AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Resolving Chemical Contributions to Atmospheric Brown Carbon with the Aerodyne Aerosol Chemical Speciation Monitor
LELIA HAWKINS, Raunak Pednekar, Jason Casar, Harvey Mudd College
Abstract Number: 222 Working Group: Source Apportionment
Abstract Light absorbing organic carbon (also known as brown carbon) has many sources in an urban environment, including nitration of aromatics, secondary aqueous formation in aerosol or cloud water, and primary emission during combution of biomass and fossil fuels. This work aims to deconvolute those sources based on organic mass fragments measured by an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Spectra were recorded at 30-minute intervals for a one month period in summertime in an inland location within the Los Angeles basin. Collocated measurements of water soluble organic carbon and water soluble UV/visible light absorption recorded at 5-minute resolution provide a solution phase mass absorption coefficient, allowing us report the variability in aerosol absorptivity over hours, days, and weeks. Preliminary analysis indicates that aerosol absorptivity is highest in the morning hours coinciding with rush hour traffic in the region, while secondary aerosol formation appears to contribute little to additional browning.