Reaction Kinetics of Green Leaf Volatiles with Sulfate, Hydroxyl, and Nitrate Radicals in Tropospheric Aqueous Phase

Abstract

Green plants exposed to abiotic or biotic stress release C-5 and C-6 unsaturated oxygenated hydrocarbons called Green Leaf Volatiles (GLVs). GLVs partition into tropospheric waters and react to form secondary organic aerosol (SOA). We explored the kinetics of aqueous-phase reactions of 1-penten-3-ol (PENTOL), (Z)-2-hexen-1-ol (HEXOL), and (E)-2-hexen-1-al (HEXAL) with SO4 •–, •OH, and NO3 •. At 298 K, the rate constants for reactions of PENTOL, HEXOL, and HEXAL with SO4 •– were, respectively, (9.4 ± 1.0) × 108 L mol–1 s–1, (2.5 ± 0.3) × 109 L mol–1 s–1, and (4.8 ± 0.2) × 108 L mol–1 s–1; with •OH – (6.3 ± 0.1) × 109 L mol–1 s–1, (6.7 ± 0.3) × 109 L mol–1 s–1, and (4.8 ± 0.3) × 109 L mol–1 s–1; and with NO3 • – (1.5 ± 0.15) × 108 L mol–1 s–1, (8.4 ± 2.3) × 108 L mol–1 s–1, and (3.0 ± 0.7) × 107 L mol–1 s–1. The rate constants increased weakly with temperatures ranging from 278 to 318 K. The diffusional limitations of the rate constants appeared significant only for the GLV–•OH reactions. The aqueous-phase reactions appeared negligible in deliquescent aerosol and haze water but not in clouds and rains. The atmospheric lifetimes of GLVs decreased from many days to hours with increasing liquid water content and radicals’ concentration.

Green Leaf Volatiles in the Atmosphere—Properties, Transformation, and Significance

“…Richards-Henderson et al [22] determined the UV absorption coefficients for (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, MeSa, MeJa, and 2-methyl-3-butene-2-ol in aqueous solutions of pH = 5.5 ± 03 at 298 K (Figure 2, Figure 6, and Figure 7). Their results agree well with [163] and this work regarding peak location, while differences in the intensities can result from experimental errors [163].…”

“…Sarang et al [163] presented UV spectra of 1-penten-3-ol, (Z)-2-hexen-1-ol, and (E)-2-hexen-1-al in aqueous solutions at 298 K and pH = 7 (Figures 1, 4 and 8). The spectra were recorded with a double-beam Lambda 900 UV/VIS/NIR spectrometer (Perkin Elmer Instruments).…”

“…Sarang et al [163] determined the relative rate constants for the aqueous-phase reactions of 1-penten-3-ol, (Z)-2-hexen-1-ol, and (E)-2-hexenal with OH, NO 3 , and SO 4 − radicals (Tables 33 and 34). They used the Laser Flash Photolysis-Laser Long Path Absorption (LFP-LLPA) technique over the 278-318 K temperature range.…”

“…Sarang et al [163] analyzed the atmospheric significance of the aqueous-phase reactions of 1-penten-3-ol, (Z)-2-hexen-1-ol, and (E)-2-hexen-1-al with OH, NO 3 , and SO 4 − radicals. The aqueous-phase reactions reduced the atmospheric lifetimes of GLV at sufficiently high liquid water contents (LWC).…”

“…Figure1. Absorption cross-sections σ of (a) 1-penten-3-one, (b) 1-penten-3-ol[57], and (c) (E)-2pentenal[162] in the gas phase at 298 K, and absorption coefficients ε of (d) 1-penten-3-ol in the aqueous phase at 298 K and pH = 7[163].…”