Characterization of aerosol particles containing trace elements (Ga, As, Rb, Mo, Cd, Cs, Tl, and others) and their atmospheric concentrations with a high temporal resolution

Particles with diameters of 2.5 μm and smaller (PM2.5) contain various trace elements and potentially influence human health. Physical and chemical features of individual particles and their concentrations with detailed time trends provide useful information for an accurate estimation of the sources and potential toxicity of PM2.5. Although many studies have measured these features for relatively common elements (e.g., Fe, Zn, and Pb), diurnally concentrations changes and mixing states of particles containing trace elements (below 1 ng m−3) have not been explicitly analyzed. In this study, we observed atmospheric concentrations of 44 elements in PM2.5 using a real-time observation technique (GED-ICP-MS) at Fukuoka, western Japan, during the winter and spring of 2018. As a result, various elements were detected in anthropogenic air masses from long-range transports. We also sampled aerosol particles every 3 h and analyzed their shapes, mixing states, and compositions using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy to demonstrate particle occurrences containing trace elements at an individual scale. We especially focused on the abundance and physicochemical features of aerosol particles containing trace elements, such as As, Ga, Rb, Mo, Cd, Cs, and Tl. The element group Ga, Rb, and Cs and a pair of As and Cd showed significant correlations and we succeeded to observe three Ga-bearing particles, seven As-bearing particles, and three Cd-bearing particles. Moreover, we introduce particle features containing Mo and Tl, which were not reported in previous studies. Our results have implications for understanding the occurrence of trace elements in the atmosphere, identifying aerosol sources, and evaluating the influences of aerosol particles on human health.