Average Surface Concentration Research Articles

On accounting for emissions of pollutants from autonomous heat supply sources of individual residential buildings when conducting summary calculations of atmospheric air pollution for settlements

Introduction. Autonomous sources of heat supply (ASHS) can make a crucial contribution to the level of atmospheric air pollution in settlements. However, emissions from ASHS in most cases are either not included in the summary calculations of atmospheric air pollution at all or estimated with significant uncertainties. 
 The purpose of this study was a hygienic assessment of methods and results of accounting for emissions of pollutants from the ASHS of individual residential buildings when conducting summary calculations of atmospheric air pollution for settlements. 
 Materials and methods. the original methodology of a phased survey of the city’s ASHS was used and the results of summary calculations of atmospheric air pollution in 18 cities conducted using this methodology are presented. Calculations of single, average seasonal (for the cold period) and average annual surface concentrations of pollutants were carried out in accordance with current regulatory documents using the unified software for calculating atmospheric pollution (UPRZA) “Ecologist-city”. In all the studied cities a significant number of sources of atmospheric air pollution was established to be ASHS. In more than 90% of these sources, coal and firewood were used as energy carriers. The greatest excess of hygienic standards of atmospheric air quality was noted 
 for benz(a)pyrene. In 15 cities, the highest calculated maximum single surface concentration of at least one pollutant created by emissions from ASHS exceeded the maximum allowable single concentration (MACs). 
 Limitations of the study are due to the fact that direct instrumental measurements to determine the characteristics of emissions from ASHS into the atmosphere are impossible. 
 Conclusions. The area of the city’s territory where the estimated maximum single surface concentration of at least one pollutant exceeded the MACs, reached 45%, and the seasonal average concentration exceeded maximum allowable average annual concentration on 50% of the territory. The most effective measure to reduce air pollution by emissions from ASHS is the replacement of solid and liquid mineral fuels with natural gas. Unification of methods of accounting and inventory of ASHS as sources of atmospheric air pollution is required.

Deterioration of air quality associated with the 2020 US wildfires

The wildfires of August and September 2020 in the western part of the United States were characterized by an unparalleled duration and wide geographical coverage. A particular consequence of massive wildfires includes serious health effects due to short and long-term exposure to poor air quality. Using a variety of data sources including aerosol optical depth (AOD) and ultraviolet aerosol index (UVAI), obtained with the Moderate-Resolution Imaging Spectroradiometer (MODIS), Multi-Angle Implementation of Atmospheric Correction (MAIAC) and Tropospheric Monitoring Instrument (TROPOMI), combined with meteorological information from the European Center for Medium-Range Weather Forecasts (ECMWF) and other supporting data, the impact of wildfires on air quality is examined in the three western US states, California, Oregon, and Washington, and areas to the east. The results show that smoke aerosols not only led to a significant deterioration in air quality in these states but also affected all other states, Canada, and surrounding ocean areas. The wildfires increased the average daily surface concentration of PM2.5 posing significant health risks, especially for vulnerable populations. Large amounts of black carbon (BC) aerosols were emitted into the atmosphere. AOD and UVAI exceeded 1 and 2 over most of the country. In parts of the three western states, those values reached 3.7 and 6.6, respectively. Moreover, a reanalysis based on MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, version 2) showed that the maximum values of BC surface mass concentration during the wildfires were about 370 μg/m3. These various indicators provide a better understanding of the extent of environmental and atmospheric degradation associated with these forest fires.

Study of capture efficiency utilizing passive mixing in heterogeneous microfluidic immunosensors

The role of 3-dimensional (3-D) geometries in facilitating surface reactions in microchannels is the subject of the present work. 3-D microfluidic immunosensor geometries inspired from the design of packed bed columns, utilizing splitting and recombination of flows in improving the transport in flow heterogeneous microfluidic immunosensors, were studied systematically. First, the effect of the passive mixing on the antigen capture was tested experimentally using prostate specific antigen (PSA) and anti-PSA and validated using numerical studies. Subsequently, numerical studies on the effects of geometrical parameters like the height and width of the microchannel, the height and width of the grooves, number of groove sets, the ratio of the heights of the grooves and the microchannel etc., on the antigen capture were conducted. The Sherwood number (Sh) and Peclet number (Pe) were used to explain the mass transfer. Finally, the optimum Peclet number (Pe∼x223C 3400) was found, having a maximum figure of merit ratio for the grooved to the ungrooved microchannels Correlations were also obtained between the average surface concentration and the geometrical parameters. The paper presents novel scientific results which are useful for designing efficient heterogeneous immunosensors.

Assessment of the ecological and social potential of the organization of ecological zones to ensure sustainable transport development of territories

The article presents the results of an assessment of the impact on the environment and public health of measures to prohibit entry into a certain territory of the city of cars belonging to low environmental classes (“ecological zone” or “ecozone”). When justifying the choice of the city on the example of which the research was conducted (Novosibirsk), both environmental and socio-economic aspects were taken into account. The assessment of the environmental impact of the ecozone organization consisted in modeling traffic flows on the road network before and after the organization of the ecozone, estimating the emissions of pollutants from the totality of traffic flows, calculating the maximum and average annual surface concentrations of the considered pollutants on the territory of the ecozone. Based on the calculated average annual concentrations of pollutants, characteristics of the population density living in the ecozone, and scenarios of its interaction with pollutants, public health risk assessments were carried out before and after the organization of the ecozone. Studies have shown that the change in gross emissions of major pollutants during the organization of the ecozone in Novosibirsk will be 40…60%. Ground-level concentrations of these pollutants will decrease by about the same amount. Carcinogenic and non-carcinogenic risks to the population will be reduced by about half.

Spatio-temporal modelling of changes in air pollution exposure associated to the COVID-19 lockdown measures across Europe

The lockdown and related measures implemented by many European countries to stop the spread of the SARS-CoV-2 virus (COVID-19) pandemic have altered the economic activities and road transport in many cities. To rigorously evaluate how these measures have affected air quality in Europe, we developed Bayesian spatio-temporal (BST) models that assess changes in the surface nitrogen dioxide (NO2) and fine particulate matter (PM2.5) concentration across the continent. We fitted BST models to measurements of the two pollutants in 2020 using a lockdown indicator covariate, while accounting for the spatial and temporal correlation present in the data. Since other factors, such as weather conditions, local combustion sources and/or land surface characteristics may contribute to the variation of pollutant concentrations, we proposed two model formulations that allowed the differentiation between the variations in pollutant concentrations due to seasonality from the variations associated to the lockdown policies. The first model compares the changes in 2020, with the ones during the same period in the previous five years, by introducing an offset term, which controls for the long-term average concentrations of each pollutant during 2014–2019. The second approach models only the 2020 data, but adjusts for confounding factors. The results indicated that the latter can better capture the lockdown effect. The measures taken to tackle the virus in Europe reduced the average surface concentrations of NO2 and PM2.5 by 29.5% (95% Bayesian credible interval: 28.1%, 30.9%) and 25.9% (23.6%, 28.1%), respectively. To our knowledge, this research is the first to account for the spatio-temporal correlation present in the monitoring data during the pandemic and to assess how it affects estimation of the lockdown effect while accounting for confounding. The proposed methodology improves our understanding of the effect of COVID-19 lockdown policies on the air pollution burden across the continent.

Controlling Factors of Methane in Tropical Lakes of Different Depths

AbstractTo understand methane (CH4) dynamics in tropical lakes and describe their importance in overall CH4 emissions, we observed temporal trends of CH4 stored in the water columns of Philippine lakes of different depths (shallow, moderately deep, and deep). We detected higher CH4 stored in profundal anoxic layers of deeper lakes. The average surface and profundal CH4 concentrations throughout our monthly monitoring were 0.27 ± 0.07 and 421 ± 189 μmol L–1 in the shallow lake, 0.48 ± 0.37 and 1,121 ± 125 μmol L–1 in the moderately deep lake, and 0.34 ± 0.23 and 943 ± 119 μmol L–1 in the deep lake. The fate of CH4 stored in the water column was related to depth, owing to different stratification and mixing regimes. Analyses of temporal relationships of CH4 with daily weather and physicochemical parameters revealed their impact on CH4 dynamics by controlling the frequency and mixing intensity throughout the year. Only shallow lake exhibited increase in CH4 concentrations with lowering atmospheric pressure. This allows vertical mixing and transport of CH4 from deeper to shallower layers. In moderately deep, and deep lakes, effects of daily weather parameters were not apparent on CH4 concentrations in the deepest layers (below 30 m depth). This suggests that lake depth and stratification should be considered for precise estimation of tropical lakes' CH4 emissions. Comparison with lakes under different climate conditions revealed the importance of tropical lakes for surface CH4 emission due to higher surface CH4 concentrations. Changes in water temperature is one of the factors controlling profundal CH4 production, storage, and its transport to shallower layer.

Change of CO Concentration Due to the COVID-19 Lockdown in China Observed by Surface and Satellite Observations

The nationwide lockdown due to the COVID-19 pandemic in 2020 reduced industrial and human activities in China. In this study, we investigate atmospheric carbon monoxide (CO) concentration changes during the lockdown from observations at the surface and from two satellites (TROPOspheric Monitoring Instrument (TROPOMI) and Infrared Atmospheric Sounding Interferometer (IASI)). It is found that the average CO surface concentration in 2020 was close to that in 2019 before the lockdown, and became 18.7% lower as compared to 2019 during the lockdown. The spatial variation of the change in the CO surface concentration is high, with an 8–27% reduction observed for Beijing, Shanghai, Chengdu, Zhengzhou, and Guangzhou, and almost no change in Wuhan. The TROPOMI and IASI satellite observations show that the CO columns decreased by 2–13% during the lockdown in most regions in China. However in South China, there was an 8.8% increase in the CO columns observed by TROPOMI and a 36.7% increase observed by IASI, which is contrary to the 23% decrease in the surface CO concentration. The enhancement of the CO column in South China is strongly affected by the fire emissions transported from Southeast Asia. This study provides an insight into the impact of COVID-19 on CO concentrations both at the surface and in the columns in China, and it can be extended to evaluate other areas using the same approach.

Effect of Wet Deposition on Secondary Inorganic Aerosols Using an Urban-Scale Air Quality Model

We investigated the effects of wet deposition on secondary inorganic aerosols (SIAs) in urban areas by coupling the wet deposition module with the three-dimensional computational fluid dynamics atmospheric chemistry model (CFD-Chem). We developed a wet deposition model for the microscale model by improving on the global modeling initiative scheme. We evaluated the model by comparing it to the observed washout ratio from the total wet deposition. The simulated washout ratio calculated using the wet scavenging coefficient (WSC) based on the theoretical calculation is six times lower than that observed, suggesting that the wet deposition amount of SIAs from below-cloud scavenging might be underestimated. When we applied the WSC based on field measurements, the washout ratio was much improved; however, it was slightly overestimated compared to the observed rate. Therefore, we estimated the optimal WSC for SIAs in the urban area using a linear regression approach. We conducted a model using the wet deposition of SIAs in a megacity to understand the effects of wet deposition on the SIA concentration using estimated optimal WSCs. The simulated results indicate that washout processes decrease the surface aerosol concentration, showing that reductions in the average surface concentrations from washout processes were from 7.1% to 11.2%. The simulation results suggest that washout processes can reduce the particulate matter concentration in urban areas, indicating that washout processes should be considered in the microscale model, although the modeling domain can only simulate washout processes.

Aircraft landing and takeoff emission impacts on surface O3 and PM2.5 through aerosol direct feedback effects estimated by the coupled WRF-CMAQ model

The aerosol direct feedback effects (ADFEs) are neglected in traditional air quality modeling studies (where meteorology is used as input and not affected by the chemistry and aerosol microphysics) for estimating the impacts of aircraft emissions on air quality. In this study, aircraft landing and take-off (LTO) attributable change of O3 and PM2.5 concentrations through ADFEs for the year 2005 within the contiguous United States (CONUS) are quantified by a coupled meteorology-chemistry modeling system: Weather Research and Forecasting – Community Multi-scale Air Quality (WRF-CMAQ) model. We first quantified the effects of ADFEs of all aerosols within the CONUS (not the effects of aircraft LTO emissions) on surface meteorology and air quality and found that ADFEs changed on average the downward short-wave radiation (SWR), 2-m temperature (T2), planetary boundary layer (PBL) height, O3 and PM2.5 by −7.38 W/m2, −0.47 K, −20.72 m, −0.41 ppb and +0.28 μg/m3 in 2005. We also found a seasonal influence where ADFE-influenced change (decrease) of SWR, T2, PBL, O3 and change (increase) of PM2.5 were higher in summer than in winter. We found that the aircraft LTO emissions’ contribution to domain average surface concentration of O3 and PM2.5 were +0.0065 ppb and +0.0022 μg/m3 respectively when ADFEs are accounted for. The ADFEs decrease aircraft LTO attributable surface O3 and PM2.5 change by 21% and 23% respectively comparing with that without ADFE in 2005. We also found that in both without-and-with ADFE cases, the aircraft LTO emissions increases domain average of O3 from April to October and decreases from November to March showing a strong seasonal pattern. Our modeling study revealed that use of a coupled model with ADFE shows localized changes in air quality by aircraft LTO emissions across the domain which were masked when looking at domain averages for both O3 and PM2.5, and which may be important for accurately quantifying health risk due to air pollution exposures in densely populated areas.

Effect of active mixing on capture efficiency in heterogeneous microfluidic immunosensor

The enhanced capture of the antigen (Ag) by the surface-immobilized antibodies (Ab) in heterogeneous microfluidic immunosensors lowers (improves) the detection limit thus facilitating the early disease detection. The efficient capture of the antigen is subjected to the interaction of the transport parameters, reaction parameters and the microfluidic system geometry. In the present work, the role of active mixing in facilitating the transport in flow-based heterogeneous immunosensor was studied, both numerically and experimentally. The experiments were performed with the capture of prostate-specific antigen (PSA) by anti-PSA and the results were validated using numerical simulations. The average Sherwood number (Sh) for the experiments and simulations was comparable. First, the effect of the nature of the flow on the capture efficiency was tested, which showed the enhancement in the antigen capture using active mixing. Further, studies of individual active mixing parameter (average velocity, frequency and amplitude) on analyte capture were conducted. The increase in average velocity (uavg) increases the antigen capture but the corresponding pressure drop also increases, and the figure of merit (FOM) attains a maximum at Re ~ 0.6. Similar behavior was observed with the increase of the frequency. The continuous increase in the frequency reduces the reaction time scale and decreases the analyte capture. The amplitude has the least effect on the antigen capture. The flow profiles were also seen and the temporal variation was compared at different flow conditions with micro-PIV. We also proposed two correlations utilizing the parameters—the average surface concentration (Cs,avg), the Reynolds number (Re) and the Strouhal number (St). The correlations indicate that the dependency coefficient for St is higher than Re, and signify the impact of vortex propagation (i.e., active mixing) on antigen capture.

Correlations of the capture efficiency with the Dean number and its constituents in heterogeneous microfluidic immunosensors

In heterogeneous microfluidic immunosensors, enhanced capture efficiencies of the antigens (Ag) in the carrier fluids by the surface-immobilized antibodies (Ab) facilitate lower detection limits and thus early detection of disease. Capture efficiency depends on the interplay of transport, reaction parameters and the geometry of the system. A detailed analysis on the enhanced capture efficiencies due to secondary flows in heterogeneous immunosensors has not received significant attention and is the theme of the present work. We conducted a systematic study to observe the significance of secondary forces on the capture efficiency, manifested as the average surface concentration (Cs,avg), in serpentine channels of different lengths (l) and radius of curvature (Rc) as a function of the Reynolds number (Re). Experimental observations were validated with numerical simulations. Micro-PIV studies at different planes and sections of the serpentine microchannels were conducted and matched with the simulated velocity profiles. Further investigation of the process and the geometrical parameters was conducted using numerical simulation and the behaviour of Cs,avg as a function of Re and Rc was plotted for different cases. A highlight of the present work are correlations of Cs,avg as a function of the Dean number (De), as well as its constituents (Re and α). The scientific studies of the geometrical and process parameters which affect the analyte capture advance the understanding of the phenomena and the proposed engineering correlations would be useful in the design of more efficient flow-based heterogeneous immunosensors.

Modelling the effect of aerosol polydispersity on unipolar charging and measurement in low-cost sensors

Low-cost ultrafine aerosol sensors are experimentally calibrated with controlled aerosol sources to provide metrics such as surface area, lung-deposited surface area, mean particle size and/or total concentration from one or more electrical current measurements. However, an aerosol with a large standard deviation in particle size provides a significantly different signal from a monodisperse aerosol with the same median particle size. In this paper, we investigate the effect of particle polydispersity on measurements in devices which employ unipolar charging. The conservation equations are solved for particle/ion charging and transport (convection, diffusion and electrical transport) in laminar, steady-state, incompressible flow. Lognormal particle size distributions are represented by over 102 coupled conservation equations for multiple size bins and discrete charge states and solved numerically for the first time. Modelling results show that integrated electrical current from a polydisperse particle distribution can be represented by a monodisperse distribution characterised by the count mean diameter (d¯; unipolar diffusion charging) or diameter of the average surface (ds¯; photoelectric charging) and total concentration, for a large range of particle distributions and operating conditions offering a convenient simplification for the interpretation of ultrafine particle measurements. The simplification reduces the number of simultaneous conservation equations required, thereby reducing computation time by up to 57 times for a polydisperse particle distribution represented by 16 discrete size bins. The method of analysis is useful to both users and developers of low-cost ultrafine particle sensors to understand the effect of particle polydispersity on measurements.

Evaluation of External Beta Absorbed Dose for Contamination of the Skin

Skin dose is very difficult to measure directly and is usually estimated. The beta dose rate to the skin expressed in terms of average surface concentrations of a radionuclide on the skin gives more reliable estimates for this exposure pathway. However, the data in the literature vary as much as an order of magnitude. In this study, we calculate external beta-ray dose rate for human skin contamination around an isotropic point source of mono-energetic electrons. The beta-ray doses rates were computed by performing analytical integration of a semi-empirical point dose rate function . Evaluation of the model is realized by calculating the dose rate for the contamination of the skin at different depths for samples of air collected around the Research Reactor located at the Atomic Energy Authority (Egypt). Meandering of the plume i.e., low wind condition is taken into consideration. The above mentioned treatment is applied for different meteorological states, namely different thermal stability classes, A,B,C,D and E. The maximum beta absorbed dose for the contamination of the skin is for stability class E for nuclide of Cs137 at depth of 20m from the skin.

Studies on the Climate Effects of Black Carbon Aerosols in China and Their Sensitivity to Particle Size and Optical Parameters

In this paper, based on the principle of Mie scattering, we calculated the optical parameters of BC aerosols at different scales and then applied the new optical parameters to simulate the BC aerosols concentration distribution, radiative forcing, and their climate effects. We also compared the results of optical parameters of BC aerosols with homogeneous scales and analyzed the effect on climate. Compared with the conventional uniform-scheme optical parameterization, the concentrations of the first mode of BC aerosols simulated with the optical parameters that were recalculated based on the particle size are significantly higher, while the concentrations of the other modes and the total of BC aerosols are lower. In the respective of statistics, the changes of column burdens of BC in four modes are 0.085, −0.095, −0.089, −0.054 mg/m2. The clear-sky TRF of BC are weakened in the value of 0.03 W/m2 averaged over the domain, while the all-sky TRF of BC are enhanced of 0.06 W/m2 in general. The warming effect of BC becomes weaker when using the new scheme by −0.04 K to −0.24 K. When using the new optical parameters scheme, the regional average surface concentrations of BC in four modes are 0.372, 0.264, 0.055 and 0.004 μg/m3, respectively. Especially, the first and the second mode account for as large as 53% and 38%. The surface concentration and column burden of total BC are 0.69 μg/m3 and 0.28 mg/m2 can be dropped. The regional average direct RFs of BC at the top of the atmosphere are 0.49 W/m2 under clear-sky and 0.36 W/m2 under all-sky averaged over the domain. Over most areas of central China, North China, and East China, BC may increase the temperature in a range of 0.05∼0.15 K, while over South China, BC shows cooling effect. In average, the precipitation variations caused by BC over East China, North China, South China, and Northeast China are −0.83, −0.05, −0.11, and −0.13 mm/d, respectively. As a whole, the variations of circulation, pressure, and temperature show a good correspondence.

Geochemical soil anomalies: Assessment of risk to human health and implications for environmental monitoring

Areas with natural geochemical anomalies are not normally included when defining geochemical backgrounds for metals. However, it is important to understand the distribution and extent of anomalous geochemical values when assessing the risks associated with metal contamination to the ecosystem. This study measured the concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn in pedogenetic soil horizons with geochemical anomalies. The factors that control the vertical distribution of these elements (pH, organic carbon, cation exchange capacity, lithogenic metals, granulometry) were also examined. Except to Cd and Hg, the average surface concentrations of the metals studied exceeded the expected background levels for the region. The concentrations of Cr, Cu, and Ni were higher in soils developed from basalt, while Cd, Hg, Pb and Zn exhibited concentrations with no direct relation to the type of parent material. All the metals are of natural origin with the exception of Zn, which was influenced by anthropogenic activities in two soil profiles. With an exception of the Cd and Hg contents that were low for all analyzed soils, samples showed geochemical anomalies for all the metals, in particular Cr, Ni, and Pb, with values high enough to warrant investigation due to the possible impairment of soil functions and potential risks to human health. However, when samples were evaluated using sequential extraction analyses, results showed at least 84% of the total content of Cr, Ni e Pb was associated with the residual fraction, indicating a low potential for mobility and availability in the environment. Measures of the hazard quotient and the hazard index showed that adverse impacts on human health are not likely to result from the high concentrations of Cr, Ni, and Pb, even in more sensitive organisms. These results have important implications for the definition of trigger values for investigative or remedial measures in areas with geochemical anomalies.

Heterogenization of a [NiFe] Hydrogenase Mimic through Simple and Efficient Encapsulation into a Mesoporous MOF.

In the quest for new, efficient, and noble-metal-free H2-evolution catalysts, hydrogenase enzymes are a source of inspiration. Here, we describe the development of a new hybrid material based on a structural and functional [NiFe]-hydrogenase model complex (NiFe) incorporated into the Zr-based MOF PCN-777. The bulk NiFe@PCN-777 material was synthesized by simple encapsulation. Characterization by solid-state NMR and IR spectroscopy, SEM-EDX, ICP-OES, and gas adsorption confirmed the inclusion of the guest. FTO-supported thin films of the NiFe@PCN-777 composite were obtained by electrophoretic deposition of the bulk material and characterized by SEM-EDX, ICP-OES, and cyclic voltammetry. The average surface concentration of electroactive NiFe catalyst in the film was found to be ∼9.6 × 10-10 mol cm-2, implying that a surprisingly high fraction (37%) of NiFe units incorporated in the MOF are electroactive. By cyclic voltammetry, we showed that NiFe maintains its electrocatalytic capabilities for H+ reduction inside the MOF cavities, even if under controlled-potential electrolysis conditions the activity of NiFe cannot be discerned from that of free PCN-777 and FTO.

Theory for the chronopotentiometry on rough and finite fractal electrode: Generalized Sand equation

A theoretical model for the galvanostatic chronopotentiometry on a randomly rough electrode is developed for the diffusion controlled mass transport. The proposed model addresses the influence of various morphological characteristics of roughness on the transition time, interfacial concentration and potential transients. The potential transient and transition time of rough electrode is expressed in terms of average interfacial concentration. Expression for the average surface concentration is obtained in terms of the power spectrum of roughness while detailed analysis of simulated chronopotentiograms is performed for the finite fractal model. Power spectrum of finite fractal roughness is characterized through three controlling parameters of roughness, viz. fractal dimension (DH), lower cutoff length scale of fractality (ℓ) and topothesy length (ℓτ), significantly influence the chronopotentiometric response. Theoretical result show that the transition time at a centered random or pitted surface decreases with increase in their roughness. Experimental data on rough Pt electrode corroborate this observation and quantitative agreement over all time scale is achieved after inclusion of correction for the electric double layer and ohmic contributions.

A Study on Voltametric Electro-kinetic Mechanism of Catechol at l-glutamic Acid-Carbon Paste Sensor

Quinones and quinoles, the pervasive components of living organism, perform different biochemical and physiological activities. These compounds have found their widespread applications as life saving drugs in cancer chemotherapy, antioxidant, anti bacterial and antifungal agents. These contribute as components of biological electron transfer chains located indifferent body parts. Electrochemical redox behavior of catechol using cyclic and differential pulse voltammetry at the surface of ℓ-glutamic acid modified carbon paste sensor was observed quite sensitive. There was a remarkable increase in the magnitude of both peak currents of catechol at the surface of modified electrode as compared to that of bare carbon paste electrode. Optimizations of working parameters for both techniques have been performed to perk up the working efficiency during experimentation. The electrochemical process occurs under both the diffusion and adsorption controlled conditions. The kinetic parameters such as heterogeneous electron transfer rate constant for electrode process (K<sub>h</sub>), diffusion coefficient (D), standard rate constant of surface reaction (k°), electron transfer coefficient (α) and the average surface concentrations of electro-active species (χ<sub>1</sub>&χ<sub>2</sub>) at the electro-chemical barriers catechol/o-quinone radical and o-quinone radical/o-quinone were calculated. The calculated value of K<sub>h</sub> lie in close vicinity to limiting value of a complete irreversible process and in far range of quasi-reversible process. In the higher range of applied scan rates at lower potentials of the used potential window, the forward scan revealed the formation of well stable reaction intermediate, at relatively slower rate. This is the rate determining step of the oxidation process but in case of reduction pulse of the same scan rate, there is no indication of any reduction intermediate moieties. The chemical process during electrochemical oxidation of catechol follows pseudo first order kinetics. Furthermore, a two step oxidation, Electronic-Chemical-Electronic-Chemical reactions (ECEC) mechanism has been proposed and single step reduction has been observed for the coupled redox process at the sensor/analyte interface.

Influence of Rotational Moulding Process Parameters on Accuracy of Polymer Casts

The present paper describes the experimental tests undertaken to examine the influence of rotational speeds of two axes of the mould on properties of casts produced in the rotational moulding process. The general principles of this polymer processing technology have been described. The main applications have been introduced, and leading advantages and typical disadvantages of rotational moulding process have been told over. Rotational mould's speed around axes was changed, and a thickness of cast walls has been measured also with average surface concentration of colorant in cast walls. Laboratory test stand, processing properties of polymer, also test program and experimental test methodology have been described.

Evaluation of a Reduced Graphene Oxide Antimony Nanocomposite Horseradish Peroxidase Biosensor Matrix for Hydrogen Peroxide

An exploration of reduced graphene oxide impregnated with antimony nanoparticles to form a nanocomposite as a platform for the immobilization of horseradish peroxidase for the amperometric detection of hydrogen peroxide is presented. Electrochemical measurements revealed that the heterogeneous electron transfer constant (ks) was evaluated to be 0.37 s−1. The average surface concentration of electro-active HRP on the surface of the modified glassy carbon electrode was calculated to be 9.43 × 10−9 mol cm−2. The voltammetric results revealed that the peak current of the modified electrode increased linearly with increasing concentration of hydrogen peroxide (from 1nM to 4nM) with a detection limit of 2.88nM.