What is the environmental importance of mirror-image volatile organic compounds emitted by the Amazon forest?

Project URL: https://edin.ac/4ilOY4v

Group website: https://sites.google.com/view/palmer-group/home

Summary

Understand the environmental importance of mirror-image volatile organic compound emissions. This will be achieved by using measurements to develop a novel emission model that will drive a cutting-edge atmospheric chemistry model.

Project background

Volatile organic compounds (VOCs) are emitted by plants and trees to help with, for example, thermotolerance, warding off pests, and attracting pollinators. They play a central role in atmospheric chemistry, influencing the atmospheric concentration of the hydroxyl radical (the principal tropospheric oxidant) and consequently the lifetime of a range of pollutants. They can also form secondary organic aerosols that influence Earth’s radiative balance directly and indirectly (through alteration of cloud optical properties). 

Recent studies have revealed a possible role for the chirality of emitted monoterpenes in identifying responsible emission processes, particularly the response of forests to drought. Chiral molecules are mirror-images that can manifest themselves in differences in smell or taste, e.g. the two limonene structures smell like oranges or lemons. Recent field measurements have reported oxidation products of chiral hydrocarbons, and new experimental work suggests a link between molecular chirality of monoterpenes and their ability to influence cloud processing. 

Here, we are interested in translating what we know about chiral molecules of alpha and beta monoterpenes from field and laboratory experiments to develop an existing emission model of biogenic VOCs and use the GEOS-Chem atmospheric chemistry transport to explore the resulting seasonal atmospheric distributions of these molecules over the Amazon Basin. 

The project takes advantage of an established link between the University of Edinburgh (Palmer), York/NCAS (Hamilton), and the Max Planck Institute for Chemistry in Mainz, Germany (Professor Jonathan Williams), with both institutes offering complementary expertise to support the studentship.

Research questions

1) How can we use laboratory and field data to develop an existing monoterpene emission model that accounts for chirality?

2) Are there characteristic differences in the atmospheric distributions of different chiral monoterpenes?

o Is one chiral molecule more likely to reach the free troposphere due to differences in diel emission cycles?

o What are the implications for the production of low volatility compounds that help grow organic aerosol?