Heavy Metal Assessments of Soil Samples from a High Natural Background Radiation Area, Indonesia

Mamuju, Indonesia, is an area with high natural background radiation. This study assesses heavy metal content in soil samples from this area to determine the level of public and environmental hazard it presents. This study analyzes natural radionuclide elements using high purity germanium (HPGe) gamma spectrometry and performs heavy metals analysis using a flame atomic absorption spectrometry (FAAS). Moreover, pollution indices and descriptive analyses were used to assess heavy metal contamination in the environment and the correlation between heavy metals and radionuclides. The results demonstrate that soil samples in several areas of Mamuju contain a high concentration of the natural radionuclides 226Ra and 232Th, and that heavy metal concentrations in the soil decrease in the sequence Zn > Pb > Cr > Cu > Ni > Cd. This study revealed that soil samples from Mamuju are moderately contaminated. There was a strong positive relationship between 226Ra, 232Th, ambient dose equivalent rate, and Pb. Ecological risk index (RI) and cumulative pollution index (IPI) values in Mamuju are 2.05 and 125, respectively, which are possible hazards to human health as a result. Pb concentration in the Mamuju soil samples ranged from 109 to 744 mg kg−1, exceeding the worldwide average of 27 mg kg−1.

Distributions and Risk Assessment of the Natural Radionuclides in the Soil of Shoubra El Kheima, South Nile Delta, Egypt

Due to heightening concern about radiation hazards protection, activity concentrations of 226Ra, 232Th, 40K in forty soil samples collected from Shoubra El Kheima in the South Nile Delta were measured using gamma-ray spectrometry. The mean activity concentrations of 226Ra and 40K were higher in 20% of the considered samples than the world average values. A comprehensive comparison with up-to-date data was carried out. Spatial distribution maps of the measured radionuclides and radiological parameters were generated. The distributions of natural radionuclides were influenced by the soil organic matter, clay content, and scavenger metals oxides, as well as differences in the physical and chemical attributes and solubility of these radionuclides. The results revealed that industrial activity and agricultural practices in the study area caused an incremental increase in 226Ra and 40K activity concentrations. It can be deduced that although there are intensive industrial activities in this area, the natural radiation that comes from the soil is normal and does not pose a significant radiological hazard to the public. The natural radioactivity of soil in this area needs to be monitored periodically to prevent unnecessary radiation exposure to inhabitants.

The <i>μ</i>Dose system: determination of environmental dose rates by combined alpha and beta counting – performance tests and practical experiences

The μDose system is a recently developed analytical instrument applying a combined α- and β-sensitive scintillation technique for determining the radioactivity arising from the decay chains of 235U, 238U and 232Th as well as from the decay of 40K. The device was designed to meet the particular requirements of trapped charge dating methods and allows the assessment of environmental (i.e. low) levels of natural radionuclides. The μDose system was developed as a piece of low-cost laboratory equipment, but a systematic test of its performance is still pending. For the first time, we present results from a comprehensive performance test based on an inter-laboratory comparison. We compare the results obtained with μDose measurements with those from thick source alpha counting (TSAC), inductively coupled plasma optical emission spectrometry (ICP-OES) and low-level high-resolution gamma spectrometry (HRGS) applied in five participating laboratories. In addition, the reproducibility and accuracy of μDose measurements were tested on certified reference materials distributed by the International Atomic Energy Agency (IAEA; RGU-1, RGTh-1 and RGK-1) and on two loess standards (Nussy and Volkegem) frequently used in trapped charge dating studies. We compare μDose-based results for a total of 47 sediment samples with results previously obtained for these materials by well-established methods of dose rate determination. The investigated natural samples cover a great variety of environments, including fluvial, aeolian, littoral, colluvial and (geo-)archaeological sites originating from high and low mountain regions as well as from lowlands in tropical areas, drylands and mid-latitude zones of Europe, Africa, Australia, Central Asia and the Americas. Our results suggest the μDose system's capability of assessing low-level radionuclide contents with very good accuracy and precision comparable to well-established dosimetry methods. Based on the results of our comparative study and with respect to the practical experiences gained so far, the μDose system appears to be a promising tool for trapped charge dating studies.

Ambient dose equivalent rate and soil contamination density with 137Cs in kitchen gardens in settlements of the Bryansk region, Russia in 2020–2021

The article provides results of application of the field (in situ) gamma spectrometry method for carrying out mass monitoring measurements of ambient dose equivalent rate and soil contamination density with 137Cs in kitchen garden plots located in the zone of radioactive contamination after the Chernobyl accident. In 2020 and 2021, 115 private farmsteads in 46 settlements of the Bryansk region were surveyed. At the time of the survey, the officially established average density of soil contamination with 137Cs in the settlements ranged from 27 to 533 kBq/m2 . The field spectra were measured using a portable scintillation gamma-spectrometer-dosimeter. Results of the field measurements and subsequent calculations of soil contamination density with 137Cs in the kitchen gardens were in good agreement with official data on the average soil contamination density with 137Cs in the surveyed settlements. The mean value of the ratio of the experimental data to the official data was 1.04. Individual values of experimental data deviated from corresponding official values by no more than two times. The use of the gamma spectrometry method in situ made it possible: 1) to determine separately values of the ambient dose equivalent rate from 137Cs and from natural radionuclides in the soil, and 2) to estimate the effective external doses to a person who worked in the kitchen gardens. The measured values of ambient dose equivalent rate varied from 17 to 53 nSv/h (mean ± standard deviation = 35 ± 9 nSv/h) for natural radionuclides and from 8 to 432 nSv/h (mean ± standard deviation = 125 ± 91 nSv/h) for 137Cs. The ambient dose equivalent rate from 137Cs normalized to the soil contamination density with 137Cs in the same kitchen garden was in the range of 0.41–0.84 (nSv/h)/(kBq/m2 ) with a mean value of 0.55 (nSv/h)/(kBq/m2 ). If a person stayed in kitchen garden for 840 hours per year, the estimated effective external doses from natural radionuclides and 137Cs were respectively in the range of 0.008–0.025 mSv/year and 0.004–0.20 mSv/year.

EXPERIMENTAL METHODS FOR STUDYING THE RESOURCE VALUE OF DUMP BLAST FURNACE SLAGS

The study of the properties of blast-furnace slags requires an integrated approach, including various research methods. The purpose of the work is to substantiate the resource value of the Zaporizhstal dump blast furnace slag. The research methods were used: X-ray phase, petrographic, gamma-spectrometric analysis and electron probe microanalysis. The slag is dispersed into fractions, since the slag minerals have different hardness. Fractions (mm) were investigated in the work: >20 2.5–5, <0.63. X-ray phase analysis made it possible to reveal in the crystalline part of blast-furnace slag minerals that are technically valuable in the production of binders: 3CaO∙2SiO2, SiO2, 2CaO∙Al2O3∙SiO2, α-2CaO∙SiO2, 2CaO∙MgO∙2SiO2, α-CaO∙SiO2. Minerals akermanite, bredigite, pseudo-wollastonite have hydraulic activity. It is shown that the mass fraction of the amorphous component is half the mass of the blast furnace slag. The high content of substances in the amorphous state confirms the possibility of sorption of extraneous ions and compounds. The found elements Potassium, Sodium, Sulfur, Chlorine, Cuprum and Titanium are not part of the minerals. Slag contains less than 1% of the total amount of Fe, Ti and Cu, belonging to the 3rd class of hazardous substances. The maximum content of Potassium, Sodium and Titanium is typical for the fraction 2.5–5 mm. The most basic is the fraction <0.63 mm (pH 9.7), for the 2.5–5 mm fraction pH 9.1, the most acidic fraction >20 (pH 8.2). By the value of the toxicity index (4.3–5.4) and the III hazard class, dump blast furnace slag «Zaporizhstal» as a moderately hazardous waste can be used as a secondary raw material in the construction industry. The database on the content of natural radionuclides in technogenic raw materials has been updated. It has been proven that slag and its individual fractions contain natural radionuclides 40К, 226Ra, 232Th. The main contribution to the value of Сef is made by the 226Ra radionuclide, then by 232Th. The excess of specific activity is expressed for the 2.5–5 mm fraction. The I class of radiation hazard is defined, which allows the use of slag in construction without restrictions. Dump blast furnace slag «Zaporizhstal can be recommended in the production of inorganic binders « by the totality of chemical indicators.