南极苔原近地面CO2、CH4、N2O浓度和通量的相互关系

在南极苔原,首次系统地研究了近地面CO2,CH4,N2O浓度及通量的相互关系,结果表明：天气条件对三种温室气体浓度日变化影响较大,在天气较晴稳及雪天条件下,CO2与CH4,N2O浓度日变化存在明显的消失关系,而在雨天这三种气体浓度日变化趋势基本一致,整个夏季CO2与CH4浓度变化趋势基本一致,而N2O却与二者浓度的变化趋势相反,另外,在雨,雪天气条件下CH4,N2O通量日变化存在消长关系,整个夏季二者的通量变化也存在明显的消长关系,南极苔原土壤对CH4主要起着汇的作用,对N2O主要起着源的作用,此外,CO2浓度变化对苔原CH4通量有较大影响,CO2浓度增加会适当减缓CH4汇的作用,甚至使南极苔原由CH4的汇变为源。     

南极Fides半岛CH4浓度监测

在南极法尔兹半岛（Fildes Peninsula）6个环境小区内采集了近地面气体样品,在室内分析了其中223个样品的CH3浓度,得出了这些小区内大气CH4平均浓度;其中沿海潮间带藻类发布区、企鹅聚集区和人类活动区CH4浓度显著高于全球CH4平均浓度及其他无人区,表明这些区域可能是南极地区大气CH4主要的源;而苔藓、地衣植被区CH4浓度显著低于内陆冰盖区和全球大气CH4平均浓度,表明苔原植被区可能是南极大气CH4重要的汇,还分析了苔藓植被区CH4浓度的夏季变化,在夏季2个多月内该植被区CH3浓度呈上升趋势;在相同的天气条件下,苔藓与地衣两不同植被区CH4浓度变化趋势基本相同;但两者土壤CH4通量存在明显的消长关系。     

南极Fildes半岛CH4浓度监测

在南极法尔兹半岛(FildesPeninsula)6个环境小区内采集了近地面气体样品,在室内分析了其中223个样品的CH4浓度,得出了这些小区内大气CH₄平均浓度;其中沿海潮间带藻类分布区、企鹅聚集区和人类活动区CH₄浓度显著高于全球CH₄平均浓度及其他无人区,表明这些区域可能是南极地区大气CH₄主要的源;而苔藓、地衣植被区CH₄浓度显著低于内陆冰盖区和全球大气CH4平均浓度,表明苔原植被区可能是南极大气CH₄重要的汇.还分析了苔藓植被区CH₄浓度的夏季变化,在夏季2个多月内该植被区CH₄浓度呈上升趋势;在相同的天气条件下,苔藓与地衣两不同植被区CH₄浓度变化趋势基本相同;但两者土壤CH₄通量存在明显的消长关系.     

内蒙古温带半干旱羊草草原温室气体N2O和CH4通量变化特征

利用透光密闭箱对内蒙古半干旱典型草原羊草草地土壤-植被系统温室气体N2O和CH4通量进行了较长期的原位观测研究.研究结果表明:内蒙古温带半干旱典型草原作为大气N2O的源和CH4的汇而起作用,N2O与CH4的通量强度分别是:0.6～22.6μgm-zh-1和-1～-217μgm-2h-1.N2O和CH4的通量具有明显的日变化和季节变化特征,并且主要的环境因子(温度、水分)对其有重要影响.N2O通量的季节变化特征表现为:夏季最高,由春、秋至冬逐次降低;CH4通量的季节变化特征表现为:由春至冬依次减弱.     

内蒙古温带半干旱羊草原温室气体N2O和CH4通量变化特征

利用透光密闭箱对内蒙古半干旱典型草原羊草草地土壤－植被系统温室气体N2O和CH4通量进行了较长期的原位观测研究,研究结果表明,内蒙古温带关干旱典型草原作为大气N2O的源和CH4的汇而起作用,N2O与CH4的通量强度分别是：0．6－22.6ugm^-2h^-1和－5－－217ugm^-2h^-1,N2O和CH4的通量具有明显的日变化和委节变化特征,并且主要的环境因子（温度,水分）对其有重要影响,N2O通量的季节变化特征表现为：夏季最高,由春,秋至冬逐次降低,CH4通量的季节变化特征表现为：由春至冬依次减弱。     

天然温带典型草原N2O和CH4通量的时间变化特征

以内蒙古温带半干旱典型草原类型羊草草原土壤为主要研究对象,利用静态箱技术在野外连续多年原位观测草地N2O和CH4排放通量.通过对1995,1998,1999,2001,2002和2003年的野外观测资料的数据分析,发现温带半干旱典型草原N2O通量的日变化特征明显,草原植物的不同生长阶段对其具有显著的影响;CH4通量的日变化没有明显的规律性特征,植物生长状态对其影响不明显,但对于草地吸收CH4的日较差有显著的影响.多年观测资料显示:我国温带草地N2O通量的排放峰值在四季中均有可能出现,低值通常出现在冬季,不同实验年份,不同季节都有出现N2O吸收通量的可能性,N2O季节通量的变化形式多样,通常是春、夏季较高,冬季最低.CH4通量季节变化规律相对明显,其峰值主要出现在春季,冬季较低.在不同的季节都观测到CH4的排放通量,这同草地出现N2O的吸收通量一样不影响温带草地作为N2O源和CH4汇的功能.N2O较CH4通量的年际变化显著,两者年通量的变异系数分别是71.6%和18.7%,5个实验观测年(跨9个年度),N2O和CH4年通量的平均值分别是:(1.14±0.82)kg·hm-2·a-1和(-3.52±0.66)kg·hm-2·a-1.统计分析结果表明:只有CH4的季节通量与降雨量之间存在显著线性关系.以此估算我国温带草地N2O和CH4年排放总量分别是:以氮计0.23 Tg和以碳计-0.83Tg,分别是全球温带草地N2O排放总量的23%以及全球土壤吸收CH4总量的11%.     

N_2/CO_2/H_2O抑制甲烷燃烧数值分析

建立了CH4-O2预混气体等容绝热燃烧、爆炸的零维数学模型,并以此为基础对惰性气体抑制CH4点火、燃烧和爆炸的微观化学动力学过程进行数值模拟.数值计算结果表明,N2,CO2和H2O的加入,大大延长了CH4-O2预混气体的点火延迟时间,同时降低了燃烧反应系统温度.N2,CO2和H2O能有效抑制CH4点火、燃烧和爆炸,一方面源于CH4和O2在混合气体中的摩尔浓度被降低,致使离解出的H,O,OH和CH3自由基减少;另一方面则源于N2,CO2和H2O作为第三体稳定分子参与三元碰撞反应,使高活性的自由基转变成了低活性的稳定分子.相同条件下,CO2和H2O除了重点参与三元碰撞反应外,还不同程度地参与其他链式反应,而N2则是完全不参与其他链式反应.这就导致N2,CO2和H2O的抑燃、抑爆的能力和效果存在差异.     

微生物在温室气体排放与吸收中的多样性

对N2O和CH4两种重要的温室气体进行了研究．结果表明它们的生物排放源主要来自土壤微生物过程．其中土壤微生物的硝化和反硝化作用是N2O的重要排放源,厌氧土壤通过反硝化作用能将N2O还原为N2,是N2O的弱的汇．CH4主要由土壤中甲烷产生菌在厌氧条件下产生．在好氧条件下,甲烷氧化菌将厌氧土壤产生的甲烷进行氧化,成为土壤甲烷的汇．由此可见土壤微生物在温室气体N2O和CH4的产生与消耗中起着十分重要的作用,体现了微生物在温室气体产生与排放中的多样性．     

二氧化碳置换甲烷试验中渗透率变化研究

为研究煤层注CO2置换CH4过程中煤样对气体的吸附特性及渗透率变化特征,利用沁水盆地圆柱体原煤试样,在恒定体积应力(36 MPa)及不同注入压力(1~5 MPa)条件下,进行CO2置换CH4试验。结果表明:煤体对CO2的渗透率高于CH4气体;置换试验中,随注入压力的降低,煤体中CO2吸附相浓度逐渐升高,而CH4气体吸附相浓度呈相反变化趋势;在试验压降范围内,煤体对CO2、CH4气体的吸附量分别降低了48.73%、68.04%,煤体解吸CH4能力强于CO2气体。同时,在置换过程中,煤样置换渗透率受有效应力效应、基质收缩效应及滑脱效应等作用影响,其随注入压力的降低呈现先降低再增大的变化关系,且渗透率最低值出现在压力3.25 MPa时;在体积应力36 MPa条件下,注入压力下降后期渗透率相对于初期提高了17.03%。     

长江三角洲稻田CH4及N2O排放规律的数值模拟

建立了CH4及N2O排放数值模式,模式可以正确反映稻田CH4及N2O排放特征,数值分析证实了水稻生长期内CH4及N2O排放的消长关系,并揭示出CH4与N2O年际排放量的正相关关系,气象因子中,生长期平均气温与NH4和N2O排放间存在明显正相关。敏感分析表明温度升高后,生长期平衡气温与CH4和N2O排放量之间的正相关关系将略有加强,反演了苏州地区近百年CH4及N2O排放状况,表明近期人类农业生产对温室效应具有巨大增进效应。     

森林土壤温室气体通量对森林管理和全球大气变化的响应

森林土壤是温室气体重要的源和汇。探讨不同森林管理和全球大气变化下土壤温室气体通量特征,为有效减少温室气体排放及森林可持续管理等提供参考。笔者从森林土壤温室气体(forest soil green house gases)、森林管理(forest mangement)和全球大气变化(global atmospheric change)3个关键研究点,查阅近年来相关研究成果,归纳森林管理和全球大气变化下土壤温室气体通量的一般性模式。CO₂、CH₄和N₂O是3种重要温室气体,其通量间存在协同、消长和随机型耦合关系。森林管理如火烧、采伐和造林等显著影响土壤温室气体通量。一般情况下,火烧导致土壤N₂O通量降低,CH₄吸收量增加,CO₂通量因火烧类型、火烧强度、生态系统类型不同出现增加、减低和无影响3种结果; 采伐通常导致土壤CO₂、CH₄和N₂O排放增加; 造林可使土壤CO₂排放减少,对N₂O和CH₄通量的影响随生态系统类型、造林树种等而改变。全球大气变化如CO₂浓度升高、氮沉降和气温升高影响森林土壤温室气体通量。通常,CO₂浓度升高导致土壤CO₂和N₂O排放量增加,CH₄吸收量降低; 氮沉降促进土壤N₂O排放、抑制CH₄吸收。气温升高导致土壤CO₂和N₂O排放增加。森林管理和全球大气变化对土壤温室气体通量的综合影响是非叠加的,有效的森林管理可能改变土壤温室气体通量对全球大气变化的响应。     

Fluxes of CO2, N2O and CH4 from a typical temperate grassland in Inner Mongolia and its daily variation

Using a dark enclosed chamber technique, the fluxes of CO2, N2O and CH4 from nature and disturbed grassland were measured on the spot in Inner Mongolian Temperate Grassland along the annual rainfall gradient section ranging from 450 to 200 mm. The results showed that the measured mean fluxes of CO2, N2O and CH4 were (1 180.4 ± 308.7), (0.010 ± 0.004) and (- 0.039 ± 0.016) mg·m?2/h, respectively. The decrease of the fluxes of CO2, N2O and CH4 follows with that of annual rainfall gradient in the measurement area. Human activities, such as grazing and reclamation are also critical factors to affect the fluxes of these gases from grassland. Daily continuous measurement of CO2, N2O and CH4 fluxes showed a strong diurnal variation with higher emission in the daytime. A good relationship between the fluxes of CO2, N2O, CH4 and temperature was exposed in this study.     

生物炭添加对土壤冻融过程中温室气体排放的影响

【目的】研究模拟生物炭添加对土壤冻融过程中二氧化碳(CO₂)、甲烷(CH₄)和氧化亚氮(N₂O)排放的影响,为冻融期土壤温室气体的减排提供参考。【方法】以伊犁河谷典型农田为研究对象,野外采集原状土柱,并在室内模拟不同幅度的冻融过程(+5 ℃、-5 ℃～ +5 ℃和-10 ℃ ～ +10 ℃),探求冻融过程中土壤CO₂、CH₄和N₂O排放对生物炭添加(0、20和40 t/hm²)的响应特征。【结果】与不添加生物炭的处理相比,添加生物炭会使冻融过程中的土壤CO₂排放量提高1.1～1.4倍,但该影响远小于冻融作用对土壤CO₂排放的促进作用(为CK的1.5～3.2倍); 虽然冻融作用未显著(P > 0.05)影响土壤CH₄的累积排放量,但生物炭的添加显著(P < 0.05)促进了45.5%～81.8%的CH₄吸收量; 冻融作用使土壤N₂O的累积排放量提高了1.3～3.0倍,生物炭降低了冻融过程中10.2%～30.9%的土壤N₂O排放量,但在多数情况下这种减小并不显著(P > 0.05)。【结论】模拟生物炭添加会增加土壤冻融过程中CO₂的排放,也会促进CH₄的吸收和N₂O的减排。     

Increased soil emissions of potent greenhouse gases under increased atmospheric CO2

Increasing concentrations of atmospheric carbon dioxide (CO(2)) can affect biotic and abiotic conditions in soil, such as microbial activity and water content. In turn, these changes might be expected to alter the production and consumption of the important greenhouse gases nitrous oxide (N(2)O) and methane (CH(4)) (refs 2, 3). However, studies on fluxes of N(2)O and CH(4) from soil under increased atmospheric CO(2) have not been quantitatively synthesized. Here we show, using meta-analysis, that increased CO(2) (ranging from 463 to 780 parts per million by volume) stimulates both N(2)O emissions from upland soils and CH(4) emissions from rice paddies and natural wetlands. Because enhanced greenhouse-gas emissions add to the radiative forcing of terrestrial ecosystems, these emissions are expected to negate at least 16.6 per cent of the climate change mitigation potential previously predicted from an increase in the terrestrial carbon sink under increased atmospheric CO(2) concentrations. Our results therefore suggest that the capacity of land ecosystems to slow climate warming has been overestimated.     

Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models

Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.     

The influence of Antarctic sea ice on glacial-interglacial CO2 variations

Ice-core measurements indicate that atmospheric CO2 concentrations during glacial periods were consistently about 80 parts per million lower than during interglacial periods. Previous explanations for this observation have typically had difficulty accounting for either the estimated glacial O2 concentrations in the deep sea, 13C/12C ratios in Antarctic surface waters, or the depth of calcite saturation; also lacking is an explanation for the strong link between atmospheric CO2 and Antarctic air temperature. There is growing evidence that the amount of deep water upwelling at low latitudes is significantly overestimated in most ocean general circulation models and simpler box models previously used to investigate this problem. Here we use a box model with deep-water upwelling confined to south of 55 degrees S to investigate the glacial-interglacial linkages between Antarctic air temperature and atmospheric CO2 variations. We suggest that low glacial atmospheric CO2 levels might result from reduced deep-water ventilation associated with either year-round Antarctic sea-ice coverage, or wintertime coverage combined with ice-induced stratification during the summer. The model presented here reproduces 67 parts per million of the observed glacial-interglacial CO2 difference, as a result of reduced air-sea gas exchange in the Antarctic region, and is generally consistent with the additional observational constraints.     

黑麦秸秆对土壤中无机氮转化和N_2O、CO_2释放的影响

在欧美国家,黑麦秸秆经常作为有机肥或农业废弃物而归还到农田中。本研究通过培养试验探讨了添加黑麦秸秆对土壤中无机氮的形态转化和N_2O、CO_2释放的影响。研究结果表明,黑麦秸秆的添加量及培养时间对土壤中N_2O、和CO_2释放量、N_2O/CO_2比值和无机氮形态转化均有明显影响。添加的黑麦秸秆越多,培养2周后土壤中的NH_4-N越多,释放的N_2O则越少。N_2O/CO_2比值与黑麦秸秆添加量呈极显著的负相关,与培养时间(T)的函数关系(达到极显著的负相关)则呈对数形式:(N_2O/CO_2)=a b·lnT。     

CH4/O2/CO2层流预混火焰传播速度实验研究

采用本生灯法,测量了CH4/O2/CO2混合气在不同工况下的层流预混火焰传播速度.采用基于火焰图像的全面积法计算本生灯火焰的传播速度.主要研究了化学当量比(08~12)、氧气体积分数(25%~35%)和稀释剂种类(N2,CO2)对火焰传播速度的影响规律.结果表明:当化学当量比为1时火焰传播的速度达到最大值,在其两侧火焰传播速度逐渐下降;火焰传播速度随着氧气体积分数的增加而增加,且火焰传播速度与氧气体积分数呈二次函数关系;与N2相比,高浓度CO2降低了火焰传播速度,CH4在O2/CO2气氛下的火焰传播速度约为O2/N2气氛下的五分之一.     

CH4、CO2与O2制合成气的研究(V)--催化剂床层的热波分布

采用微型固定床反应装置,研究了甲烷、二氧化碳和氧气制氧化重整合成气时Ni-Ce-Cu-Li／Al2O3催化剂床层的热波分布,考察了炉温和进料配比对催化剂床层热波分布的影响．研究结果表明：在甲烷、二氧化碳和氧气的氧化重整反应中,催化剂床层存在明显的热波现象;在相同的炉温下,甲烷部分氧化反应的热波强度最大,甲烷、二氧化碳和氧气的氧化重整反应次之;甲烷、二氧化碳的重整反应没有热波现象．热波现象进一步印证了甲烷、二氧化碳和氧气制氧化重整合成气的反应遵从燃烧-重整的反应机理．