Physical conditions, ground water

The concern is that the combustion process mobilizes the major/minor and trace element concentrations of combustion product and that fresh water (streams, lakes) as well as ground-water may become contaminated by leachate. In general, sites for ash disposal are physically close to the combustion site. Thus, the location is chosen primarily on the basis of economics, and the disposal sites exhibit a wide range of local hydrological regimes and are, of course, subject to prevailing climatic conditions. 

The physical and chemical characteristics of these ashes, combined with the operational parameters of the power plant and the disposal environments in which the ashes are placed, control the leaching susceptibility of these wastes and determine the potential for contamination to ground-water aquifers. Little information is known on the effect of coal ash leachates on groundwater quality (Theis, 1975 Theis et al., 1978, 1979). This paper discusses the concentrations of selected elements that can be expected to be released under ash disposal conditions, as simulated by laboratory experiments. 

Data from field and laboratory studies of creosote-contaminated ground water are being analyzed by the U S. Geological Survey to determine the transformation pathways of selected organic compounds, assess the relative importance of physical, chemical, biochemical, and microbial processes in the transformation of these compounds under ambient conditions, and study relevant biotransformation processes occurring in the subsurface ground water. 

The ground-water environment is quite variable in its physical conditions of ground-water distribution, occurrence and flow. What was considered a sterile environment, devoid of oxygen, is known to contain dissolved oxygen and considerable microbial biomass (1). Distributions of... 

Subsurface physical, chemical and biological conditions are quite variable in space and time. These factors can be the source of considerable "natural" variability in ground-water chemistry at both clean and contaminated sites. Sampling and analytical errors or variability can be controlled if these activities are planned and documented as protocols which take into account the unique characteristics of individual sampling points and conditions. It is critical that a sound hydrogeologic basis exists for the steps in the sampling protocol which precede actual sample collection. 

Maneb or Mancozeb. Few data on the transport and partitioning of these maneb and mancozeb were located. Calumpang et al. (1993) reported a half-life of 2.9 days for mancozeb determined in a silty clay loam soil placed in experimental columns and maintained under field conditions. In other studies, the half-life for maneb in soil was estimated to be 3 weeks and 4-8 weeks (Nash and Beall 1980 Rhodes 1977). Using chemical and physical properties. Beach et al. (1995) estimated that the half-life in soils for maneb and mancozeb to 70 days. The high value estimated for these compounds (>2000) suggested to these authors that the potential for leaching into ground water would be low. However, the potential for solubility in surface water was considered to be moderate, despite the relatively low solubility of maneb and reportedly insolubility of mancozeb. 

Affected by the forces of inter-atomic and inter-molecular interactions, almost all atoms in ground water turn out to be to some extent associated. Numerous weak intermolecular bonds, not taken into account at chemical analysis, whose effect grows with increase in pressure, salinity and with the decrease in temperature and rate of flow, have special significance. All these bonds obstruct translation mobility of individual atoms and thereby facilitate the formation of some structure of the solution, which determines its physical and chemical properties in reservoir conditions. Aqueous solution structure is some relatively stable in space and time optimum orderliness of inter-atomic and inter-molecular bonds in the specifically set conditions. This structme depends on temperature, pressure and composition of water in the reservoir conditions. 

CWorine is an elemental chemical lliat exists as a gas at ambient conditions but liquefies at moderate pressures. Some of its common physical properties are listed in Table 8.1.1. Chlorine is sliglitly water soluble, is yellow-green in the gaseous state, and Itas a strong cliaracteristic odor. Because chlorine gas is about 2.5 times denser tlian air, it tends to stay close to the ground when released into tlie atmosphere. Liquid chlorine Itas a clear amber color one volume of liquid can vaporize to about 460 volumes of gas. In addition, liquid cltlorine has a large coefficient of thermal expansion. 

The capillary pressures are determined by the hydrocarbon-water interfacial tension, y, and the diameters of the interconnected pore throats of the carrier rock. The interfacial tension between oil and water increases a little with depth it varies between 25 x 10 Nm and 35 x 10" Nm (Berg, 1975). The gas-water interfacial tension decreases with depth from 75 x 10 Nm" at ground surface conditions to 35 x lO Nm at depths of > 2 km (Berg, 1975). At depths of more than 2 km, the gas-water interfacial tension is similar to the oil-water interfacial tension (Berg, 1975 England et al., 1987). The size of the pore throats is determined by the physical properties of the carrier rock. 

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