Plume Dispersion Research Articles

Large-eddy simulation studies for predicting plume concentrations around nuclear facilities using an overlapping technique

We propose, in emergency response to nuclear accidents, a practical and quick local-scale atmospheric dispersion calculation method using an overlapping technique. First, we pre-calculated large-eddy simulations (LESs) of plume dispersion around an actual nuclear facility under idealised atmospheric conditions with 36 wind-direction cases and made a dataset of the 10-minute averaged concentrations for each wind direction case. Then, we conducted LESs of plume dispersion for 1-hour periods under realistic atmospheric conditions using the meteorological data and estimated the spatial distributions of the 1-hour averaged concentrations by overlapping the pre-calculated concentration data depending on the frequency of the mean wind directions. It is shown that the concentration distribution patterns are well reproduced in comparison to those under the realistic conditions. It is concluded that the atmospheric dispersion calculation method using the overlapping technique has potentially a high performance in emergency responses to nuclear accidents.

Spatio-temporal analysis of prodelta dynamics by means of new satellite generation: the case of Po river by Landsat-8 data

This paper describes a procedure to perform spatio-temporal analysis of river plume dispersion in prodelta areas by multi-temporal Landsat-8-derived products for identifying zones sensitive to water discharge and for providing geostatistical patterns of turbidity linked to different meteo-marine forcings. In particular, we characterized the temporal and spatial variability of turbidity and sea surface temperature (SST) in the Po River prodelta (Northern Adriatic Sea, Italy) during the period 2013–2016. To perform this analysis, a two-pronged processing methodology was implemented and the resulting outputs were analysed through a series of statistical tools. A pixel-based spatial correlation analysis was carried out by comparing temporal curves of turbidity and SST hypercubes with in situ time series of wind speed and water discharge, providing correlation coefficient maps. A geostatistical analysis was performed to determine the spatial dependency of the turbidity datasets per each satellite image, providing maps of correlation and variograms. The results show a linear correlation between water discharge and turbidity variations in the points more affected by the buoyant plumes and along the southern coast of Po River delta. Better inverse correlation was found between turbidity and SST during floods rather than other periods. The correlation maps of wind speed with turbidity show different spatial patterns depending on local or basin-scale wind effects. Variogram maps identify different spatial anisotropy structures of turbidity in response to ambient conditions (i.e. strong Bora or Scirocco winds, floods). Since the implemented processing methodology is based on open source software and free satellite data, it represents a promising tool for the monitoring of maritime ecosystems and to address water quality analyses and the investigations of sediment dynamics in estuarine and coastal waters.

Transport of anisotropic particles under waves

Using a numerical model, we analyse the effects of shape on both the orientation and transport of anisotropic particles in wavy flows. The particles are idealized as prolate and oblate spheroids, and we consider the regime of small Stokes and particle Reynolds numbers. We find that the particles preferentially align into the shear plane with a mean orientation that is solely a function of their aspect ratio. This alignment, however, differs from the Jeffery orbits that occur in the residual shear flow (that is, the Stokes drift velocity field) in the absence of waves. Since the drag on an anisotropic particle depends on its alignment with the flow, this preferred orientation determines the effective drag on the particles, which in turn impacts their net downstream transport. We also find that the rate of alignment of the particles is not constant and depends strongly on their initial orientation; thus, variations in initial particle orientation result in dispersion of anisotropic-particle plumes. We show that this dispersion is a function of the particle’s eccentricity and the ratio of the settling and wave time scales. Due to this preferential alignment, we find that a plume of anisotropic particles in waves is on average transported farther but dispersed less than it would be if the particles were randomly oriented. Our results demonstrate that accurate prediction of the transport of anisotropic particles in wavy environments, such as microplastic particles in the ocean, requires the consideration of these preferential alignment effects.

Exposure of coastal ecosystems to river plume spreading across a near-equatorial continental shelf

The Berau Continental Shelf (BCS) in East Kalimantan, Indonesia, harbours various tropical marine ecosystems, including mangroves, seagrass meadows and coral reefs. These ecosystem are located partly within reach of the Berau River plume, which may affect ecosystem health through exposure to land-derived sediments, nutrients and pollutants carried by the plume. This study aims (1) to assess the exposure risk of the BCS coastal ecosystems to river plume water, measured as exposure time to three different salinity levels, (2) to identify the relationships between these salinity levels and the abundance and diversity of coral and seagrass ecosystems, and (3) to determine a suitable indicator for the impacts of salinity on coral reef and seagrass health. We analysed hydrodynamic models, classified salinity levels, and quantified the correlations between the salinity model parameters and ecological metrics for the BCS systems. An Empirical Orthogonal Functions (EOF) analysis revealed three modes of river plume dispersal patterns, which strongly reflect monsoon seasonality. The first mode, explaining 39% of the variability, was associated with the southward movement of the plume due to northerly winds, while the second and third modes (explaining 29% and 26% of the variability, respectively) were associated with the northeastward migration of the plume related to southwesterly and southerly winds. Exposure to low salinity showed higher correlations with biological indicators than mean salinity, indicating that low salinity is a more suitable indicator for coastal ecosystem health. Significant correlations (R2) were found between exposure time to low salinity (days with salinity values below 25 PSU) with coral cover, coral species richness, seagrass cover, the number of seagrass species, seagrass leaf phosphorus, nitrogen, C:N ratio and iron content. By comparing the correlation coefficients and the slopes of the regression lines, our study suggests that coral reefs are more susceptible to low salinity levels exposure than seagrass meadows. Regarding the risk of corals being exposed to low salinity, nearshore and northern barrier reefs were classified as “high risk”, the middle barrier reef as “medium to high risk” and southern barrier reefs as “medium risk”. Further offshore, the oceanic reefs were classified as “low risk”. Regarding the seagrass meadows, the nearshore region was categorized as “high risk”, the barrier reef as “medium to low risk” and oceanic reefs as “low risk”. This study contributes to assessing the potential impacts of salinity on the BCS ecosystems, and further provides a knowledge base for marine conservation planning.

Impact of remotely generated eddies on plume dispersion at abyssal mining sites in the Pacific

Proposed harvesting of polymetallic nodules in the Central Tropical Pacific will generate plumes of suspended sediment which are anticipated to be ecologically harmful. While the deep sea is low in energy, it also can be highly turbulent, since the vertical density gradient which suppresses turbulence is weak. The ability to predict the impact of deep plumes is limited by scarcity of in-situ observations. Our observations show that the low-energy environment more than four kilometres below the surface ultimately becomes an order of magnitude more energetic for periods of weeks in response to the passage of mesoscale eddies. The source of these eddies is remote in time and space, here identified as the Central American Gap Winds. Abyssal current variability is controlled by comparable contributions from tides, surface winds and passing eddies. During eddy-induced elevated flow periods mining-related plumes, potentially supplemented by natural sediment resuspension, are expected to spread and disperse more widely and rapidly. Predictions are given of the timing, location and scales of impact.

Odour Dispersion Modelling for Raw Rubber Processing Factories

An odour dispersion modelling approach was adopted to assess odour dispersion, particularly from the drying stage of raw rubber processing factories, identified as a major source of malodour pollutant in the rubber industry. The Ausplume modelling software which uses a Gaussian plume dispersion model was used to predict odour dispersion from the water scrubber, a malodour control system used by rubber processing factories. The modelling involved a selected range of parameters in correlation with characteristics of raw rubber malodour pollutants and interpretations of the predicted data were discussed in terms of effects of stack height of the water scrubber, odour concentration and local meteorological conditions at several locations in peninsular Malaysia. In general, it was found that a higher stack of water scrubber minimises effects of different emission concentration characteristics and local meteorological conditions. This was demonstrated by profiles of predicted odour concentration dispersion and minimal dispersion variation within variables as attributed by standard deviation curves. Furthermore, higher stacks predicted lower odour concentration carried over from the point of emission to ground level receptors by taking into consideration all of the modelling assumptions. In summary, the initialfindings from this work are beneficial to designing a better odour control system which subsequently minimises odour impact to the surrounding environment.

Wildfire smoke plumes transport under a subsidence inversion: Climate and health implications in a distant urban area

This study shows the influence of two large wildfires (one of which was the largest wildfire ever recorded in the region of Castilla y León) in the north-west of the Iberian Peninsula upon the atmospheric air quality of the city of León, Spain, at approximately 70km from the fires, on days with a strong subsidence inversion associated with high pressures. The vertical dispersion of the smoke plume was inhibited and this caused an increase in the particulate matter (PM) in the atmosphere. During this event, average values of up to 1700±600particlescm−3 were registered, most of which corresponding to the smallest fraction of the fine mode. On the other hand, the count median diameter of the fine mode (CMDf) increased gradually from 0.09 to 0.14μm. The PM10 and PM2.5 reached hourly values of 89 and 36μgm−3, respectively. This study also estimates the changes in the optical properties of the particles as well as the associated radiative forcing. The presence of an important load of absorbing aerosols was detected, with instantaneous radiative atmospheric forcing up to +134.6Wm−2. The estimations of the respirable fractions showed in healthy adults high levels of mass concentration of the aerosol that reaches the bronchioles and alveoli (up to 43μgm−3).

Metal contamination of the St. Lawrence River following a major release of untreated wastewater.

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Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

Abstract. Tropical volcanic eruptions have been widely studied for their significant contribution to stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1° N, 153.2° E), which erupted in June 2009, and the influence of the Asian summer monsoon (ASM) on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission time series and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach using the Lagrangian particle dispersion model Massive–Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived SO2 emission time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The MPTRAC simulations show that about 4 % of the sulfur emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The MPTRAC simulations and MIPAS aerosol data both show that between the potential temperature levels of 360 and 400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported southwestwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an aerosol hole inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of the water vapor tape recorder. Furthermore, a hypothetical MPTRAC simulation for a wintertime eruption was carried out. It is shown that under winter atmospheric circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetical scenario, a high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.

Biochemical responses of Solea senegalensis after continuous flow exposure to urban effluents

Urban effluent potential toxicity was assessed by a battery of biomarkers aimed at determining sub-lethal effects after continuous exposure on the marine organism Solea senegalensis. Specimens were exposed to five effluent concentrations (1/2, 1/4, 1/8, 1/16, 1/32) during 7-days, simulating the dispersion plume at the discharge point. Three different groups of biomarkers were selected in the present study: biomarkers of exposure (Phase I: EROD and DBF; Phase II: GST), biomarkers with antioxidant responses (GR and GPX) and biomarkers of effects (DNA damage and LPO). Additionally, a biological depuration treatment (photobiotreatment (PhtBio)) was tested in order to reduce the adverse effects on aquatic organisms. Effluent exposure caused sub-lethal responses in juvenile fish suggesting oxidative stress. After PhtBio application, concentrations of the major part of measured contaminants were reduced, as well as their bioavailability and adverse effects.

On the Longitudinal Dispersion in Conservative Transport Through Heterogeneous Porous Formations at Finite Peclet Numbers

AbstractWe consider transport of a conservative solute through an aquifer as determined: (i) by the advective velocity, which depends upon the hydraulic conductivity K and (ii) by the local spreading due to the pore‐scale dispersion (PSD). The flow is steady, and it takes place in a porous formation where, owing to its erratic spatial variations, the hydraulic log conductivity is modeled as a stationary Gaussian random field. The relative effect of the above mechanisms (i)–(ii) is quantified by the Peclet number which, in most of the previous studies, was considered infinite (i.e., no PSD) due to the overtake of advective heterogeneities upon the PSD. Here we aim at generalizing such studies by accounting for the impact of finite Pe on conservative transport. Previous studies on the topic required extensive numerical computations. In the present note, we remove the computational burden by adopting the rational approximate expression of Dagan and Cvetkovic (1993) for the covariance of the velocity field. This allows one to obtain closed form expressions for the quantities characterizing the longitudinal plume's dispersion. Transport can be straightforwardly investigated by dealing with a modified Peclet number incorporating both the PSD and the aquifer's anisotropy. The satisfactory match to Cape Cod field data suggests that the present theoretical results lend themselves as a useful tool to assess the impact of the PSD upon conservative transport through heterogeneous porous formations.

Atmospheric dispersion of trace metals between two smelters: An approach coupling lead, strontium and osmium isotopes from bioindicators

Bioindicators, by naturally cumulating the impacts of chemical contaminants over time, have demonstrated their added value in evaluating environmental quality. We studied Pb, Sr and Os isotope systematics from Cladonia rangiferina lichens collected along a transect between two smelting complexes located in Rouyn-Noranda and Sudbury (Canada) to identify sources of these metals in the Abitibi region and to delineate the extent of their respective emission plumes. Results show that metals present in the study area are explained by the contamination of the regional background by deposition from the atmospheric emissions of the different smelters over distances up to 250km. A rough estimate of the respective metal contributions of each smelter to the lichen samples was calculated. At low metal concentrations, lichen samples indicate that dispersion plumes may differ for the Pb and Os contamination, perhaps to be linked to differential volatility.

Prefrontal bore mixing

AbstractRainbow Ridge, a 1950 m deep upthrusted ultramafic block along the axis of the Mid‐Atlantic Ridge, has an active hydrothermal vent system at 2400 m on its western slope. However, within 1 km from the vent excessive temperatures are barely measurable, probably due to strong turbulent mixing. This mixing is studied here using a 400 m long high‐resolution temperature sensor array moored with a 600 m ranging 75 kHz acoustic Doppler current profiler. Rich internal wave turbulence was recorded, characterized by 100–200 m upshoots and >200 m large overturning in particular near the end of the warming phase of the up and down moving tide. These highly nonlinear internal waves of tides interacting with buoyancy frequency waves extend up to 400 m above the sloping bottom of the ridge. While a turbulent “bottom boundary layer” could barely be defined, the more intense turbulence higher up in the water column is suggested to lead to the strong dispersion of the hydrothermal plume.

A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016

Abstract. In June and July 2016 the Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) project organised a major international field campaign in southern West Africa (SWA) including measurements from three inland ground supersites, urban sites in Cotonou and Abidjan, radiosondes, and three research aircraft. A significant range of different weather situations were encountered during this period, including the monsoon onset. The purpose of this paper is to characterise the large-scale setting for the campaign as well as synoptic and mesoscale weather systems affecting the study region in the light of existing conceptual ideas, mainly using objective and subjective identification algorithms based on (re-)analysis and satellite products. In addition, it is shown how the described synoptic variations influence the atmospheric composition over SWA through advection of mineral dust, biomass burning and urban pollution plumes.The boreal summer of 2016 was characterised by Pacific La Niña, Atlantic El Niño and warm eastern Mediterranean conditions, whose competing influences on precipitation led to an overall average rainy season. During the relatively dusty pre-onset Phase 1 (1–21 June 2016), three westward-propagating coherent cyclonic vortices between 4 and 13° N modulated winds and rainfall in the Guinea coastal area. The monsoon onset occurred in connection with a marked extratropical trough and cold surge over northern Africa, leading to a breakdown of the Saharan heat low and African easterly jet and a suppression of rainfall. During this period, quasi-stationary low-level vortices associated with the trough transformed into more tropical, propagating disturbances resembling an African easterly wave (AEW). To the east of this system, moist southerlies penetrated deep into the continent. The post-onset Phase 2 (22 June–20 July 2016) was characterised by a significant increase in low-level cloudiness, unusually dry conditions and strong northeastward dispersion of urban pollution plumes in SWA as well as rainfall modulation by westward-propagating AEWs in the Sahel. Around 12–14 July 2016 an interesting and so-far undocumented cyclonic–anticyclonic vortex couplet crossed SWA. The anticyclonic centre had its origin in the Southern Hemisphere and transported unusually dry air filled with aged aerosol into the region. During Phase 3 (21–26 July 2016), a similar vortex couplet slightly farther north created enhanced westerly moisture transports into SWA and extraordinarily wet conditions, accompanied by a deep penetration of the biomass burning plume from central Africa. Finally, a return to more undisturbed monsoon conditions took place during Phase 4 (27–31 July 2016). The in-depth synoptic analysis reveals that several significant weather systems during the DACCIWA campaign cannot be attributed unequivocally to any of the tropical waves and disturbances described in the literature and thus deserve further study.

Impact of seasonal vertical stratification on the dispersion patterns of dredging plumes off the south coast of Korea

Simultaneous satellite and ship-borne surveys have been conducted to investigate the dispersion patterns of dredging plumes off the south coast of Korea in two contrasting seasons (spring and autumn). The distribution of total suspended solid (TSS) derived from sequential satellite imagery showed that the dredging plumes in spring developed over longer distances along the surface current than those in autumn. In spring, the deep and strong stratified condition in the water column contributed to the increase in radius of plume dispersion along the water surface. In autumn, the shallow and vertically well-mixed (or un-stratified) condition in the water column enhanced sinking of suspended dredged materials. This difference is due to the Brunt-Väisälä frequency being higher in spring (0.0183s−1) than in autumn (0.0123s−1). Although the sediment-laden overflow significantly increased TSS near the surface during the dredging period, the TSS contribution to water column stratification was only 2.3−5.6% of the thermohaline contribution. Therefore, the seasonal variation of thermohaline density is the main factor determining the dispersion patterns of dredging plumes in the study area.

Application of Gauss's theorem to quantify localized surface emissions from airborne measurements of wind and trace gases

Abstract. Airborne estimates of greenhouse gas emissions are becoming more prevalent with the advent of rapid commercial development of trace gas instrumentation featuring increased measurement accuracy, precision, and frequency, and the swelling interest in the verification of current emission inventories. Multiple airborne studies have indicated that emission inventories may underestimate some hydrocarbon emission sources in US oil- and gas-producing basins. Consequently, a proper assessment of the accuracy of these airborne methods is crucial to interpreting the meaning of such discrepancies. We present a new method of sampling surface sources of any trace gas for which fast and precise measurements can be made and apply it to methane, ethane, and carbon dioxide on spatial scales of ∼ 1000 m, where consecutive loops are flown around a targeted source region at multiple altitudes. Using Reynolds decomposition for the scalar concentrations, along with Gauss's theorem, we show that the method accurately accounts for the smaller-scale turbulent dispersion of the local plume, which is often ignored in other average mass balance methods. With the help of large eddy simulations (LES) we further show how the circling radius can be optimized for the micrometeorological conditions encountered during any flight. Furthermore, by sampling controlled releases of methane and ethane on the ground we can ascertain that the accuracy of the method, in appropriate meteorological conditions, is often better than 10 %, with limits of detection below 5 kg h−1 for both methane and ethane. Because of the FAA-mandated minimum flight safe altitude of 150 m, placement of the aircraft is critical to preventing a large portion of the emission plume from flowing underneath the lowest aircraft sampling altitude, which is generally the leading source of uncertainty in these measurements. Finally, we show how the accuracy of the method is strongly dependent on the number of sampling loops and/or time spent sampling the source plume.

Aggregation, Allee effects and critical thresholds for the management of the crown-of-thorns starfish Acanthaster planci

We investigated how density and aggregation influence crown-of-Thorns starfish Acanthaster planci reproductive success, using an empirically-Tuned, individual-based simulation model that incorporates spatial and temporal biological stochasticity associated with spawning, and a kinetics model of fertilisation that explicitly incorporates the probability of polyspermy. Greater aggregation of individuals relieved Allee fertilisation dynamics, particularly at low densities, leading to higher rates of successful monospermic fertilisation and allowing populations to produce many more zygotes. This is likely more important to smaller, rather than larger, populations, due to limited and more variable reproductive success. In higher density populations a fertilisation optimum was observed at moderate levels of aggregation, above which monospermic fertilisation plateaued or even declined. This was likely due to 2 factors: The spatial dynamics of gamete plume dispersal and polyspermic fertilisation. Comparison of in situ natural spawning aggregation with model results indicates a cost-benefit equilibrium may exist between aggregation and reproductive success, and that relief from mechanisms limiting aggregation (for example, decreased relative predator abundance) may permit increased aggregation resulting in greater fertilisation and zygote production. We propose an Allee threshold of 3 starfish ha-1 (for starfish of a mean diameter 345 mm), below which reproductive capacity is greatly reduced regardless of aggregation level. These preliminary findings posit aggregation as a key factor in outbreak formation that may feasibly be incorporated into preventative management strategies to detect and define incipient outbreak conditions and to mitigate subsequent risk.

Stability of volcanic ash aggregates and break-up processes

Numerical modeling of ash plume dispersal is an important tool for forecasting and mitigating potential hazards from volcanic ash erupted during explosive volcanism. Recent tephra dispersal models have been expanded to account for dynamic ash aggregation processes. However, there are very few studies on rates of disaggregation during transport. It follows that current models regard ash aggregation as irrevocable and may therefore overestimate aggregation-enhanced sedimentation. In this experimental study, we use industrial granulation techniques to artificially produce aggregates. We subject these to impact tests and evaluate their resistance to break-up processes. We find a dependence of aggregate stability on primary particle size distribution and solid particle binder concentration. We posit that our findings could be combined with eruption source parameters and implemented in future tephra dispersal models.

Modeling of gas adsorption by aerosol plumes emitted from industrial sources

Abstract Adsorption of trace atmospheric gases by aerosol particles contributes to the evolution of concentration distribution of the trace constituents and can affect subsequent chemical reactions in the atmosphere. We suggest a two dimensional model of adsorption of trace atmospheric constituents by aerosol particles in air pollution plume emitted from an industrial source. The model is based on an application of theory of turbulent diffusion in the atmospheric boundary layer (ABL) in conjunction with plume dispersion model and model of gas adsorption by porous solid particles. The wind velocity profiles used in the simulations were fitted from our data previously obtained in field measurements conducted in the Northern Negev (Israel) using the experimental wind mast. The developed model allows analyzing spatial and temporal evolution of adsorbate concentration in the gaseous phase as well as in the particulate matter. The adsorbate concentration distributions are calculated for the particulate matter PM2.5–10, which is typical for industrial emissions. Analysis is performed for different meteorological conditions and atmospheric stability classes. It is shown that the concentration of gases adsorbed by aerosol plume strongly depends on the level of atmospheric turbulence. The obtained results are compared with the available experimental data.

Probabilistic Assessment of Severe Accident Consequence in West Bangka

Probabilistic dose assessment for severe accident condition is performed for West Bangka area. Source-term from WASH-1400 reactor analysis is used as a conservative release scenario for 1000 MWe PWR. Seven groups of isotopes are used in the simulation based on core inventory and release fraction. Population distribution for Muntok district and the area within a 100 km radius is obtained from 2014 data. Meteorological data is provided through cyclic sampling from a database containing two-year site-specific hourly records in 2014-2015 periods. PC-COSYMA segmented plume dispersion code is used to investigate the assumed the consequence of the accident scenario. The result indicates that early or deterministic effect is important for areas close the release point while long-term or stochastic effect is related to population distribution and covers area of up to 100 km from the release point. The mean annual expected values for early mortality and late mortality for the population within 100 km radius from Muntok site are 2.38×10−4yr−1 and 1.33×10−3 yr−1 respectively.