Biljana Milenkovic

Heavy metals, organics and radioactivity in soil of western Serbia

Western Serbia is a region well-known for potato production. Concentrations of selected metals, polycyclic aromatic hydrocarbons (PAHs) and radioactivity were measured in the soil in order to evaluate the quality and characteristics. The examined soils (Luvisol and Pseudogley) showed unsuitable agrochemical characteristics (acid reaction, low content of organic matter and potassium). Some samples contained Ni, Mn and Cr above the maximal permissible concentration (MPC). The average concentration of total PAHs was 1.92 mg/kg, which is larger than the maximal permissible concentration in Serbia but below the threshold values in the European Union for food production. The average radioactivity of (238)U, (226)Ra, (232)Th, (40)K and the fission product (137)Cs were 60.4+/-26.2, 33.2+/-13.4, 49.1+/-18.5, 379+/-108 and 36.4+/-23.3 Bq/kg. Enhanced radioactivity in the soils was found. The total absorbed dose rate in air above the soil at 1m height calculated for western Serbia was 73.4 nGy/h and the annual effective dose was 90 microSv, which are similar to earlier reports for the study region.

Exposure of school children to polycyclic aromatic hydrocarbons, heavy metals and radionuclides in the urban soil of Kragujevac city, Central Serbia

The concentrations of radionuclides, polycyclic aromatic hydrocarbons (PAHs) and heavy metals were measured in soil samples collected from school backyards and playgrounds in Kragujevac, one of the largest cities of Central Serbia. The activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs were determined using the HPGe semiconductor detector. The average values were 34.6, 44.7, 428.9 and 45.1 Bq kg(-1), respectively. The correlation between the activity concentrations of (226)Ra in the soil samples and the results of the previous measurement of (222)Rn concentrations in the indoor air was examined. The absorbed dose rates, the annual effective doses and excess lifetime cancer risk were also estimated. The activity concentrations of (226)Ra and (232)Th have shown normal distribution. The collected soil samples were analysed for PAHs by HPLC. All analysed soil samples contained PAHs, and their total amounts (for 15 measured compounds) were found to be between 0.038 and 3.136 mg kg(-1) of absolutely dry soil (a.d.s). In addition the concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in the fourteen soil samples collected from the playgrounds of kindergartens.

Persistent organic pollutants, heavy metals and radioactivity in the urban soil of Priština City, Kosovo and Metohija

Polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), heavy metals content and radioactivity levels were measured in 27 soil samples collected from Priština, the capital of Kosovo and Metohija. The sixteen PAHs, twelve OCPs and six PCBs congeners were determined by gas chromatography system with mass spectrometry detection. Although the use of PCBs and OCPs was prohibited decades ago residues of those compounds still existed in measurable concentrations in soils of Priština. PAHs were also present in analyzed samples but their mean concentration was significantly lower than mean concentrations of PAHs previously reported in urban areas in the world. The concentrations of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) were determined by the EDTA extraction protocols, along with their extractable concentrations. The activity concentrations of natural radionuclides (226Ra, 232Th and 40K) were determined by gamma spectrometry method. The Shapiro-Wilk normality test found that activity concentrations of natural radionuclides were normally distributed. Radiological risk was estimated through the annual effective dose, gonadal dose equivalent, excess lifetime cancer risk, radium equivalent activity, external and internal hazard indexes. Spearman correlation coefficient was used for analysis of correlations between physicochemical properties, heavy metal contents and radionuclide activity concentrations. Strong positive correlation between 226Ra and 232Th was found, as well as among pairs of As-Cd and Co-Mn. Very strong positive correlation (0.838) at the 0.01 significance level was noted for Pb-Zn pair. Strong correlations indicate common occurrence of these elements in the nature, as well as geogenic association.

Computer program Neutron_CR-39 for simulation of neutrons from an Am–Be source and calculation of proton track profiles

Abstract A computer program called Neutron_CR-39.F90 for neutron simulation through a PADC detector and its detection was described and developed. In this work the neutron Am–Be source was considered for simulation. It was shown that the most intensive secondary particles, created in neutron interactions with the detector, are protons. The programming steps are outlined with detailed description of neutron simulation, determination of latent tracks of created protons, as well as, their development after detector etching in the same and opposite direction of particle motion. The outputs of the code are parameters of created protons (coordinates of starting and stopping points, direction angles of particles, initial and deposited energies) and number of visible tracks per incident neutron. Program summary Program title: Neutron_CR-39 Catalogue identifier: AEIU_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEIU_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 140 004 No. of bytes in distributed program, including test data, etc.: 2 213 012 Distribution format: tar.gz Programming language: Fortran 90 Computer: PCs and workstations Operating system: Unix, Linux, Windows 95+ RAM: 256 MB Classification: 17.5, 18 External routines: For the Windows installation the entire code must be linked with the PORTLIB library. Nature of problem: The neutrons do not cause ionizations in the detector, and consequently no tracks are produced directly by them in the PADC. Due to the elastic and nonelastic interaction of neutrons with the atoms of PADC, recoil nuclei and secondary particles are created producing latent intrinsic tracks. After chemical etching in aqueous NaOH solution these tracks become visible under optical microscope and usually density of visible tracks is measured. Optical microscopes are often used for this purpose but the process is relatively tedious and time consuming. The present computer program has been written for neutron simulation through PADC detector; determination of parameters of secondary particles; calculation track profiles of secondary particles emitted in the same and opposite direction as etchant progression. The outputs of the code are parameters of secondary particles (coordinates of starting and stopping points, direction angles of particles, initial and deposited energies) and number of visible tracks per incident neutron. Solution method: A computer program is prepared to simulate neutronʼs interactions in a PADC by the Monte Carlo method using the Neutron data library ENDF/B-VII [B. Milenkovic, D. Nikezic, N. Stevanovic, Radiat. Meas. 45 (2010) 1338]. The parameters of the emitted secondary particles (emission angle, initial energy, deposited energy and starting and stopping coordinates) were stored in an enclosed file. The subroutine for calculation of track profiles by a finite difference method for particles emitted in the same direction was developed [D. Nikezic, N. Stevanovic, D. Kostic, S. Savovic, K.C.C. Tse, K.N. Yu, Radiat. Meas. 43 (2008) S76]. It was shown that there are many tracks formed in the opposite direction than the etchant progression. The method for calculation of track profiles for these particles is developed in [B. Milenkovic, N. Stevanovic, D. Krstic, D. Nikezic, Radiat. Meas. 44 (2009) 57]. It is very different than the method for track in the same direction. The separate subroutine for this purpose was developed here. Additional comments: The program distribution file contains an executable which enables the program to be run on a Windows machine. The source code is also provided, but in order to build an executable the PORTLIB must be available. Running time: Running time depends mainly on the neutron number for simulation, source and detector geometry and removed layer required by the user. Running time is several minutes.

Monte Carlo calculations of lung dose in ORNL phantom for boron neutron capture therapy

Monte Carlo simulations were performed to evaluate dose for possible treatment of cancers by boron neutron capture therapy (BNCT). The computational model of male Oak Ridge National Laboratory (ORNL) phantom was used to simulate tumours in the lung. Calculations have been performed by means of the MCNP5/X code. In this simulation, two opposite neutron beams were considered, in order to obtain uniform neutron flux distribution inside the lung. The obtained results indicate that the lung cancer could be treated by BNCT under the assumptions of calculations.

NEUTRON DETECTION BY A CR-39 DETECTOR AND ANALYSIS OF PROTON TRACKS ETCHED IN THE SAME AND OPPOSITE DIRECTIONS

A program code to simulate neutron interactions with a CR-39 detector and calculate parameters describing the induced etched proton tracks in the CR-39 material was previously developed(( 1)). This code was used to understand the mechanisms involved during interactions with neutrons in the CR-39 material and the influence of the etching process, enabling an improvement in the efficiency of the CR-39 detector. Due to neutron interaction with atoms of the detector material, the created protons are emitted in different directions and their latent tracks are oriented randomly within the detector. The aim of this paper is to show differences between the number of visible tracks etched in the same and opposite directions from both sides of the detector. The efficiency of neutron detection was analysed as a function of the removed layer and neutron energy for both sides of detector.

Environmental radioactivity with respect to geology of some Serbian spas

This study was performed in order to investigate gamma dose rates, radon exhalation rates and soil radioactivity with respect to geology. Fifteen locations in three Serbian spas were under investigation. Gamma dose rate was measured by Radex RD1503+ monitor. GIS technology was applied for the interpretation of the results. HPGe detector was used for gamma-spectrometry determination of soil radioactivity. Radon exhalation rate was determined using RAD7 device. The correlation was examined between radon exhalation rate and 226Ra. No correlation was found between calculated effective dose from radionuclides in soil and measured ambient gamma dose rate.

Determination of a CR-39 detector response to neutrons from an Am-Be source.

A comparison of experimental and calculated responses of a CR-39 detector to neutron spectra from an Am-Be source is presented. Code named Neutron_CR-39.F90 has been used to calculate the neutron dose equivalent as well as the track density. Conversion coefficient (sensitivity), between track density in track/cm(2) and neutron dose equivalent in mSv, was calculated and good agreement with experimental data was found. Sensitivity increases linearly with removed layer in the range between 6 μm and 24 μm.