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251.
CuFe-SSZ-13 catalyst showed excellent performance in the selective catalytic reduction of NOx with NH3 (NH3-SCR) for diesel engine exhaust purification. To investigate the effect of preparation methods on NH3-SCR performance, Fe was loaded into one-pot synthesized Cu-SSZ-13 catalysts through solid-state ion-exchange (SSIE), homogeneous deposition precipitation (HDP) and liquid ion-exchange (IE), respectively. Three CuFe-SSZ-13 catalysts showed similar SO2 resistance, which was better than that of Cu-SSZ-13. The improvement was attributed to the protection of Fe species. Hydrothermal stability of three CuFe-SSZ-13 catalysts was significantly different, which was attributed to the state of active species caused by different preparation methods. Compared with the other two catalysts, more active species existed inside the zeolite pores of CuFe-SSZ-13SSIE. During hydrothermal aging, the aggregation of these active species in the pores caused the collapse of catalyst structure, ultimately leading to the deactivation of CuFe-SSZ-13SSIE. In contrast, Fe species was dispersed better on the surface over CuFe-SSZ-13IE, enhancing the hydrothermal stability of catalysts. Consequently, Fe loading effectively improved the resistance of SO2 and H2O over Cu-SSZ-13. For CuFe-SSZ-13, large amounts of active species located inside the zeolite pores are not beneficial for the hydrothermal stability. 相似文献
252.
253.
采用自动连续测量系统,对不同施肥情况下稻田甲烷排放通量进行了监测。结果表明:施肥是影响稻田甲烷排放的重要因素。增施有机肥会导致甲烷排放量增加.应用化肥可降低甲烷排放,有机肥加倍处理,32d甲烷总排放量16.40gCH_4/m ̄2,是化肥加倍处理的1.56倍;常规施肥处理介于两者之间。略高于常规加倍处理。肥料种类对甲烷排放量也有影响。全施有机肥高于有机肥加化肥(1:1)组,施沼渣肥组次之,全化肥组排放量最低,不到全有机肥处理排放量的1/5.有机肥又以施人畜粪的甲烷排放率最高,绿肥次之,沼渣肥和稻草的甲烷排放率最低。有机肥的多级利用是减少稻田甲烷排放的一条重要途径。 相似文献
254.
在济南市区设11个点位,在不同季节采集大气颗粒物,其中五个点位用六级串级式采样器采集飘尘样。样品分析了40多种元素、非金属和有机物,并分析了不同粒径中苯并(a)芘含量。应用富集因子计算并提出富集值大干5(EF>5)为污染富集的论点;摸清了济南大气颗粒物的理化特征及粒径分布规律;用化学质量平衡(CMB_7)法探寻了颗粒物来源。 相似文献
255.
Concentrations of heavy metals (Pb, Zn, Cd, Cu) were determined in soils and vegetables (chrysanthemum, spinach and four cultivars of Chinese cabbage from the area adjacent to a Pb/Zn mine in Shaoxing, Zhejiang province, China, and compared with the Chinese National Standards for Soil Environmental Quality. The accumulation of heavy metals in cabbage cv. Siyuegreen was investigated at different distances from the center of the mine. The vegetable plantation soils were polluted with Pb, Cd, Cu and Zn, especially by Pb and Cd. The levels of Pb and Cd were 20 and 30 times higher than the permitted standards, indicating that this Pb/Zn mining area is unsuitable for agricultural use. Chinese cabbage, chrysanthemum and spinach had different enrichment coefficients. The enrichment coefficient of Cd from soil to roots of chrysanthemum was >80% and from roots to leaves of cabbage cv. Shanghaigreen was >120%. These vegetables were polluted by heavy metals and could not be regarded as safe for human consumption. Environmental accumulation of heavy metals in the vegetable plantation soils was proportional to heavy metal accumulation in vegetables and both were inversely proportional to the distance from the lead/zinc mine. 相似文献
256.
Complexes of fulvic acid on the surface of hematite, goethite, and akaganeite: FTIR observation 总被引:3,自引:0,他引:3
The present work extended our knowledge on the binding and complexation of a fulvic acid (FA) derived from leonardite and the iron oxides (hematite, goethite and akaganeite) by Fourier transform infrared spectroscopy (FTIR). As a prerequisite, the iron oxides were firstly prepared and characterized by transmission electron micrograph (TEM). All iron phases were single and well-described crystalloid. The FTIR data obtained by two different sampling preparation methods gave the consisting evidences that under our experimental conditions the interaction mechanism was to the ligand-exchange involving carboxylic functional groups of the FA and the surfaces sites of both hematite and goethite, while no complexation can be evidenced in the case of akaganeite, only surface adsorption. In general, the binding affinities of the iron oxides with the FA was in the order of hematite>goethite>akaganeite. The present method, although associated with some uncertainties, provided an opportunity to increase the knowledge in the field of the humic chemistry. 相似文献
257.
加油站火灾爆炸故障树分析 总被引:2,自引:0,他引:2
采用安全系统工程的方法,对加油站的火灾爆炸事故进行了故障树分析。通过故障树分析,得出4个最小径集,指明了预防事故发生的可能途径;从而确定出加油站火灾爆炸事故的预防措施,并做出安全检查表,以供现场实施参考。 相似文献
258.
IntroductionThis paper utilizes generalized additive model to explore the potential non-linear relationship between crash frequency and exposure on different types of urban roadway segments.MethodsGeneralized additive models are used to analyze crash frequency data and compared with the commonly used crash rate method and generalized linear models using a five-year crash data set from Houston, Texas.ResultsThe study shows that the relationship between crash frequency and exposure varies by segment type and the linearity may only approximately exist in certain segment types. In addition, the generalized additive modeling results suggest that such relationship curves may not be monotonic. Finally, this study demonstrates that generalized additive models in general provide better flexibility and modeling performance than generalized linear models.Impact on IndustryThe generalized additive model provides a very promising alternative for crash frequency modeling and other safety studies. 相似文献
259.
Xuemin Hao Guanlong Wang Shuo Chen Hongtao Yu Xie Quan 《Frontiers of Environmental Science & Engineering》2019,13(5):77
260.
Gang Yi Xinfei Fan Xie Quan Shuo Chen Hongtao Yu 《Frontiers of Environmental Science & Engineering》2019,13(2):23