Biosphere–atmosphere exchange of reactive nitrogen and greenhouse gases at the NitroEurope core flux measurement sites: Measurement strategy and first data sets

The NitroEurope project aims to improve understanding of the nitrogen (N) cycle at the continental scale and quantify the major fluxes of reactive N by a combination of reactive N measurements and modelling activities. As part of the overall measurement strategy, a network of 13 flux ‘super sites’ (Level-3) has been established, covering European forest, arable, grassland and wetland sites, with the objective of quantifying the N budget at a high spatial resolution and temporal frequency for 4.5 years, and to estimate greenhouse gas budgets (N₂O, CH₄ and CO₂). These sites are supported by a network of low-cost flux measurements (Level-2, 9 sites) and a network to infer reactive N fluxes at 58 sites (Level-1), for comparison with carbon (C) flux measurements.Measurements at the Level-3 sites include high resolution N₂O, NO (also CH₄, CO₂) fluxes, wet and dry N deposition, leaching of N and C and N transformations in plant, litter and soil. Results for the first 11 months (1.8.2006 to 30.6.2007) suggest that the grasslands are the largest source of N₂O, that forests are the largest source of NO and sink of CH₄ and that N deposition rates influence NO and N₂O fluxes in non-agricultural ecosystems. The NO and N₂O emission ratio is influenced by soil type and precipitation. First budgets of reactive N entering and leaving the ecosystem and of net greenhouse gas exchange are outlined. Further information on rates of denitrification to N₂ and biological N₂ fixation is required to complete the N budgets for some sites. The quantitative roles played by CO₂, N₂O and CH₄ in defining net greenhouse gas exchange differ widely between ecosystems depending on the interactions of climate, soil type, land use and management.     

燃煤锅炉烟气中一氧化氮排放浓度测量的不确定度评定

根据《测量不确定度评定与表示》（JJF1059-1999）,对燃煤锅炉烟气中一氧化氮排放浓度的测量不确定度进行评定。对废气监测领域不确定度评定具有现实意义。     

Environmental impacts of irrigated sugarcane production: Nitrogen lost through runoff and leaching

There is concern about environmental impacts of cropping in catchments of Australia's Great Barrier Reef, especially losses of nitrogen (N) from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out from other crops/regions because it is grown with the highest applications of irrigation water and N fertiliser rates of any sugarcane producing region in Australia, attributes which may enhance losses of N. Little is known about N losses from sugarcane production systems, especially irrigated systems. We measured parts of the water and N balance over three sugarcane crops at three contrasting sites in different parts of the Burdekin region, covering a range of soil types/textures and irrigation managements. The experimental data were used to parameterise the APSIM-Sugarcane cropping systems model, and the model then used to ‘infill’ missing data and develop more complete water and N balances for each of the crops at the three sites. The model was also used to simulate long-term yields and N losses through runoff and leaching below the root zone at the sites under a range of N fertiliser and irrigation management practices. Unlike the experience in other cropping systems, N losses through runoff and leaching below the root zone were not higher at our sites than measured in rainfed sugarcane production systems. The long-term simulations showed there were clear opportunities for reducing N losses while maintaining yields through reducing N fertiliser application rates. Simulations results suggested that long-term N surpluses of 50 kg ha⁻¹ yr⁻¹, considerably less than those during the experiment or common in the study region, were sufficient to maintain yields but reduce N losses by 50-57%. So, N fertiliser management should aim to keep surpluses to that level. Improved irrigation management could also help reduce N losses but generally to a much lesser extent than reduced N fertiliser applications. Research is required to confirm these predicted benefits, and investigate potential interaction between N fertiliser and irrigation management practices, and impacts of other management practices.     

Carbon dioxide emissions from spring ploughing of grassland in Ireland

Grassland re-seeding or land-use change requires ploughing, which may enhance carbon dioxide (CO₂) emissions from soil. This study observed the short to intermediate-term (37 days) effects of ploughing on CO₂ emissions from poorly drained grassland using automated soil respiration chambers. Immediately after ploughing, a brief peak in CO₂ emissions from soil occurred with a maximum observed flux of 6.91 g CO₂ m⁻² h⁻¹. Contradictory to other reported results, ecosystem respiration after ploughing was lower on the ploughed than on the grass site. After including estimates of photosynthesis in the analysis, ploughing led to significantly higher net CO₂ emissions than from grassland. The main mechanism of C loss during ploughing was most likely due to a reduction in gross primary production rather than enhanced soil respiration.     

碳源类型对污水生物处理过程中氧化亚氮释放的影响

碳源是污水生物处理过程中N2O释放的重要影响因素.本试验以不同碳源（葡萄糖、乙酸钠和淀粉）条件下的SBR反应器为研究对象,分析了碳源类型对于N2O释放的影响作用.结果发现,N2O释放主要发生在好氧段,且释放总量受碳源影响,以乙酸钠为碳源的反应器产生的N2O最多,释放速率最大,其次为葡萄糖,淀粉最少,N2O转化率分别为7...     

NOx photocatalytic degradation on active concrete road surface — from experiment to real-scale application

The use of titanium dioxide (TiO₂) as a photocatalyst in concrete pavements has received considerable attention in recent years due to its ability to decontaminate via photocatalytic processes. The objective of this study is to assess the effectiveness of activated concrete road in the degradation of nitrogen oxides (NO_x). We have used a TiO₂ and activated carbon (AC) permeable spray solution to coat concrete to assess its NO_x purifying ability. A number of experiments were undertaken to ascertain the conditions that affect NO_x purification. Indoor simulation experiments with active concrete road at optimum conditions show that it has good purification ability, self-regeneration and repetition ability, with a minimum decontamination rate for NO and NO₂ of 37.4% and 25.84%, respectively. Outdoor experiments show that the photodegradation of NO_x is related to light intensity and temperature. As the light intensity increases the reaction rate increases, and conversely as temperature increases the reaction rate decreases.     

Preparation methods and thermal stability of Ba-Mn-Ce oxide catalyst for NOx-assisted soot oxidation

Manganese oxide-loaded and -doped ceria as well as the corresponding barium-modified oxide catalysts were prepared for soot oxidation in the presence of NOx, and were characterized by using X-ray diffraction, Brunauer-Emmett-Teller and NO temperatureprogrammed oxidation measurements. The activity of catalyst depended strongly on the NO2 production capacity, and the importance of surface nitrates was weakened without heat transfer limitations. The formation of perovskite-type oxides after the high-temperature calcination caused the loss of NOx storage capacity for the Ba-modified catalysts, but did not seem to affect the NO oxidation activity obviously. The addition of barium did not prevent the phase separation of MnOx-CeO2 solid solutions, whereas it inhibited the sintering of oxide crystallites effectively. This, as well as the relatively high surface area, resulted in a small increase in soot oxidation temperature for the thermally aged Ba/Mn-Ce catalyst.     

环氧乙烷热稳定性及杂质对其影响研究

为研究环氧乙烷热稳定性及杂质对其影响,利用C600微量量热仪对环氧乙烷进行热分解试验研究,获得了环氧乙烷分解活化能和绝热条件下到达最大反应速率所需时间(TMRad)等动力学参数.研究了氢氧化钾固体、45％氢氧化钾溶液、三氧化二铁和六水三氯化铁对环氧乙烷热分解特性的影响.结果表明:随温升速率的增加,环氧乙烷热分解起始放热温度逐渐增大;分解活化能E在55～ 90 kJ/mol;环氧乙烷在常温下不易发生热失控;但氢氧化钾固体、45％氢氧化钾溶液、三氧化二铁和六水三氯化铁均对环氧乙烷的热分解有一定程度的影响,使其起始放热温度和最大放热温度都有不同程度的降低,且氢氧化钾溶液和氢氧化钾固体的影响最为明显.     

Indium tin oxide nanoparticles-mediated DNA fragmentation and cell death by apoptosis in human lung epithelial cells

Indium tin oxide (ITO) nanoparticles (NP) have extensive applications in industrial fields, and concerns regarding their potential toxicity in humans and environmental impact have increased. Since exposure to ITO NP is mainly via skin and inhalation, this study was conducted utilizing human lung epithelial (A549) cell line. Cells were exposed to different concentrations of the ITO NP for 24 and 48 hr. A severe cytotoxic response of ITO NP was observed as evident by the (3-4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and neutral red uptake assays after 48 hr exposure. ITO NP significantly reduced glutathione levels with a concomitant increase in lipid hydroperoxide levels, superoxide activity, and reactive oxygen species (ROS) generation after exposure. A significant induction in caspase activity and formation of condensed chromosomal bodies was also observed after ITO NP (10 or 25 µg/ml) exposure. Furthermore, a significant induction in DNA damage was observed by the Comet assay in cells exposed to ITO NP. Our data demonstrate that ITO NP display cytotoxic and genotoxic potential. However, increase in ROS levels and oxidative stress leading to oxidative DNA damage and condensed chromosomal bodies formation, suggests involvement of apotosis. Thus, ITO NP-mediated effects on cell viability indicate cytotoxicity, and therefore, exposures need to be carefully monitored in the industrial sector.     

活性污泥羟氨氧化还原酶粗酶提取及活性测定方法的优化研究

污水生物脱氮过程中N_2O的产生与活性污泥中细菌的羟氨氧化还原酶(Hydroxylamine oxidoreductase,HAO)活性有着密切关系.但目前活性污泥中细菌的HAO提取和活性测定方法尚未建立.本文首先探索了在25℃、酶活性反应液电子受体供体配比1∶1和终止剂选用2 mol·L~(-1)HCl条件下超声或高压破碎细胞法对HAO粗酶活性的影响,结果表明高压破碎比超声破碎获取的粗酶活性高(p0.01).在此基础上,我们进一步优化了高压破碎下压力大小、破碎次数和裂解液用量的参数.粗酶提取液中DNA含量、酶活力及酶比活力结果进行多因素方差分析表明压力大小(50、110或160 MPa)、破碎次数(1、2或3次)和裂解液用量(2、5或10 m L)均对脱氮活性污泥破碎效果、酶活性和比活力有显著影响(p0.01);综合DNA含量、酶活力及酶比活力结果看,110 MPa压力条件下,加5 m L裂解液破碎2次更适合污水生物处理中HAO的提取和活性测定,既节省时间,又能较好的保持酶活性.