Groundwater water chemistry

Dissolution and precipitation can occur as contaminants travel from the land surface to groundwater aquifers. These processes can affect water chemistry, and they can significantly modify the physical and chemical properties of porous media (Lasaga 1984 Palmer 1996 Dijk and Berkowitz 1998, 2000 Darmody et al. 2000). Under some conditions, large quantities of mass can be transferred between the liquid and solid mineral phases. 

The measurement of pH is one of the most important measurements in water chemistry. The value of pH defines the types and the rates of chemical reactions in water, and the fate and bio availability of the living organisms. Together with temperature measurements, pH values serve as groundwater well stabilization indicators. 

Gobler, C. J., and Bonedlo, G. E. (2003). Impacts of anthropogenicaUy influenced groundwater seepage on water chemistry and phytoplankton dynamics within a coastal marine system. Mar. Ecol. Prog. Set. 255, 101-114. 

Groundwater or soil pore-water chemistry generally differs from the chemistry of laboratory solutions due to both inorganic and organic solutes which can act as catalysts or inhibitors to dissolution (e.g., Ganor and Lasaga, 1998). For example, much effort has been expended to... 

Over the last several decades, the decline in alkalinity in many streams in Europe and in northeastern USA as a result of acid deposition has been a subject of much concern (Likens et al., 1979). The concentration of bicarbonate, the major anion buffering the water chemistry of surface waters and the main component of dissolved inorganic carbon (DIC) in most stream waters, is a measure of the reactivity of the watersheds and reflects the neutralization of carbonic and other acids by reactions with silicate and carbonate minerals encountered by the acidic waters during their residence in watersheds (Garrels and Mackenzie, 1971). Under favorable conditions, carbon isotopes of DIC can be valuable tools by which to understand the biogeochemical reactions controlling carbonate alkalinity in groundwater and watersheds (MUls, 1988 Kendall et al., 1992 see Chapter 5.14). 

Drake, J.J., 1980, The effect of soil activity on the chemistry of carbonate groundwaters. Water Resources Research, 16 381-386. 

Figure 1.1. Natural water environments of interest in aquatic chemistry. Water links elemental cycles of the atmosphere with those of the sediments. Atmospheric chemistry, water chemistry, sediment geochemistry, soil chemistry, and groundwater chemistry of the elements are needed.

Figure 9.10 Log([Na ]/[H+]) versus log[H4SiO J diagram at 25 C and 1 bar pressure. The figure shows a stability field for an idealized sodic montmorillonite. Plotted on the diagram are analyses of groundwaters from various rock types. A lutite is a shale or mudstone that probably contains illite and kaolinite, with smaller amounts of smectite clays such as montmorillonite. Sandstones include feldspars as well as quartz. Note that most of the water analyses fall in the kaolinite field. After O. P. Bricker and R. M. Garrels, Mineralogic factors in natural water equilibria. In Principles and applications of natural water chemistry, ed. S. Faust and J. V. Hunter. Copyright 1965. Reprinted by permission.

In their study of the Canadian uranium deposit at Cigar Lake, Cramer and Smellie (1994) have plotted data for K, Na+, Ca +, and Mg +, in site waters on log([M"]/[H+]") versus log[H4Si04] diagrams. In Fig. 9.15, the illite phase field is contoured to show the stabilities of different illite fractions in I/S. The plot describes the evolution of water chemistry from atmospheric precipitation and surface-waters (lakes and streams) to infiltrating soil water and groundwater above, and then in contact with, the orebody. In the soil, kaolinite and illite (the dominant clay), quartz, and feldspars are... 

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