Molecular Level Analysis of Photochemical Processing of Brown Carbon and Nitrogen Compounds in Atmospheric Aerosols
EMSL Project ID
47915
Abstract
Atmospheric aerosols have a profound effect on climate by scattering and absorbing solar and Earth radiation. They can be predominantly scattering (e.g., sea-salt aerosol), predominantly absorbing (e.g., black carbon), or have intermediate optical properties (e.g., light-absorbing "brown carbon"? organic aerosol). Although the first two types of aerosols have been extensively studied, brown carbon aerosol has been only recently recognized as a significant climate forcing factor. Brown carbon is predominantly produced by biomass burning and atmospheric aging of primary and secondary organic aerosol (POA and SOA). POA and SOA are ubiquitous in urban environments and are typically mixed with inorganic compounds such as sulfates, nitrates, and ammonium. Atmospheric aging of these mixed particles results in formation of various nitrogen-containing organic compounds (NOC), which are now known to account for a significant (~30%) fraction of the total atmospheric particulate nitrogen. Certain types of NOC compounds have recently been shown to strongly absorb solar radiation. For example, our laboratory studies showed that SOA generated from the biogenic precursors become light absorbing and change their color from white to brown when exposed to reduced nitrogen compound such as NH3(g), aqueous phase NH4+ and amino acids. Furthermore, we discovered that formation of light absorbing NOC may be greatly accelerated during cloud processing of SOA. This previously-unrecognized type of brown carbon is thus secondary, as it is formed by atmospheric chemistry, and distinct in nature from the primary brown carbon produced by various direct emission sources. The climate relevance of the transformation of predominantly scattering organic aerosol into brown carbon is not understood at present. An accurate assessment of the role of light-absorbing NOC on climate and on the nitrogen cycle cannot be achieved without a fundamental understanding of the relationship between the chemical and physical properties of NOC species relevant to the atmospheric and aquatic environments. We propose to carry out a first systematic investigation of the role of NOC in the light-absorption by aged SOA. Using the unique molecular-level characterization capabilities of high-resolution mass spectrometry and state-of-the-art high-resolution sum frequency generation spectroscopy available at EMSL, we will be able to address the following important questions: 1) What is the chemical composition and molecular identity of NOC in urban and rural aerosol? 2) What is the impact of NOC optical properties of SOA? 3) What are the main types of NOC compounds that exhibit the most substantial light absorption characteristics of SOA? 4) How do atmospheric aging processes, such as cloud-processing and photodegradation, affect NOC composition, and subsequently optical properties of SOA?
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Flores JM, R Washenfelder, G Adler, HJ Lee, L Segev, J Laskin, A Laskin, S Nizkorodov, S Brown, and Y Rudich. 2014. "Complex refractive indices in the near-ultraviolet spectral region of biogenic secondary organic aerosol aged with ammonia." Physical Chemistry Chemical Physics. PCCP 16(22):10629-10642. doi:10.1039/C4CP01009D
Julia Laskin, Alexander Laskin, Sergey A. Nizkorodov. 2017. "Mass Spectrometry Analysis in Atmospheric Chemistry." Analytical Chemistry 90 (1):166-189. https://dx.doi.org/10.1021/acs.analchem.7b04249
Laskin J, A Laskin, S Nizkorodov, PJ Roach, PA Eckert, MK Gilles, B Wang, HJ Lee, and Q Hu. 2014. "Molecular Selectivity of Brown Carbon Chromophores." Journal of Environmental Science and Technology 48:12047-12055. doi:10.1021/es503432r
Lee HJ, PK Aiona, A Laskin, J Laskin, and S Nizkorodov. 2014. "Effect of Solar Radiation on the Optical Properties and Molecular Composition of Laboratory Proxies of Atmospheric Brown Carbon ." Environmental Science & Technology 48(17):10217-10226. doi:10.1021/es502515r
O'Brien RE, A Neu, SA Epstein, A MacMillan, B Wang, ST Kelly, S Nizkorodov, A Laskin, RC Moffet, and MK Gilles. 2014. "Phase State and Physical Properties of Ambient and Laboratory Generated Secondary Organic Aerosol ." Geophysical Research Letters [epub ahead of print]:, doi:10.1002/2014GL060219
Shrestha M, Y Zhang, MA Upshur, P Liu, SL Blair, H Wang, S Nizkorodov, R Thomson, ST Martin, and FM Geiger. 2014. "On Surface Order and Disorder of alpha-Pinene-Derived Secondary Organic Material." Journal of Physical Chemistry A. doi:10.1021/jp510780e
Tao S, X Lu, NA Levac, AP Bateman, TB Nguyen, DL Bones, S Nizkorodov, J Laskin, A Laskin, and X Yang. 2014. "Molecular Characterization of Organosulfates in Organic Aerosols from Shanghai and Los Angeles Urban Areas by Nanospray-Desorption Electrospray Ionization High-Resolution Mass Spectrometry." Environmental Science & Technology 48:10993-11001. doi:10/1021/es5024674