Application of chlorofluorocarbons (CFCs) to estimate the groundwater age at a headwater wetland in Ichikawa City, Chiba Prefecture, Japan

Zhiwei Han,Touma Matsumaru,Xing Li,Changyuan Tang,Yingjie Cao,Chipeng Zhang,Jingqiu Piao

doi:10.1007/s13201-013-0145-7

Abstract

To delineate the groundwater flow system in a basin, the groundwater age was estimated by analyzing chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) in a typical headwater wetland in Ichikawa, Japan. Feasibility of groundwater dating by CFCs was assessed comprehensively based on the concentrations of NO3−, SO42−, Fe2+ and dissolved CH4 in the groundwater, because the CFCs would be degraded under the reduction condition available in a wetland. It was found that the CFC-11 apparent age was much older than that estimated by other CFC species. It showed that CFC-12 and CFC-113 were suitable tracers for groundwater dating because of their stability in the wetland environment. Furthermore, the mixture of groundwater with different age was discussed by CFC-12 and CFC-113 based on the binary mixing model and piston-flow model. As a result, the apparent age of groundwater in the study area is in the range of 38–48 years.

Highlights

As one of the most active factors, groundwater age is a key to understand the hydrological cycle as well as the associated hydro-ecological processes in a watershed
To delineate the groundwater flow system in a basin, the groundwater age was estimated by analyzing chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) in a typical headwater wetland in Ichikawa, Japan
Feasibility of groundwater dating by CFCs was assessed comprehensively based on the concentrations of NO3, SO42, Fe2? and dissolved CH4 in the groundwater, because the CFCs would be degraded under the reduction condition available in a wetland

Summary

Introduction

As one of the most active factors, groundwater age is a key to understand the hydrological cycle as well as the associated hydro-ecological processes in a watershed. Tritium (3H) is used to estimate residence times, but the method is difficult to use since the tritium concentration is too low to be detectable at present (DeWalle et al 1997; Małoszewski and Zuber 1982; Uhlenbrook 2002). Historical tracers are those which are present as a result of human activity, and the concentrations of tracers changed in the past time obey a given rules (Selaolo 1998). Compared with some groundwater dating techniques, CFCs can be determined

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Results