Developing mechanisms for secondary organic aerosol from oxygenated volatile organic compounds in biomass burning and volatile chemical product emissions

EPA Grant Number: R840008
Title: Developing mechanisms for secondary organic aerosol from oxygenated volatile organic compounds in biomass burning and volatile chemical product emissions
Investigators: Jathar, Shantanu , Pierce, Jeffrey
Institution: Colorado State University
EPA Project Officer: Chung, Serena
Project Period: August 1, 2020 through July 31, 2023
Project Amount: $400,000
RFA: Chemical Mechanisms to Address New Challenges in Air Quality Modeling (2019) RFA Text |  Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Early Career Awards

Description:

Biomass burning (e.g., wildfires) and volatile chemical products (VCPs) (e.g., personal care products) are important sources of oxygenated volatile organic compounds (VOCs) to the atmosphere. Some of these oxygenated VOCs are expected to oxidize in the atmosphere to form secondary organic aerosol (SOA) and contribute to fine particle pollution. However, most of these oxygenated VOCs are poorly represented in chemical mechanisms and their contribution to the atmospheric SOA burden remains uncertain. 

Objective:

The goal of this research is to improve the representation of SOA formation from oxygenated VOCs in biomass burning and VCP sources in chemical mechanisms. We hypothesize that the inclusion of oxygenated VOCs, particularly phenols, furans, glycols, and glycol ethers, in chemical mechanisms will improve predictions of SOA formation and properties in air quality models (AQMs).

Approach:

The primary tool researchers will use in this work is the SOM-TOMAS (Statistical Oxidation Model-TwO Moment Aerosol Sectional) model that simulates the multigenerational chemistry, thermodynamic properties, and microphysics of SOA. In Objective 1, researchers will update the model to account for the influence of NOX on SOA formation and heterogeneous chemistry of SOA. In Objective 2, the updated model will be used to develop SOA parameters based on environmental chamber and flow reactor data for key oxygenated VOC classes: phenols, furans, glycols, and glycol ethers. The parameters will be corrected for vapor wall losses and, for the first time, be independently evaluated against speciated measurements made using chemical ionization mass spectrometry. The SOM-TOMAS model along with the newly developed parameters will be used to understand the contributions of oxygenated VOCs to SOA formation and properties observed in laboratory and field experiments relevant to biomass burning and VCPs. Finally, in Objective 3, researchers will develop a computationally-efficient, reduced-form volatility basis set model (VBSSOM) that can be easily implemented in AQMs. When constrained against the SOM-TOMAS, the VBSSOM model will capture the dynamic evolution of SOA under atmospherically-relevant conditions.

Expected Results:

One of the primary outcomes of this work is an updated, semi-explicit and open-source organic aerosol model. This model will provide a novel and powerful framework to probe the precursors, pathways, and properties of SOA in laboratory and field experiments. This model development work aligns closely with the EPA’s research priority to enable and contribute to sustained development of chemical mechanisms for use in global and regional AQMs. The organic aerosol model will be used to probe the SOA formation from oxidation of biomass burning and VCP emissions, which should help identify the most important SOA precursors and chemical processes to be included in chemical mechanisms to model the air pollution burden from these sources (Research Area #1). The development and evaluation of a computationally-efficient, reduced-form model, constrained to the more detailed model, will provide an application-specific condensed mechanism appropriate for use AQMs (Research Area #2).

Supplemental Keywords:

particulates, organics, VOCs, solvents, environmental chemistry, physics, modeling, atmosphere, chemical transport