Saturation depth

The value of the saturation concentration,, is the spatial average of the value determined from a clean water performance test and is not corrected for gas-side oxygen depletion therefore K ji is an apparent value because it is determined on the basis of an uncorrected. A tme volumetric mass transfer coefficient can be evaluated by correcting for the gas-side oxygen depletion. However, for design purposes, can be estimated from the surface saturation concentration and effective saturation depth by... 

The effective saturation depth,, represents the depth of water under which the total pressure (hydrostatic plus atmospheric) would produce a saturation concentration equal to for water ia contact with air at 100% relative humidity. This can be calculated usiag the above equation, based on a spatial average value of T, measured by a clean water test. For design purposes,, can be estimated from clean water test results on similar systems, and it can range from 5 to 50% of tank Hquid depth. Effective depth values for coarse bubble diffused air, fine bubble diffused air, and low speed surface aerators are 26 to 34%, 21 to 44%, and 5 to 7%, of the Hquid depth, respectively. 

Figure 4.6. Variation in the saturation depth of seawater with respect to calcite as a function of potential Pc02 f°r seawater at 2°C, S=35, and At=2400 ieq kg-1 seawater.

Typical vertical saturation profiles for the North Atlantic, North Pacific, and Central Indian oceans are presented in Figure 4.10. The profiles in the Atlantic and Indian oceans are similar in shape, but Indian Ocean waters at these GEOSECS sites are definitely more undersaturated than the Atlantic Ocean. The saturation profile in the Pacific Ocean is complex. The water column between 1 and 4 km depth is close to equilibrium with calcite. This finding is primarily the result of a broad oxygen minimum-C02 maximum in mid-water and makes choosing the saturation depth (SD) where Oc = 1 difficult (the saturation depth is also often referred to as the saturation level SL). 

We have calculated the saturation depth (SD) with respect to calcite for various regions of the Atlantic, Pacific and Indian oceans as shown in Figure 4.12. The saturation depth is deepest in the Eastern Atlantic ocean. In both the eastern and western Atlantic Ocean, the saturation depth becomes shallower to the south,... 

Figure 4.12. Saturation depths with respect to calcite in different areas of the ocean calculated from corrected GEOSECS data (see text).

One of the most controversial areas of carbonate geochemistry has been the relation between calcium carbonate accumulation in deep sea sediments and the saturation state of the overlying water. The CCD, FL, R0, and ACD have been carefully mapped in many areas. However, with the exception of complete dissolution at the CCD and ACD, the extent of dissolution that has occurred in most sediments is difficult to determine. Consequently, it is generally not possible to make reasonably precise plots of percent dissolution versus depth. In addition, the analytical chemistry of the carbonate system (e.g., GEOSECS data) and constants used to calculate the saturation states of seawater have been a source of almost constant contention (see earlier discussions). Even our own calculations have resulted in differences for the saturation depth in the Atlantic of close to 1 km (e.g., Morse and Berner, 1979 this book). 

One of the more "aesthetically pleasing" relations was put forth for the eastern and western Atlantic Ocean basins by Berger (1977). In his plots (see Figure 4.21) the R0, FL and CCD were generally widely separated and usually close to parallel. The saturation depth (SD) was close to coincident with the R0 level. However, even this picture has problems. If the R0 and SD are closely coincident, how can the 50% dissolution occur that is required to produce the R0 level (Adelseck, 1978) ... 

More recent calculations such as those in this book indicate substantially lower saturation depths. Those calculated here are plotted in Figure 4.21. The SD is generally about 1 km deeper than that presented by Berger (1977). Clearly the new SD is much deeper than the R0 and appears only loosely related to the FL. Indeed, in the equatorial eastern Atlantic Ocean, the FL is about 600 m shallower than the SD. If these new calculations are even close to correct, the long cherished idea of a "tight" relation between seawater chemistry and carbonate depositional facies must be reconsidered. However, the major control of calcium carbonate accumulation in deep sea sediments, with the exceptions of high latitude and continental slope sediments, generally remains the chemistry of the water. This fact is clearly shown by the differences between the accumulation of calcium carbonate in Atlantic and Pacific ocean sediments, and the major differences in the saturation states of their deep waters. 

Figure 4.21. Latitudinal variation of saturation depths (SD) and carbonate sediment facies in the eastern and western Atlantic Ocean basins. (Modified after Berger, 1977.)...

A detailed study of the chemistry of pore waters near the sediment-water interface of sediments from the equatorial Atlantic was conducted by Archer et al. (1989) using microelectrodes that were slowly lowered into the sediment. By modeling the resulting data they were able to confirm that calcite was dissolving above the saturation depth as a result of benthic oxidation of organic matter. The estimated in situ rate constant for calcite dissoluton was 1-100% day1. This rate constant is 10 to 100 times slower than the one used in previous models, which was based on experimental data. If the slower rate constant proves to be correct, then dissolution of calcite by benthic metabolic processes will be of major importance. 

Chen (1982) pointed out that excess CO2 has caused the aragonite saturation depth in the North Pacific Ocean to rise close to the sea surface. 

Another problem in comparing Berger s (42) results to those of other experiments is that all H2O2 treated pteropod samples suspended below the aragonite saturation depth completely dissolved. Morse (57) found that if the slowest possible... 

A puzzling observation has recently been made by R. A. Jahnke and D. B. Jahnke (in press). They found that in sediments above the saturation depth that contain high concentrations of calcium carbonate, the ratio of the calcium carbonate dissolution rate to the organic matter remineralization rate was substantially less than at other types of sites. They have suggested that this may be the result of exchange on carbonate particle surfaces coupled with particle mixing, but this process has yet to be clearly substantiated. 

Equations [3-8a] to [3-8c] are different applications of the Thiem equation, which estimates drawdown in an aquifer or well under steady-state conditions. As previously mentioned, it is assumed that the changes in saturated aquifer thickness are small compared with the total saturated depth. This is necessarily true in a confined aquifer, but not always in an unconfined (phreatic) aquifer. If drawdown becomes a significant fraction of the saturated aquifer thickness, more complicated expressions for drawdown are obtained see Bear (1979). For an unconfined aquifer in which drawdown is a significant fraction of the saturated thickness, Eq. [3-8a] must be expressed in terms of head instead of drawdown ... 

Aquifer characteristics include a 10-m saturated depth, a transmissivity of 2 X 10 3 m2/sec, a regional gradient of 0.0005, and a porosity of 0.25. It is proposed to remove, treat, and reinject the water to clean up the remaining trichloroethene. Water will be removed at well A, treated, and reinjected at well B, 200 m away downgradient. The spill extent is poorly known, but the consultant has assumed that if the steady-state pumping rate is sufficient to cause any contaminant midway between A and B to enter well A, all contaminant eventually will be captured. 

The photodeformation capabilities of the CN-azopolymer and the H-azopo-lymer were examined by determining the depth of the indents formed by polystyrene microspheres under LED irradiation. After photoirradiation and removal of the microspheres, regularly arranged indented patterns formed by the microspheres were observed on the surfaces of the azopolymers. The depths of the indents were plotted as a function of irradiation time for several kinds of azopolymers, as shown in Fig. 9.14. The indent depths in the azopolymer increased with increasing irradiation time. The depths of the indents saturated and reached a maximum after 30 min of photoirradiation for each of the azopolymers. The saturated depths were lowest in those azopolymers with the lowest content of azobenzene moieties. These results indicate that the photo-responsive moiety plays an important role in inducing photodeformation and that the indent depth is related to the content of the azobenzene in the azopolymers. There were no differences in photodeformation capabilities between the CN- and... 

For applications requiring a large sensing surface area, such as those measuring permittivity and conductivity of tissue, an interdigital capacitor was introduced as the capacitive element in an LC circuit. The change in capacitance resulted in a variation of the impedance and resonant frequency of the LC sensor, which can be interpreted as alterations in the permittivity and conductivity of tissue. The sensor was implanted into the phantom tissue and a saturation depth was achieved such that data were only collected from the tissue layer of interest (Yvanoff and Venkataraman 2009). 

Based on the biomass concentration Cx and the value fph.s Lambert-Beer can be used to calculate the depth 2 inside the photobioreactor where the local photon flux density fph(2 ) is equal to Iph,s- This depth will be called the saturation depth 2 ... 

The well has a diameter of 25 cm and is installed in an aquifer having a hydraulic conductivity of 0.03 cm/sec, a porosity of 0.25, and a saturated depth of 17 m. The regional hydraulic gradient is 0.014. Aquifer bulk density is 2.2 kg/liter. The area receives about 1 m/yr of rain, of which roughly half goes into aquifer recharge. Thus, an estimated radius of influence is about 1400 m. 

---