Preprints
https://doi.org/10.5194/amt-2021-265
https://doi.org/10.5194/amt-2021-265

  07 Sep 2021

07 Sep 2021

Review status: this preprint is currently under review for the journal AMT.

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

Jianqiang Zeng1,2,4, Yanli Zhang1,2,3, Huina Zhang1,2, Wei Song1,2,3, Zhenfeng Wu1,2,4, and Xinming Wang1,2,3,4 Jianqiang Zeng et al.
  • 1State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
  • 2CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China
  • 3CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 4University of Chinese Academy of Sciences, Beijing 100049, China

Abstract. With the accumulation of data about biogenic volatile organic compounds (BVOCs) emissions from plants based on branch-scale enclosure measurements worldwide, it is vital to assure that measurements are conducted using well-characterized dynamic chambers with good transfer efficiencies and less disturbance on natural growing microenvironments. In this study, a self-made cylindrical semi-open dynamic chamber with Teflon-coated inner surface was characterized both in the lab with standard BVOC mixtures and in the field with typical broad-leaf and coniferous trees. The lab simulation with a constant flow of standard mixtures and online monitoring of BVOCs by proton transfer-time of flight-mass spectrometry (PTR-ToF-MS) revealed that lower real-time mixing ratios and shorter equilibrium times than theoretically predicted due to wall loss in the chamber, and larger flow rates (shorter residence times) can reduce the absorptive loss and improve the transfer efficiencies. However, even flow rates were raised to secure residence times less than 1 min, transfer efficiencies were still below 70 % for heavier BVOCs like α-pinene and β-caryophyllene. Relative humidity (RH) impacted the adsorptive loss of BVOCs less significantly when compared to flow rates, with compound specific patterns related to the influence of RH on their adsorption behavior. When the chamber was applied in the field to a branch of a mangifera indica tree, the enclosure-ambient temperature differences decreased from 4.5 ± 0.3 to 1.0 ± 0.2 °C and the RH differences decreased from 9.8 ± 0.5 % to 1.2 ± 0.1 % as flow rates increased from 3 L min−1 (residence time ~4.5 min) to 15 L min−1 (residence time ~0.9 min). At a medium flow rate of 9 L min−1 (residence time ~1.5 min), field tests with the dynamic chamber for Mangifera indica and Pinus massoniana branches revealed enclosure temperature increase within +2 °C and CO2 depletion within −50 ppm when compared to their ambient counterparts. The results suggested that substantially higher air circulating rates would benefit reducing equilibrium time, adsorptive loss and the ambient-enclosure temperature/RH differences. However, even under higher air circulating rates and with inert Teflon-coated inner surfaces, the transfer efficiencies for monoterpene and sesquiterpene species are not so satisfactory, implying that emission factors for these species might be underestimated if they are obtained by dynamic chambers without certified transfer efficiencies, and that further efforts are needed for field measurements to improve accuracies and narrow the uncertainties of the emission factors.

Jianqiang Zeng et al.

Status: open (until 22 Oct 2021)

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  • RC1: 'Comment on amt-2021-265', Anonymous Referee #1, 16 Sep 2021 reply

Jianqiang Zeng et al.

Jianqiang Zeng et al.

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Short summary
The emission of biogenic volatile organic compounds (BVOCs) from plant leaves is an essential part of biosphere-atmosphere interactions. Here we demonstrate how a dynamic chamber for measuring branch-scale BVOC emissions could be characterized both in the lab for adsorptive losses and in the field for ambient-enclosure environmental differences. The results also imply emission factors for terpenes might be underestimated if measured using dynamic chambers without certified transfer efficiencies.