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Investigation on the content of potentially toxic elements and organic compounds in the water sample from the Pek river (Ujevac, Serbia)
Get PDFUzorci vode iz reke Pek uzeti su u proleće 2022. godine. Analiza potencijalno toksičnih
elelemata (Hg, As, Zn, Cd, Pb, Ni, Fe, B, Cr, Mn i Cu) izvršena je pomoću optičke
emisione spektroskopije sa induktivno spregnutom plazmom (ICP-OES), a aromatičnih
ugljovodonika, policikličnih aromatičnih ugljovodonika i fenola gasnim hromatografom sa
masenom spektometrijom (GC-MS). Koncentracije Mn prelazile su MDK vrednosti
propisane za vodu. Od organskih jedinjenja, detektovani su samo fluoranten, naftalen i
fenantren. Fluorescentna spektroskopija korišćena je za skrining vode na prisustvo
aromatičnih jedinjenja. Dobijeni rezultati pokazali su da se ova metoda može koristiti kao
brzi alat za skrining kvaliteta vode.Water samples from the Pek river were collected in the spring 2022. Analysis of potentially
toxic elements (Hg, As, Zn, Cd, Pb, Ni, Fe, B, Cr, Mn, and Cu) was performed using
inductively-coupled plasma optical emission spectrometry (ICP-OES), and aromatic
hydrocarbons, polycyclic aromatic hydrocarbons, and phenol by gas chromatography-mass
spectrometry (GC-MS). Mn concentrations exceeded the MAC values prescribed for water.
Of organic compounds, only fluoranthene, naphthalene, and phenanthrene were detected.
Fluorescence spectroscopy was used for water screening on presence of aromatic
compounds. The results indicated that this method could be used as a fast screening tool for
water quality analysis
Relationships of otolith size to fish size – a study on pumpkinseed (Lepomis gibbosus) from Topola Reservoir (Serbia)
Get PDFOtoliths are calcareous structures commonly used for fish age, size, and taxon determination. Information obtained from the analysis of otoliths can be of great importance for the management of fish populations, including invasive fish species. Pumpkinseed (Lepomis gibbosus) is one of the most successful invaders of Serbian freshwaters. It preys on aquatic invertebrates, fish eggs, and small fish. This species shows high plasticity of life history traits and can tolerate harsh environmental conditions, including hypoxia and high water temperatures. In October of 2020, a total of 28 pumpkinseed individuals from Topola reservoir (44.268229 N, 20.691564 E) were caught with electrofishing device Villager VGI2400 (230 V, 8.7 A, 2.0 kW). In order to determine relationships of otolith to fish size, a total length (TL) and body weight (BW) of each fish were measured as well as otolith area (OA), perimeter (OP), length (OL), and weight (OW). There were no significant differences between left and right otolith regarding OA, OP, OL, and OW (t-test, P>0.94). Significant and strong correlations were recorded for TL and OA (r2=0.936, P<0.0001), TL and OP (r2=0.958, P<0.0001), TL and OL (r2=0.945, P<0.0001), and TL and OW (r2=0.838, P<0.0001). Additionally, significant and strong correlations were recorded for BW and OA (r2=0.844, P<0.0001), BW and OP (r2=0.819, P<0.0001), BW and OL (r2=0.828, P<0.0001), and BW and OW (r2=0.795, P<0.0001). Results indicated that TL-OP relationship is the best predictor of pumpkinseed length, while BW-OW relationship is the weakest predictor of pumpkinseed weight. The common linear regression equations were determined: y = 0.9004x + 3.2643 for OA-TL, y = 0.9079x – 0.4816 for OP-TL, y = 2.4873x – 0.6667 for OL-TL, y = 523.2832x + 5.2364 for OW-TL, y = 3.2985x – 9.6439 for OA-BW, y = 3.2389x – 22.5237 for OP-BW, y = 8.9825x – 23.5786 for OL-BW, and y = 1966.5664x – 2.7114 for OW-BW. The obtained equations allow the calculation of pumpkinseed TL and BW based on the set of data on the morphological characteristics of the otoliths. Of the considered otolith parameters, otolith weight is the least suitable character for estimation of pumpkinseed size
Security Enhancement of Joint Procedure Based on Improved Elliptic Curve Cryptography in LoRaWAN
No full textFor long-range communication, Long-Range Wide Area Network (LoRaWAN) is the appropriate media access layer protocol. This LoRaWAN protocol connects the end devices and the application server through the gateways. The end devices can join the LoRaWAN network by following two processes such as Over-The-Air-Activation (OTAA) and Activation-By-Personalization (ABP). The joining request from the end devices is unencrypted during the process of OTAA. So, to improve the joining process in OTAA, joining requests from the end devices are encrypted using the improved elliptic curve cryptography (ECC) in this paper. To enhance the performance of ECC, the private key is selected optimally using the Artificial Flora (AF) algorithm. AF algorithm solves some complex, non-linear, discrete optimization problems. The proposed novel method of AF-based ECC (AF-ECC) performance outperforms conventional ECC based on latency, timeout messages, and throughput, which is depicted in simulation results
The Danube River in Serbia
Get PDFOver 2850 km long, the Danube River is certainly the most important river in Europe, flowing through Germany (687 km), Austria (358 km), Slovakia (172 km), Hungary (417 km), Croatia (138 km), Serbia (587 km), Bulgaria (472 km), Romania (1075 km), Moldovia (<1 km) and Ukraine (54 km) in a west-east direction, and representing a “water backbone” for many European countries located in its basin
Palladium-copper bimetallic surfaces as electrocatalysts for the ethanol oxidation in an alkaline medium
No full textTwo types of Cu-modified Pd catalysts supported on high area carbon were prepared: Pd nanoparticles modified
with a sub-monolayer of underpotentially deposited Cu (Cu@Pd/C) and Pd-Cu alloy nanoparticles (Pd-Cu/C),
and examined for the ethanol oxidation reaction (EOR) in alkaline solution. The catalysts were characterized by
energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron
spectroscopy, as well as cyclic voltammetry. As reference catalysts, Pd/C and Pt/C were used. The electrochemically
active surface area of all samples was determined from COads and Cuupd desorption and Pd oxide
reduction, and used to assess their intrinsic activity for EOR. Intimate contact of Pd with Cu atoms enhanced its
activity, regardless of the type of bimetal catalyst. The atomic Pd:Cu ratio between 2:1 and 4:1 appears to be
optimal for high activity. The most active catalyst under the potentiodynamic conditions was Cu@Pd/C with
θ(Cu) = 0.21,although Pd-Cu/C was superior during the potentiostatic test. All bimetallic catalysts surpassed
Pd/C in mass activity. The EOR activity of Pt/C was higher compared to Pd-based catalysts at low potentials,
both in terms of specific and mass activity, but with a significant decline over a 30-min potentiostatic stability
test
Tailoring of BaCe0.9Y0.1O3-d Electrolyte Properties by Co-Doping
Get PDFBaCe0.9Y0.1O3–δ has been known as one of the best proton conducting electrolyte, which enables its application in intermediate-temperature solid oxide fuel cells (IT-SOFC) operating between 500 °C and 700 °C. The main disadvantage of this material is its instability in a CO2-rich atmosphere that limits its application with respect to fuel selection. Therefore, many attempts has been made to improve its stability by replacing yttrium with other dopants, or by co-doping.
In this study, we compared BaCe0.9Y0.1O3–δ and BaCe0.85Y0.1M0.05O3–δ (M = {In, Zr, Nb}) electrolytes by taking into consideration the dopant properties (primarily the valence, electronegativity and ionic radius) and how they influenced the microstructure, conductivity and chemical stability of doped BaCeO3. The samples were synthesized by the citric-nitric autocombustion method. BaCe0.85Y0.1In0.05O3–δ was sintered at 1400 °C for 5 h in air, while the temperature of 1550 °C was required for the other materials to complete the sintering. This makes the doping with In a preferable method since sintering temperatures above 1500 °C can lead to a certain materials degradation resulting in BaO loss. The total conductivities (σ) measured at 700 °C in wet hydrogen decreased in the following order:
BaCe0.9Y0.1O3–δ > BaCe0.85Y0.1Zr0.05O3–δ > BaCe0.85Y0.1Nb0.05O3–δ > BaCe0.85Y0.1In0.05O3–δ. By comparing the stability of the ceramics exposed to a 100% CO2 atmosphere at 700 °C for 5 h and examined by X-ray analysis, it was observed that only BaCe0.85Y0.1In0.05O3–δ could sustain the aggressive environment. The exposed sample contained only traces of secondary phases, while the other compositions were partially or significantly decomposed. By taking into account the values of the Goldschmidt tolerance factor (t) and dopant electronegativit
Characterisation, axial anisotropy, and formation conditions of celestine minerals from the Jabal Eghei (Nuqay) late Neogene – Pleistocene volcanic province, southeastern edge of the Sirt Basin, southern Libya: Constraints on the mineralogical geothermometer
No full textFive celestine crystals were sampled from the (palaeo)surface intervening between the late Miocene to Pleistocene basaltic sequences of the Jabal Eghei (Nuqay) volcanic province in southern Libya and then characterised by applying a combination of the SEM–WDS, ICP/OES, PXRD and IR methods. Colour variations and related minerogenetic frameworks were also investigated. Three samples have greenish-blue-to-blue colour (480.4–482.5 nm), whereas the other two samples have blue–green colour (cyan; 489.1–494.1 nm). The colour purity ranges from 1.36–7.16. Their composition is similar, end-member celestine, in which only 1.6–4.1 at.% of Sr2+ content was substituted by Pb2+ (0.7–0.9 at.%), Ba2+ (0.5–0.7 at.%) and Ca2+ (0.2–0.8 at.%). Three samples contained vacancies, from 1.0 to 1.9 at.%. The content of other chemical elements is minor. The resulting unit-cell parameters have the ranges: a0 = 8.3578(9)–8.3705(6) Å; b0 = 5.3510(5)–5.3568(4) Å; c0 = 6.8683(7)–6.8767(2) Å and V0 = 307.17(5)–308.34(4) Å3. The PXRD and IR results are mainly in accordance with the SEM–WDS results, with a high level of correlation. However, a few discrepancies were found, producing several possible interpretations, the primary cause being a slight unit-cell axial anisotropy i.e. thermal expansion. As a consequence these results yield a new geothermometric tool that is based on the unit-cell axial anisotropy. The celestines investigated were formed during a Miocene intraplate volcanism with basaltic magmas, and associated brines lifted by the structural conduits (normal faults crosscutting the Sirt basin). The Sr-bearing fluids then poured into and over the faulted and fractured lagoon-type gypsum, anhydrite Eocene sediments. The celestine mineralisation formed within a ~368–430 K (~95–157°C) temperature range. The celestine formed at slightly elevated temperature and pressure conditions, close to the shallow subsurface environment (over 250 bars)
Applicability of wastewater based epidemiology in countries with poor wastewater treatment – COVID-19 case study in Serbia
No full textPollution of natural water bodies is one of the biggest challenges in developing countries, such as Serbia, where wastewater is discharged directly into the recipients without proper treatment and poses serious threats to surface water quality, general safety and environmental health. Numerous pathogenic microorganisms, bacteria, viruses, protozoa and helminthes may reach surface waters and eventually contaminate groundwater. Despites its extreme importance in this case, implementation of wastewater-based epidemiology is a challenge for developing countries, as the majority of households are not connected to sewerage systems. Within our research, we have placed major focus on recipients of wastewaters as an alternative of targeting raw wastewater. During the fourth COVID-19 wave in Serbia that started in late February 2021 multiple water samples were collected at 12 sites at Sava and Danube Rivers in the Belgrade city area which are under the impact of untreated wastewaters. SARS-CoV-2 RNA was quantified using RT-qPCR with primer sets targeting nucleocapsid (N1 and N2) and envelope (E) protein genes. Microbiological (standard fecal indicator bacteria and microbial faecal source tracking markers), epidemiological, physico-chemical and hydro-morphological parameters were analysed in parallel. Out of 44 samples analyzed, 31 were positive for at least one of the target regions of SARS-CoV-2. The results indicated that surveillance of SARS-CoV-2 RNA in surface waters in context with the large amount of epidemiological and environmental metadata can be used as epidemiological early-warning tool in countries with poor wastewater treatment
Relationship between mineral nutrition, plant diseases, and pests
No full textMineral nutrient supply or tissue concentrations affect plant diseases and pests in various ways. The supply of nutrients
changes the resistance of plants to pathogens and pests by altering growth and tissue composition (e.g., concentration of
soluble compounds or defense compounds), the expression of plant defense and pathogen/pest virulence genes, and the
interactions with beneficial soil microorganisms. Depending on the pathogen or pest and nutrient, adequate nutrient supply
for optimal plant growth may increase or decrease disease incidence. This chapter discusses the effects of nutrient
supply on foliar and soil-borne fungal and bacterial diseases as well as on pests. Calcium and B inhibit pathogen invasion
via their stabilizing effect on cell walls and membranes. Silicon and Mn play important roles in defense reactions
to pathogen infection or pest attack, whereas N and K exert their effects mainly via modulating the concentrations of
soluble compounds in plant tissues. The effects of crop management (e.g., timing and form of fertilizers, liming, and/or
biological agents) on disease incidence are outlined
Hydrothermally synthesized CeO2/ZnO nanocomposite photocatalysts for the enhanced degradation of Reactive Orange 16 dye
No full textIn this work, in order to improve the photocatalytic efficiency of ZnO, the optimal CeO2 content in ZnO powders was determined by varying the quantity of CeO2 from 0 to 10 mol%. The structural, microstructural, optical, textural, and photocatalytic properties of the hydrothermally obtained ZnO and CeO2/ZnO nanocomposites have been investigated by using the XRPD, FESEM, HRTEM/SAED, BET, and UV–Vis techniques. Detailed characterization revealed that CeO2, having spherical nanodots of about 5 nm with a large surface area, was distributed onto the ZnO surface, whose crystallites displayed a bimodal distribution, from nano-to micro-crystals. The morphology of ZnO is a combination of nanograins and microrods that further makes a 3-D tie-like morphology. The nanocomposite containing 5 mol% of CeO2 showed about 30% better photocatalytic efficiency in the degradation of Reactive Orange 16 dye compared to other samples under simulated solar radiation. In addition, the kinetics and mechanism of photocatalytic degradation were also proposed based on the photocatalytic activity and scavenger tests