2016 Progress Report: Effects of Ammonia on Secondary Organic Aerosol Formation in a Changing Climate

EPA Grant Number: R835881
Title: Effects of Ammonia on Secondary Organic Aerosol Formation in a Changing Climate
Investigators: Dabdub, Donald , Nizkorodov, Sergey
Institution: University of California - Irvine
EPA Project Officer: Chung, Serena
Project Period: January 1, 2016 through December 31, 2018 (Extended to December 31, 2019)
Project Period Covered by this Report: January 1, 2016 through December 31,2016
Project Amount: $701,304
RFA: Particulate Matter and Related Pollutants in a Changing World (2014) RFA Text |  Recipients Lists
Research Category: Air , Climate Change


The goal of this research is to systematically explore the effect of the reactive uptake of ammonia (NH3) by secondary organic aerosols (SOAs) on the yield, chemical composition and optical properties of anthropogenic and biogenic SOAs using both experimental and modeling approaches. Targeted laboratory experiments will be performed in which SOAs are prepared under controlled conditions in a smog chamber; aged by ammonia; and examined with a suite of instruments that measure SOA yield, detailed molecular level composition and optical absorption coefficient. The results of these observations will be implemented in state-of-the-art air pollution models at three different scales: (1) box modeling to replicate chamber experiment results; (2) urban scale modeling of the South Coast Air Basin (SoCAB) of California with a comprehensive chemical mechanism; and (3) modeling of a continental domain that covers the entire contiguous United States that utilizes a simplified version of the chemical mechanism of SOA formation, and includes both the coupling of meteorological and air quality and the interaction between aerosol formation and weather. The three modeling systems will enable the assessment of model sensitivity with respect to chemical and spatial resolution and extension. The coupling of meteorology with air quality provides estimates of feedback effects of aged SOAs on meteorological conditions. In summary, the main objective of this research is to quantify the formation of brown carbon from the reaction of ammonia and SOAs through laboratory experiments and atmospheric computer models.

Progress Summary:

During this period, extensive progress has been made with respect to both laboratory experiments and air quality modeling tasks described in the original project plan. We are closely on track with the timeline established in the proposal. In accordance with Task 1, a variety of controlled laboratory experiments were carried out to study (1) the uptake of gas-phase NH3 by SOA particles; (2) the effect of humidity on the formation of SOAs; and (3) the formation, optical properties, and chemical composition of SOAs formed by low-NOx photooxidation of indole. Modeling efforts during this period have focused on the development and application of the three-dimensional UCI-CIT air quality model to study (1) the impact of global climate change on ozone, PM and SOA concentrations (Task 4); (2) the uptake of gas-phase NH3 by aged SOA particles (Tasks 2 and 3); and (3) the formation of SOAs from photooxidation of indole (Task 2).

In addition to the tasks described above, we have developed an extensive bibliographical database that includes a thorough review of expected changes in future climate and emissions and potential impacts on air quality as well as the current level of understanding of the fundamental science related to ammonia and SOA dynamics. This database is used to validate experimental and model results by comparison to existing studies and, along with results from laboratory experiments, will aid in the development of new chemical mechanisms for the models used in this project.

Future Activities:

For the tasks described above, two manuscripts have been submitted for publication and are currently under review. These manuscripts will be enclosed with the report for the next period after they have been accepted for publication.

Laboratory experiments will continue into the next period to constrain the mechanism of the uptake of gas-phase NH3 by SOA particles and determine uptake coefficients and products for a number of different types of aerosols. Results from chamber experiments will continue to be used in the development and implementation of new science into the air quality models used in this project during the next reporting period. A complete parameterization of the reactive uptake of NH3 by SOAs will be included in the UCI-CIT model’s chemical mechanism to account for NOC formation as described in Task 2 and Task 3. Simulations will be performed to quantify changes in air quality and further our understanding of the interaction of NH3 with SOAs.

We will also introduce a simplified SOA chemical mechanism into the Community Multiscale Air Quality (CMAQ) modeling system to extend this analysis to the continental scale for the contiguous United States as described in Task 5. The SMOKE model will be used to develop spatially and temporally resolved emissions inventories for use in CMAQ, while the WRF model will be used to provide the required meteorological inputs. New simulations will be performed using CMAQ to determine the impact of NH3 uptake by SOA on both gas- and aerosol-phase pollutants at the national level. Results will be compared to existing studies where available, and sensitivity scenarios will be performed to determine modeling sensitivity and uncertainty.

Longer term goals include introducing the simplified SOA chemical mechanism developed for CMAQ into the WRF-CMAQ two-way coupled model. Simulations will be performed to determine potential feedback effects on meteorological conditions that can result from changes in aerosol species concentrations. In particular, the climate effects of BrC produced by ammonia-driven secondary sources will be investigated. 

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

Other project views: All 18 publications 4 publications in selected types All 4 journal articles
Type Citation Project Document Sources
Journal Article Horne JR, Dabdub D. Impact of global climate change on ozone, particulate matter, and secondary organic aerosol concentrations in California: a model perturbation analysis. Atmospheric Environment 2017;153:1-17. R835881 (2016)
R835881 (2017)
  • Full-text: ScienceDirect-Full Text HTML
  • Abstract: ScienceDirect-Abstract
  • Other: ScienceDirect-Full Text PDF
  • Supplemental Keywords:

    Air, ambient air, atmosphere, ozone, global climate, tropospheric, VOC, oxidants, nitrogen oxides, organic, environmental chemistry, engineering, modeling

    Progress and Final Reports:

    Original Abstract
  • 2017 Progress Report