Citation:

Xie, M., X. Chen, A. Holder, M. Hays, M. Lewandowski, J. Offenberg, Tad Kleindienst, M. Jaoui, AND M. Hannigan. Light Absorption of Organic Carbon and its Sources at Southeastern U.S. Locations in Summer. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 244:38-46, (2018). https://doi.org/10.1016/j.envpol.2018.09.125

Impact/Purpose:

This work seeks to identify the major sources of atmospheric brown carbon in the summertime in the southeastern United States.Light absorbing carbon, also referred to as brown carbon, contributes to regional haze and can impact the earth’s radiative balance. Biomass burning has been identified as a major source of brown carbon to the atmosphere, but other sources or processes have been rarely studied. In this work particulate matter samples were taken in Research Triangle Park, NC over the summer of 2013 and analyzed for light absorption, carbonaceous content, organosulfates, and nitroaromatics. Positive matrix factorization (PMF) was used to identify the particulate matter composition associated with light absorption and identify sources of brown carbon. The results suggest that secondary organic aerosol containing organosulfates derived from biogenic emissions are a major source of brown carbon in this region during the summertime.

Description:

Light-absorbing organic carbon (OC), also referred to as “brown carbon” (BrC), has been intensively investigated in biomass burning (BB) impacted atmospheres. However, other BrC sources (e.g., secondary formation) are rarely studied in ambient aerosols. In the current work, forty-five PM2.5 filter samples were collected in Research Triangle Park (RTP), NC, from June 1st to July 15th, 2013. The bulk carbonaceous components, including OC, elemental carbon (EC), water soluble OC (WSOC) and an array of organic molecular markers (OMMs) were measured; a ultraviolet (UV)/visible (Vis) spectrometer was used to measure the light absorption of methanol extractable OC and WSOC. Less than 1% of the BrC absorption is attributed to nitroaromatic compounds identified in this work; the light absorption per mass OC (0.36 ± 0.16 m2 g-1C) or WSOC (0.29 ± 0.13 m2 g-1C) is weaker than other locations (0.7 – 1.6 m2 g-1C) with substantial influences from BB or anthropogenic emissions. To identify the major sources of BrC absorption in RTP in the summer, Positive Matrix Factorization (PMF) was applied to the dataset containing optical properties and chemical compositions of carbonaceous components in PM2.5. The results suggest that the formation of biogenic secondary organic aerosol (SOA) containing organosulfate and anthropogenic SOA dominate the BrC absorption in RTP during the summertime, while the chemical and optical properties of specific secondary BrC chromophores warrant further study.

URLs/Downloads:

Record Details: