生物炭及其老化对农田NH3挥发及N2O排放的影响

生物炭具有减缓农田NH₃挥发和N₂O排放的重要潜力,但在施入环境后常常存在“老化”现象,这为其缓解全球变暖的长期有效性带来了不确定性。为了探明生物炭的长期效应,人工加速模拟了自然界中水分、温度、氧气、土壤矿物质及微生物多种老化因素,结合多元表征手段对比不同老化方式对生物炭性质的影响,利用主成分分析法建立新的生物炭性质综合指标来反映老化强度。再通过大田控制试验,采用原位通气法和静态箱—气相色谱法监测夏玉米生长周期内老化前后生物炭施用对农田NH₃挥发和N₂O排放的影响,为生物炭的可持续应用提供科学依据。结果表明,老化过程增加了原生物炭(BC)的氧含量、比表面积(S_BET)、总孔容(V_t)及含氧官能团数量,降低了灰分、碱性、碳含量、平均孔径及其芳香性,各老化作用强度排序为：氧化老化生物炭(OBC)>矿化老化生物炭(KBC)>微生物老化生物炭(MBC)>干湿循环老化生物炭(WBC)>冻融循环老化生物炭(FBC)>BC。生物炭的添加减少...     

等氮滴灌对宿根蔗产量及土壤氧化亚氮排放的影响

为得到合理的水肥管理措施,研究等氮量下不同滴灌施肥比例对宿根蔗产量以及不同生育期蔗田土壤氧化亚氮(N2 O)通量和无机氮含量的影响,并分析蔗田土壤N2 O通量与无机氮含量之间的关系.该文以自然降雨W0为对照,设置2种滴灌灌水量水平W1(田间持水量的75％)和W2(田间持水量的85％),等量氮肥(N 300 kg·hm-...     

DCD不同施用时间对小麦生长期N2O排放的影响

通过田间试验,采用静态箱法研究相同施肥条件下,DCD不同施用时间(基肥配施,追肥配施,基追肥按比例配施)对麦季N2O排放的影响.结果表明,小麦生长期施肥配施DCD减少麦季N2O排放.从小麦整个生长季来看,与尿素处理相比,基肥配施减少N2O排放21％,追肥配施减少N2O排放26％,基追肥按比例配施减少N2O排放35％,方差分析均达显著水平(P＜0.05),其中基肥配施主要减少小麦播种-返青期N2O排放,追肥配施主要减少小麦返青-成熟期N2O排放,而基追肥按比例配施DCD减少整个小麦生长季N2O排放.在小麦的整个生长阶段,施加DCD处理的土壤NH+4-N浓度和表观硝化率均高于未施加DCD的处理,且土壤NH+4-N浓度随时间的延长而降低.在小麦播种-返青期,基肥配施处理和基追肥按比例配施处理土壤NH+4-N浓度和表观硝化率高于追肥配施处理和对照处理;在小麦的返青-成熟期,追肥配施处理和基追肥按比例配施处理土壤NH+4-N浓度和表观硝化率高于基肥配施处理和对照处理.从小麦产量来看,与尿素处理相比,基肥配施和基追肥按比例配施显著增加小麦产量,而追肥配施处理小麦产量无显著性差异.基追肥按比例配施DCD在提高小麦产量的同时显著减少N2O排放,具有大田推广的现实意义;基肥与追肥配施DCD对N2O减排效果除了与施用时间有关外,还应将降雨或灌溉量的年际变化考虑在内.     

Evolution of nitrous oxide in a nitrate-treated soil at a low partial pressure of acetylene

Summary Soil cores incubated under air atmosphere with C₂H₂ at partial pressure of 0.1 kPa, reduced NO₃ ^– to N₂O. Glucose and nitrate at higher concentration stimulated the N₂O production. Further reduction of N₂O to N₂ seemed to be temporarely inhibited. However after 12 h N₂O concentrations decreased, irrespective of soil treatment.     

Nitrogen removal in a wastewater treatment plant through biofilters: nitrous oxide emissions during nitrification and denitrification

In order to estimate N₂O emissions from immersed biofilters during nitrogen removal in tertiary treatments at urban wastewater treatment plants (WWTPs), a fixed culture from the WWTP of “Seine Centre” (Paris conurbation) was subjected to lab-scale batch experiments under various conditions of oxygenation and a gradient of methanol addition. The results show that during nitrification, N₂O emissions are positively related to oxygenation (R ² = 0.99). However, compared to the rates of ammonium oxidation, the percentage of emitted N₂O is greater when oxygenation is low (0.5–1 mgO₂ L⁻¹), representing up to 1% of the oxidized ammonium (0.4% on average). During denitrification, the N₂O emission reaches a significant peak when the quantity of methanol allows denitrification of between 66% and 88%. When methanol concentrations lead to a denitrification of close to 100%, the flows of N₂O are much lower and represent on average 0.2% of the reduced nitrate. By considering these results, we can estimate, the emissions of N₂O during nitrogen removal, at the “Seine Centre” WWTP, to approximately 38 kgN-N₂O day⁻¹.     

微生物脱氮过程中氧化亚氮的释放机理及减释措施

微生物脱氮是去除废水中含氮污染物质的重要方法,微生物的种类及其生存环境不同会导致其释放N_2O的途径及机理具有差异性。本文系统地综述了脱氮过程产生N_2O微生物的种类、特点及其释放N_2O的多重途径,综合分析了参与N_2O形成的相关酶类和影响N_2O释放的关键因素,同时,提出了减缓生物脱氮过程释放N_2O的相关措施,对未来脱氮工艺的优化与N_2O释放的控制提供新思路。     

DCD不同施用时间对水稻生长期CH4和N2O排放的影响

硝化抑制剂传统的施用方法是在作物移栽或播种前与基肥配合施用.通过温室盆栽试验研究相同施肥条件下,硝化抑制剂双氢胺(dicyandiamide, DCD)不同施用时间(与基肥混施、分孽肥后施入、穗肥后施入)对水稻生长期CH4和N2O排放的影响.结果表明,施入DCD能同时降低CH4和N2O排放量.就整个水稻生长期而言,与基肥混施DCD分别降低21.41%的CH4排放量和8.00%的N2O排放量;调节DCD施用时间至分孽肥后显著降低30.30%的N2O排放量,同时降低5.24%的CH4排放量.就施入DCD到水稻收获的特定生长阶段而言,缓施DCD分别降低32.65%的N2O排放量和11.18%的CH4排放量;晚施DCD对CH4和N2O排放的影响不大.CK、早施DCD、缓施DCD及晚施DCD处理CH4平均排放通量分别为0.95、0.75、0.87 mg/(m2 · h)及0.94 mg/(m2 · h),N2O平均排放通量为155.67、143.24、108.50 μg/(m2 · h)及153.24 μg/(m2 · h),缓施DCD显著降低CH4和N2O排放量(p＜0.01).土壤温度是影响N2O排放的主要因素,而CH4排放通量与土壤Eh呈显著负相关(p＜0.01).     

控释肥施用对土壤N2O排放的影响——以华北平原冬小麦/夏玉米轮作系统为例

控释肥作为一种能够提高肥料利用率、保障作物产量和节约劳动力的新型肥料已经在作物生产中得到广泛应用,而控释肥对土壤N_2O排放影响结果的差异使其成为当前科学评估控释肥施用环境效应的焦点问题之一。因此,旨在探讨不同种类控释肥及氮素水平施用对华北平原冬小麦/夏玉米轮作系统土壤N_2O排放的影响,为科学评价控释肥施用的环境效应及其推广应用提供科学依据。本研究监测采用静态暗箱—气相色谱法对不同控释肥施用下土壤N_2O排放、环境因素以及产量进行了周年监测,探讨了不同处理(对照处理(CK)、控释肥处理1(CRF1)、优化控释肥处理1(80%CRF1)、优化控释肥处理2(80%CRF2)和控释肥处理3(CRF3+尿素))下土壤N_2O排放特征及土壤温湿度对其的影响。结果表明:控释肥施用下冬小麦/夏玉米轮作系统中土壤N_2O排放峰高值主要出现在基肥施用并伴随灌溉(或降雨)后,一般持续时间约为7—10 d,小麦返青期灌溉以及玉米后期降雨会引起微弱的N_2O排放峰。不同处理土壤N_2O排放通量变化范围为~(-2)35.61—2625.01μg N_2O m~(-2)h~(-1),平均排放通量为23.88—51.39μg N_2O m~(-2)h~(-1),与CRFI相比,80%CRF1和80%CRF2处理能够减小施肥期的N_2O排放峰值,但不改变轮作周期土壤N_2O排放季节变化规律。CK处理和CRF3+尿素处理土壤N_2O排放通量与5 cm深度土壤温度之间表现出显著的正相关性(r~2=0.38,P0.01;r~2=0.30,P0.05);CRF1处理和80%CRF1处理在冬小麦生长季及整个轮作周期内与土壤孔隙含水率(WFPS)表现为显著的正相关关系(冬小麦生长季分别为r~2=0.50,P0.01;r~2=0.39,P0.05;整个轮作周期分别为r~2=0.39,P0.05;r~2=0.43,P0.05)。80%CRF2处理N_2O年排放总量最高,为(2.89±0.24)kg N/hm~2。相同控释肥种类条件下,80%CRF1处理比CRF1处理减少了14.23%,但并未达到显著水平;相同施氮量水平下,CRF1处理与(CRF3+尿素)处理之间N_2O年排放总量差异不显著,而80%CRF1处理比80%CRF2处理N_2O年排放总量减少16.16%,并达到显著水平(P0.05)。本研究不同处理之间N_2O直接排放系数在0.29%—0.42%之间,均明显低于IPCC 1.0%的默认值。各控释肥处理产量与当地农民常规施肥量条件下产量没有显著性差异。因此在华北地区冬小麦/夏玉米轮作系统中应用控释肥技术可以在保证产量的前提下有效减少土壤N_2O排放,并且仍存在一定的减排空间。     

Nitrous oxide emissions from agricultural fields: Assessment, measurement and mitigation

In this paper we discuss three topics concerning N₂O emissions from agricultural systems. First, we present an appraisal of N₂O emissions from agricultural soils (Assessment). Secondly, we discuss some recent efforts to improve N₂O flux estimates in agricultural fields (Measurement), and finally, we relate recent studies which use nitrification inhibitors to decrease N₂O emissions from N-fertilized fields (Mitigation).To assess the global emission of N₂O from agricultural soils, the total flux should represent N₂O from all possible sources; native soil N, N from recent atmospheric deposition, past years fertilization, N from crop residues, N₂O from subsurface aquifers below the study area, and current N fertilization. Of these N sources only synthetic fertilizer and animal manures and the area of fields cropped with legumes have sufficient global data to estimate their input for N₂O production. The assessment of direct and indirect N₂O emissions we present was made by multiplying the amount of fertilizer N applied to agricultural lands by 2% and the area of land cropped to legumes by 4 kg N₂O-N ha^-1. No regard to method of N application, type of N, crop, climate or soil was given in these calculations, because the data are not available to include these variables in large scale assessments. Improved assessments should include these variables and should be used to drive process models for field, area, region and global scales.Several N₂O flux measurement techniques have been used in recent field studies which utilize small and ultralarge chambers and micrometeorological along with new analytical techniques to measure N₂O fluxes. These studies reveal that it is not the measurement technique that is providing much of the uncertainty in N₂O flux values found in the literature but rather the diverse combinations of physical and biological factors which control gas fluxes. A careful comparison of published literature narrows the range of observed fluxes as noted in the section on assessment. An array of careful field studies which compare a series of crops, fertilizer sources, and management techniques in controlled parallel experiments throughout the calendar year are needed to improve flux estimates and decrease uncertainty in prediction capability.There are a variety of management techniques which should conserve N and decrease the amount of N application needed to grow crops and to limit N₂O emissions. Using nitrification inhibitors is an option for decreasing fertilizer N use and additionally directly mitigating N₂O emissions. Case studies are presented which demonstrate the potential for using nitrification inhibitors to limit N₂O emissions from agricultural soils. Inhibitors may be selected for climatic conditions and type of cropping system as well as the type of nitrogen (solid mineral N, mineral N in solution, or organic waste materials) and applied with the fertilizers.     

Earthworm effects on gaseous emissions during vermifiltration of pig fresh slurry

Treatment of liquid manure can result in the production of ammonia, nitrous oxide and methane. Earthworms mix and transform nitrogen and carbon without consuming additional energy. The objective of this paper is to analyse whether earthworms modify the emissions of NH₃, N₂O, CH₄ and CO₂ during vermifiltration of pig slurry.The experiment used mesocosms of around 50 L, made from a vermifilter treating the diluted manure of a swine house. Three levels of slurry were added to the mesocosms, with or without earthworms, during one month, in triplicate. Earthworm abundance and gas emissions were measured three and five times, respectively.There was a decrease in emissions of ammonia and nitrous oxide and a sink of methane in treatments with earthworms. We suggest that earthworm abundance can be used as a bioindicator of low energy input, and low greenhouse gas and ammonia output in systems using fresh slurry with water recycling.     

牲畜排泄物返还对草地土壤氮转化和氧化亚氮(N2O)排放的影响研究进展

牲畜排泄物返还被认为是对草地的一种天然的施肥措施,也是草地养分归还的一种重要途径,对于维持土壤肥力和植被生产力具有十分重要的生态学意义。论述了放牧牲畜粪便和尿液自身降解及其氮素变化、粪尿返还对草地土壤氮转化和氧化亚氮(N₂O)排放的作用机制及影响效应,指出排泄物氮输入使粪尿斑块成为草地土壤氮转化和N₂O排放的活跃点,且不同排泄物类型、土壤理化特性和气候条件等使土壤氮素矿化、固持、硝化及反硝化等关键过程具有复杂性和差异性,进而导致不同类型草地生态系统N₂O排放对牲畜排泄物返还的响应不尽相同。建议未来在全球气候变化背景下,应加强草地牲畜排泄物-植被-土壤体系氮素生物地球化学循环过程的系统研究,进一步加深天然草地关键氮素转化过程和N₂O排放的微生物作用机制方面的认识,从而有助于为优化放牧牲畜排泄物的管理模式、制定科学合理的草地土壤养分调控策略和维持草地生态系统可持续发展提供科学有效的理论指导。     

Losses of inorganic carbon and nitrous oxide from a temperate freshwater wetland in relation to nitrate loading

We studied the export of inorganic carbon and nitrous oxide (N₂O) from a Danish freshwater wetland. The wetland is situated in an agricultural catchment area and is recharged by groundwater enriched with nitrate (NO₃ ^–) (1000 M). NO₃ ^– in recharging groundwater was reduced (57.5 mol NO₃ ^– m^–2 yr^–) within a narrow zone of the wetland. Congruently, the annual efflux of carbon dioxide (CO₂) from the sediment was 19.1 mol C m^–2 when estimated from monthly in situ measurements. In comparison the CO₂ efflux was 4.8 mol C m^–2 yr^–1 further out in the wetland, where no NO₃ ^– reduction occurred. Annual exports of inorganic carbon in groundwater and surface water was 78.4 mol C m^–2 and 6.1 mol C m^–2 at the two sites, respectively. N₂O efflux from the sedimenst was detectable on five out of twelve sampling dates and was significantly (P < 0.0001) higher in the NO₃ ^– reduction zone (0.35–9.40 mol m^–2 h^–1, range of monthly means) than in the zone without NO₃ ^– reduction (0.21–0.41 mol m^–2 h^–1). No loss of dissolved N₂O could be measured. Total annual export of N₂O was not estimated. The reduction of oxygen (O₂) in groundwater was minor throughout the wetland and did not exceed 0.2 mol 0₂ m^–2yr^–1. Sulfate (SO₄ ^––) was reduced in groundwater (2.1 mol SO₄ ^–– m^–2 yr^–1) in the zone without NO₃ ^– reduction. Although the NO₃ ^– in our wetland can be reduced along several pathways our results strongly suggest that NO₃ ^– loading of freshwater wetlands disturb the carbon balance of such areas, resulting in an accelerated loss of inorganic carbon in gaseous and dissolved forms.     

双氢胺对土壤裂缝产生过程中N2O释放的影响

模拟稻田土壤在加入不同量的 (NH₄)₂SO₄和双氢按(DCD)抑制剂的溶液后先进行淹水培养,然后让土壤自然蒸发变干,直至土壤产生裂缝到裂缝稳定,最后在裂缝稳定后的复水的连续培养试验。通过模拟对土壤进行复杂的、动态的水分含量变化过程中试验,探讨双氢胺抑制剂对其N₂O释放的影响。每天监测土体释放的N₂O通量,以及渗漏液中溶解的N₂O浓度和pH值。这些监测结果表明：在相同的水分管理条件下,土壤中没有氮肥加入,只有DCD加入的A处理释放N₂O气体最少,其平均释放通量为340.91 μg m^-2 h^-1; 土壤中有高剂量的氮肥和DCD加入的E处理释放N₂O最多,其平均释放通量为9280.23 μg m^-2 h^-1。裂缝产生稳定后的复水能减少N₂O向空气中的释放。渗漏液中的N₂O浓度都是过饱和的。当土壤中肥料(NH₄)₂SO₄加入量(每千克土壤中外加N≤3g)相对较少的情况下,DCD抑制剂能抑制裂缝产生过程中的N2O释放;当土壤中肥料(NH₄)₂SO₄加入量(每千克土壤中外加N≥6g)相对较多的情况下,DCD抑制裂缝产生过程中的N₂O释放效果不明显。此外还得出(NH₄)₂SO₄和DCD的加入量比是10:1 时,其抑制N₂O排放的效果比(NH₄)₂SO₄和DCD的加入量比分别是10∶1.5和10∶2要好。土体释放的N₂O通量和渗漏液中溶解的N₂O浓度之间不存在相关性,土体释放的N₂O通量和渗漏液中的pH值之间也不存在相关性。但是渗漏液中的N2O浓度和pH值之间存在显著的正线性相关关系。     

Rates and pathways of nitrous oxide production in a shortgrass steppe

Most of the small external inputs of N to the Shortgrass steppe appear to be conserved. One pathway of loss is the emission of nitrous oxide, which we estimate to account for 2.5–9.0% of annual wet deposition inputs of N. These estimates were determined from an N₂O emission model based on field data which describe the temporal variability of N₂O produced from nitrification and denitrification from two slope positions. Soil water and temperature models were used to translate records of air temperature and precipitation between 1950 and 1984 into variables appropriate to drive the gas flux model, and annual N₂O fluxes were estimated for that period. The mean annual fluxes were 80 g N ha^–1 for a midslope location and 160 g N ha^–1 for a swale. Fluxes were higher in wet years than in dry, ranging from 73 to 100 g N ha^–1y^–1at the midslope, but the variability was not high. N₂O fluxes were also estimated from cattle urine patches and these fluxes while high within a urine patch, did not contribute significantly to a regional budget. Laboratory experiments using C₂H₂ to inhibit nitrifiers suggested that 60–80% of N₂O was produced as a result of nitrification, with denitrification being less important, in contrast to our earlier findings to the contrary. Intrasite and intraseasonal variations in N₂O flux were coupled to variations in mineral N dynamics, with high rates of N₂O flux occurring with high rates of inorganic N turnover. We computed a mean flux of 104 g N ha^–1 y^–1 from the shortgrass landscape, and a flux of 2.6 × 109 g N y^– from all shortgrass steppe (25 × 106 ha).     

Nitrous oxide emissions from surface flow and subsurface flow constructed wetland microcosms: Effect of feeding strategies

The effects of continuous and intermittent feeding strategies on nitrogen removal and N₂O emission from surface flow and subsurface flow constructed wetlands were evaluated in this study. Microcosm wetlands planted with Phragmites australis were constructed and operated with different feeding strategies for the 4-month experiment. Results showed the intermittent feeding strategy could enhance the removal of ammonium effectively in the subsurface flow constructed wetlands, although it had no significant effect for the surface flow wetlands. And the intermittent feeding mode could promote the emission of N₂O. The amount of N₂O-N emission from the subsurface flow constructed wetlands with intermittent feeding mode was about 5 times higher than that with continuous feeding strategy and the emission rate ranged from 0.09 ± 0.03 to 7.33 ± 1.49 mg/m²/h. Compared with the surface flow constructed wetlands, the N₂O emission in the subsurface flow constructed wetlands was affected significantly by the intermittent feeding mode.     

Emission of nitrous oxide through a snowpack in ten types of temperate ecosystems in Japan

The release of N₂O from the snow surface in winter and the soil in summer was measured in ten types of temperate ecosystems (bare ground, grassland, forest, marsh, and crop field) in Japan. The snow-covered crop field emitted by far the largest amount of N₂O during the winter. Among the snow-covered natural ecosystems studied, marshy ecosystems showed the largest effluxes of N₂O. Based on results showing that the magnitude of the winter N₂O fluxes was not negligible compared with that of the summer N₂O fluxes and because the snow period in the areas studied area is sufficiently long, we suggest that the winter N₂O fluxes contribute significantly to the annual emission of N₂O in the study areas.     

土壤磷含量与有效性对N2O排放量的影响元分析

土壤氧化亚氮(N₂O)主要产生于土壤微生物参与的氮循环过程,其排放量受磷含量及有效性影响。添加磷肥有助于缓解陆地生态系统磷限制,提升土壤有效磷含量,进一步影响土壤微生物对氮的利用,同时控制N₂O排放。然而不同独立实验中N₂O对外源磷添加的响应差异较大。研究从发表的中、英文文献中收集了54份关于施用磷肥与N₂O排放量的观测结果,采用元分析方法确定添加外源磷后N₂O排放量的响应差异及潜在影响因素。结果表明：(1)外源磷添加对土壤N₂O排放量影响不显著;但在磷肥施用量> 50 kg P/hm²的室外实验中土壤N₂O排放量显著降低了32.5%;施用NaH₂PO₄的室内实验中N₂O排放量显著降低了18.4%。(2)土壤N₂O对外源磷添加响应的高变异性是磷肥施用量和土壤含水量、土壤pH、土地利用类型、磷肥种类、纬度和实验时间多种影响...     

Emissions of nitrous oxide from three tropical forests in Southern China in response to simulated nitrogen deposition

Emissions of nitrous oxide (N₂O) from the soil following simulated nitrogen (N) deposition in a disturbed (pine), a rehabilitated (pine and broadleaf mixed) and a mature (monsoon evergreen broadleaf) tropical forest in southern China were studied. The following hypotheses were tested: (1) addition of N will increase soil N₂O emission in tropical forests; and (2) any observed increase will be more pronounced in the mature forest than in the disturbed or rehabilitated forest due to the relatively high initial soil N concentration in the mature forest. The experiment was designed with four N treatment levels (three replicates; 0, 50, 100, 150 kg N ha⁻¹ year⁻¹ for C (Control), LN (Low-N), MN (Medium-N), and HN (High-N) treatment, respectively) in the mature forest, but only three levels in the disturbed and rehabilitated forests (C, LN and MN). Between October 2005 to September 2006, soil N₂O flux was measured using static chamber and gas chromatography methodology. Nitrogen had been applied previously to the plots since July 2003 and continued during soil N₂O flux measurement period. The annual mean rates of soil N₂O emission in the C plots were 24.1 ± 1.5, 26.2 ± 1.4, and 29.3 ± 1.6 μg N₂O–N m⁻² h⁻¹ in the disturbed, rehabilitated and mature forest, respectively. There was a significant increase in soil N₂O emission following N additions in the mature forest (38%, 41%, and 58% when compared to the C plots for the LN, MN, and HN plots, respectively). In the disturbed forest a significant increase (35%) was observed in the MN plots, but not in the LN plots. The rehabilitated forest showed no significant response to N additions. Increases in soil N₂O emission occurred primarily in the cool-dry season (November, December and January). Our results suggest that the response of soil N₂O emission to N deposition in tropical forests in southern China may vary depending on the soil N status and land-use history of the forest.     

免耕施肥对稻田甲烷与氧化亚氮排放及其温室效应的影响

2008年采用静态箱-气相色谱法对鄂东南免耕不施肥(NT₀)、翻耕不施肥(CT₀)、免耕施肥(NTC)和翻耕施肥(CTC) 4种处理下稻田CH₄和N₂O的排放进行测定.结果表明：各处理CH₄排放均呈先升高后降低的季节性规律,而N₂O排放的季节性规律不明显;施肥显著提高了稻田CH₄和N₂O的排放.与翻耕不施肥相比,免耕不施肥显著提高了CH₄的排放量,并显著降低了N₂O的排放量;与翻耕施肥相比,免耕施肥仅略降低了CH₄的排放量和略提高了N₂O的排放量.对稻田CH₄和N₂O两种气体的综合温室效应分析表明,与翻耕不施肥相比,免耕不施肥的综合温室效应提高了25.9%,与翻耕施肥相比,免耕施肥的综合温室效应降低了10.1%.因此,合理的肥料运筹和稻田免耕技术可降低两种气体的综合温室效应.