Impact of Chemical Composition on Aerosol Scattering: Insights from the Surface Particulate Matter Network and Aerosol Robotic Network

Abstract

Using the Surface Particulate Matter Network (SPARTAN) and Aerosol Robotic Network (AERONET), we investigated the relationship between aerosol chemical composition and optical properties across 14 global sites. The mass concentrations of ammonium sulfate (AS), ammonium nitrate (AN), fine soil (FS), and black carbon (BC) from SPARTAN were collocated with aerosol optical properties (aerosol optical depth (AOD), fine mode fraction (FMF), and single scattering albedo (SSA)) from AERONET. Significant differences in the optical properties of samples from 2016 to 2023 were identified based on the mass and mass ratios of the chemical components. For the BC–FS relationship in the data set used in this study, increased FS mass lowered FMF and dSSABC–FS(SSA440–SSA870) by approximately 0.033 and 0.005 per 1 μg/m3, respectively. Higher ratios of nonabsorbing components (AS and AN) to BC (w = (AS + AN)/(AS + AN + BC)) increased SSA at all wavelengths. The correlation between w and SSA was stronger at longer wavelengths, with SSA440and SSA1020increasing by approximately 0.026 and 0.046 per 10% increase in w from the data set, respectivley. Site-specific results showed that dSSAwand rSSA (SSA440/SSA1020) increased as the BC proportion rose (w decreased). This study emphasizes the utility of both dSSA and rSSA, alongside single-wavelength SSA, in understanding aerosol behavior. Integrating columnar optical data with surface-level chemical measurements, the combined SPARTAN and AERONET approach offers valuable insight into aerosol classification, behavior, and atmospheric impacts.