Air pollutant concentration and its location under different thermal stability classes

Summary ?The Gaussian plume model for the dispersion of pollutants released to the atmosphere from an elevated point source has been presented assuming perfect reflection at ground surface. An analytic treatment for both the maximum ground-level concentration and its downwind location for different stability categories have been obtained. The effective release height modification was taken into consideration. An illustrative case study namely, the emission from the research reactor at Inchas, has been studied. The results of both analytical treatments and semi-empirical formula are discussed and presented in illustrative diagrams. Received June 27, 2001; accepted April 30, 2002     

Algal community and pollution indicators for the assessment of water quality of Ismailia canal,Egypt

Stochastic Environmental Research and Risk Assessment - The phytoplankton community structure is affected by both ecological and spatial factors. Influences of these two factors on phytoplankton...     

Mathematical model for hermitized atmospheric dispersion in low winds with eddy diffusivities as linear functions of down wind distance

Summary In the present paper, an attempt is made for generalized the atmospheric diffusion operator. This can be accomplished by employing the realizability procedure, to identify a surface operator, that ensures self-adjointness’ of the atmospheric diffusion operator. The dispersion modeling in low wind speeds assumes importance because of the high frequency of occurrence and episodic nature of these poor diffusion conditions. A steady-state mathematical model for hermitized model has been calculated for the dispersion of air pollutants in low winds by taking into account the diffusion in the three coordinate directions and advection along the mean wind. The eddy diffusivities have been parameterized in terms of downwind distance for near source dispersion (Arya, 1995). The constants involved in this parameterization are the squares of intensities of turbulence. An analytical solution for resulting advection-diffusion equation with the physically relevant boundary conditions has been obtained. The solution has been used to simulate the field tracer data collected at IIT Delhi in low wind convective conditions.     

Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation

Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young’s modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young’s modulus of equivalent medium for wave propagation analysis.     

Quaternary coral reefs of the Red Sea coast, Egypt: diagenetic sequence, isotopes and trace metals contamination

This study focuses on the diagenetic sequence under marine and meteoric conditions as well as isotopes and trace metals contamination in Quseir and Gebel Zeit areas along the Egyptian Red Sea coast through a series of modern and fossil corals, Porites lutea and Favites pentagona. The diagenetic sequence begins with deposition of thin fringes of syntaxial aragonite and micritic high-magnesian calcite in the modern corals to completely altered Porites and partially altered Favites to low-magnesium calcite in the oldest Pleistocene unit. Average δ¹⁸O and δ¹³C values of Pleistocene corals in the two studied areas were lower than those of modern corals. Values of modern corals and lower fossil unit indicated coralline limestone, while those of middle and upper fossil units indicated fresh water influences. Average values of trace metals in modern corals were higher than those of Pleistocene counterpart except for Mn. Modern coral samples recorded enrichment in the average values of Pb, Zn, and Mn at Quseir area and enrichment in Co, Cu, and Ni at Gebel Zeit area. This may be attributed mostly to different tourist activities, landfill due to increase urbanization and nearby of Quseir area from the old phosphate harbor at El Hamrawin area, as well as oil exploration and production activities in the Gulf of Suez area. Also, results indicated that most samples of Porites have high concentration of trace metals than in Favites, especially in Cu, Zn, Mn, and Pb. This may due to high amounts of intergranular porosity and high total surface area of Porites in contrast to Favites.     

Quantitative Interpretation of Self-Potential Anomalies of Some Simple Geometric Bodies

We have developed a new numerical method to determine the shape (shape factor), depth, polarization angle, and electric dipole moment of a buried structure from residual self-potential (SP) anomalies. The method is based on defining the anomaly value at the origin and four characteristic points and their corresponding distances on the anomaly profile. The problem of shape determination from residual SP anomaly has been transformed into the problem of finding a solution to a nonlinear equation of the form q = f (q). Knowing the shape, the depth, polarization angle and the electric dipole moment are determined individually using three linear equations. Formulas have been derived for spheres and cylinders. By using all possible combinations of the four characteristic points and their corresponding distances, a procedure is developed for automated determination of the best-fit-model parameters of the buried structure from SP anomalies. The method was applied to synthetic data with 5% random errors and tested on a field example from Colorado. In both cases, the model parameters obtained by the present method, particularly the shape and depth of the buried structures are found in good agreement with the actual ones. The present method has the capability of avoiding highly noisy data points and enforcing the incorporation of points of the least random errors to enhance the interpretation results.     

A New Algorithm for Depth Determination from Total Magnetic Anomalies due to Spheres

We have developed an automatic method to determine the depth of a buried sphere from numerical second horizontal derivative anomalies obtained from total field magnetic data. The method is based on using a relationship between the depth and a combination of observations at symmetric points with respect to the coordinate of the projection of the center of the source in the plane of the measurement points with a free parameter (graticule spacing). The problem of depth determination has been transformed into the problem of finding a solution of a nonlinear equation of f(z) = 0. Procedures are also formulated to determine the magnetic moment and the effective angle of magnetization. The method is applied to synthetic examples with and without random errors and tested on a field example from Senegal. In all cases, the depth solutions are in good agreement with the actual ones.     

Fragmentation Energy in Rock Blasting

The theoretical explosive energy used in blasting is a common issue in many recent research works (Spathis 1999; Sanchidrian 2003). It is currently admitted that the theoretical available energy of the explosives is split into several parts during a blast: seismic, kinetic, backbreaks, heave, heat and fragmentation energies. Concerning this last one, the energy devoted to the breakage and to the creation of blocks within the muckpile can be separated from the microcracking energy which is devoted to developing new and/or extending existing micro cracks within the blocks (Hamdi et al. 2001; López et al. 2002). In order to investigate these two types of energy, a first and important task is to precisely study the main parameters characterising the two constitutive elements of the rock mass (rock matrix and discontinuity system). This should provide useful guidelines for the choice of the blasting parameters (type of explosive, blasting pattern, etc.), in order to finally control the comminution process. Within the frame of the EU LESS FINES research project, devoted to the control of fines production, the methodology was developed in order to: (1) characterize the in situ rock mass, by evaluating the density, anisotropy, interconnectivity and fractal dimension of the discontinuity system and (2) evaluate fragmentation (both micro and macro) energy spent during the blasting operation. The methodology was applied to three production blasts performed in the Klinthagen quarry (Sweden) allowing to estimate the part of the fragmentation energy devoted to the formation of muck pile blocks on one side and to the muckpile blocks microcracking on the other side.     

A simple formula for shape and depth determination from residual gravity anomalies

This paper presents a simple method for shape and depth determination of a buried structure from residual gravity anomalies along profile. The method utilizes the anomaly values of the origin and characteristic points of the profile to construct a relationship between the shape factor and depth of the causative source. For fixed points, the depth is determined for each shape factor. The computed depths are then plotted against the shape factor representing a continuous monotonically increasing curve. The solution for the shape and depth of the buried structure is then read at the common intersection point of the depth curves. This method is applied to synthetic data with and without random errors. Finally, the validity of the method is tested on two field examples from the USA.