Nitrogen Oxides and Atmospheric Chemistry

Nitrogen Oxides and Atmospheric Chemistry. Perhaps the most significant report in this field has been the publication of the proceedings of the symposium of the International Association of Geomagnetism and Aeronomy (Kyoto, Japan, 1973).159 Fifteen papers were presented which contain important information, of which the following might be the most directly relevant  

159 International Association of Geomagnetism and Aeronomy, Symposium Kyoto, Japan, 1973, Canad. J. Chem., 1974, 52, 1381. 

A new method, based on that of Griess-Saltzman, has been developed for measuring N02 in the atmosphere.160 A detailed study has been made of the relative quantum yields for the photolysis of N02 to NO at 5 or 10 nm intervals in the range 295—445 nm, and also at longer wavelengths. The photodissociation probability of N02 remains close to unity for photolysis by all wavelengths shorter than the dissociation limit at 398 nm.161 The photolysis of low concentrations (0.9—lOOp.p.m.) of N02 in air has been investigated and the rate constants of three of the elementary reactions have been directly determined.162 

A preliminary report has appeared of the reaction of NO with vibration-ally excited 03.163 The rate constant for the reaction of 03 with N02 has now been measured over the range of temperature 259—362 K and the data have been fitted to the Arrhenius equation.164 Graham and Johnston165 have also studied this reaction, from 298.2 to 231.4 K. Morris and Niki166 have investigated the mechanism and rate constant of the reaction  

The primary reaction in the photolysis of HN03 vapour by u.v. radiation is  

Nitrogen Oxides and Atmospheric Chemistry. Over the past few years it has become clear that nitrogen oxides play a significant role in the chemistry of our atmosphere. It therefore seems pertinent to include a brief summary of relevant research in this Report. Two features require careful examination the detection of the reactive species (often in very low concentrations) and the measurement of the rates at which they react. 

The important u.v.-filtering action of ozone has caused concern about the factors which control its concentration in the stratosphere. It has been suggested that NO and NOg may control the formation and destruction of stratospheric O3 and a recent study has reported the presence of NO in a mean mixing ratio of 1.0 0.2 parts per thousand million from 11 to 26 km. The NO is probably produced by the reaction  

Oxidation of atmospheric gases e.g. SO2) to form aerosols has been thought to occur with O2 as the oxidizing agent. Kinetic evidence, using the stopped-flow technique, has been obtained to support the theory that the oxidant is 03,2 Vibrationally excited nitrogen plays a number of important roles in determining the nature of the lower thermosphere. In the reaction  

Raman spectroscopy has shown that 25 3 % of the available energy (3.27 eV) appears as vibrational energy. It was shown that the vibrationally excited N2 is a primary product of the reaction and is not produced by collisions of translationally hot oxygen atoms with N2. 

---