用氟里昂(CFC)数据确定地下水的补给年龄

Groundwater Dating Using the Concentrations of Chlorofluorocarbons

地下水中是否有新水补给是地下水资源评价中非常重要的问题之一,如何确定地下水中有无新水补给是水文地质工作中的一个难题。地下水年龄测定是识别地下水来源的重要方法之一。近十多年来CFC方法被应用于近50年以来地下水的定年:即通过测定地下水中溶解的碳氯氟化合物(氟里昂)来确定地下水的补给年龄。本文重点介绍这一方法的原理和应用。

The concentrations of chlorofluorocarbons (CFCs) can be used for groundwater dating. Water exposed to CFCs in the atmosphere will build up an amount of CFCs that are proportional to the atmospheric CFCs concentrations. This type of water can be differentiated from older groundwater based on the CFCs' concentration. Two assumptions are important for the groundwater dating:the piston flow assumption and the binary mixture assumption. Under the piston flow assumption, the concentrations of CFCs of groundwater in solution equilibrium with that in the atmosphere can indicate the recharge time of the groundwater; and under the binary mixing flow assumption, the CFCs concentration ratios can indicate the recharge time of young groundwater and the fraction of the young groundwater in the mixture of young and old groundwater. This paper introduces the basic principle of groundwater dating using concentrations of CFCs.