Isotopic signature of N(2)O produced by marine ammonia-oxidizing archaea

The ocean is an important global source of nitrous oxide (N(2)O), a greenhouse gas that contributes to stratospheric ozone destruction. Bacterial nitrification and denitrification are thought to be the primary sources of marine N(2)O, but the isotopic signatures of N(2)O produced by these processes are not consistent with the marine contribution to the global N(2)O budget. Based on enrichment cultures, we report that archaeal ammonia oxidation also produces N(2)O. Natural-abundance stable isotope measurements indicate that the produced N(2)O had bulk δ(15)N and δ(18)O values higher than observed for ammonia-oxidizing bacteria but similar to the δ(15)N and δ(18)O values attributed to the oceanic N(2)O source to the atmosphere. Our results suggest that ammonia-oxidizing archaea may be largely responsible for the oceanic N(2)O source.     

Nitrogen-15 and oxygen-18 characteristics of nitrous oxide: a global perspective

The global budget of N(2)O shows a significant imbalance between the known rate of destruction in the stratosphere and the estimated rates of natural and anthropogenic production in soils and the ocean. Measurements of the (15)N/(14)N and (18)O/(16)O ratios in two major tropospheric sources of N(2)O, tropical rain forest soils and fertilized soils, show that soil N(2)O from a tropical rain forest in Costa Rica and from sugar-cane fields in Maui is strongly depleted in both (15)N and (18)O relative to mean tropospheric N(2)O. A major source of heavy N(2)O, enriched in both (15)N and (18)O, must therefore be present to balance the light N(2)O from soils. One such source is the back-mixing flux of N(2)O from the stratosphere, which is enriched in (15)N and (18)O by photolysis and chemistry. However these return fluxes of (15)N and (18)O are so great that a large oceanic flux of N(2)O is required to balance the heavy isotope-enriched stratospheric flux. All these effects will be reflected in climatically related isotopic variations in trapped N(2)O in polar ice cores.     

Isotopic fractionation of stratospheric nitrous oxide

We propose an isotopic fractionation mechanism, based on photolytic destruction, to explain the 15N/14N and 18O/16O fractionation of stratospheric nitrous oxide (N2O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers 15N14N16O and 14N15N16O have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N2O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N2O in the middle atmosphere and that individual N2O isotopomers might be useful tracers of stratospheric air parcel motion.     

硝化和反硝化过程对林地和草地土壤N2O排放的贡献

【目的】明确好气条件下硝化和反硝化过程对林地和草地土壤N2O排放的贡献,比较温度变化对两个过程排放贡献的影响。【方法】通过室内好气培养试验（60%WHC）,采用15N同位素标记技术测定林地和草地土壤在10℃和15℃下铵态氮、硝态氮和N2O的15N丰度,计算硝化和反硝化过程对N2O排放的贡献。【结果】好气培养条件下,林地和草地土壤中的硝化作用和反硝化作用同时发生,硝化作用对N2O排放的贡献为53.1%―72.0%,是N2O排放的主要过程。培养期间林地土壤中反硝化过程对N2O排放的平均贡献为44.9%,显著大于草地土壤（28.9%）,而硝化过程对N2O排放的平均贡献为55.1%,显著小于草地土壤（71.1%）。温度增加显著促进了土壤中N2O的排放,但是对硝化和反硝化过程的N2O排放贡献没有影响。【结论】好气条件下硝化作用是土壤中N2O排放的主要过程,但反硝化作用仍占有很大比例。     

The 18O/16O and 17O/16O ratios in atmospheric nitrous oxide: A mass-independent anomaly

Measurements of the oxygen isotope ratios (18O/16O and 17O/16O) in atmospheric nitrous oxide (N2O) from La Jolla, Pasadena, and the White Mountain Research Station (elevation, 3801 meters) in California and the White Sands Missile Range in New Mexico show that N2O has a mass-independent composition. These data suggest the presence of a previously undefined atmospheric process. The La Jolla samples can be explained by a mixing between an atmospherically derived source of mass-independent N2O and biologically derived mass-dependent N2O. Possible origins of the mass-independent anomaly in N2O are discussed.     

不同氮钾水平及氮形态差异对土壤氨挥发和氧化亚氮排放的影响

研究不同氮钾用量下土壤氨(NH3)挥发和氧化亚氮(N2O)排放,为确定氮钾肥合理施用和大气环境保护提供理论依据。盆栽实验共9个处理:N0K0、(NO^-3-N)50K35、(NO^-3-N)50K80、(NO^-3-N)100K35、(NO^-3-N)100K80、(NH^+4-N)50K35、(NH^+4-N)50K80、(NH^+4-N)100K35、(NH^+4-N)100K80。分别采用静态箱法和通气法采集N2O和NH3。氮肥显著增大了N2O的排放通量和累积排放量以及NH3的挥发速率和累积排放量。N2O的平均排放通量和累积排放量从不施肥处理的15.8μg·m^-2·h-1和0.17 mg·kg^-1增加到氮肥用量100 mg·kg^-1时的45.6μg·m^-2·h-1和0.57 mg·kg^-1。NH3挥发速率和累积排放量在氮肥用量为100 mg·kg^-1时达到最大,分别为1.5 kg·hm^-2·d^-1和4.18 mg·kg^-1。铵态氮为氮源的各处理N2O排放通量和累积排放量以及NH3挥发速率和累积排放量均高于以硝态氮为氮源的各处理。钾肥显著增大了NH3挥发速率和累积排放量,但在低氮水平下,钾肥显著降低N2O排放通量和累积排放量。化学氮肥施用量的增加是NH3挥发和N2O排放增加的主要因素,与硝态氮肥相比,铵态氮肥更易于NH3和N2O的排放。增施钾肥显著增大土壤NH3挥发速率和排放量,但降低了土壤N2O的排放通量,显著减少了整个生长季节N2O的累积排放量。     

农田氧化亚氮排放的主要影响因素及其作用机制

氧化亚氮(N2O)的环境效应显著,研究N2O的排放机理及影响因素对减少N2O排放和改善全球环境具有重大意义.农田生态系统的生物和非生物途径均可产生N2O,是N2O的重要排放源.由于受人为干扰频繁,农田土壤中N2O的产生和排放过程受到环境和农田管理措施等多种因素影响.介绍了土壤中N2O的产生机理,重点论述了肥料施用和土壤水热状况等关键性因素影响土壤N2O产生和排放的作用机制,以期为N2O的减排策略提供依据.     

Variability in nocturnal nitrogen oxide processing and its role in regional air quality

Nitrogen oxides in the lower troposphere catalyze the photochemical production of ozone (O3) pollution during the day but react to form nitric acid, oxidize hydrocarbons, and remove O3 at night. A key nocturnal reaction is the heterogeneous hydrolysis of dinitrogen pentoxide, N2O5. We report aircraft measurements of NO3 and N2O5, which show that the N2O5 uptake coefficient, g(N2O5), on aerosol particles is highly variable and depends strongly on aerosol composition, particularly sulfate content. The results have implications for the quantification of regional-scale O3 production and suggest a stronger interaction between anthropogenic sulfur and nitrogen oxide emissions than previously recognized.     

不同氮磷肥施用对春玉米农田N2O排放的影响

农田过量施肥会增加N2O排放,使农田土壤成为重要的温室气体排放源。为减少农田N2O排放,利用自动观测系统研究了春玉米农田中不同肥料对N2O排放的影响,并结合作物产量及N2O的排放量探索减少温室气体排放的施肥措施。采用田间试验方法设定了不施肥(CK)、尿素(U)、尿素加磷肥(NP)和硝酸磷肥(NOP)4个处理进行研究。结果表明,各处理下N2O排放总量分别为:CK0.21kgN·hm-2、U1.19kgN·hm-2、NP0.93kgN·hm-2、NOP0.69kgN·hm-2;N2O排放主要受施肥、灌溉,降雨和土壤温度的影响;在作物生长后期土壤含氮量小于7mgN·kg-1的情况下,观测到土壤吸收N2O的情况;各处理下排放因子均小于政府间气候变化委员会(IPCC)的缺省值1%,表明IPCC推荐的排放因子不适用于估算中国北方的春玉米农田N2O排放。施加磷肥有助于减少农田N2O排放并提高产量,硝态磷肥较尿素可以显著减少N2O排放。综合考虑产量和N2O排放,相对于施用尿素和尿素加磷肥处理,硝酸磷肥处理不仅可节约15%和30%的肥料投入,而且分别减少42%和26%的N2O排放,具有减排不减产的良好效果。     

灌溉方式对农田N2O排放影响的研究进展

N2O是大气中对温室效应和大气臭氧层损耗有重要影响的微量气体.农田气体排放是大气中N2O的重要来源.灌溉方式能从多个方面影响农田N2O的排放.因此,追踪灌溉方式对农田N2O排放影响的研究进展,不仅可以为我国农田N2O排放机理的进一步研究提供参考,而且对我国发展低碳环保农业具有十分重要的意义.该研究简要地探讨了淹灌、无水层灌溉、天然降雨3种灌溉方式对农田土壤N2O排放的影响,并对该领域的研究做出展望.     

我国河流N2O饱和度与释放系数变化及其与河流氮水平的关系研究

通过选择我国3个不同流域的河流,研究了河流N2O饱和度与释放量的时空变化及其与河流氮水平的关系,并评估了IPCC关于河流N2O的释放系数.结果显示,河流硝态氮和氨氮的浓度变化范围分别为0.023～5.24(均值1.29±0.822)mg N·L-1和0.020～40.3(均值2.54±5.47 )mg N·L-1;相应地,河流N2O饱和度和释放量的变化范围分别为90％～8213％(均值407％±1010％)及0.250～1960(均值58.3±221)μg N·m-2·h-1.不同河流N2O饱和度均呈现明显的季节变化特征,N2O饱和度几乎持续处于过饱和状态,表明河流N2O是大气N2O的源.不同类型的河流,其氮浓度水平、N2O饱和度与释放量均有显著差异,城市纳污型河流——南淝河,其氨氮浓度、N2O饱和度和释放量显著高于其他河流,均值分别达(12.5±6.10)mg N·L-1、1760％±2620％及(363±548)μg N m-2·h-1.研究发现,除南淝河外,所有径流主导型的河流,其N2O饱和度与NO3-含量存在显著线性正相关关系,说明高NO3-含量的河流能增加N2O的表观产量.除南淝河以外的河流N2O释放系数变化范围为0.05％～0.87％,均值为0.20％,较为接近IPCC的参考值0.25％.但我们的研究建议采用修正后的河流N2O释放系数(均值为0.10％),该系数更能体现河流释放N2O的实际情况.     

Antarctic Ozone Depletion Chemistry: Reactions of N2O5 with H2O and HCl on Ice Surfaces

The reactions of dinitrogen pentoxide (N(2)O(5)) with H(2)O and hydrochloric acid (HCl) were studied on ice surfaces in a Knudsen cell flow reactor. The N(2)O(5) reacted on ice at 185 K to form condensed-phase nitric acid (HNO(3)). This reaction may provide a sink for odd nitrogen (NO(x)) during the polar winter, a requirement in nearly all models of Antarctic ozone depletion. A lower limit to the sticking coefficient, gamma, for N(2)O(5) on ice is 1 x 10(-3). Moreover, N(2)O(5) reacted on HCl-ice surfaces at 185 K, with gamma greater than 3 x 10(-3). This reaction, which produced gaseous nitryl chloride (ClNO(2)) and condensed-phase HNO(3), proceeded until all of the HCl within the ice was depleted. The ClNO(2), which did not react or condense on ice at 185 K, can be readily photolyzed in the Antarctic spring to form atomic chlorine for catalytic ozone destruction cycles. The other photolysis product, gaseous nitrogen dioxide (NO(2)), may be important in the partitioning of NO(x) between gaseous and condensed phases in the Antarctic winter.     

L-乳酸生产菌干酪乳杆菌6028液体发酵条件的研究

[目的]寻求干酪乳杆菌6028发酵产酸的最佳条件。[方法]以干酪乳杆菌6028为试验菌种,经斜面培养基、筛选培养基、种子培养基、发酵培养基培养后进行液体发酵,研究碳源、氮源、硫酸镁、磷酸氢二钾、乙酸钠、发酵温度和发酵时间对干酪乳杆菌6028 L-乳酸产量的影响。[结果]当培养基中葡萄糖、氮源、无水乙酸钠、MgSO4.7H2O含量分别为14%、3.75%、0.5%、0.02%,发酵温度为34℃、发酵时间为96 h时,L-乳酸产量最高。在此条件下,L-乳酸的产量达到97.03 g/L。[结论]干酪乳杆菌6028的最佳培养基组成为:葡萄糖、蛋白胨、牛肉膏、酵母膏、无水乙酸钠、MgSO4.7H2O、MnSO4.7H2O、碳酸钙分别为140、15、15、7.5、5、0.2、0.05、100 g/L、吐温-80 1 ml、pH值6.8。最佳发酵时间和温度分别为96 h、34℃。     

A "Green" route to adipic acid: direct oxidation of cyclohexenes with 30 percent hydrogen peroxide

Currently, the industrial production of adipic acid uses nitric acid oxidation of cyclohexanol or a cyclohexanol/cyclohexanone mixture. The nitrous oxide emission from this process measurably contributes to global warming and ozone depletion. Therefore, the development of an adipic acid production process that is less damaging to the environment is an important subject in chemical research. Cyclohexene can now be oxidized directly to colorless crystalline adipic acid with aqueous 30 percent hydrogen peroxide under organic solvent- and halide-free conditions, which could provide an ideal solution to this serious problem.     

光照对分蘖期水稻叶际及根系-培养液体系 N2O 和 NOX（NO，NO2）排放的影响

[目的]该研究探讨光照对分蘖期水稻根、叶界面N2O和NOX排放的作用及其机制。[方法]试验在水培控氮、小型光控培养箱控光和同步测定条件下,探讨了不同光质、光强及光控处理对分蘖期水稻叶际及根系-培养液体系 N2O和 NOX 排放的影响。[结果]①在相同氮源(NH4NO3-N,90 mg/L)、日间光照为6000、8000 lx条件下,分蘖期平均水稻叶际 N2O和NO排放速率分别为27.08、32.33μg/(pot·h)和0.114、0.057μg/(pot·h),分别占 N2O和 NO总排放的57.38%、58.65%和9.65%、4.52%,水稻叶际是N2O的重要排放源;②在光强(1600 lx)一致条件下,LED黄、绿、白、红、蓝光处理的平均水稻叶际N2O 排放速率分别为6.83、9.40、9.73、2.82和4.08μg/(pot·h),光 X强较高的红(3000 lx)、蓝光(2500 lx)处理能同步抑制分蘖期水稻根、叶界面N2O的挥发(P<0.01),LED红、白光有促进日间水稻叶际NO排放的作用,LED蓝光则有同步抑制水稻根、叶界面 NO挥发的作用效果,但不同光控处理下水稻根、叶界面均无明显的NO2净排放作用;③0~8000 lx 范围内随着光照增强,水稻根部NO及根、叶界面 N2O排放同步增加,但高光强(6000~8000 lx)下水稻叶际 NO排放显著大幅下降(P<0.01)。[结论]水稻根、叶界面均以N2O挥发为主;试验供氮水平下适度控制日间光强并同步增加红光、蓝光比例的技术,能同步抑制水稻根、叶界面氮氧化物的排放。     

农田氧化亚氮减排的关键是合理施氮

农业源氧化亚氮(N2O)排放量占全球人为源总排放量的2/3,是最大的人为排放源,氮肥和有机肥的施用是其主要贡献者。合理施氮是获得较高目标产量、维持土壤氮肥力和降低因施氮引起环境污染风险的关键,在减少农田土壤N2O排放、缓解温室效应中起重要作用。本文基于合理施肥的“4R”(Right amount,Right type,Right time,Right place)理念和技术,论述了施氮量与N2O排放量之间的数量关系,肥料品种、施肥时期和方法对N2O减排的影响。强调了氮素投入超过作物需氮量后,N2O排放量会呈现指数型增长;将施氮量控制在合理范围对N2O减排的重要性。建议在不同土壤-气候-作物体系下,同时开展产量、品质,氨挥发、硝酸盐淋洗、N2O排放和土壤肥力的长期系统研究,不能顾此失彼;形成同类地区能够机械操作的规范化种植模式与合理施肥措施,包括与其他农艺措施的配合,如轮作与耕作、灌溉、有机肥和秸秆还田、磷钾肥和中微量元素管理等,以实现产量、品质、效益与环境效应相协调的可持续集约化作物生产目标。     

氮磷钾配比施肥对巨尾桉叶片及根系有机酸质量分数的影响

采用正交L9(34)试验设计,研究不同氮(N)磷(P)钾(K)配比施肥下巨尾桉GL9(Eucalyptus grandis×E.urophylla)叶片、根系中有机酸种类及质量分数和根系有机酸酶活性。结果表明:叶片有机酸质量分数是根系的4.03~6.64倍;与对照(CK)相比,N3P2K1、N2P3K1的叶片有机酸质量分数分别比CK低7.44%和19.70%,其余配比均比CK高;而根系中N1P2K2、N1P3K3、N2P3K1的有机酸质量分数比CK低22.02%~31.07%,有机酸质量分数越低,表明巨尾桉的养分越均衡,肥料的元素配比越合理。叶片中苹果酸、柠檬酸、乙酸占所有酸的85.21%~95.32%,根系中苹果酸及柠檬酸占所有酸的54.99%~85.21%。相关分析表明,叶片与根系的总有机酸质量分数均与苹果酸、柠檬酸显著相关(p0.05),这两种酸作为巨尾桉的优势酸,可能是植物遭受养分胁迫的指示型酸;而有机酸酶PEPC、NAD-IDH酶活性与根系有机酸质量分数显著相关(p0.05),PEPC是促进巨尾桉根系苹果酸、柠檬酸积累的重要酶,NAD-IDH是与有机酸分解相关的酶。N素和P素是影响有机酸的主要因子,高氮低磷的配比加剧植物养分胁迫,产生更多的有机酸。综合分析表明,中氮高磷低钾的配比即N2P3K1遭受的养分胁迫最小,有机酸的质量分数最低,推荐最佳N、P2O5、K2O施肥量分别为15、9、6 g·株-1。     

马占相思人工林土壤温室气体排放日变化规律研究

【目的】探索马占相思Acacia mangium人工林土壤温室气体排放日变化规律,确定最佳观测时间。【方法】采用静态箱-气相色谱法,对华南地区马占相思人工纯林土壤3种温室气体CO_2、CH_4、N_2O通量进行连续观测。【结果】马占相思人工林土壤3种温室气体具有明显的日变化特征,马占相思人工林土壤为CO2和N2O的排放源及CH_4的吸收汇,其通量日变化幅度分别为:401.33~555.59 mg·m~(-2)·h~(-1)、24.50~34.72μg·m~(-2)·h~(-1)和-10.96~-41.88μg·m~(-2)·h~(-1)。地表CO_2、CH_4通量和5 cm深土壤温度呈极显著(P0.01)或显著(P0.05)相关,地表N_2O通量同温度的相关性不显著。【结论】通过对矫正系数分析,综合考虑3种温室气体以及取样的可操作性,华南地区马占相思人工林雨季的最佳观测时间为09:00时左右。     

淮山不同氮钾用量及镁硼配施效应研究

[目的]以淮山为研究对象,旨在明确淮山生产中的氮钾肥适宜用量及镁硼肥配施效应,以期为高产优质淮山生产和合理施肥提供科学依据。[方法]设置3个氮肥用量水平(270 kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;、360 kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;和450 kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;)和3个钾肥用量水平(270 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;、360 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;和450 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;),研究在等量有机肥(精制有机肥4500kg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;)和磷肥(144 kg P2O5/hm&;lt;sup&;gt;2&;lt;/sup&;gt;)基础上配施不同用量钾氮肥并添加镁(22.5 kg Mg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;)硼(0.21kg B/hm&;lt;sup&;gt;2&;lt;/sup&;gt;)肥对淮山叶绿素含量、生物量、品质、养分吸收量和产量的影响。[结果]研究结果表明,氮钾肥不同用量对淮山块根膨大期和收获期叶片SPAD值无显著影响。配施Mg和B明显提高淮山可溶性蛋白和氨基酸态氮含量。随施N量或施K量的增加,生产100kg淮山N、K的需求量均呈先增加后下降趋势。在360kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;基础上配施450kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;或在360 kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;和360 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;基础上配施22.5 kg Mg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;均明显提高淮山块根重量、总生物量和淮山产量。增施钾肥和配施Mg均有利于提高淮山N和K的收获指数。[结论]为获得70000-90000kg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;的淮山产量,建议在施用4500kg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;精制有机肥、360 kg N/hm&;lt;sup&;gt;2&;lt;/sup&;gt;、144 kg P2O5/hm&;lt;sup&;gt;2&;lt;/sup&;gt;基础上配施450 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;或配施360 kg K2O/hm&;lt;sup&;gt;2&;lt;/sup&;gt;和22.5 kg Mg/hm&;lt;sup&;gt;2&;lt;/sup&;gt;。     

稻田温室气体（CH4和N2O）排放影响因素及其减排措施研究进展

甲烷(CH4)和氧化亚氮(N2O)是重要的两种温室气体,近一个世纪以来,大气中这两种气体浓度持续升高,进而引起温室效应明显加剧和气候变暖等极端气候的频繁出现.稻田生态系统是大气CH4和N2O的重要源.稻田温室气体的排放受土壤性质、气候条件及人为活动等因素的交互作用和综合调控,CH4和N2O排放量与各因素的变异程度、敏感程度密切相关.全面综述了影响稻田温室气体排放的因子及温室气体减排措施的研究进展,可为制定我国稻田温室气体减排措施、促进农业可持续发展以及生态环境协调发展提供参考.