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61.
Late season nitrogen fertilization of soybeans: effects on leaf senescence, yield and environment 总被引:3,自引:0,他引:3
Flavio H. Gutiérrez-Boem Javier D. Scheiner Helena Rimski-Korsakov Raúl S. Lavado 《Nutrient Cycling in Agroecosystems》2004,68(2):109-115
Nitrogen demand from soybean seeds during seed filling is very high and has been proposed as the cause of nitrogen remobilization and leaf senescence. Previous research has not shown consistent effects of late season fertilization on seed yield, while its effects on leaf senescence have not been evaluated. Two field experiments were performed to determine the effects of a late season N fertilization on leaf senescence and fall, seed yield and its components, and residual soil nitrate, and to evaluate the potential risk of groundwater contamination. Two rates of nitrogen (50 and 100 kg N ha–1) were applied at the R3 and R5 development stages. Nitrogen fertilization, either at R3 or R5, increased soil nitrate availability during the seed-filling period. Seed yield, seed number and protein content were not affected by N fertilization. The addition of 100 kg N ha–1 produced a small delay of 1–2 days in the leaf fall, and slightly increased seed size (3.6%). Our results suggest that increasing soil N availability during the seed-filling period is not an effective way to delay leaf senescence or to increase seed growth and yield of soybean. Nitrogen fertilization increased the level of residual nitrate in the top soil at one site (the one with lowest seed yield), increasing the risk of nitrate leaching during subsequent fallow. 相似文献
62.
《Journal of the European Ceramic Society》2019,39(16):5197-5203
A Mo(Si, Al)2 based composite was pre-oxidized to establish an alumina scale on the material surface. Thereafter, the corrosion behavior of the composite was examined at 1700 °C for up to 24 h in 95% N2 + 5% H2.The weight change was followed by recording the material weight before and after exposure. The crystalline corrosion products were analyzed with X-ray diffraction (XRD) and the microstructure of the cross sectioned material was characterized using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS).It was shown that AlN and Al5O6N layers developed on top of the pre-oxidized alumina layer and alumina threads develop out from the specimen surface. The accompanied aluminum consumption converts the substrate Mo(Si,Al)2 into Mo5Si3 immediately below the alumina scale to the extent that the Mo5Si3 becomes porous underneath the alumina scale. Corrosion mechanisms are discussed with the support of thermodynamic calculations. 相似文献
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Tomohiro Isogai Kazuhiro Hirooka Tetsuro Tojo Hitoshi Takebayashi Morihiro Saito Minoru Inaba Akimasa Tasaka 《Electrochimica acta》2011,56(12):4425
Metal fluoride added carbon anodes treated by pre-electrolysis were investigated for electrolytic production of nitrogen trifluoride (NF3) in molten NH4F·KF·4HF at 100 °C. The conditions for pre-electrolysis were first optimized using a graphite sheet anode as a model anode. The formation of fluorine-graphite intercalation compounds (fluorine-GICs) with semi-covalent C–F bonds, (CxF)n, on the MgF2 and CaF2 added carbon anode surface was accelerated by pre-electrolysis at potentials less than 4.0 V. Critical current densities (CCD) on the MgF2 added carbon anodes pre-electrolyzed under various conditions were determined, and the highest CCD was 290 mA cm−2 obtained for that pre-electrolyzed at 3.5 V for 500 C cm−2. This anode was successfully used in the electrolysis at 100 mA cm−2 for 290 h and the maximum NF3 current efficiency was 55%. From these results, it was concluded that the metal fluoride added carbon anode treated by pre-electrolysis has a high potential for electrolytic production of NF3 at higher current density. 相似文献
66.
The most of new technologies of reduction of NOx emission, as literature survey (Skalska et al., 2010b) suggests is focused on NOx emission control from power plants and mobile vehicles. Fewer investigations are conducted on the NOx emission abatement from chemical industry. Recently, Chacuk et al. (2007) proposed the model for the nitrous acid oxidation with the use of ozone in gas–liquid contactor. It is well known that not all of NOx can be totally absorbed in water or nitrous/nitric acid solution, as well as ozone is not totally consumed in the acidic liquid. The reaction between ozone and NOx can take place also in the gas phase. The ozone injection into exhaust gas stream followed by absorption was proposed as the NOx emission abatement. The objective of these studies was to propose kinetic model of the process and to determine the rate constants of NOx ozonation in the laboratory scale batch reactor. The process was carried out in the 0.5 dm3 volume batch reactor for different concentrations of NO, and NO2 and varying molar ratios of O3/NO at temperature 25 °C. Gaseous reagents were analyzed using a Fourier Transform Infrared Spectrometer Jasco FTIR-4200. The kinetic model of NOx ozonation process was proposed and rate constants were estimated based on experimental data. 相似文献
67.
This paper reports the ozone generation in pulsed multichannel dielectric barrier discharge. The influence of nitrogen addition (0.1%–10%) on ozone concentration and ozone generation efficiency in nitrogen–oxygen gas mixtures is studied. Results show that adding 0.1% N2 would not seriously increase the ozone production. Meanwhile, 1% N2 content exhibits the highest ozone production efficiency in low SIE (J/L, defined as the ratio of power to gas flow rate) region (0–200 J/L) while adding 0.3% N2 would lead to the highest ozone generation efficiency in high SIE region (300–800 J/L). The increase of ozone production induced by N2 addition is more significant in low SIE region compared with that in high SIE region. At 100 J/L, ozone production efficiency increases 26.9% to 201.6 g/kWh with 1% N2 addition when compared with that in oxygen. At 18 J/L, the observed maximum ozone generation efficiency reaches 252 g/kWh at 1.3 g/Nm3 with 1% N2 addition. An increase of ozone production can be obtained with 0.3%–2% N2 addition in all explored SIE ranges. 相似文献
68.
Air Quality Monitoring Network Design to Control Nitrogen Dioxide and Ozone,Applied in Granada,Spain
Antonio Lozano José Usero Eva Vanderlinden Juan Raez Juan Contreras Benito Navarrete 《臭氧:科学与工程》2011,33(1):80-89
This paper describes a method to design air quality monitoring networks for nitrogen dioxide and ozone and its application in Granada, a city located in Andalusia, southern Spain. The city has a population of 236,988 inhabitants, and traffic is its main source of air pollution. Sampling campaigns with passive diffusion samplers at 88 sites were carried out to obtain information on the pollution distribution in Granada. The average concentrations found for NO2 and O3 were 36.5 μg/m3 and 51.6 μg/m3, respectively. Maximum values of up to 57.1 μg/m3 NO2 were found in Granada city center and O3 reached 77.2 μg/m3 downwind from the emission source. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe. Another sampling campaign with diffusive samplers was carried out in 2007 to determine if the locations of the air quality assessment stations were still representative for their zone. A correction was made in the control network following results of this verification campaign. 相似文献
69.
The effects of sonication time, nitrogen, N2(g), increasing temperature, dissolved oxygen (DO) and titanium dioxide (TiO2) concentrations on the sonodegradation of polyaromatic hydrocarbons (PAHs) in petrochemical wastewaters were investigated. Sonication alone without N2(g), DO and TiO2 provided 80% maximum PAH yields at 2 5°C after 150 min. This PAH yield increased to 89–95% at 60 °C after 150 min sonication. The contribution of DO, N2(g) and TiO2 on the PAH removal was not significant compared to the control. In the presence of HCO3 ?, the degradation of hydrophobic PAH dibenz[a,h]anthracene (DahA)was suppressed in the acceleration step of the sonication. Maximum acute toxicity removal was reached by 30 min N2(g) sparging, 4 mg/L DO and by 0.1 mg/L TiO2 after 150 min sonication. 相似文献
70.
A sludge ozonation process with lab-scale anaerobic/oxic (A/O) system was used to investigate the utilization of the ozonized sludge (OS) supernatant as extra carbon source for denitrification. The optimal ozone dose for the sludge ozonation was 0.2 gO3/gSS. The concentrations of SCOD, BOD, NH3-N and TN in the supernatant increased respectively at this ozone dose. In the meantime, the sludge was significantly reduced. The OS supernatant had negative effect on nitrification because of low pH and alkalinity. After alkalinity adjustment, the A/O with the OS supernatant as the extra carbon source achieved a nitrogen removal rate of 78%, which was very close to the control experiment using glucose (79%). 相似文献