In aquifer

Adsorption of Metal Ions and Ligands. The sohd—solution interface is of greatest importance in regulating the concentration of aquatic solutes and pollutants. Suspended inorganic and organic particles and biomass, sediments, soils, and minerals, eg, in aquifers and infiltration systems, act as adsorbents. The reactions occurring at interfaces can be described with the help of surface-chemical theories (surface complex formation) (25). The adsorption of polar substances, eg, metal cations, M, anions. A, and weak acids, HA, on hydrous oxide, clay, or organically coated surfaces may be described in terms of surface-coordination reactions ... 

Suflita JM, Gibson SA, Beeman RE. 1988. Anaerobic biotransformations of pollutant chemicals in aquifers. J Ind Microbiol 3 179-194. 

Metwally M E-S, NL Wolfe (1990) Hydrolysis of chlorostilbene oxide. II. Modelling of hydrolysis in aquifer samples and in sediment-water systems. Environ Toxicol Chem 9 963-973. 

Krumme ML, KN Timmis, DF Dwyer (1993) Degradation of trichloroethylene by Pseudomonas cepacia G4 and the constitutive mutant strain G4 52223 PRl in aquifer systems. Appl Environ Microbiol 59 2746-2749. 

Munakata-Marr J, PL McCarty, MS Shields, M Reagin, CS Francesconi (1996) Enhancement of trichloroethylene degradation in aquifer microcosms bioaugmented with wild-type and genetically altered Burk-holderia Pseudomonas cepacia G4 and PRl. Environ Sci Technol 30 2045-2052. 

Salanitro JP (1993) The role of bioatttenuation in the management of aromatic hydrocarbon plumes in aquifers. Ground Water Monit Remed 13 150-161. 

Seki, Y. (1990) Gas concentration in aquifer fluid prior to boiling in the Oku-aizu geothermal system, Fukushima, Japan. Geochem. J., 24, 105-121. 

The ubiquity of groundwater ( " U/ U) ratios above the equilibrium value attests to the widespread operation of preferential release processes in aquifers. Since the U isotopes are long-lived, the concentrations cannot be assumed to be in steady state, adding difficulties to unravelling the causes of U isotopic variations. However, U... 

The two most promising options are storage in aquifers (ATES) and storage through borehole heat exchangers (BTES). These concepts have already been introduced as commercial systems on the energy market in several countries. Another option is to use underground cavities (CTES), but this concept is so far rarely applied commercially. 

Many minerals have been found to dissolve and precipitate in nature at dramatically different rates than they do in laboratory experiments. As first pointed out by Paces (1983) and confirmed by subsequent studies, for example, albite weathers in the field much more slowly than predicted on the basis of reaction rates measured in the laboratory. The discrepancy can be as large as four orders of magnitude (Brantley, 1992, and references therein). As we calculate in Chapter 26, furthermore, the measured reaction kinetics of quartz (SiC>2) suggest that water should quickly reach equilibrium with this mineral, even at low temperatures. Equilibrium between groundwater and quartz, however, is seldom observed, even in aquifers composed largely of quartz sand. 

In aquifers containing significant amounts of natural organic matter, benzene migration is retarded by sorption to the organic surfaces. 

Solid - phase arsenic concentrations are low in aquifer sands in both high and low arsenic zones - generally 2 parts per million (ppm) or less. In fine grain sediments, arsenic levels are typically 5 -10 ppm in both the low and high arsenic zones, peaking at 20 ppm near the surface in the channel-fill silts (borehole 20, Fig. 2). 

Rittman, B. E., McCarty, P. L. and Roberts, P. V. (1980). Trace-organics biodegradation in aquifer recharge, Ground Water, 18, 326-343. 

Studies have indicated that large-scale storage could take place with gaseous hydrogen underground in aquifers, depleted petroleum or natural gas reservoirs or man made caverns from mining operations. One of... 

Just as oil, natural gas is also categorised as conventional and unconventional. Unlike crude oil, however, natural gas deposits are normally classified according to the economic or technical approach, i.e., all occurrences that are currently extract-able under economic conditions are considered conventional, whereas the rest are termed unconventional. Conventional natural gas includes non-associated gas from gas reservoirs in which there is little or no crude oil, as well as associated gas , which is produced from oil wells the latter can exist separately from oil in the formation (free gas, also known as cap gas, as it lies above the oil), or dissolved in the crude oil (dissolved gas). Unconventional gas is the same substance as conventional natural gas, and only the reservoir characteristics are different and make it usually more difficult to produce. Unconventional gas comprises natural gas from coal (also known as coal-bed methane), tight gas, gas in aquifers and gas hydrates (see Fig. 3.17). It is important to mention in this context so-called stranded gas , a term which is applied to occurrences whose extraction would be technically feasible, but which are located in remote areas that at the moment cannot (yet) be economically developed (see Section 3.4.3.1). 

Properties and extraction processes Aquifer gas, also referred to as geo-pressured gas or brine gas, is natural gas found dissolved in aquifers, primarily in the form of methane. The solubility of natural gas, and thus the methane content of the water, can vary significantly, and depend on factors, such as the total pressure, temperature, salt content of the water and amount of other gases dissolved. The amount of gas dissolved in underground liquids increases substantially with depth. A general rule is that the deeper the aquifers and the higher the pressure, the higher the gas content. At depths down to 5 km, up to 5 m3 of methane can be dissolved per m3 of water in aquifers under normal hydrostatic pressure (load of water) under lithostatic pressure (load of water and rocks), this factor may increase to more than... 

Bentall, R. (compiler), 1963b, Shortcuts and Special Problems in Aquifer Tests. U.S. Geological Survey Water-Supply Paper 1545-C, pp. C1-C117. 

Thermally enhanced extraction is another experimental approach for DNAPL source removal. Commonly know as steam injection, this technique for the recovery of fluids from porous media is not new in that it has been used for enhanced oil recovery in the petroleum industry for decades, but its use in aquifer restoration goes back to the early 1980s. Steam injection heats the solid-phase porous media and causes displacement of the pore water below the water table. As a result of pore water displacement, DNAPL and aqueous-phase chlorinated solvent compounds are dissolved and volatilized. The heat front developed during steam injection is controlled by temperature gradients and heat capacity of the porous media. Pressure gradients and permeability play a less important role. 

The key factors that determine the effectiveness of bioremediation in aquifers are ... 

Salanitro, J. R, 1993, The Role of Bioattenuation in the Management of Aromatic Hydrocarbon Plumes in Aquifers Ground Water Monitoring and Remediation, Fall, 1993, Vol. 13, No. 4, pp. 150-161. 

Table 4.6 gives a few representative values for Kow and Kp for non-polar organic substances on typical soil material and Table 4.7 gives estimates on typical retardation factors estimated for an aquifer. The data show that many non-polar organic substances, with the possible exception of very lipophilic substances such as hexachlorobenzene, are not markedly retarded in aquifers that contain little organic material (foe = 0.001 - 0.005). On the other hand, such substances are effectively retained in soils rich in organic carbon. 

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