---

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 HO 2 radicals are reviewed and recently recognised difficulties, in particular with the measurement of HO 2 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.

---

Field Observations of Daytime HONO Chemistry and its Impact on the OH Radical Budget; J. Stutz et al.- NO 2 Measurement Techniques: Pitfalls and New Developments; J. Kleffmann et al.- An Overview of Measurement Techniques for Atmospheric Nitrous Acid; X. Zhou.- Assessment of HONO Measurements: The FIONA Campaign at EUPHORE; M. Ródenas et al.- State of the Art OH and HO 2 Radical Measurement Techniques: An Update; D. Heard.- HO x and RO x Radicals in Atmospheric Chemistry; D. Amedro et al.- The Exchange of Soil Nitrite and Atmospheric HONO: a Missing Process in the Nitrogen Cycle and Atmospheric Chemistry; H.Su et al.- Nitrogen Oxides: Vehicle Emissions and Atmospheric Chemistry; T. J. Wallington et al.- Modeling Atmospheric HONO Concentrations on the Regional Scale; B. Vogel, H. Vogel.- Heterogeneous Atmospheric Chemistry of Nitrogen Oxides: New Insights from Recent Field Measurements; S.S. Brown et al.- VOC Degradation in the Atmosphere by Nanophotocatalysts; R.A. Khaydarov et al.- Production of the Atmospheric Oxidant Radicals OH and HO 2 from the Ozonolysis of Alkenes; Wm. J. Bloss et al.- Theoretical Investigation of NO 3 Initiated Reactions of VOCs; S. J›rgensen.- Measurements of Trace Gases at Saint-Petersburg State University (SPbSU) in the Vicinity of Saint-Petersburg, Russia; Y. Timofeyev et al.- Nitro- and Nitro-oxy-compounds in Multiphase Particle Chemistry: Field and Analytical Studies; Y. Iinuma, H. Herrmann.- Heterogeneous and Liquid-Phase Reactions of BVOCs with Inorganic Pollutants in the Urban Atmosphere; K. J. Rudzinski.- Chemistry of Organic Sulfates and Nitrates in the Urban Atmosphere; R. Szmigielski.- Tracers for Biogenic Secondary Organic Aerosol from __Pinene and Related Monoterpenes: An Overview; M. Claeys et al.- An Ionization Method based on Photoelectron Induced Thermal Electron Generation- Capillary Atmospheric Pressure Electron Capture Ionization (cAPECI); V. Derpmann et al.- NO x in Chinese Megacities; J.Liu, T. Zhu.- Urban and Global Effects of Megacity Pollution; T. Butler.- Temporal Concentration Variation of Gaseous Pollutants and Ionic Species in Mansoura City, Egypt; A.A. Shakour et al.- Remote and Ground-based Sensing of Air Polluted by Nitrogen Dioxide in the Dnepropetrovsk Region (Ukraine); M.M.Kharytonov et al.- Atmosphere Pollution Problems in Urban Areas on the Territory of Georgia; T. Davitashvili.- The Numeric Forecast of Air Pollution caused by a Blasting Accident in the Enterprise Responsible for Rocket Fuel Utilization in Ukraine; M. M.Biliaiev et al.- Deterministic and Probabilistic Potential Risk Analysis of Lead Contamination in an Urban Environment in Egypt; N.M. Abdel-Latif et al.- Author Index.

---