Effect of dry deposition of NOx and SO2 gaseous pollutants on the degradation of calcareous building stones

A laboratory-based atmospheric flow chamber, using realistic presentation rates of SO₂, NO and NO₂ pollutants directed to various dry and wetted surfaces, has been employed to quantify the effects of the individual pollutants and the role of ozone as an oxidant. For the individual pollutant gases reacting with stone surfaces coming to equilibrium with 84% relative humidity (r.h.), chemical reaction in the presence of a moisture film proceeds and the extent of this reaction is related to pollutant gas solubility in the moisture film, i.e. SO₂ > NO₂ > NO. After dissolution in the moisture film, the pollutant gases are oxidized in the presence of catalysts associated with the stones. The additional presence of ozone promotes oxidation of the pollutant gases and thus their reaction with the stones. For SO₂ pollutant, oxidation in the gas phase is not significant compared with that in the moisture film, with enhanced oxidation in the presence of catalysts. Ozone increases oxidation of NO and NO₂ pollutant gases in the gas phase and moisture film; however, the oxidation of SO₂ in the moisture film is more significant than that of NO or NO₂. Wetting of the stone surfaces, in the absence of ozone, reveals the consistently greatest chemical reaction with SO₂ compared with NO and NO₂, which is related to SO₂ solubility, oxidation in the presence of catalysts and production of sulphuric acid. Generally similar behaviour is evident of NO and NO₂, but NO shows a reduced extent of chemical reaction, implying that its oxidation in surface water, in the presence of catalytic species, is slow and hence the reactants are lost in the form of run-off. In the additional presence of ozone, the SO₂ pollutant gas gives rise to enhanced chemical reaction, whereas both NO and NO₂ show lower extents of chemical reaction than for the dry stones. This arises from the relatively slow conversion of N₂O₅ in the liquid phase to nitric acid, allowing loss of reactants in run-off.     

An assessment of the luminol chemiluminescence technique for measurement of NO2 in ambient air

The detection of NO₂ by its chemiluminescent reaction with luminol is a rapid and sensitive means of measuring atmospheric NO₂. However, testing and field use of a commercial NO₂ monitor employing this detection scheme have shown that several corrections are necessary in order to obtain accurate NO₂ data at low concentrations. In use aboard aircraft, the NO₂ data must be corrected for zero offset, altitude (i.e. pressure), nonlinearity of response, and interferences from ozone and PAN. Detector response is dependent on the age of luminol reagent solution. This paper describes the tests performed to determine correction factors, the algorithms and order of precedence for applying the corrections, and other observations regarding detector performance.     

Air pollutant concentrations in Varanasi,India

This study reports the diurnal patterns in the concentrations of ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂) and total suspended particulate matter (TSP) in the urban atmosphere of Varanasi city in India during 1989. The city was divided into five zones and three monitoring stations were selected in each zone.Ambient concentrations of NO₂ and SO₂ were maximum during winter but ozone and TSP concentrations were highest during summer. The measured maximum concentrations (2-h average) were 150 and 231 μg m⁻³ (0.078 and 0.086 ppm) for NO₂ and SO₂, respectively, for the winter season. Ozone and TSP concentrations reached a maximum of 160 (0.08 ppm) and 733 μg m⁻³, respectively, in the summer. NO₂ and SO₂ concentrations peaked in the morning and evening. Peak concentrations of O₃ occurred in the afternoon, generally between noon and 4 p.m. Maximum concentrations of O₃, NO₂, SO₂ and TSP were measured in zones I and II, and minimum in zone V.     

燃煤电厂颗粒物中硫酸根与硝酸根离子的转化规律

燃煤电厂排放的颗粒物可以分为可凝结颗粒物（condensable particle matter,CPM）和可过滤颗粒物（filterable particle matter,FPM）.通过分析7个超低排燃煤电厂的湿法脱硫（wet flue gas desulfurization,WFGD）进出口和湿电除尘（wet electrostatic precipitator,WESP）出口烟气中CPM和FPM的SO₄^2-和NO₃^-浓度,揭示了这2种典型水溶性离子在烟道内的变化规律与转化特征.结果表明在WFGD前后,CPM中的SO₄^2-和NO₃^-浓度呈降低趋势,其降低率范围分别为43.12%~86.84%和17.99%~91.58%,而FPM中SO₄^2-和NO₃^-浓度呈增大趋势.在WESP前后,CPM中SO₄^2-和NO₃^-浓度呈增大趋势,增长率范围分别为21.05%~424.65%和13.51%~298.37%,而FPM中SO₄^2-和NO₃^-浓度呈减小趋势.在WFGD中,随着烟气温度降低和湿度增加,部分CPM会通过冷凝和团聚作用进一步转化为FPM;在WESP中,由于烟气一直处于低温、高湿的条件,烟气中存在的SO₂与NO₂会结合水蒸气发生氧化还原反应,进而经过协同作用促进CPM中SO₄^2-和NO₃^-的生成.     

An online monitoring system for atmospheric nitrous acid (HONO) based on stripping coil and ion chromatography

A new instrument for measuring atmospheric nitrous acid(HONO) was developed,consisting of a double-wall glass stripping coil sampler coupled with ion chromatography(SC-IC).SC-IC is featured by small size(50 × 35 × 25 cm) and modular construction,including three independent parts:the sampling unit,the transfer and supporting unit,and the detection unit.High collection efficiency(> 99%) was achieved with 25 μmol/L Na2CO3 as absorption solution even in the presence of highly acidic compounds.This instrument has a detection limit of 8 pptv at 15 min time resolution,with a measurement uncertainty of 7%.Potential interferences from NOx,NO2+SO2,NO2+VOCs,HONO+O3,HNO3,peroxyacetyl nitrite(PAN) and particle nitrite were quantified in laboratory studies and were found to be insignificant under typical atmospheric conditions.Within the framework of the 3C-STAR project,inter-comparison between the SC-IC and LOPAP(long path liquid absorption photometer) was conducted at a rural site in the Pearl River Delta.Good agreement was achieved between the two instruments over three weeks.Both instruments determined a clear diurnal profile of ambient HONO concentrations from 0.1 to 2.5 ppbv.However,deviations were found for low ambient HONO concentrations(i.e.< 0.3 ppbv),which cannot be explained by previous investigated interference species.To accurately determine the HONO budget under illuminated conditions,more intercomparison of HONO measurement techniques is still needed in future studies,especially at low HONO concentrations.     

Uncertainties in the Norwegian emission inventories of acidifying pollutants and volatile organic compounds

The uncertainties in the Norwegian emission inventory data for SO₂, NO_x, NH₃ and non-methane volatile organic compound (NMVOC) have been estimated based on expert judgements of uncertainties in input data and stochastic simulations. The SO₂ inventory is uncertain by about 4%, the NO_x inventory by about 12% and the NMVOC and NH₃ inventories by about 20%. Several possible systematic errors were identified; the SO₂ inventory is most likely overestimated, while the NH₃ and NMVOC inventories can be underestimated. Domestic shipping (for SO₂ and NO_x), crude oil loading (for NMVOC) and manure (for NH₃) are the sources that are most important for the overall uncertainty. These findings indicate that the inventory methodologies can be improved, leading to changes in the whole time series (recalculations). The robustness of emission obligations formulated as emission ceilings and percentage reductions have been compared with respect to uncertainties in input data. The formulation of obligations as emission ceilings is not very robust for any methodological improvements influencing the end year estimates. Relatively, small changes in the emission estimates can mean that obligations apparently are met without measures or that obligations hardly can be met at all. Obligations formulated as percentage reductions are on the other hand more robust, except when recalculations unequally affect the base and end year.     

Laboratory tests of KI and alkaline annular denuders

Annular denuders coated with KI and with alkaline solutions have been tested for their ability to remove atmospheric pollutants including ozone, NO₂, SO₂, formaldehyde, methyl nitrate and peroxyacetyl nitrate. Tests were carried out at flow rates of 0.4–2.0 ℓ min⁻¹, using particle-free ambient air as well as purified air to study the effect of atmospheric CO₂ on alkaline denuder performance. Denuders coated with KI were efficient in removing O₃, NO₂, SO₂ (> 95%) and PAN (84±3%) but not methyl nitrate (44%) and formaldehyde (<5%). Selective removal of PAN from NO₂, and vice versa, could be obtained with annular denuders coated with NaOH, which removed 100% PAN and ⩽15% NO₂, and with alkaline guaiacol, which removed ⩾99% NO₂ and ⩽6% PAN.     

Trends in ground level ozone concentrations in the European Union

Following the Council Directive 92/72/EEC on air pollution by ozone the Member States of the European Union have to inform the European Commission on ozone concentrations and exceedances of threshold values within their territory. Using the available information covering the period of 5 years (1994–1998), the data has been analysed for a possible trend in statistical parameters (50- and 98-percentiles) and number and severity of exceedances. Time series are relatively short but the data suggest that there might be a small increasing trend in the 50 percentile values. The ozone peak values, expressed as 98-percentile values or as number of exceedance days tend to decrease. However, these conclusions must be interpreted carefully as on the short time scales considered here meteorological variations and inter-annual changes may play an important role. The decrease in peak values is most likely caused by the decrease in European ozone precursor emissions since 1990; insufficient data is available to explain the increasing 50-percentile values. Possible explanations are an increase in tropospheric ozone background values caused by a world-wide increase in CH₄, CO and NO_x emissions or a reduced ozone titration by reduced NO_x emissions on the local scale. The data submitted under the ozone directive is insufficient to provide firm conclusions on this point.     

Climate and air quality-driven scenarios of ozone and aerosol precursor abatement

In addition to causing domestic and regional environmental effects, many air pollutants contribute to radiative forcing (RF) of the climate system. However, climate effects are not considered when cost-effective abatement targets for these pollutants are established, nor are they included in current international climate agreements. We construct air pollution abatement scenarios in 2030 which target cost-effective reductions in RF in the EU, USA, and China and compare these to abatement scenarios which instead target regional ozone effects and particulate matter concentrations. Our analysis covers emissions of PM (fine, black carbon and organic carbon), SO₂, NO_x, CH₄, VOCs, and CO. We find that the effect synergies are strong for PM/BC, VOC, CO and CH₄. While an air quality strategy targeted at reducing ozone will also reduce RF, this will not be the case for a strategy targeting particulate matter. Abatement in China dominates RF reduction, but there are cheap abatement options also available in the EU and USA. The justification for international cooperation on air quality issues is underlined when the co-benefits of reduced RF are considered. Some species, most importantly SO₂, contribute a negative forcing on climate. We suggest that given current knowledge, NO_x and SO₂ should be ignored in RF-targeted abatement policies.     

Field study investigations of the impact of shape,size and orientation on dry deposition induced corrosion of galvanized steel

A controlled field study was conducted at Research Triangle Park, NC, to determine how shape, size and orientation of galvanized steel structures affect (1) dry deposition of SO_x and NO_x compounds and (2) dissolution of Zn corrosion products resulting from such deposition. Thirteen structures of various shapes, sizes and orientations were exposed to dry deposition only for 100 weeks, during which they were rinsed with deionized water every 2 weeks and the rinses were analysed for Zn, Ca, and their ionic contents. The rinse data are consistent with size, orientation and exposure history affecting dry deposition of SO²⁻₄ precursors such as SO₂. Dry deposition of precursors of surface NO⁻₃, including HNO₃, is affected by structure size. A model regression equation is presented that shows that Zn dissolution can be explained in terms of the SO⁻²₄ and NO⁻₃ rinse concentrations. The experimental results suggest that there is likely to be some error associated with extrapolating galvanized steel test panel results to actual structures.     

海南省背景区域臭氧及其前体物污染特征

基于2019年五指山背景点、海口市和三亚市的环境空气自动监测数据和气象观测资料,分析了海南省背景区域和重点城市O₃及其前体物NO₂污染特征;结合挥发性有机物（VOCs）在线监测数据,分析了五指山背景点VOCs的时间变化规律、O₃浓度高值月份O₃及其前体物VOCs和NO_x的污染特征以及VOCs的臭氧生成潜势（OFP）.结果表明,O₃是影响五指山背景点空气质量的关键污染物,五指山背景点O₃日最大8 h浓度平均值与海口市和三亚市显著相关.背景点NO₂月均浓度水平显著低于城市点,然而背景点和城市点O₃月均浓度水平和变化趋势高度一致.背景点O₃变化与风向密切相关,春夏季偏南风频率较高,O₃浓度相对较低;秋冬季以东北风为主,易受内陆污染输送影响,O₃浓度较高.五指山背景点春夏季VOCs体积分数低于秋冬季,但对应的OFP高于秋冬季;其中异戊二烯夏季体积分数显著高于秋冬季,且其夏季体积分数占总挥发性有机物的比例最高,对应的OFP贡献率可达70%以上,O₃则表现出秋冬季显著高于夏季的特征.11月O₃高浓度时段乙炔和芳香烃的体积分数较清洁日出现较大上升,同时其对应的OFP显著上升.VOCs优势物种和OFP主要贡献物种的分析结果表明,O₃高浓度时段机动车尾气和油气挥发排放源对五指山背景点VOCs的化学组成和OFP有重要贡献.     

南昌市固定燃烧点源大气污染物排放清单及特征

大气污染物排放清单是了解区域污染物排放特征、准确模拟空气质量的重要资料,而工业点源是大气污染的重点排放源.通过收集相关活动水平信息和合理的排放因子,采用"自下而上"的方法建立了南昌市2014年点源大气污染物排放清单.结果表明,SO_2、NO_x、CO、PM_(10)、PM_(2.5)和VOC排放总量分别为29576.2、17115.1、25946.6、4689.4、922.9和1190.4 t,其中,金属炼制行业对SO_2、CO和VOC的贡献最高,分别占37.75%、30.59%和38.45%;火电行业是NO_x的主要来源,其贡献率为47%;水泥等建材制造行业对PM_(10)和PM_(2.5)排放贡献最高,分别为26%和25%.根据排放源污染物排放量及地理坐标信息,建立了0.4 km×0.4 km的污染物排放量空间分布特征图,结果表明,南昌市大气污染物排放较为集中,青山湖区北部和新建区北部是SO_2、NO_x、CO和VOC的主要排放区,而PM_(10)和PM_(2.5)的排放量相对分散,并在安义县出现排放高值区.通过将计算结果与统计数据结果进行对比,了解所估算清单的准确程度.对SO_2和NO_x的计算值和统计值进行统计分析,结果显示,NMB(标准化平均偏差)和NME(标准化平均误差)值均小于50%,清单计算精度较高.同时,为了解清单数据质量,对清单的不确定性进行定量分析,结果显示,SO_2和VOC不确定性较低而PM_(10)和PM_(2.5)的不确定性相对较高,清单整体不确定性与其他研究结果相差不大.建议后期研究可以从提升基础数据质量和建立具有区域代表性的排放因子数据库着手,从而减小排放量的不确定性,获得精准可靠的大气污染物清单并应用于空气质量模型预报等更深入的研究.     

Ambient air quality trends and driving factor analysis in Beijing, 1983-2007

The interaction between pollution sources change and implementation of air pollution control measures was the main driving factor that caused the variation in air quality.     

Effectiveness of national air pollution control policies on the air quality in metropolitan areas of China

Understanding the effectiveness of national air pollution controls is important for control policy design to improve the future air quality in China. This study evaluated the effectiveness of major national control policies implemented recently in China through a modeling analysis. The sulfur dioxide （SO2） control policy during the llth Five Year Plan period （2006-2010） had succeeded in reducing the national SO2 emission in 2010 by 14% from its 2005 level, which correspondingly reduced ambient SO2 and sulfate （SO42-） concentrations by 13%-15% and 8%-10% respectively over east China. The nitrogen oxides （NOx） control policy during the 12th Five Year Plan period （2011-2015） targets the reduction of the national NOx emission in 2015 by 10% on the basis of 2010. The simulation results suggest that such a reduction in NOx emission will reduce the ambient nitrogen dioxide （NO2）, nitrate （NO3-）, 1-hr maxima ozone （03） concentrations and total nitrogen deposition by 8%, 3%-14%, 2% and 2%--4%, respectively over east China. The application of new emission standards for power plants will further reduce the NO2, NO3-, 1-hr maxima 03 concentrations and total nitrogen deposition by 2%-4%, 1%-%, 0-2% and 1%-2%, respectively. Sensitivity analysis was conducted to evaluate the inter-provincial impacts of emission reduction in Beijing-Tianjin-Hebei and the Yangtze River Delta, which indicated the need to implement joint regional air pollution control.     

A study of Taipei ozone problem

A high level of ozone has been a serious problem in Taipei. At one station there were concentrations of hourly O₃ 127 and 60 time > 120 ppbv in 1986 and 1987, respectively. The diurnal O₃ variation is mainly governed by a single-peaked (SP) pattern with a major peak near noontime, and a double-peaked (DP) pattern with a primary peak near noontime and a secondary peak in the early morning. The analyses of observed NO_x, NO₂ and NMHC distributions suggest that the photochemical production of ozone is responsible for the primary peak but not the secondary peak. In January, DP occurs more frequently than SP, while in June the SP pattern dominates. Analyses of the surface meteorological data suggest that a unique localized circulation may be responsible for the occurrence of the secondary peak of the DP pattern. A simplified quasi-three-dimensional model is developed to analyze the effect of land-sea breeze on the temporal and spatial variation of O₃.     

臭氧在冰晶及硫酸铵和亚硫酸铵渗溶冰晶上的粘着系数

利用流动管式反应器,在220-260K温度范围内,实验测量了臭氧在低温冰晶及硫酸铵和亚硫酸铵渗溶冰晶表面上的粘着系数.结果表明:臭氧在低温冰晶表面上的粘着系数随温度升高而增大, 其粘着系数为1.3×10-7-2.7×10-6; 臭氧在硫酸铵和亚硫酸铵渗溶冰晶表面上的粘着系数与二者浓度呈非线性关系; 利用实验结果估算了臭氧在极地平流层云中存留寿命约为56d, 臭氧在主要组成为水的冰晶表面上的损耗不容忽视.     

NOx和/或NH3气氛下SO2在高岭土表面非均相转化的实验研究

利用自制气溶胶反应器研究了NO_x和/或NH_3气氛下SO_2在高岭土表面的非均相转化过程,应用扫描电镜(SEM)对高岭土颗粒物形貌进行了表征.结果表明:高岭土颗粒表面的SO_2非均相转化致使其成分和形貌产生了较大变化.相同实验条件下,SO_2转化的协同作用程度由高到低依次为NH_3、NO_x/NH_3和NO_x气氛,相对湿度40%、有光照条件下,SO_2转化量增幅最高可分别达125%、75%和50%.所有气氛下,协同作用在无光照时在高相对湿度(40%~70%)区间更为突出,有光照时其显著性则体现在低相对湿度(20%~40%)区间.SO_2、NO_x、NH_3三者共存时,在高岭土颗粒表面发生的非均相反应过程既有协同作用又存在竞争反应.     

Numerical evaluation of the effectiveness of NO2 and N2O5 generation during the NO ozonation process

Wet scrubbing combined with ozone oxidation has become a promising technology for simultaneous removal of SO₂ and NO_x in exhaust gas. In this paper, a new 20-species, 76-step detailed kinetic mechanism was proposed between O₃ and NO_x. The concentration of N₂O₅ was measured using an in-situ IR spectrometer. The numerical evaluation results kept good pace with both the public experiment results and our experiment results. Key reaction parameters for the generation of NO₂ and N₂O₅ during the NO ozonation process were investigated by a numerical simulation method. The effect of temperature on producing NO₂ was found to be negligible. To produce NO₂, the optimal residence time was 1.25 sec and the molar ratio of O₃/NO about 1. For the generation of N₂O₅, the residence time should be about 8 sec while the temperature of the exhaust gas should be strictly controlled and the molar ratio of O₃/NO about 1.75. This study provided detailed investigations on the reaction parameters of ozonation of NO_x by a numerical simulation method, and the results obtained should be helpful for the design and optimization of ozone oxidation combined with the wet flue gas desulfurization methods (WFGD) method for the removal of NO_x.     

Studying high ozone concentrations by using the Danish Eulerian model

The long-range transport of air pollutants (LRTAP) over Europe is studied by a mathematical model based on a system of partial differential equations (PDEs). The number of PDEs is equal to the number of species studied and the model contains 35 species at present. Among the species are NO, NO₂, NO₃⁻, HNO₃, NH₃, NH₄⁺, O₃, PAN, SO₂, SO₄²⁻ and may hydrocarbons. Most of the 70 chemical reactions involved in the model are nonlinear (including here many photochemical reactions).The model requires large sets of input data. Emissions of SO₂, NO_x, NH₃ and both natural and anthropogenic volatile organic compounds (VOC) are needed in the model. The meteorological data consist of fields of wind velocities, precipitation, surface temperatures, temperatures of the boundary layer, relative humidities and cloud cover, which are read in the beginning of every 6-h interval. Both daytime and nighttime mixing heights are used in the model.Many of the species in the model vary on a diurnal basis. An investigation of the main mechanisms that determine the diurnal variation of the ozone concentrations is performed. One of the important conditions that is necessary if one wants to represent correctly the diurnal variations of the concentrations is to have access to meteorological data that vary diurnally. This is especially true for the temperature and the mixing height.The use of modern numerical algorithms (which are combined with vectorization of the most time-consuming numerical procedures) allows one to perform long-term runs with the model on several high-speed computers. Results obtained in runs with meteorological data for July 1985 and August–October 1989 are discussed. The computed concentrations and depositions are compared with measurements taken at stations located in different European countries. The agreement between calculated concentrations and measurements is reasonably good.Results obtained with several scenarios, in which the NO_x emission and/or the anthropogenic VOC emissions are varied, are presented. Several main conclusions are drawn by studying the results obtained during the comparisons. Some plans for future development of the models are discussed.     

Source-receptor relationships for wet SO42− and NO3− production

Precipitation chemistry data for the years 1982–1985 from 110 stations distributed across the continental U.S. and southern Ontario Province are used to describe the geographic distributions of SO₄²⁻ and NO₃⁻ in precipitation. Volume-weighted, wet SO₄²⁻ and NO₃⁻ concentrations, averaged over the 4 years of observation by season and annullly, show coherent patterns with maxima in the northeastern U.S. and southeastern Canada about ten times greater than the minima observed in the Intermountain and Pacific Northwest regions.Tests for empirical source-receptor relationships indicate that, in land areas with relatively low emissions of SO₂ and NO_x, the associations between wet SO₄²⁻ concentrations and SO₂ emissions and between wet NO₃⁻ concentrations and NO_x emissions within 560 km of each precipitation chemistry station are weak or nonexistent (r²⩽0.42). The remaining land areas show moderate to strong associations between SO₂ and SO₄²⁻ and NO_x and NO₃⁻ during the spring and summer, but only weak to nonexistent associations during the winter. The associations between emissions and concentrations, e.g. SO₂ and SO₄²⁻, are equally well represented by either a linear or a power law function. However, at the level of aggregation employed, the data do not substantiate a linear-proportional relationship between concentrations and anthropogenic emissions. Furthermore, emissions of SO₂ and NO_x are highly correlated, as are the emissions of RHC and NO_x.