Fig. 2
An omnipresent variability in molecular-level composition. The molecular-level composition of functionalized OA varies greatly between multi-hour samples at three diverse field sites, and this variability occurs across abundances, volatilities, and compound classes. a The average (±standard deviation, shown as error bars) percentage of distinct compounds for sample-to-sample comparisons is shown across various sample subsets at each field site, where overlapping compounds are determined by comparing molecular formulas and LC retention times. Markers above and below each average and standard deviation represent the minimum and maximum values of distinct compounds for each set of comparisons. All other sample-to-sample comparisons in each set fell in the range set by the minimum and maximum displayed here. “All consecutive samples” includes consecutive days, consecutive nights, consecutive day–night pairs, and consecutive night-next day pairs. Day- and night-only comparisons for all samples and consecutive samples are also shown. b–d Molecular-level variability in all sample comparisons across all three sites is shown as the distribution of compositional variability (i.e., distinct compounds) across (b) ion abundance ranges (divided into percentiles based on ion count, with corresponding individual analyte mass concentrations on the order of ng/m3), (c) volatility bins (i.e., intermediate/semi/low/extremely-low volatility organic compounds: IVOCs, SVOCs, LVOCs, ELVOCs, respectively), and d compound classes
