藻型湖泊溶解有机碳特征及其对甲烷排放的影响

湖泊碳通量研究已成为全球碳循环研究的前沿和热点问题.本研究以太湖藻型湖区(西北湖区、梅梁湾、贡湖湾、西南湖区和湖心)为研究对象,基于为期一年的连续野外观测,旨在揭示富营养化湖泊DOC变化特征及其对CH₄排放的影响.结果表明,太湖藻型湖区DOC质量浓度均值为4.15 mg/L,且具有显著的空间变化.受外源输送和内部蓝藻增殖影响,西北湖区和梅梁湾DOC质量浓度较高,且其DOC时间变化与流域降雨量紧密相关,尤以西北湖区最为明显(R²=0.67,P<0.01).但在受外源输送影响较小的湖心区域,其DOC的时间变化主要受蓝藻生物量驱动(R²=0.60,P<0.01).太湖藻型湖区CH₄排放均值为0.083 mmol·m^-2·d^-1,不同湖区CH₄排放量差异明显.藻型湖区较高的蓝藻生物量显著提高了CH₄的排放量,且DOC含量是蓝藻影响CH₄产生和排放的主要因子.总体上,太湖藻型湖区DOC的累积致使其是CH₄排放的热点区域,但DOC对CH₄产生和排放的影响受湖泊内部因子和外部因子的综合调控,其潜在的控制机制还需要进一步探讨.     

1970—2018年中国甲烷排放量时空分布特征及行业排放源分析

在100年时间尺度上,甲烷(CH₄)气体的全球增温潜势是CO₂的25倍,研究CH₄排放的时空特征及排放源组成结构对于国家"双碳目标"的实现具有重要价值.本文基于全球大气研究排放数据库(EDGAR)中的数据集,刻画了中国CH₄排放的时空分布特征,利用空间自相关和热点分析方法,揭示了CH₄排放的空间集聚效应,并基于不同的行业部门排放数据对CH₄的排放源进行分析.研究表明:1970—2018年CH₄排放的热点区主要分布在我国的华东、华北以及华南地区,有逐渐向西北地区延伸的趋势;年CH₄排放量平均值达8.33 t·a^-1·km^-2,变化曲线总体上呈现平缓上升—急速上升—稳定排放三个阶段;从各行政区的排放量来看,上海一直处于最高,全市排放量十年间平均值不低于25 t·km^-2;能源活动和工业生产的CH₄排放量贡献突出,尤其是交通运输和煤炭开采近些年排放占比逐渐攀升.     

不同CO2浓度和施氮水平对麦田CO2净通量的影响

为研究不同CO₂浓度和施氮量对麦田CO₂净通量的影响,利用开顶式气室(OTC)组成的CO₂浓度自动调控平台模拟CO₂浓度升高环境.以冬小麦为试验材料,设置CK (对照,环境大气CO₂浓度)、C₁(CO₂浓度比CK增加120 μmol·mol^-1)和C₂(CO₂浓度比CK增加200 μmol·mol^-1)3个CO₂浓度水平;施氮量设置常规施氮量(N₁,25 g·m^-2)和低氮(N₂,15 g·m^-2)2个水平.采用静态箱-高精度气体分析仪观测麦田CO₂净通量.结果表明:各处理的麦田CO₂净通量变化特征一致,均呈先增大后减小的趋势,在拔节期和抽穗期达到峰值.N₁处理下,在整个生育期,CK、C₁和C₂处理的CO₂累积量分别为-105.8±12.6、-123.1±11.5和-120.2±4.1 kg·hm^-2.N₂处理下,在整个生育期,CK、C₁和C₂处理的CO₂累积量分别为-82.3±9.2、-95.4±7.6和-96.7±2.8 kg·hm^-2;拔节期C₂处理的CO₂累积量比CK显著增加了31.8%(P=0.024).C₁处理下,拔节期N₁处理的CO₂累积量显著高于N₂处理55.0%(P=0.009);C₂处理下,N₁处理的整个生育期CO₂累积量显著高于N₂处理23.6%(P=0.010).各处理CO₂净通量跟土壤湿度的相关关系均达到显著;N₁处理下,C₁和C₂处理的CO₂净通量跟光合有效辐射的相关关系达到显著,N₂处理下,CK和C₁处理的CO₂净通量跟光合有效辐射的相关关系达到显著;N₁处理下,C₁处理的CO₂净通量跟空气温度的相关关系达到显著,其余处理未达到显著.本研究表明:在小麦的拔节期和抽穗期,相比于CO₂浓度升高,施氮量对麦田CO₂净通量的影响更为显著;CO₂浓度升高与施氮量对麦田CO₂净通量的影响没有显著的交互作用.     

美丽中国背景下云南省农业活动甲烷排放量计算与情景预测分析

运用CH4MOD模型和排放因子法对云南省农业活动CH₄排放量进行计算分析,并运用情景分析法对云南省农业活动CH₄排放量进行预测.研究结果表明:1)云南省2010—2019年农业源CH₄排放总量变化趋势为先波动上升再迅速减少最后趋于平稳,其中动物肠道发酵排放量贡献最大;2)云南省2010—2019年农业源CH₄单位农业增加值排放强度呈下降趋势,单位农地面积排放强度为波动状态;3)云南省2020—2029年不同情景下农业活动CH₄排放量预测均为上升趋势.由此从水稻种植和畜禽养殖两方面提出减排措施,以期实现"双碳"目标和美丽中国建设.     

铜基材料的制备及其光催化还原CO2的实验研究

光催化还原技术可以将CO₂气体转化成高附加值有机物,实现CO₂资源化利用。TiO₂作为常见的光催化材料,具有价格低廉、化学稳定性高等优点。虽其自身的光谱响应范围较窄,且其电子空穴复合率太高,导致其作为光催化材料的催化效率大大降低,但可以通过半导体复合的方式提高其光催化性能。以硫脲和二水氯化铜团制备出硫化亚铜Cu₂S-TiO₂-X,通过高温水热复合到基体上,通过X射线衍射、X射线电子能谱、扫描电镜、紫外光可见光分度计等表征手段研究了其物理特性,并进行了CO₂还原实验。结果表明:Cu₂S-TiO₂-1.0的光催化还原性最强,其CH₄产率为0.12 μmol/(g·h);随着Cu₂S含量的减少,CH₄产率先增加后减少。     

海南岛甲烷浓度空间异质性规律解析

温室气体排放升高对全球气候变暖有重要影响,其浓度分布的空间异质性及与局地气候变化和社会经济的关系是影响温室气体减排策略制定的关键因素.海南岛是国家生态文明建设的试验区,温室气体减排方面也面临着目标考核的压力与责任.本研究使用GHGSat的CH₄浓度产品、气温、降雨、GDP和人口数据集,采用Theil-Sen趋势分析、Mann-Kendall (MK)检验构建地理加权回归(GWR)模型,分析了2020—2021年海南岛CH₄浓度变化趋势及规律.结果表明:1)时空尺度上,2020—2021年海南岛CH₄浓度整体呈下降趋势,CH₄浓度均值为1 848.40×10^-9 mol／mol,8—11月的CH₄浓度低于均值,其余月份均值皆高于均值;海南岛46.42％的区域CH₄浓度呈显著减小趋势,主要集中在海南岛的西部及东部地区.2) CH₄浓度时空分布的异质性规律方面,GWR模拟结果显示,海南岛CH₄浓度与气温回归系数值分布于-114.92~127.80,CH₄浓度与降雨回归系数分布集中于-297.40~399.91,而CH₄浓度与GDP和人口的回归系数较高,分别集中于-4 125.55~4 509.07和-1 751.43~1 556.41,GWR能够揭示像元尺度上CH₄浓度分布对气候与社会经济因子的响应规律.3)拟合方法选择上,基于普通最小二乘法(OLS)与GWR方法对CH₄浓度与气温、降雨、GDP和人口的拟合结果的R²分别为0.14和0.83,表明海南岛CH₄浓度分布受气候和社会经济的局地效应影响显著,GWR方法在解释CH₄浓度分布影响因素方面比OLS的拟合效果更优.本研究揭示了海南岛CH₄浓度变化趋势及其空间变异规律,能够为海南CH₄浓度时空分布的动态评估提供方法参考.     

不同类型有机肥对珠三角水稻产量和温室气体排放的影响

水稻田是甲烷(CH₄)和氧化亚氮(N₂O)的重要排放源.以珠三角地区典型双季稻为研究对象,设置了无肥(CK)、化肥(CF)、条垛有机肥(SOF)、促腐有机肥(COF)、新鲜有机肥(FOF)和灭菌有机肥(STOF)共6种处理,采用静态暗箱-气相色谱法,研究等氮量施用不同类型有机肥对水稻产量以及温室气体CH₄和N₂O排放的影响.结果如下:1)水稻产量依次为STOF> FOF> COF> CF> SOF> CK.STOF、FOF和COF处理相对于化肥处理增加了水稻产量,分别为19.3％、17.1％和15.5％(P<0.05);FOF、STOF和COF处理相对于化肥处理增加了水稻田的经济效益,分别为69.4％、41.2％和24.2％.2)早稻和晚稻CH₄累积排放量依次为COF> FOF> SOF> STOF> CF> CK.COF、FOF、SOF和STOF处理相对于化肥处理增加了早稻和晚稻CH₄的累积排放量,分别为333.5％、261.3％、154.1％和128.6％(P<0.05).3)水稻生长期间各施肥处理N₂O的排放量均处于较低水平,该地区水稻田主要的温室气体仍然为CH₄.4)4种类型有机肥处理相对于化肥处理均显著增加了水稻田的全球增温潜势和温室气体排放强度.从全生命周期来看,COF由于堆肥时间较短、温室气体排放最少,在实际应用中不仅可以提高经济效益,同时也可以兼顾生态环境效益.     

在用机动车基于台架试验CO2排放因子研究

本研究选取14辆中国目前常用的在用轻型和重型机动车,利用底盘测功机,分别在WLTC (世界轻型车测试程序)和C-WTVC (中国重型商用车辆瞬态循环)工况的冷启动程序下,测试CO₂排放因子,同时研究了相应的油耗,并比较不同的影响因素.结果表明:机动车CO₂排放因子受到排量、冷热启动、燃料和驾驶路段的影响;机动车在城市路段冷启动条件下油耗最高,导致CO₂排放因子更高,比全工况冷启动和城市路段热启动条件下分别高出了26.6％~199.7％和8.3％~35.5％;高排量重型柴油货车在市区油耗更高,导致CO₂排放因子大幅增加,因此禁止大排量重型柴油货车进入市区能有效控制CO₂排放;使用液化石油气替代燃油会降低机动车CO₂的排放,液化石油气公交车和出租车在城市路段的CO₂排放分别降低37.2％和12.1％,而高速路段则分别降低51.8％和20.3％;当前更为符合道路实际的WLTC工况依旧会对中国实际道路轻型机动车CO₂排放因子和油耗分别产生31％~46％和17.7％~26.8％的低估.为了得到更为准确的排放因子数据,我国须加快工况的本土化改良.     

CO2强化再生骨料的特性及其对再生混凝土性能的影响

CO₂强化不同品质和粒径再生骨料的特性研究尚不系统和完善。在约20% CO₂浓度和自然环境压力条件下,考虑再生粗骨料（RCA）品质和粒径的影响,试验测试了CO₂强化再生骨料（CRCA）的碳化率、CO₂吸收率、碱度、残留CO₂气体含量、吸水率及CO₂强化再生骨料混凝土（CRAC）的抗压强度和抗氯离子渗透性能。结果表明：CO₂强化再生骨料的碳化率和CO₂吸收率随再生骨料水灰比的增加而增加;CO₂强化显著降低了再生骨料的碱度,且CO₂强化再生骨料粒径越小、水灰比越低,其残留CO₂气体含量越高;CO₂强化显著降低了再生骨料的吸水率,明显提升CO₂强化再生骨料混凝土的抗压强度和抗氯离子渗透性能。     

东亚地区二氧化碳体积分数变化特征

利用2004年以来东亚地区10个本底观测站大气φ(CO₂)观测资料,分析了各站大气φ(CO₂)的变化特征及其各站之间的差异,讨论了下垫面特征、源汇作用等对φ(CO₂)变化的影响.结果表明:10个本底站大气月均φ(CO₂)有明显的季节变化,高值多出现在冬春等寒冷季节,而低值则多出现在6—9月,属于北半球的夏季;大气φ(CO₂)日变化趋势较为一致,15时(当地时间)前后达到全天最低,随后φ(CO₂)升高,并在日落后继续积累,至清晨7时(当地时间)前后达到全天最高,之后φ(CO₂)随着太阳辐射的增强而逐渐降低,且平均φ(CO₂)水平与下垫面植被量成反比,φ(CO₂)日变化的幅度与下垫面植被量成反比.作为全球基准站之一的瓦里关山站,2004—2008年φ(CO₂)年均值逐年增加,年增长率为2.28×10^-6/a.     

Component fractionation of temporal evolution in adsorption–desorption for binary gas mixtures on coals from Haishiwan Coal Mine

Adsorption–desorption experiments on CO₂–CH₄ gas mixtures with varying compositions have been conducted to study the fractionation characteristics of CO₂–CH₄ on Haishiwan coal samples. These were carried out at constant temperature but different equilibrium pressure conditions. Based on these experimental results, the temporal evolution of component fractionation in the field was investigated. The results show that the CO₂ concentration in the adsorbed phase is always greater than that in the original gas mixture during the desorption process, while CH₄ shows the opposite characteristics. This has confirmed that CO₂, with a greater adsorption ability has a predominant position in the competition with CH₄ under different pressures. Where gas drainage is employed, the ratio of CO₂ to CH₄ varies with time and space in floor roadways used for gas drainage, and in the ventilation air in Nos.1 and 2 coal seams, which is consistent with laboratory results.     

Preferential adsorption behaviour of CH4 and CO2 on high-rank coal from Qinshui Basin,China

In order to better understand the prevailing mechanism of CO₂ storage in coal and estimate CO₂ sequestration capacity of a coal seam and enhanced coalbed methane recovery (ECBM) with CO₂ injection into coal, we investigated the preferential adsorption of CH₄ and CO₂ on coals. Adsorption of pure CO₂, CH₄ and their binary mixtures on high-rank coals from Qinshui Basin in China were employed to study the preferential adsorption behaviour. Multiple regression equations were presented to predict CH₄ equilibrium concentration from equilibrium pressure and its initial-composition in feed gas. The results show that preferential adsorption of CO₂ on coals over the entire pressure range under competitive sorption conditions was observed, however, preferential adsorption of CH₄ over CO₂ on low-volatile bituminous coal from higher CH₄-compostion in source gas was found at up to 10 MPa pressure. Preferential adsorption of CO₂ increases with increase of CH₄ concentration in source gas, and decreases with increasing pressure. Although there was no systematic investigation of the effect of coal rank on preferential adsorption, there are obvious differences in preferential adsorption of gas between low-volatile bituminous coal and anthracite. The obtained preferential adsorption gives rise to the assumption that CO₂ sequestration in coal beds with subsequent CO₂-ECBM might be an option in Qinshui Basins, China.     

人工红树林碳通量变化特征及其影响因素分析

红树林是重要的滨海蓝碳生态系统.人工红树林在恢复过程中碳交换过程受到气候、植被等环境的影响,与成熟红树林呈现较大差异.本研究采用闭路涡动相关系统对珠江河口人工红树林湿地生态系统进行二氧化碳(CO2)通量和甲烷(CH4)通量的观测,并基于通径分析方法探讨了环境要素对总初级生产力(GPP)、生态系统呼吸(Re)、CO2和C...     

Nitrogen enhanced drainage of CO_2 rich coal seams for mining

Coal seams with high CO_2 gas contents can be difficult to drain gas for outburst management. Coal has a high affinity for CO_2 with adsorption capacities typically twice that of CH_4. This paper presents an analysis of nitrogen injection into coal to enhance drainage of high CO_2 gas contents. Core flooding experiments were conducted where nitrogen was injected into coal core samples from two Australian coal mining basins with initial CO_2 gas contents and pressures that could be encountered during underground mining. Nitrogen effectively displaced the CO_2 with mass balance analysis finding there was only approximately 6%–7% of the original CO_2 gas content residual at the end of the core flood. Using a modified version of the SIMED II reservoir simulator, the core flooding experiments were history matched to determine the nitrogen and methane sorption times. It was found that a triple porosity model(a simple extension of the Warren and Root dual porosity model) was required to accurately describe the core flood observations. The estimated model properties were then used in reservoir simulation studies comparing enhanced drainage with conventional drainage with underground in seam boreholes. For the cases considered, underground in seam boreholes were found to provide shorter drainage lead times than enhanced drainage to meet a safe gas content for outburst management.     

江苏省主要农作物碳足迹动态及其构成研究

江苏作为农业大省和粮食主产区,全面核算其主要农作物生产碳足迹时序动态变化与构成,可为江苏省主要作物生产体系全过程环境管理及农业绿色发展提供决策依据.本文采用生命周期评价法(LCA)核算江苏省1990—2019年水稻、小麦、玉米、大豆和油菜5种作物生产过程各环节碳排放强度,研究分析不同作物生产碳足迹时序动态变化、构成及影...     

不同类型稻田亚硝酸型CH4厌氧氧化潜力的比较研究

甲烷(CH₄)厌氧氧化是稻田土壤中消减温室气体排放的重要过程.本试验选择内陆性南京稻田和滨海性上海崇明岛围垦稻田,比较研究稻田耕层(0~10 cm)和深层(50~60 cm)土壤中亚硝酸盐型CH₄厌氧氧化(n-DAMO)潜力的差异及其微生物驱动机制.结果表明,南京稻田耕层土壤的n-DAMO速率为3.51 nmol·g^-1·d^-1(以¹³CO₂计),显著高于围垦稻田耕层土壤(1.43 nmol·g^-1·d^-1).两种类型稻田耕层土壤的n-DAMO速率均显著高于深层土壤.南京稻田和围垦稻田M.oxyfera-like细菌的16S rRNA基因拷贝数分别为(2.31~4.82)×10⁷和(0.89~2.12)×10⁷ copies·g^-1,与亚硝酸盐型CH₄厌氧氧化速率显著正相关.相关性分析发现,土壤有机碳、总氮、无机态氮是稻田n-DAMO速率分异的重要原因.综上所述,内陆性稻田土壤n-DAMO氧化潜力较高,其主要由较高的土壤本底碳、氮水平和功能微生物丰度所致.     

Numerical Simulation and Analysis of Migration Law of Gas Mixture Using Carbon Dioxide as Cushion Gas in Underground Gas Storage Reservoir

One of the major technical challenges in using carbon dioxide（ CO2） as part of the cushion gas of the underground gas storage reservoir（ UGSR） is the mixture of CO2and natural gas. To decrease the mixing extent and manage the migration of the mixed zone,an understanding of the mechanism of CO2and natural gas mixing and the diffusion of the mixed gas in aquifer is necessary. In this paper,a numerical model based on the three dimensional gas-water two-phase flow theory and gas diffusion theory is developed to understand this mechanism. This model is validated by the actual operational data in Dazhangtuo UGSR in Tianjin City,China.Using the validated model,the mixed characteristic of CO2and natural gas and the migration mechanism of the mixed zone in an underground porous reservoir is further studied. Particularly,the impacts of the following factors on the migration mechanism are studied： the ratio of CO2injection,the reservoir porosity and the initial operating pressure. Based on the results,the optimal CO2injection ratio and an optimal control strategy to manage the migration of the mixed zone are obtained. These results provide technical guides for using CO2as cushion gas for UGSR in real projects.     

Numerical analyses and experiment investigations of an annular micro gas turbine power system using fuels with low heating values

This study investigates the effects of using fuels with low heating values on the performance of an annular micro gas turbine (MGT) experimentally and numerically. The MGT used in this study is MW-54, whose original fuel is liquid (Jet A1). Its fuel supply system is re-designed to use biogas fuel with low heating value (LHV). The purpose is to reduce the size of a biogas distributed power supply system and to enhance its popularization. This study assesses the practicability of using fuels with LHVs by using various mixing ratios of methane (CH₄) and carbon dioxide (CO₂). Prior to experiments, the corresponding simulations, aided by the commercial code CFD-ACE+, were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when LHV gas was used. The main purposes are to confirm that there are no hot spots occurring in the liners and the exhaust temperatures of combustor are lower than 700°C when MGT is operated under different conditions. In experiments, fuel pressure and mass flow rate, turbine rotational speed, generator power output, and temperature distribution were measured to analyze MGT performance. Experimental results indicate that the presented MGT system operates successfully under each tested condition when the minimum heating value of the simulated fuel is approximately 50% of pure methane. The power output is around 170 W at 85000 r/min as 90% CH₄ with 10% CO₂ is used and 70 W at 60000 r/min as 70% CH₄ with 30% CO₂ is used. When a critical limit of 60% CH₄ is used, the power output is extremely low. Furthermore, the best theoretical Brayton cycle efficiency for such MGT is calculated as 23% according to the experimental data while LHV fuel is used. Finally, the numerical results and experiment results reveal that MGT performance can be improved further and the possible solutions for performance improvement are suggested for the future studies.