Gaseous emissions from Canadian boreal forest fires

CO₂-normalized emission ratios (ΔX/ΔCO₂; V/V; where ΔX and ΔCO₂ = the enhancement of trace gas and CO₂, respectively, above background levels) for carbon monoxide (CO), hydrogen (H₂), methane (CH₄), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N₂O) were determined from smoke samples collected during low-altitude helicopter flights over two prescribed fires in northern Ontario, Canada. The emission ratios determined from these prescribed boreal forest fires are compared to emission ratios determined over two graminoid (grass) wetlands fires in central Florida and are found to be substantially higher (elevated levels of reduced gas production relative to CO₂) during all stages of combustion. These results argue strongly for the need to characterize biomass burning emissions from the major global vegetation/ecosystems in order to couple combustion emissions to their vegetation/ecosystem type. Such a process should improve the quality of any assessments of biomass burning impacts on atmospheric chemistry and climate.     

Simulation based life cycle assessment of airborne emissions of biomass-based ethanol products from different feedstock planting areas in China

Oil shortage and environmental deterioration urge people to pay more and more attention to Biomass-based Fuel Ethanol (BFE), because it is renewable and apparently environmentally friendly. This paper aims to assess and compare the air emissions of three BEF products from different feedstock planting areas in China. For the purpose of a “cradle to grave” study of biomass-based ethanol fuel as a substitute transportation fuel, the authors chose “vehicle fueled by biomass-based E10 (a blend of 10% ethanol and 90% gasoline, v/v)” as the subject. Then, life cycle emission models of Wheat-based E10 from central China, Corn-based E10 from northeast China, and Cassava-based E10 from southwest China were set up based on surveys; life cycle emission functions of CO₂, CO, N₂O, NO_x, SO₂, CH₄, VOC, and PM₁₀ were constructed and value of each emission category was calculated based on Monte Carlo simulation of the life cycle emission models. The calculation results showed that compared with gasoline-fueled vehicles, biomass-based E10-fueled vehicles release less CO₂ and VOC in their lifecycles, but wheat-based E10-fueled and cassava-based E10-fueled ones have more emissions of CO, CH₄, N₂O, NO_x, SO₂, PM₁₀ and corn-based E10-fueled ones have more emissions of CH₄, N₂O, NO_x, SO₂, PM₁₀. Suggestions on reducing the emissions have been proposed for future actions.     

Oxidation of organic substances in aqueous solutions over Ru catalysts by oxygen

The catalytic performance of supported Ru catalysts has been studied in the reactions of wet oxidation of acetonitrile, N,N-dimethyl formamide and carbamide at T=433–533 K and P=2.0–4.6 MPa, and wet oxidation of real sewage from an alcohol plant (so-called Luther water) at T=403–473 K and P=1.5–3.6 MPa. The Luther water contained a mixture of low-boiling (C₁–C₅) aldehydes and alcohols. The experiments were carried out in a perfectly mixed batch autoclave reactor. The conversion of alcohols and aldehydes contained in the Luther water and selectivity of the process towards CO₂ and water as well as the selectivity of the oxidation of acetonitrile, N,N-dimethyl formamide and carbamide towards CO₂, N₂ and water were determined at various temperatures and reaction times. Ru (4.8 wt.%)/graphite-like carbon was effective in the oxidation of Luther water (ΔTOC=97.5% at T=423 K for 1 h), carbamide (X_CO(NH2)2=100%, S_{CO(NH2)2→CO2}=100%, S_{CO(NH2)2→N2}=71% at 473 K, 2 h) and acetonitrile (X_CH3CN=100%, S_CH3CN→CO2=100%, S_CH3CN→N2=75% at 493 K, 1 h). Ru/active carbon/γ-Al₂O₃ was effective in the oxidation of N,N-dimethyl formamide (X_HCON(CH3)2=100%, S_{HCON(CH3)2→CO2}=61%, S_{HCON(CH3)2→N2}=100% at 493 K).     

Variability of Fire Behavior, Fire Effects, and Emissions in Scotch Pine Forests of Central Siberia

As part of the Russian FIRE BEAR (Fire Effects in the Boreal Eurasia Region) Project, replicated 4-ha experimental fires were conducted on a dry Scotch pine (Pinus sylvestris)/lichen (Cladonia sp.)/feathermoss (Pleurozeum schreberi) forest site in central Siberia. Observations from the initial seven surface fires (2000-2001) ignited under a range of burning conditions quantified the different fuel consumption and fire behavior characteristics (e.g., rate of spread, fireline intensity, etc.) possible in this particular forest fuel type. Experimental results and dendrochronological study of local fire history both support the dominance of local fire regimes by low to moderate-intensity surface fires. Carbon released by the experimental fires ranged from 4.8 to 15.4 t C ha^{− 1} depending on fuel conditions and fire severity. Preliminary emission data show a strong correlation between carbon dioxide (CO₂) and carbon monoxide (CO) emissions, which should facilitate accurate estimates of fire impacts on atmospheric chemistry. Carbon concentration in smoke samples was related to fire severity. The short landscape-scale fire-return interval (50 years), combined with typically low fire severity, in pine ecosystems of central Siberia is often associated with low tree mortality and relatively rapid buildup of litter and understory fuels after a fire.     

Estimating emissions from crop residue open burning in China based on statistics and MODIS fire products

With the objective of reducing the large uncertainties in the estimations of emissions from crop residue open burning, an improved method for establishing emission inventories of crop residue open burning at a high spatial resolution of 0.25°× 0.25° and a temporal resolution of1 month was established based on the moderate resolution imaging spectroradiometer(MODIS) Thermal Anomalies/Fire Daily Level3 Global Product(MOD/MYD14A1). Agriculture mechanization ratios and regional crop-specific grain-to-straw ratios were introduced to improve the accuracy of related activity data. Locally observed emission factors were used to calculate the primary pollutant emissions. MODIS satellite data were modified by combining them with county-level agricultural statistical data, which reduced the influence of missing fire counts caused by their small size and cloud cover. The annual emissions of CO_2, CO, CH_4,nonmethane volatile organic compounds(NMVOCs), N_2O, NO_x, NH_3, SO_2, fine particles(PM2.5),organic carbon(OC), and black carbon(BC) were 150.40, 6.70, 0.51, 0.88, 0.01, 0.13, 0.07, 0.43,1.09, 0.34, and 0.06 Tg, respectively, in 2012. Crop residue open burning emissions displayed typical seasonal and spatial variation. The highest emission regions were the Yellow-Huai River and Yangtse-Huai River areas, and the monthly emissions were highest in June(37%).Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of within ±126% for N_2O to a high of within ± 169% for NH_3.     

生物炭添加对半干旱地区土壤温室气体排放的影响

为确定生物炭添加对半干旱地区农田土壤温室气体释放的影响,采用小区定位试验,利用锯末(J)和槐树皮(H)及3种添加比例(1%、3%、5%,质量百分比),研究了生物炭添加6个月内表层土壤CO2、CH4和N2O等3种温室气体排放的动态变化.结果表明,与对照相比,各处理土壤CO2排放通量随生物炭的添加呈现增加的趋势,锯末和槐树皮等两种生物炭处理的土壤CO2平均排放通量分别增加了1.89%和3.34%,但差异不显著.CH4排放随着生物炭添加量的增加而降低,各生物炭处理的土壤表层CH4排放量平均降幅分别为:J1:1.17%、J3:2.55%、J5:4.32%、H1:2.35%、H3:5.83%、H5:7.32%.其中,锯末生物炭仅在5%添加量时较对照差异显著(P0.05),而槐树皮生物炭处理在3%和5%的添加量与对照差异均达显著水平(P0.05).生物炭对N2O的排放影响没有明显规律性.研究表明,生物炭在短期内对半干旱地区农田土壤CO2和N2O的排放没有显著影响,而对CH4排放则影响显著(P0.05).就生物炭类型而言,槐树皮生物炭在抑制CH4排放方面优于锯末生物炭,差异显著(P=0.048).     

中国城镇污水处理厂温室气体排放时空分布特征

城镇污水处理厂由于运行过程中能够大量产生二氧化碳(CO_2)、甲烷(CH_4)和氧化亚氮(N_2O),而被视为重要的人为温室气体释放源.采用基于污染物削减量的排放因子法建立了2014年中国城镇污水处理厂温室气体(CO_2、CH_4和N_2O)排放清单,并分析温室气体排放的时空分布和影响因素.结果表明,2014年中国城镇污水处理厂温室气体排放总量(以CO_2-eq计)为7 348.60 Gg,CO_2、CH_4和N_2O排放量分别为6 054.57 Gg、27.47 Gg(769.08 Gg,以CO_2-eq计)和1.98 Gg(524.95 Gg,以CO_2-eq计);各省份间排放量差异明显,华东地区排放量较高,西北地区排放量较低,西藏几乎没有排放,2005~2014年这10年间中国通过城镇污水处理厂排放的温室气体总量增长了229.4%,CO_2、CH_4和N_2O的涨幅分别为217.9%、217.9%和520.3%;地区经济的发展水平和污水处理量与当地城镇污水厂温室气体释放量相关性最大,人均蛋白质供应量与城镇污水厂N_2O产生量密切相关.     

Responses of greenhouse gas fluxes to experimental warming in wheat season under conventional tillage and no-tillage fields

Understanding the effects of warming on greenhouse gas(GHG, such as N_2O, CH_4 and CO_2 )feedbacks to climate change represents the major environmental issue. However, little information is available on how warming effects on GHG fluxes in farmland of North China Plain(NCP). An infrared warming simulation experiment was used to assess the responses of N_2O, CH_4 and CO_2 to warming in wheat season of 2012–2014 from conventional tillage(CT) and no-tillage(NT) systems. The results showed that warming increased cumulative N_2O emission by 7.7% in CT but decreased it by 9.7% in NT fields(p 0.05). Cumulative CH_4 uptake and CO_2 emission were increased by 28.7%–51.7% and 6.3%–15.9% in both two tillage systems,respectively(p 0.05). The stepwise regressions relationship between GHG fluxes and soil temperature and soil moisture indicated that the supply soil moisture due to irrigation and precipitation would enhance the positive warming effects on GHG fluxes in two wheat seasons.However, in 2013, the long-term drought stress due to infrared warming and less precipitation decreased N_2O and CO_2 emission in warmed treatments. In contrast, warming during this time increased CH_4 emission from deep soil depth. Across two years wheat seasons, warming significantly decreased by 30.3% and 63.9% sustained-flux global warming potential(SGWP) of N_2O and CH_4 expressed as CO_2 equivalent in CT and NT fields, respectively. However, increase in soil CO_2 emission indicated that future warming projection might provide positive feedback between soil C release and global warming in NCP.     

Greenhouse gas emission factors for land use and land-use change in Southeast Asian peatlands

Tropical peat swamp forests, which are predominantly located in Southeast Asia (SEA) and play a prominent role as a global carbon store, are being intensively degraded and converted to agricultural lands and tree plantations. For national inventories, updated estimates of peat emissions of greenhouse gases (GHG) from land use (LU) and land-use change in the tropics are required. In this context, we reviewed the scientific literature and calculated emission factors of peat net emissions of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in seven representative LU categories for SEA i.e. intact peat swamp forest, degraded forest (logged, drained and affected by fire), mixed croplands and shrublands, rice fields, oil palm, Acacia crassicarpa and sago palm plantations. Peat net CO₂ uptake from or emissions to the atmosphere were assessed using a mass balance approach. The balance included main peat C inputs through litterfall and root mortality and outputs via organic matter mineralization and dissolved organic carbon. Peat net CO₂ loss rate from degraded forest, croplands and shrublands, rice fields, oil palm, A. crassicarpa and sago palm plantations amounted to 19.4?±?9.4, 41.0?±?6.7, 25.6?±?11.5, 29.9?±?10.6, 71.8?±?12.7 and 5.2?±?5.1 Mg CO₂ ha^?1 y^?1, respectively. Total peat GHG losses amounted to 20.9?±?9.4, 43.8?±?6.8, 36.1?±?12.9, 30.4?±?10.6, 72?±?12.8 and 8.6?±?5.3 Mg CO₂-equivalent ha^?1 y^?1 in the same LU categories, respectively. A single land-clearing fire would result in additional emissions of 493.6?±?156.0 Mg CO₂-equivalent ha^?1.     

On-line CO, CO2 emissions evaluation and (benzene, toluene, xylene) determination from experimental burn of tropical biomass

Atmospheric pollution and global warming issues are increasingly becoming major environmental concerns. Fire is one of the significant sources of pollutant gases released into the atmosphere; and tropical biomass fires, which are of particular interest in this study, contribute greatly to the global budget of CO and CO₂. This pioneer research simulates the natural biomass burning strategy in Malaysia using an experimental burning facility. The investigation was conducted on the emissions (CO₂, CO, and Benzene, Toluene, Ethylbenzene, Xylenes (BTEX)) from ten tropical biomass species. The selected species represent the major tropical forests that are frequently subjected to dry forest fire incidents. An experimental burning facility equipped with an on-line gas analyzer was employed to determine the burning emissions. The major emission factors were found to vary among the species, and the specific results were as follows. The moisture content of a particular biomass greatly influenced its emission pattern. The smoke analysis results revealed the existence of BTEX, which were sampled from a combustion chamber by enrichment traps aided with a universal gas sampler. The BTEX were determined by organic solvent extraction followed by GC/MS quantification, the results of which suggested that the biomass burning emission factor contributed significant amounts of benzene, toluene, and m,p-xylene. The modified combustion efficiency (MCE) changed in response to changes in the sample moisture content. Therefore, this study concluded that the emission of some pollutants mainly depends on the burning phase and sample moisture content of the biomass.     

中国地区生物质燃烧释放的含碳痕量气体

为了研究中国地区生物质燃烧不同阶段释放的各种妆胆气体排放比与排放因子，建立了动态与静态燃烧室以及ＣＨ４、ＣＯＳ、ＣＯ、及ＣＯ２的采样、富集、分析方法；然后对典型乔木、灌木与草的地上部分生物质进行规模不同的燃烧实验，测得痕量 排放比和排放因子，根据全国森林生态系统碳贮量的估计及火灾统计资料，初步测算了中国地区生物质向大气中释放含碳痕量气体量。     

Improving the quality of national greenhouse gas inventories

This paper summarises the findings of an Intergovernmental Panel on Climate Change (IPCC) Expert Meeting on Methods for the Assessment of Inventory Data Quality held in Bilthoven, The Netherlands, 5–7 November 1997. Under the Kyoto Protocol of the Climate Convention, reliable inventories of national greenhouse gases (GHG) are needed for verifying compliance. Four approaches are suggested for assessing and improving the quality of greenhouse gas inventories: inventory quality assurance; inventory comparisons; model comparisons; and direct emission measurements. The paper presents recommendations for improving the quality of emission estimates of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O).     

Response of gaseous carbon emissions to low-level salinity increase in tidal marsh ecosystem of the Min River estuary, southeastern China

Although estuarine tidal marshes are important contributors to the emission of greenhouse gases into the atmosphere, the relationship between carbon dioxide(CO_2), methane(CH_4)emission, and environmental factors, with respect to estuarine marshes, has not been clarified thoroughly. This study investigated the crucial factors controlling the emission of CO_2 and CH_4from a freshwater marsh and a brackish marsh located in a subtropical estuary in southeastern China, as well as their magnitude. The duration of the study period was November 2013 to October 2014. Relevant to both the field and incubation experiments, the CO_2 and CH_4emissions from the two marshes showed pronounced seasonal variations. The CO_2 and CH_4emissions from both marshes demonstrated significant positive correlations with the air/soil temperature(p 0.01), but negative correlations with the soil electrical conductivity and the pore water/tide water Cl-and SO_4~(2-)(p 0.01). The results indicate no significant difference in the CO_2 emissions between the freshwater and brackish marshes in the subtropical estuary, whereas there was a difference in the CH_4 emissions between the two sites(p 0.01). Although future sea-level rise and saltwater intrusion could reduce the CH_4 emissions from the estuarine freshwater marshes, these factors had little effect on the CO_2 emissions with respect to an increase in salinity of less than 5‰. The findings of this study could have important implications for estimating the global warming contributions of estuarine marshes along differing salinity gradients.     

笼养肉鸡生长过程NH3、N2 O、CH4和CO2的排放

为确定规模化笼养肉鸡生产过程NH3、N2O、CH4和CO2的排放因子,并探讨不同生长阶段排放特征,本研究选择山东某商业化肉鸡养殖场,利用INNOVA 1312多气体分析仪-连续采样测试系统和风机风量现场测定系统(FANS),对肉鸡舍NH3、N2O、CH4和CO2的排放进行为期42 d的测定,确定了肉鸡整个生产过程气体的平均排放因子和累积排放因子.结果表明,整个肉鸡生产过程中NH3排放因子呈现出先升高后降低的趋势,变化范围在8.5～342.1 mg·(d·bird)-1,平均为137.9mg·(d·bird)-1[48.6 g·(d.AU)-1],CH4和CO2排放因子随着日龄的增加而增大,CH4排放因子的变化范围在19.5～351.9mg·(d·bird)-1之间,平均为154.5 mg·(d·bird)-1[54.4 g·(d.AU)-1],CO2的排放因子在2.2～152.9 g·(d·bird)-1之间变化,平均为65.9 g·(d·bird)-1[23.2 kg·(d.AU)-1],整个生产过程没有监测到N2O的排放;肉鸡的NH3累计排放因子为(5.65±1.02)g·(bird·life cycle)-1,第1阶段(0～17 d)、第2阶段(18～27 d)和第3生长阶段(28～42 d)氨气排放占总排放的比例分别为33.6%、36.4%和29.9%,第2阶段的NH3累计排放因子显著高于第1和第3生长阶段;CH4和CO2的累计排放因子分别为(6.30±0.16)g·(bird·life cycle)-1和(2.68±0.18)kg·(bird·life cycle)-1,第3阶段的CH4和CO2累计排放因子显著大于1和2阶段,占总排放量的50%以上.研究结果为控制气体排放提供了数据基础.     

Sectoral emission inventories of greenhouse gases for 1990 on a per country basis as well as on 1°×1°

A set of global greenhouse gas emission inventories has been compiled per source category for the 1990 annual emissions of the direct greenhouse gases CO₂, CH₄ and N₂O, as well as of the indirect greenhouse gases (ozone precursors) CO, NO_x and NMVOC, and of SO₂. The inventories are available by sector, both on a per country/region basis and on a 1°×1° grid. Developed by TNO and RIVM for constructing the Emission Database for Global Atmospheric Research (EDGAR) Version 2.0, in co-operation with the Global Emission Inventory Activity (GEIA) of IGAC/IGBP, the inventories meet the needs of both policy-makers and atmospheric modellers. The data sources for activity data, emission factors and grid maps are discussed with the focus on anthropogenic sources of primarily CO₂, CH₄ and N₂O. The estimates of a standard group of anthropogenic sources are presented for each compound per world region.     

北京上甸子站气相色谱法大气CH4和CO在线观测方法研究

参照瓦里关全球大气本底站气相色谱在线观测系统的设计,通过系统调试、测试和参数优化,于2009年在北京上甸子区域大气本底站建立了高精度气相色谱法大气CH4和CO在线观测系统.该系统对CH4和CO的测量精度分别优于0.03%和0.45%,达到世界气象组织全球大气观测计划(WMO/GAW)的质量目标.研究建立了与该系统配套的标气选取方法及运行序列:选取可基本涵盖该站大气CH4和CO浓度范围的2瓶标气作为工作标气,其中CH4浓度分别为2 007.1×10-9、1 809.5×10-9(摩尔分数,下同),CO浓度分别为405.6×10-9、123.8×10-9,在高低浓度工作标气之间穿插分析3次大气样品,能够保证测量的准确度(观测浓度的标准偏差CH4<1.7×10-9、CO<1×10-9),同时可最大程度地节省工作标气.该方法已应用于华北地区本底大气CH4和CO的高精度连续观测.     

基于MODIS影像估算中国大陆区域草地火污染物时空格局

草地火是草地生态系统重要干扰因子,对草地生态系统结构和功能有重要影响.草地火释放的大量烟气和颗粒物对大气环境、生态系统和人类健康有重要影响.本研究基于2001—2017年中国大陆区域MODIS-MCD64A1数据,结合生物质密度,估算各区域草地火燃烧生物量.并运用排放因子法,估算17年间中国大陆区域草地火排放污染物总量.研究结果表明,中国大陆地区草地生物质密度存在差异,由东向西逐渐递减.草地火时空分布不均衡且存在明显季节性差异,主要集中在3月和9月.中国大陆地区2001—2017年草地火次数、火面积和燃烧总量分别是1.63×10~5次、6.12×10~6 hm~2和23.86 Mt,排放CO_2、CO、CH_4、SO_2、NMVOC、NO_x、PM_(2.5)、BC、OC和TC总量分别为37.27 Mt、1.31 Mt、43.30 kt、11.05 kt、287.74 kt、79.60 kt、155.82 kt、9.25 kt、64.95 kt和75.54 kt.此外,各污染物在时间和空间上不均衡,在东北、华北、华中和西南区域呈增加趋势,华东和西北区域呈降低趋势,华南区域呈显著降低趋势.本研究揭示了中国大陆地区草地火释放污染物的时空变化,为深入揭示草地火对区域环境影响提供数据支持.     

Perturbations to tropospheric oxidants, 1985–2035: 2. Calculations of hydrogen peroxide in chemically coherent regions

Increasing global emissions of trace gases NO, CH₄, and CO, along with perturbations initiated by changes in stratospheric O₃ and H₂O, may cause tropospheric hydrogen peroxide (H₂O₂) levels to change. Specific scenarios of CH₄CONO emissions and global climate changes are used to predict HO₂ and H₂O₂ changes from 1985 to 2035 in a one-dimensional model that simulates different chemically coherent regions (e.g. urban, non-urban continental and marine mid-latitudes; marine and continental low latitudes).If CH₄ and CO emissions continue to increase throughout the troposphere at current rates (1% yr⁻), there will be large increases in H₂O₂, for example, more than 100% in the urban boundary layer from 1985 to 2035. Globally, H₂O₂ will increase 22% with HO₂ increasing 8% and O₃ increasing 13%. When CH₄, CO and NO emissions are specified on a regionally varying basis and are parameterized for high and low potential growth rates, globally averaged increases in surface concentrations are 12% for H₂O₂ and 18% for O₃. A global warming (with increased H₂O vapor) or stratospheric O₃ depletion superimposed on CH₄, CO and NO emissions changes will cut O₃ increases but add to peroxide, increasing levels as much as 150% above present day in some regions.Both globally uniform and region-specific scenarios predict a 10–15% loss in global OH from 1985 to 2035. Thus, conversion of OH to HO₂ and H₂O₂ in the atmosphere may signify a loss of gaseous oxidizing capacity in the atmosphere and an increase in aqueous-phase oxidizing capacity.     

Quantification of carbon dioxide and methane emissions in urban areas: source apportionment based on atmospheric observations

Anthropogenic emissions of carbon dioxide (CO₂) and methane (CH₄) in the atmosphere constitute an important component of the related carbon budget. The main source of anthropogenic CO₂ is burning of fossil fuels, especially in densely populated areas. Similar emissions of CH₄ are associated with the agricultural sector, coal mining, and other human activities, such as waste management and storage and natural gas networks supplying methane to large urban, industrial centers. We discuss several methods aimed at characterizing and quantifying atmospheric loads and fluxes of CO₂ and CH₄ in Krakow, the second largest city in Poland. The methods are based on atmospheric observations of mixing ratios as well as isotopic composition of the investigated gases. Atmospheric mixing ratios of CO₂ and CH₄ were measured using gas chromatography (GC) and cavity ring-down spectroscopy (CRDS). The isotopic composition of CO₂ and CH₄ was analyzed using isotope ratio mass spectrometry (IRMS), accelerator mass spectrometry (AMS), and CRDS techniques. These data, combined with auxiliary information characterizing the intensity of vertical mixing in the lower atmosphere (height of the nocturnal boundary layer [NBL] and atmospheric ²²²Rn concentration), were further used to quantify emission rates of CO₂ and CH₄ in the urban atmosphere of Krakow. These methods provide an efficient way of quantifying surface emissions of major greenhouse gases originating from distributed sources, thus complementing the widely used bottom-up methodology based on emission statistics.

     

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.