Atmospheric mercury speciation in Shanghai, China

•Hg species at a suburban site in Shanghai were lower than that in most urban areas of China.•Three kinds of atmospheric speciated mercury exhibited totally different diurnal pattern.•No significant correlations between Hg species and air pollutants were found.•PSCF result showed that Shanghai was mainly impacted by local emission.

GEM (Gaseous elemental mercury), fine fraction (< 2.5 μm) PBM (Particle-bound mercury) and GOM (Gaseous oxidized mercury) were continuously monitored from Jun 1 to Dec 31 2014 at a suburban site in Shanghai. The average concentrations of GEM, PBM and GOM were 4.19 ± 9.13 ng·m− 3, 197 ± 877 pg·m− 3, 21 ± 100 pg·m− 3, respectively, which were all much higher than those at urban sites in Europe and North America and rural areas of China, but lower than those at urban sites of China. The concentrations of the three mercury species were all found with the highest concentration in December than those in summer. Overall, GEM varied little and PBM exhibited higher level during the night, while GOM typically peaked in the noon and afternoon which is consistent with that of ozone, indicating that GOM may depend on the stronger photochemical reactions during the daytime. Despite of the weak correlations of GEM with SO2 (r = 0.14, p < 0.0001) and NOX (r = 0.17, p < 0.0001), GEM, PBM, SO2 and NOx exhibited similar diurnal trend, suggesting that coal combustion might be the important sources of mercury in Shanghai because there is no mercury mining companies and few mercuric manufacturers in Shanghai. The strong correlation of PBM with GEM and GOM showed that directly anthropogenic emission was an important source of GEM and PBM, but the gas-particle partitioning of GOM and GEM might be also another source of PBM. The lower GEM/CO ratio of 3.9 (ng·m− 3·ppmv− 1) in Shanghai than that for mainland China and non-ferrous smelting factories were related to the few non-ferrous smelting factories around Shanghai. The results from the potential source contribution function (PSCF) model furtherly illustrated that in Shanghai the concentration of GEM in summer and autumn might be highly impacted by the local and regional source but wasn't heavily affected by long-range transport.

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