First eddy covariance flux measurements of semi-volatile organic compounds with the PTR3-TOF-MS

We present first eddy covariance flux measurements with the PTR3-TOF-MS, a novel proton transfer time of flight reaction mass spectrometer. During 3 weeks in spring 2016, the instrument recorded 10 Hz data of biogenic volatile organic compounds above a boreal forest, on top of a measurement tower at the SMEAR (Station for Measuring Ecosystem -Atmosphere Relations) II station in Hyytiala, Finland. Flux and concentration data of isoprene, monoterpenes, and sesquiterpenes were compared to the literature. Due to the improved instrument sensitivity and a customized wall-less inlet design, we could detect fluxes of semi-volatile and low-volatility organic compounds with less than singledigit picomol per square meter per second (pmolm(-2) s(-1)) values for the first time. These compounds include sesquiterpene oxidation products and diterpenes. Daytime diterpene fluxes were in the range of 0.05 to 0.15 pmolm(-2) s(-1), which amounts to about 0.25% to 0.5% of the daytime sesquiterpene flux above canopy.Peer reviewe