[en] A pollutant of small particles is emitted by a point source at a height h above ground level in an atmosphere in which a uni-directional wind speed, U, is prevailing. The pollutant is subjected to diffusion in all directions in the presence of advection and settling due to gravity. The equation governing the concentration of the pollutant is studied with the wind speed and the different components of diffusion tensor are proportional to the distance above ground level and the source has a uniform strength. Adopting a Cartesian system of coordinates in which the x-axis lies along the direction of the wind velocity, the z-axis is vertically upwards and the y-axis completes the right-hand triad, the solution for the concentration c(x,y,z) is obtained in closed form. The relative importance of the components of diffusion along the three axes is discussed. It is found that for any plane y=constant (=A), c(x,y,z) is concentrated along a curve of ''extensive pollution''. In the plane A=0, the concentration decreases along the line of extensive pollution as we move away from the source. However, for planes A≅0, the line of extensive pollution possesses a point of accumulation, which lies at a nonzero value of x. As we move away from the plane A=0, the point of accumulation moves laterally away from the plane x=0 and towards the plane z=0. The presence of the point of accumulation is entirely due to the presence of lateral diffusion. (author)

[en] A fixed volume of pollutant of small particles is emitted by a point source at a height h above ground level, at a certain instant of time, in an infinite medium in which wind is blowing horizontally with a uniform speed, U. The pollutant is subject to diffusion in the presence of advection and settling due to gravity. The solution for the concentration is obtained in closed form for subsequent times. It is shown that as time increases the point volume spreads out under the influence of diffusion but the volume of dust always maintains a point of accumulation, where the concentration is a maximum. In the absence of horizontal diffusion, the dust moves as a vertical front with uniform speed U. In both cases the accumulation point moves horizontally with the flow speed but its height is a complicated function of diffusion (both horizontal and vertical) and gravity. The solution is illustrated graphically. (author)

[en] The factor analysis is a modern method of statistical analysis of the experimental data. This method applies in a broad range of sciences like psychology, economy, medicine, electronics, physics and other. This method allows one to extract from a set of experimental data some properties of the studied process (usually called 'hidden') when there is not any theoretical description of studied phenomena. In this study we have done a short presentation of factor analysis followed by some applications as the problem of the boxes (the classical one) and the problem of the polynoms. We apply the factor analysis to an ecological problem using a very simple model of the source of pollution (the gaussian one) by simulating the computer data

[en] In this paper there are presented the main characteristics of the 'new generation' dispersion model which can be used in a real time surveillance system of the pollution level around a major pollution source. There are presented also, the results concerning SO₂ concentration obtained with the described model in the area of power plant sites: Bucharest-South, Craiova-2 and Drobeta Turnu-Severin power plants. Daily mean concentration for June 1993 have been calculated and there are presented plots for the maximum values obtained for all three power plants recorded during this month. Using the predicted concentration values obtained with the dispersion model, decisions can be taken for decreasing the pollutant emission in case that the air quality standards are exceeded in the analyzed area. (authors). 4 figs., 1 tab., 4 refs

[en] The pollutant emission of the thermal power stations may have an important contribution to the local pollution as well as to regional (transfrontier) and global pollution. Due to the impossibility at present of making continuous monitoring of the emission of pollutants it is necessary to use computational models for obtaining inventories of the pollutant sources and for studying their dispersion into atmosphere. The computational code used to simulate the pollutant diffusion in the atmosphere is a climatologic model giving the annual average concentration and the evaluation of the maximum SO₂ concentration. The paper presents the analyses for the case of 14 thermal power stations of Romania

[en] Full text: Chlorinated solvent source zones and plumes in fractured sedimentary rock have been investigated intensely at several industrial sites in Canada and USA using numerous high resolution field and laboratory methods within a field-based research program. The contamination at these sites was initiated by DNAPL releases decades ago and the plumes emanating from these subsurface sources serve as long-term tracer experiments providing valuable insights regarding flow and transport in sedimentary rock. The sites show many features common to all and this provides the basis for a General Conceptual Model (GCM) for such plumes in sedimentary rocks (Parker et al., 2012). The processes influencing these plumes were determined by application of the DFN approach, a suite of several field and laboratory methods for high resolution measurements on core and in open and sealed boreholes to quantify various physical, chemical and microbial properties and their interactions within the heterogeneous fractured and porous rock system. Several types of sedimentary rock have been studied and include: dolostones, a sandstone and sandstone with shale interbeds, shales and siltstone. The major features in common include: the longitudinal distance between the source zone, where the DNAPL initially caused the plume to form, and the plume front is small relative to the distance travelled by groundwater over the same time (i.e. strong plume front retardation); even though there is strong retardation, the plume occupies a substantial volume of the rock because of strong dispersion in the directions transverse to the dominant groundwater flow direction; the plumes have evolved over decades to achieve a stationary position or nearly so (quasi-steady state); nearly all contaminant mass now resides, due to matrix diffusion and sorption, in the low-permeability blocks of rock between the fractures, the latter being where active groundwater flow and dissolved-phase contaminant transport occurs; the internal characteristics of the concentration distributions are more orderly than chaotic; the peak concentrations in the plumes are generally much below DNAPL solubility values due to the combined effects of matrix diffusion, transverse dispersion and in some but not all cases due to degradation; DNAPL persists when exceptionally large releases allowed high non-wetting phase saturations of low-solubility compounds, especially mixed organic NAPL source zones, but otherwise, source zones have little to no remaining DNAPL phase and are indistinguishable from plumes. Hence, these sites are now referred to as having plumes without persistence of DNAPL source zones. This is important in the remediation context because DNAPL remediation is not the remediation issue. Overall, each of the plumes is smaller, more orderly and less impacting on groundwater resources and the environment than was initially expected based on early visions of the nature of fractured rock systems. The common characteristics of the plumes indicated above are a result of the key features of the fracture networks common to all of the sites. These features are: orderly networks consisting of bedding parallel fractures and nearly orthogonal joint sets creating 3-D fracture networks. The fracture density is large so that fracture connectivity is strong. Therefore, for purposes of bulk groundwater flow estimation, the groundwater flow systems can be assessed using an equivalent porous medium approach. However for contaminant transport, DFN concepts and models must be used that represent flow in the numerous fractures that provide surface area for matrix diffusion effects. Another feature common to all of the sites is the substantial effective rock matrix porosity in the range of 2-20%, which provides large capacity for contaminant mass storage as dissolved phase that is enhanced by sorption to solid phase organic carbon common to sedimentary rock systems. Ultimately, however, the characteristic that strongly limits the groundwater flux and hence contributes most strongly to contaminant plume front retardation is the number and distribution of hydraulically-active fractures and their effective (hydraulic) apertures that are generally moderate to small (50-500 microns). Fracture length is most-difficult to assess in the subsurface however, it is deduced by the hydraulic connectivity enhanced by the number of fractures observed in these systems. The plumes as tracers over 50 years or more suggest that larger fractures are distributed in such a way that they have limited influence at the plume scale because they likely connect to smaller fractures preventing long distance transport in larger aperture fractures. It is also apparent from these field studies and simulations using DFN models that 3-D fracture networks with nearly orthogonal geometries observed for sedimentary rocks cause strong transverse dispersion in the direction of flow, increasing the down-gradient width of these plumes compared to the source zone width and enhancing detection of the plumes within a well-connected fracture network but also contributing to plume front retardation (Parker et al., 2012; Chapman et al., 2013). In the early stage of the contamination, diffusion from the fractures into the rock matrix (forward diffusion) occurs nearly everywhere in the source zones and plumes, however now, after decades of advection along many fractures and diffusion into the rock matrix there is a redistribution of mass throughout the entire source and plume causing an evolution in site conditions. Beginning on the up-gradient end, there is diffusion out of the rock matrix into the fractures being actively flushed by clean groundwater (back diffusion) in much or most of the former source zone. This back diffusion contributes mass fluxes out of the up-gradient source zone and sustains the plume concentrations down-gradient, while the contaminant mass in the former source zone gradually diminishes due to down-gradient transport. The fact that the contaminant mass is nearly all in the rock matrix everywhere throughout the entire contaminated volume where groundwater flow is small or negligible and the total contaminant mass discharge from the former source zone to the plume is relatively small, DFN model simulations for transport show that complete removal of the mass from the former source zone has only minimal influence of the plume over long time into the future (Parker et al., 2010). After a few to several decades these evolved source conditions create a nearly stationary plume position (plume front positions are not migrating down-gradient) due to strong matrix diffusion effects throughout. Declining concentrations are observed in the source zones and the plumes even without substantial mass loss due to degradation, however, after a few decades of monitoring at these sites, abiotic and biological degradation products are increasingly evident and we show that even slow degradation rates suggest that Monitored Natural Attenuation (MNA) is a reasonable option for site remediation in fractured sedimentary rock. After a few or more decades, these nearly stationary or shrinking contaminated volumes can be effectively managed within water supply capture zones with adequate aquifer characterization and confirmatory monitoring. The field-based research program has quantified the time and distance scales for the evolution of source zone and plume conditions through distinct stages at several sites in sedimentary rock. The range of field site conditions shows common conditions that inform a general conceptual model (GCM) for point source zone and plume behavior in sedimentary rocks, providing an intuitive framework or guide. The characteristics and processes that control the source zone and plumes in fractured porous rock (sedimentary rock) are much different than those influencing DNAPL source zones and plumes in granular porous media. The current concepts for plumes found in textbooks and embedded in the regulatory frameworks for site remediation and decision-making are founded only on granular media concepts, not fractured rock. This has created much difficulty with decision-making for sites on bedrock, which are different in nearly all respects. (author)

No abstract available

[en] The paper discusses results from a July 1991 workshop and the progress that has been made in advancing the technology of surface-coating-free materials (SCFMs). The workshop identified opportunities for the development of SCFMs being used by industries and recommended ways for increasing the use of SCFMs by other industries. In addition, the workshop offered the opportunity for the exchange and the development of innovative concepts related to SCFMs. Coating operations release about 15% of stationary area source volatile organic compound (VOC) emissions. Many of these sources cannot be impacted by add-on controls at a reasonable cost due to their small size and/or the difficulty of capturing emissions. In addition, not only do emissions occur during initial coating, they occur each time the surface is recoated. If materials or products could be developed which do not need coating during either manufacture or use (SCFMs), VOC emissions could be reduced significantly. The U.S. ambient air quality standard for ozone (0.12 ppm) is exceeded in over 100 areas in the country. Extensive reduction of VOC emissions is required for attainment. The difficulty of dealing with stationary area sources has been a major obstacle to attaining these reductions. Area sources may contribute as much as 50% of U.S. VOC emissions

[en] Dispersion modelling is a necessary tool for both qualitative and quantitative estimates of air pollution. There exists a number of models for prediction of the ground-surface air pollutant concentrations resulting from various sources. These models are to be used in a wide variety of applications, such as the installation of new energy-development facilities and other sources of air pollution, regulatory decision making, and environmental planning. In this paper, major types of air pollution models are described along with their applications, advantages, and disadvantages. (author). 19 refs., 2 figs

[en] Almost the entire Norwegian population has cell phone. The usefulness of the cell phone is great, but can use a mobile phone to health or discomfort? How can exposure be reduced? NRPA follows research and provides advice on mobile phone use. (AG)