17O excess transfer during the NO2 + O3 → NO3 + O2 reaction

Abstract

The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)∗) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen.

Measurement of the 17O‐excess (Δ17O) of tropospheric ozone using a nitrite‐coated filter

“…Studies of isotope transfer during the O 3 + NO 2 ‐ reaction were conducted in the dark and at room temperature in a Pyrex vacuum line (for details, see Savarino et al and Berhanu et al ). Ozone was produced via Tesla discharge in a cylindrical glass trap using pure oxygen (99.9990%) obtained from a commercial tank supplied by Messer (Bad Soden, Germany).…”

“…To the remaining (major) portion of the ozone, purified helium was added at a pressure of approximately 760 Torr and the combined gas was pumped through a nitrite‐coated filter until the pressure was only 10 Torr. The isotopic equality between the aliquot and the reacting portion of the ozone was verified in a separate experiment . The isotopic composition of both the starting bulk ozone, denoted Δ 17 O(O 3 ) bulk , and the resulting nitrate product were determined separately in order to quantify the transfer of the 17 O‐excess of ozone to the nitrite‐coated filter.…”

“…The measured raw values were converted into enrichment values relative to the tank oxygen used for ozone production using its isotopic composition (δ 18 O and δ 17 O = 11.75 and 5.79‰, respectively, relative to VSMOW) determined earlier. The errors of the ozone isotope ratio determination, including the various steps associated with the handling of O 3 in the vacuum line, collection, and conversion into oxygen using the molecular sieve, are estimated to be 0.1‰ and 0.5‰ for δ 18 O and δ 17 O, respectively …”

Mass-Independent Isotopic Composition of Terrestrial and Extraterrestrial Materials

“…The recognition that the terrestrial nitrogen footprint needs to be better understood has led to the development of new methodologies to study its behavior, including multi-isotopic measurements. Some of the facets requiring further resolution include (1) depositional rates, (2) chemical tropospheric chemical transformation mechanisms, (3) source variability and quantitative identification, and (4) significance of long-range transport of nitrates (Berhanu et al, 2012;Costa et al, 2011;McCabe et al, 2007;Morin et al, 2007Morin et al, , 2008Morin et al, , 2011. It has been shown that atmospheric aerosol nitrate possesses one of the largest mass-independent oxygen isotopic compositions ( Figure 8) observed in nature (Michalski et al, 2002(Michalski et al, , 2003(Michalski et al, , 2004a(Michalski et al, , 2005a).…”

“…It is now known that most oxygen-bearing molecules in the atmosphere (except water) possess mass-independent isotopic compositions (Thiemens, 2006). These molecules include O 2 , O 3 , CO 2 , CO, N 2 O, H 2 O 2 , ClO 4 , as well as aerosol carbonate, nitrate, and sulfate (Berhanu et al, 2012;Costa et al, 2011;Kunasek et al, 2008Kunasek et al, , 2010Shaheen et al, 2010;Thiemens, 2006). Figure 8 displays the mass-independent isotopic composition of most of the molecules that have mass-independent isotopic compositions associated with them.…”