青海南部高原积雪期与生长季高寒草甸土壤CO2、CH4和N2O通量的观测

以静态箱采集气体和气相色谱分析气体浓度方法,测定分析了青海南部高原积雪期和生长季高寒草甸土壤CO_2、CH_4和N_2O通量.结果表明在积雪集中期的3月3日和4日,积雪深度为9~10 cm时,土壤CO_2通量为1.33 g·(m~2·h)-1、N_2O通量为0.21 mg·(m~2·h)-1、CH_4通量为-0.19 mg·(m~2·h)-1;在积雪末期的4月30日,积雪深度在8~9 cm时,土壤CO_2通量为4.70 g·(m~2·h)~(-1)、N_2O通量为0.24 mg·(m~2·h)-1、CH_4通量为-1.23 mg·(m~2·h)-1;积雪深度小于4 cm时,土壤CO_2和N_2O通量较低或为负值,土壤CH_4通量为负值且绝对值较小.土壤CO_2和N_2O通量与积雪深度呈正相关、土壤CH_4通量与积雪深度呈负相关(P0.05),土壤CO_2与CH_4通量及CH_4与N_2O通量间呈负相关、土壤CO_2与N_2O通量间呈正相关.土壤CO_2和N_2O通量在生长季较高、在积雪末期其次、在积雪集中期较低;土壤CH_4通量为负值,其绝对值在生长季和积雪末期较大.结果说明积雪改变将影响青藏高原高寒草甸土壤温室气体通量.     

施用不同污泥堆肥品对土壤温室气体排放的影响

通过田间试验,分别施加两种不同的污泥堆肥品（A：含生物质炭堆肥品,B：不含生物质炭堆肥品）和不同施肥量,分析土壤CO₂、CH₄和N₂O动态变化特征和排放系数,研究施用污泥堆肥品对土壤温室气体排放的影响.结果表明,土壤CO₂和CH₄排放主要集中在生长期,生物质炭堆肥品低施用量能减少CO₂排放,而高施肥量增加CO₂排放.CH₄排放主要为负值,总体表现为土壤吸收CH₄,对照处理吸收量远高于其他处理（P<0.01）,A组处理CH₄吸收量随施肥量的增加而增加（P<0.05）.N₂O排放集中在发芽期和幼苗期,施肥量越高,排放量越大（P<0.01）.污泥堆肥品农用过程排放的温室气体主要是N₂O,施用A、B两种污泥堆肥品的土壤N₂O排放系数分别为1.02%~1.90%和1.28%~2.93%.生物质炭堆肥品具有显著的碳减排效果,其温室气体排放量比不含生物质炭堆肥品的土壤低19.49%~35.56%,且对于N₂O的减排效果较CH₄更为显著.     

快速城市化区河流温室气体排放的时空特征及驱动因素

河流是大气温室气体重要的排放源,近十多年来全球城市化导致河流生态系统各要素发生改变,对河流水体温室气体排放产生影响.为研究快速城市化区不同土地利用方式下河流温室气体排放的时空特征及其影响因素,采用薄边界层模型法,于2014年9月(秋季)和12月(冬季)及2015年3月(春季)和6月(夏季)的晴天对重庆市区内梁滩河干、支流水体pCO_2、CH_4、N_2O溶存浓度进行监测.结果表明,梁滩河干、支流水体pCO_2范围为(23. 38±34. 89)～(1395. 33±55. 45) Pa、CH_4溶存浓度范围(65. 09±28. 09)～(6 021. 36±94. 36) nmol·L~(-1)、N_2O溶存浓度范围为(29. 47±5. 16)～(510. 28±18. 34)nmol·L~(-1); CO_2、CH_4和N_2O排放通量分别为-6. 1～786. 9、0. 31～27. 62和0. 06～1. 08 mmol·(m~2·d)~(-1);流域水体温室气体浓度空间格局与快速城市化带来的污染负荷空间梯度吻合,干流温室气体浓度与通量从上游向下游均呈先增加后降低,在城市化速度最快的中游出现峰值,其中城市河段CO_2和CH_4浓度约为非城市河段的2倍,同时支流水体自上游农业区向下游城市区呈显著增加;由于受到降雨、温度、外源输入的综合影响,河流CO_2排放通量呈秋季冬季夏季春季的季节模式,CH_4排放通量春季最高夏季最低,N_2O排放通量季节差异不显著.流域水体碳、氮含量均较高,水体CO_2的产生和排放不受生源要素限制,但受水温、pH、DO、叶绿素a等生物代谢因子影响; CH_4的产生和排放受水体碳、氮、磷含量和外源污水输入的共同驱动; N_2O的产生和排放主要受高N_2O浓度的城市污水排放影响.本研究认为流域快速城市化加快了河流水体温室气体排放,形成排放热源,因此城市河流温室气体排放对全球河流排放通量的贡献可能被忽视,在未来研究中应受到更多关注.     

不同干扰强度下三江平原湿地土壤温室气体排放对冻融作用的响应

为评估季节性冻融作用对不同干扰强度湿地温室气体产生机制的影响,采用静态箱/气相色谱法,原位观测三江平原洪河国家自然保护区内未受干扰的常年积水的小叶章湿地(undisturbed Deyeuxia angustifolia wetland,UDAW)、保护区外受人类活动干扰导致湿地含水量减少的季节性积水的小叶章湿地(disturbed Deyeuxia angustifolia wetland,DDAW)以及由小叶章湿地开垦10年以上的水稻田(rice paddy,RP)的温室气体排放通量,分析季节性冻融作用对3种湿地温室气体排放的影响特征.结果表明:3种湿地在冻融期均有CO₂和CH₄排放,且在春季冻融初期CO₂和CH₄均出现短期的高排放现象,随着冻融温度升高,温室气体排放通量均逐渐增加.其中,CO₂排放通量表现为UDAW > DDAW > RP,CH₄排放通量却表现为DDAW > RP > UDAW;DDAW的CH₄排放速率与冻融温度的相关性最高(P < 0.01,R2=0.647 5),UDAW中二者的相关性最低(P < 0.01,R2=0.424 7).相关性分析显示,DDAW和RP土壤中CO₂与CH₄的排放通量均呈正相关(P均小于0.01,R2分别为0.749 1、0.574 4),而UDAW土壤中CO₂与CH₄的排放通量表现为弱相关(P < 0.05,R2=0.303 8),可见冻融温度会影响CO₂和CH₄的排放通量.季节性冻融作用影响了3种湿地土壤N₂O的排放通量,秋季冻融期UDAW和DDAW表现为N₂O的汇,而在春季冻融期3种湿地均表现为N₂O的源,表明不同干扰湿地N₂O的排放通量对冻融作用的响应不同,但均随土壤温度的升高其排放通量不断增加.研究显示,三江平原的冻融作用降低了湿地温室气体排放,干扰强度越大,冻融作用影响越小,且秋季冻融作用大于春季.      

模拟潮汐和植被对湿地温室气体通量的影响研究

以福建省九龙江入海口的滩涂潮间带作为研究对象,通过原位采样和室内人工微宇宙实验,利用静态箱-气相色谱法,研究了潮汐植被对湿地CH₄、CO₂和N₂O 3种重要温室气体通量的影响.结果表明,3种温室气体通量在模拟潮汐和植被作用下表现出明显的差异.模拟潮汐对CH₄和N₂O通量的影响没有明显的规律,总量上都表现为排放;对CO₂通量具有显著影响,退潮时抑制,表现为吸收,涨潮时促进,表现为排放.植被促进CH₄的排放,对CO₂通量影响无明显规律,对N₂O通量表现为抑制作用.植被除了自身对温室气体直接作用外,还通过改变沉积物的理化性质影响微生物活动,进而影响温室气体通量.综合分析,植被对温室气体通量的影响要比模拟潮汐作用明显.     

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.     

不同施氮处理下旱作农田土壤CH_4、N_2O气体排放特征研究

依托甘肃农业大学布设在定西市李家堡镇的长期施氮定位实验,对不同施氮农田CH4和N2O气体通量,采用静态箱-气相色谱法进行小麦生育期的连续观测,并对影响通量变化的环境因子同期观测.结果表明:5个施氮处理下(0、52.5、105、157.5、210 kg·hm-2),旱作农田土壤在小麦全生育期内表现为CH4累积通量的汇和N2O累积通量的源;且不施氮处理时,CH4累积吸收通量最大;施氮量为210 kg·hm-2时,土壤CH4的累积吸收通量所受抑制最大,即土壤CH4累积吸收通量随施氮量升高而降低.相反,不施氮处理时,土壤N2O的累积排放通量最小,施氮量为210 kg·hm-2时,土壤N2O的累积排放通量最大,土壤N2O累积排放通量随施氮量的增加而增大.综合分析,施氮量增大会抑制全生育期旱作春小麦田土壤CH4吸收通量,提高土壤N2O的排放通量.因此,合理控制施氮量有利于生育期旱作农田土壤减排.CH4平均吸收通量随土壤温度的升高而降低,随土壤水分的升高而升高;相反,N2O平均排放通量随土壤温度的升高而升高,随土壤水分的升高而降低.5~10 cm层次的土壤温度与CH4平均吸收通量呈极显著线性负相关,与N2O平均排放通量呈显著正相关.5~10 cm层次的土壤水分与CH4平均吸收通量呈极显著线性正相关,与N2O平均排放通量呈显著负相关.     

施用畜禽粪便堆肥品的蔬菜地CH4、N2O和NH3排放特征

农田是重要的温室气体排放来源之一,其中蔬菜地的温室气体排放日益受到人们关注.以北京市郊某温室种植的油麦菜地为研究对象,通过大棚试验,考察和比较了油麦菜地施用不同类型畜禽粪便堆肥产品的CH4、N2O和NH3排放特征及其影响因素.结果表明,油麦菜地NRM、RM、CF处理的CH4排放系数分别为0.2%、0.027%、0.004%;N2O排放系数分别为0.18%、0.63%、0.74%;NH3排放系数分别为2.00%、3.98%、2.53%.CH4排放通量与土壤温度和地表湿度相关,N2O排放通量与土壤温度、地表温度和湿度相关,CH4、N2O和NH3排放通量均受土壤含水率影响,而温室中的气温不是影响CH4、N2O和NH3排放的主要因素.     

秸秆与化肥减量配施对菜地土壤温室气体排放的影响

采用静态箱/气相色谱法,2016年11月至2017年9月通过田间原位试验,设置了无物料还田(CK)、常规化肥(F)、秸秆还田配施100%化肥(100FS)、秸秆还田配施70%化肥(70FS)、秸秆还田配施60%化肥(60FS)、秸秆还田配施50%化肥(50FS),对比分析了在化肥减量的基础上,配施秸秆处理的菜地(莴笋-卷心菜-辣椒轮作)土壤CO_2、CH_4、N_2O动态变化特征及温室效应,研究秸秆与化肥减量配施对菜地温室气体排放的影响.结果表明,土壤CO_2、CH_4、N_2O排放具有一定的季节变化规律,排放高峰主要集中在4~8月,且在施肥灌水后均会出现气体的排放峰.秸秆与化肥配施较常规施肥(F)处理提高了土壤N_2O排放量,累积排放量及其排放系数,其中100FS处理的效果最为明显,辣椒季的累积排放通量明显高于莴笋季和卷心菜季,高达60.76 kg·hm~(-2)(P0.05),N_2O的排放系数(以N_2O-N/N计)为0.138 kg·kg-1,而秸秆与化肥减量配施较100FS处理可以降低氮肥的N_2O排放系数.与对照CK和F处理相比,70FS处理降低了土壤CO_2排放量和累积排放量,分别为55.28~1 831.62 mg·(m2·h)-1和7 502.13~25 988.55 kg·hm~(-2),而其他秸秆与化肥配施处理均增加了CO_2累积排放通量,尤其是60FS和50FS处理.对土壤CH_4排放而言,辣椒季的排放波动较大,除CK外,各处理的土壤CH_4累积排放量多为负值,表现为大气中CH_4汇;秸秆与化肥减量30%~50%配施处理均降低了辣椒季的土壤CH_4排放量和累积排放通量,而100FS处理提高了CH_4排放量和累积排放通量.与CK和F处理相比,除70FS外,100FS、60FS和50FS均显著提高了GWP.总体上,从温室气体排放角度,在常规化肥施用的基础上减量30%再与秸秆配施可以降低土壤CO_2和CH_4排放,缓解温室气体的增温潜势,而对土壤N_2O减排效果不显著.     

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.     

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.     

炉渣与生物炭施加对稻田温室气体排放及其相关微生物影响

为了减少稻田温室气体排放通量,本研究对稻田土壤进行炉渣和生物炭单一施加和混合施加处理,并测定了早、晚稻拔节期和乳熟期CO_2、CH_4和N_2O排放通量及相关微生物(细菌、真菌、硝化细菌、反硝化细菌)的数量.结果表明,稻田施加废弃物可以减少温室气体的排放通量.在早、晚稻的拔节期,施加生物炭显著降低了CO_2和N_2O的排放通量(p0.05),混合施加显著降低了CO_2和CH_4的排放通量(p0.05),施加炉渣条件下3种温室气体的排放通量与对照组相比没有差异.施加炉渣或生物炭都显著降低硝化细菌的数量(p0.05),混施处理显著降低细菌、硝化细菌、反硝化细菌数量(p0.05),但显著提高了稻田土壤真菌/细菌比值(p0.05).在早、晚稻的乳熟期,炉渣、生物炭、混施处理能显著降低CH_4排放通量(p0.05),而生物炭处理显著降低N_2O排放通量(p0.05).炉渣处理显著降低细菌、硝化细菌、反硝化细菌数量(p0.05),生物炭处理显著降低细菌、反硝化细菌数量(p0.05),混施处理显著降低细菌、硝化细菌数量,并显著提高真菌/细菌比值(p0.05).温室气体排放与微生物数量之间的相关性分析结果表明,CO_2、CH_4排放通量与细菌数量呈显著正相关,与真菌/细菌比值呈显著负相关;而N_2O排放通量则与硝化细菌、反硝化细菌数量呈显著正相关.     

河口潮滩湿地CH4、CO2排放通量对氮硫负荷增强的响应

以闽江河口区高、中潮滩短叶茳芏湿地为研究对象,于2014年6—11月植物生长季进行氮硫负荷增强实验,利用静态箱-气象色谱法测定土壤CH_4、CO_2排放通量,并同步观测相关环境因子.结果表明,氮硫负荷增强对潮滩湿地CH_4、CO_2排放通量的影响不尽一致.与对照相比,NH_4~+-N输入使高、中潮滩CH4排放通量分别提高了(107.53%,7.19%),使高潮滩CO_2排放通量增加了3.39%,中潮滩减少了3.00%;NO_3~--N输入使高潮滩CH4、CO_2排放通量分别增加了(29.99%,16.99%),使中潮滩分别减少了(3.45%,4.77%);SO_4~(2-)-S输入使高、中潮滩CH4排放通量分别减少了(8.99%,7.67%),使高潮滩CO_2排放通量减少了3.87%,中潮滩增加了5.44%;N-S复合输入使高、中潮滩CH4排放通量分别提高了(72.48%,25.66%),CO_2排放通量提高了(13.32%,13.48%).氮硫负荷增强改变了短叶茳芏沼泽生长季CH_4、CO_2排放通量变化规律,但除了NH+4-N处理对高潮滩CH4通量的影响显著外,其他处理影响均未达到显著性水平.相关分析显示,高、中潮滩湿地CH_4、CO_2排放通量与土壤温度,含水率具有显著的正线性相关关系,与土壤电导率相关性不显著.在全球环境问题日益严重背景下,系统研究湿地生态系统温室气体排放的机制与规律,对于准确估算全球温室气体排放量具有重要而直接的意义.     

盐碱区不同开发年限水田温室气体排放规律及影响因素

以吉林省前郭盐碱水田区为研究对象,采用野外采样和小区试验相结合的方法,监测水稻生长期土壤温室气体(CH4和N2O)排放、土壤p H和土壤有机碳(SOC)变化,分析水田温室气体排放规律及其影响因素.结果表明,水田N2O排放季节变化特征明显并呈现3个峰值,肥料的施入提供了更多的反应底物,对水田N2O的排放量影响显著.在淹水条件下,N2O的主要来源于反硝化过程,而排水后,硝化作用则占据了主导地位.CH4排放呈现单峰,在水稻生长旺盛的分蘖期,稻田较深水层以还原环境为主,为产生CH4的微生物提供了适宜的条件,进而导致CH4排放呈高峰值;土壤p H对N2O和CH4排放的影响不明显,但土壤SOC含量与CH4的排放规律呈现显著正相关.     

闽江河口短叶茳芏湿地CH4和N2 O排放对氮输入的短期响应

利用静态箱-气相色谱法,研究了氮输入对闽江河口短叶茳芏湿地CH4和N2O排放通量的短期影响.结果表明,高氮输入在不同采样时间均促进了湿地CH4排放,低氮输入在不同时间则具有不同的变化特征.与对照处理相比,低氮和高氮2种处理分别使湿地CH4排放通量增加了-44.35%～1 057.35%和7.15%～667.37%.外源氮输入在24 h内对湿地N2O排放通量具有明显的正激发效应,最高可增加171.60倍和177.79倍,但在8 d后,氮输入对湿地N2O排放的激发效应减弱甚至消失.氮输入在短时间内对湿地土壤Ec、pH和Eh均未产生显著影响.湿地CH4排放通量在对照处理下仅与5 cm Eh存在显著负相关,在低氮处理下仅与10 cm地温呈显著负相关,在高氮处理下则与5 cm Ec、0、5 cm pH以及0、5、10 cm土壤Eh均呈显著相关性,而N2O排放通量在不同处理下与湿地气温、地温、盐度、pH和Eh等环境因子均不存在显著相关性.研究表明,探讨氮输入对湿地温室气体排放的影响应考虑其时间变异性.     

Methane and CO2 fluxes from an Indonesian peatland used for sago palm (Metroxylon sagu Rottb.) cultivation: Effects of fertilizer and groundwater level management

Tropical peatland is a vast potential land source for biological production, but peatland is a major natural source of greenhouse gases, especially methane (CH₄). It is important to evaluate the changes in greenhouse gas emissions induced by cultivation practices for sustainable agricultural use of tropical peatland. We investigated the effects of fertilizer application and the groundwater level on CH₄ and carbon dioxide (CO₂) fluxes in an Indonesian peat soil. The crop cultivated was sago palm (Metroxylon sagu Rottb.), which can grow on tropical peat soil without drainage and yield great amounts of starch. CH₄ emission through sago palm plants was first estimated by collecting gas samples immediately after cutting sago suckers using the closed chamber method. The CH₄ fluxes ranged from negative values to 1.0 mg C m⁻² h⁻¹. The mean CH₄ flux from treatment with macroelements (N, P, and K) and microelements (B, Cu, Fe, and Zn) applied at normal rates did not differ significantly from that of the No fertilizer treatment, although increasing the application rates of macroelements or microelements by 10-fold increased the CH₄ flux by a factor of two or three. The relationship between CH₄ flux and the groundwater table was regressed to a logarithmic equation, which indicated that to maintain a small CH₄ flux, the groundwater table should be maintained at <−45 cm. The CO₂ fluxes ranged between 24 and 150 mg C m⁻² h⁻¹, and were not significantly affected by either fertilizer treatments or the groundwater level. The inclusion of sago palm suckers in a chamber increased CH₄ emission from the peat soil significantly. Thus, gas emissions mediated by certain kinds of palm plants should not be disregarded.     

厌氧条件下砂壤水稻土N2、N2O、NO、CO2和CH4排放特征

了解厌氧条件土壤反硝化气体(N2、N2O和NO)、CO2和CH4排放特征,是认识反硝化过程机制的基础,并有助于制定合理的温室气体减排措施.定量反硝化产物组成,可为氮转化过程模型研发制定正确的关键过程参数选取方法或参数化方案.本研究选取质地相同(砂壤土)的两个水稻土为研究对象,通过添加KNO3和葡萄糖的混合溶液,将培养土壤的初始NO-3和DOC含量分别调节到50 mg·kg-1和300 mg·kg-1,采用氦环境培养-气体及碳氮底物直接同步测定方法,研究完全厌氧条件下土壤N2、N2O、NO、CO2和CH4的排放特征,并获得反硝化气态产物中各组分的比率.结果表明,在整个培养过程中,两个供试土壤的N2、N2O和NO累积排放量分别为6~8、20和15~18 mg·kg-1,这些气体排放量测定结果可回收土壤NO-3变化量的95%~98%,反硝化气态产物以N2O和NO为主,其中3种组分的比率分别为15%~19%(N2)、47%~49%(N2O)和34%~36%(NO);但反硝化气体产物组成的逐日动态均显现为从以NO为主逐渐过渡到以N2O为主,最后才发展到以N2为主.以上结果说明,反硝化气体产物组成是随反硝化进程而变化的,在以气体产物组成比率作为关键参数计算各种反硝化气体产生率或排放率的模型中,很有必要重视这一点.     

Biochar addition to agricultural soil increased CH4 uptake and water holding capacity – Results from a short-term pilot field study

Biochar addition to agricultural soil has been suggested to mitigate climate change through increased biogenic carbon storage and reduction of greenhouse gas emissions. We measured the fluxes of N₂O, CO₂, and CH₄ after adding 9 t ha^?1 biochar on an agricultural soil in Southern Finland in May 2009. We conducted these measurements twice a week for 1.5 months, between sowing and canopy closure, to capture the period of highest N₂O emissions, where the potential for mitigation would also be highest. Biochar addition increased CH₄ uptake (96% increase in the average cumulative CH₄ uptake), but no statistically significant differences were observed in the CO₂ and N₂O emissions between the biochar amended and control plots. Added biochar increased soil water holding capacity by 11%. Further studies are needed to clarify whether this may help balance fluctuations in water availability to plants in the future climate with more frequent drought periods.     

Ammonia and greenhouse gas emissions from a subtropical wheat field under different nitrogen fertilization strategies

Minimizing soil ammonia (NH₃) and nitrous oxide (N₂O) emission factors (EFs) has significant implications in regional air quality and greenhouse gas (GHG) emissions besides nitrogen (N) nutrient loss. The aim of this study was to investigate the impacts of different N fertilizer treatments of conventional urea, polymer-coated urea, ammonia sulfate, urease inhibitor (NBPT, N-(n-butyl) thiophosphoric triamide)-treated urea, and nitrification inhibitor (DCD, dicyandiamide)-treated urea on emissions of NH₃ and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH₃ emission following N fertilization was characterized using active chamber method whereas GHG emissions of N₂O, carbon dioxide (CO₂), and methane (CH₄) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH₃-N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on N₂O-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH₃-N and N₂O-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO₂-C flux but had no effect on CH₄-C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH₃ and N₂O emissions in subtropical wheat production in Southern USA.     

Methane and nitrous oxide emissions from a subtropical coastal embayment (Moreton Bay, Australia)

Surface water methane (CH₄) and nitrous oxide (N₂O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH₄ and N₂O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH₄ and N₂O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH₄ varied between 500% and 4000% saturation while N₂O varied between 128 and 255% in the two bays. Average seasonal CH₄ fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH₄/(m²·day) while N₂O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N₂O/(m²·day). Weighted emissions (t CO₂-e) were 63%-90% N₂O dominated implying that a reduction in N₂O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH₄ and N₂O and puts the estimated fluxes into the global context with measurements done from other climatic regions.