Influence of sources and atmospheric processes on metal solubility in PM2.5 in urban Guangzhou, South China

Abstract

Water-soluble metals exert a significant influence on human and ecosystem health. In this study, a comprehensive investigation was undertaken to elucidate the solubilities of metals in PM_2.5 and potential influencing factors during the dry season of 2019-2020 in urban Guangzhou, South China. The observed average solubility was less than 20% for Al, Fe, Sn, and Ti; 20-40% for V, Cr, Sb, Pb, and Ni; 40-60% for Ba and Cu; and 60-80% for Zn, As, Se, Cd, and Mn. Metals (Al, Ti, and Fe) originated from crustal sources (e.g., soil dust) have much lower solubilities than those (Mn, Zn, As, Se, Cd, and Ba) from fossil fuel combustion sources (e.g., traffic emission, coal combustion), suggesting the dominant role the metal sources played on solubility. Enhanced solubilities of Cu, As, Se, Cd, Sn, Sb, and Pb were associated with aerosol acidity, while those of V, Cr, Mn, Ni, Zn, and Ba were linked to organic acid complexation. For the three crustal metals, the solubilities of Al and Ti primarily depended on aerosol acidity, whereas that of Fe relied on both aerosol acidity and organic acid complexation. These findings underscore the primary influence of inherent metal properties and minor impacts (on average <5% for most species and 7-15 19% for Cu, As, Se, and Cd) of atmospheric physicochemical processes on metal 16 solubilities.