Mercury Species in Atmospheric Particles and Their Dependent Conditions

The cascade impactor and PM10 sampler were used to collect atmospheric particles in the south Shanghai.Chemically,the sequential extraction method was applied to detect the exchangeable particle-phase mercury(ExPM),hydrochloric soluble mercury(HPM),elemental particle-phase mercury(EPM) and residual particle-phase mercury(RPM).Results showed that the average concentration of total Hg in particulate matters as,ρ(total-Hg) was 0.48 ng/m3(0.07-1.44 ng/m3),of which 47.8% was in PM1.6(particulate matter with diameter ≤1.6 μm.The average content of the total Hg content,w(total-Hg),in particulate matters was 1.81 μg/g(0.35-6.89 μg/g) which was greatly higher than that in the coal or cement.Mercury in particles showed a signivicant seasonal variation and ρ(total-Hg) that it was higher in winter and spring;while it was lower in summer.The bimodal pattern of diurnal variation of ρ(total-Hg) in PM10 was found while no distinct diurnal of w(total-Hg) was found.The concentration of difference mercury species was detected higher in nighttime than that at daytime.The mercury species were impacted by meteorological conditions and sources distribution.Except in spring of 2006,w(HPM) in particle displayed the similar level in other seasons and higher ρ(EPM) was observed in winter of 2005 and spring of 2006 which were 0.19,0.17 ng/m3,respectively.HPM and EPM were mainly concentrated in fine particles while RPM in 1.6 μm and 1.6-3.7 μm were not significantly different.The ρ(total-Hg) and ρ(RPM) negatively correlated with temperature,daily temperature difference,relative humidity while positively with ρ(SO2),while both ρ(HPM) and ρ(RPM) showed different correlations.The results determined by the sources and atmospheric behavior of HPM and EPM,HPM were easy to dissolve in liquid phase and was associated with solar-light dependent photochemical reactions,while EPM depended on contributions of combustion sources and the deposition velocity.