CHEMICAL CHARACTERISTICS AND EVOLUTION PROGRESS OF THE PORE-WATER IN KUNMING BASIN

Kunming basin is a fault basin formed on a background of carbonate basement. In the study area, the cations of Ca²⁺ and anions of HCO₃-are dominated in pore water. The common types of the chemical component of pore water are HCO₃-Ca, HCO₃-Ca·Mg and HCO₃·Cl-Ca. Affected by human activities, the chemical composition varies in different areas. The chemical types of groundwater tend complex from basin edge to center. Spatially, the groundwater shows an increasing mineralization from east to west. During the last 20 years, with the rapid urbanization of Kunming city, the quality of pore water evolves in both positive and negative directions. The groundwater mineralization near the Western Mountain and Caohai Lake has reduced yearly; while the deteriorative area is spreading to the outer part of urban districts. The variations of groundwater chemical types indicate that the changes of land use and pollution intensity have greatly impacted the groundwater environmental evolution. Factor analysis of chemical data shows that HCO₃^-, NO₃- and COD concentrations have the highest factor loadings on factor 1, factor 2 and factor 3, which indicate natural evolution process, agricultural and domestic contaminants, and industrial pollutions respectively. The result of the factor analysis indicate that Mg²⁺, Na⁺, Cl^-, SO₄^2- and K⁺ derive from both natural processes and external pollution sources. The industrial pollution source represented by COD also has some influence on the concentration of Cl^-, SO₄^2- and K⁺ in groundwater.