Simultaneous Real-Time Measurement of Isoprene and 2-Methyl-3-Buten-2-ol Emissions From Trees Using SIFT-MS.

Ann-Sophie Lehnert,Erica Perreca,Susan E Trumbore,Jonathan Gershenzon,Georg Pohnert

doi:10.3389/fpls.2020.578204

Abstract

The C5 hemiterpenes isoprene and 2-methyl-3-buten-2-ol (MBO) are important biogenic volatiles emitted from terrestrial vegetation. Isoprene is emitted from many plant groups, especially trees such as Populus, while emission of MBO is restricted to certain North American conifers, including species of Pinus. MBO is also a pheromone emitted by several conifer bark beetles. Both isoprene and MBO have typically been measured by proton-transfer reaction mass spectrometry (PTR-MS), but this method cannot accurately distinguish between them because of their signal overlap. Our study developed a method for using selective ion flow tube mass spectrometry (SIFT-MS) that allows simultaneous on-line measurement of isoprene and MBO by employing different reagent ions. The use of m/z(NO+) = 68 u for isoprene and m/z(O2+) = 71 u for MBO gave minimal interference between the compounds. We tested the suitability of the method by measuring the emission of young trees of Populus, Picea, and Pinus. Our results largely confirm previous findings that Populus nigra, Picea glauca, and Picea abies emit isoprene and Pinus ponderosa emits MBO, but we also found MBO to be emitted by Picea abies. Thus SIFT-MS provides a reliable, easy to use, on-line measuring tool to distinguish between isoprene and MBO. The method should be of use to atmospheric chemists, tree physiologists and forest entomologists, among others.

Highlights

The C5-hemiterpene isoprene, or 2-methyl-1,3-butadiene, is the most abundant biogenic volatile compound emitted from vegetation
We demonstrate the use of selective ion flow tube mass spectrometry (SIFT-MS) for simultaneous measurement of isoprene and MBO by monitoring isoprene with m/z(NO+) = 68 u and MBO with m/z(O2+) = 71 u
Limitations in the mass resolution of the quadrupole used in the SIFT-MS resulted in a 5–6% interference [normalized to m/z(NO+) = 68 u] due to the natural isotopologues of isoprene substituted with a single 13C

Summary

Introduction

The C5-hemiterpene isoprene, or 2-methyl-1,3-butadiene, is the most abundant biogenic volatile compound emitted from vegetation. Its annual global emission is estimated to be 350 to 769 Tg yr−1, approximately half of the total estimated emissions of biogenic volatile organic compounds (BVOC) (Guenther et al, 2012). MBO contributions represent only a minor component of total BVOC emissions (Guenther et al, 2012), but in Northern American pine forests, their levels can reach 4–7 times the level of isoprene (Goldan et al, 1993; Harley et al, 1998; Schade and Goldstein, 2001)

Methods

Results

Conclusion