Abstract
This review thoroughly covers the research on green leaf volatiles (GLV) in the context of atmospheric chemistry. It briefly takes on the GLV sources, in-plant synthesis, and emission inventory data. The discussion of properties includes GLV solubility in aqueous systems, Henry’s constants, partition coefficients, and UV spectra. The mechanisms of gas-phase reactions of GLV with OH, NO3, and Cl radicals, and O3 are explained and accompanied by a catalog of products identified experimentally. The rate constants of gas-phase reactions are collected in tables with brief descriptions of corresponding experiments. A similar presentation covers the aqueous-phase reactions of GLV. The review of multiphase and heterogeneous transformations of GLV covers the smog-chamber experiments, products identified therein, along with their yields and the yields of secondary organic aerosols (SOA) formed, if any. The components of ambient SOA linked to GLV are briefly presented. This review recognized GLV as atmospheric trace compounds that reside primarily in the gas phase but did not exclude their transformation in atmospheric waters. GLV have a proven potential to be a source of SOA with a global burden of 0.6 to 1 Tg yr−1 (estimated jointly for (Z)-hexen-1-ol, (Z)-3-hexenal, and 2-methyl-3-buten-2-ol), 0.03 Tg yr−1 from switch grass cultivation for biofuels, and 0.05 Tg yr−1 from grass mowing.
Highlights
F + HNO3 N2O5 no Pfrang et al [192,231] showed that relative rate constants for the gas-phase reactions of NO3 with (Z)-2-hexen-1-ol, (E)-3-hexen-1-ol, (Z)-2-penten-1-ol, and 1-penten-3-ol at 298 ± 3 K obtained using N2O5 as a source of NO3 were higher than the absolute rate constants obtained using off-axis continuous-wave cavity-enhanced absorption spectroscopy (CEAS) using the reaction of F atoms with HNO3 as a source of NO3
There is little data published on the aqueous-phase reactions of green leaf volatiles (GLV), so we present all findings in one section
The calculation based on secondary organic aerosols (SOA) mass yields from the OH photooxidation of isoprene and each GLV in the smog chamber experiments (1.2%, 3.1%, and 0.93%, resp., Section 6.1) scaled up to 3%, 7.5%, and 2.25%
Summary
A for convenience of the audience, we used traditional GLV names rather than the latest IUPAC recommendations; b unspecified isomer. (7.3 ± 2.1 | -), (33.8 ± 11.3 | 7.3 ± 8.5), (4.8 ± 1.4 | -) ng g DW−1 (June | August), Betula pendula, B. pubescens, Populus tremula, resp. Kirstine and Galbally [19] developed a model for estimating BVOC emission from uncut and cut grass in urban environments They estimated that hexenyl-type compounds (C6 GLV alcohols and aldehydes) constituted more than 70% of total BVOC emission upon initial wounding of grass and 22–40% during drying of cut material. The surface concentrations of GLV at the same bulk concentration decreased in the following order: (Z)-3-hexenyl acetate, (Z)-3-hexen-1-ol, MBO, and MeSa. The models accurately reproduced the experimental values of 1-octanol/water partition coefficients and the surface tension of solutions at 298 K and 0.01 MPa. The models indicated that all four GLV tended to remain at water-air interfaces with polar groups oriented towards the water. The observation indicated that the atmospheric reactions of those GLV may proceed at the aqueous interfaces rather than in the bulk gas or aqueous phases
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