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Saturated zone concentrations

Trichloroethylene in soil and groundwater were found to be correlated (r 0.9994) in samples taken during well instillation at the U.S. Army Cold Regions Research and Engineering Laboratory in Hanover, NH (Hewitt and Shoop 1994). Concentrations of trichloroethylene in soil from the saturated zone were 0.008-25 mg/kg, while concentrations in the groundwater were 0.044-180 ppm. [Pg.219]

Introduction of the flushing solution may occur within the vadose zone, the saturated zone, or both. Flushing solutions may consist of plain water, or surfactants, co-solvents, acids, bases, oxidants, chelants, and solvents. The infiltrating flushing solution percolates through the soil and soluble compounds present in the soil are dissolved. The elutriate is pumped from the bottom of the contaminated zone into a water treatment system to remove pollutants. The process is carried out until the residual concentrations of contaminants in the soil satisfy given limits. [Pg.563]

In zone a of Figure 2.5, the kinetics are first order with respect to [S], that is to say that the rate is limited by the availability (concentration) of substrate so if [S] doubles the rate of reaction doubles. In zone c however, we see zero order kinetics with respect to [S], that is the increasing substrate concentration no longer has an effect as the enzyme is saturated zone b is a transition zone. In practice it is difficult to demonstrate the plateau in zone c unless very high concentrations of substrate are used in the experiment. Figure 2.5 is the basis of the Michaelis-Menten graph (Figure 2.6) from which two important kinetic parameters can be approximated ... [Pg.39]

Mean aqueous concentrations of trichloroethene (TCE) in a contaminated aquifer were measured to be 25 ig/L. The water table is located 4 m below the soil surface. The saturated zone has a mean thickness of 50 m and an average porosity ( ) of 0.3. Water temperature in the aquifer is 10°C. [Pg.847]

Evapotranspiration returns distilled water into the atmosphere. The salts, dissolved in the original precipitation water, remain in the soil zone, and at the end of dry seasons some of these salts accumulate on the surface. The next rain event redissolves these salts, and eventually they are brought into the saturated zone. Thus recharge water is richer in atmospherically derived salts than the original precipitation. The factor by which the chlorine concentration in the recharge water is greater than its concentration in the respective precipitation serves as a semiquantitative tool to estimate the amount of water transferred to the atmosphere by evapotranspiration (section 6.15). [Pg.35]

In the saturated zone the chloride concentration stays constant unless mixing of different water types occurs. A chloride concentration that decreases along a suggested groundwater flow direction indicates the suggested flow path model is not valid, as there is no process that can reduce... [Pg.61]

A chlorine concentration of 5mg/l is found in the precipitation of many rainy terrains, but the respective groundwaters often contain around 50mgCl/l. Thus, ETmci,.x (5/50) x 100= 10% that is, 10% of the initially infiltrating water reaches the saturated zone as effective recharge. [Pg.151]

Rain and surface waters equilibrate with air, becoming saturated with dissolved oxygen. Equilibration with soil air goes on until water reaches the saturated zone, where it is isolated from further contact with air. The concentration of dissolved oxygen in air-saturated water depends on... [Pg.174]

In the saturated zone, water is isolated from the atmosphere and the tritium concentration drops due to radioactive decay the original tritium concentration of 5TU drops to 2.5 TU after 12.3 years, only 1.2TU are left after another 12.3 years, and so on. [Pg.211]

Assume that water entered the saturated zone 4000 years ago with an initial concentration of 100 pmc and emerges at present in a well. How much 14C will it contain The answer, read from Fig. 11.1, is 62 pmc. [Pg.237]

Answer 6.11 Extreme degree of evaporation of surface water and soil water in the dry season, resulting in the concentration of rainborne salts in playas and salinas. During extra-heavy rain events these salts are redissolved and transported by the recharge water into the saturated zone. This process is common in certain arid zones. [Pg.426]

A common procedure is to add the nutrients in solution through injection wells into the saturated zone or through infiltration galleries into the unsaturated or surface-soil zone. Water is recovered from production wells, then amended with nutrients, and recirculated. The concentrations of contaminants and nutrients are often measured on a regular basis by taking samples from wells installed between the points of injection and removal. In some instances, water is not recirculated but, instead, is treated at the surface. [Pg.292]

Solution of these equations with appropriate boundary and initial conditions gives the contaminant concentration in both space and time which is the objective of the exrcise. Highly simplified problems (1) and (2) can have analytical solutions (see for example Ogata and Banks [ 3]) but for most real problems, numerical techniques such as finite differences or finite elements have to be used. For the saturated zone examples discussed below, the solutions were obtained using finite difference techniques on the computer of Delft Soil Mechanics Laboratory. [Pg.146]

Higher concentrations of As tend to be found more in groundwater than in surface water sources of drinking water therefore, the emphasis of this paper is on the geochemical processes that affect As transport in groundwater. However, many of the processes discussed are also applicable to surface waters and the variably saturated zone above the groundwater table. [Pg.68]

FIGURE 1. Changes in concentration of organic carbon from precipitation to interstitial waters of soil (unsaturated zone) and in saturated zone of groundwater based on Leenheer et al. (1974), Wallis (1979), Dawson et al. (1981), Antweiler and Drever (1983), Meyer and Tate (1983), and Thurman (1985). [Pg.89]

As explained in the first section of this chapter, low concentrations of humic substances occur in groundwater from the saturated zone. Thus, geochemi-... [Pg.99]

Subsurface contamination by organic-rich wastes from landfills, leaky septic tanks, sewerage tile fields, and toxic-waste dumps, can also produce high CO2 concentrations in both the unsaturated and saturated zones. For example, a shallow well 50 m from two septic tanks had an apparent CO2 pressure of 10 bar (see Chap. 6 and Table 6.7, analyses 3 to 5 and 9). [Pg.158]


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See also in sourсe #XX -- [ Pg.215 ]




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