甘肃董志塬地区第四系地下水补给环境与水化学特征演化  

Groundwater recharge environment and geochemistry evolution of the Quaternary aquifer in the Dunzhiyuan region,Gansu Province

作　　者：潘峰[1,2] 张清寰[2] 何建华[2] 

机构地区：[1]兰州大学大气科学学院,甘肃兰州730000 [2]兰州大学西部环境教育部重点实验室,甘肃兰州730000

出　　处：《干旱区地理》2014年第1期9-18,共10页Arid Land Geography

基　　金：国家自然科学基金项目(41271039);长庆油田分公司科技项目(No.09AK-KF-003)资助

摘　　要：董志塬地区是我国重要的工业基地,近几十年来,地下水超采严重,引起了较为严重的供水安全问题,对塬区第四系地下水属性的认识十分必要。因此,通过综合利用水化学与同位素技术研究董志塬地区第四系地下水系统,对其补给来源、补给环境与演化规律进行探讨。稳定同位素资料显示地下水的δ2H、δ18O值较负,与现代降水及地表水特征值具有明显差别,指示了后两者对前者微弱的补给作用。该区降水在对第四系地下水补给时存在明显的滞后效应。地下水化学类型主要为HCO3-Ca型和HCO3-Ca-Mg型,矿化度较小,与当地主要河流的溶质成分差别较大,是很好的淡水资源。地下水经历的水岩反应有碳酸盐、硅酸盐和石膏矿物的溶解沉淀、阳离子交换和同离子效应等。The Dongzhiyuan region is a very particular area in China, which has the thickest loess deposition land- forms reaching up to approximately 300 m. The water resource in this area is very limited owing to the low precipita- tion and its especial hydrogeological condition. Recently, much attention has been focused on the groundwater sys- tem, however, little studies have been performed to this groundwater aquifer. In this study, the groundwater evolution and its recharge are examined using a combination of chemical indicators and stable isotopes. The groundwater types are studied by the Piper diagram. The water-rock reaction of groundwater is determined by the relationship between the different ions and the Phreeqc model. Finally, the possible recharge of the groundwater is confined by the stable isotopic data. The study shows that the groundwater is quite depleted with the stable isotope, the value of δ^18O is be- tween -9.2‰- and -13.16‰, which is lower than the value of the modem rainfall, indicating the groundwater may form in a cold environment in ancient time. In addition, the calculated ^14C age ranges from 3.17 to 24.32 ka, showing the groundwater is quite old. The groundwater type is HCO3-Ca and HCO3-Ca-Mg with a very low TDS of 270 mg/L, however, the salty of the rivers is very high with the value of 1 533 mg/L. The concentration of Na＋, K＋, Mg2＋, NO3- is below 1 mg/L. The mean value of m K/Na is 0.014, which is lower than that of the precipitation, indicating the loss of K absorbed by the plant, tuNa/C1 between 4.54 to 46.07 but shows decrease along the flow path, which illustrates the dissolution of Glauber＇s salt, however, the Na may exchange into the rock when the groundwater salinity increas-es. The plots of HCO3- ＋ SO42- vs Ca2＋＋Mg2＋ in groundwater lies below the 1 ： 1 stoichiometry line, there is a deficien- cy in （Ca2＋＋Mg2＋） relative to （ HCO3 ＋ S024- ） ,this must be balanced by Na＋ origins from the Glauber＇ s salt. The re- lationship between the Na＋-C1

关 键 词：董志塬 地下水 水化学 稳定同位素 

分 类 号：P641.3[天文地球—地质矿产勘探]