Grantee Research Project Results

2023 Progress Report: Development, validation and integration of a new model-ready parameterization of N2O5 heterogeneous chemistry.

EPA Grant Number: R840006
Title: Development, validation and integration of a new model-ready parameterization of N2O5 heterogeneous chemistry.
Investigators: Bertram, Timothy , Holloway, Tracey
Institution: University of Wisconsin - Madison
EPA Project Officer: Chung, Serena
Project Period: August 1, 2020 through May 8, 2025
Project Period Covered by this Report: August 1, 2022 through July 31,2023
Project Amount: $798,234
RFA: Chemical Mechanisms to Address New Challenges in Air Quality Modeling (2019) RFA Text | Recipients Lists
Research Category: Watersheds , Endocrine Disruptors , Environmental Engineering , Air Quality and Air Toxics , Air

Objective:

The primary objective of this proposal is development and validation of a new chemically based parameterization for γ(N₂O₅) and Φ(ClNO₂) that accounts for recent insights from laboratory and field measurements of N₂O₅ and ClNO₂ heterogeneous chemistry, with a specific focus on the role of phase separation and aerosol water in regulating reactive uptake of N₂O₅. The chemically based parameterization will be constructed such that they can be readily integrated into CMAQv5.3 leveraging new advances in organic aerosol treatment in the model.

Progress Summary:

During year three, we finished the testing and implementation of a modified version of the Gaston et al. (2014) N₂O₅ parameterization to account for the dependencies of γ(N₂O₅) on aerosol composition and phase. We implemented new N₂O₅ uptake (γ(N₂O₅)) and ClNO₂ yield (Φ(ClNO₂)) parameterizations in the Community Multiscale Air Quality model that account for the role of particulate organic matter in regulating N₂O₅ uptake and the role of reactive solutes in suppressing ClNO₂ production. We compared the performance against existing model parameterizations and field measurements. With the new parameterizations, the coarse mode contributed modestly to N₂O₅ loss (17.2%) but significantly to ClNO₂ production (60.3%), highlighting the impact of coarse mode chemistry. The new γ(N₂O₅) parameterization in the fine mode increased agreement between modeled N₂O₅ concentration and observations (RMSE_new=0.37 ppb) compared to the model default (RMSE_default=0.43 ppb). The new γ(N₂O₅) parameterization was overall biased low due to underestimates in modeled particle oxygen to carbon ratio (O:C). The new Φ(ClNO₂) parameterization resulted in further underestimation (NMB_new=−73.7%) compared to the model default (NMB_default=−37.9%) because of underestimation of fine mode particle chloride concentration. We expect that the new parameterizations will more accurately capture the mean state and variability in γ(N₂O₅) and Φ(ClNO₂) under conditions where model particulate O:C and chloride are better represented.

Future Activities:

Our upcoming work will be focused on assessment of the diurnal variability in NOx chemistry by comparison of the surface and column variability of observed NO₂ from ground monitors, the CMAQ model, Pandora spectrometer data, and the once-a-day TROPOMI satellite. This work will naturally extend to new measurements of the diurnal variability in column NO₂ from TEMPO. This work has examined the sensitivity of column NO₂ to surface abundance, statistical methods to relate column and surface NO₂ abundance, and the impact of emissions, chemistry, and meteorology on the distribution of NO₂ in space and time.

References:

Hoffman A, Bertram TH, Holloway T, and Harkey M. Assessment of nocturnal NOx heterogeneous reaction mechanisms in the Community Multiscale Air Quality (CMAQ) model, under review at Journal of Geophysical Resesearch.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views:	All 2 publications	2 publications in selected types	All 2 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Bergin RA, Harkey M, Hoffman A, Moore RH, Anderson B, Beyersdorf A, Ziemba L, Thornhill L, Winstead E, Holloway T, Bertram TH. Observation-based constraints on modeled aerosol surface area:implications for heterogeneous chemistry. Atmospheric Chemistry and Physics 2022;22:15449–68.	R840006 (2022) R840006 (2023) R840006 (2024)	Full-text: Copernicus - Full Text HTML Exit

Supplemental Keywords:

air quality, particulate nitrate, heterogeneous and multiphase chemistry

Relevant Websites:

BERTRAM RESEARCH GROUP Exit

The Holloway Group Exit

data and code from Hoffman et al. can be found at: Assessment of N2O5 heterogeneous reaction mechanisms in the Community Multiscale Air Quality (CMAQ) model Exit

Progress and Final Reports:

Original Abstract

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.