天山东部冰川积雪中大气粉尘的沉积特征

Characteristics of Modern Atmospheric Dust Deposition in Snow on the Glaciers of East Tianshan Mountains, China

对我国天山东部三个研究点乌鲁木齐河源1号冰川、奎屯哈希勒根51号冰川和哈密庙尔沟平顶冰川积雪中大气粉尘沉积进行了分析研究。微粒特征分析表明,自西向东随着研究点地理环境的变化,积雪中不溶微粒的质量浓度、沉积通量和体积粒径分布众数都表现出增高趋势:奎屯哈希勒根51号冰川最小,乌鲁木齐河源1号冰川次之,哈密庙尔沟平顶冰川最大;三个研究点粒径0.57<d<26!m微粒的平均质量浓度分别是969"g/kg、1442#g/kg、3690$g/kg,年均沉积通量分别是58.2%g/cm2、72.1&g/cm2、73.8’g/cm2。表明,哈密冰川受粉尘源影响较大,而乌鲁木齐河源与奎屯河源区受影响则相对较小。雪坑微粒浓度剖面和离子相关性分析表明,天山东部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3-22(m,粒径分布显示了单结构模式。研究区最近4年积雪的污化层剖面揭示了春季零星的粉尘浓度峰值以及沉积数量上较大的年际变化,意味着天山东部雪冰中粉尘沉积对大气环境变化的敏感性。

Deposition of atmospheric dust was measured in snow deposited on Glacier No. 1 at the headwater of Urumqi River, Haxilegen Glacier No.51 in Kuitun and Miaoergou Glaicer in Hami in East Tianshan Mountains, western 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 East Tianshan Mountains is different from each other. The characteristics of modem atmospheric dust deposition in snow is different among three research points in East Tianshan Mountains, as the environment changes from west to east. Mean mass concentration of microparticles with 0.57 〈 d 〈 26 μm in the snowpack is 969 μg/kg, 1442 μg/kg and 3690 μg/kg in three study sites, respectively. Dust flux to East Tianshan Mountains has a range of 58.2-73.8 μgcm^-2a^-1 for particles with 0.57 〈 d 〈 26 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 with duat＇s. Volume size distributions of dust particles in the snow showed single-modal structures having volume median diameters from 3-22 μm. Dust profiles in snow cover over the last 4 years reveal frequent sporadic high dust concentrations and large year-to-year variations in the amount deposited, implying that dust deposition in East Tianshan Mountains is very sensitive to atmospheric environmental change.