2013 Progress Report: Aerosol Optical Properties and Biogenic SOA: Effect on Hygroscopic Properties and Light AbsorptionEPA Grant Number: R835411
Title: Aerosol Optical Properties and Biogenic SOA: Effect on Hygroscopic Properties and Light Absorption
Investigators: Khlystov, Andrey , Ramachandran, Subramanian
Institution: Dessert Research Institute , North Carolina State University
Current Institution: Dessert Research Institute , Carnegie Mellon University
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2013 through March 31, 2016 (Extended to March 31, 2018)
Project Period Covered by this Report: April 1, 2013 through March 31,2014
Project Amount: $398,318
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air
Secondary organic aerosol (SOA) from biogenic sources is a major contributor to the global aerosol burden. It is estimated to have a profound effect on regional and global climate. There is strong evidence that biogenic SOA can influence optical properties of ambient aerosol by altering its hygroscopicity and contributing to light absorption directly via formation of brown carbon and indirectly by enhancing light absorption by black carbon (“lensing effect”). The magnitude of these effects remains highly uncertain. It was suggested that organo-nitrogen (ON) compounds are the substances responsible for formation of brown carbon in biogenic SOA. No evidence exists yet for such a link in ambient aerosol. The goal of this project is to provide comprehensive characterization of optical properties of anthropogenically influenced biogenic SOA, its contribution to aerosol hygroscopicity and light absorption via formation of brown carbon and “lensing” effect, and investigate the link between ON and brown carbon.
During the first year of this project, a set of state-of-the-art instruments has been deployed for 6 weeks within the Southern Oxidant and Aerosol Study (SOAS) at a site near Centerville, Alabama, to study contribution of biogenic SOA to light scattering and absorption by the ambient aerosol. Data analysis is still ongoing. Preliminary results indicate that organic aerosol constituents had a significant contribution to both light scattering and light absorption by the ambient aerosol during the SOAS. The exact contribution of SOA, including that of biogenic origin, to light scattering and absorption, as well as how it is affected by anthropogenic sources will be determined by further analysis of the data collected during the SOAS and a second field campaign at Duke Forest near Chapel Hill, North Carolina, which is planned for summer 2015.
The main activity planned for the next reporting period is to continue analysis of data collected during the SOAS field campaign and prepare a manuscript for publication in a peer-reviewed journal. We also will start preparations for the second field campaign that is planned in summer 2015 at a research site in Duke Forest near Chapel Hill, North Carolina. The same suite of instruments used in the SOAS will be used in Duke Forest. The Duke Forest site is characterized by a stronger influence of anthropogenic sources. A comparison of aerosol properties measured at the two sites will help discern the effect of anthropogenic sources on optical properties of biogenic SOA.