Variation Features of Chemical Composition in Snow Cover
in the Western Part of the Tianshan Mountains, China
Wei Wenshou1, Jiang Fengqing1, Li Weihong1, and Liu Mingzhe1
Seasonal snow cover is thick in the western part of the Tianshan Mountains, China. Its maximum
depth can be up to 150 cm, and its multiyear average maximum depth is 86 cm. Because snow cover
plays a unique role in monitoring environmental pollution, the western part of the Tianshan Moun-
tains, China, is selected as the study area of the variation of chemical composition in polluted snow
cover. The analysis of snow samples shows that the mean values of the main anions and cations in
seasonal snow cover are 0.6215.8 Mg/L. Generally, the ionic concentration of fresh snow is higher
than that of whole snow cover (excluding Mg2+ and Ci). The concentration of K+ + Na+ is relatively
high in cations; their average values occupy 60% and 38% of the average ionic value, respectively. In
anions, the content of SO2- is obviously higher than that of other anions, which is about 60% of the
4
total. The pH value of snow cover is about 6.5. Correlative analysis results show that snow pollution
is mainly affected by continental sulfate and heavy carbonate. The analysis results of the spatial
variation of anions and cations show that the ionic concentration of SO2- and K+ + Na+ has a
4
lowering tendency with of elevation. However, it has an obvious high value in the areas where
human activities are frequent. Therefore, one of the main factors causing a spatial variation of SO2-
4
and Na+ is local human activity.
The analysis results of temporal variation of anions and cations show that the variation of ionic
concentration of Mg+ is small, and that of K+ + Na+ and Ca2+ is obvious. The variation tendency has
a positive correlation with air temperature. This variation tendency is mainly caused by increase or
decrease of dust amounts in air because most of the land surface in the study area and the Middle
Asia is covered by snow during the snow-cover period. The snow reduces the amount of dust going
into air while the amount of dust going into air increases along with the exposing of land surface in
snow-melting season under the effect of wind, human activities, and animal movement. Except for
the uncovered land surface, dried lake basins and deserts eroded by wind in the Middle Asia are the
material sources of sulfates in pollutants of snow cover in the western part of the Tianshan Moun-
tains. The variation of chemical composition in the polluted snow cover is also strongly influenced
-
by human activities. The spatial distribution of K+ + Na+, SO2- , Ca2+, and HCO3 varies obviously
4
in anions and cations in both fresh snow and old snow cover; the regional features are basically the
same. Therefore, except for the change of natural environment, human activities are the main factors
causing a high ionic concentration. Temporal variation of anions and cations in fresh snow is mainly
influenced by scope, depth, and duration of snow cover, and is controlled by regional atmospheric
circulation and temperature. Therefore, with a deep snow cover with an extensive distribution in
midwinter, correspondingly, ionic concentration of pollutants is low.
1
Xinjiang Institute of Geography, 40 South Beijing Street, Urumqi, 830011 Xinjiang, China
66
Previous Page
