Applications of non-destructive spectroscopic techniques and multivariate statistics for the analysis of atmospheric aerosol collected on membranes

This work presents applications and relevant achievements from two non-destructive, time-saving, and low-cost spectroscopic techniques on particulate matter (PM) samples collected on filters: Ultraviolet-Visible (UV-Vis) diffuse reflectance spectroscopy and Fourier transform - Infrared (FT-IR) spectroscopy in transmission mode. The case studies below reveal how the inventive combination of spectroscopic measurements with advanced statistical methods can quickly provide information about the atmospheric aerosol emission sources. UV-Vis spectroscopy The acquisition of UV-Vis spectra of PM collected on polytetrafluoroethylene (PTFE) or quartz membranes can provide parameterization and digitization of the filter colours (e.g., Morozzi et al., 2021), as well as identify groups of samples with similar optical behaviour. This application shows how the colour-based clusters may offer information on the chemical composition and related emission sources of PM from a different perspective. Red tones are related to the influence of iron oxide (mainly hematite) from mineral dust, while black tones are affected by carbonaceous component from biomass burning. These outcomes may be utilized to investigate the radiative forcing of climate by differently coloured suspended particulate matter. FT-IR spectroscopy The acquisition of FT-IR spectra of PM collected on PTFE membranes may provide reliable qualitative and quantitative information on ambient aerosol sources and aging. Indeed, after baseline correction by the AIRspec platform (e.g., Reggente et al., 2019), spectral data can be even subjected to Positive Matrix Factorization (PMF, Belis et al., 2019). It is shown, therefore, how in the present case study this method can solve three emission sources: Factors 1 and 2 that are linked with anthropogenic emissions from biomass combustion and urban traffic, respectively; Factor 3 that is associated with mineral dust transport.