Brad Baker's Research
California State University, Sacramento
  College of Natural Sciences and Mathematics
  Department of Chemistry



Biogenic Volatile Organic Compounds

Plants are the major source of volatile organic compounds (VOC) to the atmosphere. These compounds, once emitted, play a major role in the chemistry of the lower atmosphere. Of major interest is the role that biogenic VOCs play in the production of tropospheric ozone, a major component of photochemical smog. This phenomenon occurs when VOCs mix with elevated concentrations of nitrogen oxides (which are primarily anthropogenic), in the presence of sunlight. Also of major interest is the contribution that biogenic VOCs make to natural background organic aerosol. Understanding what affects the composition of atmospheric aerosols is necessary in order to understand aerosols' impact on climate change, human health, and atmospheric visibility. Other important environmental issues that are influenced by biogenic VOCs are carbon cycling and atmospheric oxidant production and loss.

Due to the diversity of plants on Earth and the diversity of biogenic VOCs emitted by various species of plants, quantifying emissions can be challenging. Emission measurements can be made at the leaf level to determine what VOCs are emitted by specific species of plants and what environmental parameters (such as light and temperature) control emissions. Emission flux measurements can be made at the landscape and regional scale to determine integrated emissions from whole ecosystems. The combination of data from these types of measurements allows us to model emission fluxes both regionally and globally. Model data can then be used to help understand how biogenic VOCs affect atmospheric processes.

My research involves quantifying and understanding emissions of biogenic VOCs from various types of plants. Currently, we are focusing on the emissions of sesquiterpenes. Sesquiterpenes are 15 carbon compounds made up of three isoprene units. Once in the atmosphere, these compounds react quickly to produce oxygenated VOCs with low vapor pressures that condense onto atmospheric aerosol. Sesquiterpene emissions have been mostly overlooked since they normally cannot be observed in ambient air due to their short lifetimes. They are also tricky to sample quantitatively due to the ‘stickiness’ of these compounds on surfaces. In our lab, we place small trees and plants into enclosures where we can closely control and monitor environmental conditions and exclude oxidants. We sample onto solid absorbents or use solid phase microextraction then analyze our samples using gas chromatography. In addition to these measurements, my lab is also developing new methods for biogenic VOC analysis. We are working on building small, lightweight, and power conserving instrumentation that can be taken to remote areas and generate accurate data.

Current Students

Stephen Disher M.S.

Ashley Fung M.S.

Graduated Students

Niria Arellano-Jara B.S. (2011)

Jason Fell B.S. (2010)

Wayne Conrad B.S. (2009)

Chithra McCrea M.S. (2009)

Mark Sinnott M.S. (2009)

Fei Du M.S. (2008)

Lex Mitchell B.S. (2008)

John Pham B.S. (2007)

Adriana Flores B.S. (2006)

Mike Graessli M. S. (2006)

Tioga Martin B. S. (2006)

Send questions, problems, comments or suggestions to:

California State University, Sacramento
Department of Chemistry
College of Natural Sciences and Mathematics

Updated: January 19, 2010