Nontarget screening of a Siberian ice core reveals changes in the pre-industrial to industrial organic aerosol composition.

Glaciers serve as natural archives for reconstructing past changes of atmospheric aerosol concentration and composition. While most ice-core studies have focused on inorganic species, organic compounds, which can constitute up to 90% of the submicrometer aerosol mass, have been largely overlooked. To our knowledge, this study presents the first nontarget screening record of secondary organic aerosol species preserved in a Belukha ice core (Siberia, Russian Federation), ranging from the pre-industrial to the industrial period (1800-1980 CE). We identified a total of 398 molecules, primarily polar and low-volatile compounds. Since the 1950s, the atmospheric aerosol composition has changed, with the appearance of organic molecules, including nitrogen-containing compounds, deriving from enhanced atmospheric reactions with anthropogenic NOx, or direct emissions. In addition, there was a significant increase in the oxygen-to-carbon ratio (+3%) and the average carbon oxidation state (+18%) of the detected molecules compared to the pre-industrial period, suggesting an increased oxidative capacity of the atmosphere.