Mercury concentration and isotopic composition on different atmospheric particles (PM10 and PM2.5) in the subtropical coastal suburb of Xiamen Bay, Southern China

The concentration and isotopic composition of particulate-bound mercury (PBM) on both PM2.5 and PM10 were simultaneously measured (24 months) in a typical subtropical coastal suburb of Xiamen bay (SCXB), southern China. The results showed that most mercury was concentrated in PM2.5 and small particulates enriched heavier isotopes of mercury more than lighter ones. Negative Δ199Hg values and slightly positive Δ200Hg values were observed in both PM2.5 and PM10. PBM input sources were identified with isotopic compositions and meteorological data using the NOAA HYSPLIT model. It revealed that biomass combustion is the main source of particulate mercury in SCXB, and the two other sources are urban anthropogenic emissions and potential marine sources. Seasonal variations in isotopic composition and correlation analysis suggested that PBM in SCXB mainly originate from inland after long-distance transportation in spring and under the influence of oceanic air masses in summer. The Δ199Hg/Δ201Hg ratios in all samples (1.01 ± 0.05, 2SE) indicated that the photoreduction of Hg(II) in the aerosol was the main reaction process of PBM transformation in the atmosphere. Seasonal variations in Δ200Hg values were also found, indicating the possibility of even mass independent fractionation in tracing the mercury sources. [Display omitted] •Hg isotopic compositions on PM10 and PM2.5 were monitored simultaneously for the first time.•Biomass consumption has been the dominate Hg source of atmospheric particulates.•Inland and ocean air masses were the main factors that influenced Hg isotopic characteristics.•The observed seasonal difference of Δ200Hg could be used to identify Hg sources.