Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry

[摘要] A `virtual' disjunct eddy covariance (vDEC) device was tested with field measurementsof biogenic VOC fluxes at a subalpine forest site in the Rocky Mountains of the USA. APTR-MS instrument was used as the VOC sensor. Daily peak emission fluxes of 2-methyl-3-buten-2-ol(MBO), methanol, acetone and acetaldehyde were around 1.5, 1, 0.8 and 0.4mg m^-2 h^-1, respectively. High pass filtering due to long sampling lines was investigated inlaboratory experiments, and suggested that VOC losses in PTFA lines are generally governedby diffusion laws. Memory effects and surface reactions did not seem to play a dominant role.Model estimatesof MBO fluxes compared well with measured fluxes. The results alsosuggest that latent heat and sensible heat fluxes are reasonably well correlated with VOCfluxes and could be used to predict variations in VOC emissions. The release ofMBO, methanol, acetone and acetaldehyde resulted in significant change of tropospheric oxidantlevels and a 10--40% increase in ozone levels, as inferred from a photochemical box model.We conclude that vDEC with a PTR-MS instrument is a versatile tool for simultaneous fieldanalysis of multiple VOC fluxes.

[学科分类] 大气科学