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261.
262.
过渡金属催化剂上CO还原NO反应性能的研究 总被引:3,自引:0,他引:3
在一系列负载型过渡金属催化剂上考察了CO-NO和CO-O2的反应性能。结果表明,催化剂的CO-O2反应活性高于CO-NO反应,催化剂表面NO解离是CO-NO反应的速率控制步骤。低温反庆有利于N2O的生成,高温有利于N2的生成。 相似文献
263.
Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO3- was determined in sediment-water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO3- removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m-2 d-1 over 16 d for a 1750-mg NO3-N m-2 addition, and 170 mg N m-2 d-1 over 16 d for a 3500-mg NO3-N m-2 addition. The total N2O-N emissions from the 1750- and 3500-mg NO3-N m-2 additions were 19 and 54 mg N m-2 accounting for 1.1% and 1.5% of the applied NO3-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m-2 d-1 (21 and 32 g N m-2 yr-1) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO3--N m-2 of added nitrate in floodwater, respectively. The total N evolved over 11 d as N2O + N2 was equivalent to 436 and 921 mg N m-2 (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO3- applied to the overlying water increased the rate of NO3- loss and N2O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO3- application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO3- in the river water, reducing the amount of NO3- reaching to offshore areas. 相似文献
264.
Hejingying Niu Dennis Y C Leung Chifat Wong Tong Zhang Mayngor Chan Fred C C Leung 《环境科学学报(英文版)》2014,26(3):555-565
Nitric oxide(NO) is one of the most important air pollutants in atmosphere mainly emitted from combustion source. A biotrickling filter was designed and operated to remove NO from an air stream using bacteria extracted from the sewage sludge of a municipal sewage treatment plant. To obtain the best operation conditions for the biotrickling filter, orthogonal experiments(L9(34)) were designed. Inlet oxygen concentration was found to be the most significant factor of the biotrickling filter and has a significant negative effect on the system. The optimal conditions of the biotrickling filter occurred at a temperature of 40℃, a pH of 8.0 and a chemical oxygen demand of 165 mg/L in the recycled water with no oxygen in the system. The bacteria sample was detected by DNA sequencing technology and showed 93%–98% similarity to Pseudomonas mendocina. Moreover, a full gene sequencing results indicated the bacterium was a brand new strain and named as P. mendocina DLHK. This strain can transfer nitrate to organic nitrogen. The result suggested the assimilation nitrogen process in this system. Through the isotope experimental analysis, two intermediate products(15NO and 15N2O) were found. The results indicated the denitrification function and capability of the biotrickling filter in removing NO. 相似文献
265.
Tree species and temperature change arising from seasonal variation or global warming are two important factors influencing N2O and NO emissions from forest soils. However, few studies have examined the effects of temperatures(5–35℃) on the emissions of forest soil N2O and NO in typical subtropical region. A short-term laboratory experiment was carried out to investigate the influence of temperature changes(5–35℃) on soil N2O and NO emissions under aerobic conditions in two contrasting(broad-leaved and coniferous) subtropical acidic forest types in China. The results showed that the temporal pattern of N2O and NO emissions between the three lower temperatures(5℃, 15℃, and 25℃) and 35℃ was significantly different for both broad-leaved and coniferous forest soils. The effects of temperature on soil N2O and NO emission rates varied between broad-leaved and coniferous forest soils. Both N2O and NO emissions increased exponentially with an increase in temperature in the broad-leaved forest soil. However, N2O and NO emissions in the coniferous forest soil were not sensitive to temperature change between 5℃ and 25℃. N2O and NO emission rates were significantly higher in the broad-leaved forest soil as compared with the coniferous forest soil at all incubation temperatures except 5℃. These results suggest that the broad-leaved forest could contribute more N2O and NO emissions than the coniferous forest for most of the year in the subtropical region of China. 相似文献
266.
目的为太阳辐射试验标准、光老化试验标准修订时正确选择太阳光谱提供依据。方法辨析CIE NO.20,CIE NO.85两种出版物太阳辐射光谱特点,从五个方面对此问题进行探讨,统计这两种太阳辐射光谱带宽辐照度的误差;分析相对空气质量、臭氧与水分、云层光学厚度、地表反射率等因素对太阳辐射光谱辐照度的影响;分析人工辐射光源光谱分布特点,以及它们与太阳辐射光谱的差别;分析当前光老化试验标准对光谱辐照度允差的要求;介绍光老化试验结果间的可比性。结果 CIE NO.85光谱更准确、更细致,但其波长范围较窄,两种光谱辐照度的差别很小,大气环境中许多因素会降低到达地面的光谱辐照度;人工辐射光源光谱与太阳光谱的误差、光老化试验标准中光谱辐照度允差都远大于前述太阳辐射光谱间的误差,标准对太阳光谱波长范围的要求比CIE NO.85光谱宽。结论太阳辐射试验标准、光老化试验标准修订时,仍可选用CIE NO.20光谱作为太阳辐射光谱。 相似文献
267.
268.
针对工业上100℃以下的中低温NO废气处理成本高、脱除困难等问题,以氢氧化钙为吸收剂、过碳酸钠为氧化剂,制备用于烟气半干法同时脱硫脱硝的高活性脱硝剂,并研究了NO去除率的影响因素。当气体总流量为1.2 L/min、O_2体积分数为10%、SO_2质量浓度1 428 mg/m~3、N_2为载气时,适宜的工艺条件为:氧化剂与吸收剂质量比5∶8、高活性脱硝剂中液固比80%、反应温度60℃、入口NO质量浓度670 mg/m~3。在此条件下,NO去除率达到55%以上,SO_2去除率达到100%。 相似文献
269.
D. W. Sweeney A. B. Bottcher K. L. Campbell D. A. Graetz 《Journal of the American Water Resources Association》1985,21(5):867-873
Nitrogen runoff and leaching losses from two tomato and four corn field plots were compared to model predictions by CREAMS, a field-scale model for Chemicals, Runoff, and Erosion from Agricultural Management Systems. The tomato treatments were (1) trickle irrigation with one-half of applied N at preplant and one-half of applied N through the trickle irrigation system and (2) overhead sprinkler irrigation with one-half of applied N at preplant and one-half of applied N in two equal sidedressings. The corn treatments consisted of multiple N applications, minimum tillage, and “conventional” management. Soil type appeared to influence the ability of CREAMS to predict seasonal trends and treatment influences. Model predictions for N losses from tomato and corn treatments that were located on sandy soils often disagreed with measured values. Treatment influences and seasonal trends for N losses from corn treatments that were located on a higher clay content soil were more satisfactorily predicted by CREAMS. Even though model input parameter estimation and measurement techniques may be imperfect, the simulation ability of CREAMS for predicting N leaching losses from systems on deep sands probably needs to be improved. Sensitivity analyses indicated that annual NC3?-N leaching loss predictions were either minimally or not affected by changes in saturated hydraulic conductivity. Input estimations of the fraction of soil pore space filled at field capacity and soil organic matter were inversely related to annual NO3?-N leaching losses, while potential mineralizable N was directly related to yearly N leaching losses. 相似文献
270.
A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F− anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. 相似文献