Direktna metoda za određivanje ukupne alfa/beta aktivnosti u vodama

Monitoring of environmental samples, drinking and surface waters, is continuously carried out, demanding development of methods that are both reliable and accurate on one side, but as simple and fast as possible, on the other. Screening tests such as gross alpha/beta activity measurements in water samples are one liquid scintillation counting (LSC) technique widely used as an efficient tool for radiological assesment and estimation whether water sample needs further analysis or not. In this paper, establishment of rapid gross alpha/beta screening technique in waters has been presented, which assumes modification of conventional ASTM D 7283-06 method, since samples were directly mixed with liquid scintillation cocktail, without any sample pretreatment. Method’s optimization involved sample-to-cocktail ratio determination based on the achieved detection limit and sample’s quench level. Optimal value of Pulse Shape Analysis (PSA) discriminator that considerably improves performance of LSC technique through alpha/beta spectra separation during radiological quality measurements of drinking waters has also been investigated. Results of calibration experiments and method’s validity measurements on spiked samples with 241Am and 90Sr/90Y aqueous standards are presented. Achieved detection limits for 300 minutes of counting are MDAα=0.294(11) Bq l-1 and MDAβ=0.405(5) Bq l-1, in alpha and beta window, respectively. Direct alpha/beta method provides deviations up to 40% from reference values, but it offers advantages over conventional alpha/beta measurements, it is ultra fast, simple and inexpensive test for efficient screening of water samples.Rutinski monitoring pijaćih i površinskih voda sprovodi se kontinuirano i nameće potrebu za razvojem metoda koje su, s jedne strane, pouzdane i tačne, ali istovremeno, jednostavne i brze. Screening testovi radi procene ukupne alfa/beta aktivnosti u uzorcima voda, jedna su od često primenjenih tehnika tečne scintilacione spektroskopije, kojima se efikasno može utvrditi da li uzorak zahteva dalju radiološku analizu ili ne. U radu je predstavljena optimizacija brze direktne metode za ispitivanje ukupne alfa/beta aktivnosti u vodama, uz prikaz i diskusiju postignutih granica detekcije. Ova metoda je modifikacija standardne test metode ASTM D 7283-06 za ispitivanje ukupne alfa i beta aktivnosti i podrazumeva direktno mešanje uzorka vode sa scintilacionim koktelom. Na taj način, uzorak je spreman za merenje bez prethodne pripreme koja, prema standardnim metodama, obično podrazumeva duge procedure poput uparavanja do suvog ostatka. Optimizacija metode sastoji se u određivanju optimalnog odnosa uzorak: scintilacioni koktel na osnovu granica detekcije (MDA) u alfa i beta kanalima, kao i nivoa prigušenja u uzorcima, uzimajući u obzir i maksimalni kapacitet određenog koktela. Podešena je vrednost PSA (Pulse Shape Analysis) diskriminatora u cilju optimalne separacije alfa i beta spektara i redukcije pozadinskih efekata. Kalibracija i validacija metode je izvršena standardnim referentnim materijalima, rastvorima 241Am i 90Sr/90Y. Utvrđeno je da za 300 minuta merenja tečnim scintilacionim brojačem, mogu se izmeriti koncentracije aktivnosti koje premašuju vrednosti MDAα=0,294(11) Bq l-1 i MDAβ=0,405(5) Bq l-1 u alfa i beta kanalima, respektivno. Rezultati validacije metode pokazuju da maksimalna relativna odstupanja mogu iznositi do 40%, što je prihvatljivo, uzimajući u obzir da metod nije predviđen za precizno merenje koncentracija aktivnosti pojedinih radionuklida, već za celokupnu procenu radiološke bezbednosti uzoraka voda.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин

Radioactivity Concentrations in Spa Waters - Dose Assessment

In this study 6 different spa water samples from Serbia, Hungary and Czech Republic were investigated in order to determine their radioactivity concentrations. These waters have been used on a large scale for medical and bathing purposes; for therapy, rehabilitation and recreation and also used for drinking, which is the most important. The obtained results showed that natural activity concentrations of alpha emitting radionuclides was within World Health Organization recommended levels and Serbian applicable regulations, but the gross beta activity exceed 1 Bq L-1 for some of the samples. Considering the fact that gross beta activity in four samples was higher than recommended levels, gamma spectrometric measurements were performed, in order to identify radionuclides which caused increase of the gross beta activity. It was found that K-40 was responsible for the elevated gross beta activity. Based on the obtained results the annual effective dose was calculated.3rd International Conference on Radiation and Applications in Various Fields of Research (RAD), Jun 08-12, 2015, Budva, Montenegr

Comparison of two different methods for gross alpha and beta activity determination in water samples

Measurement of the gross alpha and beta activity concentrations in various matrices is suitable as a preliminary screening procedure to determine whether further analysis related to specific radionuclide is necessary. In Serbia, according to current regulations, radioactivity concentrations in drinking water for gross alpha and gross beta should be LT 0.5 and LT 1.0 Bq L-1, respectively. The generally accepted methods for gross alpha and beta activity analysis of drinking water in different countries are: EPA 900.0 and ISO methods (ISO 9696, water quality - measurement of gross alpha activity in non-saline water - thick source method, and ISO 9697, water quality - measurement of gross beta activity in non-saline water). This paper describes comparison of preparations and measurement gross alpha and beta activity in bottled mineral waters as well as in tap waters in Serbia using two methods: EPA 900.0 with and without ash, and ISO methods. Concentration of total dissolved solids (TDS) in investigated water samples was determined. Based on obtained TDS, certain volume was evaporated. The instrumentation used to count the gross alpha and gross beta activities for both methods is alpha/beta low level proportional counter Thermo Eberline FHT 770 T

Utjecaj radija na mjerenje radona u vodi – usporedba monofazne i dvofazne tekućinske scintilacijske spektrometrije

Assessment of radiation exposure to drinking, surface, and groundwater and of the associated health risks calls for accurate and precise 226Ra and 222Rn measurements. One method that fits the bill is liquid scintillation counting (LSC), which allows measurements in onephase (homogenous) or two-phase samples. The aim of our study was to compare the measurement efficiency with both variations in Niška Banja spa water, known for its elevated 222Rn content to get a better insight into the stability and behaviour of the samples and 226Ra interference in samples spiked with 226Ra with 222Rn measurement. 226Ra interference was more evident in homogenous, one-phase and much lower in two-phase samples. However, one-phase samples offer more accurate indirect 226Ra measurements. Water-immiscible cocktails (in two-phase samples) have shown a limited capacity for receiving 222Rn generated by Ra decay from the aqueous to organic phase when 222Rn/226Ra equilibrium is reached. We have also learned that samples with naturally high 222Rn content should not be spiked with 226Ra activities higher than the ones found in native samples and that calibration of two-phase samples can be rather challenging if measurements span over longer time. Further research would require much lower 226Ra activities for spiking to provide more practical answers to questions arising from the demonstrated phenomena.Točne i precizne metode za mjerenje aktivnosti 226Ra i 222Rn u pitkim vodama, kao i u površinskim i podzemnim vodama, nužne su kako bi se procijenilo izlaganje zračenju i radiološki rizik za zdravlje stanovništva. Tekućinska scintilacijska spektrometrija (tzv. liquid scintillation counting, krat. LSC) veoma je pogodna metoda za koju je potrebno pripremiti bilo monofazne (homogene) ili dvofazne uzorke. Cilj našega istraživanja bio je usporediti detekcijsku učinkovitost spomenutih metoda na stvarnim uzorcima iz Niške Banje s povišenom koncentracijom aktivnosti 222Rn, u koje je dodana otopina standarda 226Ra, što je dalo uvid u ponašanje tih uzoraka, njihovu stabilnost i utjecaj 226Ra na mjerenje koncentracije 222Rn. Prisutnost 226Ra može se preciznije detektirati u homogenim uzorcima, a dvofazna metoda pouzdanija je pri mjerenju sadržaja 222Rn s manjim 226Ra doprinosom u dobivenim rezultatima. Međutim, u monofaznim uzorcima dobiva se veća točnost pri neizravnom mjerenju koncentracija aktivnosti 226Ra. Nakon uspostavljanja radioaktivne ravnoteže između 222Rn i 226Ra u uzorku, primijećeno je da kokteli koji se ne miješaju s vodom (u dvofaznim uzorcima) imaju ograničeni kapacitet za transfer radijeva potomka 222Rn iz vode u organsku fazu. Također smo zaključili da se uzorci s prirodno povišenim sadržajem 222Rn ne trebaju obogaćivati višim koncentracijama 226Ra od onih pronađenih u stvarnim uzorcima te da je kalibriranje metode s dvofaznim uzorcima izazovno pri mjerenjima koja traju duže vrijeme. Daljnja istraživanja zahtijevaju obogaćivanje znatno nižim koncentracijama 226Ra radi dobivanja praktičnih odgovora na pitanja koja proizlaze iz demonstriranih fenomena

NATURALLY OCCURRING RADIONUCLIDES AND BASIC CHARACTERISTICS OF SOIL AND ASH SAMPLES NEARBY COAL–FIRED POWER PLANTS

Deposition of (fly and bottom) ash generated after coal combustion in the coal fired power plants (CFPP) in Serbia is carried out in active and passive lagoons. Ash waste mixed with water is directly transported to the lagoon currently active and the other one is passive in the stage of temporary inactivity for technical consolidation of ash and drainage and subjected to revegetation process using grass–legume mixtures with the purpose of creating plant cover. In order to obtain similarity, samples studied in this work were all taken from the area covered with grass which included: (1) soil close to CFPP (2 km) and (3) ash from the flat area of associated passive lagoon. Investigated sites were four power plants: TE “Kolubara” (TEK), TE “Morava” (TEM), TE “Nikola Tesla” A (Tent A) and B (Tent B). In order to analyse environmental implications of ash deposition in the surrounding area, basic characteristics such as texture, particle size distribution, pH value, organic matter and carbonate content were determined in the soil and ash samples. Simultaneously, 238U, 226Ra, 210Pb and 232Th activity concentrations were measured as it is known that after elimination of the organic component of the coal in the process of combustion naturally occurring radionuclides activity concentrations in the coal ash could be enhanced up to 10 times. Analyses of differences between soil and ash samples collected in this study showed that for one group of soils some changes of physical and chemical characteristics occurred compared to the rest of the soils. These changes were found to be related to the soil texture, percentages of clay size particles and 232Th/226Ra activity concentration ratios

Biomedical application of electroporation: electrochemotherapy and electrogene therapy

Electroporation refers to exposure of cells to external electric field thatresults in transiently or permanently increased permeability of cell membranes. Cancer treatment, where local application of electroporation to tumor nodules is combined with chemotherapeutic drugs bleomycin or cisplatin is called electrochemotherapy. The antitumor effectiveness of electrochemotherapy is primarily based on direct killing of tumor cells due to the increased chemotherapeutic drug uptake, but other mechanisms, such as vascular disrupting action was also demonstrated. Our group is involved in elucidating the underlying mechanism of vascular disrupting action by studying the changes in cytoskeletal proteins after electrochemotherapy in endothelial cells by immunocytochemistry. In addition, metastatic potential and global changes in gene expression of melanoma cells that survived electrochemotherapy were also studied, demonstrating that metastatic potential of cells is not changed and that a very low percentage of genes are down or up regulated after electrochemotherapy, which further supports its safe use in the clinical setting. Another application of electroporation is delivery of plasmid DNA into the cells for gene therapy. Our group is involved in preparation of plasmid DNA with tissue specific promoters and without genes for antibiotic resistance, thus enabling safe use of gene therapy in line with USA Food and Drug Administration (FDA) and European medicines Agency (EMA) recommendations

Energy efficiency of residential buildings in Serbia

In this paper, presented is the stale-of-the-art of energy Efficiency of residential buildings in Serbia. Special attention is paid to energy efficiency in already existing buildings. The average energy consumption in residential buildings in Serbia is over 150 kWhm(-2) per year, while in developed European countries it is about 50 kWm(-2) per year. In this paper examined is the contribution of ventilation losses, through the windows of low quality, regardless whether they are poorly made, or made from bad materials, or with no adeguate glass. Besides ventilation losses, which are of major importance in our buildings, special attention is paid to transmission losses, which are conseguence of the quality and energy efficiency of the facade. All of the above statements are proved by measurements obtained on a representative building of the Block 34 in New Belgrade, built in the eighties of the last century. In addition to measurements performed the calculation of energy consumption for heating during winter has been made. The results of two different methods of calculation of energy consumption for heating are compared with the values obtained by measuring

Surface chemistry of "boron" doped carbon quantum dots

Carbon quantum dots (CQDs), are a novel class of carbon nanomaterials that exhibit outstanding physical, chemical, and optical characteristics in addition to strong light absorption. By substituting some of the carbon atoms in CQDs for heteroatoms like N, B, P, and S, it is possible to modify the surface chemistry and electronic properties of the structures, boosting their catalytic activity. Adding B dopant to CQDs changes its surface chemistry and morphology, opening up a wide range of potential uses. The presented study illustrates a quick and environmentally friendly method for producing B-CQDs through microwave-assisted method. According to TEM characterization, the generated B-CQDs had a spherical form, an average diameter of 12 nm, and were negatively charged particles with good water dispersibility and no discernible aggregation. The thorough surface chemistry characterization revealed the presence of B-O and B-C bonds, as well as oxygen-containing surface functional groups in the form of hydroxyl, carbonyl, and carboxyl groups. Additionally, using an RB organic dye as a model molecule, the sonocatalytic, photocatalytic, and synergistic effects of the two processes were investigated

Changes of c-myc expression in b16 melanoma cells induced by 8-chloroadenosine-3′, 5′-monophosphate and tiazofurin

The aim of this study was to investigate the in vitro effects of 8- chloroadenosine 3′, 5′-monophosphate (8-Cl-cAMP) and tiazofurin (TR) on the expression of c-myc gene in B16/F10 and B16/C3 mouse melanoma cells. Exponentially growing cells were treated with 8-Cl-cAMP or TR (5µmol - 25µmol) for 6h and 24h. The level of c-myc expression, estimated by RT-PCR, did not significantly change in B16/F10 cells after treatment with 8-Cl-cAMP or TR. Similar results were obtained in B16/C3 cells after treatment with 8-Cl-cAMP. The level of c-myc expression has shown a significant increase in B16/C3 cells after treatment with TR. Further studies of these agents will lead to better understanding of molecular mechanisms of their action.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200