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Flux Measurement of BVOCs

Deposition and Emission of BVOCs by Eddy Covariance Flux Measurements

The ultra-fast analysis capabilities of IONICON PTR-TOF instruments are essential for eddy covariance flux measurements, allowing to study deposition and emission rates of biogenic volatile organic compounds (BVOCs). 

Flux Measurement of BVOCs

Most volatile organic compounds (VOCs) in the atmosphere originate from biogenic emissions, so-called BVOCs. They play a critical role in atmospheric chemistry and are associated with ozone production and secondary aerosol (SOA) formation. Studies of the atmosphere-ecosystem exchange of BVOCs have been limited to a few dominant compounds in the past. The high-time resolution of IONICON PTR-TOF instruments enables eddy-covariance measurements to study the active atmosphere-ecosystem exchange of a vast number of BVOCs, giving new insights for understanding the atmospheric VOC budget. 

The eddy covariance (also known as eddy correlation and eddy flux) technique is a key method to measure and calculate vertical turbulent fluxes in the atmosphere. It requires high time resolution measurements of 3D wind components (e.g. 5–20 Hz). A parallel measurement of VOC concentrations can be correlated with the vertical wind component to extract emission and deposition fluxes. This necessitates a trace gas analyzer able to measure ultra-low VOC concentrations quantitatively and with a high-time resolution of 10 Hz. 

IONICON‘s PTR-TOFMS series perfectly meets these requirements for eddy covariance flux measurements. They allow for highly time resolved measurements (> 10 Hz) and their high sensitivity for VOCs provides quantitative results for trace gas concentrations. PTR-TOF instruments acquire the full spectrum in each measurement and simultaneously gather data on a vast number of existing BVOCs. Moreover, their high mass resolving power allows for separation of isobars and provides chemical identification of the measured compounds. 

Proton transfer reaction (PTR) is ideally suited for the sensitive measurement for biogenic VOCs, including hydrocarbons (isoprene, monoterpenes, and sesquiterpenes) as well as oxygenated organic compounds (e.g. methanol, acetone, acetic acid, hexenal) and also previously unexpected compounds, for more details see Ruuskanen et al.. Many researchers around the world already rely on IONICON PTR-TOFMS technology for atmospheric research.

Flux Measurements adapted from Park et al. 2013 Science Supporting Online MaterialIn a recent study, published in the prestigious magazine Science, Park. et al. have employed an IONICON PTR-TOF 8000 system for eddy covariance flux measurements. They were able to determine fluxes for over 500 VOCs simultaneously and „conclude that PTR-TOF-MS is a powerful new tool for quantifying ecosystem fluxes for a wide range of VOCs“.