Plume Dispersion Research Articles

The Environmental Effects of the April 2020 Wildfires and the Cs-137 Re-Suspension in the Chernobyl Exclusion Zone: A Multi-Hazard Threat

This paper demonstrates the environmental impacts of the wildfires occurring at the beginning of April 2020 in and around the highly contaminated Chernobyl Exclusion Zone (CEZ). Due to the critical fire location, concerns arose about secondary radioactive contamination potentially spreading over Europe. The impact of the fire was assessed through the evaluation of fire plume dispersion and re-suspension of the radionuclide Cs-137, whereas, to assess the smoke plume effect, a WRF-Chem simulation was performed and compared to Tropospheric Monitoring Instrument (TROPOMI) satellite columns. The results show agreement of the simulated black carbon and carbon monoxide plumes with the plumes as observed by TROPOMI, where pollutants were also transported to Belarus. From an air quality and health perspective, the wildfires caused extremely bad air quality over Kiev, where the WRF-Chem model simulated mean values of PM2.5 up to 300 µg/m3 (during the first fire outbreak) over CEZ. The re-suspension of Cs-137 was assessed by a Bayesian inverse modelling approach using FLEXPART as the atmospheric transport model and Ukraine observations, yielding a total release of 600 ± 200 GBq. The increase in both smoke and Cs-137 emissions was only well correlated on the 9 April, likely related to a shift of the focus area of the fires. From a radiological point of view even the highest Cs-137 values (average measured or modelled air concentrations and modelled deposition) at the measurement site closest to the Chernobyl Nuclear Power Plant, i.e., Kiev, posed no health risk.

Dispersion and impact of smoke plumes from industrial fires: the case of Lubrizol

Dispersion and impact of smoke plumes from industrial fires: the case of Lubrizol

Characterising industrial thermal plumes in coastal regions using 3-D numerical simulations

Coastal power stations use sea water as a coolant, releasing it back into coastal environments at a higher-than-ambient temperature. Due to the possible ecological impacts on sensitive coastal zones, thermal plume formed by warmer coolant waters needs to be monitored, which is typically done through field campaigns. This paper assesses the use of simulations and remotely sensed observations as complimentary methods to characterise plume behaviour for a chosen coastal power station located within an inter-tidal embayment. Simulations of the thermal plume for two main tide phases and associated sea current conditions are validated against the high-resolution satellite observations. Simulated plume temperatures are higher than the observed values, with the biggest difference of 2 °C. The direction of the simulated plume dispersion is in agreement with observations and depends on the strength and direction of sea currents associated with the phase of the tide. The plume stretches most at the surface with limited impact on the benthic temperatures.

Improving spatial resolution of PM2.5 measurements during wildfires

This study proposes an approach to improve the spatial resolution of ground-level concentrations of PM2.5 that is required to assess health risks associated with exposure to pollutants released during wildfires. We use this approach to analyze the impact on air quality of the wildfire complex consisting of the Atlas, Nuns, Tubbs, Pocket, and Redwood Valley fires in northern California that started on October 8, 2017 and the Camp Fire in northern California that was first reported on November 8, 2018. The PM2.5 concentrations measured in populated areas downwind of these fires were well above the 24-h standard of 35 μg/m3 during several days of both fires. To estimate health risks at locations where ground-based monitors did not provide sufficient spatial coverage we first estimate the emissions from the fires by fitting concentration estimates from two models, a Lagrangian model and a segmented plume dispersion model, to corresponding concentrations from ground monitors. We also use a power law model to fit the measured PM2.5 concentrations to the ratio of aerosol optical depth (AOD) to planetary boundary layer measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) carried by NASA's Terra and Aqua satellites. Dispersion model estimates are then combined with estimates from the AOD model to compute ground-level concentrations at a resolution of 1 km. Kriged residuals between estimates from the combined model and measured PM2.5 concentrations are then added to obtain high resolution maps that can be used for exposure studies.

Dispersion Plumes in Open Ocean Disposal Sites of Dredged Sediment

Management of estuarine systems under anthropogenic pressures related to port settlement and development requires thorough understanding about the long-term sediment dynamics in the area. In an era of growing shipping traffic and of ever larger ships; millions of tons of bottom sediments are dredged annually all over the world and the major question concerning dredging operations is not whether they should be done, because it is obvious that they are extremely important and necessary, but where the dredged sediments can be disposed of with the least possible ecological impact. The present study involves the evaluation of transport trends of dredged material from a turbid estuary disposed of in four different open ocean disposal sites using numerical model techniques, aiming to contribute to minimizing potential environmental impacts and maximizing efficiency of the dredging operation. The study is carried out in southern Brazil, investigating the fate of dredged material from the Port of Rio Grande, located inside the Patos Lagoon estuary. Simulations were carried with the TELEMAC-3D model coupled with the suspended sediment (SEDI-3D) module and incorporating results from the wave module (TOMAWAC) to evaluate the dispersion of the suspended sediment plume and its interaction with coastal currents. This modeling structure proved to be a valuable tool to study the hydrodynamics and sediment transport pathways in estuarine and coastal areas. Results indicate that the natural Patos Lagoon coastal plume was observed under the predominant ebb flows and NE winds, promoting fine sediment entrapment south of the mouth of the lagoon (in front of Cassino Beach). The dispersion plumes in the disposal sites responded to the wind intensity and direction and did not present any transport tendency towards Cassino Beach. Part of the dredged sediment disposed of in the proposed alternative sites located in deeper areas (Sites B and C) left the site and was transported parallel to the coast (SW–NE direction) according to the wind direction (NE–SW). The area where the disposal sites were located took around 4 days to recover from the dredging operation and reach the usual suspended sediment concentrations and the actual Port of Rio Grande Licensed Site for dredged material proved to be the best alternative among the investigated options.

An urban large-eddy-simulation-based dispersion model for marginal grid resolutions: CAIRDIO v1.0

Abstract. The ability to achieve high spatial resolutions is an important feature for numerical models to accurately represent the large spatial variability of urban air pollution. On the one hand, the well-established mesoscale chemistry transport models have their obvious shortcomings due to the extensive use of physical parameterizations. On the other hand, obstacle-resolving computational fluid dynamics (CFD) models, although accurate, are still often too computationally intensive to be applied regularly for entire cities. The major reason for the inflated computational costs is the required horizontal resolution to meaningfully apply obstacle discretization, which is mostly based on boundary-fitted grids, e.g., the marker-and-cell method. In this paper, we present the new City-scale AIR dispersion model with DIffuse Obstacles (CAIRDIO v1.0), in which the diffuse interface method, simplified for non-moving obstacles, is incorporated into the governing equations for incompressible large-eddy simulations. While the diffuse interface method is widely used in two-phase modeling, this method has not been used in urban boundary-layer modeling so far. It allows us to consistently represent buildings over a wide range of spatial resolutions, including grid spacings equal to or larger than typical building sizes. This way, the gray zone between obstacle-resolving microscale simulations and mesoscale simulations can be addressed. Orographic effects can be included by using terrain-following coordinates. The dynamic core is compared against a standard quality-assured wind-tunnel dataset for dispersion-model evaluation. It is shown that the model successfully reproduces dispersion patterns within a complex city morphology across a wide range of spatial resolutions tested. As a result of the diffuse obstacle approach, the accuracy test is also passed at a horizontal grid spacing of 40 m. Although individual flow features within individual street canyons are not resolved at the coarse-grid spacing, the building effect on the dispersion of the air pollution plume is preserved at a larger scale. Therefore, a very promising application of the CAIRDIO model lies in the realization of computationally feasible yet accurate air-quality simulations for entire cities.

Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation part 6: introduction of detailed dose calculation method

ABSTRACT We developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) for the safety assessment of nuclear facilities and emergency responses to accidental or deliberate releases of radioactive materials. In parts 1–5 of this series, the basic performance was examined by comparing with wind tunnel or field experimental results on plume dispersion over various complex surface geometries under ideal and realistic atmospheric conditions. In this study, we introduced a dose calculation method that can simulate air dose rate distributions by considering shielding effects and inhomogeneous distribution of radioactive materials in the air and on the ground and building surfaces. First, we conducted LESs of radioactive plume dispersion and dry deposition in building array and investigated the basic performance of the dose calculation method by comparison with that of Monte-Carlo based three-dimensional radiation transport simulations by Particle and Heavy-Ion Transport code System (PHITS). Then, we compared the LOHDIM-LES results with actual air dose rate obtained from the monitoring posts in a nuclear facility. The observed data were reasonably simulated. Thus, we completed LOHDIM-LES, which can simulate plume dispersion, dry deposition, and air dose rates from complex distributions of radionuclides considering the influence of individual buildings under realistic meteorological conditions.

Heavy Metal and Mineral Composition of Soil, Atmospheric Deposition, and Mosses with Regard to Integrated Pollution Assessment Approach.

The fact that there are no real borders between the biosphere, atmosphere, lithosphere, and hydrosphere means that environmental pollution monitoring studies should not only include one of the environmental spheres. Thus, integrated environmental pollution assessment studies conducted in the biosphere, lithosphere, and atmosphere promote the "whole system" approach. In this study, the aim was to determine the pollution in the atmosphere, soil, and plants by taking advantage of the high pollution accumulation characteristics of the mosses. Prevailing wind has the potential to distribute pollutants emitted into the air throughout its path. With this regard, soil, mosses, and atmospheric deposition samples were collected in Çanakkale, Turkey, in two seasons. Concentrations of selected elements were measured by Inductively Coupled Plasma-Mass Spectrometry. The enrichment factor of the selected elements in the soil, moss, and deposition samples was calculated. The highest enrichments were found for Lead in atmospheric deposition, Arsenic in soil, and Mercury in moss samples. Cobalt and chromium accumulated more in mosses than in soil. Elevated arsenic levels found in the samples can pose a great risk for public health and agriculture. The study result showed that the elemental composition of the samples was influenced by the enhanced air plume dispersion of anthropogenic pollution sources along the Northeast-Southwest directions due to wind characteristics in the province. As expected, strong correlations were found among the moss, soil, and atmospheric deposition samples indicating the vital interactions between the environmental components.

A fuzzy classification of the hydrodynamic forcings of the Rhone River plume: An application in case of accidental release of radionuclides

Assessing and modelling the coastal plume dispersion of nuclearized rivers is strategic in case of accidental releases, but taking into account the variation of main hydrodynamic forcings is challenging. This study uses fuzzy c-mean clustering of a 10 years series of discharge and wind speed at the Rhone River estuary (France) in order to explain the variability of its plume. The method allows to classify the data into 6 scenarios of hydrodynamic forcings that were related to different spatial extensions of the plume, as well as to surface currents measured in-situ. These scenarios were used to simulate the extension and dilution of a radioactive release issued from the river. Based on threshold values of the forcings, a decisional tree is proposed to provide a quick decision tool identifying, in real time, which climatological scenario occurs at the river mouth and the potential plume pattern.

Study of three domestic sewage submarine outfall plumes through the use of numerical modeling in the São Sebastião channel, São Paulo state, Brazil

The dispersion of the thermotolerant coliform plumes emitted from the Araçá, Itaquanduba and Cigarras domestic sewage submarine outfalls in the São Sebastião Channel was modeled. The plumes were simulated as the only pollution sources considering bacterial decay for the summer and winter of 2016. The main goal was to determine if and which areas were impacted by the disposal systems. The simulated concentrations were quantitatively compared with Enterococcus and thermotolerant coliform data provided by sanitation agencies in São Paulo state (CETESB and SABESP). The UM3 model from Visual Plumes software and the ECOM were used as the near-field and far-field models, respectively. The ECOM was configurated with 37 sigma levels and its horizontal resolution varies from 0.2 km to 5 km. The modeled concentrations did not exceed the limit stated by CONAMA Resolution 274 (2000), with the exception of that in June 2016. The main conclusion of this study is that channel hydrodynamic patterns are sufficient to disperse the plumes from sewage disposal outfalls. The areas adjacent to Araçá outfall presented the highest persistence of coliform concentrations; however, the modeled concentrations did not exceed 1000 MPN/100 mL for more than 0.1% of the time. The simulations satisfactorily reproduced the coliform variability and dispersion in the region.

A Study on Plume Dispersion Characteristics of Two Discrete Plume Stacks for Negative Temperature Gradient Conditions

The dispersion of air pollutants emitted from industries has been studied ever since the dawn of industrialisation. The present work focuses on investigating the effect of negative atmospheric temperature gradient and the plume stack orientation of two individual equal-height stacks on the vertical rise and dispersion of the plume. The study carried out upon three-stack layout configurations namely inline, 45° and non-inline, separated by an inter-stack distance of 12 times the exit chimney diameter (12 D) and 22 times the exit chimney diameter (22 D) in each case over the two temperature gradients of −0.2 K/100 m and −0.5 K/100 m. The turbulence is modelled using realisable k-ε model, a model used in the FLUENT flow solver. In the case of the inline configuration, the upwind plume shields its downwind counterpart, which in turn allows for higher plume rise at a given temperature gradient. The plume oscillates more in the case of inline than 45° and non-inline cases. Also, for a temperature gradient of −0.5 K/100 m, the plumes oscillate violently in the vertical direction, mainly because, with the initial rise of the plume, cold air from higher altitudes moves down and forms a layer of lower temperature closer to the ground. The present study is important to highlight the plume dispersion characteristics under negative temperature gradient conditions.

Experimental characterization and real-time monitoring for laser percussion drilling in titanium alloy using transverse electric field assistance and/or lateral air blowing

A novel laser percussion drilling technology assisted by an electric field with lateral air blowing is reported. The lateral air blowing is first proposed for assisting the E-field assisted laser drilling for improving hole-drilling performance, quality and efficiency by blowing away the vapor plume and cooling the target workpiece. A high-speed camera is first used for observing and characterizing the transient laser percussion drilling process with and without an electric field and/or a lateral airflow. It was indicated that the transverse electric force and/or the side air blowing expedited the spatial motion with dispersion and density reduction of the vapor-plasma plume for enhancing laser drilling efficiency via weakening the plume-induced shield effect. The recast layer was reduced by using the transverse E-field assistance with and without lateral air blowing, and the combined assistance of a transverse E-field together with a lateral airflow was more effective for reducing the recast layer. Interestingly, as a result of the dynamic air cover across the sample surface induced by the lateral air blowing, the laser-vapor interaction inside a drilling hole was greatly enhanced together with the laser-material interaction, leading to the rapidly-accumulated expansion and then the sudden explosion of the laser-induced plume inside a drilling hole. The enhanced vertical scouring and flowing effect resulting from the accelerated vertical plume-motion inside a drilling hole, which was caused by the accumulated pressure difference inside and outside of the hole due to the enhanced outside motion-dispersion effect (especially induced by the electric force) of the plasma-vapor plume, expedited the uniform molten material removal and distribution along the hole sidewall. Importantly, a transverse E-field with and without a side airflow effectively refined the grains of the heat affected zone (HAZ) near the fusion zone of a through hole via increasing the average grain size number. The micro hardness was improved after laser hole-drilling by loading a transverse E-field with and without a side airflow due to a grain refinement effect with and without an airflow cooling effect. It was demonstrated that the lateral air blowing used was more effective to increase laser drilling efficiency for drilling through the workpiece than the E-field used, and the hole-drilling efficiency was further increased if using the combined assistance of a transverse E-field and a side airflow. After the workpiece was drilled through, the hybrid plume signal was effectively suppressed primarily above the hole entrance by using a transverse E-field and/or a side airflow, especially in case of using the transverse E-field assistance.

Experimental investigations on scale-dependent dispersivity in three-dimensional heterogeneous porous media.

The relationship between the scale-dependent dispersivity and heterogeneous sedimentary structures is investigated through conducting non-reactive tracer experiments in a three-dimensional heterogeneous sand tank. The heterogeneous porous media consists of three sedimentary facies of silty, fine, and medium sands collected from the west of the Songnen Plain, China. Moreover, several corresponding individual facies soil columns were constructed for comparison. A conservative tracer was continuously injected from an upstream source. The effective parameters were estimated by inverse modeling of a one-dimensional transport model. The results show that the scale dependence of the estimated dispersivities was discovered in the individual facies column (with relatively weaker effect) and the heterogeneous porous media (with more significant effect). With increasing transport distances, the dispersivities of the individual facies tend to reach an asymptotic value, while those of the heterogeneous media increase continuously. Furthermore, the results show that a power function can describe the relationship between effective dispersivities and transport distances. The exponent of the function is greater than one for the heterogeneous media, but less than one for the individual facies. The results also indicate that the dispersion plume is macroscopically dominated by the distribution of facies. The heterogeneity of hydraulic conductivity causes the variations of flow velocity, which further enhances the scale dependence of dispersivities. The tracer experiment in heterogeneous media provides the fundamental insight into the understanding of contaminant transport processes.

Encountering shoaling internal waves on the dispersal pathway of the pearl river plume in summer

Fundamentally, river plume dynamics are controlled by the buoyancy due to river effluent and mixing induced by local forcing such as winds and tides. Rarely the influence of far-field internal waves on the river plume dynamics is documented. Our 5-day fix-point measurements and underway acoustic profiling identified hydrodynamic processes on the dispersal pathway of the Pearl River plume. The river plume dispersal was driven by the SW monsoon winds that induced the intrusion of cold water near the bottom. The river effluent occupied the surface water, creating strong stratification and showing on-offshore variability due to tidal fluctuations. However, intermittent disruptions weakened stratification due to wind mixing and perturbations by nonlinear internal waves (NIWs) from the northern South China Sea (NSCS). During events of NIW encounter, significant drawdowns of the river plume up to 20 m occurred. The EOF deciphers and ranks the contributions of abovementioned processes: (1) the stratification/mixing coupled by wind-driven plume water and NIWs disruptions (81.7%); (2) the variation caused by tidal modulation (6.9%); and (3) the cold water intrusion induced by summer monsoon winds (5.1%). Our findings further improve the understanding of the Pearl River plume dynamics influenced by the NIWs from the NSCS.

Evaluation of Radiation Doses for Hypothetical Accident Scenarios of Egyptian Second Research Reactor

Inshas site is very important site, it is considered as a first nuclear site in Egypt. It contains the first and the second research reactors and other important facilities such as the Egyptian Fuel Manufacturing Pilot Plant (FMPP) which submits the fuel to the second research reactors. The goals of this paper are to assess different emergency plan scenarios, determine the effects of metrological conditions on the dispersion of the radioactive plume, and calculate the overall effective dose equivalent values (TEDE). The meteorological parameters for one complete year 2020 (hourly) meteorological data were analysed in details such as wind direction, wind speed and temperature. The HotSpot code was used to model atmospheric dispersion and its application resulted in a radiation dose profile around the site using meteorological parameters specific to the area under study. This study used more than one scenario to investigate the role of various meteorological parameters. The radionuclide source term of Cs-137 was assumed to be 2.10E+15Bq. The results show that the maximum dose form all postulated scenarios is about 1.1E+4 Sv is observed at 10 m from the release source for weather stability class F, which is greater than the IAEA occupational exposure limit of 0.02 Sv per year. The results can also show that the time of accident is a major effect on the impact of accident and then on the consequences of emergency plan.

Reconstructing Eruption Plume and Tephra Dispersal Using Simulation and Inversion Techniques: A Review Focusing on Recent Studies Using Tephra2 and WT

Reconstructing Eruption Plume and Tephra Dispersal Using Simulation and Inversion Techniques: A Review Focusing on Recent Studies Using Tephra2 and WT

Particle aging and aerosol–radiation interaction affect volcanic plume dispersion: evidence from the Raikoke 2019 eruption

Abstract. A correct and reliable forecast of volcanic plume dispersion is vital for aviation safety. This can only be achieved by representing all responsible physical and chemical processes (sources, sinks, and interactions) in the forecast models. The representation of the sources has been enhanced over the last decade, while the sinks and interactions have received less attention. In particular, aerosol dynamic processes and aerosol–radiation interaction are neglected so far. Here we address this gap by further developing the ICON-ART (ICOsahedral Nonhydrostatic – Aerosols and Reactive Trace gases) global modeling system to account for these processes. We use this extended model for the simulation of volcanic aerosol dispersion after the Raikoke eruption in June 2019. Additionally, we validate the simulation results with measurements from AHI (Advanced Himawari Imager), CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), and OMPS-LP (Ozone Mapping and Profiling Suite-Limb Profiler). Our results show that around 50 % of very fine volcanic ash mass (particles with diameter d<30 µm) is removed due to particle growth and aging. Furthermore, the maximum volcanic cloud top height rises more than 6 km over the course of 4 d after the eruption due to aerosol–radiation interaction. This is the first direct evidence that shows how cumulative effects of aerosol dynamics and aerosol–radiation interaction lead to a more precise forecast of very fine ash lifetime in volcanic clouds.

Plume Height Time-Series Retrieval Using Shadow in Single Spatial Resolution Satellite Images

Volcanic plume height is a key parameter in retrieving plume ascent and dispersal dynamics, as well as eruption intensity; all of which are crucial for assessing hazards to aircraft operations. One way to retrieve cloud height is the shadow technique. This uses shadows cast on the ground and the sun geometry to calculate cloud height. This technique has, however, not been frequently used, especially not with high-spatial resolution (30 m pixel) satellite data. On 26 October 2013, Mt Etna (Sicily, Italy) produced a lava fountain feeding an ash plume that drifted SW and through the approach routes to Catania international airport. We compared the proximal plume height time-series obtained from fixed monitoring cameras with data retrieved from a Landsat-8 Operational Land Imager image, with results being in good agreement. The application of the shadow technique to a single high-spatial resolution image allowed us to fully document the ascent and dispersion history of the plume–cloud system. We managed to do this over a distance of 60 km and a time period of 50 min, with a precision of a few seconds and vertical error on plume altitude of ±200 m. We converted height with distance to height with time using the plume dispersion velocity, defining a bent-over plume that settled to a neutral buoyancy level with distance. Potentially, the shadow technique defined here allows downwind plume height profiles and mass discharge rate time series to be built over distances of up to 260 km and periods of 24 h, depending on vent location in the image, wind speed, and direction.

New strategies for vertical transport in chemistry transport models: application to the case of the Mount Etna eruption on 18 March 2012 with CHIMERE v2017r4

Abstract. Excessive numerical diffusion is one of the major limitations in the representation of long-range transport by chemistry transport models. In the present study, we focus on excessive diffusion in the vertical direction, which has been shown to be a major issue, and we explore three possible ways of addressing this problem: increasing the vertical resolution, using an advection scheme with anti-diffusive properties and more accurately representing the vertical wind. This study was carried out using the CHIMERE chemistry transport model for the 18 March 2012 eruption of Mount Etna, which released about 3 kt of sulfur dioxide into the atmosphere in a plume that was observed by satellite instruments (the Infrared Atmospheric Sounding Interferometer instrument, IASI, and the Ozone Monitoring Instrument, OMI) for several days. The change from the classical Van Leer (1977) scheme to the Després and Lagoutière (1999) anti-diffusive scheme in the vertical direction was shown to provide the largest improvement to model outputs in terms of preserving the thin plume emitted by the volcano. To a lesser extent, the improved representation of the vertical wind field was also shown to reduce plume dispersion. Both of these changes helped to reduce vertical diffusion in the model as much as a brute-force approach (increasing vertical resolution).

Tropical Atlantic dust and the zonal circulation

This study examines the factors driving the variability of Saharan dust over the subtropical Atlantic during summer. Monthly tropospheric dust concentrations from satellite-based model assimilation averaged in the area 10–23 N, 30–65 W, are used to create an index over the period 1980–2017. The seasonal cycle peaks in summer and affects tropical cyclones from July to September. Point-to-field regression analysis is performed, and then composites of dusty and clean seasons are analyzed as maps and sections of meteorological fields. The regression reveals significant differences in oceanic trade winds, (detrended) sea surface temperature, and atmospheric convection. Dusty minus clean composites show a zonal overturning circulation with sinking/rising motions over Africa/western Caribbean and lower easterlies/upper westerlies over the subtropical Atlantic. This circulation spreads Saharan dust and warm dry air in the 1–4 km layer westward at ~ 10 m/s over cooler waters, inhibiting convection. Among the factors driving tropospheric dust variability is the Pacific El Nino Southern Oscillation. Composites of dusty and clean hurricane occurrence show a threefold difference in numbers and a tenfold difference in mean power dissipation index. Analysis of a dust event in August 2009 illustrates how wind shear and cool SST conspire to suppress tropical easterly waves. Supplementary work characterizes the dispersion of a dense Saharan dust plume in June 2020.