乌鲁木齐河源1号冰川表层雪的化学特征——以低分子有机酸和无机阴离子为例

Chemical Characteristics of the Surface Snow on Glacier No.1 at the rümqi River Head:Organic Acids and Inorganic Anions

表层雪是联系大气成分与冰芯记录的重要纽带,是研究成冰作用过程中化学组成变化的起点.为配合天山乌鲁木齐河源1号冰川成冰作用过程中化学组成变化的研究,对1号冰川积累区(海拔4130 m)一个完整年度的表层雪样品进行了低分子有机酸和无机阴离子含量的分析.结果显示:表层雪中低分子有机酸主要有HCOO-、CH3COO-、C2H5COO-和(COO)22-,无机阴离子主要有F-、Cl-、NO2-、NO3-、SO42-和PO43-.除(COO)22-外,大部分高浓度的有机酸和无机阴离子因受到周围环境和盛行风的影响呈现出明显的季节变化特征,即夏半年离子浓度变化剧烈,最大值和最小值同时出现在夏半年,冬半年的浓度则相对小而稳定;而(COO)22-和低浓度的无机阴离子随季节变化的特征不明显,在全年均显示出波动性.在外界条件不变的情况下,表层雪可以长时间(至少半年时间)保存其中高含量的化学组成不被改变.

Surface snow links the atmosphere and the ice core in geochemical compositions, thus, it is a benchmark for identifying post depositional changes of the geochemical constituent in the ice forming processes. For monitoring the variations of chemical composition in the transforms from snow to ice, snow samples collected during March 2004 to March 2005 field campaign from the accu- mulation zone of the Glacier No. 1 at the UrOmqi River head, Tianshan Mountains, China, were analyzed for low molecular weight organic acids and inorganic anions. The organic acids in the snow include HCOO^-, CH3COO^-, C2H5COO^- and （COO）2^2-, while the inorganic anions are F^-, Cl^-, NO2^-, NO3^-, SO4^2- and PO4^3-. Most of the organic acids, except for （COO）2^2- and high-concentration inorganic anions as Gl^-, NO3^- and SO4^2-, demonstrate seasonal variations from April to September, which are caused primarily by strong local atmospheric circulations and the prevailing westerly in the seasons, with much even concentrations in the winter. All the anions change considerably from the late spring to early autumn, and reveal both the lowest and highest concentra- tions in a year. On the other hand, （COO）2^2- and low-concentration inorganic anions as F^-, NO2^-and PO4^3- show high variations in the whole year. Analyzed results indicate that the majority of high concentration anions can be preserved in the surface snow for a long time （at least half a year） without weather change condition in their concentrations if the remains relatively stable