农田土壤主要温室气体(CO2、CH4、N2O)的源/汇强度及其温室效应研究进展

气候变化是当今全球面临的重大挑战, 人类社会生产生活引起的温室气体排放是全球气候变暖的主要原因。大气中CO₂、CH₄ 和N₂O 是最重要的温室气体, 对温室效应的贡献率占了近80%。据估计, 大气中每年有5%~20%的CO₂、15%~30%的CH₄、80%~90%的N₂O 来源于土壤, 而农田土壤是温室气体的重要排放源。本文重点阐述了农田土壤温室气体产生、排放或吸收机理及其影响因素, 指出土地利用方式和农业生产力水平等人为控制因素通过影响土壤和作物生长条件来影响农田土壤温室气体产生与排放或吸收。所以, 我们可以从人类活动对农田生态系统的影响着手, 通过改善农业生产方式和作物生长条件来探索温室气体减排措施, 达到固碳/氮增汇的目的。对国内外关于农田温室气体排放的源/汇强度及其综合温室效应评估的最新研究进展进行了综述, 指出正确估算与评价农田土壤温室气体的源/汇强度及其对大气中主要温室气体浓度变化的贡献, 有助于为温室气体减排以及减少气候变化预测的不确定性提供理论依据。     

稻鸭共作对不同栽培环境稻季CH4和N2O排放的影响

稻田是大气温室气体甲烷(CH₄)和氧化亚氮(N₂O)的重要排放源, 稻田温室气体减排一直是生态农业研究的热点。目前, 采用水稻品种选择利用、水分控制管理、肥料运筹管理、耕作制度调整以及种养结合模式等方法来减少稻田温室气体排放有较好实践效应, 但不同稻田栽培环境(露地、网室)基础上的稻鸭共作对麦秸全量还田的稻田温室气体排放特征及相关土壤理化特性关联性的影响尚为少见。本研究采用裂区设计, 在两种栽培环境条件下, 以无鸭子放养的常规稻作和麦秸不还田为对照, 在等养分条件下分析麦秸全量还田与稻鸭共作模式对稻田土壤氧化还原电位、CH₄排放量、产CH₄潜力及CH₄氧化能力、N₂O排放量及N₂O排放高峰期土壤反硝化酶活性、全球增温潜势、水稻产量的影响, 为稻田可持续生产和温室气体减排提供参考。结果表明, 麦秆还田增加了稻田产CH₄潜力、提高了CH₄排放量, 降低了稻田土壤反硝化酶活性、土壤氧化还原电位和N₂O排放量, 整体上导致全球增温潜势上升96.89%~123.02%; 稻鸭共作模式, 由于鸭子的不间断活动提高了稻田土壤氧化还原电位, 降低了稻田产CH₄潜力, 增强了稻田CH₄氧化能力, 从而降低稻田CH₄排放量, N₂O排放量虽有提高, 整体上稻鸭共作模式的全球增温潜势较无鸭常规稻田下降8.72%~14.18%; 网室栽培模式显著提高了稻田土壤氧化还原电位, 降低稻田产CH₄潜力、CH₄氧化能力和土壤反硝化酶活性, 减少了稻田CH₄和N₂O排放量, 全球增温潜势降低6.35%~13.14%。本试验条件下, 稻田土壤的CH₄氧化能力是产CH₄潜力的2.21~3.81倍; 相同环境条件下, 稻鸭共作和麦秸还田均能增加水稻实际产量, 网室栽培的所有处理较相应的露地栽培减少了水稻实际产量1.19%~5.48%。本试验表明, 稻鸭共作和网室栽培可减缓全球增温潜势, 稻鸭共作和麦秸还田能够增加水稻实际产量。     

堆放奶牛粪便温室气体排放及影响因子研究

用静态箱—气相色谱法对两种不同堆放方式的奶牛粪便(自然堆放和覆盖玉米秸秆)在4个不同时段的温室气体排放速率进行了观测，结果表明：各个时段两种处理的温室气体排放速率变化趋势基本一致，但各个时段的排放速率有明显差异。两种处理温室气体的排放速率与牛粪温度相关极显著。覆盖玉米秸秆会减少CO₂、N₂O的排放，而且第3时段(2006年5月14日～6月14日)CO₂的排放速率和第4时段(2006年8月2日～8月30日)N₂O的排放速率与自然堆放的均差异显著；不同时段覆盖对CH₄的排放影响不同，第4时段覆盖处理的CH₄排放速率上升，并且与自然堆放的差异显著；其他时段两种处理温室气体的排放速率无显著差异。     

有机农业发展的低碳机理分析

温室气体排放引起的全球气候变暖是人类关注的环境热点问题之一。本文从农业生态系统影响全球变暖的主要温室气体(CO₂、N₂O 和CH₄)的产生和排放出发, 探讨有机农业在生产减排和土壤固碳方面的机理。研究发现相对于常规农作而言, 有机农业在减排和固碳方面具有很大优势和潜力; 然而, 从长期来看, 通过土壤固碳减少大气温室气体的排放不是无限制的, 到一定程度后会达到一个平衡。因此, 更多的有效固碳途径和管理措施有待于进一步研究。同时, 从低碳理念出发, 强调中国加强有机农业环境效益研究的必要性。     

生物炭和秸秆还田对干旱区玉米农田土壤温室气体通量的影响

为了研究生物炭及秸秆还田对干旱区玉米农田温室气体通量的影响,以内蒙古科尔沁地区玉米农田为试验对象,采用静态箱-气相色谱法对分别施入生物炭0 t·hm^-2（CK）、15 t·hm^-2（C15）、30 t·hm^-2（C30）、45 t·hm^-2（C45）及秸秆还田（SNPK）的土壤进行温室气体（CO₂、CH₄和N₂O）通量的原位观测,并估算生长季CH₄和N₂O的综合增温潜势（GWP）与排放强度（GHGI）。结果表明：添加生物炭能够显著减少土壤CO₂和N₂O的排放量,并促进土壤对CH₄的吸收作用。其中处理C15对CO₂的减排效果最好,与对照相比CO₂排放量降低21.16%。随着施入生物炭量的增加,生物炭对N₂O排放的抑制作用不断增强,处理C45对减排效果最好,与对照相比N₂O排放量降低86.25%。处理C15对土壤吸收CH₄的促进效果最好,CH₄吸收量增加56.62%;处理C45对CH₄的排放有促进作用,使生长季土壤吸收CH₄减少81.36%。SNPK对温室气体的减排作用接近处理C15。添加生物炭和秸秆还田对提高玉米产量和降低农田GWP与GHGI均有显著效果,施用生物炭及秸秆还田均有效提高了科尔沁地区的玉米产量,且玉米产量随着施入生物炭含量的增大而提升。从GWP上来看,施用15 t·hm^-2生物炭对温室气体减排的整体效果最好。从GHGI上来看,施用生物炭及秸秆还田均具有一定的经济效益和减排意义,其中施用15 t·hm^-2生物炭的综合效益最高。因此综合经济效益与环境因素,建议科尔沁地区农田在种植玉米时添加15 t·hm^-2生物炭,如不具备购买生物炭条件,可以考虑秸秆还田来实现玉米增产与温室气体减排。     

铝箔复合膜气袋对温室气体吸附性的试验研究

为了解气袋对温室气体气样的吸附性,采用气相色谱仪对5 L气袋中CH₄、SF₆、CO₂、和N₂O标准气体浓度进行了连续监测。结果表明,CH₄、SF₆、CO₂和N₂O气体浓度的变异系数分别为6.72%,0.95%,3.86%和6.56%,气袋对4种温室气体的吸附性均不显著,该气袋用于以上温室气体的测定是可行的。     

气候变化下基于DayCent的旱地玉米农田温室气体排放通量模拟

气候变化通过大气CO₂浓度、温度和降雨的改变,直接或间接影响农田温室气体排放,研究未来气候情景下农田温室气体排放对实现农业碳减排具有重要意义。为探究气候变化背景下农田温室气体排放特征,该研究在长期田间定位试验基础上,利用当前大气CO₂浓度与CO₂浓度升高条件下旱作玉米农田温室气体排放通量的田间观测数据,采用“试错法”对DayCent模型进行校验,并利用校验后的模型,根据第六次国际耦合模式比较计划（Coupled Model Intercomparison Project phase 6,CMIP6）气候情景数据,预测未来SSP126与SSP245气候情景下旱地玉米农田温室气体排放通量。结果表明,DayCent模型对不同大气CO₂浓度下N₂O、CH₄和CO₂排放通量的模拟值与观测值高度一致,模拟效率（modeling efficiency,EF）分别为0.58～0.87、0.45～0.65和0.25～0.62,均方根误差（root mean square error,RMSE）分别为0.83～1.33、0.67～0.82和0.58～0.80 g/(hm²·d),决定系数（coefficient of determination,R²）分别为0.80～0.91、0.53～0.80和0.53～0.85。SSP126和SSP245气候情景下,在玉米单作种植模式下旱地农田N₂O和CO₂年排放量均呈现上升趋势,以2001—2020年农田温室气体排放通量为基准,到2060年N₂O年排放量分别增加22.8%和24.9%,CO₂年排放量分别增加6.7%和8.0%;旱地农田CH₄年吸收量呈下降趋势,两个气候情景下分别减少13.6%和13.4%。未来气候情景下旱地农田仍是温室气体排放源,优化氮肥管理和农田耕作措施对实现温室气体减排具有重要意义,模拟结果可以为制定农业适应气候变化对策提供基础数据支持。     

夏季休牧对高寒矮嵩草草甸温室气体排放的影响

以高寒矮嵩草草甸为研究对象，利用密闭箱－气相色谱法，对夏季休牧8a的围栏草地(休牧草地)和全年放牧的草地(放牧草地)的温室气体排放通量、土壤特性和生物量进行了对比研究。结果表明：与放牧草地相比，休牧草地植被盖度较之高41％，单位面积生物量较之高53％。同时，土壤特性也有较大不同；休牧草地的植被－土壤系统CO₂排放通量比放牧草地低20.7％，测定期间两者CO₂排放通量以每天每公顷排放C的质量计分别为30.7和38.7 kg·(hm²·d)^-1；试验期间高寒矮嵩草草甸植被－土壤系统是大气CH₄的弱汇，休牧后草地土壤对CH₄的吸收能力增强，休牧和放牧草地CH₄的平均吸收强度分别为28.1和21.9 g·(hm²·d)^-1；休牧草地土壤N₂O排放通量比放牧草地低，两者排放通量分别为4.5和7.6 g·(hm²·d)^-1。可见，夏季休牧措施降低了草地对大气中温室气体浓度增加的贡献。     

中国农村户用沼气工程建设对减排CO2、SO2的贡献——分析与预测

农村户用沼气工程是中国可再生能源建设的重点项目，可为农村居民生活提供清洁的可再生能源，该工程的建设能减轻农村环境污染，有助于部分缓解全球气候变暖的趋势。该文根据国际通用的减排量计算方法，对中国农村户用沼气替代传统生物质能和煤炭所产生的CO₂和SO₂的减排量进行了计算分析，为制定农村能源发展战略和农村环境发展规划提供参考。研究结果表明，在1996～2003年间，每年可减少CO₂排放39.76～419.39万t，减少SO₂排放2.13～6.20万t。通过对2010、2020和2050年沼气替代农村传统能源减排CO₂和SO₂量的预测，证明农村户用沼气工程的建设可以有效减少CO₂和SO₂的排放。     

夏季猪场污水贮存过程中CO2、CH4排放试验

猪场粪污是重要的温室气体排放源,针对中国缺乏猪场污水贮存过程中温室气体排放参数的问题,该文选择温度较高的夏季,利用动态箱法于2007年6月对猪场的三格式化粪池进行了CO<2、CH₄气体排放测试。测试结果表明：当大气平均温度为28.4℃时,86%的温室气体排放源于一级和二级化粪池,一级、二级和三级化粪池的温室气体排放通量分别为407.5、383.0、127.7 g/(m2?h)二氧化碳当量;CH₄是本污水贮存单元中产生的主要的温室气体,一、二、三级化粪池排放的温室气体总量中,CH₄排放的贡献率分别为95%、96%、95%,控制一、二级化粪池甲烷排放将大幅度减少猪场污水温室气体排放     

Study on Greenhouse Gas Emissions in Jiangsu Province

This paper has attempted to do a statistical analysis of the inventory of greenhouse gas emissions from Jiangsu province in 1990, based on the methods provided in IPCC Guidelines (1995), hereby to investigate and evaluate the present situation of emissions of GHGs such as CO₂, CH₄ from the energy sector, industries, and agriculture. The study has found the annual per capita GHG emissions as follows: CO₂, 1.97 ton/person; CH₄, 22.65 kg person^-1; N₂O, 0.11 kg person^-1. The emission levels are close to the national average, and half of the world average. Energy consumption activities, among other activities, is the main source of CO₂ emission in Jiangsu province, which accounts for 91.6% of the total emission. The emission of CH₄ can be traced mainly to the cultivation of rice, which accounts for 44.1% of the emission.

     

稻田种养结合循环农业温室气体排放的调控与机制

水稻在我国粮食作物种植中占据主导地位,在保障粮食安全、关系国计民生方面有着重要的作用。稻田是温室气体甲烷(CH_4)和氧化亚氮(N_2O)的重要排放源。因此,控制稻田温室气体排放对缓解全球温室效应具有重要作用。近年来,稻田种养结合循环农业在我国发展迅速,具有稳产增效、绿色发展的重要功效,同时显著影响了稻田温室气体排放特征以及全球增温潜势(global warming potential,GWP)。稻鸭共作、稻田养小龙虾、稻鱼共作、稻田养蟹、稻田养鳖等稻田种养结合循环农业模式,由于稻田养殖生物在稻田生态系统中添加生态位、延长食物链的增环作用,通过其持续运动、觅食活动等,不同程度地影响稻田温室气体的排放量和GWP,总体呈现出减缓温室效应的趋势。本文概述了稻田种养结合循环农业的CH_4和N_2O的排放特征及水分管理和施肥措施的影响效应,探讨了稻田种养结合循环农业的减排途径,并分析了稻田种养结合循环农业温室气体减排的研究前景,以期为我国稻田种养结合循环农业的健康发展和稻田生态系统减排增效提供参考。     

Effects of land use type and incubation temperature on greenhouse gas emissions from Chinese and Canadian soils

Purpose  

Land use type is an important factor influencing greenhouse gas emissions from soils, but the mechanisms involved in affecting potential greenhouse gas (GHG) emissions in different land use systems are poorly understood. Since the northern regions of Canada and China are characterized by cool growing seasons, GHG emissions under low temperatures are important for our understanding of how soil temperature affects soil C and N turnover processes and associated greenhouse gas emissions in cool temperate regions. Therefore, we investigated the effects of temperature on the emission of N₂O, CO₂, and CH₄ from typical forest and grassland soils from China and Canada.     

Influence of increasing temperature and nitrogen input on greenhouse gas emissions from a desert steppe soil in Inner Mongolia

We investigated the effect of increasing soil temperature and nitrogen on greenhouse gas (GHG) emissions [carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O)] from a desert steppe soil in Inner Mongolia, China. Two temperature levels (heating versus no heating) and two nitrogen (N) fertilizer application levels (0 and 100?kg?N?ha^?1?year^?1) were examined in a complete randomized design with six replications. The GHG surface fluxes and their concentrations in soil (0 to 50?cm) were collected bi-weekly from June 2006 to November 2007. Carbon dioxide and N₂O emissions were not affected by heating or N treatment, but compared with other seasons, CO₂ was higher in summer [average of 29.6 versus 8.6?mg carbon (C) m^?2?h^?1 over all other seasons] and N₂O was lower in winter (average of 2.6 versus 4.0?mg?N?m^?2?h^?1 over all other seasons). Desert steppe soil is a CH₄ sink with the highest rate of consumption occurring in summer. Heating decreased CH₄ consumption only in the summer. Increasing surface soil temperature by 1.3°C or applying 100?kg?ha^?1?year^?1 N fertilizer had no effect on the overall GHG emissions. Seasonal variability in GHG emission reflected changes in temperature and soil moisture content. At an average CH₄ consumption rate of 31.65?µg?C?m^?2?h^?1, the 30.73 million ha of desert steppe soil in Inner Mongolia can consume (sequestrate) about 85?×?10^6?kg CH₄-C, an offset equivalent to 711?×?10^6?kg CO₂-C emissions annually. Thus, desert steppe soil should be considered an important CH₄ sink and its potential in reducing GHG emission and mitigating climate change warrants further investigation.     

Water availability and abundance of microbial groups are key determinants of greenhouse gas fluxes in a dryland forest ecosystem

Forests are considered key biomes that could contribute to minimising global warming as they sequester carbon (C) and contribute to mitigate emissions of the potent greenhouse gases (GHG) including nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂). Management practices are prevalent in forestry, particularly in dryland ecosystems, known to be water and nitrogen (N) limited. Irrigation and fertilisation are thus routinely applied to increase the yield of forest products. However, the contribution of forest management practices to current GHG budgets and consequently to soil net global warming potential (GWP) is still largely unaccounted for, particularly in dryland ecosystems. We quantified the long-term effect (six years) of irrigation and fertilisation and the impact of land-use change, from grassland to a Eucalyptus plantation on N₂O, CH₄ and CO₂ emissions and soil net GWP, within a dryland ecosystem. To identify biotic and abiotic drivers of GHG emissions, we explored the relationship of N₂O, CH₄ and CO₂ fluxes with soil abiotic characteristics and abundance of ammonia-oxidizers, N₂O-reducing bacteria, methanotrophs and total soil bacteria. Our results show that GHG emissions, particularly N₂O and CO₂ are constrained by water availability and both N₂O and CH₄ are constrained by N availability in the soil. We also provide evidence of functional microbial groups being key players in driving GHG emissions. Our findings illustrate that GHG emission budgets can be affected by forest management practices and provide a better mechanistic understanding for future mitigation options.     

Strong pH influence on N2O and CH4 fluxes from forested organic soils

Greenhouse gas (GHG) emissions from farmed organic soils can have a major impact on national emission budgets. This investigation was conducted to evaluate whether afforestation of such soils could mitigate this problem. Over the period 1994–1997, emissions of methane (CH₄) and nitrous oxide (N₂O) were recorded from an organic soil site in Sweden, forested with silver birch (Betula pendula Roth), using static field chambers. The site was used for grazing prior to forestation. Soil pH and soil carbon content varied greatly across the site. The soil pH ranged from 3.6 to 5.9 and soil carbon from 34 to 42%. The mean annual N₂O emission was 19.4 (± 6.7) kg N₂O‐N ha^?1 and was strongly correlated with soil pH (r = ?0.93, P < 0.01) and soil carbon content (r = 0.97, P < 0.001). The N₂O emissions showed large spatial and temporal variability with greatest emissions during the summer periods. The site was a sink for CH₄ (i.e. ?0.8 (± 0.5) kg CH₄ ha^?1 year^?1) and the flux correlated well with the C/N ratio (r = 0.93, P < 0.01), N₂O emission (r = 0.92, P < 0.01), soil pH (r = ?0.95, P < 0.01) and soil carbon (r = 0.97, P < 0.001). CH₄ flux followed a seasonal pattern, with uptake dominating during the summer, and emission during winter. This study indicates that, because of the large N₂O emissions, afforestation may not mitigate the GHG emissions from fertile peat soils with acidic pH, although it can reduce the net GHG because of greater CO₂ assimilation by the trees compared with agricultural crops.     

Nitrogen addition impacts on the emissions of greenhouse gases depending on the forest type: a case study in Changbai Mountain,Northeast China

Purpose

Anthropogenic-induced greenhouse gas (GHG) emission rates derived from the soil are influenced by long-term nitrogen (N) deposition and N fertilization. However, our understanding of the interplay between increased N load and GHG emissions among soil aggregates is incomplete.

Materials and methods

Here, we conducted an incubation experiment to explore the effects of soil aggregate size and N addition on GHG emissions. The soil aggregate samples (0–10 cm) were collected from two 6-year N addition experiment sites with different vegetation types (mixed Korean pine forest vs. broad-leaved forest) in Northeast China. Carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) production were quantified from the soil samples in the laboratory using gas chromatography with 24-h intervals during the incubation (at 20 °C for 168 h with 80 % field water capacity).

Results and discussion

The results showed that the GHG emission/uptake rates were significantly higher in the micro-aggregates than in the macro-aggregates due to the higher concentration of soil bio-chemical properties (DOC, MBC, NO₃ ^?, NH₄ ⁺, SOC and TN) in smaller aggregates. For the N addition treatments, the emission/uptake rates of GHG decreased after N addition across aggregate sizes especially in mixed Korean pine forest where CO₂ emission was decreased about 30 %. Similar patterns in GHG emission/uptake rates expressed by per soil organic matter basis were observed in response to N addition treatments, indicating that N addition might decrease the decomposability of SOM in mixed Korean pine forest. The global warming potential (GWP) which was mainly contributed by CO₂ emission (>98 %) decreased in mixed Korean pine forest after N addition but no changes in broad-leaved forest.

Conclusions

These findings suggest that soil aggregate size is an important factor controlling GHG emissions through mediating the content of substrate resources in temperate forest ecosystems. The inhibitory effect of N addition on the GHG emission/uptake rates depends on the forest type.

     

Columns and Detectors Recommended in Gas Chromatography to Measure Greenhouse Emission and O2 Uptake in Soil: A Review

ABSTRACT

Gas chromatography (GC) is a technique used to analyze substances/molecules (as chemical species) with a system composed of chromatograph, column, and detector. This study has the objective of reviewing the use of GC in monitoring greenhouse gases (GHG; carbon dioxide: CO₂; methane: CH₄; nitrous oxide: N₂O) emission and O₂ (oxygen) uptake in soil, demonstrating results from experiments around the world and alternative use of sensors to monitor these gases in soil. Our study shows that the correct column and detector depend on analyzing gas and the advantages and disadvantages of the column and the detector. The columns, packed and capillary, have been more used and are considered better options to analyze GHG emission and O₂ uptake in soil science. Thermal conductivity detector (TCD), electron capture detector (ECD) and mass selective (MS) are great choice to monitor CO₂ emission; flame ionization detector (FID) equipped with methanizer allows the detection of CO₂ and CH₄ emission; and ECD detects the amount of N₂O emitted. Moreover, both, TCD and ECD, also can be used to detect O₂ uptake. GC system is complex, and to identify of GHG emission and O₂ uptake is necessary the use of column (packed or capillary) and may contain multiple detectors, i.e. three (TCD, ECD, and FID) or two detectors (FID and ECD). Field and laboratory study should be run to verify the efficacy of sensors to monitor GHG emission and O₂ uptake as an alternative of GC system.     

农业生物质能温室气体减排潜力

中国拥有丰富的农作物秸秆和畜禽粪污等农业废弃物资源。农业生物质能技术是促进农业废弃物资源有效利用的重要途径，既能够解决农业废弃物的环境污染问题、减少因焚烧或无序堆放排放温室气体，又能够替代化石能源减排CO2、提升土壤固碳能力，未来在"双碳"背景下发展潜力很大。该研究基于LCA全生命周期评价方法，研究8种不同生物质能技术的温室气体排放因子，核算农业生物质能转化与利用过程消耗能源的排放、抵扣化石能源减排、副产物土壤碳汇3个方面，并基于秸秆和畜禽粪污两大类农业废弃物资源禀赋及能源化利用潜力，预测3种不同情景下，农业生物质能替代化石能源的潜力，以及减排温室气体的贡献。结果表明，从减排因子看，热解炭气联产和规模化沼气/生物天然气技术的温室气体减排贡献最大。其次为成型燃料、捆烧供暖、生物质发电、炭化和燃料乙醇等技术，而户用沼气的减排贡献相对较小，8种不同生物质能技术的温室气体排放因子分别为-3.47、-3.20、-2.57、-2.63、-2.58、-2.48、-2.42 t/t（单位为标准CO2当量/标准煤当量）；基于现有政策及规划情景、技术水平提升情景、能源需求结构变化情景等3种不同情景下，评价农业生物质能对温室气体减排贡献潜力。结果显示，2030年农业生物质能替代化石能源潜力为6 490×104～7 664×104 t，温室气体减排贡献为1.97×108～2.34×108 t；2060年替代化石能源潜力为9 073×104～10 763×104 t，温室气体减排贡献为2.79×108～3.36×108 t。该研究为实现农业农村领域碳达峰碳中和目标提供数据支撑。