Grantee Research Project Results

2024 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, 2023 through July 31,2024
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 four, we published the manuscript that contains the primary project objective: Development of a N₂O₅ parameterization to account for the dependencies of γ(N₂O₅) on aerosol composition and phase. This included the implementation of the new N₂O₅ uptake (γ(N₂O₅)) and ClNO₂ yield (Φ(ClNO₂)) parameterizations in the Community Multiscale Air Quality (CMAQ) model that account for the role of particulate organic matter in regulating N₂O₅ uptake and the role of reactive solutes in suppressing ClNO₂ production. The primary student involved in this work received their PhD in January of 2024. Since this publication, we have focused on the impact of nocturnal nitrogen chemistry on air quality. These analyses have focused in the spatial and seasonal variability in dominant nocturnal NO_x loss pathway across the United States. Specifically, we used the CMAQ model to calculate the contribution of different loss pathways to the NO_x budget. Reactions of NO₃ with biogenic and anthropogenic volatile organic compounds (VOCs) are the dominant nocturnal loss mechanism in the summer, but the dominant nocturnal loss pathway varies by location in winter. Daytime loss pathways account for 78% of total NO_x loss on average in both seasons, which highlights how most NO_x loss occurs during the day rather than at night.

Future Activities:

In the final year of the project (and no cost extension) we plan to complete the analyses of the contribution of nocturnal chemistry to NO_xlifetimes and prepare it for publication. We expect to submit these results to Geophysical Research Letters during summer 2025.

Journal Articles on this Report : 2 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
Journal Article	Hoffman A, Bertram TH, Holloway T, Harkey M. Assessment of Nocturnal NOx Heterogeneous Reaction Mechanisms in the Community Multiscale Air Quality (CMAQ) Model. Journal of Geophysical Research:Atmospheres. 2024;129(10):e2023JD040290.	R840006 (2024)	Full-text: AGU - Full text HTML Exit

Supplemental Keywords:

air quality, particulate nitrate, heterogeneous and multiphase chemistry

Relevant Websites:

Bertram Research Group Exit

The Holloway Group @ SAGE Exit

data and code from Hoffman et al., 2024 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.