Using 222Rn as a naturally occurring tracer to estimate NAPL contamination in an aquifer

• This paper used 222Rn as a tracer for estimating a NAPL-contaminated groundwater site.
• 222Rn partition coefficient in water and some NAPLs was examined by batch experiment.
• The partition coefficient of gasoline, diesel, PCE, TCE was acquired from the regression results.
• Rn shows a strong affinity to NAPLs, so semi-quantitative results should be possible.
• TCE contaminated 54 groundwater samples in Wonju city, Republic of Korea, was analyzed using 222Rn tracer.

The naturally occurring radioisotope 222Rn was used as a partitioning tracer to evaluate the presence and amount of a non-aqueous phase liquid (NAPL) in an aquifer. The batch experiment results of a diesel contaminated soil showed that the emanation rate of 222Rn decreased to 31%, relative to a background rate. Batch experiment results of water contaminated by gasoline, diesel, PCE and TCE were similar. A field study to examine TCE contamination was conducted using 54 groundwater samples in Wonju city, Republic of Korea. Estimates of TCE contamination ranged from <0.001 mg/L to 14.3 mg/L, and 222Rn concentrations ranged from 1.89 Bq/L to 444. Results of 222Rn analysis showed that TCE contamination was mainly restricted to an asphalt laboratory area and that the 222Rn values of a NAPL-contaminated aquifer were correlated with TCE analytical results.