No abstract

No abstract

Although reaction with the earth's surface has been considered the major, if not the only, sink for tropospheric ozone, both theoretical considerations and field observation suggest that gas phase reactions are also a major sink. Field data obtained in a joint study by the University of North Carolina and Research Triangle Institute have shown that gas phase destruction of ozone takes place. The data have also given an indication of the magnitude of the process. Our measurements of the oxides of nitrogen and ozone and the simultaneous changes observed in their concentrations bear out the concept that the NOx‐O3 reactions are a significant sink for ozone.

In the 10 or so years since Haagen-Smit 1 proposed the photochemical mechanism for ozone formation in the lower atmosphere considerable effort has been made to determine the exact nature of the "smog reaction." A great number of the variables affecting this reaction have been demon-* Presented at the 54th Annual Meeting of APCA,

Seventeen continuous 24-hour samples of ozone were obtained in the community air of Chapel YIill, N. C. The readings were made over the period of a year with a Mast ozone meter. The over-all range was 0.0 to 13.0 pphm. The daily ranges varied from 0.0-0.1 to 6.4-13.0. Atmospheric sampling for a number of pollutants revealed the fact that the air of Chapel I-Iill was intermediate in cleanliness between rural and urban air. Ambient air was captured in three different systems, two glass and one Mylar, and irradiated with artificial light or sunlight. Of 29 samples, irradiation caused an apparent ozone synthesis in 25. Four of these cases were confirmed with a I•egener oxyluminescent ozone meter. Of the 21 increases measured with the Mast ozone meSer alone, 9 were greater than 1.2 pphm. The differential of 1.2 pphm was established as the 'confidence level' of the Mast instrument by evaluation in this laboratory. 5OO9