Harvard Forest Research

Fast time response measurements of volatile organic compound (VOC) concentrations and fluxes at the Harvard Forest Environmental Measurement Station

Principal Investigator: Karena McKinney
Amherst College: May 01 2009 - Apr 30 2010:

Abstract:
Volatile organic compounds (VOCs) are a ubiquitous component of the lowermost atmosphere and play a key role in determining its chemistry and composition. VOCs are derived from both anthropogenic and biogenic sources. Harvard Forest is itself a large source of biogenic hydrocarbons, and is also regularly affected by anthropogenic hydrocarbon emissions from nearby urban and industrial areas. Essential factors regulating the atmospheric chemistry of VOCs that remain poorly understood include the identification and quantification of emitted species, elucidation of the mechanisms and products of hydrocarbon oxidation reactions, and determination of the role of various VOCs in ozone and aerosol formation. We will conduct a series of studies aimed at quantifying sources and sinks of hydrocarbons and at investigating their reactivity in the atmosphere by making direct field observations of ambient concentrations, concentration gradients, and fluxes of these compounds at Harvard Forest. Measurements will be carried out using Proton Transfer Reaction Mass Spectrometry (PTR-MS), an on-line technique with high sensitivity and fast time response capable of simultaneously monitoring multiple VOCs. We will focus specifically on investigating the emission rates and oxidation processes of unsaturated biogenic hydrocarbons such as isoprene and monoterpenes, and on measuring concentrations of oxygenated VOCs such as acetone and methanol. Together, these two classes of compounds dominate the OH reactivity of non-methane hydrocarbons in the atmosphere. These measurements will provide new information on the impact of anthropogenic activity on the hydrocarbon oxidation cycle at Harvard Forest and in the surrounding area.
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