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

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 NO 3-, SO 4 2-, Fe 2? and dissolved CH 4 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.

Distribution and Adsorption Characteristics of Phosphorus at A Headwater Wetland in Ichikawa City, Chiba Prefecture, Japan

“…It was also obvious that ORP of groundwater trended decrease in the upward groundwater at all investigated sites, indicating that ORP of groundwater was decreasing along the groundwater flow direction. Furthermore, The pH and EC of groundwater were also trended decrease along the flow direction at most investigated sites, which was the same as the characteristics of NO 3 -and SO 4 2-in groundwater of the wetland (Han et al, 2014). It could be concluded that the characteristics of pH, ORP and EC of the groundwater were mainly affected by processes of reduction in the wetland, which was the biochemical purification.…”

“…TDP concentrations of the spring water ranged from undetectable to 0.059 mg/L, and 2 samples (S7 and S16) exceeded the environmental standard (0.020 mg/L). Groundwater at different depth was observed in the middle of the wetland maintained under aerobic-, nitrate-, and sulfate-reducing conditions, and methanogenic conditions from 3 m to 1 m depth, respectively (Han et al, 2014). Wetlands are also used to treat municipal wastewater due to the reduction function (Yan et al, 2012).…”

Hydrogeochemistry and Precursory Anomalies in Thermal Springs of Fujian (Southeastern China) Associated with Earthquakes in the Taiwan Strait

“…Certain ion ratios (Na + /K + , Na + /Ca 2+ ) in geothermal water, and even the content of a certain single component (Si) can indicate its circulation depth. Through the ratio of rubidium and strontium isotopes, the ambient petrophysical composition in the cycle of the thermal spring can be determined, and also the thermal spring circulation time can be calculated [33,34].…”