Participating Students - Stephen (Bro) Griffith

Stephen (Bro) Griffith
Indiana University, School of Public and Environmental Affairs
BART Enrollement Year: 2008
Email Address: stegriff at
Atmospheric Mentor: Phil Stevens
Biospheric Mentor: Rich Phillips

Research Topic

Influence of biogenic emission factors on HOx chemistry in a Northern Michigan forest


The tropospheric oxidants, OH and HO2 (HOx), are key players in ground level ozone production and Secondary Organic Aerosol (SOA) formation, which are associated with public health concerns and climate change. Measured HOx radical concentrations in forested environments have been poorly predicted by current models of atmospheric chemistry, with measured daytime and nighttime values exceeding models by up to a factor of two. A possible explanation for the elevated HOx radical concentrations is the ozonolysis of undetected biogenic volatile organic compounds such as mono and sesquiterpenes that lead to a net production of HOx and peroxy (RO2) radicals. Mono and sesquiterpene emissions have been shown to be affected by stress events, foliage wetness, and humidity levels, and as a result may indirectly affect HOx concentrations above and inside a forest canopy. This research will examine the trends in HOx concentrations both above and inside the forest canopy to determine if factors that enhance biogenic emissions of terpenes also enhance HOx concentrations, and if these biogenic emission factors are able to improve photochemical models.