典型岩溶槽谷地下河水化学时空变化特征及影响因素初探——以重庆青木关地下河系统为例

对重庆青木关岩溶槽谷区内一条地下河的pH值、电导率、HCO3-、Ca2+、SO24-、Mg2+以及NO2-、NO3-等水化学指标进行了7个月至1年不等的监测,这些指标在空间和时间分布上具有不同特征.在空间上,电导率及HCO3-、Ca2+、Mg2+、NO3-浓度自地下河上游至下游逐步升高,比较地下河入口(D1)和出口(S2)处,电导率升高100μS/cm,HCO3-浓度升高1.5 mm0l/L,Ca2+浓度升高17 mg/L,Mg2+浓度升高5.1 mg/L,NO3-浓度相差6.4倍,而pH值和SO24-浓度则呈逐渐降低的趋势,D1和S2处的pH值相差0.16,SO24- 浓度相差26 mg/L.在时间分布上,pH、电导率、HCO3-、Ca2+、SO24-、Mg2+浓度季节变化明显,夏、秋季的值比冬、春季低.NO2-、NO3- 浓度变化在6、7月份有明显升高-回落的过程.对以上指标的影响因素分析显示:地质背景对水化学的控制、降雨的稀释效应、地下河的不同补给来源、岩溶作用的强弱程度以及农业活动的影响.

Abstract：

The hydrochemical indicators [pH, electrical conductivity (EC), HCO3- , Ca2+ , SO24- , Mg2+ ,NO2- and NO3-] of the underground water in a karst valley in Qingmuguan, Chongqing was monitored for 7-12 months, and the hydrochemical characters were found to be different in their temporal and spatial distribution. Some factors, such as EC, HCO3- , Ca2+ , Mg2+ and NO3- , increased from the upstream to the downstream, while pH and SO24 decreased. Compared with the data at D1 (the inlet), EC, HCO3-,Ca2+ and Mg2+ increased by 100μS/cm, 1.5 mmoll/L, 17 mg/L and 5.1 mg/L, respectively, at S2 (the outlet), and the concentration of NO3- at S2 was 6.4 times that at D1. In contrast, pH and SO24- concentration showed an opposite trend, being 0.16 and 26 mg/L lower at D1 than at S2. The underground water hydrochemistry differed in different seasons, pH, EC, HCO3- , Ca2+ and SO24- showed significant seasonal variations, being higher in winter and spring than in summer and fall. NO3- and NO2 showed a sharp in-crease followed by a decrease in June and July. It is concluded from an analysis of these monitoring data that the major influencing factors are geological background, precipitation dilution, different underground water recharge, karstification and agriculture activities.