Influence of Noble Gas Phase Partitioning on the 3H-3He Groundwater Age at a DNAPL Contaminated Site

DNAPL contaminated sites require an understanding of the hydrological properties for future remedial actions to proceed. The 3H-3He age dating method is one of the ways to characterize the groundwater flow properties. However, there is a chance of misinterpretation of groundwater age using the conventional 3H-3He age calculation method at DNAPL contaminated sites. This is due to the fact that the existence of noble gas phase partitioning to the liquid DNAPL phase is not considered in the conventional method. Hence, the aim of this research is to evaluate the difference in the 3H-3He age calculation between the cases where noble gas phase partitioning was considered and not. Groundwater samples were obtained from the DNAPL contaminated site at the Namdong Industrial Complex (NIC), South Korea. Noble gas data of groundwater samples showed varying degrees of phase partitioning. The neglection of this aspect likely underestimates the groundwater age to varying extents depending on the phase partitioning of samples, which is critical in terms of the accuracy of groundwater age calculation and overall comprehension of the flow system. Hence, it can be interpreted that noble gas phase partitioning is a potential factor to be encountered for a better understanding of the groundwater flow using the 3H-3He age tracer within a DNAPL contaminated site.

Acknowledgement: This work was supported by Korea Environment Industry & Technology Institute(KEITI) through "Activation of remediation technologies by application of multiple tracing techniques for remediation of groundwater in fractured rocks" funded by Korea Ministry of Environment (MOE)(Grant number:20210024800002/1485017890).