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

Abstract

Abstract.A 'virtual' disjunct eddy covariance (vDEC) device was tested with field measurements of biogenic VOC fluxes at a subalpine forest site in the Rocky Mountains of the USA. A PTR-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 0.4 mg m −2 h −1 , respectively. High pass filtering due to long sampling lines was investigated in laboratory experiments, and suggested that VOC losses in PTFA lines are generally governed by diffusion laws. Memory effects and surface reactions did not seem to play a dominant role. Model estimates of MBO fluxes compared well with measured fluxes. The results also suggest that latent heat and sensible heat fluxes are reasonably well correlated with VOC fluxes and could be used to predict variations in VOC emissions. The release of MBO, methanol, acetone and acetaldehyde resulted in significant change of tropospheric oxidant levels 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 field analysis of multiple VOC fluxes.

Predicting and partitioning ozone fluxes to maize crops from sowing to harvest: the Surfatm-O<sub>3</sub> model

“…Under these conditions, stomatal resistance was overestimated because of an overestimated impact of VPD upon g max by g VPD function. During late senescence, the model strongly underestimated ozone fluxes, about 33 % in mean (Table 3) Schade et al (2001) and Karl et al (2002). Thus, since Surfatm-O 3 model does not include ozone chemistry, modelled ozone fluxes were underestimated.…”

First space-based derivation of the global atmospheric methanol emission fluxes

“…These emission factors are based on whole ecosystem net methanol flux measurements reported by 17 studies that characterized various ecosystems including tropical forest (Geron et al, 2002;Karl et al, 2004Karl et al, , 2007Langford et al, 2010), warm conifer forest (Karl et al, 2005), cool temperate conifer forest (Schade and Goldstein, 2001;Baker et al, 2001;Karl et al, 2002), temperate broadleaf forest and plantation (Spirig et al, 2005;Karl et al, 2003a;Jardine et al, 2008), boreal forest (Rinne et al, 2007), croplands (Warneke et al, 2002;Schade and Custer, 2004) and grassland (Kirstine et al, 1998;Fukui and Doskey, 1998;Ruuskanen et al, 2010). Among these studies, Kirstine et al (1998) and Fukui and Doskey (1998) have used whole ecosystem enclosure techniques with gas chromatography analysis to quantify emissions from grasslands, Schade and Goldstein (2001), Baker et al (2001) and Geron et al (2002) used above canopy relaxed eddy accumulation with gas chromatography analysis to measure methanol fluxes above forests, whereas all the other studies used protontransfer reaction mass spectroscopy (PTR-MS) and the eddy covariance, or disjunct eddy covariance, approach (see Karl et al, 2002). The daytime fluxes reported by these studies for warm, sunny conditions range from no emissions (or a small net uptake) to a net emission of about 3500 µg m −2 h −1 .…”

North American acetone sources determined from tall tower measurements and inverse modeling

“…The temperature dependence of acetone emissions is simulated using an exponential β coefficient of 0.10. The MEGANv2.1 acetone emission factors and light and temperature dependencies have been established based on a limited set of enclosure and above canopy eddy flux measurements (e.g., Macdonald and Fall, 1993b;Janson et al, 1999;Baker et al, 2001;Schade and Goldstein, 2001;Karl et al, 2002Karl et al, , 2004, and are highly uncertain. Part of our objective here is to apply the KCMP tall tower data to evaluate and better constrain the simulated biogenic acetone flux.…”