Groundwater mineral content

Once a bioremediation effort is started, the bioreactions that occur in the presence of added electron acceptors will result in significant variations of water chemistry across the three-dimensional area of the aquifer. Careful monitoring of these variations is an important indicator of the effectiveness of the remediation process. 

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Several important parameters control aquifer bioremediation projects. These include hydraulic conductivity, soil structure and stratification, groundwater mineral content, groundwater pH, temperature, microbial presence, and bench-scale testing, as further discussed below. 

Because carbon dioxide is about 1.5 times as dense as air and 2.8 times as dense as methane, it tends to move toward the bottom of the landfill. As a result, the concentration of carbon dioxide in the lower portions of landfill may be high for years. Ultimately, because of its density, carbon dioxide will also move downward through the underlying formation until it reaches the groundwater. Because carbon dioxide is readily soluble in water, it usually lowers the pH, which in turn can increase the hardness and mineral content of the groundwater through the solubilization of calcium and magnesium carbonates. 

The lithological parameter is only one of several parameters that control groundwater quality. Other factors include evaporation at the surface prior to infiltration, transpiration, wash-down of sea spray, and reducing conditions in the aquifer, connected to H2S production. Water moves underground, and its salt or mineral content is determined by all soil and rock types it passes through. Thus, occasionally, saline water may be encountered in rocks that by themselves do not contribute soluble salts. 

Fen. A peatland covered by water, receiving inputs from groundwater and/ or surface flow, and generally having a higher mineral content than a bog. 

About 97% of Earth s water is in the oceans. This saline water contains vast amounts of dissolved minerals. More than 70 elements have been detected in the mineral content of seawater. Only four of these—chlorine, sodium, magnesium, and bromine—are now commercially obtained from the sea. The world s fresh water comprises the other 3%, of which about two-thirds is locked up in polar ice caps and glaciers. The remaining fresh water is found in groundwater, lakes, rivers, and the atmosphere. 

Since groundwater is in contact with the soil, it is usually enriched with minerals. If it is in contact with hard rock, however, the mineral content is small. Groundwater comes to the surface in springs if the water then contains large quantities of mineral salts, it is known as mineral water. Among the forms of mineral water, we may list ... 

U-bearing minerals and adsorption processes (Salah et al. 2000 Perez del Villar et al. 2000). The vertical and lateral flow of groundwater is responsible for the oxidation and dissolution of primary sulphides, leading to acidic solutions that facilitated the oxidation and dissolution of uraninite. The resulting uranyl cations migrated and precipitated as uranyl minerals, mainly phosphates, silicates, silico-phosphates. In certain local conditions, reduction of these uranyl cations allowed precipitation of coffinite with a high content of P and LREE. Adsorption of uranium, together with P, mainly occurs on Fe-oxyhydroxides, but this kind of uranium retention seems less efficient than the precipitation, at least in the close vicinity to the... 

In this case study, the selected phases are pyrite, amorphous FeS, calcite (present in limestones in the roof strata Fig. 5), dolomite (possibly also present in the limestones), siderite (which occurs as nodules in roof-strata mudstones), ankerite (present on coal cleats in the Shilbottle Seam), melanterite and potassium-jarosite (representing the hydroxysulphate minerals see Table 3), amorphous ferric hydroxide (i.e., the ochre commonly observed in these workings, forming by precipitation from ferruginous mine waters), and gypsum (a mineral known to precipitate subaqueously from mine waters with SO4 contents in excess of about 2500 mg/L at ambient groundwater temperatures in this region, and with which most of the mine waters in the district are known to be in equilibrium). In addition, sorption reactions were included in some of the simulations, to contribute to the mole transfer balances for Ca, Na, and Fe. 

The removal of Ra by adsorption has been attributed to ion exchange reactions, electrostatic interactions with potential-determining ions at mineral surfaces, and surface- precipitation with BaSO 4. The adsorptive behavior of Ra2+ is similar to that of other divalent cationic metals in that it decreases with an increase in pH and is subject to competitive interactions with other ions in solution for adsorption sites. In the latter case, Ra is more mobile in groundwater that has a high total dissolved solids (TDS) content. It also appears that the adsorption of Ra + by soils and rocks may not be a completely reversible reaction (Benes et al. 1984, 1985 Landa and Reid 1982). 

This process consumes oxygen and produces C02. As a result, the oxygen content of air in soil may be as low as 15%, and the carbon dioxide content may be several percent. Thus, the decay of organic matter in soil increases the equilibrium level of dissolved C02 in groundwater. This lowers the pH and contributes to weathering of carbonate minerals, particularly calcium carbonate. 

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