Comparative Study of Atmospheric Water-Soluble Organic Aerosols Composition in Contrasting Suburban Environments in the Iberian Peninsula Coast

Abstract

[Abstract] This study investigates the structural composition and major sources of water-soluble organic matter (WSOM) from PM2.5 collected, in parallel, during summer and winter, in two contrasting suburban sites at Iberian Peninsula Coast: Aveiro (Portugal) and Coruña (Spain). PM10 samples were also collected at Coruña for comparison. Ambient concentrations of PM2.5, total nitrogen (TN), and WSOM were higher in Aveiro than in Coruña, with the highest levels found in winter at both locations. In Coruña, concentrations of PM10, TN, and WSOM were higher than those from PM2.5. Regardless of the season, stable isotopic δ13C and δ15N in PM2.5 suggested important contributions of anthropogenic fresh organic aerosols (OAs) at Aveiro. In Coruña, δ13C and δ15N of PM2.5 and PM10 suggests decreased anthropogenic input during summer. Although excitation-emission fluorescence profiles were similar for all WSOM samples, multi-dimensional nuclear magnetic resonance (NMR) spectroscopy confirmed differences in their structural composition, reflecting differences in aging processes and/or local sources between the two locations. In PM2.5 WSOM in Aveiro, the relative distribution of non-exchangeable proton functional groups was in the order: HC (40–43%) > HCC (31–39%) > HCO (12–15%) > Ar-H (5.0–13%). However, in PM2.5 and PM10 WSOM in Coruña, the relative contribution of HCO groups (24–30% and 23–29%, respectively) equals and/or surpasses that of HCC (25–26% and 25–29%, respectively), being also higher than those of Aveiro. In both locations, the highest aromatic contents were observed during winter due to biomass burning emissions. The structural composition of PM2.5 and PM10 WSOM in Coruña is dominated by oxygenated aliphatic compounds, reflecting the contribution of secondary OAs from biogenic, soil dust, and minor influence of anthropogenic emissions. In contrast, the composition of PM2.5 WSOM in Aveiro appears to be significantly impacted by fresh and secondary anthropogenic OAs. Marine and biomass burning OAs are important contributors, common to both sites.