祁连山七一冰川融水化学组成及演化特征

2006-06～2006-07在祁连山七一冰川采集冰川冰、冰面融水、侧碛河及冰川融水径流样,分析了样品中主要可溶离子浓度、pH及电导率.结果表明,所有样品的pH介于8.05～8.79之间,电导率分布在32.4～134.4 μS·cm-1之间.不同水体中主要可溶离子浓度顺序为:冰面融水＜侧碛河＜七一冰川水文总汇点,水化学类型也由HCO3-Ca2 型演化为(HCO3 SO2-)-(Ca2 Mg2 )型.几乎所有样品中主要可溶阴、阳离子浓度序列为:HCO3＞SO2-4＞CI-＞NO-3,Ca2 ＞Mg2 ＞Na ＞K ,以碳酸盐风化产物为主,也有部分硫酸盐贡献.由于受到各种物理化学因素影响,在水岩作用过程中MG2 和K 浓度增加速率大于Ca2 和Na ,不同于其在地壳中的丰度.七一冰川区融水中离子浓度空间变化主要受水岩作用时间控制,气温影响下的冰川消融量的大小是水化学时间变化的主要控制因素.

Hydrochemical Characteristics and Evolution of Runoff at Qiyi Glacier, Qilian Mts.

Glacier ice, supraglacier stream water, ice-marginal stream water, proglacier stream water samples were collected at Qiyi glacier located in central part of Qilian Mountain 2006-06 - 2006-07. Major ions concentration, pH and EC were analyzed. The results indicate that pH varies from 8.05 to 8.79, and EC 32.4 - 134.4 microS cm(-1). The order of major ions concentration in differed water is: supraglacier stream water< ice-marginal stream water < proglacier stream water. Meanwhile, hydrochemical characteristics vary from HCO3(-) -Ca(2+) to (HCO3(-) + SO4(2-))-(Ca(2+) + Mg(2+)). Major ions,almost in all samples; HCO3(-) > SO4(2-) > Cl(-) > NO3(-), Ca(2+) > Mg(2+) > Na(+) > K(+) mainly comes from carbonate weathering,and some is from sulfate dissolution. Concentrations of Mg(2+) and K(+) increase quicker than Na(+) and Ca(2+) in proglacier stream and ice-margin stream that is inverse to their abundance in crust. The spatial characteristic of ions concentration is controlled by the process of water-rock and temporal change is hydrological factors.