标题：Continuous flux measurements of VOCs using PTR-MS — reliability and feasibility of disjunct-eddy-covariance, surface-layer-gradient, and surface-layer-profile methods
摘要：We measured VOC fluxes using disjunct-eddy-covariance (DEC), surface-layer-gradient (SLG), and surface-layer-profile (SLP) methods with proton transfer reaction mass spectrometry (PTR-MS) above a boreal forest in Hyytiälä, Finland. Our aim was to examine the reliability and feasibility of these methods for long-term measurements at low-flux conditions typical for boreal forests. The compounds targeted were formaldehyde, methanol, acetaldehyde, acetone, isoprene/methylbutenol fragment, methylbutenol, hexanal, hexenal and monoterpenes. We carried out a 10-day comparison between the techniques and used longer continuous data sets for the feasibility study. Out of these surface layer methods, the SLP method performed the best. We found out that with the SLP method we were able to detect fluxes for all the targeted compounds except formaldehyde. The method had also smaller detection limits and better data coverage than the DEC method. The systematic error of both SLP and SLG techniques was estimated to be around 10% for these measurements and it was caused by the high frequency attenuation for the DEC and by the turbulence parametrization for the SLP. As a conclusion the SLP method can be recommend for long-term flux measurements in low-flux conditions.
