Text Material Preview
Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=zelb20 Tellus B: Chemical and Physical Meteorology ISSN: (Print) 1600-0889 (Online) Journal homepage: www.tandfonline.com/journals/zelb20 15N/14N ratios of NO>x from vehicle engines and coal-fired power stations T. H. E. Heaton To cite this article: T. H. E. Heaton (1990) 15N/14N ratios of NO>x from vehicle engines and coal- fired power stations, Tellus B: Chemical and Physical Meteorology, 42:3, 304-307, DOI: 10.3402/ tellusb.v42i3.15223 To link to this article: https://doi.org/10.3402/tellusb.v42i3.15223 © 1990 The Author(s). Published by Taylor & Francis. Published online: 18 Jan 2017. Submit your article to this journal Article views: 198 View related articles Citing articles: 29 View citing articles https://www.tandfonline.com/action/journalInformation?journalCode=zelb20 https://www.tandfonline.com/journals/zelb20?src=pdf https://www.tandfonline.com/action/showCitFormats?doi=10.3402/tellusb.v42i3.15223 https://www.tandfonline.com/action/showCitFormats?doi=10.3402/tellusb.v42i3.15223 https://doi.org/10.3402/tellusb.v42i3.15223 https://www.tandfonline.com/action/authorSubmission?journalCode=zelb20&show=instructions&src=pdf https://www.tandfonline.com/action/authorSubmission?journalCode=zelb20&show=instructions&src=pdf https://www.tandfonline.com/doi/mlt/10.3402/tellusb.v42i3.15223?src=pdf https://www.tandfonline.com/doi/mlt/10.3402/tellusb.v42i3.15223?src=pdf https://www.tandfonline.com/doi/citedby/10.3402/tellusb.v42i3.15223?src=pdf https://www.tandfonline.com/doi/citedby/10.3402/tellusb.v42i3.15223?src=pdf Tel/us (1990), 42B, 304-307 SHORT CONTRIBUTION 15N/14N ratios of NOx from vehicle engines and coal-fired power stations By T. H. E. HEATON*, Natural Isotopes Division, NPRL, CS/R, P.O. Box 395, Pretoria, South Africa (Manuscript received 10 March 1989; in final form 13 June 1989) ABSTRACT Preliminary data are presented for the 15 N/ 14N ratios of the two main sources of anthropogenic NOx. Contrary to expectation, the b15 N values of NOx emitted from vehicle exhausts ( - 13 to - 2 %0 ) and coal-fired boilers ( + 6 to + 13 %0 ) are different from the isotopic composition of the nitrogen in their fuel+ air mixtures ( ~0%0). These differences may reflect variable effects of kinetic isotopic fractionation in the formation (vehicles) and destruction (boilers) of NO, and have important consequences for the use of nitrogen isotopes in atmospheric studies. 1. Introduction Because nitrogen compounds play such an important role in the chemistry and pollution of the atmosphere, several studies have been directed towards an examination of their 15N/ 14N ratios (Roering, 1957; Moore, 1977; Freyer, 1978; Heaton, 1986, 1987). The interpret ations of these studies, however, require infor mation on the isotopic composition of the NOx gases (NO and N02 ), for which very few data are available. The major sources for the anthropogenic emission of NOx are vehicles and coal-fired power stations. The nitrogen in their fuel + air combustion mixtures is either atmospheric N 2 (in vehicles) or atmospheric N 2 plus coal-nitrogen (in power stations). In both cases, this source nitrogen has a b15 N value which is equal to or close to 0 %0 : b 1 5 N = 0 %0 for atmospheric N 2 , b 1 5 N = typically - 2 to + 3 %0 for coals (see foot note to Table 1 for definition of b15N). It has therefore been assumed that the NOx gases formed by oxidation of this nitrogen will also *Present address: Isotope Geology Laboratory, Keyworth, Nottingham NG 12 5GG, England. have b15 N close to 0%0 (Freyer, 1978; Heaton, 1987). Whilst a b15N value close to 0%0 for the anthropogenic emissions of NOx was partially supported by two earlier measurements of vehicle exhausts (b 15 N = -1.8 and +3.7%0 (Moore, 1977; Freyer, 1978)), subsequent analyses of vehicle NOx suggested a wider range (b 15N = -13 to - 2 %0 , and a single analysis of NOx from a power station yielded b15N = +5%0 (Heaton, 1987)). I therefore present 15N/14N ratio data for NOx from a further four vehicle exhausts and four power station emissions, and suggest possible mechanisms whereby the major sources of anthropogenic NOx may have b 15N values which are not close to 0%0 • The new data are discussed in conjunction with the earlier data presented, but not discussed, in Heaton (1987). 2. Analytical method and precision Gases were sampled from the exhaust pipes of test-bed and road vehicle engines at Pretoria (altitude = 1300 m, no catalytic convertors) and from downstream of the electrostatic precipi tators of coal-fired boilers generating steam for electric power stations on the Transvaal Highveld Tellus 42B (1990), 3
