Preprints
https://doi.org/10.5194/egusphere-2023-2293
https://doi.org/10.5194/egusphere-2023-2293
26 Oct 2023
 | 26 Oct 2023

Incorporating Oxygen Isotopes of Oxidized Reactive Nitrogen in the Regional Atmospheric Chemistry Mechanism, Version 2 (ICOIN-RACM2)

Wendell W. Walters, Masayuki Takeuchi, Nga L. Ng, and Meredith G. Hastings

Abstract. The oxygen-stable isotope mass-independent composition (Δ(17O) = δ(17O) – 0.52×δ(18O)) has proven to be a robust tool for probing photochemical cycling and atmospheric formation pathways of oxidized reactive nitrogen (NOy). Several studies have developed modeling techniques to implicitly model Δ(17O) based on numerous assumptions that may not always be valid. Thus, these models may be oversimplified and limit our ability to compare model Δ(17O) values of NOy with observations. In this work, we introduce a novel method for explicit tracking of O3 transfer and propagation into NOy and odd oxygen (Ox), integrated into the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Termed ICOIN-RACM2 (InCorporating Oxygen Isotopes of NOy in RACM2), this new model includes the addition of 55 new species and 727 replicate reactions to represent the oxygen isotopologues of NOy and Ox. Employing this mechanism within a box model, we simulate Δ(17O) for various NOy and Ox molecules for chamber experiments with varying initial nitrogen oxides (NOx = NO + NO2) and α-pinene conditions, revealing response shifts in Δ(17O) linked to distinct oxidant conditions. Furthermore, diel cycles are simulated under two summertime scenarios, representative of an urban and rural site, revealing pronounced Δ(17O) diurnal patterns for several NOy components and substantial Δ(17O) differences associated with pollution levels (urban vs. rural). Overall, the proposed mechanism offers the potential to assess NOy oxidation chemistry in chamber studies and air quality campaigns through Δ(17O) model comparisons against observations. The integration of this mechanism into a 3-D atmospheric chemistry transport model is expected to notably enhance our capacity to model and anticipate Δ(17O) across landscapes, consequently refining model representations of atmospheric chemistry and tropospheric oxidation capacity.

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Wendell W. Walters, Masayuki Takeuchi, Nga L. Ng, and Meredith G. Hastings

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2023-2293', Juan Antonio Añel, 20 Dec 2023
  • RC1: 'Comment on egusphere-2023-2293', Anonymous Referee #1, 02 Feb 2024
  • RC2: 'Comment on egusphere-2023-2293', Anonymous Referee #2, 08 Mar 2024
  • AC1: 'Comment on egusphere-2023-2293', Wendell Walters, 11 Apr 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2023-2293', Juan Antonio Añel, 20 Dec 2023
  • RC1: 'Comment on egusphere-2023-2293', Anonymous Referee #1, 02 Feb 2024
  • RC2: 'Comment on egusphere-2023-2293', Anonymous Referee #2, 08 Mar 2024
  • AC1: 'Comment on egusphere-2023-2293', Wendell Walters, 11 Apr 2024
Wendell W. Walters, Masayuki Takeuchi, Nga L. Ng, and Meredith G. Hastings

Model code and software

ICOIN_RACM2 Wendell Walters https://doi.org/10.5281/zenodo.8418755

Wendell W. Walters, Masayuki Takeuchi, Nga L. Ng, and Meredith G. Hastings

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Short summary
The study introduces a novel chemical mechanism for explicitly tracking oxygen isotope transfer in oxidized reactive nitrogen and odd oxygen using the Regional Atmospheric Chemistry Mechanism, version 2. This model enhances our ability to simulate and compare oxygen isotope compositions of reactive nitrogen, revealing insights into oxidation chemistry. The approach shows promise for improving atmospheric chemistry models and tropospheric oxidation capacity predictions.