Radiological and heavy metals analysis in soil and water at the former tin mining site in the urban area (Danau Kota Lake, Kuala Lumpur)

Abstract

Former mining sites are known to be concentrated with enriched naturally occurring radioactive materials (NORM) and heavy metals, as a result of past mining activities. A number of the sites are reclaimed as an open area, which in turn raised concerns regarding public safety. Thus, it is crucial to evaluate the safety of the public engaging in activities around the former tin mining areas. A study is carried out to determine the concentrations of NORM and heavy metals in soil and water collected from Danau Kota Lake, Kuala Lumpur, known as a former mining site. Both NORM and heavy metals were analysed using gamma spectrometry and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The average concentration of 226Ra and 232Th in water collected was 0.7 ± 0.2 Bq/L and 0.1 ± 0.03 Bq/L, respectively. 40K, however, was not detected in the water. The average activity concentration of 226Ra, 232Th, and 40K in soil was 60.8 ± 2.3 Bq/kg, 42.9 ± 1.4 Bq/kg, and 338.4 ± 11.7 Bq/kg, respectively. From the values obtained, it is observed that the activity concentrations for both soil and water are still within the range limit reported by WHO and UNSCEAR. In regards to heavy metals analysis, manganese concentration was the highest in both water and soil with a value of 1.18 µg/L and 147.7 mg/kg, respectively. To evaluate the radiological hazard, the radium equivalent activity index (Req), gamma index (Iγ), absorbed dose rate (D), effective dose rate (Deff) and external hazard index (Hex) are calculated and valued at 148 Bq/kg, 1.1 Bq/kg, 69 nGy/h, 0.1 mSv/year and 0.4, respectively. All radiological hazard indices are found to be below the safety limits. Therefore, the lake area is considered safe for public activities except for Iγ.