不同水分管理方式下水稻生长季N2O排放量估算：模型应用

基于田间原位测定结果,作者建立了不同水分管理方式下稻田N₂O排放估算的统计模型. 在模型验证和输入参数检验的基础上, 本研究应用模型估算了20世纪50～90年代我国稻田水稻生长季N₂O直接排放量. 结果表明, 由于水稻种植面积和氮输入量的增加、以及水分管理方式的变化, 稻田N₂O-N季节排放量从20世纪50年代平均每年9.55 Gg增加到了90年代每年32.26 Gg, 同期伴随着水稻单产的增加. 在20世纪50～90年代间, 我国水稻生产的N₂O-N排放量以平均每10 a6.74 Gg的速度递增. 20世纪50年代和90年代稻田N₂O-N季节排放通量平均分别为0.32 kg·hm^-2和1.00 kg·hm^-2, 相当于季节氮输入总量的0.37%和0.46%. 本研究模型估算50～90年代间稻田N₂O季节排放量的不确定性为59.8%～37.5%. 就全国稻田的不同种植区域而言, 长江中下游地区稻田水稻生长季N₂O排放量占全国稻田N₂O排放总量的51%～56%. 20世纪90年代水稻生长季N₂O排放量约占我国农田N₂O年总排放量的8%～11%. 相对于旱地作物而言, 过去几十年水稻生产的发展在很大程度上减缓了我国农业生产的N₂O排放. 然而, 随着水稻生产中节水灌溉的推广和氮肥施用量的增加, 我国稻田N₂O季节排放量预计将相应增加.     

人工湿地污水处理系统中氧化亚氮的释放规律研究

利用静态箱-气相色谱法研究了潜流和表面流人工湿地系统中N2O的释放规律和相关的氨氧化细菌.结果表明,潜流和表面流人工湿地的N2O平均通量分别为296.5μg.(m2.h)-1和28.2μg.(m2.h)-1,总体上均表现为大气N2O的排放源,前者的N2O平均释放通量高于农田、森林、草原和沼泽湿地等生态系统,潜流方式促进了N2O的释放.潜流和表面流人工湿地N2O通量有较大的月份差异和明显的日变化特征,最高值出现在7月,分别为(762.9±239.3)μg.(m2.h)-1和(91.9±20.3)μg.(m2.h)-1,一天中的极大值和极小值分别出现在中午和凌晨.温度和芦苇的生长情况对N2O通量有一定的影响.人工湿地系统进水端,较高浓度的污水和充足的碳、氮源,促进了硝化和反硝化过程,使得N2O通量均高于出水端.克隆结果表明,人工湿地污水处理系统中与N2O产生相关的氨氧化细菌主要为Nitrosomonas和Nitrosospira.     

EDTA对生物转鼓的NO废气净化效率的影响

生物转鼓过滤器(Rotating Drum Biofilter,RDB)是一种能有效净化氮氧化物废气的新型生物反应器,但在之前的实验发现,由于NO在液相中的低溶解度降低了NO在RDB中的传质效果,从而影响其去除效率。改善气液传质速率是整个反硝化降解NO过程的关键步骤,实验用CuⅡ(EDTA)、ZnⅡ(EDTA)、MgⅡ(EDTA)和FeⅡ(EDTA)等络合剂添加到营养液中,利用NO能与络合剂结合的原理,使得NO能快速溶于液相,从而使NO去除效率由原来平均85%提高到98%。     

厌气条件下百菌清对土壤N2O和CH4排放的影响

在密闭、淹水、充N2的严格厌氧条件下对土壤进行了14d的培养试验,研究了杀菌剂百菌清在添加水平为田间施用量（FR）(5.5 mg·kg-1),20倍(20FR)和40倍田间施用量(40FR)时对强酸性、酸性、中性和碱性土壤N2O和CH4排放的影响.结果表明,20FR和40 FR的百菌清能够显著促进N2O向N2的还原,降低N2O排放,在酸性、中性和碱性土壤中培养14d后,对照处理的N2O排放量为0.076~0.46mg·kg-1,而20FR和40FR处理的N2O排放量为0.004~0.06mg·kg-1,降低了１个数量级.反硝化作用和有机氮矿化作用强的土壤中,百菌清减少N2O排放作用更明显.反硝化底物NO-3的存在对CH4的产生与排放具有显著的抑制作用.在加入百菌清未对NO-3浓度产生显著影响的土壤中,百菌清对CH4排放量没有明显影响,在对NO-3浓度产生显著影响的土壤中,CH4排放量随着NO-3的增加而减少,说明百菌清可能通过影响反硝化过程中NO-3的消耗而影响CH4排放.     

Characteristics of emissive spectrum and the removal of nitric oxide in N2/O2/NO plasma with argon additive

Although the approach using non-thermal plasma (NTP) for deNOx has been studied for over 15 years, how to achieve higher removal e ciency with lower cost is still a barrier for its industrial application. In order to investigate the impact of the argon additive on electron density, energy and nitric oxide reduction process in plasma, the spectrum of the dielectric barrier discharge at atmospheric pressure in a coaxial reactor was measured using the monochromater with high resolution. The comparative experiments for NO reduction were carried out simultaneously in N2/O2/NO plasma stream with and without argon, respectively. The nitrogen molecular spectrum which is attributed to the energy level transition (C3 u ! B3 g) was compared in the wavelength range 300–480 nm and the electron density and temperature were determined based on the relative intensities and Stark broadening width of spectral lines. The spectrum results indicated that the argon additive could enhance the intensity of emissive spectrum of plasma, thus the electron concentration as well as the energy was increased, and finally prompted the ionization rate to produce active N, O and O3. The results of NO reduction showed that NO conversion e ciency increased in the range of 10%–30% with 5% addition of argon in stream comparing with the condition without argon additive. This study will play a positive role in the industrial application of dielectric barrier discharge deNOx reactor.     

Novel Fe/glass composite adsorbent for As(V) removal

An effective adsorbent for arsenic removal was synthesized by hydrothermal treatment of waste glass powder (GP), followed by loading Fe(Ⅲ) oxyhydroxide onto the surface of waste glass powder. The ≡Si-O-H group was formed on the surface of GP and the specific surface area of GP powder was slightly increased after hydrothermal treatment. FeOOH was loaded onto the surface of hydrothermally treated waste glass powder (HGP) by the hydrolysis of FeCl3. The formation conditions of FeOOH were also investigated. The...     

Integrated assessment of promising measures to decrease nitrogen losses from agriculture in EU-27

Following the recognition of the detrimental effects of nitrogen (N) losses from agriculture in the European Union (EU) on human health and environment, series of environmental policy measures have been implemented from the early 1990s onwards. However, these measures have only been partially successful. Clearly, there is lack of integration of available measures and there is lack of enforcement and hierarchy; which measures should be implemented first? We identified and assessed three ‘most promising measures’ to decrease N losses from agriculture, i.e., (i) balanced fertilization, (ii) low-protein animal feeding, and (iii) ammonia (NH₃) emissions abatement measures. Environmental-economic assessments were made using scenario analyses and the modeling tools MITERRA-EUROPE and CAPRI.In the baseline scenario (business as usual), N use efficiency (NUE) in crop production increases from 44% in 2000 to 48% in 2020, while total N losses decrease by 10%. Implementation of promising measures increases NUE further to 51–55%, and decreases NH₃ emissions (by up to 23%), nitrous oxide (N₂O) emissions (by up to 10%) and N leaching losses (by up to 35%). Differences in responsiveness to promising measures varied between and within Member States. Strict implementation of balanced fertilization in nitrate vulnerable zones, as defined in the Nitrates Directive, decreases total farmers’ income in EU-27 by 1.7 billion euros per year. Implementation of all three measures decreases farmers income by 10.8 and total welfare by 17 billion euros per year, without valuing the environmental benefits.The study presented here is one of the first EU-wide integrated assessments of the effects of policy measures on all major N losses from agriculture and their economic costs. Our results show that the most promising measures are effective in enhancing NUE and decreasing NH₃ and N₂O emissions to the atmosphere and N leaching to groundwater and surface waters, but that income effects are significant. The order of implementation of the measures is important; NH₃ emissions abatement measures must be implemented together with balanced N fertilization.     

Review of greenhouse gas emissions from crop production systems and fertilizer management effects

Fertilizer nitrogen (N) use is expanding globally to satisfy food, fiber, and fuel demands of a growing world population. Fertilizer consumers are being asked to improve N use efficiency through better management in their fields, to protect water resources and to minimize greenhouse gas (GHG) emissions, while sustaining soil resources and providing a healthy economy. A review of the available science on the effects of N source, rate, timing, and placement, in combination with other cropping and tillage practices, on GHG emissions was conducted. Implementation of intensive crop management practices, using principles of ecological intensification to enhance efficient and effective nutrient uptake while achieving high yields, was identified as a principal way to achieve reductions in GHG emissions while meeting production demands. Many studies identified through the review involved measurements of GHG emissions over several weeks to a few months, which greatly limit the ability to accurately determine system-level management effects on net global warming potential. The current science indicates: (1) appropriate fertilizer N use helps increase biomass production necessary to help restore and maintain soil organic carbon (SOC) levels; (2) best management practices (BMPs) for fertilizer N play a large role in minimizing residual soil nitrate, which helps lower the risk of increased nitrous oxide (N₂O) emissions; (3) tillage practices that reduce soil disturbance and maintain crop residue on the soil surface can increase SOC levels, but usually only if crop productivity is maintained or increased; (4) differences among fertilizer N sources in N₂O emissions depend on site- and weather-specific conditions; and (5) intensive crop management systems do not necessarily increase GHG emissions per unit of crop or food production; they can help spare natural areas from conversion to cropland and allow conversion of selected lands to forests for GHG mitigation, while supplying the world's need for food, fiber, and biofuel. Transfer of the information to fertilizer dealers, crop advisers, farmers, and agricultural and environmental authorities should lead to increased implementation of fertilizer BMPs, and help to reduce confusion over the role of fertilizer N on cropping system emissions of GHGs. Gaps in scientific understanding were identified and will require the collaborative attention of agronomists, soil scientists, ecologists, and environmental authorities in serving the immediate and long-term interests of the human population.     

Sheepfolds as “hotspots” of nitric oxide (NO) emission in an Inner Mongolian steppe

We investigated nitric oxide (NO) fluxes at a summer and a winter sheepfold in the Baiyinxile livestock farm, near Xilinhot, Inner Mongolia, which are a typical feature of the regional husbandry. Using a manual static opaque chamber/chemiluminescence measuring system, we intermittently observed fluxes in the summer sheepfold between May 28th and September 26th 2005 and in both winter and summer sheepfolds between March 8th and October 18th 2006. During these periods, mean NO emissions (±S.E., in terms of mass of nitrogen) were 124.0 ± 28.7, 134.6 ± 23.3 (summer sheepfold) and 214.4 ± 79.6 μg NO–N m⁻² h⁻¹ (winter sheepfold), respectively, and thus, three magnitudes higher than observed steppe NO emissions in the same region. The NO fluxes were not significantly different between the 2 years, but in summer they were much higher than in spring (p < 0.05). Temperature and moisture of the faeces layer significantly regulated the NO fluxes (p < 0.01). The direct NO emission factor (EF) for faeces and urine excreted in the sheepfolds was 0.7 g NO–N_emitted kg⁻¹ N_excreted, which was almost 37 times lower than a recently reported N₂O EF. We estimated the total NO emission from the sheepfolds of the Baiyinxile livestock farm to be 1.82 ± 0.43 tons NO–N year⁻¹, which accounts to approximately 12.3% of the total NO emission from this steppe region. With the rapid increase of livestock numbers, sheepfold NO emissions may further increase and contribute to high N deposition in confined areas around sheepfolds.     

催化脱除氮氧化物研究进展

消除氮氧化物污染是环境保护中的一项重要课题。催化脱除氮氧化物一直是人们解决上述课题应用的主要方法。本文对催化脱除法中应用的各种催化剂的研究进展状况作一回顾和总结