长江溶存氧化亚氮的分布与释放

于2008年1月对长江宜昌到徐六泾段干流以及部分湖泊和支流入江口进行了调查,并于2007年6月到2008年5月对长江徐六泾进行了逐月调查,采样测定了长江溶存N2O的浓度并选择合适的模型估算了其释放通量.结果表明,2008年1月长江表层河水中N2O的平均浓度为(22.0±3.5)nmo·lL-1,均处于过饱和状态,平均饱和度为180%±33%,长江向大气释放N2O通量平均为(13.7±14.6)μmol·m-·2d-1.冬季长江溶存N2O的分布规律为下游溶存N2O浓度高于中游,支流及湖泊高于干流.长江徐六泾段河水中N2O全年平均浓度为(19.4±7.3)nmol·L-1,呈现明显季节变化特征.长江徐六泾段河水中N2O平均释放通量为(43.9±24.9)μmol·m-2·d-1,夏季最高可达80.7μmol·m-·2d-1.初步估算出长江每年向大气释放N2O-N的量为12.0Gg·a-1,约占整个中国N2O排放量的1.1%.而长江输入东、黄海N2O-N的年通量为0.5Gg·a-1,对长江口及其邻近海域N2O分布及氮的生物地球化学循环有重要影响.     

Catalytic reduction of nitric oxide with carbon monoxide on copper-cobalt oxides supported on nano-titanium dioxide

A series of copper-cobalt oxides supported on nano-titanium dioxide were prepared for the reduction of nitric oxide with carbon monoxide and characterized using techniques such as XRD, BET and TPR. Catalyst CuCoOx/TiO2 with Cu/Co molar ratio of 1/2, Cu- Co total loading of 30% at the calcination temperature of 350°C formed CuCo2O4 spinel and had the highest activity. NO conversion reached 98.9% at 200°C. Mechanism of the reduction was also investigated, N2O was mainly yielded below 100°C, while N2 was produced instead at higher temperature. O2 was supposed to accelerate the reaction between NOx and CO for its oxidation of NO to give more easily reduced NO2, but the oxidation of CO by O2 to CO2 decreased the speed of the reaction greatly. Either SO2 or H2O had no adverse impact on the activity of NO reduction; however, in the presence of both SO2 and H2O, the catalyst deactivated quickly.     

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.     

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.     

不同水分管理方式下水稻生长季N_2O排放量估算:模型建立

我国水稻生产中往往采用多种水分管理方式,如持续淹水、淹水-烤田-淹水和淹水-烤田-淹水-湿润灌溉等. 水分管理方式的不同会引起水稻生长季N2O排放的显著变化. 本研究收集和整理了2005年以前17篇国内外文献报道的有关我国稻田N2O季节排放通量的71组田间原位测定资料,每组资料包括稻田氮肥施用的种类和施用量、水分管理方式、N2O季节排放量等数据,旨在建立不同水分管理方式下水稻生长季N2O直接排放量的估算模型. 分析结果表明,持续淹水稻田N2O季节排放量与施氮量无明显相关关系,在淹水-烤田-淹水和淹水-烤田-淹水-湿润灌溉的水分管理方式下,两者呈极显著线性正相关关系. 持续淹水稻田N2O季节排放总量相当于施氮量的0.02%. 基于普通最小二乘法(OLS)分析技术建立的线性回归模型估算结果表明,淹水-烤田-淹水的水分管理方式下稻田肥料氮的N2O排放系数为0.42%,但N2O季节背景排放量不显著. 在淹水-烤田-淹水-湿润灌溉的水分管理方式下,水稻生长季肥料N的N2O排放系数和N2O-N背景排放量分别为0.73%和0.79 kg·hm-2. 残差分析和效能分析显示模型具有较好的适切性. 综合3种水分管理方式,我国稻田水稻生长季N的N2O排放系数和N2O-N背景排放量平均分别为0.54%和0.43 kg·hm-2. 相对于旱作农田而言,水稻生长季肥料N的N2O排放系数较低,意味着水稻生产较旱地作物可能更有利于减缓我国农业N2O排放. 本研究建立的模型可以用于我国稻田水稻生长季N2O直接排放量的估算.     

北黄海溶解氧化亚氮的分布与通量的季节变化

根据2005年3月、 2006年4月和8月、 2007年4月和10月对北黄海进行的大面调查,分析研究了不同季节表层海水中溶解氧化亚氮（N₂O）的水平分布及海-气交换通量.结果表明,北黄海海水中溶解N₂O浓度的季节变化不大（约为12 nmol·L^-1）,但其饱和度呈现明显的季节变化,夏、秋季远高于春季,并且春季3个航次表层海水中溶解的N₂O随水温的升高由不饱和逐渐转变为过饱和,相关性分析显示,温度是影响溶解N₂O饱和度的主要因素.利用Liss和Merlivat公式（LM86）以及Wanninkhof公式（W92）分别估算了北黄海春、夏、秋3个季节N₂O的海-气交换通量,其平均值分别为（0.6±1.7）、（5.8±8.4）、（7.9±8.2） μmol·(m²·d)^-1和（1.1±2.7）、（10.2±13.6）、（13.8±14.3） μmol·(m²·d)^-1,呈现明显的季节性变化,夏、秋两季高于春季.根据北黄海3个季节的平均N₂O海-气交换通量和北黄海的面积,初步估算出北黄海N₂O的年释放量为（5.3×10^-3～9.2×10^-3） Tg·a^-1,表明北黄海海域是大气N₂O的净源.     

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.     

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.     

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.