Issue 1 [March]

A main problem related to coal ash disposal is the heavy metal content of the residue. In this regard,
experimental results of numerous studies have indicated that toxic trace metals may leach when fly ash
and bottom ash contacts with water.
In this study, fly ash and bottom ash samples obtained from Kemerköy thermal power plant, located on
the south-western coast of Turkey, were subjected to toxicity tests such as the extraction procedures
(EP) and toxicity characteristic leaching procedures (TCLP) of the U.S. Environmental Protection
Agency (U.S. EPA), the so-called Method A extraction procedure of the American Society of Testing
and Material (ASTM). When Pb and Cd concentrations, analysed according to EP and TCLP, were
considered, Kemerköy fly and bottom ash can be classified as a hazardous waste under the principles
of the Federal Resource Conservation and Recovery Act (RCRA).
Based on the geochemical analyses carried out, it was also determined that several toxic trace elements,
such as Pb, Zn, Cd, Cu and Co were enriched at the fly and bottom ash of Kemerköy thermal power plant.

The development of a conceptual site model (CSM) is an invaluable tool used for assessing and planning
remedial actions at a contaminated site. The CSM incorporates site-specific, hydrogeologic and
geochemical information to identify contaminants of concern, sources of pollution, environmental
pathways and retardation mechanisms, and points of exposure. The model is dynamic and continually
revised as new information is obtained during the course of investigation. A ground water contamination
case study is examined to illustrate the development and application of a CSM. The site is a metal
plating facility that has contaminated the ground water with chromium. The CSM was incorporated
into a 3-D fate and transport model. The Heavy Metal model, HM-3D, was used to simulate the fate
and transport of chromium at the site and evaluate pump-and-treat remediation scenarios.

The problem of the passive contaminant spreading in a steady viscous fluid stream is discussed while the
admixture's dissipation and diffusion are taken into account. The channel is assumed to be a horizontal
plane, curvilinear and quite lengthy, so that the ratio of the stream width to its length can be regarded as
a small parameter. A mathematical model of the process derived by the small parameter technique from
the 2D steady Navier-Stokes equations for incompressible viscous fluid and non-steady convection-diffusion
equation of a substance in the moving medium is introduced. A finite element method is applied for
numerical study of the proposed model and results of computer experiments are presented.

Field experiments have been conducted to investigate flow and dispersion through obstacle arrays.
Model obstacles which represent real structures at a nominal scale between 1/10 and 1/20 were used.
The main purpose of the experiments was to examine flow and dispersion of contaminants in the vicinity
of individual obstacles embedded in an array of cubes. Two array configurations were used, namely
the in-line and staggered array configurations. The field experiments were supported by flow visualisation
trials performed in the wind tunnel. In the light of the results of these wind tunnel trials, the field
experiments were carried out using an array spacing S/H = 1.5 (where S is the space between two consecutive
array elements). Dispersion around an isolated model building has already been investigated
in the field (Mavroidis and Griffiths, 1996). Thus comparison is allowed between dispersion around an
isolated obstacle and around the same obstacle embedded in an array of cubes.