Measurement of NOy and Potential Artifacts

Oxidized nitrogenous species play a critical role in the formation of ozone in the atmosphere. For both smog chambers and ambient air, a knowledge of the mass balance of such species is useful for the development and validation of methods to model ozone formation. The term NOy has been developed to represent such species although the definition depends on whether it is used by a modeler or an analyst. The modeler would like a measure of the total reactive nitrogen oxides, or odd nitrogen, while the analyst uses an operational definition as the response of a chemiluminescent NO analyzer after the sample is treated with a converter that reduces more highly oxidized species to NO. The term (NOy)i has been used to designate this operational definition from that of NOy. These definitions, though slightly different, should be quite similar based on our knowledge of the individual oxidized nitrogenous species typically found in ambient air. Other definitions in general use are NOx (NO + NO2) and NOz (NOy NOx).