Resumen
Studies have been carried out to investigate the baseline radioactivity level (gross alpha, gross beta and 226Ra) of soil, rocks and groundwater in the Fuling block, Chongqing, the largest shale gas exploitation area of China. The results show that there is a general activity concentration trend of gross alpha, gross beta and 226Ra: shale > soil > limestone due to the high content of uranium, thorium and potassium in shale and low content in limestone. The average activities of shallow groundwater from a limestone aquifer are 0.14, 0.13 and <0.008 Bq/L for gross alpha, gross beta and 226Ra, respectively. The radioactivity concentrations of gross alpha, gross beta and 226Ra (4.37, 1.40 and 0.395 Bq/L, respectively) of the formation water were far lower than those of formation water in the Marcellus shale in the USA (with ranges of 86?678, 23?77 and 16?500 Bq/L, respectively). One polluted shallow groundwater source and its associated stream sediments had been polluted due to leakage of drilling fluid with relatively high radioactivity levels and high concentration of main ions. Overall, this study provides an important baseline radioactivity level to assess the impact of shale gas exploitation on a shallow environment.