07 Sep 2023
 | 07 Sep 2023
Status: this preprint is currently under review for the journal AMT.

Optimizing a twin-chamber system for direct ozone production rate measurement

Yaru Wang, Yi Chen, Suzhen Chi, Jianshu Wang, Chong Zhang, Weixiong Zhao, Weili Lin, and Chunxiang Ye

Abstract. High Ozone Production Rate (OPR) leads to O3 pollution episodes and adverse human health outcomes. Discrepancies between OPR observation (Obs-OPR) and OPR modeling (Mod-OPR) as calculated from observed and modeled peroxy radical and nitrogen oxides reminds of a yet-perfect understanding of O3 photochemistry. Direct measurement of OPR (Mea-OPR) by a twin-chamber system emerges with the optimization required for suppressing the wall effect. Herein, we minimized the chamber surface area to volume ratio (S/V) to 9.8 m−1 and the dark uptake coefficient of O3 to the order of 10−9. Condition experiments further revealed a photo-enhanced O3 uptake and recommended an essential correction. We finally characterized a measurement uncertainty of ±27 % and a detection limit of 2.8 ppbv h−1 (3SD), which suggests that Mea-OPR is sensitive enough to measure OPR in urban or suburban environments. Application of this system in urban Beijing during the Winter Olympic Games recorded a noontime OPR of 7.4 (±3.8, 1SD) ppbv h−1, which indicates fairly active O3 photochemistry despite the pollution control policy implemented. Mea-OPR versus j(O1D) slope of 6.1 × 105 ppbv h−1 s−1 confirmed fairly active O3 photochemistry, which was assisted by a high abundance of VOCs and NOx, atypically high Mea-OPR even under high-NOx conditions, but mediated by relatively weak ultraviolet (UV) radiation.

Yaru Wang et al.

Status: open (until 28 Oct 2023)

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Yaru Wang et al.


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Short summary
We reported an optimized system (Mea-OPR) for direct measurement of ozone production rate, which showed a precise, sensitive and reliable measurement of OPR for at least urban and suburban atmosphere, and active O3 photochemical production in winter Beijing. Herein, the Mea-OPR system also shows its potential in exploring the fundamental O3 photochemistry, i.e., surprisingly high ozone production even under high-NOx conditions.