Vertical profiles of biogenic volatile organic compounds as observed online at a tower in Beijing

Abstract

Vertical profiles of isoprene and monoterpenes were measured by a proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) at heights of 3, 15, 32, 64, and 102 m above the ground on the Institute of Atmospheric Physics (IAP) tower in central Beijing during the winter of 2016 and the summer of 2017. Isoprene mixing ratios were larger in summer due to much stronger local emissions whereas monoterpenes were lower in summer due largely to their consumption by much higher levels of ozone. Isoprene mixing ratios were the highest at the 32 m in summer (1.64 ± 0.66 ppbV) and at 15 m in winter (1.41 ± 0.64 ppbV) with decreasing concentrations to the ground and to the 102 m, indicating emission from the tree canopy of the surrounding parks. Monoterpene mixing ratios were the highest at the 3 m height in both the winter (0.71 ± 0.42 ppbV) and summer (0.16 ± 0.10 ppbV) with a gradual decreasing trend to 102 m, indicting an emission from near the ground level. The lowest isoprene and monoterpene mixing ratios all occurred at 102 m, which were 0.71 ± 0.42 ppbV (winter) and 1.35 ± 0.51 ppbV (summer) for isoprene, and 0.42 ± 0.22 ppbV (winter) and 0.07 ± 0.06 ppbV (summer) for monoterpenes. Isoprene in the summer and monoterpenes in the winter, as observed at the five heights, showed significant mutual correlations. In the winter monoterpenes were positively correlated with combustion tracers CO and acetonitrile at 3 m, suggesting possible anthropogenic sources.

Sources of non-methane hydrocarbons in surface air in Delhi, India

“…The monoterpenes in particular showed a much stronger correlation with CO during the post-monsoon period suggesting an anthropogenic source. 30,59,72 This conclusion is similar to that reported by who suggested that biogenic molecules may be explained by vehicular or burning sources in Delhi. 45 Pre-monsoon campaign Post-monsoon campaign .…”

Design and characterization of a semi-open dynamic chamber for measuring biogenic volatile organic compound (BVOC) emissions from plants

“…A proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS; Ionicon Analytik GmbH, Innsbruck, Austria), which has time resolution of less than 1 s, is used to monitor the real-time mixing ratios of BVOCs inside the chamber. More detail descriptions about the determination of BVOCs by the PTR-ToF-MS can be found elsewhere (Wang et al, 2014;Huang et al, 2016;H. Zhang et al, 2020).…”

“…Due to vital roles played by BVOCs in atmospheric chemistry, their emission inventory has become an indispensable part of air quality and climate models. Global annual emissions of BVOCs are estimated over 1 Pg (10 15 g) (Guenther et al, 1995), yet these estimations may have large uncertainties (Simpson et al, 1999;Guenther et al, 2006;Y. Zhang et al, 2020) and inaccurate emission factors are among the most important contributors to the uncertainties either regionally or globally (Wang et al, 2011;Guenther et al, 2012;Situ et al, 2014).…”

Variations and sources of volatile organic compounds (VOCs) in urban region: insights from measurements on a tall tower

“…Acetonitrile is widely used as a typical tracer of biomass burning sources in previous studies (de Gouw et al, 2003;Zhang et al, 2020;Tan et al, 2021). However, biomass burning source was not identified in this study because acetonitrile was not predominantly attributed to a single factor (Figure 8).…”