Selective catalytic reduction of nitrogen oxides over a modified silicoaluminophosphate commercial zeolite

Nitrogen oxides(NO_x:NO,NO_2)are a concern due to their adverse health effects.Diesel engine transport sector is the major emitter of NO_x.The regulations have been strengthened and to comply with them,one of the two methods commonly used is the selective catalytic reduction of NO_xby NH_3(NH_3-SCR),NH_3being supplied by the in-situ hydrolysis of urea.Efficiency and durability of the catalyst for this process are highly required.Durability is evaluated by hydrothermal treatment of the catalysts at temperature above 800°C.In this study,very active catalysts for the NH_3-SCR of NO_xwere prepared by using a silicoaluminophosphate commercial zeolite as copper host structure.Characterizations by X-ray diffraction(XRD),scanning electron microscopy(SEM)and temperature programmed desorption of ammonia(NH_3-TPD)showed that this commercial zeolite was hydrothermally stable up to 850°C and,was able to retain some structural properties up to950°C.After hydrothermal treatment at 850°C,the NO_xreduction efficiency into NH_3-SCR depends on the copper content.The catalyst with a copper content of 1.25 wt.%was the most active.The difference in activity was much more important when using NO than the fast NO/NO_2reaction mixture.     

Impact evaluation of agrotechnologies in watersheds

The special project RAISA (Advanced Researches for Innovation in Agricultural Systems) of the National Research Council of Italy concerns the development of new methodologies for the study and evaluation of the impact of agrotechnologies on the environment. In the project, several trans-disciplinary Units have worked together since 1990. The aim of the project is to define systems, using tools such as remote sensing and Geographical Information Systems, for decision making support in land planning and land use management, with particular attention to groudwater table pollution. The fundamental steps for evaluation of the impact of agrotechnologies on the Po river watershed, 75,000 km² in northern Italy, and Tevere (Tiber) river watershed, 17.169 km² in Central Italy are described here. The study concerns particular areas located in the western part of the Po River plain, where flooded rice is the main crop, and in the central plain of the Tevere basin where the risk of water pollution is considerable, due to small and medium sized swine breeding farms. The aspects considered were water pollution due to mineral nitrogen used to fertilize the rice crop and the nitrogen contained in the waste water from pig farms. For the Po river basin the methodology developed was based on the integration of satellite remote sensing images, and the available cartography, such as topographic and thematic maps, together with the hydrological and the toxicological data of the chemical fertilizers employed, summarized in maps of the groundwater table pollution hazard. A simpler evaluation was obtained in the Tevere river basin: the thematic layers were crossed in bi-directional matrices and the result merged with the map of the territorial distributionof the swine. In both cases the selected information was integrated and processed in Integrated sub-basin scale. The GISs led to the development of a user-friendly system for formalizing our knowledge of the degree of pollution hazard in simple and readable maps.Research supported by National Research Council of Italy, Special Project RAISA, sub-project N. 1 Paper N.     

氮氧化物生态环境中的转化及危害

在对氮氧化物污染引起奶牛亚硝酸中毒事件的调查基础上，通过室内模拟实验研究氮氧化物的转化过程及测定方法，探讨氮氧化物的生态环境中的转化规律，分析其危害途径和机理，研究表明氮氧化物中的二氧化氮遇水迅速反应生成硝酸和亚硝酸，而对生态环境和人畜产生危害。     

氮和磷对铜山源水库优势藻生长影响实验研究

分别研究了N、P等对铜山源水库优势藻类（绿球藻和舟形硅藻）生长的影响。结果表明，当N／P比为25时，绿球藻生长量最高，其限制因子是磷。绿球藻生长最适pH范围为6－8，生长过程中培养基pH没有显著变化。绿球藻和舟形硅藻混合培养时，绿球藻占优，而硅盐浓度对硅藻生长有明显促进作用。     

城市空气中氮氧化物污染预报模型的探讨

本文着重介绍了适合城市空气中氮氧化物预报的五种模型 :统计模型中的MOBILE模式、时间序列分析法、投影回归技术和数值预报模型中的高斯模式及箱模式 .并在此基础上推荐了组合预报 .     

英国城市污水营养物（氮和磷）去除技术研究进展

欧共体“都市污水处理指令”使得英国大部分城市污水必须进行除磷脱氮处理。为此，英国水处理公司已经完成了营养物去除技术研究和开发计划。本文回顾了英国污水营养物去除的历史经验和近期的研究进展。     

煤燃烧过程中影响NO_x转化的因素探讨

利用管式沉降炉对煤粉燃烧过程中的反应温度、初始氧浓度、反应时间、煤的挥发分及含氧量对燃料氮向NOx 转化的影响进行了试验研究 ,摸清了反应的规律 ,找出了影响转化的显著因素。     

Soil N balance as affected by soybean maturity class in the Guinea savanna of Nigeria

Legume–cereal rotation may reduce the fertilizer requirement of the cereal crop and we hypothesize that the benefit depends on the maturity class of the soybean. Field trials were therefore conducted in 1995 in four Guinea savanna sites to monitor the effect of soybean (Glycine max (L.) Merrill) cultivation on the N balance of the soil. In trial 1, an early (TGx1485-1D) and a late (TGx1670-1F) soybean were grown to maturity along with a maize (Zea mays L.) reference plot. In trial 2, six varieties of soybean (early: TGx1485-1D, TGx1805-2E and TGx1681-3F; medium: TGx1809-12E and TGx923-2E; late: TGx1670-1F) were grown to maturity along with a reference maize plot. The total nitrogen (N) content, aboveground N₂ fixed, and N remaining in the stover were higher in the medium and the late varieties than in early varieties. Also, the early varieties had higher nitrogen harvest indices (81–84%) than medium and late varieties (74–79%). From the N balance calculation, it was found that medium and late maturing soybean resulted in an addition of 4.2 kg N ha⁻¹ to the soil, whereas the early maturing varieties resulted in depletion of the soil N reserve by 5.6 kg N ha⁻¹ (P<0.05). On average, among the medium and late varieties, late maturing TGx923-2E resulted in an addition of 9.5 kg N ha⁻¹ to the soil. When the stover was not returned to the field, early soybean resulted in more negative N balance than the medium and late soybean (P<0.05). Therefore, planting an early variety of soybean for one season resulted in net depletion of soil N, even when the soybean residues were returned to the soil and N₂ fixed in the roots and N in the fallen leaf litter were included in the N balance calculations. Contrary to this, planting medium and late soybean for one season resulted in an addition of N to the soil. Therefore, medium and late soybean should be used as a preceding crop in legume–cereal rotation, if possible, to minimize or avoid depletion of soil N by early varieties of soybean.     

多级高浓度自浓缩活性污泥法脱氮除磷研究

随着经济的发展和人们环境意识的提高,对N,P的控制越来越受到重视.在此简要介绍了“多级高浓度自浓缩活性污泥法脱氮除磷”新工艺.新工艺可在基本不增加投资、对二沉池基本没有影响的情况下,使传统活性污泥法工艺在BOD,COD保持较高的去除率的同时,具备良好的脱氮、除磷功能,较适合采用传统活性污泥法工艺的污水厂的改造.