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In this work, we determine the major channels through which air pollutants, mainly originating in Northeast Asian mega-cities, flow out into the Northwestern Pacific atmosphere. For this purpose, comprehensive backward/forward trajectory analyses are conducted. Two important channels along which pollutants from the Northeast Asian mega-cities flow out are defined, and are labeled as “DC8 transport path” and “P3B transport path”. We then comprehensively examine the chemico-microphysical transformations of the anthropogenic pollutants from the Northeast Asian mega-cities along the two major transport paths, using a new Lagrangian forward-trajectory photochemical model. In the newly developed model, state-of-the-science parameterizations for considering chemico-microphysical aging processes and atmospheric aerosol processes are incorporated. As air masses travel toward low latitudes through the marine boundary layer (MBL), the temperature increases along the trajectories and large amounts of PAN experience thermal decomposition. By this process, PAN can be an important supplier of NO 2 in the remote MBL. The O 3 productions in the remote Northwestern Pacific MBL are fueled and maintained by NO x provided from the PAN decomposition. High O 3 levels (>50 ppb) are observed within the remote MBL of the Northwestern Pacific Oceans from several TRACE-P DC8 and P3B measurements under the continental outflow situations. Gas-phase SO 2 is continuously converted into nss-sulfate via heterogeneous oxidation reaction with H 2 O 2 at a particle pH of 2–5. The Lagrangian-trajectory modeling studies also indicate that in the remote MBL of Northwestern Pacific Ocean under continental outflow situations, conditions are unfavorable for nucleation events, because of the depletion of SO 2 , the large aerosol surface areas available for H 2 SO 4 sink, and high temperatures.

There is an urgent need to better constrain the global rates of mercury degassing from natural sources, including active volcanoes. Hitherto, estimates of volcanic fluxes have been limited by the poorly determined speciation of Hg in volcanic emissions. Here, we present a systematic characterisation of mercury partitioning between gaseous (Hg(g)) and particulate (Hg(p)) forms in the volcanic plume of Mount Etna, the largest open-vent passively degassing volcano on Earth. We demonstrate that mercury transport is predominantly in the gas phase, with a mean Hg(p)/Hg(g) ratio of ∼0.01 by mass. We also present the first simultaneous measurement of divalent gaseous mercury ( Hg ( g ) II ) and total gaseous mercury (Hg(g)) in a volcanic plume, which suggests that Hg ( g ) 0 is the prevalent form of mercury in this context. These data are supported by the results of model simulations, carried out with HSC thermodynamic software. Based on a mean “bulk plume” Hg/SO2 mass ratio of 8.7×10−6, and a contemporaneous volcanic SO2 flux of 0.8 Mt yr−1, we estimate an Hg emission rate from Mt. Etna during passive degassing of 5.4 t yr−1 (range, 1.1–10 t yr−1). This corresponds to ∼0.6% of global volcanic Hg emissions, and about 5% of Hg released from industrial activities in the Mediterranean area.

Particulate matter emissions generated by agricultural field preparation and harvesting operations were measured remotely via aerosol lidar and sampled simultaneously with a variety of aerosol point samplers in order to quantify dust plume space and time dynamics and particulate mass and number concentrations. Data for two cotton operations (disking, harvesting) in a flood-irrigated field in New Mexico are presented. Dust plume dynamics varied with boundary layer meteorological conditions, especially atmospheric stability, with plume maximum height significantly lower under stable conditions. Plume tracking indicated little change in plume area with height under unstable conditions and plume movement depended on wind speed and direction. Particle mass distributions indicate approximately 50% of the measured PM10 mass was PM2.5, significantly higher than previously reported values, possibly due to the near-source nature of the samples collected here. Variability in plume movement matched the variability in short-term wind fluctuations and this variability helps explain why models that utilize long-term averages perform poorly when trying to capture plume dynamics for nonsteady sources such as tractor operations.

This modeling study evaluated the capability of alternative funnel-and-gate structures with three gates for capturing contaminated groundwater in a hypothetical unconfined aquifer. Simulated interceptor structures were linear and 45 m wide, consisting of three gates and two funnels (walls). One gate occupied the center and two gates occupied the ends of the interceptor structures. The structures, positioned perpendicular to regional groundwater flow, traversed the entire thickness of the aquifer. A total of four structures were evaluated (numbers designate widths of end, center, and end gates, respectively, in meters): 3-3-3, 2-5-2, 1-7-1, and 4-1-4. Particle tracking and zonal water budgets identified shapes of capture zones and discharge patterns for each interceptor structure. A mass transport model, accounting for advection and hydrodynamic dispersion, tested the capability of each structure for capturing a contaminant plume. Results suggest that: time-dependent capture zones underestimate the amount of time to capture a contaminant plume, wide center gates facilitate plume capture, and wide end gates facilitate lateral containment of contaminants. Of the structures simulated, the 2-5-2 configuration was relatively efficient at processing and containing the simulated contaminant plume.

A mathematical model and an analytical solution are presented to describe field-scale dense non-aqueous phase liquid (DNAPL) source dissolution and source zone biodecay rates coupled with advective–dispersive dissolved plume transport. The model is employed to investigate various source remediation options on source zone mass depletion, net source mass flux, and dissolved plume attenuation for different source zone “architectures” (i.e., pools versus residual DNAPL) and compliance criteria. Remediation options considered include partial source mass removal, source flow reduction, and source zone enhanced biodecay. Partial mass reduction reduces the source zone mass flux and downgradient concentrations for residual DNAPL sources and pools, which can significantly reduce dissolved plume size and time to reach compliance criteria. Source zone flow reduction decreases the rate of source mass depletion, but can facilitate compliance, if concentrations at compliance locations are not too high initially. Increase in source biodecay rate, especially with concomitant increases in dissolution kinetics, can decrease the time to achieve compliance criteria over biodecay alone.

Pollution in the coastal waters of the Mumbai, India was analyzed the spectral signature with high resolution IRS-L3 data at the sewage discharge points in the Thane creek. The sewage distribution pattern was studied with reference to local tide on 21 February 2002 and 29 October 2002. The sewage plumes were identified off the discharge points in Thane Creek, Mumbai and spread areas were estimated indicating relatively high concentration of pollutants in the inner creek.

The plume rich with chlorophyll-a concentration (>0.3 mg/l) observed on 22 March 2003 along the 16° N in the western Bay of Bengal off the Krishna-Godavari river delta was studied. Relatively high sea surface temperature (>30° C) observed in the plume area indicated their origin in the coastal waters. The bloomy plume was found spreading 400 to 500 km offshore in the form of an offshore jet extending as far as 86° E in the Bay of Bengal. An offshore flow was observed with geostrophic velocity exceeding 50 cm/s with a cyclonic eddy on its north around 17° N, 82° E and an anti-cyclonic eddy around 14° N, 83° E to its south. The hydrographic data of the area were studied with the observations made by GTS data buoy indicated coastal upwelling. Similar plumes were also observed during the years 2004 and 2005.

The objective of this work is to study the variation of axi-symmetric fire plume structure with the variation of gravity level, which is of great significance to aviation and spaceflight. Numerical simulation of fire plume under various gravity levels is proposed here. Detailed comparison and analysis of centerline temperature and velocity are carried out. The results show that the variation of fire plume structure with the increase of gravity level can be divided into two stages. The first stage is flow dominated, while the second stage is oxygen dominated. The fire plume structure in the transition stage has unique characteristics and should be given more attention for fire safety. It has also been shown that the level of gravity has a significant effect on the fire plume structure. The study in this article extends the range where a fire plume can take place and promotes a better understanding of axi-symmetric fire plume.

Continuous crosswell seismic monitoring of a small-scale [Formula: see text] injection was accomplished with the development of a novel tubing-deployed piezoelectric borehole source. This piezotube source was deployed on the [Formula: see text] injection tubing, near the top of the saline aquifer reservoir at [Formula: see text] depth, and allowed acquisition of crosswell recordings at [Formula: see text] intervals during the multiday injection. The change in traveltime recorded at various depths in a nearby observation well allowed hour-by-hour monitoring of the growing [Formula: see text] plume via the induced seismic velocity change. Traveltime changes of [Formula: see text] (up to 8%) were observed, with no change seen at control sensors placed above the reservoir. The traveltime measurements indicate that the [Formula: see text] plume reached the top of the reservoir sand before reaching the observation well, where regular fluid sampling was occuring during the injection, thus providing information about the in situ buoyancy of [Formula: see text].

From 16 to 26 July 2003 an extensive field campaign was carried out around Mt Etna, Sicily, Italy. During the campaign a new airborne system, Fire Airborne Spectral Analyzer (FASA), was tested. The main instrument of the payload is a high resolution Michelson Interferometer with Rotating Retroreflector (MIROR), which operates in the nominal infrared 600-3000 cm-1 spectral range with a high resolution of 0.12 cm-1. This work investigates the feasibility of using MIROR data to retrieve the surface temperature, the hyper-spectral emissivity and the SO2 volcanic plume abundance. The results for the surface parameters show a good agreement with those obtained by satellite data and on ground measurements. In particular, the spectral emissivity shows a meaningful minimum, around 1040 cm-1, consistent with the basaltic properties of Mt Etna's surface. A sensitivity study has also been carried out to show the difficulties of SO2 columnar abundance retrieval due to the too low SO2 volcanic emission and the too high instrumental noise.

The Environmental Fluid Dynamic Code, an estuarine and coastal ocean circulation model, is used to simulate the distribution of the salinity plume in the vicinity of the mouth of the Cape Fear River Estuary, North Carolina. The individual and coupled effects of the astronomical tides, river discharge, and atmospheric winds on the spatial and temporal distributions of coastal water levels and the salinity plume were investigated. These modeled effects were compared with water level observations made by the National Oceanic and Atmospheric Administration and salinity surveys conducted by the Coastal Ocean Research and Monitoring Program. Model results and observations of salinity distributions and coastal water level showed good agreement. The simulations indicate that strong winds tend to reduce the surface plume size and distort the bulge shape near the estuary mouth due to enhanced wind-induced surface mixing. Under normal discharge conditions, tides, and light winds, the southward outwelling plume veers west. Relatively moderate winds can mechanically reverse the flow direction of the plume. Under conditions of weak to moderate winds the water column does not mix vertically to the bottom, while in strong wind cases the plume becomes vertically well mixed. Under conditions of high river discharge the plume increases in size and reaches the bottom. Vertical mixing induced by strong spring tides can also enable the plume to reach the bottom.

Nutrient levels in coastal waters must be accurately assessed to determine the nutrient effects of increasing populations on coastal ecosystems. To accomplish this goal, in-field data with sufficient temporal resolution are required to define nutrient sources and sinks, and to ultimately calculate nutrient budgets. Models then are required for the interpretation and analysis of data sets. To quantify the coastal ocean nitrogen input to Yaquina Bay, Oregon, nitrate concentrations were measured by a moored sensor hourly for one month during summer upwelling some distance outside the estuary entrance jetties. The time series results then were interpreted using a steady state model (Visual Plumes’ PDSW) and a hydrodynamic model, the Finite Volume Coastal Ocean Model (FVCOM). The physical scales of many stream and river plumes often lie between the scales for outfall mixing zone plume models, such as those found in EPA's Visual Plumes, and larger-sized grid scales for regional circulation models like FVCOM. A potential advantage of relatively simple, steady state plume models is that they use entrainment terms to close the plume equations, theory that has proven useful in simulating turbulent plume discharges from various sources, some approaching the dimensions of rivers. Important advantages of models like FVCOM are that they are dynamic and include the effects of the Earth's rotation. The results showed that the steady-state plume model simulates observed velocity and concentration data fairly well during periods of strong discharge velocity and weak ambient coastal currents. FVCOM was judged to give better estimates under all other ambient current conditions, although the data from the mooring cannot be used to prove this assertion as stronger currents would deflect the plume away from the mooring. Nevertheless, plume models may be useful in establishing boundary and initial conditions for hydrodynamic models.

Burning embers, commonly called firebrands, are lofted by a fire's buoyant plume and transported downwind to ignite new fires (spot fires) ahead of the main fire. In the present work, transport and combustion of firebrands from burning trees are numerically investigated. A three-dimensional physics-based model is used to precompute the steady-state gas flow and thermal fields induced by a crown fire into which firebrands will be injected. Another preliminary study of the thermal degradation and combustion of woody fuel particles is conducted to determine the burning characteristics of firebrands. Then the trajectories and burning rates of disk-shaped firebrands lofted by the crown fire plume and transported downwind are calculated for various values of the wind speed, U wind , and of the fire intensity, I. Firebrands of different sizes and densities are first launched from a specified location at the top of the canopy. Firebrands that fall on the ground are in a flaming or a glowing state depending on the product ρ f w 0 × τ ( ρ f w 0 : initial firebrand density, τ: firebrand thickness). Results show that for firebrands that remain longer in the thermal plume, the distance covered upon landing is independent of the initial particle diameter and correlates well with I 0.1 U wind 0.9 ( ρ f w 0 × τ ) −0.2 . The normalized brand mass fraction at landing also correlates with the flight time normalized by the product ρ f w 0 × τ for flaming firebrands or by the product ρ f w 0 × D 0 5 / 3 ( D 0 : initial firebrand diameter) for glowing firebrands. For firebrands released from random locations within the canopy, the above correlations remain unchanged, thereby demonstrating the generality of the developed approach.

Careful site characterization is critical for successful geologic storage of carbon dioxide (CO2) because of the many physical and chemical processes impacting CO2 movement and containment under field conditions. Traditional site characterization techniques such as geological mapping, geophysical imaging, well logging, core analyses, and hydraulic well testing provide the basis for judging whether or not a site is suitable for CO2 storage. However, only through the injection and monitoring of CO2 itself can the coupling between buoyancy flow, geologic heterogeneity, and history-dependent multi-phase flow effects be observed and quantified. CO2 injection and monitoring can therefore provide a valuable addition to the site-characterization process. Additionally, careful monitoring and verification of CO2 plume development during the early stages of commercial operation should be performed to assess storage potential and demonstrate permanence. The Frio brine pilot, a research project located in Dayton, Texas (USA) is used as a case study to illustrate the concept of an iterative sequence in which traditional site characterization is used to prepare for CO2 injection and then CO2 injection itself is used to further site-characterization efforts, constrain geologic storage potential, and validate understanding of geochemical and hydrological processes. At the Frio brine pilot, in addition to traditional site-characterization techniques, CO2 movement in the subsurface is monitored by sampling fluid at an observation well, running CO2-saturation-sensitive well logs periodically in both injection and observation wells, imaging with crosswell seismic in the plane between the injection and observation wells, and obtaining vertical seismic profiles to monitor the CO2 plume as it migrates beyond the immediate vicinity of the wells. Numerical modeling plays a central role in integrating geological, geophysical, and hydrological field observations.

The dispersal of the Hudson River plume in response to idealized wind forcing is studied using a three-dimensional model. The model domain includes the Hudson River and its estuary, with a realistic coastline and bottom topography of the New York Bight. Steady low river discharge typical of mean conditions and a high-discharge event representative of the spring freshet are considered. Without wind forcing the plume forms a southward coastally trapped current at low river discharge and a large recirculating bulge of low-salinity water during a high-discharge event. Winds affect the freshwater export through the mouth of the estuary, which is the trajectory the plume takes upon entering the waters of the Mid-Atlantic Bight inner shelf, and the rate at which freshwater drains downstream. The dispersal trajectory is also influenced by the particular geography of the coastline in the apex of the New York Bight. Northward wind causes offshore displacement of a previously formed coastally trapped plume and drives a new plume along the Long Island coast. Southward wind induces a strong coastal jet that efficiently drains freshwater to the south. Eastward wind aids freshwater export from the estuary and favors the accumulation of freshwater in the recirculating bulge outside the mouth of Raritan Bay. Westward wind delays freshwater export from Raritan Bay. The momentum balance of the modeled plume shows that buoyancy and wind forces largely determine the pattern of horizontal freshwater dispersal, including the spreading of freshwater over ambient, more saline water and the bulge formation.

In densely populated coastal cities in Asia, wastewater outfalls are often located not far from sensitive areas such as beaches or shellfisheries. The impact and risk assessment of effluent discharges poses particular technical challenges, as pollutant concentration needs to be accurately predicted both in the near field and intermediate field. The active mixing close to the discharge can be modeled by proven plume models, while the fate and transport far beyond the mixing zone can be well-predicted by three-dimensional (3D) circulation models based on the hydrostatic pressure approximation. These models are usually applied separately with essentially one-way coupling; the action of the plume mixing on the external flow is neglected. Important phenomena such as surface buoyant spread or source-induced changes in ambient stratification cannot be satisfactorily addressed by such an approach. A Distributed Entrainment Sink Approach is proposed to model effluent mixing and transport in the intermediate field by dynamic coupling of a 3D far field shallow water circulation model with a Lagrangian near-field plume model. The action of the plume on the surrounding flow is modeled by a distribution of sinks along the plume trajectory and an equivalent diluted source flow at the predicted terminal height of rise. In this way, a two-way dynamic link can be established at grid cell level between the near and far-field models. The method is demonstrated for a number of complex flows including the interaction of a confined rising plume with ambient stratification, and the mixing of a line plume in cross flow. Numerical predictions are in excellent agreement with basic laboratory data. The general method can be readily incorporated in existing circulation models to yield accurate predictions of mixing and transport in the intermediate/far field.

An experimental study of the thermal plume developed above a variable cylindrical source of finite dimensions was conducted with the aim of verifying the corresponding point source model. The heat source was a 1 m diameter, 1 m high cylinder featuring five zones (four 0.25 m high cylindrical surfaces and a top disk) of identical surface area. Two different configurations were tested: in the first, only the top surface of the cylinder was heated and, in the second, both the top disk and the related cylindrical zone were heated. Surface temperatures were chosen to maintain the same source convective power for both situations. A battery of nine anemometric probes recorded simultaneously plume velocity and temperature distributions. These measurements allowed the plume thermal and dynamic radii above the source to be deduced. These radii vary linearly with height and they enable the plume virtual origin to be situated. If the virtual origin of each source is taken as a starting point, we observe that, in both test cases, the plumes develop in the same way, effectively validating the point source model. Velocity measurements also allowed the plume flow rate to be evaluated. The values found agree closely with those calculated using the relation that gives plume flow rate as a function of source convective power and height above the virtual origin.

International audience; Contaminant plumes (e.g., associated with leakages from municipal landfills) provide a source of natural electrical potentials (or “self-potentials”) recordable at the Earth's surface. One contribution to these self-potentials is associated with pore water flow (i.e., the “streaming potential”), and the other is related to redox conditions. A contaminant plume can be regarded as a “geobattery”: the source current potentially results from the degradation of the organic matter by micro-organisms, which produces electrons. These electrons are then carried by nanowires that connect bacteria and thorough metallic particles that precipitate in areas of strong redox potential gradient. In the case of the Entressen landfill (South of France), reported here, the hydraulic head differences measured in piezometers outside the contaminant plume is strongly linked to the surface self-potential signals, with a correlation coefficient of − 0.94. We used a Bayesian method that combines hydraulic head and self-potential data collected outside the contaminated area to estimate the streaming potential component of the collected self-potential data. Once the streaming potential contribution was removed from the measured self-potentials, the correlation coefficient between the residual self-potentials and the measured redox potentials in the aquifer was 0.92. The slope of this regression curve was close to 0.5, which was fairly consistent with both finite element modelling and the proposed geobattery model.

Tropospheric volcanic plume features have been derived from airborne multispectral images collected during field measurement campaigns at the Mt. Etna volcano in June 1997, during a quiescent period, and in July 2001 during an eruptive period. Results have been obtained in terms of mapping the volcanic aerosol optical thickness (AOT), the Angstrom parameters and the water vapor content using different bands from visible to infrared. The AOT values show average values of 0.1 and 1, for quiescent and eruptive plumes, respectively, demonstrating that this geophysical parameter well indicates a major contribution of particulates in the explosive plume with respect to the quiescent one. The mapping of Angstrom parameters, in the explosive case, indicates the presence of larger particles and their distribution along the plume, while in the quiescent case indicates the particle size is dominated by small particles with an effective radius about 1 μm. Further in the quiescent case, the map of water vapor shows low values indicating that water vapor emitted condenses mainly in aerosols.

This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present. The following may be inferred: (1) waves created a steep hydraulic gradient in the swash zone and a mild one landward of it; (2) waves increased the residence time of a plume when they broke seaward of it. They also created additional pathways for transport of the tracer to the beach surface; and (3) in the presence of a tide that completely covered the solute plume, overall, the waves increased the washout of the tracer from the intertidal zone of the beach in comparison with the no-wave case. The residence time of the tracer plume due to waves superimposed on the tide was estimated as 75% of that resulting from the tide with no waves. Discussion on scaling up the results and implications for bioremediation are also presented.

We consider the filling of a room with smoke from a small, centrally located floor fire. We present theoretical arguments for the behaviour of the filling time relative to the idealised ‘filling box time’ [Baines WD, Turner JS. Turbulent buoyant convection from a source in a confined region. J Fluid Mech 1969;37:51–80] as a function of the room height to width aspect ratio. Initially, the rate at which the smoke layer deepens is shown to be more rapid for relatively wide rooms (large aspect ratio). However, at larger times, relatively tall rooms (small aspect ratio) fill more rapidly due to large scale overturning and engulfing of ambient fluid. A series of experiments were performed to verify these results and showed good qualitative agreement with our theoretical predictions. The experiments were also used to evaluate the extent of deviation of the actual smoke front position from the idealised filling box model as a function of the aspect ratio.

A drag law accounting for Ekman rotation adjacent to a flat, horizontal bou\ud ndary is proposed for use in\ud a plume model that is written in terms of the depth-mean velocity. The drag l\ud aw contains a variable turning\ud angle between the mean velocity and the drag imposed by the turbulent bound\ud ary layer. The effect of the\ud variable turning angle in the drag law is studied for a plume of ice shelf wat\ud er (ISW) ascending and turning\ud beneath an Antarctic ice shelf with draft decreasing away from the groundi\ud ng line. As the ISW plume\ud ascends the sloping ice shelf–ocean boundary, it can melt the ice shelf, wh\ud ich alters the buoyancy forcing\ud driving the plume motion. Under these conditions, the typical turning ang\ud le is of order\ud 10° over most of\ud the plume area for a range of drag coefficients (the minus sign arises for th\ud e Southern Hemisphere). The\ud rotation of the drag with respect to the mean velocity is found to be signifi\ud cant if the drag coefficient exceeds\ud 0.003; in this case the plume body propagates farther along and across the b\ud ase of the ice shelf than a plume\ud with the standard quadratic drag law with no turning angle.

Changes in target surface morphology and ablation plume direction have been experimentally observed during the initial stages of the silicon laser ablation process. A relationship between both phenomena can be observed upon analysing the temperature field induced by the laser beam in a rough surface material. Theoretical studies on the deflection of the ablation plume are presented. These analyses are based on the hypothesis that particles that reach evaporation temperature will exit normally to the target surface with a velocity that is proportional to the surface temperature and the amount of the ablated material. Numerical solutions and experimental results of laser ablation process of silicon targets are found to agree with theoretical studies.

New field data on cohesive sediment erosion is presented and discussed, with particular focus on partitioning the total erosion into resuspension and bed load. The data were obtained using a recently developed in situ flume of the National Institute of Water and Atmospheric Research, New Zealand. The erosion rate is estimated from direct measurements of bed surface elevations by acoustic sensors, whereas resuspension rate is obtained using data on sediment concentrations measured by optical backscatter sensors. The bed- load contribution to the total erosion rate is evaluated from the conservation equation for sediments. To test repeatability, the data from the in situ flume are compared with those from a previous version of the flume. The results show that comparative studies of in situ flumes and standardized deployment procedures enable direct comparison of experimental data on cohesive sediment erosion. Overall, the data show that a commonly used assumption that the erosion rate is equal to the resuspension rate is not always valid as bed load plays a significant role in cohesive sediment erosion. The data also highlight the importance of clay content and other sediment physical characteristics in the sediment mixture.

Summary We investigated the potential thermal impacts from below-water-table aggregate extraction on a cool-water stream supporting Brook trout (Salvelinus fontinalis) and cool-water macroinvertebrates. We monitored thermal plumes emanating from an aggregate pit through an unconfined, glacial-outwash aquifer. Our objectives were to complete a detailed assessment to quantify the persistence of thermal plumes in the subsurface, and establish a framework for guiding these investigations as the growing demand for aggregate increases pressures to pursue extraction in ecologically sensitive areas. During a 10-year period, we measured ground and surface water temperatures in an outwash aquifer and cool-water stream, including two periods of intensive monitoring (22 months and 2.5 years) focusing on plume movement from one aggregate pit. We quantified the aquifer hydraulic conductivity K at the laboratory and field scale, and characterized the effective thermal conductivity λ at an unprecedented level of detail. The mean K’s from the multi-scale tests span two-orders of magnitude, 1.8 × 10−4 to 1.7 × 10−2 m s−1, and are related to the test support volume. The saturated λ has a mean of 2.42 W m−1 K−1, ranges from 2.14 to 2.69 W m−1 K−1, and is correlated to stratigraphic units (gravel, sand, and till). The annual temperature amplitude in the pit is 10 °C above up gradient ground water, and our results show that alternating warm and cool plumes persist in the aquifer for 11 months and migrate up to 250 m down gradient. The observed plume velocity (1.2 m d−1) lags the ground water velocity (2.8 m d−1) due to thermal retardation. Furthermore, hydraulic conductivity is shown to vary with the scale of the test and ground water velocities estimated from pumping tests may overestimate thermal plume velocities. While we focused on plume migration, our results demonstrate that assessing impacts on the aquatic community requires an integrated, multi-disciplinary study. This work can guide such assessments.

Dissolved iron (Fe) speciation in the Columbia River plume, the San Francisco Bay plume, and the Columbia River estuary was investigated using competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) with the added ligand salicylaldoxime. A stronger L1-type Fe-binding ligand class was measured in all surface samples, and in the Columbia River estuary. A weaker L2-type ligand class was present in the far-field Columbia River plume and the San Francisco Bay plume but was not observed in the low-salinity (S = 1.4-22.5) waters of the near-field Columbia River plume or estuary. Concentrations of total dissolved Fe were correlated with the concentrations of the stronger L1-type ligand in nonestuarine (S > 13) surface samples. Leachable particulate (>0.4 µm) Fe concentrations in the Columbia River plume were measured to supplement existing data from the San Francisco Bay plume. There is a large concentration of readily leachable particulate Fe in the two plumes, yet it is the concentration of ambient L1-type ligands that appears to dictate the concentration of dissolved Fe in these waters and, consequently, the supply of dissolved Fe to neighboring coastal waters. The correlation between dissolved Fe and L1 ligand concentrations in both plume waters, as well as in California Current and upwelled surface waters, suggests that this relationship will persist in other coastal environments and should be considered when evaluating and modeling coastal Fe cycling and supply.

Since the physics of air entrainment is not yet clearly understood, most of the fire plume expressions reported in the literature were derived empirically. Experiments with different fire geometry, fuels, and ambient conditions would be difficult when trying to derive comprehensive plume temperature and velocity fields from existing theories. Computational fluid dynamics (CFD), a practical engineering tool in fire engineering, might give a better understanding of the plume behavior. This technique can eliminate factors which are difficult to control in experiments, but would affect the plume movement. Aerodynamics for thermally induced plumes is studied by CFD in this article. Three types of thermal plumes such as axisymmetric plume, balcony spill plume, and door plume are considered. Four axisymmetric plume equations and three balcony spill plume models are assessed by comparing with the CFD results. For door plumes, qualitative results of the mass entrainment rate are obtained. Investigations in this article are useful for fire engineers in designing smoke management systems in an affordable fashion. This is a critical point in implementing an engineering performance-based fire code.

We use magnetic field-aligned mapping between the ionosphere and the magnetosphere to intercompare ground-based observations of storm enhanced density (SED), and plasmasphere drainage plumes imaged from space by the IMAGE EUV imager, with the enhanced inner-magnetosphere/ionosphere SAPS electric field which develops during large storms. We find that the inner edge of the SAPS electric field overlaps the erosion plume and that plume material is carried sunward in the SAPS overlap region. The two phenomena, SED in the ionosphere and the erosion plume at magnetospheric heights, define a common trajectory for sunward-propagating cold plasma fluxes in the midnight—dusk–postnoon sector. The SAPS channel at ionospheric heights and its projection into the equatorial plane serve to define the sharp outer boundary of the erosion plume. The SAPS electric field abuts and overlaps both the plasmasphere boundary layer and the plasmasphere erosion plume from pre-midnight through post-noon local times.

Turbulent buoyant plumes in cold fresh water are analysed, assuming a quadratic dependence of density on temperature. The model is based on the assumption that entrainment velocity is proportional to vertical velocity in the plume. Numerical and asymptotic solutions are obtained for both rising and descending plumes from virtual sources with all possible combinations of buoyancy, volume and momentum fluxes. Physical sources can be identified as points on trajectories of plumes from virtual sources.The zero-buoyancy condition, at which the plume and the ambient have equal densities but their temperatures are on opposite sides of the temperature of maximum density, is of particular importance. If an upwardly buoyant plume rising through a body of water reaches the surface before passing through its zero-buoyancy level, it will form a surface gravity current; otherwise, the plume water will return to the source as a fountain. The height at which zero buoyancy is attained generally decreases as the source momentum flux increases: greater plume velocity produces greater entrainment and hence more rapid temperature change. Descending plumes, if ejected downwards against upward buoyancy, may be classified as strongly or weakly forced according to whether they reach the zero-buoyancy condition before being brought to rest. If they do, they continue to descend with favourable buoyancy; otherwise, they may form an inverted fountain. Once a descending plume has attained downward buoyancy, it can continue to descend indefinitely, ultimately behaving like a plume in a fluid with a linear equation of state. In contrast, a rising plume will eventually come to rest, however large its initial upward buoyancy and momentum fluxes are.

Building fires go through a series of stages. They start with a fire plume period during which buoyant fire smoke rises to the ceiling. A second stage is the following enclosure smoke-filling period. In this paper, the first stage is the subject, especially for the fire plume behavior in thermally stratified environments in large volume spaces. In NFPA 92B, Morton's integral equation was introduced for calculating the maximum plume rise, and beam smoke detectors were recommended for smoke detection design. In this work, experiments and CFD simulations were conducted in a small-scale enclosure and a large space to investigate early fire movements in temperature-stratified ambients. The results show that in a thermally stratified environment, the axial temperature and velocity of a fire plume decrease more quickly along the vertical axis than in uniform environment, and in some cases the fire plume ceases to rise. The previous integral equation was shown to underestimate the actual maximum height of a fire smoke plume, and also was unable to explain the differences of the maximum heights of low-density and high-density smoke plumes with the same stratification and outlet conditions. The integral equation was improved by introducing two correction factors, and extended for non-linear temperature stratified environments. A light section smoke detection method with three space-protected area was suggested and discussed.

Following the cessation of dewatering in the southern part of the Durham Coalfield in 1974, groundwater levels rose in both the mine workings and the overlying Magnesian Limestone Aquifer (MLA). A pollution plume has since been migrating through the MLA, with sulphate concentrations greatly exceeding potable water standards. Prediction of future plume development requires specification of whether upflow of mine water to the MLA occurs from a small number of point sources or in a diffuse manner (i.e. distributed over most of the area in which the MLA is underlain by mineworkings). A programme of conceptual and numerical modelling has addressed this issue. Mine plans and geological information were used to characterize the flooded mine system and its interface with the MLA. Piezometric and meteorological data were used to constrain finite difference simulations of groundwater flow in the MLA. Flow velocity vectors derived from these flow simulations allowed modelling of plume migration by solution of the advection–dispersion equation. The results of these simulations illustrate that it is necessary to invoke both point and diffuse upflow to explain the observed patterns of pollutant migration to 2003. Predictive modelling of further plume migration indicates that sulphate concentrations are likely to rise to unacceptable levels in the most proximal public supply wells within the next two decades.

This study investigated mass transport near trenches designed to capture contaminated groundwater. Numerical models simulated migration of contaminant plumes toward trenches oriented perpendicular to regional groundwater flow, partially penetrating a hypothetical unconfined aquifer. Plumes originated at the top of the simulated groundwater flow system. The smallest trench necessary to capture a contaminant plume was identified for various sets of mass transport parameters. Results suggest that, in predominantly horizontal flow systems such as those simulated here: (i) vertical hydraulic conductivity has relatively little effect on downward propagation of contaminant plumes and required trench size, (ii) transverse vertical dispersivity exerts significant control on plume and trench depth, and (iii) recharge dilutes and thus reduces plume and trench width, but may induce downward vertical hydraulic gradients that deepen plumes and trenches. For all cases considered, trenches oriented perpendicular to regional groundwater flow, placed close to the leading edge of a contaminant plume, and sized slightly larger than the plume (in transverse cross-section) facilitate plume capture.

On the basis of a combination of laboratory microcosm experiments, column sorption experiments, and the current spatial distribution of groundwater concentrations, the origin of a mixed brominated ethene groundwater plume and its degradation pathway were hypothesized. The contaminant groundwater plume was detected downgradient of a former mineral processing facility, and consisted of tribromoethene (TriBE), cis-1,2-dibromoethene (c-DBE), trans-1,2-dibromoethene (t-DBE), and vinyl bromide (VB). The combined laboratory and field data provided strong evidence that the origin of the mixed brominated ethene plume was a result of dissolution of the dense non-aqueous-phase liquid 1,1,2,2-tetrabromoethane (TBA) atthe presumed source zone, which degraded rapidly (half-life of 0.2 days) to form TriBE in near stoichiometric amounts. TriBE then degraded (half-life of 96 days) to form c-DBE, t-DBE, and VB via a reductive debromination degradation pathway. Slow degradation of c-DBE (half-life220 days), t-DBE (half-life 220 days), and VB (half-life220 days) coupled with their low retardation coefficients (1.2, 1.2, and 1.0 respectively) resulted in the formation of an extensive mixed brominated ethene contaminant plume. Without this clearer understanding of the mechanism for TBA degradation, the origin of the mixed brominated ethene groundwater contamination could have been misinterpreted, and inappropriate and ineffective source zone and groundwater remediation techniques could be applied.

We carried out a field study of the plume discharged by a near-shore wastewater outfall near the Akashi Strait, Japan. Using an Acoustic Doppler Current Profiler and a tow-body CTD, we measured the near-surface salinity and temperature fields in the region throughout an M2 tidal cycle. We filtered the data in T–S space to remove water masses other than the wastewater, and then used the adiabatic mixing assumption to calculate the concentration of wastewater in the far field of this plume. Averaging the T–S fields of repeated surveys over a time period during which the tidal regime did not change substantially, allowed comparison of the time-averaged plume with the analytical solution for a plume diffusing in both the horizontal and vertical dimensions. The resulting vertical turbulent diffusion coefficients agreed well with those resulting from Thorpe scales determined via a vertically-profiling CTD, as well as with the canonical value for open channel flow of Dz = 0.067hu*. The corresponding horizontal turbulent diffusion coefficients, however, were two orders of magnitude larger than those typically observed in straight channels, and an order of magnitude larger than those observed in meandering rivers. This is likely a result of enhanced horizontal mixing due to barotropic eddies generated by the interaction of strong tidal flow with headlands and levees, as well as due to the time-varying nature of tidal flow, and baroclinic spreading of the buoyant wastewater plume.

The writers present a one-dimensional integral model to describe multiphase plumes discharged to quiescent stratified receiving waters. The model includes an empirical submodel for detrainment, and the capability to include dispersed phase dissolution. Model equations are formulated by conservation of mass, momentum, heat, dissolved species concentration, and salinity, and allow the tracking of dissolved material and changes in plume density due to solute density effects. The detrainment (or peeling) flux, Ep , is assumed to be a function of the dispersed phase slip velocity, ub , the integrated plume buoyancy, Bi , and the momentum of the entrained plume fluid, characterized by the fluid velocity, ui , given by the general relationship Ep =e( ub ∕ ui )2 ( Bi ∕ ui2 ) . The parameter e is calibrated to laboratory experimental data. Because Ep is based on a force balance, this algorithm allows numerical models to reproduce a wide range of characteristic plume behavior. Such a predictive algorithm is importa...

The dynamics of a sea breeze front interacting with the heavily urbanized New York City area are examined. In addition, we investigate the impact of the urban-influenced sea breeze front on transport and diffusion of simulated passive tracer plumes. We employ the U. S. Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®—a registered trademark of the Naval Research Laboratory) to perform a nested simulation with data assimilation for the sea breeze event of 9 August 2004. Available surface and upper-air observations are used to validate the simulation. We also perform a sensitivity study in which the urban influence is removed (no-urban). The sea breeze front has characteristics of a density current, including an elevated head at the leading edge. The density current moves slowly and unevenly across the city. Kelvin–Helmholtz billows form in the region of the density current head, and the results show evidence of the occurrence of Kelvin–Helmholtz instability (KHI). The density current head is greatly elevated owing to the enhanced surface drag of the urban area. This urban influence is further explored in the no-urban simulation, in which the head of the density current is not elevated to the same degree and KHI does not occur. The sea breeze/density current has a large impact on transport and diffusion of simulated tracer plumes, not only changing the direction of plume motion due to the wind shift but also redistributing tracer material in the vertical so as to produce dramatic, rapid changes in near-surface concentration as the front passes. In particular, large upward vertical velocity at the head of the density current advects tracer material to large elevations, greatly reducing near-surface concentration. After passage of the front, tracer is released into the shallow density current and confined near the surface, enhancing near-surface concentrations. KHI results in turbulent mixing at the upper surface of the plume, allowing for a small reduction in near-surface concentration. Published in 2007 by John Wiley & Sons, Ltd.

Within the framework of the HPF project (Hyperalkaline Plume in Fractured Rock) at the Grimsel Test Site (Switzerland), a small scale core infiltration experiment was performed at the University of Bern. A high-pH solution was continuously injected, under a constant pressure gradient, into a cylindrical core of granite containing a fracture. This high-pH solution was a synthetic version of solutions characteristic of early stages in the degradation of cement. The interaction between the rock and the solutions was reflected by significant changes in the composition of the injected solution and a decrease in the permeability of the rock. Changes in the mineralogy and porosity of the fault gouge filling the fracture were only minor. One-dimensional reactive transport modeling, using a modified version of the GIMRT code, was used to interpret the results of the experiment. Dispersive and advective solute transport, mineral reaction kinetics and a coupling between porosity and permeability changes were taken into account. In order to obtain a reasonable agreement between models and experimental results, reactive surface areas of the order of 10 5 m 2 /m 3 rock had to be used. These values are much smaller than the values measured for the fault gouge filling the fracture, which are in the order of 10 6 –10 7 m 2 /m 3 rock. However, the results could be improved by adding a small fraction of fine grained mineral, which could explain the high initial peaks in Al and Si concentration. With the inclusion of this fine grained fraction, the initial surface areas in the model were within the range of the measured specific surface areas of the fault gouge. The fact that the decrease in permeability was significant despite the minor changes in mineralogy, suggests that permeability may be controlled by changes in the structure of the rock (pore geometries) rather than by only the bulk volumetric (porosity) changes.

This thesis focuses on the convective flow induced by a heated isotherm wall. A turbulent boundary layer develops along this wall, and resembles to a plume unlike its typical characterics are significantly modified by the boundary condition at the wall. In this study the environment is a closed box in which the lighter fluid continuously accumulates in the upper part, thus producing a temperature stratification in the interior. In order to better understand the dynamics of such a plume as well as its interaction with the ambient fluid, we deploy an approach that is both experimental and theoretical. Concerning the experiments, we developed a technique which combines Particle Image Velocimetry (PIV) with Laser Induced Fluorescence (LIF). This technique allows to simultaneously acquire the velocity and the temperature of the fluid in a plane which covers the entire flow. As concerning the theory, a one-dimensional numerical model is developed. It is based on the entrainment theory by Morton et al (1956) as for the turbulent part of the plume, and it takes into account the initial laminar character of the plume thanks to similarity solutions. The detailed comparisons between this model and the experimental results show the limits of the classical models and the relevance of the introduced improvements. In particular we evaluate the contribution of the laminar part and we highlight that the entrainment coefficient varies as a function of the ambient stratification.; Cette thèse s'intéresse à l'écoulement convectif induit par une paroi chauffante isotherme. La couche limite turbulente qui s'établit le long de celle-ci s'apparente à un panache, bien que les conditions de paroi en modifient significativement certaines caractéristiques typiques. Dans l'étude présentée, l'environnement est un milieu clos. Puisque le fluide de moindre densité s'accumule dans la partie haute de l'enceinte, une stratification en température s'établit. Afin de mieux comprendre les mécanismes qui entrent en jeu dans ce type de panache et son interaction avec le fluide ambiant, nous déployons une approche à la fois expérimentale et théorique. Sur le plan expérimental, une technique combinant Velocimétrie par Images de Particules (PIV) et Fluorescence Induite par Laser (LIF) est mise au point, et permet d'acquérir simultanément la vitesse et la température du fluide dans un plan de mesure qui couvre l'ensemble de l'écoulement. Sur le plan théorique, un modèle numérique mono-dimensionnel est développé. Il est basé sur la théorie d'entraînement de Morton et al (1956) pour la partie turbulente du panache, et tient compte de son caractère laminaire initial grâce à des solutions de similarité. Les comparaisons détaillées entre ce modèle et les résultats expérimentaux montrent les limites des modèles classiques et la pertinence des améliorations introduites. Nous évaluons notamment la contribution de la portion laminaire, et mettons en évidence le fait que le coefficient d'entraînement varie en fonction de la stratification ambiante.

Colloque avec actes et comité de lecture. Internationale.; International audience; La Méthode Énergétique Simplifiée (MES) développée au laboratoire LTDS se prête bien à la description énergétique de phénomènes acoustiques dans une cavité. Considérée sous sa forme différentielle discrétisée, elle est proche d’une méthode de tirs de rayons énergétique ; en cela, elle est relativement sensible à la formulation des réflexions aux parois, qui sont le plus souvent représentées au moyen d’une directivité lambertienne. Si cette directivité donne de bons résultats pour l’expression du champ réverbéré, elle occasionne en revanche des approximations importantes pour le champ direct. La méthode mixte proposée ici permet d’exprimer le champ direct au moyen d’une formulation par éléments de frontière (BEM), tout en gardant une formulation énergétique pour le champ réverbéré. On atteint ainsi un bon compromis entre le temps de calcul et la précision requise.

The method outlined provides for emission factor measurements to be made for unmodified vehicles driving under real world conditions at minimal cost. The method consists of a plume capture trailer towed behind a test vehicle. The trailer collects a sample of the naturally diluted plume in a 200 L conductive bag and this is delivered immediately to a mobile laboratory for subsequent analysis of particulate and gaseous emissions. The method offers low test turnaround times with the potential to complete much larger numbers of emission factor measurements than have been possible using dynamometer testing. Samples can be collected at distances up to 3 m from the exhaust pipe allowing investigation of early dilution processes. Particle size distribution measurements, as well as particle number and mass emission factor measurements, based on naturally diluted plumes are presented. A dilution profile relating the plume dilution ratio to distance from the vehicle tail pipe for a diesel passenger vehicle is also presented. Such profiles are an essential input for new mechanistic roadway air quality models.

L'etude numerique du comportement d'un panache gazeux et d'un nano-agregat crees lors l'ablation laser par impulsions. courtes est etudiee par la methode de dynamique moleculaire. Lors de l'evolution d'une nanoparticule, deux phenomenes coexistent: l'agglomeration (ou agregation) et l'evaporation. La temperature seuil de la nanoparticule a partir de laquelle l'evaporation predomine est ainsi determinee. La presence du panache gazeux modifie ce comportement. D'autre part la condensation de ce gaz est un parametre non negligeable dans la poursuite de cette etude.

Numerical simulation is used to examine the relative velocities of DNAPL and aqueous phase plumes in sandy aquifers where lateral spreading of DNAPL has occurred at the base of the aquifer. The scenario being modeled is one where a permeable aquifer is underlain by a sloping aquitard, which results in lateral migration of the DNAPL down the slope, in addition to lateral migration of an aqueous phase plume subject to a specified hydraulic gradient. A sensitivity analysis is presented to the impacts of both DNAPL properties and geologic properties. The most important chemical properties governing the relative velocities of the DNAPL and the shallow aqueous phase plume are the DNAPL viscosity and the aqueous component soil–water partition coefficient (Kd). The dip of the underlying aquitard was found to be relatively unimportant, at least for the range of values studied. The scenario under consideration can be important in conceptual model development and remedial design, as in certain cases DNAPL could be migrating in areas without the evidence of a well-developed aqueous phase plume. The implication of this work is that the absence of a shallow aqueous phase plume directly downgradient of a DNAPL source zone does not rule out the possibility of deep occurrences of DNAPL beyond the shallow monitoring well network. A further finding of this study is that the occurrence of a highly sorbing compound in groundwater at virtually any concentration may indicate the immediate upgradient presence of residual or pooled DNAPL.

To understand the dispersal pattern of sediment plume and its controlling processes, a field experiment of concentrated slurry dispersal created by a dredger was conducted in the Changjiang (Yangtze River) Estuary during the 2002 flood season. An acoustic suspended sediment concentration profiler and an acoustic Doppler profiler were deployed to simultaneously observe suspended sediment concentrations (SSC) and tidal currents at the pre-selected sections shortly following the release of dredged materials. Water sampling, grab sampling and shallow coring were simultaneously carried out to obtain the SSC and grain-size texture. High-resolution SSC profiler observations showed that two distinct sediment plumes (middle level- and near-bed plumes) occurred during the intermediate tidal phase between the spring and neap due to differential settling of the sediment mixture, whereas only a benthic plume occurred due to rapid flocculation settling during the neap tide. Three subsequent stages can be identified during the dispersal of the sediment plume: (1) initially stable stage before the release; (2) unstable stage shortly following the release as a settling cloud; and (3) stable stage after the formation of a primary lutocline or a benthic plume. Enhanced mixing due to oscillatory shear flows could raise only the elevation of the lutocline in the slurry, but could not enhance the transport capacity of suspension. In the presence of high concentration, the fate of bottom sediment plume was controlled by the bottom stress, independent of the interfacial mixing.

A study of the evolution of microplasmas produced on aluminum alloy surface at ambient air pressure by 266-nm 10-ns laser pulses with energies of 3 to 100 muJ (2 to 68 GW/cm2) is carried out. Gated photography with a minimum width of 5 ns is used to investigate the plasma evolution. Plasma emission and plasma distances from the sample surface are investigated as a function of time. Pulse energy has a strong effect on plasma emission particularly at short delay times. The experimental results are compared with a simplified model of plume expansion

The shelf-slope front (SSF) located off the northeastern United States and Canada is an oceanographic front separating colder and less-saline continental shelf waters from generally warmer and more-saline slope waters over the continental slope. The surface expression of the SSF is visible year-round using sea-surface temperature (SST) data obtained from satellite-based infrared radiometers. Availability of 20 years (1973–1992) of SSF positions, digitized from weekly satellite-derived SST charts between 75 ∘ and 50 ∘ W longitude, allows a detailed spatial analysis of the seasonal variability of the SSF position between Cape Hatteras and the Tail of the Grand Banks. Results show an overall maximum seaward (shoreward) extent during winter (summer), consistent with earlier work. However, our more detailed spatial analysis shows that the eastern-most and western-most monthly SSF anomalies, relative to the long-term (1973–1992) mean, are 180 ∘ out of phase, with maximum seasonal SSF variability of O ( ± 50 km ) occurring generally east of 58 ∘ W . Furthermore, seasonal westward propagation of the seaward-most (landward-most) SSF position is evident between 50 ∘ and 58 ∘ W from November to April (May–October), decreasing in amplitude towards the west. A simple Ekman coastal plume model incorporating gridded wind-stress anomalies and a constant plume depth ( h c = 25 m ) reproduces the general seasonal cycle of the SSF along with the east-west phase shift, except in easternmost regions where SSF positional variability is maximal. The east-west phase shift results from interaction between the slowly varying (in space) wind-stress anomalies and the abrupt change in orientation of the mean along-SSF direction, from a mean of 81 . 8 ∘ ± 14 . 3 ∘ T between 50 . 5 ∘ and 70 . 5 ∘ W , to a mean of 51 . 3 ∘ ± 24 . 0 ∘ T between 70 . 5 ∘ and 74 . 5 ∘ W . A more complex Ekman coastal plume model that allows the upper layer to evolve to a uniform thickness through shear-induced mixing and a critical Richardson number criterion ( h c = variable ), overestimates onshore movement of the SSF south of Nantucket Shoals by a factor of 2–3 compared to August–October observations. While clearly not locally wind-forced, we speculate that a possible source of the seasonal, westward-propagating SSF meander is due to seasonal variability in the volume of shelf waters within this eastern-most region resulting from Labrador Current transport that is maximum (minimum) during fall (spring) upstream of the Tail of the Grand Banks and within the Labrador Sea. Comparisons of the seasonal movements of the satellite-derived surface SSF position with previously published sub-surface expressions of the SSF and shelf water volumes derived from hydrographic data collected within the Middle Atlantic Bight section of our domain, demonstrate decoupling of the surface wind-forced SSF from the sub-surface thermohaline-forced SSF over seasonal timescales for this westernmost region.

Transport of larger smoke particles generated by a fire in a compartment is studied. An atrium fire with three different heat release rates is taken as an example. The air flow pattern and temperature contours are predicted by a fire field (or application of computational fluid dynamics (CFD) model. The paths of smoke particles are modeled by the Lagrangian method coupled with the air movement induced by hot smoke. Distribution of smoke particles and their trajectories are then calculated. By superimposing the trajectories of particles of different sizes, the shape of the smoke plume is observed.

Plume meandering and averaging time effects were measured directly using a high spatial resolution, high frequency, linescan laser-induced fluorescence (LIF) technique for measuring scalar concentrations in a plume dispersing in a water channel. Post-processing of the collected data removed time dependent background dye levels and corrected for attenuation across the laser beam to produce accurate measurements over long sample times in both a rough surface boundary-layer shear flow and shear free grid-generated turbulent flow. The data were used to verify the applicability of a meandering plume model for predicting the properties of mean and fluctuating concentrations. The centroid position of the crosswind concentration profile was found to have a Gaussian probability density function and the instantaneous plume spread about the centroid fluctuated log-normally. A modified travel-time power law model for averaging time adjustment was developed and compared to the widely used, but much less accurate, 0.2 power-law model.

The dispersion of salt water carefully introduced into fresh water closely simulates the dispersion of hot exhaust gases in fire plumes. The salt concentration downstream of the source and exhaust gas temperature downstream of the flame zone behave like passive scalars and are transported by similar turbulent convective and diffusive processes. Transport properties of buoyant plumes are investigated through quantitative visualization of the distinctive turbulent structures responsible for dispersion in these flows. Turbulent mixing patterns are visualized via Planar Laser Induced Fluorescence (PLIF). This technique uses a laser light sheet to excite a fluorescent dye tracer suspended in the salt-water solution allowing visualization of a particular plane of the flow. The intensity of the fluorescence is proportional to the concentration of the salt water providing quantitative instantaneous field measurements of flow dispersion. Canonical flows including the unconfined plume and the impinging plume are carefully characterized and compared with fire scaling laws and fire measurements to validate the quantitative implementation of the PLIF salt-water technique.

The influence of the initial plume scale on the early time variability in cumulative solute mass across a control plane for advection dominated nonreactive solute movement in a heterogeneous three-dimensional aquifer is investigated. Under an assumption of a Gaussian velocity distribution, the closed-form expressions for the early time probability distribution function of travel times and coefficient of variation of cumulative solute mass are derived for the case of statistically isotropic media as functions of the initial plume size, the variance of the log hydraulic conductivity, the correlation scale of the log hydraulic conductivity, and the mean longitudinal velocity. These results are achieved by invoking a modified variance of longitudinal velocity, accounting for the influence of a finite domain size. It is found that at early time, the initial plume size has significant influence on the variability in cumulative solute mass in the case of a finite volume source. The presented methodology can be extended to statistically anisotropic media.