Grantee Research Project Results

2019 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, 2021)
Project Period Covered by this Report: January 1, 2019 through December 31,2019
Project Amount: $701,304
RFA: Particulate Matter and Related Pollutants in a Changing World (2014) RFA Text | Recipients Lists
Research Category: Air , Climate Change

Objective:

The goal of this research is to explore systematically the effect of the reactive uptake of ammonia (NH₃) by secondary organic aerosols (SOA) on the yield, chemical composition, and optical properties of anthropogenic and biogenic SOA using both experimental and modeling approaches. Targeted laboratory experiments are performed in which SOA 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 are implemented in state-of-the-art air pollution models at different scales: (1) urban scale modeling of the South Coast Air Basin of California (SoCAB) with a comprehensive chemical mechanism, (2) modeling at the continental scale using the CMAQ model with a domain that covers the entire contiguous United States, and (3) simulations of future climate scenarios at the regional and continental scale using the CMAQ model to explore the impact of future climate change on SOA formation. These modeling systems help improve our understanding of air pollution and air quality modeling capabilities.

Progress Summary:

The goals of the project have not changed from the original application, and excellent progress has been made on the tasks described in the project proposal:

Lab experiments aligned with Task 1 were performed during 2019 to probe the NH₃ uptake dependence on relative humidity. Those experiments consolidated our understanding of the maximum possible extent to which the NH₃+SOA reactions occur, which was critically important for further modeling efforts. Lab experiments were expanded to compare the uptake of NH₃ to that of dimethylamine, a common atmospheric amine, in order to further our understanding of organic nitrogen formation in SOA. Modeling efforts during this period have focused on model development with the goal of improving the understanding between the geological factor, climate change and air quality impact, as well as meteorological-air quality feedbacks and model performance evaluation. A variety of air quality modeling tools were employed, including the CMAQ (version 5.2) model to simulate air quality at the continental scale (Task 6), and the WRF-CMAQ (version 5.2) model to simulate meteorological-air quality two-way feedbacks (Task5 & 6), as well as the AMET tool sets for evaluating model performance. First, revisions were made to the manuscript regarding the potential impact of an underestimated VOC inventory on air quality that began during the second period and submitted in the third period, and the paper was published in Atmospheric Environment (Task 6). Second, revisions to the submitted manuscript for the study of potential impacts of different drivers behind future air quality in California that began in the third period were finished, and the paper was published in Environment International (Task 4 and Task 6). Thirdly, by cooperating with a Chinese scholar from UC Davis, we investigated the potential air quality impact due to SOA based NH₃ uptake on China. From those simulations, a similar trend of impact on NH₃ and PM_2.5concentration was found on as our previous US studies, while the magnitude was found much higher due to much stronger NH₃ emission in China (Task 6). Finally, after a thorough testing period, we were able to make the WRF-CMAQ coupled meteorological-air quality model platform fully functional. A series of simulations were conducted using WRF-CMAQ to investigate the feedback between meteorology-air quality, and how our SOA-NH₃ uptake mechanism could impact such feedback (Task 5). Future scenarios regarding climate change were also studied using the newly established WRF-CMAQ platform. The meteorological conditions derived from the 2050 RCP 8.5 (business-as-usual) scenario were used for those simulations, and the air quality impact due to our SOA-NH₃ uptake mechanism was investigated under the changing climate (Task 6).

Future Activities:

With the information on relative humidity dependence of the uptake coefficients, we will be able to model the ammonia chemistry more accurately in different atmospheric environments, ranging from dry to humidThe feedbacks between meteorology-chemistry-aerosols on short- and medium-term scales of the SOA-NH₃ uptake mechanism will be investigated using the WRF-CMAQ modeling system. The parameterization of the reactive uptake of ammonia by SOA that we implemented into the CMAQ model’s chemical mechanism will continue to be refined as additional results from laboratory experiments become available, further improving model performance.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views
Other project views:	All 47 publications	12 publications in selected types	All 11 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Zhu S, Mac Kinnon M, Shaffer BP, Samuelsen GS, Brouwer J, Dabdub D. An uncertainty for clean air:Air quality modeling implications of underestimating VOC emissions in urban inventories. Atmospheric Environment 2019;211:256-67.	R835881 (2019) R835881 (2020)	Abstract: Science Direct - Abstract HTML Exit
Journal Article	Zhu S, Horne JR, Mac Kinnon M, Samuelsen GS, Dabdub D. Comprehensively assessing the drivers of future air quality in California. Environment international 2019;125:386-98.	R835881 (2019) R835881 (2020)	Abstract from PubMed Full-text: Science Direct - Full-Text HTML Exit Other: Science Direct - Full Text PDF Exit

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

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.