Forest Emissions and Uptake of VOCs across the Mass Spectrum: Canopy Profiling by high-resolution PTR-QiTOF during PROPHET- AMOS 2016

Biogenically- emitted volatile organic compounds (VOCs) play a major role in the atmosphere by reacting with oxidants and as precursors to key secondary chemicals. However, the two-way fluxes of such compounds between forests and the atmosphere are uncertain and an important source of uncertainty in current models. During the 2016 PROPHET-AMOS study, we used high-resolution time-of-flight mass spectrometry (PTR-Qi-TOF) to quantify the vertical distribution of VOCs across the mass spectrum within a deciduous forest canopy. Regular observations were made at each of 6 heights from the forest floor to above-canopy. Distinctive vertical gradients were observed across the array of detected compounds, which in some cases changed sign during the course of the 24-hour day. We interpret the results in terms of the insights they provide into the source and sink distributions for different classes of atmospheric organics.