Sevilay Haciyakupoglu

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.

Bentonite modification with hexadecylpyridinium and aluminum polyoxy cations and its effectiveness in Se(IV) removal

Usage of bentonite as a buffer material is suggested in radioactive waste repositories. Although bentonites have higher sorption ability to cations, they cannot adsorp anions due to negative surface charge. Nowadays, ongoing researches focus on increasing anion adsorption ability of the bentonites with modification. Organic-pillared bentonite (OPBent) was produced by modification of sodium bentonite with aluminum polyoxy and hexadecylpyridinium cations in this study. Variation in structure after modification was demonstrated by using different characterization techniques. Se removal efficiency of OPBent is investigated by using (75)Se, since selenium (Se) is one of the important long lived fission products found in radioactive waste and has toxic anionic species in an aqueous environment. The effect of reaction time, solid/liquid ratio, pH and concentration on the adsorption performance were examined. Se speciation and its effect onto adsorption were also investigated by measuring Eh-pH values under certain experimental conditions. Additionally, importance of the amount of Al-polyoxy cations used in modification was investigated by comparing these results with the results of other organic-pillared bentonite produced in our previous research. Experimental results confirmed that both cations were successfully placed into the bentonite interlayer and significant change in the host structure leads to increase Se adsorption. Consequently, bentonite modification improves its Se adsorption ability and further investigations are needed related to the usage of this adsorbent in other remediation studies especially in sorption of other anionic pollutants.

Determination of235U/238U ratio by instrumental neutron activation analysis

The235U/238U ratio is determined by neutron activation analysis counting the ϕ-rays of short half-lives fission products and239U. The effect of the neutron spectrum hardening using a6LiD converter is also demonstrated. The235U/238U ratio is determined using short irradiation, waiting and counting times.

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.

Instrumental neutron activation analysis of plant tissues and soils for biomonitoring in urban areas in Istanbul

The aim of this study was to determine the elemental concentrations of plant tissues and soils collected in Istanbul to evaluate the possible use of selected tree species, Carpinus betulus L., Quercus petraea (Mattuschka) Liebl., Tilia argentea Desf. ex DC., as biomonitors. The concentrations of 26 elements were determined by k0-INAA using Kayzero for Windows software. Generally, the element concentrations in samples from urban areas were found to be higher than those of control area. Tilia argentea Desf. ex DC. may be an effective biomonitor for As, Br, Ca, Cl, Cr, Fe, Hf, K, Sb, Sc, Sr, and Th.

Evaluation of Rubidium and Potassium Diffusion in Soil by Radiotracer Technique

In this study, diffusion of rubidium and potassium in soil was observed representing two alkaline elements. Generally, these elements are found as salt compounds in the earth. Soil columns were prepared in the laboratory conditions. Rubidium chlorite and potassium nitrate compounds were irradiated at ITU TRIGA Mark II nuclear research reactor at the Energy Institute of ITU to produce the radiotracer 86Rb and 42K. The irradiated compounds were sprinkled to the surface of different soil columns and were watered with realistic amounts. Radioactivity measurements were carried out by using a scintillation detector at the outside of the column for different soil depths in different diffusion times. As the results of the study, the behavior of two alkaline elements was observed appropriately similar in the soil.

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.