Journal articles on the topic 'Microscale atmospheric dispersion'
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1
Folch, Arnau, Jordi Barcons, Tomofumi Kozono, and Antonio Costa. "High-resolution modelling of atmospheric dispersion of dense gas using TWODEE-2.1: application to the 1986 Lake Nyos limnic eruption." Natural Hazards and Earth System Sciences 17, no. 6 (June 13, 2017): 861–79. http://dx.doi.org/10.5194/nhess-17-861-2017.
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Abstract. Atmospheric dispersal of a gas denser than air can threat the environment and surrounding communities if the terrain and meteorological conditions favour its accumulation in topographic depressions, thereby reaching toxic concentration levels. Numerical modelling of atmospheric gas dispersion constitutes a useful tool for gas hazard assessment studies, essential for planning risk mitigation actions. In complex terrains, microscale winds and local orographic features can have a strong influence on the gas cloud behaviour, potentially leading to inaccurate results if not captured by coarser-scale modelling. We introduce a methodology for microscale wind field characterisation based on transfer functions that couple a mesoscale numerical weather prediction model with a microscale computational fluid dynamics (CFD) model for the atmospheric boundary layer. The resulting time-dependent high-resolution microscale wind field is used as input for a shallow-layer gas dispersal model (TWODEE-2.1) to simulate the time evolution of CO2 gas concentration at different heights above the terrain. The strategy is applied to review simulations of the 1986 Lake Nyos event in Cameroon, where a huge CO2 cloud released by a limnic eruption spread downslopes from the lake, suffocating thousands of people and animals across the Nyos and adjacent secondary valleys. Besides several new features introduced in the new version of the gas dispersal code (TWODEE-2.1), we have also implemented a novel impact criterion based on the percentage of human fatalities depending on CO2 concentration and exposure time. New model results are quantitatively validated using the reported percentage of fatalities at several locations. The comparison with previous simulations that assumed coarser-scale steady winds and topography illustrates the importance of high-resolution modelling in complex terrains.
2
Lin, Dongqi, Basit Khan, Marwan Katurji, Leroy Bird, Ricardo Faria, and Laura E. Revell. "WRF4PALM v1.0: a mesoscale dynamical driver for the microscale PALM model system 6.0." Geoscientific Model Development 14, no. 5 (May 6, 2021): 2503–24. http://dx.doi.org/10.5194/gmd-14-2503-2021.
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Abstract. A set of Python-based tools, WRF4PALM, has been developed for offline nesting of the PALM model system 6.0 into the Weather Research and Forecasting (WRF) modelling system. Time-dependent boundary conditions of the atmosphere are critical for accurate representation of microscale meteorological dynamics in high-resolution real-data simulations. WRF4PALM generates initial and boundary conditions from WRF outputs to provide time-varying meteorological forcing for PALM. The WRF model has been used across the atmospheric science community for a broad range of multidisciplinary applications. The PALM model system 6.0 is a turbulence-resolving large-eddy simulation model with an additional Reynolds-averaged Navier–Stokes (RANS) mode for atmospheric and oceanic boundary layer studies at microscale (Maronga et al., 2020). Currently PALM has the capability to ingest output from the regional scale Consortium for Small-scale Modelling (COSMO) atmospheric prediction model. However, COSMO is not an open source model and requires a licence agreement for operational use or academic research (http://www.cosmo-model.org/, last access: 23 April 2021). This paper describes and validates the new free and open-source WRF4PALM tools (available at https://github.com/dongqi-DQ/WRF4PALM, last access: 23 April 2021). Two case studies using WRF4PALM are presented for Christchurch, New Zealand, which demonstrate successful PALM simulations driven by meteorological forcing from WRF outputs. The WRF4PALM tools presented here can potentially be used for micro- and mesoscale studies worldwide, for example in boundary layer studies, air pollution dispersion modelling, wildfire emissions and spread, urban weather forecasting, and agricultural meteorology.
3
Badeke, Ronny, Volker Matthias, and David Grawe. "Parameterizing the vertical downward dispersion of ship exhaust gas in the near field." Atmospheric Chemistry and Physics 21, no. 8 (April 20, 2021): 5935–51. http://dx.doi.org/10.5194/acp-21-5935-2021.
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Abstract. Estimating the impact of ship emissions on local air quality is a topic of high relevance, especially in large harbor cities. For chemistry-transport modeling studies, the initial plume rise and dispersion play a crucial role for the distribution of pollutants into vertical model layers. This study aims at parameterizing the vertical downward dispersion in the near field of a prototype cruise ship, depending on several meteorological and technical input parameters. By using the microscale chemistry, transport and stream model (MITRAS), a parameterization scheme was developed to calculate the downward dispersion, i.e., the fraction of emissions, which will be dispersed below stack height. This represents the local concentration in the vicinity of the ship. Cases with and without considering the obstacle effect of the ship have been compared. Wind speed and ship size were found to be the strongest factors influencing the downward dispersion, which can reach values up to 55 % at high wind speed and lateral wind. This compares to 31 % in the case where the obstacle effect was not considered and shows the importance of obstacle effects when assessing the ground-level pollution situation in ports.
4
Liang, Qian, Yucong Miao, Gen Zhang, and Shuhua Liu. "Simulating Microscale Urban Airflow and Pollutant Distributions Based on Computational Fluid Dynamics Model: A Review." Toxics 11, no. 11 (November 13, 2023): 927. http://dx.doi.org/10.3390/toxics11110927.
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Urban surfaces exert profound influences on local wind patterns, turbulence dynamics, and the dispersion of air pollutants, underscoring the critical need for a thorough understanding of these processes in the realms of urban planning, design, construction, and air quality management. The advent of advanced computational capabilities has propelled the computational fluid dynamics model (CFD) into becoming a mature and widely adopted tool to investigate microscale meteorological phenomena in urban settings. This review provides a comprehensive overview of the current state of CFD-based microscale meteorological simulations, offering insights into their applications, influential factors, and challenges. Significant variables such as the aspect ratio of street canyons, building geometries, ambient wind directions, atmospheric boundary layer stabilities, and street tree configurations play crucial roles in influencing microscale physical processes and the dispersion of air pollutants. The integration of CFD with mesoscale meteorological models and cutting-edge machine learning techniques empowers high-resolution, precise simulations of urban meteorology, establishing a robust scientific basis for sustainable urban development, the mitigation of air pollution, and emergency response planning for hazardous substances. Nonetheless, the broader application of CFD in this domain introduces challenges in grid optimization, enhancing integration with mesoscale models, addressing data limitations, and simulating diverse weather conditions.
5
Trini Castelli, S., G. Tinarelli, and T. G. Reisin. "Comparison of atmospheric modelling systems simulating the flow, turbulence and dispersion at the microscale within obstacles." Environmental Fluid Mechanics 17, no. 5 (March 8, 2017): 879–901. http://dx.doi.org/10.1007/s10652-017-9520-5.
6
Shcherbina, Andrey Y., Miles A. Sundermeyer, Eric Kunze, Eric D’Asaro, Gualtiero Badin, Daniel Birch, Anne-Marie E. G. Brunner-Suzuki, et al. "The LatMix Summer Campaign: Submesoscale Stirring in the Upper Ocean." Bulletin of the American Meteorological Society 96, no. 8 (August 1, 2015): 1257–79. http://dx.doi.org/10.1175/bams-d-14-00015.1.
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Abstract Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for smaller-scale stirring processes. Here, the authors describe a major oceanographic field experiment aimed at observing and understanding the processes responsible for stirring at scales of 0.1–10 km. Stirring processes of varying intensity were studied in the Sargasso Sea eddy field approximately 250 km southeast of Cape Hatteras. Lateral variability of water-mass properties, the distribution of microscale turbulence, and the evolution of several patches of inert dye were studied with an array of shipboard, autonomous, and airborne instruments. Observations were made at two sites, characterized by weak and moderate background mesoscale straining, to contrast different regimes of lateral stirring. Analyses to date suggest that, in both cases, the lateral dispersion of natural and deliberately released tracers was O(1) m2 s–1 as found elsewhere, which is faster than might be expected from traditional shear dispersion by persistent mesoscale flow and linear internal waves. These findings point to the possible importance of kilometer-scale stirring by submesoscale eddies and nonlinear internal-wave processes or the need to modify the traditional shear-dispersion paradigm to include higher-order effects. A unique aspect of the Scalable Lateral Mixing and Coherent Turbulence (LatMix) field experiment is the combination of direct measurements of dye dispersion with the concurrent multiscale hydrographic and turbulence observations, enabling evaluation of the underlying mechanisms responsible for the observed dispersion at a new level.
7
Farkas, Orsolya, and Ákos Török. "Dust deposition, microscale flow- and dispersion model of particulate matter, examples from the city center of Budapest." Időjárás 12, no. 1 (2019): 39–55. http://dx.doi.org/10.28974/idojaras.2019.1.3.
8
Weger, Michael, and Bernd Heinold. "Air pollution trapping in the Dresden Basin from gray-zone scale urban modeling." Atmospheric Chemistry and Physics 23, no. 21 (November 6, 2023): 13769–90. http://dx.doi.org/10.5194/acp-23-13769-2023.
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Abstract. The microscale variability of urban air pollution is essentially driven by the interaction between meteorology and urban topography, which remains challenging to represent spatially accurately and computationally efficiently in urban dispersion models. Natural topography can additionally exert a considerable amplifying effect on urban background pollution, depending on atmospheric stability. This requires an equally important representation in models, as even subtle terrain-height variations can enforce characteristic local flow regimes. In this model study, the effects of urban and natural topography on the local winds and air pollution dispersion in the Dresden Basin in the Eastern German Elbe valley are investigated. A new, efficient urban microscale model is used within a multiscale air quality modeling framework. The simulations that consider real meteorological and emission conditions focus on two periods in late winter and early summer, respectively, as well as on black carbon (BC), a key air pollutant mainly emitted from motorized traffic. As a complement to the commonly used mass concentrations, the particle age content (age concentration) is simulated. This concept, which was originally developed to study hydrological reservoir flows in a Eulerian framework, is adapted here for the first time for atmospheric boundary-layer modeling. The approach is used to identify stagnant or recirculating orographic air flows and resulting air pollution trapping. An empirical orthogonal function (EOF) analysis is applied to the simulation results to attribute the air pollution modes to specific weather patterns and quantify their significance. Air quality monitoring data for the region are used for model evaluation. The model results show a strong sensitivity to atmospheric conditions, but generally confirm increased BC levels in Dresden due to the valley location. The horizontal variability of mass concentrations is dominated by the patterns of traffic emissions, which overlay potential orography-driven pollutant accumulations. Therefore, an assessment of the orographic impact on air pollution is usually inconclusive. However, using the age-concentration metric, which filters out direct emission effects, previously undetected spatial patterns are discovered that are largely modulated by the surface orography. The comparison with a dispersion simulation assuming spatially homogeneous emissions also proves the robustness of the orographic flow information contained in the age-concentration distribution and shows it to be a suitable metric for assessing orographic air pollution trapping. The simulation analysis indicates several air quality hotspots on the southwestern slopes of the Dresden Basin and in the southern side valley, the Döhlen Basin, depending on the prevailing wind direction.
9
Varentsov, A. I., V. M. Stepanenko, E. V. Mortikov, A. V. Debolskiy, R. D. Kouznetsov, and M. Sofiev. "On the use of large-eddy simulation time data coarsening for dispersion forecasting in the SILAM atmospheric composition model." IOP Conference Series: Earth and Environmental Science 1023, no. 1 (May 1, 2022): 012008. http://dx.doi.org/10.1088/1755-1315/1023/1/012008.
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Abstract The paper presents the results of one-way coupling of a large eddy simulation model and an atmospheric composition and diffusion complex SILAM. This study investigates a possibility of large eddy simulation time data coarsening (filtering) for use in SILAM for microscale calculations. Experiments with scalar tracers with a limited lifetime are carried out under conditions of convective boundary layer. A comparison between the calculations with filtered and nonfiltered data demonstrate that time data coarsening is possible without a significant loss in accuracy for tracers whose lifetime is much longer than the coarsening scale and the timestep of the filtered data.
10
KAVASSERI, RAJESH G., and RADHAKRISHNAN NAGARAJAN. "A QUALITATIVE DESCRIPTION OF BOUNDARY LAYER WIND SPEED RECORDS." Fluctuation and Noise Letters 06, no. 02 (June 2006): L201—L213. http://dx.doi.org/10.1142/s021947750600329x.
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The complexity of the atmosphere endows it with the property of turbulence by virtue of which, wind speed variations in the atmospheric boundary layer (ABL) exhibit highly irregular fluctuations that persist over a wide range of temporal and spatial scales. Despite the large and significant body of work on microscale turbulence, understanding the statistics of atmospheric wind speed variations has proved to be elusive and challenging. Knowledge about the nature of wind speed at ABL has far reaching impact on several fields of research such as meteorology, hydrology, agriculture, pollutant dispersion, and more importantly wind energy generation. In the present study, temporal wind speed records from twenty eight stations distributed through out the state of North Dakota (ND, USA), (~ 70,000 square-miles) and spanning a period of nearly eight years are analyzed. We show that these records exhibit a characteristic broad multifractal spectrum irrespective of the geographical location and topography. The rapid progression of air masses with distinct qualitative characteristics originating from Polar regions, Gulf of Mexico and Northern Pacific account for irregular changes in the local weather system in ND. We hypothesize that one of the primary reasons for the observed multifractal structure could be the irregular recurrence and confluence of these three air masses.
11
Jacob, Jérôme, Lucie Merlier, Felix Marlow, and Pierre Sagaut. "Lattice Boltzmann Method-Based Simulations of Pollutant Dispersion and Urban Physics." Atmosphere 12, no. 7 (June 28, 2021): 833. http://dx.doi.org/10.3390/atmos12070833.
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Mesocale atmospheric flows that develop in the boundary layer or microscale flows that develop in urban areas are challenging to predict, especially due to multiscale interactions, multiphysical couplings, land and urban surface thermal and geometrical properties and turbulence. However, these different flows can indirectly and directly affect the exposure of people to deteriorated air quality or thermal environment, as well as the structural and energy loads of buildings. Therefore, the ability to accurately predict the different interacting physical processes determining these flows is of primary importance. To this end, alternative approaches based on the lattice Boltzmann method (LBM) wall model large eddy simulations (WMLESs) appear particularly interesting as they provide a suitable framework to develop efficient numerical methods for the prediction of complex large or smaller scale atmospheric flows. In particular, this article summarizes recent developments and studies performed using the hybrid recursive regularized collision model for the simulation of complex or/and coupled turbulent flows. Different applications to the prediction of meteorological humid flows, urban pollutant dispersion, pedestrian wind comfort and pressure distribution on urban buildings including uncertainty quantification are especially reviewed. For these different applications, the accuracy of the developed approach was assessed by comparison with experimental and/or numerical reference data, showing a state of the art performance. Ongoing developments focus now on the validation and prediction of indoor environmental conditions including thermal mixing and pollutant dispersion in different types of rooms equipped with heat, ventilation and air conditioning systems.
12
Qu, Yongfeng, Maya Milliez, Luc Musson-Genon, and Bertrand Carissimo. "Modelling Radiative and Convective Thermal Exchanges over a European City Center and Their Effects on Atmospheric Dispersion." Sustainability 14, no. 12 (June 14, 2022): 7295. http://dx.doi.org/10.3390/su14127295.
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Micro-meteorological studies of urban flow and pollution dispersion often assume a neutral atmosphere and often the three-dimensional variation in temperature fields and flow around buildings is neglected in most building energy balance models. The aim of this work is to present the results of development and validation of a three-dimensional tool coupling thermal energy balance of the buildings and modelling of the atmospheric flow and dispersion in urban areas. To do so, a 3D microscale atmospheric radiative scheme has been developed in the atmospheric module of the computational fluid dynamics (CFD) code Code_Saturne adapted to detailed building geometries. The full coupling of the radiative transfer and fluid dynamics models has been validated with idealized cases. In this paper, our focus is to simulate and compare with measurements the diurnal evolution of the brightness surface temperatures and the momentum and energy fluxes for a neighborhood in the city center of Toulouse, in the southwest part of France. This is performed by taking into account the 3D effects of the flow around the buildings and all thermal exchanges, in real meteorological conditions, and compare them to aircraft infrared images and in situ measurements on a meteorological mast. The calculation mesh developed for the city center and the simulation conditions for the selected day of the field campaign are presented. The results are evaluated with the measurements from the Canopy and Aerosol Particles Interactions in TOulouse Urban Layer experiment (CAPITOUL). In addition, the second purpose of this work is to investigate a hypothetical release of passive pollutant dispersion in the same area of Toulouse under different thermal transfer conditions for the street and the buildings surfaces: neutral and 3D radiative transfer heating. The presence of heat transfer continually modifies the airflow field while the airflow in the neutral case reaches a stationary state. Compared to the neutral case, taking into account the thermal transfer enhances the turbulence kinetic energy and vertical velocity (especially at the roof level) due to buoyancy forces. The simulation results also show that the thermal effects considerably alter the plume shape.
13
Kristóf, Gergely, and Bálint Papp. "Application of GPU-Based Large Eddy Simulation in Urban Dispersion Studies." Atmosphere 9, no. 11 (November 13, 2018): 442. http://dx.doi.org/10.3390/atmos9110442.
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While large eddy simulation has several advantages in microscale air pollutant dispersion modelling, the parametric investigation of geometries is not yet feasible because of its relatively high computational cost. By assuming an analogy between heat and mass transport processes, we utilize a Graphics Processing Unit based software—originally developed for mechanical engineering applications—to model urban dispersion. The software allows for the modification of the geometry as well as the visualization of the transient flow and concentration fields during the simulation, thus supporting the analysis and comparison of different design concepts. By placing passive turbulence generators near the inlet, a numerical wind tunnel was created, capable of producing the characteristic velocity and turbulence intensity profiles of the urban boundary layer. The model results show a satisfactory agreement with wind tunnel experiments examining single street canyons. The effect of low boundary walls placed in the middle of the road and adjacent to the walkways was investigated in a wide parameter range, along with the impact made by the roof slope angle. The presented approach can be beneficially used in the early phase of simulation driven urban design, by screening the concepts to be experimentally tested or simulated with high accuracy models.
14
Defforge, Cécile L., Bertrand Carissimo, Marc Bocquet, Raphaël Bresson, and Patrick Armand. "Improving Numerical Dispersion Modelling in Built Environments with Data Assimilation Using the Iterative Ensemble Kalman Smoother." Boundary-Layer Meteorology 179, no. 2 (January 14, 2021): 209–40. http://dx.doi.org/10.1007/s10546-020-00588-9.
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AbstractAir-pollution modelling at the local scale requires accurate meteorological inputs such as from the velocity field. These meteorological fields are generally simulated with microscale models (here Code_Saturne), which are forced with boundary conditions provided by larger scale models or observations. Local atmospheric simulations are very sensitive to the boundary conditions, whose accurate estimation is difficult but crucial. When observations of the wind speed and turbulence or pollutant concentration are available inside the domain, they provide supplementary information via data assimilation, to enhance the simulation accuracy by modifying the boundary conditions. Among the existing data assimilation methods, the iterative ensemble Kalman smoother (IEnKS) is adapted to urban-scale simulations. This method has already been found to increase the accuracy of wind-resource assessment. Here we assess the ability of the IEnKS method to improve scalar-dispersion modelling—an important component of air-quality modelling—by assimilating perturbed measurements inside the urban canopy. To test the data assimilation method in urban conditions, we use the observations provided by the Mock Urban Setting Test field campaign and consider cases with neutral and stable conditions, and the boundary conditions consisting of the horizontal velocity components and turbulence. We prove the capacity of the IEnKS method to assimilate observations of velocity as well as pollutant concentration. In both cases, the accuracy of pollutant concentration estimates is enhanced by 40–60%. We also show that assimilating both types of observations allows further improvements of turbulence predictions by the model.
15
Birmili, W., B. Alaviippola, D. Hinneburg, O. Knoth, T. Tuch, J. Borken-Kleefeld, and A. Schacht. "Dispersion of traffic-related exhaust particles near the Berlin urban motorway – estimation of fleet emission factors." Atmospheric Chemistry and Physics 9, no. 7 (April 2, 2009): 2355–74. http://dx.doi.org/10.5194/acp-9-2355-2009.
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Abstract. Atmospheric particle number size distributions of airborne particles (diameter range 10–500 nm) were collected over ten weeks at three sites in the vicinity of the A100 urban motorway in Berlin, Germany. The A100 carries about 180 000 vehicles on a weekday. The roadside particle distributions showed a number maximum between 20 and 60 nm clearly related to the motorway emissions. The average total number concentration at roadside was 28 000 cm−3 with a total range of 1200–168 000 cm−3. At distances of 80 and 400 m from the motorway the concentrations decreased to mean levels of 11 000 and 9000 cm−3, respectively. An obstacle-resolving dispersion model was applied to simulate the 3-D flow field and traffic tracer transport in the urban environment around the motorway. By inverse modelling, vehicle emission factors were derived that are representative of a fleet with a relative share of 6% lorry-like vehicles, and driving at a speed of 80 km h−1. Three different calculation approaches were compared, which differ in the choice of the experimental winds driving the flow simulation. The average emission factor per vehicle was 2.1 (±0.2) · 1014 km−1 for particle number and 0.077 (±0.01) · 1014 cm3 km−1 for particle volume. Regression analysis suggested that lorry-like vehicles emit 123 (±28) times more particle number than passenger car-like vehicles, and lorry-like vehicles account for about 91% of particulate number emissions on weekdays. Our work highlights the increasing applicability of 3-D flow models in urban microscale environments and their usefulness for determining traffic emission factors.
16
Kovalets, Ivan V., Vladimir Y. Korolevych, Alexander V. Khalchenkov, Ievgen A. Ievdin, Mark J. Zheleznyak, and Spyros Andronopoulos. "Influence of the diagnostic wind field model on the results of calculation of the microscale atmospheric dispersion in moderately complex terrain." Atmospheric Environment 79 (November 2013): 29–35. http://dx.doi.org/10.1016/j.atmosenv.2013.06.015.
17
Baumann-Stanzer, Kathrin, Sirma Stenzel, Gabriele Rau, Martin Piringer, Felix Feichtinger, and Théophane Costabloz. "Monitoring and Modeling Roof-Level Wind Speed in a Changing City." Atmosphere 11, no. 1 (January 10, 2020): 87. http://dx.doi.org/10.3390/atmos11010087.
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Results of an observational campaign and model study are presented demonstrating how the wind field at roof-level in the urban area of Vienna changed due to the construction of a new building nearby. The investigation was designed with a focus on the wind energy yield of a roof-mounted small wind turbine but the findings are also relevant for air dispersion applications. Wind speed profiles above roof top are simulated with the complex fluid dynamics (CFD) model MISKAM (Mikroskaliges Klima- und Ausbreitungsmodell, microscale climate and dispersion model). The comparison to mast measurements reveals that the model underestimates the wind speeds within the first few meters above the roof, but successfully reproduces wind conditions at 10 m above the roof top (corresponding to about 0.5 times the building height). Scenario simulations with different building configurations at the adjacent property result in an increase or decrease of wind speed above roof top depending on the flow direction at the upper boundary of the urban canopy layer (UCL). The maximum increase or decrease in wind speed caused by the alternations in building structure nearby is found to be in the order of 10%. For the energy yield of a roof-mounted small wind turbine at this site, wind speed changes of this magnitude are negligible due to the generally low prevailing wind speeds of about 3.5 m s−1. Nevertheless, wind speed changes of this order could be significant for wind energy yield in urban areas with higher mean wind speeds. This effect in any case needs to be considered in siting and conducting an urban meteorological monitoring network in order to ensure the homogeneity of observed time-series and may alter the emission and dispersion of pollutants or odor at roof level.
18
Wu, Luolin, Jian Hang, Xuemei Wang, Min Shao, and Cheng Gong. "APFoam 1.0: integrated computational fluid dynamics simulation of O<sub>3</sub>–NO<sub><i>x</i></sub>–volatile organic compound chemistry and pollutant dispersion in a typical street canyon." Geoscientific Model Development 14, no. 7 (July 28, 2021): 4655–81. http://dx.doi.org/10.5194/gmd-14-4655-2021.
Abstract:
Abstract. Urban air quality issues are closely related to human health and economic development. In order to investigate street-scale flow and air quality, this study developed the atmospheric photolysis calculation framework (APFoam 1.0), an open-source computational fluid dynamics (CFD) code based on OpenFOAM, which can be used to examine microscale reactive pollutant formation and dispersion in an urban area. The chemistry module of APFoam has been modified by adding five new types of reactions, which can implement the atmospheric photochemical mechanism (full O3–NOx–volatile organic compound chemistry) coupled with a CFD model. Additionally, the model, including the photochemical mechanism (CS07A), air flow, and pollutant dispersion, has been validated and shows good agreement with SAPRC modeling and wind tunnel experimental data, indicating that APFoam has sufficient ability to study urban turbulence and pollutant dispersion characteristics. By applying APFoam, O3–NOx–volatile organic compound (VOC) formation processes and dispersion of the reactive pollutants were analyzed in an example of a typical street canyon (aspect ratio H/W=1). The comparison of chemistry mechanisms shows that O3 and NO2 are underestimated, while NO is overestimated if the VOC reactions are not considered in the simulation. Moreover, model sensitivity cases reveal that 82 %–98 % and 75 %–90 % of NO and NO2, respectively, are related to the local vehicle emissions, which is verified as the dominant contributor to local reactive pollutant concentration in contrast to background conditions. In addition, a large amount of NOx emissions, especially NO, is beneficial to the reduction of O3 concentrations since NO consumes O3. Background precursors (NOx/VOCs) from boundary conditions only contribute 2 %–16 % and 12 %–24 % of NO and NO2 concentrations and raise O3 concentrations by 5 %–9 %. Weaker ventilation conditions could lead to the accumulation of NOx and consequently a higher NOx concentration but lower O3 concentration due to the stronger NO titration effect, which would consume O3. Furthermore, in order to reduce the reactive pollutant concentrations under the odd–even license plate policy (reduce 50 % of the total vehicle emissions), vehicle VOC emissions should be reduced by at least another 30 % to effectively lower O3, NO, and NO2 concentrations at the same time. These results indicate that the examination of the precursors (NOx and VOCs) from both traffic emissions and background boundaries is the key point for understanding O3–NOx–VOCs chemistry mechanisms better in street canyons and providing effective guidelines for the control of local street air pollution.
19
Özgökmen, Tamay M., Francisco J. Beron-Vera, Darek Bogucki, Shuyi S. Chen, Clint Dawson, William Dewar, Annalisa Griffa, et al. "Research Overview of the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE)." International Oil Spill Conference Proceedings 2014, no. 1 (May 1, 2014): 544–60. http://dx.doi.org/10.7901/2169-3358-2014.1.544.
Abstract:
ABSTRACT CARTHE (http://carthe.org/) is a Gulf of Mexico Research Initiative (GoMRI) consortium established through a competitive peer-reviewed selection process. CARTHE comprises 26 principal investigators from 14 universities and research institutions distributed across four Gulf of Mexico states and other four states. It fuses into one group investigators with unique scientific and technical knowledge and extensive publications related to oil fate/transport processes, oceanic and atmospheric turbulence, air-sea interactions, tropical cyclones and winter storms, and coastal and nearshore modeling and observations. Our primary goal is to accurately predict the fate of hydrocarbons released into the environment. Achieving this goal is particularly challenging since petroleum releases into the environment interact with natural processes across six orders of magnitude of time and space scales. We are developing a multi-scale modeling tool by incorporating state-of-the-art hydrophysical models, each applicable for a restricted range of scales, into a single, interconnected modeling system to predict the physical dispersal of hydrocarbons across scales ranging from the microscale at the wellhead to oceanic and atmospheric mesoscales. CARTHE is also conducting novel in-situ observations and laboratory experiments specifically designed for quantifying submesoscale dispersion as well as for both model validation and parameterization. Finally, we are providing a robust set of uncertainty metrics and analysis tools to assess model performance and quantify predictive uncertainty.
20
Zhao, Bin, Kuo-Nan Liou, Yu Gu, Cenlin He, Wee-Liang Lee, Xing Chang, Qinbin Li, et al. "Impact of buildings on surface solar radiation over urban Beijing." Atmospheric Chemistry and Physics 16, no. 9 (May 12, 2016): 5841–52. http://dx.doi.org/10.5194/acp-16-5841-2016.
Abstract:
Abstract. The rugged surface of an urban area due to varying buildings can interact with solar beams and affect both the magnitude and spatiotemporal distribution of surface solar fluxes. Here we systematically examine the impact of buildings on downward surface solar fluxes over urban Beijing by using a 3-D radiation parameterization that accounts for 3-D building structures vs. the conventional plane-parallel scheme. We find that the resulting downward surface solar flux deviations between the 3-D and the plane-parallel schemes are generally ±1–10 W m−2 at 800 m grid resolution and within ±1 W m−2 at 4 km resolution. Pairs of positive–negative flux deviations on different sides of buildings are resolved at 800 m resolution, while they offset each other at 4 km resolution. Flux deviations from the unobstructed horizontal surface at 4 km resolution are positive around noon but negative in the early morning and late afternoon. The corresponding deviations at 800 m resolution, in contrast, show diurnal variations that are strongly dependent on the location of the grids relative to the buildings. Both the magnitude and spatiotemporal variations of flux deviations are largely dominated by the direct flux. Furthermore, we find that flux deviations can potentially be an order of magnitude larger by using a finer grid resolution. Atmospheric aerosols can reduce the magnitude of downward surface solar flux deviations by 10–65 %, while the surface albedo generally has a rather moderate impact on flux deviations. The results imply that the effect of buildings on downward surface solar fluxes may not be critically significant in mesoscale atmospheric models with a grid resolution of 4 km or coarser. However, the effect can play a crucial role in meso-urban atmospheric models as well as microscale urban dispersion models with resolutions of 1 m to 1 km.
21
Birmili, W., B. Alaviippola, D. Hinneburg, O. Knoth, T. Tuch, J. Kleefeld-Borken, and A. Schacht. "Dispersion of traffic-related exhaust particles near the Berlin urban motorway: estimation of fleet emission factors." Atmospheric Chemistry and Physics Discussions 8, no. 4 (August 15, 2008): 15537–94. http://dx.doi.org/10.5194/acpd-8-15537-2008.
Abstract:
Abstract. Atmospheric particle number size distributions of airborne particles (diameter range 10–500 nm) were measured over ten weeks at three sites in the vicinity of the A100 urban motorway in Berlin, Germany. The A100 carries about 180 000 vehicles on a weekday, and roadside particle size distributions showed a number maximum between 20 and 60 nm clearly related to the motorway emissions. The average total number concentration at roadside was 28 000 cm−3 with a total range between 1200 and 168 000 cm−3. At distances of 80 and 400 m from the motorway the concentrations decreased to mean levels of 11 000 and 9 000 cm−3, respectively. An obstacle-resolving dispersion model was applied to simulate the 3-D flow field and traffic tracer transport in the urban environment around the motorway. By inverse modelling, vehicle emission factors were derived, representative of a relative share of 6% lorry-like vehicles, and a driving speed of about 80 km h−1. Three different calculation approaches were compared, which differ in the choice of the experimental winds driving the flow simulation. The average emission factor per vehicle was 2.1(±0.2) · 1014 km−1 for particle number and 0.077(±0.01) · 1014 cm3 km−1 for particle volume. Regression analysis suggested that lorry-like vehicles emit 116 (± 21) times more particulate number than passenger car-like vehicles, and that lorry-like vehicles account for about 91% of particulate number emissions on weekdays. Our work highlights the increasing applicability of 3-D flow models in urban microscale environments and their usefulness in determining traffic emission factors.
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Ruprecht, Daniel, Rupert Klein, and Andrew J. Majda. "Modulation of Internal Gravity Waves in a Multiscale Model for Deep Convection on Mesoscales." Journal of the Atmospheric Sciences 67, no. 8 (August 1, 2010): 2504–19. http://dx.doi.org/10.1175/2010jas3269.1.
Abstract:
Abstract Starting from the conservation laws for mass, momentum, and energy together with a three-species bulk microphysics model, a model for the interaction of internal gravity waves and deep convective hot towers is derived using multiscale asymptotic techniques. From the leading-order equations, a closed model for the large-scale flow is obtained analytically by applying horizontal averages conditioned on the small-scale hot towers. No closure approximations are required besides adopting the asymptotic limit regime on which the analysis is based. The resulting model is an extension of the anelastic equations linearized about a constant background flow. Moist processes enter through the area fraction of saturated regions and through two additional dynamic equations describing the coupled evolution of the conditionally averaged small-scale vertical velocity and buoyancy. A two-way coupling between the large-scale dynamics and these small-scale quantities is obtained: moisture reduces the effective stability for the large-scale flow, and microscale up- and downdrafts define a large-scale averaged potential temperature source term. In turn, large-scale vertical velocities induce small-scale potential temperature fluctuations due to the discrepancy in effective stability between saturated and nonsaturated regions. The dispersion relation and group velocity of the system are analyzed and moisture is found to have several effects: (i) it reduces vertical energy transport by waves, (ii) it increases vertical wavenumbers but decreases the slope at which wave packets travel, (iii) it introduces a new lower horizontal cutoff wavenumber in addition to the well-known high wavenumber cutoff, and (iv) moisture can cause critical layers. Numerical examples reveal the effects of moisture on steady-state and time-dependent mountain waves in the present hot-tower regime.
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Pérez, Isidro A., Mª Ángeles García, Mª Luisa Sánchez, Nuria Pardo, and Beatriz Fernández-Duque. "Key Points in Air Pollution Meteorology." International Journal of Environmental Research and Public Health 17, no. 22 (November 11, 2020): 8349. http://dx.doi.org/10.3390/ijerph17228349.
Abstract:
Although emissions have a direct impact on air pollution, meteorological processes may influence inmission concentration, with the only way to control air pollution being through the rates emitted. This paper presents the close relationship between air pollution and meteorology following the scales of atmospheric motion. In macroscale, this review focuses on the synoptic pattern, since certain weather types are related to pollution episodes, with the determination of these weather types being the key point of these studies. The contrasting contribution of cold fronts is also presented, whilst mathematical models are seen to increase the analysis possibilities of pollution transport. In mesoscale, land–sea and mountain–valley breezes may reinforce certain pollution episodes, and recirculation processes are sometimes favoured by orographic features. The urban heat island is also considered, since the formation of mesovortices determines the entry of pollutants into the city. At the microscale, the influence of the boundary layer height and its evolution are evaluated; in particular, the contribution of the low-level jet to pollutant transport and dispersion. Local meteorological variables have a major influence on calculations with the Gaussian plume model, whilst some eddies are features exclusive to urban environments. Finally, the impact of air pollution on meteorology is briefly commented on.
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GOL’TSEV, V. A., V. A. DUDKO, E. V. KISELEV, and A. B. LEBED. "STUDY OF THE AERO-DISPERSION SYSTEM IN THE FERROALLOY WORKSHOP WORKING AREA." Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 78, no. 6 (July 29, 2022): 553–61. http://dx.doi.org/10.32339/0135-5910-2022-6-553-561.
Abstract:
A large proportion of the gases from the process units in the casting and furnace bays of ferroalloy plants enter the production facilities, where they form a complex aerodisperse system. The resulting aerosols pose a great danger to the operating personnel due to the presence of toxic and carcinogenic components. To develop emission prevention and elimination methods, the sources of industrial aerosol formation during silicomanganese production, particle size distribution and chemical composition of the dust sludge, the behaviour of the gas-dispersed system in the working area have been analyzed. Scanning electron microscope TESCAN VEGA3 with microanalytical attachment Oxford X-Act was used to study the morphology of dust particles sediment. It was established that the aerodisperse system of the shop atmosphere consists of condensation aerosol with submicron particles of manganese and silicon oxides and dispersion aerosol generated mostly at the transportation and loading of charge materials. The behaviour of particles of silicon and manganese oxides, forming a part of the condensed aerosol in the workshop atmosphere was considered. The motion parameters of particles of various chemical compositions simulating compositions of condensation and dispersion aerosols typical of the working area atmospheric aerosol system were calculated. Time and velocity characteristics of aerosol condensation particles for silicon and manganese oxides of 0.1; 1 and 5 microns in diameter are provided.
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Oputina, I. P., V. A. Shklyaev, and N. V. Kostyleva. "Solid particles as an indicator of the placement of air pollution monitoring posts in Murmansk." Arctic: Ecology and Economy 12, no. 4 (December 2022): 598–610. http://dx.doi.org/10.25283/2223-4594-2022-4-598-610.
Abstract:
The article presents the results of field measurements and analysis of atmospheric air samples at 25 characteristic points on the territory of Murmansk in 2017—2018. For all particles taken from atmospheric air the researchers determine the granulometric, morphological and chemical composition using a high-resolution scanning electron microscope S-3400N Hitachi. They consider meteorological conditions as of the dates of sampling from the point of view of their effect on the dispersion of pollutants. The results made it possible to preliminary determine the regions on the territory of Murmansk that are most and least dependent on meteorological conditions, as well as to formulate recommendations for improving the atmospheric air monitoring network in Murmansk.
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Kochanski, A. K., E. R. Pardyjak, R. Stoll, A. Gowardhan, M. J. Brown, and W. J. Steenburgh. "One-Way Coupling of the WRF–QUIC Urban Dispersion Modeling System." Journal of Applied Meteorology and Climatology 54, no. 10 (October 2015): 2119–39. http://dx.doi.org/10.1175/jamc-d-15-0020.1.
Abstract:
AbstractSimulations of local weather and air quality in urban areas must account for processes spanning from meso- to microscales, including turbulence and transport within the urban canopy layer. Here, the authors investigate the performance of the building-resolving Quick Urban Industrial Complex (QUIC) Dispersion Modeling System driven with mean wind profiles from the mesoscale Weather Research and Forecasting (WRF) Model. Dispersion simulations are performed for intensive observation periods 2 and 8 of the Joint Urban 2003 field experiment conducted in Oklahoma City, Oklahoma, using an ensemble of expert-derived wind profiles from observational data as well as profiles derived from WRF runs. The results suggest that WRF can be used successfully as a source of inflow boundary conditions for urban simulations, without the collection and processing of intensive field observations needed to produce expert-derived wind profiles. Detailed statistical analysis of tracer concentration fields suggests that, for the purpose of the urban dispersion, WRF simulations provide wind forcing as good as individual or ensemble expert-derived profiles. Despite problems capturing the strength and the elevation of the Great Plains low-level jet, the WRF-simulated near-surface wind speed and direction were close to observations, thus assuring realistic forcing for urban dispersion estimates. Tests performed with multilayer and bulk urban parameterizations embedded in WRF did not provide any conclusive evidence of the superiority of one scheme over the other, although the dispersion simulations driven by the latter showed slightly better results.
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Xu, Bingjie, Mengxing Li, Qi Chen, Pengfei Liu, Baosong Xu, Ben Qiu, Liang Xu, and Zhao Han. "A Novel Method to Improve the Dispersibility of Silicon Nitride Powders in Aqueous Media." Nano 14, no. 09 (September 2019): 1950118. http://dx.doi.org/10.1142/s1793292019501182.
Abstract:
The present study describes a novel method to improve the dispersibility of silicon nitride powders in aqueous media. Specifically, a new Si3N4@g-C3N4 core–shell composite material was synthesized via annealing the mixture of silicon nitride and melamine under a nitrogen atmosphere using heating method. The effects of various initial mass ratios of Si3N4 and melamine on the structure and dispersibility of the composite were systematically investigated. The results of X-ray photoelectron spectroscopy and transmission electron microscope demonstrated that as-obtained Si3N4@g-C3N4 composite powders possess the core–shell structure, whereas the zeta potential and sedimentation analysis showed that they exhibit good dispersion in aqueous media. Furthermore, the colloidal dispersion of the composite powders is most stable when the initial mass ratio of Si3N4 and melamine is 100:3. The coated g-C3N4 could be completely removed in a cryogenic nitrogen atmosphere. The proposed process is expected to provide novel avenues for the study of dispersion of other inorganic powders.
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Zhang, Zhi Li, Hong Xiang Zhai, Zhen Ying Huang, Cui Wei Li, Yi Fan Wang, and Zhouyang. "Tribo-Chemical Reaction in Bulk Ti3SiC2 under Sliding Friction." Key Engineering Materials 280-283 (February 2007): 1357–60. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1357.
Abstract:
The Ti3SiC2 samples with a second phase TiC, prepared by hot-pressing progress route, were rubbed against low carbon steel disk with a sliding speed of 20 m/s under normal pressure 0.8 Mpa in atmosphere on a block-on-disk type friction tester. The morphology was observed by scanning electron microscope (SEM) and meanwhile the composition was checked by energy dispersion spectroscopy (EDS). X-ray diffraction (XRD) patterns show some impurity phases containing Ti, Si and Fe oxides in the samples. The possible tribo-chemical reaction mechanism on surface layer of Ti3SiC2 was suggested.
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Azarov, V. N., I. V. Stefanenko, and R. A. Burkhanova. "Research of Aerodynamic Characteristics of Asbestos-Cement Dust in the Ventilation Emissions to the Atmosphere." Applied Mechanics and Materials 878 (February 2018): 251–54. http://dx.doi.org/10.4028/www.scientific.net/amm.878.251.
Abstract:
The article describes the chemical properties of asbestos-cement dust and its effect on the human body. The main sources of dust emission at the enterprise for the production of asbestos-cement have been determined. Also in this research were determined the aerodynamic properties of particles of asbestos dust at the plant for the production of asbestos by method of fractional sedimentation. In the course of the experiment, the dispersion composition of dust was determined by the method of sedimentometry and analysis by means of a microscope and a PC. The dependence of the dust settling rate on the equivalent diameter of a particle in a probability-logarithmic grid is revealed.
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Liu, Jing, and Jing Feng Li. "Bi2Te3 and Bi2Te3/Nano-SiC Prepared by Mechanical Alloying and Spark Plasma Sintering." Key Engineering Materials 280-283 (February 2007): 397–400. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.397.
Abstract:
Bi2Te3-based alloys are currently best-known, technological thermoelectric materials near room temperature. In this paper, Bi2Te3 and nano-SiC dispersed Bi2Te3 were prepared by mechanical alloying followed by spark plasma sintering (SPS). Raw powders of Bi, Te and SiC were mixed and mechanically alloyed in an argon atmosphere using a planetary ball mill. The SPS temperature was 623K, and the holding time was 5 minutes. The samples were characterized by X-ray Diffraction (XRD) and Scanning electron Microscope (SEM). The thermoelectric properties: i.e. Seebeck coefficient, electrical resistivity and thermal conductivity were measured at temperatures from room temperature to 573K, followed by the evaluation of figure of merit. The results revealed that the SiC dispersion in the Bi2Te3 matrix increased Seebeck coefficient. Although the electrical resistivity was increased somewhat, the thermal conductivity was reduced by the SiC dispersion, indicating that promising thermoelectric materials with enhanced mechanical properties may be obtained in the nano-SiC dispersed Bi2Te3 composites with optimal compositions.
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Jeong, Kwang Jin, Jeong Hun Son, Seung Seok Lee, and Dong Sik Bae. "A Study on Fabrication, Dispersion and Surface Coating of Nanocarbon for MgO-C Refractories." Materials Science Forum 724 (June 2012): 404–7. http://dx.doi.org/10.4028/www.scientific.net/msf.724.404.
Abstract:
Spherical carbon nanoparticles were synthesized by sol-gel polymerization of resorcinol and formaldehyde in the presence of CTAB(cetyltrimethyl ammonium bromide) and subsequent carbonization at 900 in N2 atmosphere. It is found that the amount of CTAB, water and catalyst showed a significant impact on the morphology and size of carbon nanoparticles. The magnesia-carbon (MgO-C) bricks containing 1~4 wt% nanocarbon were prepared by adding various types of carbon black (CB), multi walled carbon nanotubes (CNT) and synthesized nanocarbon. The mechanical properties, oxidation resistance and corrosion resistance of the MgO-C brick in which the nanocarbon is added was investigated. The MgO-C refractories were characterized by Field Emission Scanning Electron Microscope (FE-SEM, MIRA II LMH), Cold Crush Strength (CCS).
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Chafidz, Achmad, Umi Rofiqah, Sumarno, Megawati, Mujtahid Kaavessina, and Thonthowy Jauhary. "Production of Microsphere Polystyrene Using Solution Enhanced Dispersion by CO2 Supercritical Fluids (SEDS)." Key Engineering Materials 805 (June 2019): 146–52. http://dx.doi.org/10.4028/www.scientific.net/kem.805.146.
Abstract:
Supercritical fluids (SCFs) process can be considered as an emerging ”clean“ technology for the production of small-size particles (e.g. micron-size). Microsphere is a material in micron scale which has been widely used as adsorbent, catalyst support, and drug delivery system. For advanced application, those materials are formulated in the form of porous microspheres. There are several methods that can be used using SCFs. One of them is Solution Enhanced Dispersion by Supercritical Fluids (SEDS). This method is considered to be suitable in obtaining the porous microsphere polystyrene. In this study, polystyrene was first dissolved into toluene (polystyrene solution) at different concentrations (i.e. 3, 5, 7, 9, 11, 13, 15 wt%) and then blown/sprayed together with supercritical carbon dioxide (CO2) through co-axial nozzle with two differents annulus diameter (i.e. 3.6 mm and 4.6 mm). Co-axial nozzle consists of two concentric pipes, inner pipe and annulus. Inner pipe for polystyrene solution flow and annulus for supercritical carbon dioxide flow. The expansion of these two of fluid was done both in atmospheric condition and in pressurized precipitator (40 bar). The resulted microsphere was analyzed by using SEM (Scanning Electron Microscope) to determine morphology and average diameter of the microsphere. The SEM analysis results showe that the smaller the initial concentration of solution used, the resulted microspheres tend to be smaller and less fibrils formed. Additionally, in the pressurized precipitator, the formed microspheres size was smaller and size distribution more narrow than that of atmospheric condition. Moreover, the use of smaller annulus diameter in co-axial nozzle produced smaller microsphere size and the size distribution was more uniform.
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Winkler, Aldo, Tania Contardo, Andrea Vannini, Sergio Sorbo, Adriana Basile, and Stefano Loppi. "Magnetic Emissions from Brake Wear are the Major Source of Airborne Particulate Matter Bioaccumulated by Lichens Exposed in Milan (Italy)." Applied Sciences 10, no. 6 (March 19, 2020): 2073. http://dx.doi.org/10.3390/app10062073.
Abstract:
The concentration of selected trace elements and the magnetic properties of samples of the lichen Evernia prunastri exposed for 3 months in Milan (Italy) were investigated to test if magnetic properties can be used as a proxy for the bioaccumulation of chemical elements in airborne particulate matter. Magnetic analysis showed intense properties driven by magnetite-like minerals, leading to significant correlations between magnetic susceptibility and the concentration of Fe, Cr, Cu, and Sb. Selected magnetic particles were characterized by Scanning Electron Microscope and Energy Dispersion System microanalyses, and their composition, morphology and grain size supported their anthropogenic, non-exhaust origin. The overall combination of chemical, morphoscopic and magnetic analyses strongly suggested that brake abrasion from vehicles is the main source of the airborne particles accumulated by lichens. It is concluded that magnetic susceptibility is an excellent parameter for a simple, rapid and cost-effective characterization of atmospheric trace metal pollution using lichens.
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Sarda-Estève, Roland, Dominique Baisnée, Benjamin Guinot, John Sodeau, David O’Connor, Jordina Belmonte, Jean-Pierre Besancenot, et al. "Variability and Geographical Origin of Five Years Airborne Fungal Spore Concentrations Measured at Saclay, France from 2014 to 2018." Remote Sensing 11, no. 14 (July 13, 2019): 1671. http://dx.doi.org/10.3390/rs11141671.
Abstract:
Airborne fungal spores (AFS) represent the major fraction of primary biological aerosol particles (PBAPs), and they are studied worldwide largely due to their important role within the Earth system. They have an impact on climate and human health, and they contribute to the propagation of diseases. As their presence in the air depends largely on studied ecosystems, a spore trap was used to monitor their atmospheric concentrations from 2014 to December 2018 in Saclay, a suburban area in the megacity of Paris. The main objective of this work was: (1) to understand the atmospheric variability of AFS in relation to different variables such as meteorological factors, agricultural practice, and (2) to identify their geographical origin by using a source receptor model. During our period of observation, 30 taxa have been identified under a light microscope. In order of importance, Ascospores, Cladosporium, Basidiospores, Tilletiopsis, Alternaria were found to be the most abundant types respectively (50.8%, 33.6%, 7.6%, 1.8%, and 1.3%) accounting for 95% of the atmospheric concentrations. We observed a general decrease associated with a strong interannual variability. A bimodal seasonal cycle was identified with a first maximum in July and a second in October. The main parameters driving the atmospheric concentration are temperature and precipitation. The daily variability is strongly activated by successive periods of hot weather and rainfall, multiplying the concentration by a factor of 1000 in less than 12 hours. Results from the source receptor model ZeFir point out unambiguous different origins of AFS due to specific sources impacting the observation site. Our study also indicated that a hydrological stress has a direct effect on the daily concentrations. This last point should be taken into account for every stressed ecosystem studied in a global warming context. This is particularly important for Mediterranean areas where water is a key control of the growth and dispersion of fungal spores.
35
Bangash, Muhammad, Graziano Ubertalli, Davide Di Saverio, Monica Ferraris, and Niu Jitai. "Joining of Aluminium Alloy Sheets to Aluminium Alloy Foam Using Metal Glasses." Metals 8, no. 8 (August 6, 2018): 614. http://dx.doi.org/10.3390/met8080614.
Abstract:
Aluminium alloy foam is a lightweight material with high energy absorption properties and can potentially replace bulk Al-components. The aim of this work is to develop a brazing technique to join aluminium facing sheets to aluminium alloy foam to obtain aluminium foam sandwich panels for applications where high service temperature is a requirement. Al-6016 alloy sheets were brazed to aluminium alloy foam using two aluminium based (Al-Cu-Mg and Al-Si-Mg-Ti) metal glasses at 560 °C–590 °C in an argon atmosphere. Microstructure and microhardness profiles of the aluminium alloy sheet/aluminium alloy foam brazed joints were analysed using a microhardness tester and scanning electron microscope equipped with electron dispersion spectroscopy. A three-point bending test was conducted to study the flexural behaviour of the aluminium foam sandwich composite panels.
36
Prošek, Zdeněk, Petr Svora, and Petr Kuklík. "Protection of Wood to against Degradation by TiO2: Scanning Electron Microscopy and Energy Dispersive Spectroscopy." Key Engineering Materials 898 (August 27, 2021): 87–92. http://dx.doi.org/10.4028/www.scientific.net/kem.898.87.
Abstract:
External wooden structures have own place in the building industry for ages. The problem is that wood easily degrades due to UV radiation, atmospheric conditions and biological aggressors. We are trying to eliminate degradable factors by photocatalytic materials (namely titanium oxide). Those materials are efficient UV absorbers and they are able to destroy biological aggressors also. Nowadays, there is no information about the interactions between wooden surface and non-photoactive or photoactive forms of TiO2. TiO2 exists in many morphological forms. The planar particles were chosen for the purpose of our research and applied on a wooden surface. The samples of wood (namely pine) were monitored for 255 days and subsequently evaluated using an electron microscope. The use of TiO2 was compared with reference material and a reference commercial coating.
37
Khitab, Anwar, Sajjad Ahmad, Riaz Akhtar Khan, Muhammad Tausif Arshad, Waqas Anwar, Junaid Tariq, Ali Sikandar Rasheed Khan, Raja Bilal Nasar Khan, Affan Jalil, and Zeesshan Tariq. "Production of Biochar and Its Potential Application in Cementitious Composites." Crystals 11, no. 5 (May 10, 2021): 527. http://dx.doi.org/10.3390/cryst11050527.
Abstract:
In cement composites, usually, reinforcement is provided to restrict the crack development and their further propagation under service conditions. Typically, reinforcements utilized in cementitious composites range from nanometer scale to millimeter scale by using nano-, micro-, and millimeter-sized fibers and particles. These reinforcements provide the crack arresting mechanisms at the nano/microscale and restrict the growth of the cracks under service loads, but usually, the synthesis of nano/microfibers, and afterward their dispersion in the cementitious materials, pose difficulty, thus limiting their vast application in the construction industry. Carbonaceous inerts are green materials since they are capable of capturing and storing carbon, thus limiting the emission of CO2 to the atmosphere. In the present study, a comprehensive review of the synthesis of low cost and environmentally friendly nano/micro carbonaceous inerts from pyrolysis of different agricultural/industrial wastes, and afterward, their application in the cementitious materials for producing high performance cementitious composites is presented, which have the potential to be used as nano/micro reinforcement in the cementitious matrix.
38
Yang, Zhi Bo, Gui Bin Zhang, and Jiu Hua Xu. "Thermodynamic Analysis of Interfacial Reaction between Diamond and Ni-Cr Alloys." Applied Mechanics and Materials 42 (November 2010): 440–43. http://dx.doi.org/10.4028/www.scientific.net/amm.42.440.
Abstract:
Brazing diamond grits to steel substrate using Ni-based filler alloy was carried out via laser in an argon atmosphere. Thermodynamic analysis was performed in order to research the interfacial reaction mechanism of diamond and Ni-Cr alloy during high temperature brazing. Meanwhile, microstructure of the interfacial layer was experimentally detected by scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD) in this paper. The results indicate that according to the thermodynamic theory the interfacial reaction has been proved feasible, and during brazing high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product Cr3C2, and the bond between the alloy and the Diamond was established through the reaction product.
39
Zhao, Xing Yu, Jing Tao Ma, Yong Gao, Shao Chang Hao, Chang Sheng Deng, Bing Liu, and Ya Ping Tang. "Preparation of UCO Microspheres by Internal Gelation Process." Key Engineering Materials 697 (July 2016): 831–34. http://dx.doi.org/10.4028/www.scientific.net/kem.697.831.
Abstract:
UCO kernels were used for High Temperature Reactor (HTR) fuel, which can restrain kernels migration and avoid corrosion of cladding layer under the high burnup compared with UO2 or UC kernels. In this paper, UCO kernels were prepared by internal gelation process containing dissolving, broth preparation, dispersing, AWD (aging, washing and drying) and sintering procedures. The broth composition was studied based on the fabrication of UO2 kernels before. Effects of the carbon black content and sintering atmosphere on the microstructure and performance of microspheres were mainly studied. Surface morphology of dried microsphere was observed by integrated microscope. Grain size and the degree of densification of UCO microspheres were observed by SEM.
40
Kim, Ji-Won, Sung-Gap Lee, Kyeong-Min Kim, Ji-Su Yuk, and Joo-Seok Park. "Structural and Electrical Properties of K(Ta, Nb)O3 Thin Films with the Variation of Sintering Temperature." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 7158–62. http://dx.doi.org/10.1166/jnn.2020.18852.
Abstract:
In this study, KTa0.55Nb0.45O3 (KTN) thin films were manufactured by using Chemical Solution Deposition (CSD) method with variations in the sintering temperature and were investigated in order to apply their applicability in memory devices. The KTN thin films were made after coating the PZT bufferlayer on Pt/Ti/SiO2/Si substrate. Each layer was dried at 200°C for 5 min to remove any organic materials and pyrolyzed at 400°C for 10 min. Finally, the layers were sintered for 30 min under an oxygen atmosphere, respectively. The pattern of KTN thin films showed a preference to the (100) and (200) orientations. Also, an increase in the sintering temperature caused the KTN crystalline peak intensities to also increase. When looking at the results from the Scanning Electron Microscope and Atomic Force Microscope data, the average grain size and root mean square roughness (Rrms) of KTN thin films were 109~157 nm and about 4 nm, respectively. Typical dielectric dispersion characteristics were observed in which the dielectric constant decreases with an increase of the applied frequency. The specimen sintered at 750°C showed the highest dielectric constant of 769 at 1 kHz.
41
Ribeiro, Helena, Paula Castro, and Ilda Abreu. "Characterization of the Pollen Trapped by Populus L. Seeds during the Dispersion Season." Aerobiology 2, no. 1 (February 7, 2024): 18–28. http://dx.doi.org/10.3390/aerobiology2010002.
Abstract:
Our study aimed to quantify the pollen trapped by the seeds and relate it with the airborne pollen concentrations. Individual Populus spp. tuft-like seeds were sampled while suspended twice a day in 2017 and 2018 during the seed dispersal season. The seeds were submitted to laboratory treatment for pollen extraction, which was quantified using an optical microscope. Airborne pollen was monitored using a seven-day Hirst-type volumetric spore sampler. A correlation analysis was performed between the airborne pollen, the pollen on the seeds, and the meteorological parameters. A total of 26 pollen grains/mg was counted in the airborne tuft-like seeds, with 26 different taxa being identified, compared with the 18 pollen taxa identified in the airborne samples. Quercus, Poaceae, Urticaceae, Pinus, and Platanus were the most frequent pollen found on the seeds, while in the atmosphere, pollen from Urticaceae, Quercus, and Cupressaceae were the most representative. A tendency of higher pollen concentrations found in the afternoon samples, both airborne and on the seeds, was observed. Correlations between the meteorological parameters and pollen concentration found airborne and in the seeds were overall not significant. Thus, airborne poplar tuft-like seeds can trap and transport pollen, most of which has been recognized to induce respiratory allergies.
42
Huffman, Donald R., Benjamin E. Swanson, and J. Alex Huffman. "A wavelength-dispersive instrument for characterizing fluorescence and scattering spectra of individual aerosol particles on a substrate." Atmospheric Measurement Techniques 9, no. 8 (August 23, 2016): 3987–98. http://dx.doi.org/10.5194/amt-9-3987-2016.
Abstract:
Abstract. We describe a novel, low-cost instrument to acquire both elastic and inelastic (fluorescent) scattering spectra from individual supermicron-size particles in a multi-particle collection on a microscope slide. The principle of the device is based on a slitless spectroscope that is often employed in astronomy to determine the spectra of individual stars in a star cluster but had not been applied to atmospheric particles. Under excitation, most commonly by either a 405 nm diode laser or a UV light-emitting diode (LED), fluorescence emission spectra of many individual particles can be determined simultaneously. The instrument can also acquire elastic scattering spectra from particles illuminated by a white-light source. The technique also provides the ability to detect and rapidly estimate the number fraction of fluorescent particles that could contaminate a collection of non-fluorescent material, even without analyzing full spectra. Advantages and disadvantages of using black-and-white cameras compared to color cameras are given. The primary motivation for this work has been to develop an inexpensive technique to characterize fluorescent biological aerosol particles, especially particles such as pollen and mold spores that can cause allergies. An example of an iPhone-enabled device is also shown as a means for collecting data on biological aerosols at lower cost or by utilizing citizen scientists for expanded data collection.
43
Khakan, Behruz, Abbas Shahroozi, Ahmad Afsari, and Seyed Reza Hosseini. "Investigation of stearic acid additive effects on the mechanochemical synthesis of silver nanoparticles." Powder Diffraction 32, no. 2 (February 28, 2017): 93–96. http://dx.doi.org/10.1017/s0885715617000203.
Abstract:
The silver (Ag) powder was synthesized in a mechanochemical (MC) process by inducing a solid-state displacement reaction between silver chloride (AgCl) and copper (Cu). This process was carried out in argon atmosphere conditions using a planetary ball mill. The reaction caused the mixture of AgCl and Cu to change the composition of the mixture to Ag and copper chloride (CuCl). CuCl was separated from MC product by leaching with ammonium hydroxide. Thus, Ag powder was obtained as the final product. Stearic acid (C18H36O2) was used as the additive to improve dispersion of Ag powder during the MC process. The ground powders, formed in the presence and absence of additive, were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD determined that the reaction between AgCl and Cu was completed in 18 h milling. SEM and particle size analysis examinations revealed that the size of the particles in the synthesized metallic Ag powder was in the range of 30–300 nm.
44
Yang, Zhi Bo, Ai Ju Liu, and Jiu Hua Xu. "Joining of Diamond Grains to Medium Carbon Steel with Ni-Base Powder during Laser Brazing." Key Engineering Materials 455 (December 2010): 392–96. http://dx.doi.org/10.4028/www.scientific.net/kem.455.392.
Abstract:
In order to develop new generation brazed Diamond grinding wheels, the joining experiments of Diamond super abrasive grains and medium carbon steel using the powder mixture of Ni-Cr alloy as active brazing alloy are carried out via laser in an argon atmosphere. The relevant characteristics of the special powder mixture, the microstructure of the interfacial region, which are both the key factors for determining the joining strength among the Diamond grains, the filler layer and the steel substrate, are investigated extensively by means of scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis. The formation mechanism of carbide layers was discussed. All the results indicate that high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product Cr3C2, and the bond between the alloy and the Diamond was established through the reaction product.
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Abudalazez, Asam M. A., Shah Rizal Kasim, Azlan B. Ariffin, and Zainal Arifin Ahmad. "Electrophoretic Deposition of Biphasic Calcium Phosphate (BCP) Coatings on 316L Stainless Steel at Room Temperature." Advanced Materials Research 501 (April 2012): 169–75. http://dx.doi.org/10.4028/www.scientific.net/amr.501.169.
Abstract:
Electrophoretically deposition of Biphasic calcium phosphate on 25 × 10 × 1.2 mm (length, width, and thickness) 316L stainless steel plates using ethanol as dispersing medium; It was achieved on the cathode with constant voltages 20, 30, 50, and 100 V during 20, 30, 60, 90 and 120 seconds, respectively. After deposition, the samples were dried at room temperature for 24 hours and deposition weight and thickness of the coatings were measured. The coated samples were sintered in a tube furnace at 800 °C for 1 h in an argon atmosphere. After the sintering, the surface morphology and structure and phase composition of the samples were studied by a scanning electron microscope (SEM), energy dispersive spectrometry (EDX) and phase purity of the coating material by X-ray diffraction.
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Huseynov, Asgar, Aydin Israfilov, Samira Mammadova, Sevda Abdullayeva, Sergey Sokolov, Alexey Goryunkov, and Akif Guliyev. "Fabrication and characterization of MWCNT/natural Azerbaijani bentonite electroconductive ceramic composites." Journal of Composite Materials 53, no. 26-27 (May 13, 2019): 3909–23. http://dx.doi.org/10.1177/0021998319848798.
Abstract:
Multi-walled carbon nanotubes have been synthesized by Aerosol-Chemical Vapor Deposition method. Carbon nanotubes firstly have been used as filler in affordable and prevalent natural Azerbaijani bentonite clays for fabrication electroconductive ceramic composites. In this paper, multi-walled carbon nanotubes/natural Azerbaijani bentonite ceramic composites were prepared by two-factor mechanical method and followed by calcination at 1050℃ in an inert atmosphere. The ceramic composites were characterized by scanning electron microscope, atomic force microscope, X-ray diffraction and thermogravimetric-differential-thermal analysis. X-ray diffraction analysis confirmed the presence of two principal components – multi-walled carbon nanotube and bentonite in composites. From the thermogravimetric-differential-thermal data, it was revealed that multi-walled carbon nanotube/ bentonite ceramic composites demonstrate thermo-oxidative stability up to 580–640℃. Scanning electron microscope images demonstrated a sufficiently high dispersibility of carbon nanotubes and satisfactory homogeneity in the composites. Experimental results demonstrated that by increasing the mass fraction of multi-walled carbon nanotubes from 1% to 8% in multi-walled carbon nanotube/bentonite ceramic composites, the electrical conductivity enhances substantially. The enhancement of electrical conductivity of the composites explained the mass fraction of multi-walled carbon nanotubes, as well as the uniform dispersion of multi-walled carbon nanotubes in the bentonite clays. Compared with other 8% multi-walled carbon nanotubes/bentonite ceramic composites, the electrical conductivity of heptane-multi-walled carbon nanotube/Gobu bentonite (σ = 397 S·m−1) and heptane-multi-walled carbon nanotubes/Atyali (σ = 305 S·m−1) composites is 2–5 times higher than the conductivity of composites obtained with cyclohexane carbon nanotubes- cyclohexane-multi-walled carbon nanotube/Atyali (σ = 78 S·m−1), cyclohexane-multi-walled carbon nanotube/Gobu (σ = 111,5 S·m−1). These results can be explained with the structure, the number of layers, purity and diameter distribution, as well as the type and amount of defects in internal and external layers of Hep-multi-walled carbon nanotubes which cause better dispersion in bentonite clays. Due to the high conductivity and high temperature stability, these composites can be used as promising material for fabrication heating elements, electrodes, substrates for microelectronic devices, etc.
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Zhang, Shu Hua, Wen Jun Gan, Wu Xing Sun, Chen Jun Ling, Xie Wang, and Qing Feng Li. "Study on Structures and Properties of CaSO4 Whiskers/PVC Composites." Advanced Materials Research 335-336 (September 2011): 234–39. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.234.
Abstract:
Structures of CaSO4 whisker(A) and CaSO4 whisker(B) were characterized by IR and XRD, and the morphologies were observed by optical microscope. The results showed that the modified CaSO4 whisker(B) has perfect crystal structure, high crystallinity and less defects. Mechanical properties and static thermal stability time(190 °C) of two composites which were prepared by CaSO4 whisker(A) / PVC and CaSO4 whisker(B) / PVC were tested separately, and the degradation processes were analyzed by TG at 50 °C-400°C, N2 atmosphere, and the dispersing states of two whiskers in the composites were observed by means of optical microscope and SEM. The research results showed that the tensile strength and elongation at break increased over 3 MPa and 40% separately, and the static thermal stability time was over 90 min of CaSO4 whisker(B) / PVC, the initial degradation time was delayed comparing with CaCO3 / PVC composite. The consistency and interfacial configuration between whisker and PVC resin were perfect, and the toughness and thermal stability of the composite was improved after CaSO4 whisker was modified. The research results indicated that modified CaSO4 whisker has better toughness and thermal stability actions for PVC.
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Kawasaki, Masahiro, Tadanori Yoshioka, Shigeki Sato, Kazuto Watanabe, and Makoto Shiojiri. "Boundary Analysis Of SrTio3 Ceramic Condenser." Microscopy and Microanalysis 5, S2 (August 1999): 154–55. http://dx.doi.org/10.1017/s1431927600014094.
Abstract:
SrTiO3-based semiconducting ceramics are widely used to electric devices such as dielectric condensers and varistors due to their properties of high dielectric constant, high dispersion frequency and small temperature dependence of the dielectric constant. The electric properties of these ceramic devices have been studied and found to be deeply influenced by the crystal growth mechanism, the grain boundary layer characteristics and the sintering atmosphere that is represented by such factors as oxygen partial pressure and processing temperature which relate to the atom vacancy formation. Atom vacancies, which play an important role to the electrical properties, have been detected by cathodoluminescence (CL) spectroscopy with scanning electron microscopy (SEM).A ceramic condenser (Sr0.94Ca0.05Ba0.01)0.99TiO3 was investigated by Hitomi el at: using transmission electron microscopy (TEM). The material is a boundary layer (BL) semiconducting ceramic condenser, having dielectric layers between semiconducting grains. The same condenser material was investigated in this report at the grain boundary region using high resolution (scanning) transmission electron microscope (TEMSTEM) capable of High Angle Annular Dark Field (HAADF) technique.
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Amirbekova, G. S., Zh K. Tolepov, N. Guseinov, M. A. Tulegenova, B. G. Orynbai, T. Koshtybayev, and Zh Otarbay. "CONTROL OF THE SIZES OF LEAD SULFIDE (PBS) NANOPARTICLES BY PLASMA TREATMENT METHOD." Herald of the Kazakh-British technical university 21, no. 2 (July 2, 2024): 266–72. http://dx.doi.org/10.55452/1998-6688-2024-21-2-266-272.
Abstract:
In this work, the optimal parameters for the production of lead sulfide nanoparticles (PbS) were determined. Lead sulfide nanoparticles were obtained by chemical precipitation in an aqueous solution of lead nitrate (Pb(NO3 )2 ) 25 ml 0.18 M (1.524 g), sodium hydroxide (NaOH) 75 ml 0.38 M (1.172 g), thiourea (CH4 N2 S) 50 ml 0.11 M (0.399 g), at a reaction temperature of 100 °C, the duration of the synthesis reaction was 120 minutes. The particles were deposited on a pre-purified silicon (Si) substrate. After synthesis, the particles were processed in a glow discharge plasma in an argon atmosphere at a pressure of the order of Ð=1 Pa, for t1 =1min and U = 2 min, at a voltage ofU = 2 kV and a current strength of I =1,5 mA. The morphology of the obtained structures was studied using a scanning electron microscope (SEM), the elemental composition of the particles was determined by energy dispersion analysis (EDX). Plasma treatment reduces the average particle size from the submicron to the nanometer range.
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Huang, Siyi, Qi Lu, Xiaorui Ma, Yunwen Chen, and Reziya Maimaiti. "A Facilely Synthesized Tourmaline–Biochar Composite for Enhanced Removal of Cr (VI) from Aqueous Solution." Atmosphere 13, no. 10 (October 9, 2022): 1643. http://dx.doi.org/10.3390/atmos13101643.
Abstract:
Hexavalent chromium (Cr (VI)), an anthropogenic heavy metal pollutant, is harmful to human beings, due to its carcinogenicity. In this study, a tourmaline–biochar composite (TMBC) was synthesized to remove Cr (VI) from an aqueous solution. The effects of different ratios (TM:BC) and pyrolysis temperatures on TMBC adsorption performance were compared. The TMBC samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope–energy-dispersive spectrometry (SEM-EDS). The kinetics and thermodynamics were analyzed to investigate the sorption mechanism. The results showed that the proper pyrolysis temperature was 650 °C, and the ratio of TM:BC was 1:3. SEM results showed the TM was well attached to the BC which assisted tourmaline dispersion. The adsorption kinetics were well fitted by the pseudo-second-order model, indicating that the sorption was related to chemical absorption. Langmuir adsorption isotherms suggested monolayer adsorption between the Cr (VI) and the TMBC, and the maximum adsorption capacity of the TMBC for Cr (VI) was 43.64 mg/g, which was more than twice the amount for the pristine TM (17.84 mg/g). The automatic polarization of water caused by tourmaline was the unique adsorption property of the TMBC. Therefore, TMBCs can be used as an economic adsorbent in the remediation of heavy metal pollution.