In this research, the radioactive noble gas radon was used as a tracer for Non-Aqueous Phase Liquids (NAPLs) contamination, since it is much more soluble in these substances than in air or water. Soil radon remains trapped within the NAPLs, resulting in a local reduction in the radon concentration within close proximity to the contaminated area. This technique was applied to a contaminated site in Roma (Italy). The main residual NAPLs are total hydrocarbons and methyl-tertiary-butyl ether (MTBE), a water-soluble additive. The monitoring activities included four sampling campaigns of groundwater from 18 wells from February 2020 to February 2021. Concentration maps were produced using radon data. The results show that the radon deficit traces the location of NAPLs in the fuelling station very well, with a residual source zone extending in NNW-SSE direction. A good correspondence between a low amount of radon and a higher concentration of NAPLs was found. The peaks of Volatile Organic Compounds (VOCs) detected between 8–9 and 11–12 m depths indicate the presence of residual blobs of NAPLs in the vadose zone of the aquifer.
Mattia, M., Tuccimei, P., Soligo, M., Carusi, C., Portaro, M. (2021). Tracing NAPL Contamination of Groundwater Using Natural Radon: A Case-Study in Roma (Central Italy). In Water: Ecology and Management. Hyderabad : Dr. Tewodros Tena.