The role of nitrate radicals (NO3) in aerosol life cycle: Secondary organic aerosol formation and aging of atmospheric organic aerosolsEPA Grant Number: R835403
Title: The role of nitrate radicals (NO3) in aerosol life cycle: Secondary organic aerosol formation and aging of atmospheric organic aerosols
Investigators: Ng, Nga Lee
Institution: Georgia Institute of Technology
Current Institution: Georgia Institute of Technology
EPA Project Officer: Chung, Serena
Project Period: April 1, 2013 through March 31, 2016 (Extended to March 31, 2017)
Project Amount: $300,000
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Global Climate Change , Climate Change , Air
The overall goal of the proposed project is to experimentally determine the extent to which NO3 radicals (formed from anthropogenic NO2 and ozone) affect organic aerosol (OA) loading and composition over its atmospheric lifetime, taking into account secondary organic aerosol (SOA) formation from NO3 oxidation pathway and both daytime and nighttime aging processes. The interactions of biogenic volatile organic compounds (VOCs) with NO3 radicals represent a direct way for positively linking anthropogenic and biogenic emissions. The first specific objective is to experimentally characterize SOA formation and gas- and particle-phase composition from the reaction of biogenic VOCs with NO3 radicals. It is hypothesized that SOA formation is dependent on the fate of peroxy radical, relative humidity, and particle acidity. The second specific objective is to determine the changes in SOA loadings and key properties with multigenerational aging, including both photochemical (OH) and dark (NO3) aging.
A series of experiments will be performed in the Georgia Tech Indoor Chamber Facility. The changes in gas and aerosol composition, aerosol chemical and physical properties will be continuously monitored by a suite of analytical instruments surrounding the chamber facility. This allows for linking gas-phase chemistry to SOA formation. Experiments will be performed to study SOA formation from the nitrate oxidation of biogenic VOCs with different RH and seed acidity conditions. A series of aging experiments will also be performed to examine the mutigenerational SOA chemistry by characterizing the chemical composition of OA over its diurnal life cycle.
This study will provide an extensive data set on SOA formation from nitrate oxidation pathway and the multigenerational chemistry involving both photochemical and dark aging. Yield parameters (e.g., Odum 2 product model, 2D volatility basis set) can be directly obtained from this study and be used in models. The inclusion of results from this study will improve our ability to simulate SOA formation in models, especially in constraining the nighttime chemistry as well as the diurnal variations of organic carbon. An improved SOA model will help inform policy makers on regulations on air quality.