祁连山西段冰川积雪中大气粉尘沉积特征

Characteristics of atmospheric dust deposition in snow on the glaciers of western Qilian Mountains

基于2012年夏季野外考察、微粒粒度测试和扫描电镜(SEM-EDX)微观形貌观测研究,对位于我国青藏高原东北缘的祁连山西段典型极大陆型冰川区老虎沟12号冰川、野牛沟十一冰川积雪中大气粉尘沉积进行了分析研究。两冰川区积雪中微粒的平均质量浓度分别是3461μg/kg、2876μg/kg,年均沉积通量分别是207.6μg/cm2、143.8μg/cm2。将本研究区与其他区域冰川积雪中粉尘浓度对比研究表明,冰川受周边粉尘源区影响较大。雪坑微粒浓度剖面和离子相关性分析表明,祁连山西段冰川积雪中污化层富含亚洲粉尘的富Ca2+、Na+矿物;微粒体积—粒径分布众数介于3～22μm,两冰川区的粒径众数分别为12.6μm和12μm,粒径分布均显示了单结构模式,同时反映了祁连山冰川区与毗邻的天山地区雪冰中粉尘粒径分布模式的相似性和粒径众数的差异性。通过SEM-EDX对粉尘颗粒的微观结构研究发现,颗粒绝大多数为形貌不规则的矿物粉尘颗粒,和很少数量的飞灰颗粒等。同时,对粉尘来源结合Sr-Nd同位素测定和气团后向轨迹分析进行验证,认为位于研究区北边的巴丹吉林沙漠是祁连山12号冰川区粉尘最可能的源区。

Deposition of atmospheric dust was measured in snow deposited on Glacier No.12 at the Laohugou River, Shiyi Glacier in Yeniugou of western Qilian Mountains, China. An analysis of horizontal distribution of dust layers, snow height and concentration of dust in the snow cover suggests that deposition of dust in western Qilian Mountains is different from each other. The characteristics of modem atmospheric dust deposition in snow are different among research sites, as the environment changes from west to east. Mean mass concentration of microparticles with 0.57 〈 d 〈 40 μm in the snowpack is 3461 μg/kg and 2876 μg/kg, respectively. Dust flux to westem Qilian Mountains has a range of 143.8-207.6 μg/cm2 for particles with 0.57 〈 d 〈 40 μm. Dust layers in the snow cover contain Ca-rich materials typically found in Asian dust particles. Vertical profile of Na＋ concentration in the snowpack is also very similar to that of dust. Volume size distributions of dust particles in the snow showed single-modal structures having volume median diameters from 3 to 22 μm. SEM-EDX was used for dust micro-topography analysis.