上海工业区大气颗粒物中硫的化学形态和分布

用低压冲击式采样器 (DLPI) 采集了上海工业区和郊区大气中28nm~9.92μm粒径范围的颗粒物样品,用同步辐射X射线吸收近边结构谱(XANES)和X射线荧光分析(SRXRF) 对样品中硫的化学形态和含量进行了研究.结果表明,粗颗粒物和细颗粒物中的硫,大部分以硫酸盐形式存在；超细颗粒物中除了硫酸盐硫之外,一部分硫以低价的还原态形式存在,可能的化学形态为金属硫化物、噻吩类有机硫化物.细粒子中硫的质量浓度高于粗颗粒,约 70%的硫分布在细粒子中.硫的质量浓度呈多模态分布.工业区的超细颗粒物峰值出现在0.091~0.154μm;细颗粒的分布为积聚模,峰值出现在0.38~0.611μm;粗颗粒分布为粗模态,在1.59~3.98μm和6.57~9.92μm出现2个峰值.郊区的超细颗粒物中硫的质量分布不存在峰值;积聚模出现两个亚模态,分别为峰值在0.261~0.380μm的“凝结模态”和峰值在0.611~0.945μm的“液滴模态”;粗模态峰值在2.38~6.57μm.污染来源和颗粒物形成、转换机制以及不同采样时间的气象条件差异决定了2个地区颗粒物中硫的分布特性,工业区颗粒物中硫的来源有海盐源的贡献,而郊区较少受海洋源的影响.

Speciation and distribution of sulfur in size-fractionated particulate matters in industrial district of Shanghai

Airborne particles were collected at industrial district and suburban area in Shanghai using a 13-stage Dekati low pressure impactor covering a size range from 28nm to 9.92μm. Synchrotron radiation techniques of X-ray absorption near-edge structure spectroscopy (XANES) and X-ray fluorescence spectrometry (XRF) were employed. Sulfate was the dominant form of sulfur in both coarse and fine particles. In addition, a small amount of sulfur was also present as metal sulfide and thiophenic forms in ultrafine particles. Mass concentration of sulfur in fine particle was higher than that in coarse particle, and it constituted up to 70% of the total sulfur. Size distribution of sulfur in particle from industrial district showed multimode: ultrafine particle mode with peak at 0.091~0.154μm, accumulation mode with the peak at 0.38~0.611μm, and two coarse particulate modes with peaks at 1.59~3.98μm and 6.57~9.92μm. In contrast, ultrafine particle mode was not present in particles from suburb area, and two sub-modes of fine particles could be observed: condensation mode with the peak at 0.261~0.380μm and droplet mode with the peak at 0.611~0.945μm. Moreover, coarse particulate mode had a peak at 2.38~6.57μm. Differences in sulfur mass distribution of particles between industrial district and suburb could be attributed to local and regional sources, weather conditions, formation and conversion mechanisms of particles. Contribution of the sea to particles in industrial district was greater than that in suburb.