祁连山老虎沟12号冰川积雪中飞灰颗粒物的特征

冰川积雪中的飞灰颗粒物可指示由大气沉降的人类活动污染物.本研究基于2012年6月在青藏高原东北缘的祁连山老虎沟12号冰川夏季野外观测取样、实验室扫描电子显微镜与X射线能谱仪联用系统(SEM-EDX)分析了积雪粉尘中球形颗粒物的特征信息,以弄清冰川区沉降的球形飞灰颗粒物的理化特征及其环境意义.结果表明,在所选取的雪层不同深度的9个积雪样品中,都存在着一定数量的飞灰颗粒,这些颗粒物通常是人类生产活动中的化石燃料高温燃烧所形成的.基于EDX能谱分析了飞灰颗粒物的化学元素成分组成,认为沉积在祁连山冰川积雪中的飞灰主要分为3种类型,分别为"富Si类"、"富Fe类"和"富Ti类"颗粒物.总体上,"富Si类"和"富Fe类"颗粒占了球形飞灰颗粒的绝大部分.这些不同组分的飞灰代表了污染物的不同生产活动来源,其平均粒径要相对大于雪层中自然来源的所有矿物粉尘颗粒物,反映了大气传输远距离中密度对粉尘颗粒的重要性.结合NOAA Hysplit气团后向传输轨迹分析认为,中亚地区和我国新疆地区城市、及研究区周边的工业燃烧物通过大气传输是祁连山老虎沟12号冰川积雪中飞灰颗粒的主要可能来源.

Characteristics of Fly Ash Particles Deposition in the Snowpack of Laohugou Glacier No.12 in Western Qilian Mountains, China

This research aimed to identify and characterize individual spherical fly ash particles extracted from surface snow at Laohugou Glacier No.12, western Qilian Mountains, China. Characterization of the spherical particles (i.e. morphology, chemical composition and genesis) was obtained by scanning electron microscopy coupled with energy dispersive X-ray spectrometer (SEM-EDX). Spherical particles and agglomerates were identified according to their morphology in nine snow samples. Prevalent particle types in all samples were granular spherical particles, hollow spherical particles, and agglomerates. The vast majority of spherical particles in our samples had mostly smooth and glossy surfaces. Individual particle analyses of elemental composition showed that particles formed in combustion were mainly composed of silicon, aluminum and trace elements. On the basis of chemical information obtained from EDX, the fly ash particles deposited in the snow could be classified into three types, which were Si-dominant particles, Fe-dominant particles, and Ti-dominant spherical particles. Backward air mass trajectory and dispersion analysis suggested that the developed urban regions of central Asia and surrounding Yumen city contributed the primary fly ash particles from industrial combustion to the study site through the high-level atmospheric circulation.