Sema Erenturk

Natural radioactivity of riverbank sediments of the Maritza and Tundja Rivers in Turkey

This article represents the first results of the natural radionuclides in the Maritza and Tundja river sediments, in the vicinity of Edirne city, Turkey. The aim of the article is to describe the natural radioactivity concentrations as a baseline for further studies and to obtain the distribution patterns of radioactivity in trans-boundary river sediments of the Maritza and Tundja, which are shared by Turkey, Bulgaria and Greece. Sediment samples were collected during the period of August 2007–April 2010. The riverbank sediment samples were analyzed firstly for their pH, organic matter content and soil texture. The gross alpha/beta and 238U, 232Th and 40K activity concentrations were then investigated in the collected sediment samples. The mean and standard error of mean values of gross alpha and gross beta activity concentrations were found as 91 ± 11, 410 ± 69 Bq/kg and 86 ± 11, 583 ± 109 Bq/kg for the Maritza and Tundja river sediments, respectively. Moreover, the mean and standard error of mean values of 238U, 232Th and 40K activity concentrations were determined as 219 ± 68, 128 ± 55, 298 ± 13 and as 186 ± 98, 121 ± 68, 222 ± 30 Bq/kg for the Maritza and Tundja River, respectively. Absorbed dose rates (D) and annual effective dose equivalent s have been calculated for each sampling point. The average value of adsorbed dose rate and effective dose equivalent were found as 191 and 169 nGy/h; 2 and 2 mSv/y for the Maritza and the Tundja river sediments, respectively.

Determining distribution of heavy metal pollution in terms of ecological risk levels in soil of industrially intensive areas around Istanbul

The aims of the present study were to measure the concentrations of As, Cr, Co, Fe, and Zn in soils from two heavily industrialized areas and to assess the degree of heavy metal pollution by using the indices enrichment factor and the geo-accumulation index, as well as assessing the potential ecological risk. The concentrations of the selected elements in the environmental samples were determined by the neutron activation analysis. The pollutant concentrations in the studied areas showed that the soils were characterized by a high pollution from As and Cr due to the industrial facilities in the area. The concentrations in the Tuzla industrial area were 79–1215 mg/kg of Cr, 17–84 mg/kg of As, 22,000–54,000 mg/kg of Fe, 101–258 mg/kg of Zn, and 8–23 mg/kg of Co. The results for the Cerkezkoy industrial area were found to be 46–196 mg/kg of Cr, 6–24 mg/kg of As, 17,000–25,000 mg/kg of Fe, 67–136 mg/kg of Zn, and 7–10 mg/kg of Co. The contamination in the soils from heavy metals was assessed based on enrichment factor, geo-accumulation factors, and ecological risk indices. The results were compared with the data from other industrial areas in Turkey. It was found that the metals As and Cr showed higher concentrations in Tuzla than in other examined industrial areas. The results for Cerkezkoy industrial area indicate that the area is not as contaminated as the other industrial areas in Turkey.

Sorption of Th(IV) onto ZnO nanoparticles and diatomite-supported ZnO nanocomposite: kinetics, mechanism and activation parameters

Abstract In this study, for the first time ZnO nanoparticles and diatomite-supported ZnO nanocomposite have been utilized as adsorbent for the removal of Th(IV) ions from aqueous solutions under different experimental conditions. The Langmuir, Freundlich, Temkin and Dubinin– Radushkevich (D–R) isotherms were used to analyze the equilibrium data. The sorption equilibrium data were fitted well to the Langmuir isotherm with maximum sorption capacities values was found to be 1.105 mmol/g and 0.320 mmol/g for ZnO nanoparticles and diatomite supported ZnO nanocomposite, respectively. Pseudo-first and pseudo-second order equations, Intraparticle diffusion and Bangham’s models were considered to evaluate the rate parameters and sorption mechanism. Sorption kinetics were better reproduced by the pseudo-second order model (R2 > 0.999), with an activation energy (Ea) of +99.74 kJ/mol and +62.95 kJ/mol for ZnO nanoparticles and diatomite-supported ZnO nanocomposite, respectively. In order to specify the type of sorption reaction, thermodynamic parameters were also determined. The evaluated ΔG* and ΔH* indicate the non-spontaneous and endothermic nature of the reactions. The results of this work suggest that both of the used materials are fast and effective adsorbents for removing Th(IV) from aqueous solutions and chemical sorption plays a role in controlling the sorption rate.

Elemental characterization of lignite from Afşin-Elbistan in Turkey by k0-NAA

Twelve samples of lignite from several places and depths of the Kışlaköy open cast mine in the south eastern Turkey were characterized by k0-NAA with emphasis on the potentially hazardous elements, such as As, Cd, Co, Cr, Mn, Ni, S, Sb, U. In total 39 elements were determined at least in some of the samples. The results showed a low quality and elemental inhomogeneity of the lignite material, which is used in the nearby thermal power plant. Mean values of element contents were also compared with older data from the same locality and to the world average lignite composition.

Kinetic modeling of selenium (IV) adsorption for remediation of contaminated aquatic systems based on meso-scale experiments

AbstractThe present study involves selenium (IV) adsorption onto organic pillared bentonite using batch experiments and kinetic modeling, at two different temperatures. selenium (IV) remediation in an aqueous environment, such as contaminated drinking water, groundwater, and industrial wastewater, is the aim of this study. The experimental data were tested with both surface reaction-based and diffusion-based kinetic models to clarify the controlling mechanism of the adsorption process from both microscopic and macroscopic point of view. Among all the investigated models, the most appropriate was the pseudo-second-order surface reaction-based kinetics model. The obtained results proved that the adsorption process at a selenium dioxide concentration of 300 mg L−1 is controlled by the diffusion rate of penetrated selenium (IV) into the reacted layer.

Selenium Adsorption on Activated Carbon by Using Radiotracer Technique

Selenium (Se) is an essential trace element for human beings and plays important roles in human health but it is also toxic at concentrations above 1 mg of selenium per kg of body weight. Therefore, elimination of selenium ions from aqueous solutions is important. Se can be eliminated by using activated carbon as an adsorbent. Radiotracer concept is applicable for observation of elimination mechanism. For this reason, selenium radioisotope can be used as tracer. Selenium dioxide is irradiated in the central thimble of ITU TRIGA Mark II Training and Research Reactor for radiotracer production. Radioactivity measurements are carried out by the gamma-ray spectroscopy system to determine the effect of different experimental parameters. The relative importance of test parameters like concentration of adsorbate, pH of the solution, and contact time on adsorption performance of activated carbon for selenium ion is examined. Typical adsorption isotherms (Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin) are determined for the mechanism of sorption process. Evaluation of experiments for different parameters shows possibility of elimination of selenium from aqueous media by using activated carbon.

Feasibility study of k 0-INAA at the ITU TRIGA Mark II research reactor, Turkey

This work is focused on testing the implementation of k0-INAA using Kayzero for Windows and k0-IAEA software packages at the ITU TRIGA Mark II research reactor. The neutron spectrum parameters were determined using the bare triple-monitor method with Au and Zr monitors. The k0-INAA performance was tested by analysis of NIST SRMs 2711 Montana Soil and 1547 Peach Leaves. The performance assessment based on the En criterion showed that the concentrations of a number of elements in both NIST SRMs determined by both software packages are in agreement with NIST values.

Investigation of Salt Diffusion in Soil by Using Radiotracing Technique

In this study, it is aimed to observe diffusion of sodium in soil samples by using radiotracing technique. To produce the radiotracer 24Na, sodium-carbonate compound was irradiated at ITU TRIGA Mark II Research reactor at Energy Institute of Istanbul Technical University. The irradiated sodium-carbonate samples were sprinkled to the surface of soil columns. Then soil was watered with representative amounts of water according to selected rain regimes in Istanbul. Radioactivity measurements were carried out by using high efficiency gamma-ray measurement system at the outside of the column for different soil depths in different times.

Comparison of relative INAA and k0-INAA using proficiency test materials at ITU TRIGA Mark II research reactor

Proficiency testing is an important way of evaluating the analytical method used in the laboratory. In recent years, neutron activation analysis studies performed in ITU TRIGA Mark II reactor comprised five proficiency tests organized by Wageningen evaluating programs for analytical laboratories. In this study, the results obtained by relative INAA and k0-INAA method for 16 elements in soil and plant samples are presented. Since both methods have some advantages compared to each other, the possible approach for the laboratory should be to combine relative INAA and k0-INAA results.

Assessment of Adsorption Parameter Effectiveness for Radio-Selenium and Radio-Iodine Adsorption on Activated Carbon

Selenium and iodine are found in human body and primarily used in nutrition, and excess or absence of them can lead to diseases. Therefore, their possible dispersion to environment through mining and reprocessing of metals, combustion of coal and fossil fuel, nuclear accidents, or similar activities needs remediation. Adsorption is one of the useful techniques to remove pollutants. In this study, a factorial design is used to determine the effect of pH, concentration of adsorbate, and contact time upon adsorption. Adsorption capacities of radio-selenium and radio-iodine were evaluated for factorial design using activated carbons. The used activated carbon samples were prepared by chemical and physical activation methods. Radioactivity measurements were carried out by using high-resolution gamma spectroscopy system. Results of the research lead to provide useful information about energy generation and management processes by preventing hazardous elements’ dispersion to the environment.