Isotopic composition for source appointment of mercury in PM2.5

Previous studies have reported mass-dependent fractionation (MDF) and mass-independent fractionation (MIF, for both odd isotopes (odd-MIF) and even isotopes (even-MIF)) of mercury (Hg) isotopes in natural samples, and... [ view full abstract ]

Previous studies have reported mass-dependent fractionation (MDF) and mass-independent fractionation (MIF, for both odd isotopes (odd-MIF) and even isotopes (even-MIF)) of mercury (Hg) isotopes in natural samples, and demonstrated the potential of Hg isotopes for studying the biogeochemical cycle of Hg. However, the usefulness of Hg isotopes for tracing the sources and pathways of Hg (and its vectors) in atmospheric fine particles (PM2.5) has not been tested.
In this study, we measured Hg isotope ratios of 30 potential source materials and 23 PM2.5 samples collected in four seasons from the center of the largest and most populated City Beijing in China, with a goal of tracing the possible sources of Hg (and the relative particles) by coupling Hg isotopic compositions with geochemical parameters and meteorological data. All PM2.5 samples displayed clear seasonal variations of both Hg isotopic compositions and elemental concentrations. This seasonal variation was likely caused by variable contributions of potential sources, with continuous industrial input in four seasons, while dominated impact of coal combustion in winter and significant contribution from biomass burning in autumn. The long-range transport was also a contributor to PM2.5-Hg, which explained the relatively higher odd-MIF particularly found in Spring and early Summer. Our study demonstrates Hg isotope approach is a powerful tool for tracing the sources (and pathways) of Hg and its vectors in the atmosphere, and stresses the importance of studying toxic metals such as Hg (and other heavy metals) in atmospheric particles and their potential threat to human health during hazes episodes.