Groundwater age dating

Major ions were determined by ion chromatography (LC-10AS, Shimazu) Methane gas was measured by a gas chromatography (GC-14B, Shimadzu) equipped with a flame ionization detector (FID) with a reproducibility of about ±2 %.

It showed that CFC-12 and CFC-113 were suitable tracers for groundwater dating because of their stability in the wetland environment.The CFCs in water samples were collected and purified by a purge and trap extraction system (Bullister and Weiss was used as purging and carrier gas.To avoid contamination and to reduce noise of system background, all devices were made without any plastics, and the valves were in purge housings flushed with carrier gas.Initially, whole water in the piezometer was withdrawn out to let fresh groundwater flow in.