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The increase in evidence on the adverse health effects of air pollution has been possible thanks to the advances in technology for air pollution monitoring and personal exposure. In this context, air quality sensors present a huge potential for enhancing long-term personal exposure prediction. In order to prove the potential of air sensors for health research, a pilot study with patients suffering from chronic obstructive pulmonary diseases or Asthma was carried out in Stuttgart (Germany) in cooperation with the University Hospital Charité in Berlin, and an outpatient pulmonary practice in Stuttgart.Prior to the pilot study, we first tested several sensor models for PM and NO2 in the laboratory as well as in the field. The sensors with the best performance were selected to build two different sensor boxes for indoor and outdoor measurements. Temperature and relative humidity sensors were also included in the boxes. To avoid the overestimation of the PM readings due to hygroscopic growth, a low-cost dryer was designed and evaluated for the PM sensor of the outdoor boxes (Chacón-Mateos et al. 2022).The measurements inside and outside the houses were carried out over 30 days. Passive sampling of NO2 was done additionally for quality assurance of the NO2 measurements. Participants completed spirometry, a questionnaire assessing respiratory symptoms, and a protocol of activities on a daily basis. The calibration and validation of the sensors were conducted two weeks before the start of the measurements. To perform the quality assurance, the sensor boxes for indoors were collocated in the laboratory, and the sensor boxes for outdoors in the field, together with reference-grade instruments. The PM2.5 concentrations were corrected using univariate linear regression whereas multilinear regression and machine learning algorithms were tested and applied to correct the raw data of the NO2 sensors.The sensor validations have shown that measuring low concentrations of PM2.5 and NO2 has higher expanded uncertainty, but high concentrations can be measured with expanded uncertainties that fulfill the Data Quality Objectives (DQO) set by the Air Quality Directives for indicative measurements. However, we also found a high unit-to-unit variability which means that model coefficients cannot be transferred from one sensor to another. We also recommend collocating NO2 passive samples close to the sensor boxes to determine whether or not the sensor is measuring within the expected range as the signal of some NO2 sensors drifted unexpectedly during the measurements in the houses of the patients.In conclusion, air sensors are not yet to be recommended to quantify the effects of low-level air pollution but they are a promising tool to increase the ubiquity of epidemiological studies for low- and middle-income countries where high air pollution is expected. Moreover, it is important to consider that in order to get actionable data with air sensors, a significant amount of time in sensor calibration should be invested.References:Chacón-Mateos, M., Laquai, B., Vogt, U., and Stubenrauch, C.: Evaluation of a low-cost dryer for a low-cost optical particle counter, Atmos. Meas. Tech., 15, 7395–7410, https://doi.org/10.5194/amt-15-7395-2022, 2022

Air pollution in urban areas is a huge concern that demands an efficient air quality control to ensure health quality standards. The hotspots can be located by increasing spatial distribution of ambient air quality monitoring for which the low-cost sensors can be used. However, it is well-known that many factors influence their results. For low-cost Particulate Matter (PM) sensors, high relative humidity can have a significant impact on data quality. In order to eliminate or reduce the impact of high relative humidity on the results obtained from low-cost PM sensors, a low-cost dryer was developed and its effectiveness was investigated. For this purpose, a test chamber was designed, and low-cost PM sensors as well as professional reference devices were installed. A vaporizer regulated the humid conditions in the test chamber. The low-cost dryer heated the sample air with a manually adjustable intensity depending on the voltage. Different voltages were tested to find the optimum one with least energy consumption and maximum drying efficiency. The low-cost PM sensors with and without the low-cost dryer were compared. The experimental results verified that using the low-cost dryer reduced the influence of relative humidity on the low-cost PM sensor results., Bundesministerium für Bildung und Forschung

The use of low-cost sensors for air quality measurements has become very popular in the last few decades. Due to the detrimental effects of particulate matter (PM) on human health, PM sensors like photometers and optical particle counters (OPCs) are widespread and have been widely investigated. The negative effects of high relative humidity (RH) and fog events in the mass concentration readings of these types of sensors are well documented. In the literature, different solutions to these problems – like correction models based on the Köhler theory or machine learning algorithms – have been applied. In this work, an air pre-conditioning method based on a low-cost thermal dryer for a low-cost OPC is presented. This study was done in two parts. The first part of the study was conducted in the laboratory to test the low-cost dryer under two different scenarios. In one scenario, the drying efficiency of the low-cost dryer was investigated in the presence of fog. In the second scenario, experiments with hygroscopic aerosols were done to determine to which extent the low-cost dryer reverts the growth of hygroscopic particles. In the second part of the study, the PM10 and PM2.5 mass concentrations of an OPC with dryer were compared with the gravimetric measurements and a continuous federal equivalent method (FEM) instrument in the field. The feasibility of using univariate linear regression (ULR) to correct the PM data of an OPC with dryer during field measurement was also evaluated. Finally, comparison measurements between an OPC with dryer, an OPC without dryer, and a FEM instrument during a real fog event are also presented. The laboratory results show that the sensor with the low-cost dryer at its inlet measured an average of 64 % and 59 % less PM2.5 concentration compared with a sensor without the low-cost dryer during the experiments with fog and with hygroscopic particles, respectively. The outcomes of the PM2.5 concentrations of the low-cost sensor with dryer in laboratory conditions reveal, however, an excess of heating compared with the FEM instrument. This excess of heating is also demonstrated in a more in-depth study on the temperature profile inside the dryer. The correction of the PM10 concentrations of the sensor with dryer during field measurements by using ULR showed a reduction of the maximum absolute error (MAE) from 4.3 µg m−3 (raw data) to 2.4 µg m−3 (after correction). The results for PM2.5 make evident an increase in the MAE after correction: from 1.9 µg m−3 in the raw data to 3.2 µg m−3. In light of these results, a low-cost thermal dryer could be a cost-effective add-on that could revert the effect of the hygroscopic growth and the fog in the PM readings. However, special care is needed when designing a low-cost dryer for a PM sensor to produce FEM similar PM readings, as high temperatures may irreversibly change the sampled air by evaporating the most volatile particulate species and thus deliver underestimated PM readings. New versions of a low-cost dryer aiming at FEM measurements should focus on maintaining the RH at the sensor inlet at 50 % and avoid reaching temperatures higher than 40 ∘C in the drying system. Finally, we believe that low-cost dryers have a very promising future for the application of sensors in citizen science, sensor networks for supplemental monitoring, and epidemiological studies.

Wood combustion is a major part of the current efforts to reduce CO2 emissions. However, wood combustion leads to emissions of other pollutants like fine particulate matter. A new option to reduce particulate matter emissions is a metal mesh filter with counter current flushing. An automatic prototype was tested under realistic conditions including starts and stops of the boiler. For regeneration, the filter was flushed using water in opposite flow direction. The water was recycled multiple times to limit water consumption. The results are very promising. Regeneration was successful and no signs of decay could be observed over 419.5 h of operation and 234 regenerations. The filter can be operated during all phases of boiler operation, which is a major step forward compared to alternative secondary measures. Separation efficiency was high with 80–86%, even though the filter showed internal leakage, which reduced the separation efficiency. Additionally, waste products were examined. About 1000 l wastewater can be expected to be produced every month, which could be disposed using the communal waste water system, given the low heavy metal loading. A part of the fine particulate matter is unsoluble and has to be removed from the regeneration water before reuse. The unsoluble fraction contains the majority of heavy metals and has to be disposed as fly ash or used for urban mining. Generally spoken, the metal mesh filter is a new, promising option which can overcome limitations of current secondary measures without increasing costs given its simple and robust construction.

Phase pure Na-β''-alumina ceramics are excellent electrolytes for molten-salt and all-solid-state batteries. However, controlled processing of this complex material is required to obtain the desired phase content, as Na-β''-alumina can accommodate variable amounts of sodium within its conduction slab. On the one hand, addition of dopant ions (e.g. Li+, Mg2+) influences stability and sodium content of Na-β''-alumina. On the other hand, β''-aluminas are prone to sodium evaporation, resulting in compositional changes during high-temperature sintering. Here, we show that while sodium evaporation indeed becomes significant at temperatures > 1300 °C, Na-β''-alumina ceramics of constant total composition can be prepared at strongly variable sintering conditions by applying an encapsulation. Nevertheless, our study reveals that the sodium content in the Na-β''-alumina crystal structure varies with the processing temperature. This is indicated by changes in the c-lattice parameter, which decreases with increasing sintering temperature, corresponding to an increase in sodium content.

In aerosol science, there is an increasing interest to perform mobile measurements to obtain number size distribution of ultrafine particles (UFP), using portable instruments based on unipolar charging and size segregation by electrical particle mobility. Applications of such measurements range from ambient and indoor aerosol studies to source identification in work environments. However, knowledge on the actual measurement uncertainties of these portable instruments under various conditions has been limited. This investigation presents results from an intercomparison workshop conducted at the World Calibration Center for Aerosol Physics (WCCAP) in Leipzig, Germany, in January 2020. Manufacturers and users were invited to have their portable instruments tested and compared against reference instrumentation for particle number size distributions (PNSD) and total particle number concentration (PNC). In particular, the performances and uncertainties of the NanoScan SMPS (Scanning Mobility Particle Sizer) Model 3910 (TSI Inc.) and the Mini Wide Range Aerosol Spectrometer (WRAS) Model 1371 (Grimm Aerosol Technik) were investigated extensively against the WCCAP Mobility Particle Size Spectrometers (MPSS) and Condensation Particle Counters (CPC). A total of 11 TSI NanoScan SMPS and 4 GRIMM Mini WRAS instruments were characterized for ambient aerosols as well as lab-generated aerosols. The workshop results affirm that the portable instruments must be serviced and calibrated annually or prior field studies to provide measurements within the given uncertainties. It should be noted that users should carry out timely service, maintenance and calibration of portable instruments at their facilities. During initial inspection, non-serviced NanoScan SMPS instruments overestimated a dominant ultrafine aerosol mode by 120 % at around 80 nm. Maintenance and servicing improved the performance. Overall, the performance of NanoScan SMPS instruments improved for the ultrafine aerosol mode while the PNC in the fine aerosol mode still overestimated by up to 80 %. The latter effect seems to be systematically related to the unipolar charging of particles, and the reduced sensitivity of electrical particle mobility with increasing particle size above 200 nm. Due to shift in the second mode of bimodal distribution, particles are overcounted around 100 nm. With regard to the integral PNC, some of the NanoScan SMPS found to be in good agreement (i.e. within 20 %) compared to the reference CPC. In addition, a reasonably good unit-to-unit agreement within ±20 % was found for NanoScan SMPS instruments. The Mini WRAS instruments, after proper cleaning and servicing, provided improved results within ±15 % deviation in PNC in the ultrafine aerosol mode. Overall, most of the GRIMM Mini WRAS instruments (operating with software version 10.0) agrees well with PNC (i.e. 10–50 %) when the ultrafine mode was dominant. Conversely, PNC of the fine aerosol mode was systematically underestimated by 60 % above 100 nm. Except for one instrument, the integral PNC of the GRIMM Mini WRAS spectrometers were within an uncertainty range of ±20 % compared to the reference CPC. Additionally, it is important for users to note that the Mini WRAS performed significantly better when using software version 10.0 compared to version 8.2. The workshop results suggest that despite the above-mentioned uncertainties, these portable instruments are suited for mobile ultrafine particle measurements to detect relative differences in the PNSD such as source apportionment studies of ultrafine particles at work places or outdoors near sources.

Das Ziel der vorgestellten Studie bestand darin, Konzentrationen von Stickstoffdioxid (NO2), Partikeln (PM10 und PM2,5) und Black Carbon (BC) entlang eines ausgewählten Abschnittes der stark befahrenen Bundesstraße B14 zu untersuchen, die durch das Stadtgebiet von Stuttgart verläuft. Dafür wurde die Verteilung verschiedener luftverunreinigender Komponenten sowohl zeitlich als auch räumlich hochaufgelöst erfasst. Sie wurden in einer ersten Messkampagne von April bis Juni 2014, in einer zweiten Messkampagne von Mitte März bis Ende April 2015 und in einer dritten Messkampagne im Februar 2017 mithilfe mobiler Messungen entlang einer festen, für Radfahrer zugänglichen Messroute gemessen. Ergänzt wurden die mobilen Messungen durch NO2– und NOX-Passivsammlermessungen an ausgewählten Messstandorten. Die NO2– und Feinstaub-Konzentrationen werden stark von den Emissionen des Straßenverkehrs beeinflusst. Die Abnahme der Schadstoffkonzentrationen mit zunehmendem Abstand zur Bundesstraße konnte durch Vergleichsmessungen in einem Park quantifiziert werden. Es wurden zusätzlich Vertikalprofile für Stickstoffoxide (NOX, NO, NO2) sowohl kontinuierlich mit Chemilumineszenz-Messgeräten als auch mit Passivsammlern in verschieden Höhen gemessen, um die Abnahme der NO2-Konzentration mit der Höhe zu untersuchen.

The stability of the atmosphere plays a major role in the dispersion of pollutants. The meteorological conditions favoring a high-pressure situation resulting in the formation of inversion layer inhibits pollutant dispersion. The aim of the study was to obtain vertical profiles of meteorological parameters and air pollutants in order to investigate the impact of inversion on the air quality of this city. Vertical profiles help to understand the behaviour of temperature inversion, pollutants and their relationship to each other. The tethered balloon was equipped with in-situ instruments to measure Particulate Matter (PM), Black Carbon (BC), Ultra Fine Particles (UFP) as well as meteorological parameters such as air temperature, relative humidity, wind speed and wind direction of the lower troposphere. The measurements were carried out in “Schlossgarten”, a park area near the city center of Stuttgart. Vertical profiles were obtained by ascending the balloon from ground up to a height of a maximum of 470 m and then descending it back to the ground. One complete sounding (ascent and descent) took around 30–40 min. The measurement campaign took place on 8th and July 9, 2018. 43 soundings were performed during that period. During the measurement campaign, a distinct inversion was observed at nighttime, which trapped the pollutants, hence increasing the pollutant concentration near the ground within the inversion layer. PM, UFP and BC concentrations showed a decreasing trend with increasing altitude but during noon, when the atmosphere was well mixed, the concentrations were relatively constant along with increasing altitude.

This work is an overview of the multi-modal hard X-ray nanoprobe beamline at the MAX IV Laboratory. The beamline provides an intense and coherent beam, focused to 40–200 nm in the energy range 5–28 eV., NanoMAX is the first hard X-ray nanoprobe beamline at the MAX IV laboratory. It utilizes the unique properties of the world’s first operational multi-bend achromat storage ring to provide an intense and coherent focused beam for experiments with several methods. In this paper we present the beamline optics design in detail, show the performance figures, and give an overview of the surrounding infrastructure and the operational diffraction endstation.

To cope with weather and climate-induced impacts as well as with air pollution in cities, the German research programme “Urban Climate Under Change” ([UC]2) aims at developing, testing and validating a new urban climate model, which is able to cover the full range of temporal and spatial scales of urban atmospheric processes. The project “Three-dimensional Observation of Atmospheric Processes in Cities” (3DO), which forms the module B of the [UC]2 research programme, aims at acquisition of comprehensive, accurate three-dimensional observational data sets on weather, climate and air quality in the German cities of Berlin, Hamburg and Stuttgart. Data sets from long-term observations and intense observation periods allow for evaluation of the performance of a new urban climate model called PALM‑4U that is developed by the project “Model-based city planning and application in climate change” (MOSAIK), which forms the module A of the [UC]2 research programme. This article focuses on collaborative activities for compilation of existing and acquisition of new observational data within the 3DO project.

Na-β″-alumina ceramics are archetypical ion conductors with excellent sodium-ion conductivity. Their processing is, however, challenging and results in large variations in reported conductivity mea...

Zur Wahrung der Grundsätze guter Unternehmensführung decken Corporate-Governance-Systeme heute vielseitige Funktionen ab: ob zur Sicherung rechtlich einwandfreier Unternehmensentscheidungen, bei der Vertretung von Stakeholder-Interessen oder im Umgang mit betrieblichen und finanziellen Risiken. Bislang jedoch arbeiten die in einzelnen Verantwortungsbereichen eingesetzten Teilsysteme meist streng voneinander getrennt. Erfolgversprechende Ansätze für ein integriertes Governance-System stellt Ihnen das Expertenteam um Jens C. Laue jetzt erstmals aus konsequent unternehmenspraktischer Perspektive vor.

Air pollution due to Particulate Matter (PM) is an increasing concern of global extent. It has been the focus of many research projects worldwide and the latest low-cost technology is offering an ease and cheap way to monitor PM concentration. In this research, a low-cost PM monitoring platform was built with the objectives of evaluating its feasibility and its performance in mobile measurements, as well as characterizing the concentration profiles of PM along the measurement route. The rack railway in Stuttgart was utilized as means of transportation for this low-cost monitoring system with which the temporal and spatial distribution of the PM10, PM2.5 and PM1 concentration along the route was attained. The measurements were conducted for around two months from mid of January until mid of March 2019, during the operation hours of the rack railway. The results showed that the PM concentrations were dominated by fine particulate matter (PM2.5 and PM1) along the route of the rack railway. Higher PM concentrations were measured near the federal highway and high traffic area as compared to the residential area. An overestimation of PM concentration using low-cost sensor platform was observed during high relative humidity conditions as compared to the professional aerosol spectrometers., Bundesministerium für Bildung und Forschung

X-ray zone plates made from gold are common optical components used in X-ray imaging experiments. These nanostructures are normally fabricated using a combination of electron-beam lithography and gold electroplating with cyanide gold baths. In this study, we present a gold electroplating process in a miniaturized gold-suplphite bath. The miniaturization is enabled by on-chip reference plating areas with well defined sizes, offering a reliable way to control the height of the structures by carefully choosing the plating time at a given current density in accordance with a calibration curve. Fabricated gold zone plates were successfully used in X-ray imaging experiments with synchrotron radiation. Although gold electroplating of nanostructures is a well-established method, details about the actual process are often missing in the literature. Therefore, we think that our detailed descriptions and explanations will be helpful for other researchers that would like to fabricate similar structures.

Using low-cost gas sensors for air quality monitoring promises cost effective and convenient measurement systems. Nevertheless, the results obtained have a questionable quality due to different factors that can affect sensor performance. The most discussed ones are relative humidity and air temperature. This investigation aimed to assess the behavior of B4-series low-cost gas sensors from Alphasense for measuring CO, NO, NO2, and O3 for different levels of relative humidity and temperature. These low-cost gas sensors were tested for six relative humidity levels from 10% to 85% with increasing steps of 15% and four temperature levels of 10 &deg, C, 25 &deg, C, 35 &deg, C, and 45 &deg, C against reference instruments in the laboratory. The effect of these parameters on low-cost gas sensors was quantified in laboratory from which a correction algorithm was calculated, which was then applied to the field data. The applied algorithm improved the data quality of the low-cost gas sensors in most of the cases. Additionally, a low-cost dryer was assessed to reduce the influence of these factors on the low-cost gas sensors, which also proved to be suitable to enhance the data quality.

The NanoMAX hard X-ray nanoprobe is the first beamline to take full advantage of the diffraction-limited storage ring at the MAX IV synchrotron and delivers a high coherent photon flux for applications in diffraction and imaging. Here, we characterize its coherent and focused beam using ptychographic analysis. We derive beam profiles in the energy range 6-22 keV and estimate the coherent flux based on a probe mode decomposition approach.

Particulate matter emissions are a key issue of modern biomass boilers. A novel gas cleaning method using a metal mesh filter combined with water-based cleaning was developed and tested. The filter was tested batch-wise. Flue gas of a commercial 50-kW boiler was filtered until a pressure drop of 2000 Pa was reached. Afterwards, the filter was regenerated. The initial prototype used ultrasound in order to remove the filter cake from the filter candles. Regeneration was complete and, even after boiler malfunctions producing tar, the filter cake could still be removed. Given the good results, a second cleaning mode, flushing the filter candles with water, was tested. The results were as good as with ultrasonic cleaning. Peak mass collection efficiency was very high with 98 ± 2% (burning wood pellets). However, directly after cleaning, the first layer of filter cake has to be developed. In this initial phase, collection efficiency is low. Service time until maximum pressure drop was reached depended on the gas velocity. Using pellets as fuel, at a gas velocity of 66.6 m/h, 12-h service time was reached and 4.1 g dust was collected per square meter filter surface, while at 33.3 m/h, service time increased to 55 h and collected dust to 13.9 g/m2. Using low-quality wood chips, the raw gas dust loading was much higher but also the maximum loading of the filter was higher with 13.3 to 28.9 g dust separated per square meter. Still, the service time decreased to 3.4 respective 38 h. Peak collection efficiency increased to 99.5 ± 0.8%. The overall collection efficiency including the buildup of the filter cake depends on the gas velocity and fuel. It ranges from 74 ± 4 to 91 ± 1%. The feasibility of the filter concept could be proven, and further development towards a commercial application is in progress. Metal mesh filters with countercurrent cleaning showed a high potential given their simple and robust design, as well as high collection efficiency., Fachagentur Nachwachsende Rohstoffe, Projekt DEAL

The objective of this work is to determine the nitrogen oxide emission in the flue gas of a catalytic hydrogen combustion process, operating without premixed hydrogen and air supply. The study was investigated on a novel designed gas under glass stove top burner, suitable for domestic kitchen applications. The basic catalytic burner assembly consists of two platinum coated silicon carbide (SiC) foam disks with a diameter of 150 mm, a thickness of 10 mm and a porosity of 60 and 80 pores per inch (ppi) respectively. The two catalytic SiC disks are stacked with 10 mm space between for a uniform air feeding and distribution. Hydrogen is supplied from below the assembly and air is blown in between the two Pt coated catalytic SiC disks, leading to a homogeneous air distribution and thus a uniform catalytic reaction of hydrogen and air. Tests are performed at hydrogen flow rates of 5, 10 and 15 Nl/min, equivalent to 0.9, 1.8, 2.7 kW power, the hydrogen to oxygen ratios (φ) were fixed to 0.66, 0.5 and 0.33 respectively. Ultra-low nitrogen oxide emissions of 0.09 ppmv to 9.49 ppmv, equivalent to 0.007 to 0.37 mg/kWh are achieved with this novel developed catalytic combustion design. These values are significantly lower than the present EU regulation of 56 mg/kWh for combustion processes of gaseous fuels for heating applications. This result shows the very high potential of converting hydrogen to heat without harmful exhaust gases for a broad domestic application in decarbonised gas grids or stationary power to gas applications.

Hydrogen produced by water electrolysis with renewable electricity is a reliable, affordable and environmental friendly energy carrier for future energy supply and storage. Alkaline water electrolysis is a well matured technique and proved to be suitable for large-scale applications. Materials development for alkaline water electrolyzers is still of interest for academia and industry to address the issues of low compatibility to renewable power sources. A lab-scale system for alkaline water electrolysis was developed, aiming to advance materials development and to bridge the intrinsic properties of materials with their performance under realistic operating conditions. As the smallest pressure-type electrolyzer, it is capable of working at 30 bar and 80 °C with continuous liquid electrolyte circulation. Experimental studies investigate the influence of temperature, pressure, and intrinsic properties of materials on voltage efficiency and hydrogen purity. With appropriate analysis, links between material sp...

As for many ion conductors, the electrical conductivity of polycrystalline Na- β ″-alumina reported in literature varies by over two decades at a given temperature. This is often ascribed to a combination of variable effects related to grain size, composition, phase content, porosity and impurities, but the dominating factors are rarely identified. Based on an extensive set of Li2O-stabilized Na- β ”-alumina ceramics sintered at different conditions, we evaluate a sample series with constant composition and phase content but variable conductivity. The total conductivity of the polycrystalline samples features pronounced non-Arrhenius temperature dependence. To explain this effect, we present a simple microstructural model describing the influence of grain size effects in Arrhenius-type ion conductors with highly resistive grain boundaries as a second phase. We show that this model further predicts a linear relationship between conductivity and effective activation energy at a given temperature, which we also observe experimentally. Based on this, we are able to identify to which extent conductivity variations in a given data set may be explained by grain size effects only. As the same microstructural model relates fundamental transport properties of the corresponding grain and grain boundary phases with the experimentally observed linear relationship, we further discuss how these parameters can be extracted, e.g. by taking into account experimentally determined grain size data. Comparison with literature data indicates for which Na- β ″-alumina samples additional effects such as changes in composition and percolation of coarse grains are relevant for the transport properties. Our findings on the relation between effective conductivity and corresponding activation energy are applicable to Arrhenius-type ion conductors with highly resistive grain boundary phases in general.

Over the last decade, manufacturers have come forth with cost-effective sensors for measuring ambient and indoor particulate matter concentration. What these sensors make up for in cost efficiency, they lack in reliability of the measured data due to their sensitivities to temperature and relative humidity. These weaknesses are especially evident when it comes to portable or mobile measurement setups. In recent years many studies have been conducted to assess the possibilities and limitations of these sensors, however mostly restricted to stationary measurements. This study reviews the published literature until 2020 on cost-effective sensors, summarizes the recommendations of experts in the field based on their experiences, and outlines the quantile-mapping methodology to calibrate low-cost sensors in mobile applications. Compared to the commonly used linear regression method, quantile mapping retains the spatial characteristics of the measurements, although a common correction factor cannot be determined. We conclude that quantile mapping can be a useful calibration methodology for mobile measurements given a well-elaborated measurement plan assures providing the necessary data., Bundesministerium für Bildung und Forschung, Umweltbundesamt

Microporous, highly charged and cation exchangeable clays are interesting carriers not only for various functional molecules such as cationic dyes, surfactants, proteins, drugs and complexes, but also for water insoluble molecules. In water, swellable nanohectorite derivatives (“laponites”) with dimensions of about 25 nm in diameter and 1 nm in height delaminate to form individual nanoparticles, which proved to be very useful for applications in aqueous dispersions, but less advantageous for the use in filter systems for water treatment, membrane technology, or as catalysts. To immobilize the particles in aqueous environments and still provide accessibility and high cation exchange rates on the clays, we used an inversion process to prepare porous nanoclay polysulfone composites with high clay contents up to 60%. Successful incorporation of the clays in the matrix required clay pre-modifications with reactive silanes such as octyltriethoxysilane or octadecyltriethoxysilane. Interestingly, unmodified laponite can also be used as a template to form a porous polysulfone network due to its leakage in the inversion process. The high accessibility and activity found in composites prepared with a mixture of unmodified and modified laponite particles pave the way for further modifications with functional molecules for various applications. In this study, we characterize the nanoclay polysulfone composites via scanning electron microscopy, nitrogen gas adsorption of the dried composite, and we determine the cation exchange capacity in the wetted state.

Zone-plate-based soft x-ray microscopes operating in the water window allow high-resolution and high-contrast imaging of intact cells in their near-native state. Laboratory-source-based x-ray micro ...

Cities often have a problem regarding the air quality because various emissions are produced within these cities and local emission sources among others relate directly to the air quality. As an addition to stationary monitoring stations, mobile measurements can provide valuable information regarding spatial distribution of pollutants. In this research, a case study is presented to illustrate the design and implementation of mobile measurement platform with a bicycle. Different compact measuring devices were selected and installed on the bicycle for mobile measurements along a designated route in Stuttgart, Germany. The measured pollutants included Particulate Matter (PM), Ultrafine Particles (UFP), Black Carbon (BC), nitrogen oxides (NO, NO2 and NOX) and ozone (O3). Meteorological parameters such as air temperature, relative humidity, wind speed, wind direction, solar radiation and air pressure were also measured. These measured parameters were allocated to the location using a GPS device. The measurements were carried out during February 2018. The measurement route covered part of the city center with high traffic roads as well as side roads and a park. The results show a very high spatial variability and the pollutant concentration was influenced by different factors such as local traffic, measurement location, meteorological conditions, etc. For NO, NO2 and UFP, the concentrations in the park (which can be considered as urban background level) were only around 30%–50% of the measured concentrations directly on the roadside. For PM10, the differences between the concentrations on the road and in urban background were less pronounced but still clearly measurable. The mobile measurement platform with the bicycle provided an opportunity to have a spatial distribution of a larger study area and proved to be highly adaptive and flexible method.

Thermochemical splitting of CO2 via a ceria-based redox cycle was performed in a solar-driven thermogravimetric analyzer. Overall reaction rates, including heat and mass transport, were determined under concentrated irradiation mimicking realistic operation of solar reactors. Reticulated porous ceramic (RPC) structures and fibers made of undoped and Zr4+-doped CeO2, were endothermally reduced under radiative fluxes of 1280 suns in the temperature range 1200–1950 K and subsequently re-oxidized with CO2 at 950–1400 K. Rapid and uniform heating was observed for 8 ppi ceria RPC with mm-sized porosity due to its low optical thickness and volumetric radiative absorption, while ceria fibers with μm-sized porosity performed poorly due to its opacity to incident irradiation. The 10 ppi RPC exhibited higher fuel yield because of its higher sample density. Zr4+-doped ceria showed increasing reduction extents with dopant concentration but decreasing specific CO yield due to unfavorable oxidation thermodynamics and slower kinetics., AIChE Journal, 63 (4), ISSN:1547-5905, ISSN:0001-1541

Structural changes in an equimolar ceria–zirconia solid solution were determined from room temperature to 1773 K under typical reducing and oxidizing conditions in a reactor for the solar thermochemical dissociation of water or carbon dioxide in a two-step redox cycle. We report the first in situ X-ray absorption spectroscopy (XAS) measurements at both the Ce K and Zr K edges under the conditions of thermochemical carbon dioxide splitting and a temperature swing of 1773 to 1073 K and isothermal conditions at 1773 K. The shift in the Ce K absorption edge reveals quantitative information about changes in the electronic structure of cerium. The maximum extent of reduction at 1773 K was 53% ± 5%; about 9% ± 5% of the cerium atoms changed valence from 4+ to 3+ and vice versa during isothermal looping in a flow of argon and carbon dioxide, respectively. Zr K edge XANES indicated a transformation of the oxygen coordination of zirconia to a more centrosymmetric cubic geometry upon reduction. During isothermal cyc...

A hydrogen based cooking stove was developed and tested in respect to efficiency, functionality and hydrogen safety. Therefore the developed novel combustion unit technology is based on the catalytic oxidation of hydrogen on a platinum coated highly porous reticulated silicon carbide foam ceramics. Compared to other works [1], premixing of hydrogen and air is avoided, thus providing the basis for safe and reliable operation. With this catalytic combustion technology, no initial hydrogen ignition is required, implying a high application security. Separate air and hydrogen supplies make regulation of temperature and power efficient, simple and save. Catalytic hydrogen oxidation is performed already at room temperature; whereby at high hydrogen load, a small hydrogen slip is detected under cold start conditions, nevertheless in operation this becomes negligible. In order to overcome this issue, a hydrogen flow regulation, based on the hydrogen combustion temperature, was introduced. A heat exchanger is integrated into the exhaust line, in order to recover heat for the incoming air, required for the catalytic combustion. This leads to a stove efficiency of up to 80%, measured according to the DIN EN 30-2-1: 2005–08 test standard and greatly exceeds the postulated standard minimum efficiency of 35%. For comfortable and save use, the combustion unit is mounted under a glass ceramic coverage, as common for conventional electrical stoves.