Radon Concentration and its Indices in Bulak (Mencilis) Cave

Abstract

The Bulak cave is in the village of Bulak near Safranbolu city. It’s one of the longest caves in Türkiye, which goes 6 kilometers into the inside, but approximately 400 meters are accessible to visitors. You require a professional guide and special equipment to travel further into the cave with lakes, a waterfall, and rivers which are essential for cavers, tourists, and researchers. However, there are possible several health problems for cave visitors. This study mainly aims to measure the radon concentrations with the nuclear track CR-39 detector in the cave environment. Twenty-two detectors were distributed inside the tourist’s area, and another six detectors were in the cave’s deeper region. The exposure time was one month on 24 September 2020, in addition to two soil samples collected from the cave used for medical purposes. These detectors are collected after 30 days and then etched with a chemical solution. The radon concentrations were calculated, which ranged between 16.437 (Bq/m3) and 48.652 (Bq/m3) using an optical microscope from the track density in detectors. The minimum and maximum values of radiation indices AED (mSv/y), LCR (WLM), PAEC (mWL), Dsoft (nGy/h), Dlung (nGy/h) and Heff (nSv/h) are presented, and all results for the radon and radiation indices are within the global limit. Radon concentrations for two soil samples were 26.956 (Bq/m3) and 59.172 (Bq/m3), and all the results were within the acceptable limits recommended by ICRP and UNSCEAR. The XRF examination was performed, which indicated the presence of Fe, Cu, Zn, As, and Mn minerals with high concentrations of 101607, 552, 1337, 237, and 1601 ppm, respectively, which are all more than the world permissible limits. The XRD analyses for the soil sample indicated the presence of clay and non-clay minerals such as Feldspar, Quartz, Gypsum, Calcite, Palygorskite, Kaolinite, and Montmorillonite.