昆明盆地孔隙水的化学特征及其演化规律

昆明盆地为一碳酸盐岩基底背景上形成的断陷盆地.研究区内孔隙水中Ca²+、HCO₃^-在阳、阴离子中占有绝对优势，水化学类型以HCO₃-Ca、HCO₃-Ca·Mg、HCO₃·Cl-Ca等为主.受不同区域人为活动影响，地下水各离子组分空间分异较大，水化学类型由盆地边缘向盆地中心呈现出复杂化.在平面上，从盆地边缘向盆地中部的冲湖积平原方向，地下水矿化度具有东西过渡分带的特点，以矣六乡-小板桥-巫家坝-联盟镇为界，东部矿化度较低，西部则相对偏高.20年来，随城市化进程的加快，孔隙水水质的演变朝着正负两方面发展，盆地西山、草海一带生态环境有所好转，地下水矿化度在逐年降低，而地下水恶化的区间向着城市的外围边缘转移.冲湖积平原区，地下水矿化度变化不大.地下水化学类型的变异在很大程度上显示了地表土地利用方式的改变对地下水环境演变的影响.因子分析法的结果表明，地下水中Mg²⁺、HCO₃^-、Ca²⁺、Na⁺、Cl^-、SO₄^2-等离子的来源很大程度上显示自然演化的结果，而NO₃^-、K⁺、PO4^3-等离子的来源主要受农业和生活污水的影响.地下水化学组分中Mg²⁺、Na⁺、Cl^-、SO4^2-和K⁺同时受到自然作用和外界污染的影响，以COD为代表的工业污染在一定程度上影响了地下水中Cl^-、SO₄^2-和K⁺的浓度及其分布.

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-, SO42-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-, SO42-and K+ in groundwater.