PTR-ToF-MS data

Volatiles were analyzed with a PTR-ToF-MS 8000 (IoniconAnalytik
GmbH, Innsbruck, Austria) using H3O+ as reagent ion for
the proton transfer reaction. The reaction takes place between H3O+
ions and all the biogenic or anthropogenic VOCs having a proton affinity higher
than that of water (165.2 kcal mol−1). Separation of single ions
happens accordingly to their mass to charge (m/z) ratio. Drift applied
voltage was set at 600 V, temperature at 110 °C, and pressure at 2.25 mbar. For
each sample, about 6 grams of material was transferred in a glass jar provided
with a special lid that allowed Teflon connection to a zero-air generator
(inlet) and the PTR-ToF system (outlet). The head space was then measured by
direct injection into the PTR-ToF drift tube inlet for 150 seconds, after
respectively 1 and 20 min of exposure.

Preliminary measurements on an
empty jar were run before every experiment and used for background subtraction.
All mass spectra up to m/z = 315 were simultaneously detected and
recorded with 1 s as integration time. Internal calibration was based on m/z
= 18.0338 (NH4+), m/z
= 21.0202 (H318O+) and m/z = 29.9974 (NO+).