The conditions allowing one to measure the concentration of terrestrial ozone by the open-path DOAS method using a zero line are considered. A technique based on measuring signals at two wavelengths, at least one of which belongs to the ozone absorption UV band, is described. The error of measurements has been estimated. A block-diagram of the optical "open-path" meter for measuring the terrestrial ozone concentration, TrIO-2, is presented.Introduction. Ozone (O 3 ) -a small fraction of the atmosphere -plays a key role in the photochemical and chemical processes developing in the troposphere and exerting a marked effect on its qualitative composition. By virtue of its high reactivity, this unstable molecular formation is a product and a participant of diverse branched photochemical and chemical reactions. The concentration of ozone in the terrestrial layer of the atmosphere changes substantially depending on the season, time of day, and weather conditions and is very sensitive to anthropogenic polluting emissions into the atmosphere. By exceeding the natural levels of concentration and being one of the main components of summer smog appearing in industrial regions, ozone can accumulate in the terrestrial atmosphere [1]. In toxicity it relates to the most hazardous substances (of the first class of hazard). The majority of ozonometric and Global Atmospheric Watch (GAW) stations that monitor the state of the terrestrial atmosphere are equipped with optical analyzers of terrestrial ozone concentration. Such analyzers have a substantial drawback associated with the necessity of taking samples of air for analysis, which leads to uncontrolled destruction of a portion of the ozone and increase in the error of measurement of its concentration. Moreover, to determine variations of natural (background) concentrations of terrestrial ozone of the order of 40 µg/m 3 (20 ppb) when using an optical path of 1m it is necessary
We present a theoretical basis and develop a convenient mathematical formalism for carrying out a multiwavelength procedure for measuring the concentration of near-ground ozone by the differential optical absorption spectroscopy (DOAS) open-path method. We have analyzed the effect on the measurement results from the difference between the spectra of the probing radiation traveling on the measurement path and the reference path.
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