Fig. 5: Particle number concentration smaller than 2.5 nm and concentrations of different type of HOMs.

Median values of hourly means during night hours (18:00–09:00). The HOMs are separated by the formation mechanism (see Table 1 in SI). HOMs formed from monoterpene and sesquiterpene in absence of NOx are clearly responsible in particle formation, while HOMs that contain one or two nitrogen atoms are not well correlated with particles with the exception of CHON dimers. Correlation coefficient (R) and statistical significance (p) are calculated for all nights combined. Panel a) monoterpene oxidation products containing C, H, and O, 10 carbon-containing molecules; b) same as panel a) but 20 carbon molecules; c) monoterpene oxidation products containing C, H, O, and N. 10 carbon molecules; d) same as panel c) but 20 carbon molecules; e) monoterpene oxidation products containing C, H, O, and 2 N atoms, 10 carbon molecules; panel f) sesquiterpene oxidation products containing C, H, and O, 15 carbon molecules.