Tall Stacks Research Articles

A practical model for the calculation of σy and σz for use in an on-line gaussian dispersion model for tall stacks, based on wind fluctuations

A practical model is proposed for estimating hourly dispersion parameters σ y and σ z directly from wind fluctuations for use in an on-line dispersion model for tall stacks. Taylor's formulation is used to calculate σ y and σ z , both σ v , σ w and the time scale of turbulence T 1 are derived from simple lateral wind measurements. This is done by separating the fluctuations of the wind direction into a stability dependent and a non-stability dependent part. Stability classes or other stability parameters are not applied. In well defined conditions there is a good agreement with the Pasquill dispersion curves using the Pasquill-Gifford-Turner (PGT) stability determination. In more complicated situations our model gives significant improvements. During the daytime the PGT method estimates stability as neutral over many hours. This is also the case at night, when the atmosphere is more stable than is assumed by the PGT method and other methods using cloud cover.

The effect of meso-scale flows on regional and long-range atmospheric transport in the western Mediterranean area

Experimental evidence accumulated over the years indicates that the formation of the Iberian thermal low on summer days is intimately associated with complex dispersion behavior of atmospheric pollutants emitted within the whole of Spain and in particular for those emitted in the coastal areas. The project “Mesometeorological Cycles of Air Pollution in the Iberian Peninsula”, sponsored by the CEC, is intended to study the origin and evolution of the atmospheric circulations responsible for the observed behaviour, and document their importance in Spain and in the Mediterranean basin as a whole. To characterize the processes involved, tall stack plumes from four sites in Spain have been tracked with COSPEC remote sensors and used as tracers of opportunity of the flow at their level. This information is being combined with available historical meteorological data to compose a mosaic of atmospheric circulation patterns for the whole of the Iberian peninsula and surrounding regions. The analysis performed to date confirms that: (a) the formation of the thermal low on summer days forces an inward flow of the coastal emissions towards the central plateau, (b) this convergence occurs at the peninsular level, (c) the inflow is mostly ageostrophic and strongly channelled along natural mountain passes, and (d) the marine airmass pulled inland along the Spanish east coast is highly enriched with O 3. The latter, (d), appears to indicate that a compensatory flow to the thermal low is provided by subsidence over the colder waters of the Gulf of Lyon and northwestern Mediterranean area. In turn, this favors the formation of northeasterly winds along the Spanish east coast during the night, and may explain the O 3 levels as a result of regional transport of precursors from source regins in this general area.

Metal contamination in liver and muscle of northern pike (Esox lucius) and white sucker (Catostomus commersoni) and in sediments from lakes near the smelter at flin flon, manitoba

AbstractNorthern pike (Esox lucius Linnaeus), white sucker (Catostomus commersoni Lacépède) and sediment cores were obtained from 13 lakes located 4.5 to 84 km from the base metal smelter at Flin Flon, Manitoba, Canada. Zn, Cu, Cd, Hg, Se, Pb and As concentrations were determined in liver and muscle of fish. Depth profiles of Zn, Cu, Cd, Hg and Se concentrations were determined in sediment cores. The area receiving significant metal deposition from the smelter is smaller than previously estimated. Increases in metal concentrations in depth profiles of sediment cores appear to coincide with the onset of smelting operations at Flin Flon. Metal concentrations in fish from two lakes near the smelter dropped between 1976 and 1982, after a tall stack (250 m) was installed on the smelter. Metal concentrations in muscle were poor indicators of metal concentrations in sediments. Concentrations of Cd and Se in liver of northern pike, and concentrations of Zn, Cu, Cd and Se in liver of white sucker were greatest in the most contaminated lakes. Concentrations of Hg in fish declined with increased proximity to the smelter. Limnological variables seemed to have little influence on metal concentrations in fish.

IMPACT OF FOSSIL POWER PLANTS ON AIR QUALITY

South Africa has abundant supply of coal, about half being used in generation of electricity. Use of low grade high ash coal results in about 25% leaving boilers as PFA but ESP's lowers quantity emitted to air considerably.
 Lower sulphur coal increases ash resistivity, inhibiting precipitator effectiveness. Various solutions tested by Eskom through the 80's include electrical improvements and ash modification. S03 injection equipment is effective at two Eskom stations in reducing dust emission to acceptable levels. General perception of poor dust emission is a stack that has visible emission. This could be a subjective view without real basis.
 Gas emissions include vast volumes of SOX and NOx, with no steps taken to attenuate. Then is obviously a difference between high level and pound level phenomena. It was previously assumed that emission of pollutants via tall stacks above inversion layers into the jet-stream would avoid pollution problems. This does not appear in practice to have resulted, as low level haze appears to be increasing and impact of high level gas emission is now being investigated. Installation of gas removal plant may help the air quality, but may be unaffordable.
 Greater demands for wealth and jobs results in greater industrialisation, with accompanying pollution products. Also, provision of living wages and housing scheme benefits has seen development of whole new black residential areas where coal is not burned, giving clean air living areas for these people and their neighbours.

On a Strategy for Reducing Short-range Daytime Ground Level Concentrations Due to Emissions from Very Tall Stacks

A procedure with a potential for increasing the duration of tall stack plumes residency within elevated stable layers, outlined schematically. The suggested procedure considers the temporal and spatial behavior of the atmospheric boundary layers (ABL). It takes advantage of the fact that under adverse dispersion conditions, due to relatively shallow ABL, injection of the plume into the capping stable layer above the ABL, may be achieved by a modification of the emission parameters. When successfully applied it will undoubtedly lead to an increase in the time a plume travels within an elevated stable layer, thus ensuring reduced ground-level concentrations as compared to plumes trapped within shallow ABLs. The reduction may be from extremely high concentrations to extremely low concentrations. Application of the strategy is most attractive when the near-stack area is a residential area, while at greater distances from the stack the population is sparse. The technology and engineering involved with increasing emission parameters requires special attention, while the current state-of-the-art tools for forecasting the morning depth of the ABL are quite credible. The proposed strategy has the sole purpose of improving near-field ground-level air quality, in a particular set of meteorological conditions, while retaining the emission rate of gasesmore » or even reducing them when compared to normal emission levels.« less

Nonmethane Organic Compound to Nitrogen Oxide Ratios and Organic Composition in Cities and Rural Areas

The observed ranges in nonmethane organic compound (NMOC) concentrations, NMOC composition and nitrogen oxides (NOX) concentrations have been evaluated for urban and nonurban areas at ground level and aloft of the contiguous United States. The ranges in NMOC to NOX ratios also are considered. The NMOC composition consistently shifts towards less reactive compounds, especially the alkanes, in air parcels over nonurban areas compared to the NMOC composition near ground level within urban areas. The values for the NMOC to NOX ratios, 1.2 to 4.2, in air aloft over nonurban areas are lower than in air at ground level urban sites, ≥8, and much lower than in air at ground level nonurban sites, ≥20. The layers of air aloft over a number of nonurban areas of the United States tend to accumulate NOX emissions from the tall stacks of large fossil fuel power plants located at nonurban sites. During the night into the morning hours, the air aloft is isolated from any fresh NMOC emissions predominately coming from near surface sources. Conversely, during this extended period of restricted vertical mixing, air near the surface accumulates NMOC emissions while this air is isolated from the major NOX sources emitting aloft. These differences in the distribution of NMOC and NOX sources appear to account for the much larger NMOC to NOX ratios reported near ground level compared to aloft over nonurban areas. Two types of experimental results are consistent with these conclusions: (1) observed increases in surface rural NOX concentrations during the morning hours during which the mixing depth increases to reach the altitude at which NOX from the stacks of fossil fuel power plants is being transported downwind; (2) high correlations of total nitrate at rural locations with Se, which is a tracer for coal-fired power plant NOX emissions. The implications of these conclusions from the standpoint of air quality strategies are suggested by use of appropriate scenarios applied to both urban and regional scale photochemical air quality models. The predictions from urban model scenarios with NMOC to NOX ratios up to 20 are that NOX control will result in the need for the control of more NMOC emissions than necessary in the absence of NOX control, in order to meet the O3 standard. On a regional scale, control of NOX emissions from fossil fuel power plants has little overall effect regionally but does result on a more local scale in both small decreases and increases in O3 concentrations compared to the baseline scenario without NOX control. The regional modeling results obtained to date suggest that NOX control may be effective in reducing O3 concentrations only for a very limited set of conditions in rural areas.

Comments on “Prediction of Wind Speed, Direction and Diffusivity under Neutral Conditions for Tall Stacks”

Comments on “Prediction of Wind Speed, Direction and Diffusivity under Neutral Conditions for Tall Stacks”

The validity of a Gaussian plume model when applied to elevated releases at a site on the Canadian shield

It is shown that while a standard Gaussian plume model can predict annual mean concentrations of a gas released from a tall stack on the Canadian Shield within a factor of two, the probability of achieving this level of agreement for hourly averages is 20–30% with no significant correlation between individual hourly observations and predictions ( r 2 = 0.08). The probability, however, increases to 50% with an averaging time of 12 h and the correlation coefficient increases to 0.44. An analysis of concentrations observed during narrowly defined meteorological conditions demonstrates the wide range of actual concentrations that is observed during conditions that can, given the models and parameterizations available, only result in one predicted concentration. The results demonstrate that atmospheric dispersion can only be adequately estimated for relatively long averaging periods when standard dispersion parameters that have been derived from averages of many experiments are used. The sources of uncertainties associated with short term atmospheric modelling required for emergency response are discussed and illustrated by measurements made at Chalk River. It is concluded that dispersivity is not uniquely associated with weather class. There are very good reasons for believing that vertical dispersion is correlated with stability and it seems likely therefore that the weakness in the model arises from the assumption that horizontal dispersion is also a simple function of stability.

Toxic Air Pollution across a State Line: Implications for the Siting of Resource Recovery Facilities

Massive volumes of solid waste are produced in the United States. Options for disposal are limited. Incineration and recycling are frequently proposed solutions. However, incinerators and waste recovery facilities, such as scrap smelters, generate hazardous air pollutants and toxic ash. Their potential hazards to health have not been adequately assessed. To illustrate the policy issues surrounding waste incineration and resource recycling, we examine the case of U.S. Metals, a scrap metals recovery plant in Carteret, New Jersey. This plant emitted 20 kilograms of dioxin in its 25 years of operation. It also released 86 tons of lead annually; nearby air lead levels were repeatedly in violation of standards. Construction of a tall stack caused export of toxic emissions from the plant to Staten Island, New York; high concentrations of lead were documented in surface soil on Staten Island. Because neither the State of New Jersey nor the U.S. Environmental Protection Agency were willing to regulate emissions from the plant, New York, the downwind state, was forced to sue U.S. Metals in federal court. The suit resulted ultimately in closing the plant. The case illustrates the difficulties in regulating pollution across state lines, a difficulty compounded by the abdication of responsibility by state and federal agencies. Further, the episode appears paradigmatic of a disturbing trend by state and local governments to locate waste combustion facilities at sites which will resolve problems of solid waste by encouraging export of airborne pollutants across regulatory boundaries.

Rain scavenging from tall stack plumes: The non‐proportionality problem

Abstract The purpose of this paper is to discuss some current problems in acidic precipitation related to transport and modelling and, more specifically, to source‐receptor relationships and data availability and interpretation problems. To this effect, experimental data related to rain scavenging from tall stack plumes will be re‐evaluated in the light of the non‐proportionality issue.

Prediction of Wind Speed, Direction and Diffusivity under Neutral Conditions for Tall Stacks

Abstract A one dimensional model of the neutral planetary boundary layer is used to predict the wind velocity and coefficient of eddy diffusivity throughout the 2-km planetary boundary layer. Comparison with routine radiosonde observations show that at 500 m, the model predictions of wind speed are within 1.2σ of the observed values where σ is the probable error of the observed values. An interesting correlation between the height of maximum diffusion and length scale (u*/f) of the neutral boundary layer has emerged out of this study. The velocity and diffusivity profiles from the PBL model are then used in the solution of a three-dimensional advection diffusion equation for the dispersal of nonreactive pollutants in the atmosphere. The results indicate that it is possible to select stack heights to ensure maximum dilution of a pollutant immediately on release and thereby minimize its long-range transport.

Comments on “Lateral Dispersion from Tall Stacks”

Abstract A few minor errors in a paper by Hanna are noted and several questions are raised about apparent inconsistencies. One question is why substantial enhancement of σy, by buoyancy was noted for the Bull Run data but was unmentioned for the Kincaid data; information given in the paper suggests similar ranges of X*/F* at both plants, but much smaller F* values at Kincaid, which may account for the lack of noticeable buoyancy effects there. The inconsistency between the recommended equation σy/x = 0.6 w*/u and the σy/x values recommended for various stability classes (based on u/w* ranges) can be removed by multiplying this σy expression by a factor which accounts for the effect of mechanical turbulence. Finally, it is noted that an identical equation was recently reported to give a good fit to σy from passive sources released above 0.3 h, albeit to much smaller distances than reported by Hanna.

Convective scaling applied to diffusion of buoyant plumes from tall stacks

During light wind convective conditions, strongly buoyant plumes from tall stacks often rise up near the top, h, of the mixed layer. Diffusion to the ground occurs at a rate proportional to the convective scaling velocity, w ∗ . When concentrations, distances, and buoyancy fluxes are scaled using h, w ∗ , the wind speed u and the emission rate Q, some simple dimensionless relations governing diffusion in the convective boundary layer can be derived. These dimensionless scaling relations are developed using aerometric and meteorological data from the Kincaid and Bull Run Power Plant tracer experiments conducted by the Electric Power Research Institute. In a test with independent data, maximum predicted and observed concentrations agree within 15% at both sites.

Verification of the pollutant transport model ?MODIS? using EPRI plains site data from a tall stack

Verification of the pollutant transport model ?MODIS? using EPRI plains site data from a tall stack

Meteorological and chemical controls on the vertical distribution of Beijing summer coarse and fine aerosols

Vertical profiles of fine and coarse aerosol particles were determined by cascade impactors at the me-teorological tower in Beijing for three days and one night, July 18–23, 1980. Coarse mode aerosols showed a maximum concentration at 47 m when there was an inversion at about 140 m height, and a rather uniform distribution when there was no inversion. This may indicate a two-component origin of coarse particles at the tower site, one being surface dust and the other being tall stack emissions. Fine mode aerosols showed more complex vertical profiles. Median particle size distributions of most metals were bimodal, indicating distinct coarse particle dispersion and fine accumulation mode processes. A chemical thermodynamic calculation indicates that fine mode Si can result from the reduction of silica to volatile SiO during coal combustion with limited air supply, a process which should release substantial amounts of carbon monoxide to the atmosphere.

Lateral Dispersion from Tall Stacks

Abstract Hourly ground-level concentrations of SF6 at downwind distances ranging from 0.5 to 50 km were observed by the Electric Power Research Institute (EPRI) on dense monitoring networks around power plants at Kincaid, Illinois, and Bull Run, Tennessee. Sigma y on given sampling arcs was estimated by a robust procedure. Over 160 h of data are available from monitoring arcs located at about five downwind distances, which show that σy is close to linear with downwind distance, x. During unstable conditions, σyu/w*x=0.6. When all the data are plotted together, the following empirical equation is valid:

Tree-ring variation in western larch (Larixoccidentalis) exposed to sulfur dioxide emissions

A tree-ring analysis was conducted to determine the relationship of sulfur emissions from the lead–zinc smelter at Trail, B.C., to radial growth in western larch (Larixoccidentalis Nutt.). Tree cores were collected from five stands known to have been polluted and from three control stands. Age effects were removed from cross–dated ring-width series by fitting theoretical growth curves and, subsequently, tree-ring chronologies were developed for each stand. We assumed that macroclimatic variation was estimated by the average of the control chronologies and two lagged values thereof. These control variables along with annual estimates of sulfur emissions were used in regression models to predict variation in the tree-ring chronologies from each of the polluted stands. Separate analyses were performed for years before and after installation of two tall stacks, for drought and nondrought years, and for years prior to initiation of smelting. In each case following the initiation of smelting, the variation explained by sulfur decreased with distance from the smelter and, concomitantly, the variation explained by the control variables increased with distance. Furthermore, chronology statistics suggested an increase in synchronous high-frequency variation in chronologies from polluted sites that persisted beyond implementation of pollution controls, which reduced emissions 10-fold.

The Effect of Tall Stacks on the Long Range Transport of Air Pollutants

Tall stacks are an effective means of reducing ground level concentrations near to sources, though they do not reduce the total burden of pollution in the atmosphere. In recent discussions of the acid rain question it has often been assumed that the use of tall stacks has had an adverse effect by allowing material to spread more widely in the atmosphere. The purpose of this study is to examine the effect of height of SO/sub 2/ emission releases on total sulfur deposition using a simple calculation.

Summary report of the corech (COGAR) workshop on the evaluation of air pollution episodes and associated control measures

Discussions within COGAR during 1981 indicated that collective information on the types of meteorological conditions when large, single sources like power stations contributed to pollution episodes, the frequency with which they occurred and the implications for intermittent control procedures, was important to all member utilities. This paper summarizes the findings of a working group set up by COGAR to study these problems. The investigation was concerned with SO 2 episodes and how feasible it would be to reduce their intensity by such measures as a substitution of low sulphur fuel or switching generation to areas where the probability of an episode developing is less. There has been a considerable reduction in SO 2 emissions in most urban areas in the last two decades. Nevertheless, in many locations, 24-h air pollution episodes can still be attributed to small or medium-sized emissions from low or medium level stacks, rather than to power stations and other large industrial sources with tall stacks. The worst cases in flat terrain where power stations do contribute for many hours are either stagnant conditions persisting for 24 h or a steady wind blowing consistently from an area containing several power stations. Single stations can present problems when topography interferes with dispersion or the stack height is inadequate for the emissions. Data on the frequency with which episodes occur in a given location and the ability to forecast episode conditions in advance, so that if appropriate, preventative measures may be taken, are the desired objectives. Achievement of these objectives requires a detailed understanding of the role of each type of source in relation to different meteorological situations and the local topography. The end product of such studies should be either; 1. (a) the specification of a procedure for implementing intermittent emission control 2. (b) a demonstration that intermittent control is not an effective option in the area under study. In case (a), input data required are 1. (i) the vertical structure of the atmosphere 2. (ii) ground level concentrations of pollutant plus, in complicated topography 3. (iii) the three-dimensional distribution of pollutant. COGAR is a group set up to coordinate atmospheric research in the electrical supply industry in Europe.

Experimental studies of plume dispersion in convective conditions—II. Horizontal plume dispersion

Field measurements have been made of the horizontal dispersion of four different plumes from four different sites during convective conditions. The plumes were emitted from tall stacks and values of the dispersion coefficients were obtained from overhead photography and by traversing plume-sensitive instruments through the plume at right angles to the plume direction. Values of the single particle dispersion coefficients were obtained from a mosaic of photographs. These values for a low-buoyancy plume are shown to be consistent with the calculations of Lamb (1979, In Fourth Symposium on Turbulence, Diffusion and Air Pollution, pp. 27–33) and Weil (1979, Martin Marietta Corp., Baltimore, MD) and confirm the validity of Lamb's predictions. Values of the relative dispersion coefficients were also obtained from photographs and airborne traverses. These data were scaled by the buoyancy length scale, l B = F u 3 , and the resulting values of σ y l B are shown to be a function of the non-dimensional down-wind distance, x l B , for values of ( x l B) 2 3 < ∼100 . At ( x l B) > ∼100 the buoyancy scaling ceases to provide an adequate description of the diffusion process, indicating the growing effects of ambient atmospheric turbulence on the plume. The relative diffusion data non-dimensionalized by division by z i are shown to be a function of Deardorffs' (1974, Boundary-Layer Met. 7,81–106) dimensionless time X = xw ∗ uz i . This indicates that the turbulence present in the convective boundary layer is effective at scales small enough to be responsible for relative diffusion.