Uticaj meteoroloških parametara na koncentraciju SO2 u Obrenovcu, Srbija

In this paper, the impacts of some meteorological parameters on the SO2 concentrations in the City of Obrenovac are presented. The City of Obrenovac is located in the north-west part of Serbia on the banks of the River Sava. The observed source emission, the power plants TENT A and B are situated on the bank of the Sava River in the vicinity of Obrenovac. During the period from January to November 2006, the concentrations of sulfur dioxide in the air at 4 monitoring sites in Obrenovac were measured. It was noticed that the maximal measured daily concentrations of sulfur dioxide ranged from 1 μg m-3 (16th November, 2006) to 98 μg m-3 (29th January 2006) and lie under the maximal allowed concentration value according to the Serbian Law on Environmental Protection. The measured sulfur dioxide concentrations mostly showed characteristics usual for a daily acidification sulfur dioxide cycle, excluding the specificities influenced by the measuring site itself. Sulfur dioxide transport was recorded at increased wind speeds, primarily from the southeast direction. Based on the impact of meteorological parameters on the sulfur dioxide concentration, a validation of the monitoring sites was also performed from the aspect of their representivity.U radu su predstavljeni rezultati monitoringa koncentracije SO2 u vazduhu u Obrenovcu koji se nalazi na severozapadu Srbije na obalama reke Save. Posmatran je uticaj meteoroloških parametara na koncentraciju SO2 emitovanog iz termoelektrana TENT A i B koji se smatraju najvećim izvorima emisije. U periodu od januara do novembra 2006. godine praćene su koncentracije sumpor-dioksida u vazduhu na 4 merna mesta lokalizovana na različitim udaljenostima od izvora emisije. Maksimalne izmerene dnevne koncentracije sumpor-dioksida su se kretale od 1 μg m-3 (16. novembra, 2006) do 24 μg m-3 (29. januara, 2006). Izmerene promene koncentracija sumpor-dioksida uglavnom pokazuju uobičajene karakteristike dnevne acidifikacije ciklusa uz razlike koje potiču od osobenosti mernih mesta. Transport sumpor-dioksida zabeležen je pri pojačanom vetru prvenstveno iz jugoistočnog pravca. Na osnovu korelacionih odnosa između koncentracije sumpor-dioksida i odgovarajućih meteroloških parametara izvršena je karakterizacija mernih mesta u pogledu njihove reprezentativnosti za merenje sumpor-dioksida

Uticaj meteoroloških parametara na koncentraciju SO2 u Obrenovcu, Srbija

In this paper, the impacts of some meteorological parameters on the SO2 concentrations in the City of Obrenovac are presented. The City of Obrenovac is located in the north-west part of Serbia on the banks of the River Sava. The observed source emission, the power plants TENT A and B are situated on the bank of the Sava River in the vicinity of Obrenovac. During the period from January to November 2006, the concentrations of sulfur dioxide in the air at 4 monitoring sites in Obrenovac were measured. It was noticed that the maximal measured daily concentrations of sulfur dioxide ranged from 1 μg m-3 (16th November, 2006) to 98 μg m-3 (29th January 2006) and lie under the maximal allowed concentration value according to the Serbian Law on Environmental Protection. The measured sulfur dioxide concentrations mostly showed characteristics usual for a daily acidification sulfur dioxide cycle, excluding the specificities influenced by the measuring site itself. Sulfur dioxide transport was recorded at increased wind speeds, primarily from the southeast direction. Based on the impact of meteorological parameters on the sulfur dioxide concentration, a validation of the monitoring sites was also performed from the aspect of their representivity.U radu su predstavljeni rezultati monitoringa koncentracije SO2 u vazduhu u Obrenovcu koji se nalazi na severozapadu Srbije na obalama reke Save. Posmatran je uticaj meteoroloških parametara na koncentraciju SO2 emitovanog iz termoelektrana TENT A i B koji se smatraju najvećim izvorima emisije. U periodu od januara do novembra 2006. godine praćene su koncentracije sumpor-dioksida u vazduhu na 4 merna mesta lokalizovana na različitim udaljenostima od izvora emisije. Maksimalne izmerene dnevne koncentracije sumpor-dioksida su se kretale od 1 μg m-3 (16. novembra, 2006) do 24 μg m-3 (29. januara, 2006). Izmerene promene koncentracija sumpor-dioksida uglavnom pokazuju uobičajene karakteristike dnevne acidifikacije ciklusa uz razlike koje potiču od osobenosti mernih mesta. Transport sumpor-dioksida zabeležen je pri pojačanom vetru prvenstveno iz jugoistočnog pravca. Na osnovu korelacionih odnosa između koncentracije sumpor-dioksida i odgovarajućih meteroloških parametara izvršena je karakterizacija mernih mesta u pogledu njihove reprezentativnosti za merenje sumpor-dioksida

Hydrogen desorption from nanostructured magnesium hydride composites

The influence of 3d transition metal addition (Fe, Co and Ni) on the desorption properties of magnesium hydride were studied. The ball milling of MgH2-3d metal blends was performed under Ar. Microstructural and morphological characterization were performed by XRD and SEM analysis, while the hydrogen desorption properties were investigated by DSC. The results show a strong correlation between the morphology and thermal stability of the composites. The complex desorption behavior (the existence of more than one desorption peak) was correlated with the dispersion of the metal additive particles that appear to play the main role in the desorption. The desorption temperature can be reduced by more than 100 degrees if Fe is added as additive. The activation energy for H2 desorption from the MgH2-Fe composite is 120 kJ/mol, implying that diffusion controls the dehydration process

Combined XRD and XPS analysis of ex-situ and in-situ plasma hydrogenated magnetron sputtered Mg films

Contrary to traditional methods including top layer catalyst deposition and ex-situ hydrogenation in current study Mg-H films were synthesized using magnetron sputtering in Ar+ atmosphere and their in-situ hydrogenation in magnetron induced hydrogen plasma. XRD analysis of hydrogenated Mg-H films revealed changes of preferred crystallographic orientation. After 1-3 h of in-situ plasma hydrogenation XRD does not indicate presence of any crystalline MgH2 phase but it is observed after 5 h. The appearance of significant amount of crystalline MgH2 phase after prolonged time of in-situ hydrogenation presupposed that samples without clear expression of MgH2 crystal phase might still have hydrogen rich amorphous Mg phase which is not observable by XRD. The analysis of predicted hydrogen containing phase was performed using combination of conventional SEM; AFM, Q-Q XRD, GI-XRD and XPS analysis techniques. The obtained data of hydrogen containing phase distribution at the surface of the samples and its distribution depth profiles are presented together with considerations related to the efficiency of the proposed in-situ hydrogenation approach and combined analysis methods. (C) 2015 Elsevier B.V. All rights reserved

Abrasive wear behaviour of ADI material with various retained austenite content

In this paper, the wear rate of ferritic and pearlitic ductile iron, as well as three types of austempered ductile iron (ADI materials), austempered at 300, 350 and 400 degrees C is investigated. Two wear parameters were varied, wear load (0.5, 1.3, 2 kg) and grit paper abrasive grain size (P240, P500, P800). The hardness of ductile iron and stress-assisted phase transformation of retained austenite into martensite (SATRAM) phenomenon in ADI materials were found to play major roles in wear behaviour. The pronounced SATRAM phenomenon was detected for the most severe wear parameters. Another important factor in the occurrence of SATRAM phenomenon is the presence of metastable, low carbon-enriched retained austenite. As a consequence, the wear rate of ADI austempered at 400 degrees C is nearly equivalent to ADI austempered at 300 degrees C at medium and high loading with the coarsest abrasive paper grit tested (P240)

Abrasive wear behaviour of ADI material with various retained austenite content

In this paper, the wear rate of ferritic and pearlitic ductile iron, as well as three types of austempered ductile iron (ADI materials), austempered at 300, 350 and 400 degrees C is investigated. Two wear parameters were varied, wear load (0.5, 1.3, 2 kg) and grit paper abrasive grain size (P240, P500, P800). The hardness of ductile iron and stress-assisted phase transformation of retained austenite into martensite (SATRAM) phenomenon in ADI materials were found to play major roles in wear behaviour. The pronounced SATRAM phenomenon was detected for the most severe wear parameters. Another important factor in the occurrence of SATRAM phenomenon is the presence of metastable, low carbon-enriched retained austenite. As a consequence, the wear rate of ADI austempered at 400 degrees C is nearly equivalent to ADI austempered at 300 degrees C at medium and high loading with the coarsest abrasive paper grit tested (P240)

Changes of hydrogen storage properties of MgH2 induced by heavy ion irradiation

In order to understand the influence of defect zones on desorption behavior of MgH2, Xe 120 keV ion irradiation of this material has been performed. DSC, SEM measurements, and SRIM calculations have been used to characterize induced modifications and its influence on the hydrogen desorption behavior of MgH2. We have demonstrated that the near-surface area of MgH2 plays the crucial role in hydrogen desorption kinetics. DSC analysis provides clear picture of vacancies influence on H diffusion and desorption in MgH2, and points out that there is possibility to control the thermodynamic parameters by controlled ion bombardment. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Hydrogen storage properties of MgH2 mechanically milled with alpha and beta SiC

To understand the influence of various crystallographic phases on hydrogen storage properties, ball milling of MgH2 with hexagonal (alpha) and cubic (beta) SiC have been performed. Structural characterization of all samples has been done by X-ray diffraction (XRD) analysis, particle size analysis and scanning electron microscopy (SEM). Investigation of hydrogen desorption properties of prepared nanocomposites has been done using temperature programmed desorption (TPD) technique. Despite the results of structural and morphological characterization of obtained nanocomposites are very similar, TPD spectra show significant differences regarding existence of intermediate temperature peak. In the sample milled with hexagonal SiC this peak originates both from H-2 and H2O, while in the sample milled with cubic phase it only comes from H2O. Both samples exhibit low temperature H-2 peak at 385 K. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Changes of structural and hydrogen desorption properties of MgH2 indused by ion irradiation

Changes in structural and hydrogen desorption properties of MgH2 induced by ion irradiation have been investigated. MgH2 powder samples have been irradiated with 45 keV B3+ and 120 keV Ar8+ions, with ion fluence of 1015 ions/cm2. The effects of ion irradiation are estimated by numerical calculations using SRIM package. The induced material modifications and their consequences on hydrogen dynamics in the system are investigated by XRD, particle size distribution and TPD techniques. Changes of TPD spectra with irradiation conditions suggest that there are several mechanisms involved in desorption process which depend on defect concentration and their interaction and ordering. The results confirmed that the near-surface area of MgH2 and formation of a substoichiometric MgHx (x<2) play a crucial role in hydrogen kinetics and that various concentrations of induced defects substantially influence H diffusion and desorption kinetics in MgH2. The results also confirm that there is possibility to control the thermodynamic parameters by controlling vacancies concentration in the system

The potential of ball-milled Serbian natural clay for removal of heavy metal contaminants from wastewaters: Simultaneous sorption of Ni, Cr, Cd and Pb ions

The influence of mechanical milling of natural Serbian clay on removal of heavy metals from an aqueous medium was investigated. The simultaneous sorption of the 4 toxic heavy metals (Ni, Cr, Cd and Pb), which are often present together in numerous polluting spills and in agrochemicals was evaluated. Microstructural and morphological changes in the ball-milled clay were characterized by X-ray diffraction (XRD), particle size distribution (PSD) and scanning electron microscopy (SEM). Induced changes in microstructure were correlated to the cation exchange capacity (CEC), determined by the EPA Method 9081. The CEC value has increased from 77 meq/100 g for the unmilled clay, to 95 meq/100 g for the milled clay. Regarding the untreated clay, the cation competition reveal some differences in their sorption: complete sorption (about 98% of the initial concentration) was achieved for Cr and Pb, while about 19% of the initial concentration of Cd and Ni still persist in the solution. The order of affinity of the metal ions is Pb approximate to Cr GT Cd approximate to Ni and it has not changed upon milling. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved