祁连山老虎沟12号冰川微粒在沉积后过程的变化特征

Post-depositional process features of the insoluble microparticles on the Laohugou Glacier No.12,Qilian Mountains

2008年10月和2009年10月在祁连山老虎沟12号冰川积累区采集了2个雪坑样品,通过样品中δ18O、可溶性离子、不溶性微粒的变化特点划分了雪坑季节.2008年雪坑季节变化信号明显,而2009年雪坑不明显,微粒浓度、Ca2+与Mg2+含量在春季较高.离子平衡、p H值、电导率及同期气象记录观测资料均显示,2009年雪坑受淋溶影响较大.淋溶强烈时,受融水造成的粉尘溶解及离子淋溶的影响,雪坑中微粒与Ca2+、Mg2+变化趋势不甚一致;与Ca2+相比,Mg2+变化能够较好表征微粒的变化;d>5μm的微粒可能更易于溶解迁移.通过分析室内雪冰样品在液态下的变化,发现伴随静置过程微粒的质量浓度呈下降的趋势,期间Ca2+、Mg2+却呈现增加的变化,可能与碳酸盐矿物的溶解有关.

In October 2008 and October 2009, two snowpits were dug in the Laohugou Glacier No. 12, the biggest glacier in the Qilian Mountains, from which snow and ice samples were collected. The seasonality of snow accumulation was determined based on 5180, insoluble microparticles and major ion profiles of the pits. The seasonal signal in the snowpit dug in 2008 was clear while it was inconspicuous in the snowpit dug in 2009. The number and volume concentrations of insoluble microparticles, calcium and magnesium records all presented higher values in spring. Due to the effects of dust dissolving and ions eluviation, the microparticles content of calcium and magnesium presented different variation tendency while strong eluviation events occurred. Magnesium could represent the variation of microparticles better than calcium. Microparticles with diameter larger than 5 μm might be easier for dissolution and migration. By analyzing the insoluble and soluble microparticles in snow samples changing with time under liquid state, it is found that microparticle mass concentration decreases with time, when calcium and magnesium increase with time, possible in relation to dissolve of carbonate minerals.