Application of radon tracer to evaluate the interaction characteristics between groundwater and surface water with time variance around the groundwater heat pump system

Abstract

The water exchange between groundwater and surface water has a significant impact on developing water resources. A geothermal energy system using indirect open loop ground source heat pump (GSHP) has been developed at Han River Environmental Research Center (HRERC) in Yangsu-ri, Yangpyeong-gun, Korea. For designing a high efficiency performance of the geothermal heat pump system in the study area, the characteristics of interaction between groundwater and surface water has to be figured out because the aquifer system of the study site is directly affected by Han Rivers. Therefore, radon-222 was used as an indicator because it has much higher concentration in groundwater than in surface water. In this study, 12 groundwater wells were used for monitoring radon concentration, hydrogeochemical parameters, and water level from May, 2014 to Apr., 2015. The statistical analysis and mixing analysis were also conducted for quantitative interpretation of the obtained radon and hydrogeochemical data. There are no significant correlations between the hydrogeochemical parameters and radon concentration. However, each group classified by the cluster analysis was reflected its own hydrogeochemical properties. The spatial distribution of radon concentration was affected by seasonal effect and fluctuation of Han River stage from surrounding dam activity. The results of mixing analysis represented the quantitative interpretation of radon data. This study demonstrated radon-222 can be used as an appropriate environmental tracer in examining the characteristics of interaction between groundwater and surface water in consideration of river discharge rate. These results help to provide useful background information on the development of GSHP in the riverside area.