七一冰川消融末期融水化学日变化特征

2006年9月1-8日在祁连山七一冰川作用区水文总控点逐时采集河水样, 并分析水样的主要可溶离子含量、电导率以及pH, 研究冰川作用区水化学组成日变化特征. 结果表明: 消融末期河水中pH的平均值约为7.60, 与离子浓度时间变化过程一致, 说明是偏碱性物质的输入增加了融水中化学物质的含量;SO~(2-)_4, Ca~(2+)分别是浓度最大的阴、阳离子, 属于SO~(2-)_4+HCO~-_3-Ca~(2+)+Mg~(2+)型水. 河水中可溶性离子浓度日变化过程具有不对称性, 表现为快速降低和缓慢的增加过程, 与流量变化呈显著反相关, Pearson相关说明流量是冰川区水化学特征随时间变化的控制性因素;阳离子通量计算显示, 在七一冰川区达54.7 t·km~(-2)·a~(-1), 其日变化过程与流量正相关, 与离子浓度成反相关, 说明径流量也是控制离子通量的主要因素.

Diurnal Variation of Meltwater Chemistry in the Qiyi Glacier during the Late Ablation Period

In order to investigate the diurnal changing characteristics of meltwater chemical composition and ion flux, water samples were collected at hydrological control site of the Qiyi Glacier from 1st to 8~(th) September, 2006. Major soluble ions concentrations, EC, pH and water lever were measured. The results indicate that: mean value of pH is 7.60, which has the same temporal change with major soluble ions, showing the input of alkali substance enhancing the concentration of ions. The dominant cation and anion are Ca~ (2+) , SO~(2-)_4 in the meltwater, of which the concentrations in the late ablation period are higher than those in the early ablation period. Chemical face is SO~(2-)_4+HCO~-_3-Ca~(2+) +Mg~ (2+) . Diurnal variations of major soluble ionic concentrations are asymmetrical, with a quick decrease and a slow increase, and a strong negative correlation with water level change, demonstrating that water discharge is the governing factor for the temporal change of the hydrochemical characteristics. A negative correlation between discharge and ionic concentration and a positive correlation between discharge and cation denudate are found, which indicate that the discharge is the main factor for controlling the change of cation denudation rate. A calculation suggests that the cation denudation rate is 54.7 t·km~(-2) ·yr~(-1) .