1 Hydrological characteristics and trace elements

Our results show that the pH of melted snow and ice samples is approximately neutral (Table II) (Reference Vilenskiy and MiklishanskiyVilenskiy and Miklishanskiy 1976, Reference Wang, Wang and LiuWang Ping and Liu Zhi 1982, Reference Wang and WangWang Ping and others 1983); however, a snow sample from Galongla glacier had a pH of 4.25, which is unusually low for the area studied. The degree of mineralization of the samples was also low, samples from “Hars”, Gonggashan, and Duoxiongla glaciers generally containing less than 15 mg 1⁻¹ of dissolved mineral salts. This shows that the snow and ice of Chinese glaciers are generally fresh and extremely soft.

Table II The Degree of Mineralization and Hydrochemical Type in Snow and Ice Samples

Table III summarizes the measured concentrations of trace elements and heavy metals. Concentrations of Mg, Co, Cr, Sr, Ni, Cu, Zn, V, Pb, Ti, Sn, Hg, Ag and Se were all found to be below the maximum permissible levels for harmful metals in groundwater, as published by the Department of Health in China in 1963. However, the levels of As and Cd were found sometimes to exceed the maximum safe concentrations; for example, the levels of As in samples taken from Dunte flat-topped glacier and Zelonglong glacier were above 50 ppb, and samples from Zelonglong, Galongla, Namula, and Duoxiongla glaciers showed Cd levels in excess of 10 ppb (the National Standard).

Table III Concentration of Trace Elements in Snow and Ice

2 Impurity enrichment factors

Table IV shows measured enrichment factors for major impurities in Chinese mountain glaciers (Reference Boutron and LoriusBoutron and Lorius 1977, Wang Ping and Luo Hongzhen 1980, Reference Luo and LoLuo Hongzhen 1983, Reference Wang and WangWang Ping 1983). The order of enrichment of the major ions was found to be:

Table IV Element Enrichment Factors in Snow and Ice

This shows that the pathways of water replenishment vary with locality in the mountainous regions of China, and that it is mainly controlled by the high atmospheric oceanic water vapour.

3 Tritium measurements

Tritium measurements can be used to estimate the annual accumulation and mean accumulation ratios (Reference Boutron and LoriusBoutron and Lorius 1977, Reference Wang, Wang, Luo, Lo, Lin, Wei and WangWang Ping and others 1984). We found environmental tritium levels in the range from 13 to 196 TU in samples of precipitation from the Altay, Tianshan, Qilian, Gonggashan, Tanggula and Kunlun mountains and from the Nanjiabawa Peak area (Table V). We also determined mean annual accumulation ratios of 618 mm a⁻¹ (west Qiongtailan glacier), 645 mm a⁻¹ (“Hars” glacier), and 424 mm a⁻¹ (“No.1 glacier”).

Table V Tritium Content in Snowfall for Mountain Areas

Tritium data can also be used to calculate the percentage of local vapour in the air and precipitation of glacial regions (Reference Wang, Wang, Luo, Lo, Lin, Wei and WangWang Ping and others 1984). Based on these results, local contributions were calculated:

Finally, we can use tritium measurements to separate the different contributions to the total glacier run-off. Analysis of the tritium content at the source of Qiongtailan River, Mt Tuomer, by Wang Lilun (Wang Li-lun), Su Zhen (Su Chen) and Zhang Wenjing (Chang Wen-ching) in July 1978 shows that glacier meltwater accounts for 34% and precipitation for 66% of the total glacier run-off. Table VI shows results obtained by the present author for “No.1 glacier” at the source of the Urumqi River, Tianshan mountains (Urumchi River, Tien Shan) at different times during 1983.

Table VI The Percentage of Glacial Meltwater in Glacier No 1 at the Source of Urumqi River