Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Rachel O'Brien

Committee Members

Jonathan Frey

John Poutsma


Atmospheric brown carbon (BrC), the light absorbing portion of Biomass Burning Organic Aerosols (BBOAs), are important in climate chemistry and can contribute to radiative forcing. There are large uncertainties, however, in their lifetimes and behaviors in the atmosphere, causing them to be omitted from global climate models. Many studies disregard the effect of relative humidity on BrC photolysis times, which could be contributing to the uncertainty in their lifetimes. Relative humidity has shown to be an important factor in lab produced molecules representing BrC, however the effect of relative humidity on field samples of BrC have yet to be explored. This study, for the first time, investigates the role of relative humidity on photolysis rates for field samples of BrC. Photodegradation of samples was determined using Ultraviolet/visible (UV/vis) spectroscopy and attenuated total reflectance- Fourier transform infrared spectroscopy (FTIR). The results from both techniques suggest that relative humidity conditions significantly affect photolysis rates of BrC. The variation between high and low relative humidity was observed to be the greatest at time scales less than one day. This suggests that further studies exploring the behavior of BrC should include relative humidity as a factor in order to find the most accurate results.

On-Campus Access Only