Leachate chemistry

PHREEQC version 2.15 was used to calculate equilibrium concentrations of ion pairs from the leachate chemistry. PHREEQCi was initially developed by the United States Geological Survey and a substantial library of thermodynamic constants has built up over the ongoing development period (Appelo Postma 2005). 

Fruchter, J. S., Rai, D., Zachara, J. M. Schmidt, R. L. 1988. Leachate Chemistry at the Montour Fly Ash Test Cell, EPRT-EA-5922. Electric Power Research Institute, Palo Alto, CA. 

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. 

Mclsaac R, Rowe RK. Change in leachate chemistry and porosity as leachate permeates through tire shreds and gravel. Can Geotech J 2005 42 1173-88. 

Median leachate water chemistry during periods of sulfide oxidation was calculated for each parameter analyzed, by humidity cell. These data, for parameters that show distinct variation between cells, are presented as Table 1. HC2-SQFP, which contains more pyrite and very low carbonate content, rapidly generates acidic leachate causing its leachate to be higher in all parameters except Mo. 

Kassim TA, Simoneit BRT, Williamson KJ (2005) Forensic investigation of leachates from recycled solid wastes An environmental analysis approach. In Kassim TA, Williamson KJ (eds) Environmental Impact Assessment of Recycled Wastes on Surface and Ground Waters Volume 3 Concepts, Methodology and Chemical Analysis. Handbook of Environmental Chemistry, Water Pollution Series, Vol 5/Part F. Springer, Berlin Heidelberg New York 321-400... 

Edmonds M., Oppenheimer C., Pyle D. M., and Herd R. A. (2003a) Rainwater and ash leachate analysis as a proxy for plume chemistry at Soufriere Hills Volcano, Montserrat. In Volcanic Degassing, Geological Society of London Special Publication 213. (eds. C. Oppenheimer, D. M. Pyle, and J. Barclay). Geological Society of London, pp. 203-218. 

Hinkley T. K. (ed.) (1987) Chemistry of ash and leachates from the May 18, 1980 eruption of Mount St. Helens, Washington. US Geological Survey Professional Paper 1397, 64pp. 

Unnatural Products Chemistry. The complete identification of unknown compounds that we have successfully resolved using PB/LC/MS will clearly require additional analytical information, such as provided via liquid chromatography ICP/MS (detecting nonmetals such as chlorine and sulfur), FT-IR, UV or proton and heteroatom NMR. This situation is analogous to that of a natural products chemist faced with making a complete structural assignment of an unknown compound isolated from some matrix such as seaweed instead of a leachate from a hazardous waste site. The natural products chemist would exploit the complete array of analytical instrumentation and not attempt identification based solely upon low resolution (quadrupole) mass spectrometry. 

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. 

In this paper the chemistry of Paraho retorted shale, the nature of the thermo-chemical reactions that can contribute to its cement-like properties, and the chemistry of the leachates obtained from permeability studies will be presented. Although civil engineering information now exists which permits the disposal of retorted shale in an environmentally acceptable manner, a better understanding of the thermal reactions of retorting and the chemical composition of retorted shale may suggest changes in retorting operations which would further lessen any possibly adverse environmental impact. 

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