Non-target screening ice-core analysis reveals changes in the atmospheric organic aerosol composition between the pre-industrial and industrial periods

Organic aerosols constitute up to 90% of submicron aerosol mass, playing a crucial role in influencing the Earth’s radiative forcing by absorbing and scattering incoming solar radiation, as well as acting as cloud condensation nuclei. To unravel the complexity of organic aerosol (OA) chemical composition, recent analytical advances, such as high-resolution mass spectrometry and the development of non-target screening (NTS) workflows, have been applied to present-day atmospheric aerosol samples. However, for a better understanding on how human activities have influenced OA chemistry, it is essential to unravel its changes between the pre-industrial and industrial periods.

In this study, we present the first application of a novel NTS method to an ice core from the Belukha glacier (Russian Federation), covering the period from 1800 to 1980 CE. A total of 398 molecules were identified, mainly secondary organic aerosol tracers (SOA), such as mono- and di-carboxylic acids. Since the 1950s, we observed a shift in the atmospheric aerosol composition, characterized by the appearance of organic molecules—such as nitrogen-containing compounds—that result from increased atmospheric reactions with anthropogenic NOx or direct emissions. Additionally, we recorded a significant increase in the oxygen-to-carbon ratio (+3%) and the average carbon oxidation state (+18%) of the detected compounds compared to the pre-industrial period, suggesting an increased oxidative capacity of the atmosphere, associated with enhanced tropospheric ozone concentrations.

This work demonstrates the potential of NTS ice-core studies for extending the reconstruction of OA chemical composition prior to the advent of direct instrumental monitoring, providing valuable contributions to the atmospheric aerosol community.