The extraction of unconventional gas resources such as shale and coal seam gas (CSG) is rapidly
expanding globally and often prevents the opportunity for comprehensive baseline groundwater investigations
prior to drilling. Unconventional gas extraction often targets geological layers with high
naturally occurring radioactive materials (NORM) and extraction practices may possibly mobilise radionuclides
into regional and local drinking water resources. Here, we establish baseline groundwater
radon and uranium levels in shallow aquifers overlying a potential CSG target formation in the Richmond
River Catchment, Australia. A total of 91 groundwater samples from six different geological units showed
highly variable radon activities (0.14e20.33 Bq/L) and uranium levels (0.001e2.77 mg/L) which were well
below the Australian DrinkingWater Guideline values (radon; 100 Bq/L and uranium; 17 mg/L). Therefore,
from a radon and uranium perspective, the regional groundwater does not pose health risks to consumers.
Uranium could not explain the distribution of radon in groundwater. Relatively high radon activities
(7.88 ± 0.83 Bq/L) in the fractured Lismore Basalt aquifer coincided with very low uranium
concentrations (0.04 ± 0.02 mg/L). In the Quaternary Sediments aquifers, a positive correlation between U
and HCO3
(r2 ¼ 0.49, p < 0.01) implied the uranium was present as uranyl-carbonate complexes. Since
NORM are often enriched in target geological formations containing unconventional gas, establishing
radon and uranium concentrations in overlying aquifers comprises an important component of baseline
groundwater investigations.