Chemistry: analytical and immunological testing – Nitrogen containing – Oxides of nitrogen
Patent
1991-04-08
1994-10-18
Warden, Robert J.
Chemistry: analytical and immunological testing
Nitrogen containing
Oxides of nitrogen
436135, 436158, 436145, 436137, 422 83, 73 232, 73 3101, 73 3102, 73 3105, G01N 3300
Patent
active
053568184
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to methods and systems for analysing the formation of smog in air, and more particularly for determining: illumination conditions; temperature and illumination conditions; air; following parameters can also be determined from the methods and systems of the invention: total concentration of nitric oxide previously introduced into air, total concentrations of NO.sub.x and NO.sub.y previously introduced into air, ROC/NO.sub.x concentration ratio of the total ROC and NO.sub.x previously introduced into air and average time of prior introductions of ROC into air.
BACKGROUND ART
Photochemical smog, which is commonly characterized by ozone concentrations in the order of 0.1 ppm or greater in air, is an air quality problem in many urban areas, particularly those with high levels of sunlight.
Photochemical smog formation passes through three sequential phases: (1) oxidation of NO to NO.sub.2, (2) production of O.sub.3, and (3) a final phase when O.sub.3 is maintained at, or near, its maximum amount. Chemical processes occurring during each phase are intimately related and interactions between various competing and consecutive chemical reactions make analysis of smog formation difficult. Also because the atmosphere in a state of dynamic flux since, as well as changing dispersion variables, there are changing emissions and changing meteorological conditions, e.g. sunlight, rain and temperature. In the atmosphere smog formation does not always reach completion because reactants are often dispersed before the final phase.
As a consequence of the above difficulties there is presently, despite considerable prior research efforts, a need for systems and methods which can provide reliable measures of smog formation in the atmosphere.
The commonly employed measure of smog concentration, ozone concentration, gives only a partial indication of the amount of smog formation. This problem arises because many chemical species, in addition to ozone, are products of the smog forming reactions and also because ozone is not a stable compound and is readily consumed, especially by reaction with nitric oxide. Thus at any given time the observed concentration of ozone in air is dependent upon the amount of prior emissions of nitric oxide into the air.
Considerable efforts by the inventor have thus been directed towards developing a robust method for determining the amount of photochemical smog formation in air and a laboratory size smog chamber which provides reproducible and accurate estimates of the photochemical reactivty potential of air being tested therein. However, it has been found that prior art smog chambers are prone to give irreproducible and inaccurate results which are thought to be due to different contributions from many variables, e.g. nature of the chamber walls and surface reactions therewith, shaded zones in the chamber, mixing rates, outgassing, chamber pretreatment, chamber deposits, impurities in reactants, non-uniform temperatures, etc. and smog reaction rates that are dependent on the extent of reaction.
There is also a need for a method for predicting smog formation from Reactive Organic Compounds (ROC)/air mixtures. Such a method could be used for screening solvents and fuels and assessing the photoreactivities of hydrocarbon wastes.
Photochemical smog formation from reactive organic compounds (ROC)
itric oxide/air mixtures occurs as follows: ##STR1##
Present methods for measuring the essential reactant, ROC, which is essential for smog formation in the atmosphere are inadequate since they are either not sufficiently sensitive, are very cumbersome and labour-intensive or do not take account of the widely differing smog forming reactivities of the individual organic species which taken together comprise ROC. Frequently, the atmospheric concentrations of the individual ROC species, while sufficient to produce significant quantities of photochemical smog, are too small to be detected by the currently available sensors. Air can be analysed for ROC by high resolution gas
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Commonwealth Scientific and Industrial Research Organisation
Tran Hien
Warden Robert J.
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