Contribution to the Implementation of Ambient Gamma Radiation Mapping Using the PGIS-2 Detector in Abidjan, Côte d’Ivoire

Abstract

Background: Environmental radioactivity monitoring is important for assessing ambient gamma-radiation exposure and establishing local radiological baseline information. In Côte d’Ivoire, ambient gamma radiation has previously been measured using other techniques; however, the use of the PGIS-2 detector combined with Surfer-based spatial mapping has not been reported. This study therefore explores this approach for generating spatially resolved ambient gamma-radiation information in Abidjan. Aims: This work contributes to the implementation of ambient gamma radiation mapping through familiarization with the PGIS-2 detector and Surfer software, with a view to using them to map this radiation in Côte d’Ivoire. Place and Duration of Study: The study was conducted at “University Felix Houphouët Boigny” in Abidjan over a period of one week. Methodology: The PGIS-2 detector was carried in a backpack worn by the experimenter. The latter moved across the study site at a pace of one step per second, that is, at a speed of less than 4 km/h, while the detector recorded the dose rate at one-second intervals, as well as the geographic coordinates (latitude and longitude) of each measurement point. Five-minute measurements in a fixed position, with the detector placed 1 m above the ground, were carried out at three different locations. The data obtained served as normalization values for the other measurements performed more than one meter above the ground. Mapping of ambient gamma radiation was carried out using Surfer software to analyze the PGIS-2 data. Results: The ambient gamma effective dose rates obtained ranged from (16 ± 4) nSv/h to (244 ± 16) nSv/h, with an average of (50 ± 7) nSv/h. The corresponding annual effective dose based on this average was (0.09 ± 0.01) mSv. From these data, a histogram was plotted and an isodose map was produced. Conclusion: The average ambient gamma effective dose rate obtained at the measurement site was slightly above the global average ambient gamma radiation dose in outdoor air provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). However, the corresponding annual effective dose was well below the global ambient gamma radiation dose limit for the public recommended by the International Commission on Radiological Protection (ICRP). The plotted histogram showed two sets of minimum and maximum dose values corresponding to the light and dark areas on the isodose map.