Leachate composition, initial

Owing to the volatility of Mn, Pb, Zn and Cu, it is assumed that these elements are released in the gaseous state during combustion and condense onto the fly ash spheres as cooling occurs (Davison et al., 1974 Kaakinen et al., 1975 Linton et al., 1976 Smith et al., 1979). Therefore, these elements make initial contact with the leaching solution. The chemical complexing of these elements and the method of adsorption and attenuation are important factors to consider when estimating leachate composition from ash composition. From the data, it is concluded that Fe is located primarily in the ash... 

Because of the possible wide differences among properties and characteristics of solid phases and the varied chemical compositions of contaminants or a contaminant leachate, field measurement variables present average properties over a large volume/area. The problem which complicates the picture is that ideal models are applied to a material or space which is highly non-ideal, non-uniform, and does not permit easy specification or identification of both initial and boundary conditions. To avoid this discrepancy, field and laboratory methods should be developed or modified to complement one another. Thus, ideal theory needs to be supported with physical evidence if rational applications to field studies and environmental simulation are desired. 

It can be seen from Table II that the fly ashes produced in the A boiler essentially form acidic leachates even though the major element composition of these fly ashes were comparable to the amounts found in the boiler C and boiler D fly ashes (see Table III). The Militant, Deep Hollow, Upshur and Badger fly ashes produced in this boiler encountered flame and boiler temperatures that are below even the initial deformation temperatures of the fly ash. Hence, the fusion reactions probably did not occur that might have led to formation of products that generate an alkaline leachate. 

The composition of pore waters from contaminated cores 1 and 2 were used to initialize the model (Table 2). Concentrations represent leachate collected from the initial half pore volume of each core. Eluent specified in the transport simulations had the composition of uncontaminated ground water in Table 2. Reactions proposed to describe concentration changes for selected constituents within the cores are based on comparisons between eluent and leachate chemistry and analysis of selected constituents in the core samples. Equilibrium constants and kinetic rates for the reactions were adjusted to give the best fit to leachate concentrations from core 1. The same reactions, equilibrium constants, and kinetic rates were then tested by modeling the concentrations of constituents in leachate from core 2. This geochemical model will be used in the future to simulate evolution of contaminated ground water associated with the Area 4 landfill at the aquifer scale. 

The spectrum of Munich leachate is more concave with no marked accident, and its absorbance decreases rapidly between 200 and 230 nm, due to a more important salinity, especially chloride ion. This spectrum also gives an indication of the composition of the leachate. Indeed, simple organic molecules that result from the initial degradation process absorb at the beginning of the UV wavelength range, and few humic-like substances are present (low shoulder at 270 nm). 

The interaction of leachate and sandstone was studied in a series of batch experiments in which crushed samples of Uinta Sandstone were reacted with the leachate for five days. The contact time was determined in previous screening experiments which showed that major chemical constituents in the leachate had attained a steady-state composition during this period. During the experiments, the initial and final compositions of the leachate were determined. Characterization of the Uinta Sandstone and the L2 leachate and details of the analytical methods used in these studies have been described elsewhere (1 ). 

In Figure 6, column (1) represents the initial chemical composition of the leachate observed prior to contact with the sandstone. Column (5) summarizes the solution composition observed after reaction with the sandstone for five days. Columns (2)-(4) represent intervening steps in the reaction-path simulation. The major changes in chemistry observed between columns (1) and (5) are an increase of three orders of magnitude in the concentration of Mg and significant decreases in total dissolved carbonate, fluoride, and silica. 

Analysis of the leachate during the toxicological and chemical screening process provides the chemical composition and toxicity data needed for initial evaluation of the test material. This evaluation aids in the scheduling of experiments for each test material. 

The residual terms associated with each system of equations represent the difference between the linear programming estimate and the actual concentration of each organic contaminant in the sample. The optimum solution for each system of equations is that for which the residual terms are minimized. Since a perfect modeling solution would accoimt for 100% of the measured concentration for each organic contaminant, the validity of the present environmental forensic MM model can be evaluated by calculating a mean residual percent of each contaminant (the mean residual for each contaminant divided by the mean contaminant concentration) [Ij. Therefore, the use of linear programming technique partitioning helps correct the initial end-member compositions of SWMs and/or their leachates, and their abundances, to better fit the observed multivariate data set, as well as to specify and select the compositions of the end-members. 

An initial solute concentration must be selected for the application of solute transport models. An initial concentration for each solvent was based on the chemical composition of leachates from hazardous-waste sites. Where available, the largest reported concentration was used in the modeling efforts (Table 17.2.1). No published data were located for some of the solvents such as cyclohexanone. In such cases, the initial concentration was arbitrarily assigned as 1,000 mg/L or it was equated to the compound s solubility in water. Hexane, decane, and tetrahydofuran were not included in fliese studies. 

Electrochemical oxidation of landfill leachates is significantly dependant on two process variables (i) the applied current density and (ii) the composition of the aqueous waste. Figure 1 shows the effect of the initial concentrations of COD and ammonia on the oxidation kinetics of both compounds, using BDD anodes. The raw leachate and a second sample obtained by dilution are compared. NaCl was added to the diluted batch, to... 

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