Technical note : Water vapour concentration and flux measurements with PTR - MS
نویسندگان
چکیده
The most direct approach for measuring the exchange of biogenic volatile organic compounds between terrestrial ecosystems and the atmosphere is the eddy covari-ance technique. It has been applied several times in the last few years using fast response proton-transfer-reaction mass spectrometry (PTR-MS). We present an independent validation of this technique by applying it to measure the water vapour flux in comparison to a common reference system comprising an infra-red gas analyser (IRGA). Water vapour was detected in the PTR-MS at mass 37 (atomic mass units) corresponding to the cluster ion H 3 O + ·H 2 O. During a five-week field campaign at a grassland site, we obtained a non-linear but stable calibration function between the mass 37 signal and the reference water vapour concentration. With a correction of the high-frequency damping loss based on empirical ogive analysis, the eddy covariance water vapour flux obtained with the PTR-MS showed a very good agreement with the flux of the reference system. The application of the empirical ogive method for high-frequency correction led to significantly better results than using a correction based on theoretical spectral transfer functions. This finding is attributed to adsorption effects on the tube walls that are presently not included in the theoretical correction approach. The proposed high-frequency correction method can also be used for other trace gases with different adsorption characteristics .
منابع مشابه
Water vapour flux measurements with PTR-MS
The most direct approach for measuring the exchange of biogenic volatile organic compounds between terrestrial ecosystems and the atmosphere is the eddy covari-ance technique. It has been applied several times in the last few years using fast response proton-transfer-reaction mass spectrometry (PTR-MS). We present an inde-5 pendent validation of this technique by applying it to measure the wate...
متن کاملFabrication and Characterization of Novel Mixed Matrix Polyethersulfone Based Nanofiltration Membrane Modified by Ilmenite (TECHNICAL NOTE)
This study is focused on fabrication and characterization of mixed matrix poly ether sulfone based nanofiltration membrane by phase inversion method. The effect of different amounts of Ilmenite (FeTiO3) particles as inorganic filler additive in the casting solution on physic-chemical characteristics of membranes was studied. Scanning electron microscopy, surface analysis, water content, contact...
متن کاملTechnical Note: Determination of formaldehyde mixing ratios in air with PTR-MS: laboratory experiments and field measurements
Formaldehyde (HCHO), the most abundant carbonyl compound in the atmosphere, is generated as an intermediate product in the oxidation of nonmethane hydrocarbons. Proton transfer reaction mass spectrometry (PTR-MS) has the capability to detect HCHO from ion signals at m/z 31 with high time-resolution. However, the detection sensitivity is low compared to other detectable species, and is considera...
متن کاملA NOTE ON THE FLUX-VARIANCE SIMILARITY RELATIONSHIPS FOR HEAT AND WATER VAPOUR IN THE UNSTABLE ATMOSPHERIC SURFACE LAYER Research Note
Atmospheric surface layer (ASL) experiments over the past 10 years demonstrate that the flux-variance similarity functions for water vapour are consistently larger in magnitude than their temperature counterpart. In addition, latent heat flux calculations using the flux-variance method do not compare as favorably to eddy-correlation measurements when compared to their sensible heat counterpart....
متن کاملEddy covariance emission and deposition flux measurements using proton transfer reaction – time of flight – mass spectrometry (PTR-TOF-MS): comparison with PTR-MS measured vertical gradients and fluxes
During summer 2010, a proton transfer reaction – time of flight – mass spectrometer (PTR-TOF-MS) and a quadrupole proton transfer reaction mass spectrometer (PTR-MS) were deployed simultaneously for one month in an orange orchard in the Central Valley of California to collect continuous data suitable for eddy covariance (EC) flux calculations. The high time resolution (5 Hz) and high mass resol...
متن کامل