张玉玺,刘景涛*,张媛静
In
order to reveal the formation mechanism of hydrochemical characteristics in
Tongchuan City, we collected and detected 39 samples of underground water.
Correlation analytical method, hydrochemical method and ion ratio coefficient
method were employed to investigate the hydrochemical characteristics,
influencing factors and principles of changing. Results demonstrate that the
main factors, controlling the shallow water salinization, are the SO42-, NO3-,
Cl- and K+. The contents of SO42-, NO3- and Cl- are in great differences and
other indexes are in relatively stable. The values of γNa/γCl demonstrate that
the Na+ is released from the aquifer of soil in the process of runoff. There is
an exchange between the Ca2+ in water and Na+ in soil, which leads to γNa>γCl. As the exchange time
in deep water is longer than that of shallow water, the exchange and adsorption
of ions are more sufficient. The value of γNa/(γNa+γCl) demonstrates that with the
increasing of ground water depth, the level of cation exchange enhances, which
leads to the dominant cation turns to Ca2+ from to Na+. The value of γHCO3+γSO4/γCa+γMg
demonstrates the shallow water is mainly from atmospheric rainfall and the
influence of cation exchange is more obvious on deep water. The types of
shallow water in Tongchuan City are mainly HCO3?SO4-Ca. Its classification is
relatively complex. Whereas, the deep water is mainly HCO3-Na and the category
of underground water is simple. As for shallow water, the contents of alkaline
earth metal is larger that of alkali metal. For the deep water, the content of
weak acid group is larger than that of strong acid group. In the region of
upper reaches, the feature of both shallow water and deep water are mainly weak
acid and alkaline earth metal. The chemical composition mainly consists of
carbonate leaching. With the flowing of underground water, the shallow water
turns to be strong acid and alkaline earth metal and the deep water turn to be
weak acid and alkali metal.