RESUMEN
PM2.5 samples of four seasons were collected from Nov. 2014 to Aug. 2015 at the site of Shengsi island in Zhoushan islands. Mercury (Hg) and speciated mercury concentrations in PM2.5 samples were measured by Atomic Fluorescence Spectrometry (AFS-9130, China) after digestion with CEM Mars Xpress (PyNN Corporation, USA). The concentrations of organic carbon (OC) and elemental carbon (EC) in PM2.5 samples were determined by thermal/optical carbon analyzer (DRI, USA). The results showed that the daily concentrations of PM2.5-bounded mercury (PBM) ranged from 0.02 to 1.25 ng·m-3. Moreover, the mass content of PBM was (12.46±18.79) µg·g-1, which was higher than those in continental cities. ANOVA analysis result suggested that the highest average mass concentrations of PBM occurred in fall, sequentially followed by spring, winter and summer. Higher concentrations of PBM were in fall and spring, which might be related to biomass burning. In addition, RPM took the highest fraction of 53.1% in PBM, followed by HPM (27.3%) and EPM (19.7%), which might be resulted from the complicated composition of marine aerosols. The strong correlations among OC, EC and PBM indicated that carbonaceous composition may affect the transport of Hg in the atmosphere. The ratio of OC/EC represents atmospheric photo-oxidation capacity, so the positive correlation between OC/EC ratio and HPM indicated that HPM was resulted from atmospheric gas-particle transformation. The negative correlation between Char-EC/soot-EC and mercury species indicated that the atmospheric particle-bounded mercury might come mainly from the input of external mercury sources.