors associated to diffusion, ebullition, bacterial oxidation, etc., have been gathered from relevant literature in an intent of providing researchers in this thematic with practical procedures and tools for the interpretation of experimental data. Also it is presented guidelines of the most reliable field and laboratory methods used at present for the correct sampling and analyzing methane in different stages of occurrence, as well the most common tools used in their interpretation. Each statement is fully referenced to a long updated list of publications.

全球甲烷控排政策措施评述及其对中国的启示和建议

相比CO_(2),甲烷(CH_(4))寿命短、全球增温潜势高,同时也是地面臭氧污染的关键成分,对其排放进行管控对减缓气候变化和改善大气污染具有重要意义。目前全球人为CH_(4)排放处在上升阶段,其中畜牧业和油气领域是关键排放源。人为源与自然源或已形成正向反馈。就国别排放而言,《联合国气候变化框架公约》附件一缔约方的CH_(4)排放呈现下降趋势,非附件一国家面临挑战。各国主要采用规制类政策措施(例如标准)管控CH_(4)排放,市场手段为辅,同时自愿协议、伙伴关系也是非常重要的成本有效措施。中国通过多措并举在CH_(4)管控方面取得了一定成效,体现为总体排放增速较低,部分环节排放出现下降。未来中国CH_(4)管控面临多重挑战,包括成本高、难以避免结构性排放上升、基础支持体系比较薄弱。基于以上现状和挑战,文中提出针对性政策建议。

华东稻田CH_4和N_2O排放

稻田ＣＨ４和Ｎ２Ｏ排放的季节变化规律完全不同，两者的排放通量随土壤水分条件变化而互为消长，但它们的日变化形式则比较一致。晴天时的ＣＨ４和Ｎ２Ｏ排放日变化规律明显，主要表现为下午单峰模态，有时ＣＨ４排放夜间出现一个次峰。ＣＨ４和Ｎ２Ｏ排放总量因肥料类型而不同，堆肥加尿素处理比ＮＨ４ＨＣＯ３处理少排放Ｎ２Ｏ３０％，多排放ＣＨ４１２％。

农垦与放牧对内蒙古草原N_2O、CO_2排放和CH_4吸收的影响

利用优选静态箱 /气相色谱法 (GC) ,首次对我国内蒙古草原典型地区进行了人类活动对N2 O、CO2 和CH4交换通量影响的实验观测 .结果表明 ,农垦麦田N2 O平均排放通量比原始草原高出 3倍 ,并改变了草甸草原为CO2 汇的性质 ,使其季节排放净通量以C计增加 1 4 .3mg·(m2 ·h) - 1.随放牧强度的增加CO2 排放通量呈线性增长 ,轻牧会引起草原对CH4 吸收的大幅增加 ,而随着放牧压力的增大 ,增加值迅速回落 .农垦麦田与草甸草原相比地 气间CH4 交换无显著变化 ,放牧强度对N2 O排放影响无显著规律 .土壤湿度和温度是影响草原排放N2 O和CO2 、吸收CH4 季节变化形式的关键因子 ,而人类活动仅影响排放强度 .排放和吸收量年际间差异很大 ,但主要受降水的影响 .N2 O和CO2 排放与CH4

不同种类有机肥施用对稻田CH_4和N_2O排放的综合影响

以麦茬稻田为对象 ,研究基肥施用不同有机肥对稻田CH4 和N2 O排放的综合影响 .结果表明 :有机肥施用对稻田CH4 和N2 O排放的季节变化模式无明显影响 ,但影响其排放量 .与施用化肥 (化肥处理 )相比 ,施用菜饼 +化肥 (菜饼处理 )促进CH4 和N2 O的排放 ,其季节排放总量分别增加了 2 5 2 %和 2 2 %;施用小麦秸秆 +化肥 (秸秆处理 )和牛厩肥 +化肥 (牛厩肥处理 )明显增加CH4 排放 ,增加量分别为 2 5 0 %和 45 %,同时却减少N2 O排放 ,分别减少 1 8%和 2 1 %;施用猪厩肥 +化肥 (猪厩肥处理 )降低CH4 和N2 O的排放 ,分别降低 4%和 1 8%.对CH4 和N2 O排放的综合温室效应分析表明 ,菜饼和秸秆处理的全球增温潜势 (GWP)约为化肥处理的 2 .5倍 ,牛厩肥和化肥处理基本持平 ,但施用猪厩肥可减少 1 0 %～ 1 5 %.各处理的GWP从高到低依次为菜饼、秸秆、牛厩肥、化肥和猪厩肥 .单位产量的GWP以秸秆处理最高 ,菜饼次之 ,牛厩肥比化肥处理略高 ,猪厩肥处理最低 .从本生长季来看 。

芦苇湿地温室气体甲烷(CH_4)排放研究

用封闭式箱法对辽河三角洲芦苇湿地温室气体 CH4 的观测结果表明 ,其排放有明显的季节变化规律。淹水前 ,土壤为 CH4 汇。淹水期间 ,有大量的 CH4 排放。排水后 ,CH4 排放明显减少。在测定期内 ,CH4 排放通量为 -968～2 73 4 μg CH4 l/ (m2· h)。另外 ,土壤中产生的 CH4 主要是通过芦苇植株的传输作用进入到大气中。试验结果还表明 ,有芦苇生长的湿地 CH4 排放是无芦苇生长的 1 5倍。同时 ,建议芦苇田应采用间歇灌溉的水分管理措施 ,这样既能促进植株生长 ,又能减少 CH4

微生物生物量C、土壤呼吸的季节性变化与黑土稻田甲烷排放

对黑土水稻田一个生长季中土壤微生物生物量C、土壤呼吸和甲烷排放通量进行了监测 .结果表明 ,在水稻生长初期 ,长效尿素能显著抑制微生物生物量C和土壤呼吸 (P <0 .0 5 ) .间歇灌溉措施对二者几乎没有影响 .间歇灌溉能减少稻田甲烷的排放 ,平均排放量比对照减少了 32 .5 % .长效尿素的施用稻田使甲烷的排放略有增加 .施用长效尿素的处理 。