大气颗粒物中汞的赋存形态及其依存条件

Mercury Species in Atmospheric Particles and Their Dependent Conditions

于2004—2007年在上海市西南部某采样点使用分级采样器和PM10采样器采集大气颗粒物样品,采用化学序批式提取法分析了颗粒物中的ExPM(可交换汞)、HPM(可溶盐酸汞)、EPM(元素汞)和RPM(剩余汞)4种形态汞的含量.结果表明:颗粒物中ρ(total-Hg)(total-Hg为总汞)在0.07～1.44 ngm3之间,47.8%集中在粒径<1.6μm的颗粒物中;颗粒物中w(total-Hg)在0.35～6.89μgg之间,高于煤炭和水泥中的含量;颗粒物中ρ(total-Hg)在冬、春季较高,夏季较低;PM10中ρ(total-Hg)日变化呈双峰型,然而w(total-Hg)的日变化并不明显.夜间各种形态汞的质量浓度都高于白天.汞的形态受气象条件和污染源分布的影响.除了2006年春季外,其他年份各季节的w(HPM)基本持平;ρ(EPM)在2005年冬季和2006年春季均出现较高值,分别为0.19和0.17 ngm3.HPM和EPM主要集中在细颗粒物上,而RPM在粒径<1.6μm和1.6～<3.7μm颗粒物中的分布无明显差异.颗粒物中的ρ(total-Hg)、ρ(RPM)与温度、日温差、相对湿度呈显著负相关,与ρ(SO2)呈正相关;但ρ(HPM)和ρ(EPM)与这些参数的相关性不同.这可能与HPM和EPM的来源与大气化学特征有关,其中,HPM易溶解于液相,与对光照依赖性很强的光化学反应有关;而EPM主要取决于一次来源的贡献和气态汞沉积速率.

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.