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Oxides and acids of nitrogen play an important role in regulating atmospheric radical levels, in particular, that of the OH radical the main initiator of the degradation of chemicals in the atmosphere. A comprehensive overview on the methods used to measure nitrogen oxides and acids in the troposphere is given and difficulties and artefacts associated with the use of the techniques for measurements in urban and mega city environments is illustrated. State-of-the-art methods for the measurement of OH and HO2 radicals are reviewed and recently recognised difficulties, in particular with the measurement of HO2 radicals, are highlighted.

Other contributions to the book cover our present understanding of the gas, aqueous and particulate/aerosol phase atmospheric degradation chemistry of volatile organic compounds (VOCs) under NOx conditions typical of rural, urban and mega city environments. Examples of measurements of NOx and VOCs in the atmospheres of these environments are given, in particular for the megacities Cairo and Beijing, in conjunction with modelling studies which attempt to simulate the field observations using state-of-the art knowledge on the chemistry of the VOCs and radical levels.



Chapter 1. Field Observations of Daytime HONO Chemistry and Its Impact on the OH Radical Budget

Measurements of daytime nitrous acid (HONO) are reviewed and possible daytime sources of HONO are discussed. The importance of the observed daytime HONO mixing ratios for the HOx budget in urban and rural environments is assessed and recommendation for future work are given.
Jochen Stutz, Kam Weng Wong, Catalina Tsai

Chapter 2. NO2 Measurement Techniques: Pitfalls and New Developments

Reliable measurements of atmospheric trace gases are necessary for both, a better understanding of the chemical processes occurring in the atmosphere, and for the validation of model predictions. Nitrogen dioxide (NO2) is a toxic gas and is thus a regulated air pollutant. Besides, it is of major importance for the oxidation capacity of the atmosphere and plays a pivotal role in the formation of ozone and acid precipitation. Detection of NO2 is a difficult task since many of the different commercial techniques used are affected by interferences. The chemiluminescence instruments that are used for indirect NO2 detection in monitoring networks and smog chambers use either molybdenum or photolytic converters and are affected by either positive (NOy) or negative interferences (radical formation in the photolytic converter). Erroneous conclusions on NO2 can be drawn if these interferences are not taken into consideration. In the present study, NO2 measurements in the urban atmosphere, in a road traffic tunnel and in a smog-chamber using different commercial techniques, i.e. chemiluminescence instruments with molybdenum or photolytic converters, a luminol based instrument and a new NO2-LOPAP, were compared with spectroscopic techniques, i.e. DOAS and FTIR. Interferences of the different instruments observed during atmospheric measurements were partly characterised in more detail in the smog chamber experiments. Whereas all the commercial instruments showed strong interferences, excellent agreement was obtained between a new NO2-LOPAP instrument and the FTIR technique for the measurements performed in the smog chamber.
Jörg Kleffmann, Guillermo Villena Tapia, Iustinian Bejan, Ralf Kurtenbach, Peter Wiesen

Chapter 3. An Overview of Measurement Techniques for Atmospheric Nitrous Acid

An overview is given of all the spectroscopic and wet chemical used for atmospheric measurements of nitrous acid. The measurement precision and difficulties associated with the techniques are discussed.
Xianliang Zhou

Chapter 4. Assessment of HONO Measurements: The FIONA Campaign at EUPHORE

HONO is an important source of OH-radicals, the major oxidant in the atmosphere during daytime that participates in ozone formation and can lead to photo-smog. Nevertheless, there are still many open questions about its formation and role as a source of OH-radicals. A better knowledge of HONO processes is highly desirable for the improvement of air pollution models, many of which do not currently include heterogeneous HONO production mechanisms. One reason for the uncertainties in the atmospheric role of HONO is the difficulty in measuring this species.
To elucidate both aspects – chemical and instrumental issues – a HONO intercomparison campaign was carried out at the EUPHORE simulation chambers within the framework of the EUROCHAMP-2 project, in May 2010. EUPHORE provided a large and well-mixed gas volume for the simultaneous operation of multiple instruments under well controlled, realistic conditions. Ten experiments were carried out to simulate typical urban and semi-rural conditions and to address the following topics: (i) intercomparison of the different techniques, (ii) study of interferences (aerosols, nitrates, nitrites, NO2, etc.) and (iii) HONO sources (nitrophenols, vehicle emissions, ambient air, etc.). The first three experiments were part of an open-informal intercomparison while the rest of the intercomparison experiments were conducted under formally blind conditions with an external referee. The extensive participant list included the majority of groups working in this area globally, running simultaneously 18 techniques/instruments that covered nearly the whole range of techniques capable of measuring HONO. These included spectroscopic and chemical instruments.
In this work, an overview of the campaign in terms of participants, instruments aim of the experiments, etc. is presented, as well as the results of a selected open experiment.
Mila Ródenas, Amalia Muñoz, Francisco Alacreu, Theo Brauers, Hans-Peter Dorn, Jörg Kleffmann, William Bloss

Chapter 5. State of the Art OH and HO2 Radical Measurement Techniques: An Update

The methods used for atmospheric measurements of OH and HO2 radicals are reviewed. Focus is given to advances in the measurement technology, instrument design and calibration for OH and HO2 measurements and a summary of results from some recent intercomparison studies, in particular, the HOxCOMP campaign are presented.
Dwayne Heard

Chapter 6. HOx and ROx Radicals in Atmospheric Chemistry

Work on the relevance of the reaction of excited NO2 with water vapour as an atmospheric source of OH radicals is presented and measurement of absolute absorption cross sections of HONO in the near infrared are reported.
Damien Amedro, Alexander E. Parker, Coralie Schoemaecker, Chaithanya Jain, Pranay Morajkar, Paul S. Monks, Koji Miyazaki, Yoshizumi Kajii, Christa Fittschen

Chapter 7. The Exchange of Soil Nitrite and Atmospheric HONO: A Missing Process in the Nitrogen Cycle and Atmospheric Chemistry

An important nitrogen exchange process that has not been considered in the nitrogen cycle and atmospheric chemistry is presented. The exchange process suggests that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing HONO source that is necessary to explain field measurements.
Hang Su, Yafang Cheng, Ulrich Pöschl

Chapter 8. Nitrogen Oxides: Vehicle Emissions and Atmospheric Chemistry

An overview of vehicle emissions, ambient concentrations, and atmospheric chemistry of NO, NO2, and N2O is presented. We start with a discussion of air quality standards and trends in NO2 levels. We then discuss the formation of nitrogen oxides in vehicle engines, technologies used to control emissions of nitrogen oxides, and the trends in vehicle emissions.
Timothy J. Wallington, John R. Barker, Lam Nguyen

Chapter 9. Modeling Atmospheric HONO Concentrations on the Regional Scale

Mechanisms to simulate the formation of nitrous acid (HONO), an important OH radical source in the atmosphere, have been incorporated into numerical models. The results from the model simulations of HONO formation are compared with field measurements of HONO and conclusions are drawn regarding HONO formation mechanisms in the atmosphere and their representation in models.
Bernhard Vogel, Heike Vogel

Chapter 10. Heterogeneous Atmospheric Chemistry of Nitrogen Oxides: New Insights from Recent Field Measurements

The heterogeneous chemistry of nitrogen oxides that occurs in the dark is important to both the overall budgets of reactive nitrogen in the atmosphere, as well as the formation of oxidants. Two of the most relevant processes include the conversion of NO2 to HONO on ground surfaces and the uptake of N2O5 to produce either HNO3 or ClNO2 on aerosol surfaces. Results from recent field measurements that have investigated the latter process have demonstrated several important findings. First, the uptake of N2O5 is highly variable, and the uptake coefficient, γ(N2O5), is often smaller than model parameterizations based on laboratory studies would suggest. Second, production of ClNO2 is much more efficient than previously thought, and is formed in relatively high yields even at interior continental sites that are well removed from direct sources of sea spray. Finally, N2O5 uptake and ClNO2 production both vary strongly with height in the nocturnal boundary layer, leading to significant complexity in this nighttime chemistry.
Steven S. Brown, Nicholas L. Wagner, William P. Dubé, James M. Roberts

Chapter 11. VOC Degradation in the Atmosphere by Nanophotocatalysts

The paper deals with a novel method for the destruction of VOCs in air. The method is based on usage of an aqueous colloidal solution of nanocarbon-metal oxides compositions in which titanium is chosen as the metal. The colloidal solution is sprayed in the air and under natural solar radiation the nanocomposition, as a photocatalyst, forms OH-radicals in the presence of water molecules from aqueous solution drops or natural moisture. Results of laboratory tests of the method conducted with benzene, toluene, trichloroethene (TCE), cis-dichloroethene and trans-dichloroethene (DCE) in a plexiglass box with dimensions of 2,000 × 1,000 × 1,000 mm are described. The concentrations of substances in the air in the experiments were within the range 1–15 mg/m3, and the concentration of sprayed solution of nanophotocatalysts was about 0.1 g/m3. The concentration of nanophotocatalysts in the colloidal solution was 100 mg/l, and the average size of the nanocompositions and aqueous solution drops were about 5 nm and 5 μm, respectively. The temperature of the air was 25°C and the air humidity was 7–15 g/m3. The air in the box was irradiated with a 60 W UV lamp during 15 min, giving degradation efficiencies of 90–99% for all compositions. Two to three hours were necessary to reach this degradation efficiency with irradiation of the box by sunlight. Concentrations of secondary products from the VOC degradation process were below detectable levels.
Rashid A. Khaydarov, Renat R. Khaydarov, Olga Gapurova, N. K. Nasirova

Chapter 12. Production of the Atmospheric Oxidant Radicals OH and HO2 from the Ozonolysis of Alkenes

The reactions of ozone with alkenes are of importance within atmospheric chemistry as a non-photolytic source of the oxidant radicals OH, HO2 and RO2. While OH yields are relatively well constrained, few data exist for production of HO2 or RO2. We report direct measurements of total radical yields from a range of small (C2–C5) alkenes, using LIF and PERCA techniques within large simulation chamber experiments. OH yields are found to be consistent with established understanding, while HO2 yields are substantially smaller than previous measurements suggest, but in good agreement with those assumed within current atmospheric chemical mechanisms.
William J. Bloss, M. S. Alam, A. R. Rickard, M. Camredon, K. P. Wyche, T. Carr, P. S. Monks

Chapter 13. Theoretical Investigation of the NO3 Initiated Reaction of VOCs

We have studied the reaction mechanism for the NO3 radical initiated atmospheric oxidation of three cresol isomers, p-cresol, m-cresol and o-cresol, in the presence of NO2. We have focused on the reaction mechanism leading to the ring retaining products, methyl-nitrophenol isomers and methyl-benzoquinone isomers. Geometries of the reactants, intermediates, transition states, and products have been optimized at the DFT-B3LYP level of theory with the 6-311 + G(d,p) basis set. The single point energy calculations have been carried out at the CCSD(T) level of theory with the cc-pVDZ basis set. The reaction path where the NO3 and NO2 radicals are added ipso and ortho to the OH group of the cresol isomer, respectively, has the lowest energy barrier.
Solvejg Jørgensen

Chapter 14. Measurements of Trace Gases at Saint-Petersburg State University (SPbSU) in the Vicinity of Saint-Petersburg, Russia

An overview of atmospheric trace gas measurements made using various spectroscopic ground-based instrumentation and measurement techniques at the Department of Physics of Atmosphere, St. Petersburg State University is given. The SPbSU trace-gas retrievals have been compared to independent ground-based and satellite measurements as well as to models. Temporal variations (from diurnal cycles to long-term trends) of trace-gases have been studied on the basis of experimental data.
Yury Timofeyev, Dmitry Ionov, Maria Makarova, Yana Virolainen, Anatoly Poberovsky, Alexander Polyakov, Hamud Imhasin, Sergey Osipov, Anton Rakitin, Marina Kshevetskaya

Chapter 15. Nitro- and Nitro-Oxy-Compounds in Multiphase Particle Chemistry: Field and Analytical Studies

Recent field evidence shows the presence of nitro-phenolic compounds in biomass burning influenced secondary organic aerosol. The results from laboratory and smog chamber experiments suggest that these compounds likely form from the reaction of gas-phase phenolic compounds originating from biomass burning in the presence of NOx. These compounds contribute as much as 3.8% to the organic carbon fraction of wintertime aerosols collected in a rural German village, indicating that they are important secondary organic aerosol constituents during the winter months.
Yoshiteru Iinuma, Hartmut Herrmann

Chapter 16. Heterogeneous and Liquid-Phase Reactions of BVOCs with Inorganic Pollutants in the Urban Atmosphere

This paper tries to say that urban air pollutants, which definitely are dangerous chemicals, can be efficiently removed from urban atmospheres by reactions with biogenic volatile organic compounds emitted by urban vegetation. It briefly recollects several ideas concerning a profitable coexistence of anthropogenic and green urban spaces in contemporary cities, and reviews recent achievements in the chemistry of BVOC-pollutant interactions arbitrarily considered important by the author.
Krzysztof J. Rudziński

Chapter 17. Chemistry of Organic Sulfates and Nitrates in the Urban Atmosphere

The paper overviews the current state of knowledge regarding the origin, formation mechanisms, properties and atmospheric implications of organic sulfates (organosulfates, OS) and organic nitrates (organonitrates, ON). Based on field measurements and smog chamber experiments, these esters have been proved to be relevant components of ambient atmospheric aerosols. Despite the fact that chemical knowledge on esters of sulfuric and nitric acids with simple alcohols has been well documented since the advent of classical organic chemistry (a second part of the nineteenth century), it has been only a recent decade since the discovery of these species in the airborne particulate matter attracted attention of the atmospheric community owing to their enhanced polarity and hydrophilic properties. The advances in the field of analytical instrumentations, chiefly in mass spectrometry, made it possible to provide a detailed characterization of organo-sulfates/nitrates at the molecular level. The composition of aerosol samples collected from various field campaigns showed clearly that organo-sulfates/nitrates may serve as excellent molecular tracers for anthropogenically affected aerosol sources, as it is the case of urban atmosphere.
Rafal Szmigielski

Chapter 18. Tracers for Biogenic Secondary Organic Aerosol from α-Pinene and Related Monoterpenes: An Overview

In this review, we first address the terpenoid composition of ambient fine rural aerosol to give a report on the current state of knowledge in regard to the molecular characterisation of biogenic secondary organic aerosol tracers. The major known, recently elucidated, and still unknown tracers, which can be detected at a significant relative abundance, are listed and briefly discussed. In a second part, we provide a historic account on the discovery of 3-methyl-1,2,3-butanetricarboxylic acid, which involved a long search with several failures and a final success, and propose a revised formation pathway. Finally, we present some brief conclusions and perspectives.
Magda Claeys, Rafal Szmigielski, Reinhilde Vermeylen, Wu Wang, Mohammad Safi Shalamzari, Willy Maenhaut

Chapter 19. An Ionization Method Based on Photoelectron Induced Thermal Electron Generation: capillary Atmospheric Pressure Electron Capture Ionization (cAPECI)

A novel method for atmospheric pressure ionization of compounds with high electron affinity (e.g., nitroaromatic compounds) or gas phase acidity (e.g., phenols) is reported. The method is based on the generation of thermal electrons by the photoelectric effect, followed by electron capture of oxygen in air or, within pure nitrogen, of the analyte itself. In the presence of oxygen, ionization of the analyte is accomplished via charge transfer or proton abstraction by the strong gas phase base O 2 . In terms of least invasive sample structure, the interaction of UV-light with metals represents a very clean method for the generation of thermal electrons at atmospheric pressure. This leads to a soft and selective ionization method, generating exclusively negative ions. The implementation of the ionization stage within a fast flowing gas system additionally reduces the retention time of the ionized sample within the high pressure region of the mass spectrometer. Therefore ion transformation processes are reduced and the mass spectrum corresponds more closely to the neutral analyte distribution than for ionization methods operating in conventional ion sources.
Valerie Derpmann, Iustinian Bejan, Hendrik Kersten, Klaus J. Brockmann, Ian Barnes, Jörg Kleffmann, Thorsten Benter, Hannah Sonderfeld, Ralf Koppmann

Chapter 20. NOx in Chinese Megacities

In the past 30 years, China has undergone great economic improvements, the urbanization rate is increasing, megacities and city clusters are expanding, leading to the development of China’s economy and society. However, the city expansion has resulted in a series of environmental problems, such as increasing energy consumption and consequently emission of pollutants, as well as deterioration in urban air quality. In spite of many measures taken by the Chinese government, air pollution from nitrogen oxides (NOx = NO + NO2) is still serious and the NOx concentration is increasing. This article analyses NOx pollution and its trends in Chinese megacities from three aspects, authoritative routine reports, campaign based research observations, and satellite observations. The article also discusses the main sources of NOx in Chinese Megacities. The discussion is based on a review of research papers on the China NOx emission inventory.
Jun Liu, Tong Zhu

Chapter 21. Urban and Global Effects of Megacity Pollution

Megacities and other large urban areas can often be associated with poor air quality. In the developed world, stricter emissions control legislation has resulted in dramatic improvements in urban air quality. Future emissions scenarios project that this will also spread to the developing world. A result of this will be that air quality in urban areas will become more influenced by emissions from outside of these areas.
Tim Butler

Chapter 22. Temporal Concentration Variation of Gaseous Pollutants and Ionic Species in Mansoura City, Egypt

Measurements of gaseous air pollutants and water soluble ions (SO 4 2− , NO3, Cl, NH 4 + ) were performed at four sites in the urban area of Mansoura city and surroundings and at another background site in a rural area near the city. The results showed that concentrations of gaseous air pollutants undergo seasonal variations characterized by winter maximum levels for SO2 (41.95 μg/m3), and H2S (21.46 μg/m3), autumn maximum levels for NO2 (72.21 μg/m3) and summer maximum levels for total photochemical oxidants (332.33 μg/m3). Higher concentrations of SO 4 2− followed by NH 4 + , Cl and NO 3 , respectively were found in the total water soluble ions (TWSI). These major ions also showed seasonal variations with maximum concentration in summer/autumn for SO 4 2− , NO 3 and NH 4 + and spring for Cl. A statistical analysis of long term measurement data for the measured pollutants indicated strong correlations. It can be concluded that the industrial and residential activities beside the traffic emission are the major sources of air pollutants in the atmosphere of this investigated area. Also the existence of these pollutants in the presence of sun light causes the formation of secondary pollutants, like ozone.
Alia A. Shakour, Sayed S. Abd El Rehim, Inas A. Saleh, Mohammed Abd El-Samea Ali El-Hashemy

Chapter 23. Remote and Ground-Based Sensing of Air Polluted by Nitrogen Dioxide in the Dnepropetrovsk Region (Ukraine)

Data of atmospheric remote sensing in Dnepropetrovsk region have been obtained for different periods (2001, 2004, 2005, 2006 and 2010) from five points located within the Dnepropetrovsk region. Current ground-based stationary research has been carried out at three observation laboratories controlling air pollution during the last 15 years. This paper analyzes the annual mean of the NO2 concentration, on a regional (south east of Ukraine) scale. A tendency for increased nitrogen dioxide concentrations in the air around cities such as Dnepropetrovsk, Dneprodzerzhinsk and Krivoy Rog is found. The average nitrogen dioxide concentrations registered at all these cities’ observation stations have exceeded the maximum permissible concentration values by as much as three to four times during the last decade.
Mykola M. Kharytonov, Valentina M. Khlopova, Sergey A. Stankevich, Olga V. Titarenko

Chapter 24. Atmosphere Pollution Problems in Urban Areas on the Territory of Georgia

Air emissions from industrial facilities and motor vehicles and monitoring of the atmosphere quality in the most industrialized cities of Georgia, Tbilisi Rustavi, Qutaisi, Zestafoni and Batumi, are presented. Fuel consumption and emissions from the transport sector in Tbilisi have been investigated. Using mathematical simulation, the concentration distribution of harmful substances, NOx, at Rustavely Avenue, the crossroad of King David Agmashenebeli and King Tamar Avenue, where traffic is congested, have been studied. Some results from the numerical calculations are presented.
Teimuraz Davitashvili

Chapter 25. The Numeric Forecast of Air Pollution Caused by a Blasting Accident in the Enterprise Responsible for Rocket Fuel Utilization in Ukraine

A mathematical model which can take into account all the scenarios of accidents has been developed. The code AIR-SIM was worked out on the basis of the described difference schemes. This code was used to simulate the atmospheric pollution for different accidents on the territory of the Pavlograd Chemical Plant. In particular, a numerical model was used to predict the atmospheric pollution in the case of HCN emission from the opening at the roof of the building. During the numerical experiment the dynamic of the toxic dose in each room was determined for each case study. It was established that the hitting zone will be about 6 km.
Mykola M. Biliaiev, Mykola M. Kharytonov

Chapter 26. Deterministic and Probabilistic Potential Risk Analysis of Lead Contamination in an Urban Environment in Egypt

A combined deterministic dynamic and probabilistic analysis using a multimedia spreadsheet model has been applied to model the environmental fate of deposited lead in different media of the Egyptian environment and consequent human exposure. The main aim was to provide evidence-based guidance on the magnitude of the contribution of atmospheric emissions, in relation to other environmental media, to human risk in Egypt. Uncertainty and sensitivity analysis approaches have been applied to assess the variation in the output function based on the collective and individual variation of the model inputs.
The dynamic steady state of lead accumulation in soil due to continuous deposition of lead from the atmosphere and irrigation water, and the length of time taken to reach a steady state was examined. Predictions of the model revealed that lead in greater Cairo is high enough to cause concern for the human population. Predicted deterministic and probabilistic human blood lead (PbB) levels in the urban environment exceed the guidance value of 10 μg dl–1 and pose a high potential risk for a significant percentage of the exposed population. Ingestion of lead-contaminated vegetables was found to be the most significant contributor to total PbB.
The current study reveals also that Pb from the atmosphere is the most significant source of lead contamination of vegetation, and all of the deposited lead, controlled by the rate of deposition, remains associated with food contamination with Pb either directly (uptake from air) or indirectly (uptake from soil). Direct foliar contamination is clearly the most important pathway in this concern, which is confirmed by the significant reduction in the contribution to total PbB by the application of washing factor. The model has provided a framework for multimedia risk assessment in Egypt and highlighted some uncertainties.
Nasser M. Abdel-Latif, George Shaw, Mike Ashmore


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