Radioactivity of beach sand in the south western coast of Sri Lanka

Review and statistical analysis of activity values reported for coastal sands worldwide

The activity of natural radionuclides is unevenly distributed across the Earth's crust, with certain areas exhibiting significantly higher levels than others, known as High Background Radiation Areas (HBRAs). This study presents a statistical analysis of reported activity values for coastal sands globally. Through this statistical analysis, costal sands were classified into four categories based on their activity levels, providing a standardized framework to compare the natural radioactivity of these sands. This classification is a valuable tool for identifying populations exposed to different radiation levels, which is essential for the study of stochastic effects. The study proposes thresholds to define HBRAs as regions with activity values exceeding 203 Bq/kg for 238U, 517 Bq/kg for 232Th, or 960 Bq/kg for 40K. Regions with lower values are classified as NonHBRAs. Further subdivision of these categories resulted in four distinct regions: NonHBRA-, NonHBRA+, HBRA-, and HBRA+. The activity values for these subdivisions are 92 Bq/kg and 2,903 Bq/kg for 238U, 94 Bq/kg and 7,230 Bq/kg for 232Th, and 901 Bq/kg and 2,298 Bq/kg for 40K. By calculating the external dose rates from the reported activity data, a threshold of 357 nGy/h was identified as the dose boundary separating NonHBRAs from HBRAs. The values for the subdivisions resulted 101 nGy/h and 3,867 nGy/h. The study also explores the content of these natural radionuclides in relation to their bearing minerals and discusses correlations between the reported activity values and the characteristics of the sands. Additionally, the activity of the anthropogenic radionuclide 137Cs (reported values ranging from the detection limit to 63 Bq/kg) is examined.

Assessment of radioactivity in sand samples from eastern Nepal in perspective of radiological hazards

This study was conducted to investigate the activity concentrations of 226Ra, 232Th and 40K in the sand samples and the health hazards associated with them utilizing a NaI (Tl) gamma spectrometer. The average activity concentrations of 226Ra, 232Th and 40K were found to be 24.8 ± 10.1, 39.8 ± 16.4 and 531.3 ± 52.8 Bq kg-1, respectively. The calculated radiological hazard parameters, including radium equivalent activity, absorbed gamma dose and effective dose rate, were found to be 122.7 ± 34.0 Bq kg-1, 57.7 ± 14.9 nGy h-1 and 0.3 ± 0.1 mSv y-1, respectively. Notably, these results were observed to be below the recommended thresholds. Other measured hazard indices were also lower than the prescribed values. From a radiological perspective, the present study concludes that the sand samples do not pose any threat to human health when utilized as a building material.

ICP-MS Measurement of Trace and Rare Earth Elements in Beach Placer-Deposit Soils of Odisha, East Coast of India, to Estimate Natural Enhancement of Elements in the Environment

Inductively coupled plasma mass spectrometry (ICP-MS) has been used to measure the concentration of trace and rare earth elements (REEs) in soils. Geochemical certified reference materials such as JLk-1, JB-1, and JB-3 were used for the validation of the analytical method. The measured values were in good agreement with the certified values for all the elements and were within 10% analytical error. Beach placer deposits of soils mainly from Odisha, on the east coast of India, have been selected to study selected trace and rare earth elements (REEs), to estimate enrichment factor (EF) and geoaccumulation index (I_geo) in the natural environment. Enrichment factor (EF) and geoaccumulation index (I_geo) results showed that Cr, Mn, Fe, Co, Zn, Y, Zr, Cd and U were significantly enriched, and Th was extremely enriched. The total content of REEs (ƩREEs) ranged from 101.3 to 12,911.3 µg g⁻¹, with an average 2431.1 µg g⁻¹ which was higher than the average crustal value of ΣREEs. A high concentration of Th and light REEs were strongly correlated, which confirmed soil enrichment with monazite minerals. High ratios of light REEs (LREEs)/heavy REEs (HREEs) with a strong negative Eu anomaly revealed a felsic origin. The comparison of the chondrite normalized REE patterns of soil with hinterland rocks such as granite, charnockite, khondalite and migmatite suggested that enhancement of trace and REEs are of natural origin.

BACKGROUND RADIATION LEVELS NEAR A MINERAL SAND MINING FACTORY IN SRI LANKA: CORRELATION OF RADIATION MEASUREMENTS WITH MICRONUCLEI FREQUENCY

Lanka Mineral Sands Ltd (LMS) is a company operating in Pulmoddai, Sri Lanka, mining for rare earth minerals along with monazite which contains thorium that emits ionizing gamma and alpha radiation on decay. The objective of the study was to determine the background radiation levels and selected radionuclides and then to correlate these levels with the frequency of micronuclei (MN) among persons residing in the vicinity of LMS. A cross-sectional study was conducted among persons of both sexes between 35 and 45 years of age residing in the vicinity of LMS. Background radiation measurements were obtained by a survey metre, and gamma spectrometry was done on soil samples. Five millilitres of venous blood was drawn for cytokinesis-blocked MN assay. Background radiation levels measured by the survey metre; 232Th, 226Ra and 210Pb mass activities in soil were highest in the samples collected from the LMS. The background radiation measurements positively correlated with MN frequency although the magnitude of the correlation was small (r = 0.176, p = 0.04). This implies that chronic long-term exposure to low-dose radiation may result in genotoxicity. Prospective large-scale studies are recommended to evaluate the long-term effect of exposure to low-dose radiation at Pulmoddai.

Annual committed effective dosage from natural radionuclides by ingestion of local food growing in mineral mining area, Sri Lanka

Sri Lanka's largest mineral sand deposit occurs in Pulmoddai, and the surrounding area of the mineral sand deposit has been identified as a high natural background radiation area. The food crops grown in the area are used for human consumption. However, the long-term consumption of high radioactive foodstuff may cause health defects. The objective of the present study was to assess the radiological impact on individuals due to ingestion of foodstuffs grown in Pulmoddai area. Seasonal food crops growing in the area, including cereals, vegetables, nuts, fruits and yams were collected and used to prepare common meal plans consumed by the residents. Samples were analyzed with high-purity germanium gamma spectrometer for activity concentrations. Activity concentration of ⁴⁰K was observed in higher amounts in every food sample. Trace amounts of ¹³⁷Cs ²³²Th and ⁷Be were also identified. The total committed effective dosage to an adult from gamma-emitting radionuclides from cooked meals was 0.1482 mSv year^-1, and raw foodstuff was 0.0667 mSv year^-1, which are far below than the harmful levels declared by International Atomic Energy Agency. Results concluded that foodstuff and cooked meals consumed by the people who live in Pulmoddai, Sri Lanka, are radiologically safe.

Assessment of natural radioactivity and gamma-ray dose in monazite rich black Sand Beach of Penang Island, Malaysia

Activity concentrations of primordial radionuclides in sand samples collected from the coastal beaches surrounding Penang Island have been measured using conventional γ-ray spectrometry, while in-situ γ-ray doses have been measured through use of a portable radiation survey meter. The mean activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K at different locations were found to be less than the world average values, while the Miami Bay values for ²²⁶Ra and ²³²Th were found to be greater, at 1023±47 and 2086±96Bqkg^{̶ 1} respectively. The main contributor to radionuclide enrichment in Miami Bay is the presence of monazite-rich black sands. The measured data were compared against literature values and also recommended limits set by the relevant international bodies. With the exception of Miami Bay, considered an elevated background radiation area that would benefit from regular monitoring, Penang island beach sands typically pose no significant radiological risk to the local populace and tourists visiting the leisure beaches.

Determination of activity concentration of natural and artificial radionuclides in sand samples from mediterranean coast of Antalya in Turkey

In this paper, we attempt to determine the activity concentration of natural and artificial radionuclides in 37 sand samples from the Mediterranean coast of Antalya in Turkey by using a high purity Germanium (HpGe) detector. 238U, 232Th, 40K and 137Cs activity concentrations, absorbed dose rate, annual effective dose equivalent, radium equivalent activity, external and internal hazard index of sand samples are determined res-pectively. The average values are 13.43 ± 0.21 Bq/kg, 6.96 ± 0.06 Bq/kg and, 122.46 ± 18.58 Bq/kg, for 238U, 232Th and 40K respectively. Most of the activity concentration values are less than below minimum detection limit for 137Cs. The average values of the absorbed dose rate D (nGy/h), annual effective dose equivalent AEDE(μSv/y), radium equivalent activity Raeq (Bq/kg), external hazard index Hex and internal hazard index Hin are 15.52 nGy/h, 19.03 μSv/y, 32.81 Bq/kg, 0.09 and 0.12 respectively. It is observed that 238U, 232Th, 40K and 137Cs activity concentrations, absorbed dose rate, annual effective dose equivalent, radium equivalent activity are in the limit of the published values, external and internal hazard index values are less than unity.