Radiological assessment of Samanalawewa quarry site: an initiative for site specific rehabilitation approaches

Abstract

Abandoned quarry sites require suitable rehabilitation approaches based on comprehensive assessments. Site characterization based on slope stability, rock properties, weathering, geological and hydrological information are common for such purposes. This study attempts to integrate in-situ and ex-situ radioactivity measurements for site characterization, through gamma ray spectrometry analysis of representative soil and rock samples collected from the site. The mean values of activity concentrations of K-40, U-238, and Th-232 in rock samples were 694.38 Bq/kg, 38.70 Bq/kg, and 60.63 Bq/kg respectively. In soil samples, the mean values of activity concentrations were 637.04 Bq/kg for K-40, 23.73 Bq/kg for U-238, and 90.52 Bq/kg for Th-232. All these values except U-238 in soil exceed global average concentrations for soil radiation, indicating significant radiological signatures. These results were correlated with the field observations and records at the Samanalawewa abandoned quarry site which included rock properties including color, weathering, and rock types. Accordingly, higher radioactivity records on less weathered, light-colored rocks like feldspathic gneiss, while relatively lower levels were found in highly weathered, dark-colored rocks like biotite gneiss. The findings highlight the importance of assessing radioactivity alongside rock property characteristics to develop effective and safe rehabilitation strategies for abandoned quarries.