Variability-lifetime relationship of VOCs observed at the Sonnblick Observatory 1999—estimation of HO-densities

Abstract

An extensive dataset of VOC measurements was collected at the Sonnblick Observatory, Austria (3106 m) in Fall/ Winter 1999/2000, showing high mixing ratios of anthropogenic and biogenic VOCs at this high altitude site due to upward mixing of air masses (Geophys. Res. Lett. 2F (2001) 507). Here we give an interpretation of proton-transferreaction (PTR-MS) mass scans obtained in November 1999 based on fragmentation data, GC-PTR-MS analysis and the variability-lifetime relationship, described by the power law, sðlnðxÞÞ ¼ At Àb : The variability-lifetime plot of anthropogenic VOCs gave a proportionality factor A of 1.40 and a,b exponent (sink term) of 0.44 and allowed an estimate of average HO-densities on the order of (1.570.4) Â 10 5 molecules cm À3. Additionally we were able to indirectly determine a diurnal HO-profile with peak values of (1.370.5) Â 10 6 molecules cm À3 around midday. HOreaction rate coefficients for higher aldehydes (heptanal to nonanal) were estimated due to photochemical losses during a stagnant air episode (27 November) and from the variability-lifetime relationship. Combining long term PTR-MS analysis of VOCs and the variability-lifetime method provides a valuable tool for assessing the dominant cause of the variability in VOC concentrations. This information is essential in understanding the sources and photochemical processing of VOCs detected in ambient air at field measurement sites.

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

“…At the TT34 rainforest site, ecosystem-scale fluxes were directly calculated from the PTR-MS measurements using the method of virtual disjunct eddy covariance (vDEC) (Karl et al, 2001;Fig. 4).…”

“…Due to the standard operation conditions of the PTR-MS under our measurement conditions, we neglected water clusters as they are regarded to be insignificant (McKinney et al, 2011;. To summarise these issues, we note that several studies have concluded m/z 73 to originate from MEK only (Bourtsoukidis et al, 2014b;De Gouw et al, 1999Holzinger et al, 2000;Karl et al, 2001Karl et al, , 2005aKim et al, 2015;Millet et al, 2015;Steeghs et al, 2004). Based on these considerations and the similarity of magnitudes measured by the PTR-MS as compared with the GC results, we assume m/z 73 is representative of the atmospheric MEK present.…”

Origin of anthropogenic hydrocarbons and halocarbons measured in the summertime european outflow (on Crete in 2001)

“…From these studies, it was proposed that the coefficient b, the dependence of variability on lifetime, reflects the importance of the source/sink budget in the regional variability of the studied species and varies from b=0 being close to the sources to b=0.5 in remote locations. Since these first studies, the variability concept has been applied to a number of datasets and has proved useful in ascertaining the consistency and quality of measurements and for the estimation of OH concentrations (Williams et al, 2000;Williams et al, 2001, Karl et al, 2001.…”

Technical Note: Determination of formaldehyde mixing ratios in air with PTR-MS: laboratory experiments and field measurements

“…PTR-MS is now used in many branches of atmospheric chemistry research, including air quality monitoring (e.g. Karl et al, 2001aKarl et al, , 2003aKarl et al, , 2003bde Gouw et al, 2003), flux measurements (e.g. Holzinger et al, 1999;Karl et al, 2001b;Grabmer et al, 2004;Spirig et al, 2005), and oxidation studies (e.g.…”