实际工况下内河航行船舶NO_x排放测试与分析

为获得NO_x的排放特征,利用便携式排放测试系统(PEMS)对7艘京杭运河中航行的内河船舶进行了实际工况下的排放测试。测量结果表明:进、离港工况下NO和NO_2的浓度波动明显,而在巡航工况下NO浓度保持稳定且处于较高的排放水平。巡航工况下NO的基于时间的平均排放因子分别是进港和离港工况排放因子的3.22倍和1.74倍。而NO_2离港工况下的平均排放因子分别是巡航工况和进港工况下的平均排放因子1.18倍和1.96倍。受到航行距离的影响,进港工况下NO和NO_2基于距离的平均排放因子高于其他2个工况下的排放因子。当发动机处于高转速时,NO的排放因子最高,而NO_2则在中转速下的排放因子最高。     

机动车细微颗粒物及气体污染物排放的隧道实测研究

利用隧道实验法对澳洲Vulturestreet公交专用隧道的细微颗粒物和气体污染物进行连续4d实测,分析了自然通风和纵向通风下隧道内NOX、细微颗粒物数目浓度以及细微颗粒物粒度分布特征。结果表明,隧道内细微颗粒物粒径谱呈双峰分布,峰值区段细微颗粒物粒径分别在19～25、70～105nm,判定为低硫柴油公交车和CNG公交车共同作用结果。隧道内NO2/NOX比值与NOX具有很强的相关性(R2=0.8320),当NOX大于1.000×10-6时,NO2/NOX渐进于(0.088±0.001),同时,NOX与细微颗粒物数目浓度、细微颗粒物总体积(VFP)呈明显的线性相关关系。柴油公交车和CNG公交车的混合条件下,细微颗粒物数目浓度、NOX平均排放因子分别为(2.48±1.53)×1014个/km、(12.8±5.1)g/km,柴油车和CNG公交车细微颗粒物数目浓度排放因子和NO排放因子没有明显差异。     

煤化工企业火炬NO_x排放的模拟燃烧实验

针对煤化工企业火炬气燃烧特点,设计了一套模拟燃烧装置,分别研究液化气添加量及燃烧温度对NO x的影响,并对火炬系统NO x的排放系数进行核算。结果表明,火炬系统NO x排放浓度和排放量随液化气添加量的增加而增大;同时研究发现,NO x与燃烧温度之间成正比关系,即温度升高有利于NO x的产生。根据核算结果,火炬系统NO x排放系数在0.099~0.185 kg/t之间,平均为0.139 kg/t。     

SCR脱硝在燃煤电厂超低排放中的适用性分析

通过流场模拟、化学动力学计算、并结合物理实验,全过程研究SCR反应器内烟气组分的动量/能量/质量传递及脱硝还原反应,计算在不同入口NO_x浓度下SCR出口NO_x和氨逃逸的排放量及空间分布,确定SCR在NO_x超低排放要求下的适用范围。研究结果表明,为实现NO_x50 mg·Nm~(-3)并同时满足NH_32.28 mg·Nm~(-3)的要求,2层SCR催化剂可处理的入口烟气NO浓度上限为240 mg·Nm~(-3),而3层SCR催化剂则可对NO浓度380 mg·Nm~(-3)的烟气实施超低排放治理,为合理选择SCR超低排放设计方案提供了数据支撑。     

厦门市空气污染的空间分布及其与影响因素空间相关性分析

基于空间信息技术、克里格插值与空间相关矩阵,研究厦门市SO2、NO2、PM10和PM2.5污染浓度空间分布特征。通过提取人口密度、道路面积比重、建设用地比重、地表温度及植被指数等空气污染影响因素的空间分布数据,划分研究区为生态区、居住区与工业区,定量评价了污染物浓度与影响因素的空间相关性,并识别出各污染物的主要影响因素。结果表明:污染浓度分布总体上呈现出工业区-居住区-生态区递减的空间特征,其主要受工业排放和机动车排放的影响;SO2与除地表温度外的其他影响因数均有较强空间相关性,PM10和PM2.主要与道路面积比重、建设用地比重具有较强相关性,NO2则与道路面积比重的相关性最强,污染浓度与影响因数空间相关性呈现出工业区-居住区-生态区递增趋势;与按照行政区的划分相比,工业区、居住区、生态区的划分显得更为合理。     

硝基氧化剂废水处理研究

用钠盐（Na2CO3和NaHCO3）作为和剂去除硝基氧化剂废水中HNO3;用尿素、Na2SO3去除NO2^-、NO3^-;加入适量的沉淀剂、络合剂、絮凝剂、助凝剂去除废水中的F^-和PO4^3-;并对处理pH值、各种药剂浓度及处理时间作了讨论,得出了最佳条件,处理后的出水达到国家污水排放标准。     

紧凑型SCR催化剂在船舶柴油机上的脱硝性能

为了减小SCR系统在船舶上的占用空间,在YC6A220C型高速船舶柴油机实验平台上进行了紧凑型蜂窝状V_2O_5-WO_3/TiO_2催化剂在高空速下的脱硝实验研究,研究了不同氨氮比、空速、温度和NO浓度对脱硝性能的影响。实验结果表明:在氨氮比为1、空速35 000 h-1、温度250~360℃、NO浓度约205×10~(-6)~600×10~(-6)时,催化剂对柴油机尾气的脱硝效率都在80%以上,满足Tier-III对高速船舶柴油机的NOx排放标准;在氨氮比为1、空速35 000 h~(-1)、温度360℃时,催化剂对NO浓度达到1 300×10~(-6)和1 900×10~(-6)的脱硝效率都在80%以上,达到Tier-III对中、低速柴油机的NOx排放标准。     

不同电子受体对聚磷菌吸磷性能的影响研究

采用人工配水,在厌氧/好氧交替运行的序批式活性污泥反应器(SBR)中,富集了全菌数量80%以上的聚磷菌(Candi-datus Accumulibacter Phosphates)。以此为基础,研究了O2及不同浓度NO3--N、NO2--N对聚磷菌吸磷的影响。结果表明,在一定的条件下,聚磷菌可以NO3--N和NO2--N为电子受体进行缺氧吸磷;NO3--N浓度对聚磷菌的吸磷速率影响很小;聚磷菌可以低质量浓度NO2--N(≤40mg/L)为电子受体,但不能以高质量浓度NO2--N(≥80mg/L)为电子受体,而且高浓度NO2--N对聚磷菌吸磷产生抑制甚至对细菌本身存在毒害;NO2--N为电子受体时,其抑制浓度和污泥本身以及外界条件都存在很大的关系,各个研究结论不尽相同,其影响过程有待进一步的探讨。     

溶胶-凝胶法制备颗粒状催化剂低温SCR脱硝性能

采用溶胶凝胶法制备了Mn-Ce/Ti O2催化剂,并将其用于低温NH3选择催化还原NO的反应(NH3-SCR),考察了反应温度、空速、氧气浓度、氮氧化物浓度和氨氮比等反应条件对催化剂性能的影响。结果表明,NO入口浓度为800~1 600 mg/m3时,催化剂活性受NO初始浓度的影响较小。反应温度和氨氮比对NO转化率影响显著,100~150℃温度范围内,NO转化率随温度升高快速上升;当[NH3]/[NO]1.1时,随着[NH3]/[NO]的增加,NO转化率很快上升。反应体系中适当的O2浓度可促进NO还原为N2。空速大于10 000 h-1时,NO转化率随着空速的增大而降低。     

用活性填料催化氧化-硝酸吸收法脱除氮氧化物的研究

为了提高硝酸吸收氮氧化物的效率,对活性填料催化氧化-硝酸吸收NOx进行了研究.结果表明:活性填料能明显提高NOx的吸收效率;当NOx中NO2体积百分含量增加,其吸收效率增加;随进气浓度和液气比的增大,NOx吸收效率增加;随NO2浓度的增加,NO的吸收效率先增加后减少,在NO/NO2为3时,NO吸收效率最高;随NO的增加NO2的吸收效率先增加后减少,在NO/NO2为0.6～1之间,NO2的吸收效果较好.     

Trends in atmospheric sulfur and nitrogen species in the eastern United States for 1989–1995

Emission reductions were mandated in the Clean Air Act Amendments of 1990 with the expectation that they would result in major reductions in the concentrations of atmospherically transported pollutants. This paper investigates the form and magnitude of trends from 1989 to 1995 in atmospheric concentrations of sulfur dioxide, sulfate, and nitrogen at 34 rural sites in the eastern US. Across all sites, there is strong evidence of statistically significant declining trends in sulfur dioxide (median change of -35%) and sulfate concentrations (median change of -26%). In general, trends in nitrogen concentrations were not as pronounced (median change of -8%) as trends in the sulfur compounds. A regional estimate of trend for a cluster of sites in the Ohio River valley showed close correspondence between declining sulfur dioxide concentrations (-35%) and changes in sulfur dioxide emissions (-32%) in this region.     

Deposition of particulate matter in diffusion tube samplers for the determination of NO2 and SO2

The applicability of tube-like diffusion samplers for the determination of ambient air concentrations of sulfur dioxide and nitrogen dioxide was evaluated. The diffusion tubes were made from polyethylene and triethanolamine was used as an absorbent. Artifacts due to the deposition of gaseous or particulate compounds to the tube walls were considered. With respect to sampling of nitrogen dioxide no interference by the tube walls could be observed. The determination of sulfur dioxide was strongly biased by the collection of particulate sulfate at the entrance part of the tube and along the tube walls. This effect leads to a large overestimation of the average air concentrations compared with fluorescence monitors.     

The Characterization of Ozone,Sulfur Dioxide,and Nitrogen Dioxide for Selected Monitoring Sites in the Federal Republic of Germany

Ambient ozone, sulfur dioxide, and nitrogen dioxide data collected at 11 rural gaseous air pollution monitoring stations located throughout the Federal Republic of Germany (FRG) were characterized to provide a basis for investigating the effect these air pollutants may have on forest decline. For any given year, with the exception of the Waldhof site, the ozone monitoring sites did not experience more than 50 occurrences of hourly mean concentrations equal to or above 0.10 ppm. In most cases, the number of occurrences equal to or above 0.10 ppm at the FRG ozone monitoring sites was below the number experienced at a rural forested site located at Whiteface Mountain, New York. Several of the FRG monitoring sites experienced a large number of occurrences of hourly mean ozone concentrations between 0.08 and 0.10 ppm. Hof, Selb, Arzberg, and Waldhof experienced several occurrences of elevated levels of sulfur dioxide concentrations. The nitrogen dioxide 24-h mean concentrations were low for all sites. Because the 24-h mean data may mask the occurrence of a few high concentration events, it is not known if any of the sites that monitored nitrogen dioxide experienced short-term elevated concentrations. To gain further insight into the possible effect of pollutant mixtures on vegetation, future efforts should involve characterizing the timing of multi-pollutant exposures.     

Sensitivity of nitrogen dioxide concentrations to oxides of nitrogen controls in the United Kingdom

There is a possibility of further controls on emissions to the atmosphere of nitrogen oxides to meet air quality objectives in the UK. Data in the National Air Quality Archive were used to calculate the likely sensitivity of hourly concentrations of nitrogen dioxide in ambient urban air to changes in the total oxides of nitrogen. Since the role of atmospheric chemical reactions is to make the response non-linearly dependent on the emissions control, we seek to establish the magnitude and sign of the effects that this non-linearity might cause. We develop a quantitative approach to analysing the non-linearity in the data. Polynomial curve fits have been developed for the empirical ratio NO₂ : NO_x (the ‘yield’). They describe nitrogen dioxide concentrations using total oxides of nitrogen. The new functions have the important feature of increased yield in winter episodes. Simpler functions tend to omit this feature of the yields at the highest hourly concentrations. Based on this study, the hourly nitrogen dioxide objective in the UK may require emissions control of no more than ≈50% on total oxides of nitrogen at the most polluted sites: other sites require less or even no control.     

Gas Dilution Apparatus for Preparing Reproducible Dynamic Gas Mixtures in any Desired Concentration and Complexity

A portable gas dilution apparatus has been constructed by which reproducible known mixtures of the common air pollutants added to carbon filtered air can be prepared in any desired quantity, complexity, and concentration. Sulfur dioxide mixtures with and without the addition of nitrogen dioxide and/or ozone have been analyzed by the conductimetric, titrimetric, turbidimetric, and colorimetric methods. Excellent analytical agreement with the concentrations obtained from the volumes of sulfur dioxide, nitrogen dioxide, hydrogen sulflde, and air that are mixed has been shown by all these methods when an efficient absorber is used though the titrimetric method tended to give slightly low results. Some common absorbers show reduced efficiency in absorbing some of the gases. Nitrogen dioxide determinations by the Saltzman method are not significantly affected by the addition of sulfur dioxide to the nitrogen dioxide-air mixtures. A modification of the Saltzman reagent, due to Lyshkow, was tested. It accelerates the rate of color development and should be useful in the automatic nitrogen dioxide analyzer. The determination of hydrogen sulfide is not affected by the presence of nitrogen dioxide in the gas mixture but sulfur dioxide increases the sulfide reading by about 5-15% while ozone decreases the reading.     

Contaminant Concentrations in the Atmosphere of Los Angeles County

Sampling for nitrogen and sulfur dioxides was initiated at several National Air Sampling Network stations in 1959 using a sampler developed for that purpose. In 1961 the Gas Sampling Network was expanded to its maximum of 49 stations. Sampling equipment and collecting solutions are supplied and chemical analyses performed by the network laboratories. Sampling and analysis procedures are described briefly. Average and maximum 24-hour concentrations of nitrogen dioxide and sulfur dioxide observed at 48 stations during 1961-1963 are presented.     

Phenolic compounds content in Pinus halepensis Mill. needles: a bioindicator of air pollution

Foliar phenol concentrations (total and simple phenols) were determined in Aleppo pine (Pinus halepensis Mill.) needles collected in June 2000, from 6 sites affected by various forms of atmospheric pollutants (NO, NO(2), NO(x), O(3) and SO(2)) monitored during two months. Results show an increase in total phenol content with exposure to sulphur dioxide and a reduction with exposure to nitrogen oxide pollution. p-Coumaric acid, syringic acid and 4-hydroxybenzoic acid concentrations increase with exposure to nitrogen oxide pollution, whereas gallic acid and vanillin decrease in the presence respectively of sulphur dioxide and ozone. This in situ work confirms the major interest of using total and simple phenolic compounds of P. halepensis as biological indicators of air quality.     

Photochemical Reactivities of Paraffinic Hydrocarbon-Nitrogen Oxide Mixtures Upon Addition of Propylene or Toluene

Effects associated with photochemical air pollution were measured during irradiation of n-butane-nitrogen oxide or n-butane-ethane-nitrogen oxide mixtures, with small amounts of propylene or toluene added. The effects measured including nitrogen dioxide and oxidant dosages, yields of formaldehyde and peroxy-acetyl nitrate, and eye irritation response. The results obtained clearly show that beneficial effects result from selective changes in hydrocarbon composition as well as from reduction of total hydrocarbon concenfration. Exclusion of olefins and alkylbenzenes was highly effective in reducing oxidant dosage, formaldehyde and peroxyacetyl nitrate concentrations, and eye irritation response. The only penalty was a modest increase in nitrogen dioxide dosage. A large reduction in nitrogen oxide concentration reduced nitrogen dioxide dosage and eye irritation response, but with the penalty of a large increase in oxidant dosage. The desirability of preferentially reducing olefins and alkylbenzenes rather than paraffinic hydrocarbons, acetylene, and benzene is strongly supported by this study. Research and development efforts should be directed toward preferential hydrocarbon control by mechanical or catalytic control     

Street-level concentrations of nitrogen dioxide and suspended particulate matter in Hong Kong

The concentrations of respirable suspended particulates (PM₁₀), fine suspended particulates (PM_2.5) and nitrogen dioxide (NO₂) were measured in various locations over the territory of Hong Kong. In order to study the contributions of these pollutants from motor vehicles and their characteristics, the attention was focused on the roadside, street-level concentrations. A statistical analysis of the sampling results was conducted to obtain general characteristics of the roadside particulate and nitrogen dioxide pollution and to investigate the effects of traffic volume and meteorological factors on the pollution levels. High correlation coefficients are found between PM₁₀, PM_2.5 and NO₂ concentration.     

Rural concentrations of nitrogen dioxide pollution throughout Wales

Monitoring of nitrogen dioxide was carried out at over 50 rural sites in Wales throughout 1986. All sites were chosen so as to be remote from any local sources of NO(2) and the values obtained were deemed to be minimum values for the different regions. Measurements were made using a diffusion tube technique which aimed to give mean concentrations of NO(2) for 2-week exposure periods. The results obtained have been used to generate pollution maps to show mean monthly levels of NO(2) for rural environments throughout Wales. It is apparent that levels of NO(2) are generally higher during the winter months. In addition, annual mean concentrations of the pollutant are greatest in the north-eastern and south-eastern parts of Wales with the lowest levels being found along the western coast. The work marks the completion of the first national survey of nitrogen dioxide pollution in Wales. The data are discussed in terms of the potential threat rural concentrations of NO(2) pose to crops and natural vegetation.