Pore water density

Pore water density (pp ) is needed in some calculations such as to derive pore water volume from pore water mass. The pore water density is usually assumed to be constant (1.024 gm /cm). However, pore water density (pp ) is a function of the density of pure water (p ), the density of salt (p ait)/ salinity (r), temperature (T), and pressure (p)  

The effect of salinity on pore water density and the calculation of both bulk density and grain density can be illustrated using the equation for seawater density at 1 atm presented by Millero and Poisson (1981). The results are presented in Table 6.3. A review shows that the effect is relatively small, and decreases with decreasing water content of the samples. Usually, the resulting changes are not significant for the purpose of the measurements. Extraction of pore water from a soil sample and the determination of its soluble salt content by refractometer has been standardized in ASTM D4542. 

Example of Effect of Pore Water Density on Calculated Bulk Density 

Salinity Pore Water Density (gm/cm ) Measured Bulk Density (gm/cm ) Calculated Bulk Density (gm/cm ) 

The total wet density is usually referred to as the bulk density or total density (p ). It is defined as the total wet sample mass (M,) divided by the total wet sample volume (IQ, or 

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This can be expressed in terms of pore water content (w, in %) and bulk density (p) as determined above, and the pore water density p . 

It is usually sufficient to assume a value of 35 ppt for salinity because the salt content of deep ocean waters do not vary a great deal. However, this is not always the case. Salinity of more than 60 ppt have been measured by the Ocean Drilling Program on Leg 150. However, it is a simple matter to measure the actual salt content if a more accurate analysis is desired, refer to Chaney et al. (1983). Changes in salinity also change pore water density, which affects the result of some of the calculations (e.g., calculated density of solids, or grain density). 

A series of processes will control the behaviour of C02 in saline aquifer formations. First, the C02 will displace the formation water (brine) originally in place and will lead to a local increase in pore fluid pressure (van der Meer, 1992). The injected C02 will not be distributed evenly, but will finger out, owing to the lower density than the pore waters and the heterogeneities of the aquifer. Doughty et al. (2001) point out that the shape of the C02 plume in the aquifer will be highly site- and case-specific. Carbon dioxide will rise to the top of the aquifer and migrate at the bottom of the... 

The actual density of clay minerals is 2.7g/cm. but these solids are surrounded by pore waters as they accumulate in the sediments. An average wet density of marine sediments is estimated at 1.6g/cm ... 

Figure 2.13 Effect of mixing of pore water by tubificid worms on profiles of P concentration in submerged soil calculated with Equations (2.37) and (2.40). Numbers on curves are densities of tubificids...

The density of coal shows a notable variation with rank for carbon content (Figure 6.1) and, in addition, the methanol density is generally higher than the helium density because of the contraction of adsorbed helium in the coal pores as well as by virtue of interactions between the coal and the methanol, which results in a combined volume that is notably less than the sum of the separate volumes. Similar behavior has been observed for the water density of coals having 80 to 84% w/w carbon. 

To evaluate the effects of cosolvent on surfactant delivery and PCE recovery, Box B was flushed with 4% Tween 80 + 5% EtOH at a Darcy velocity of 4.8 cm/hr. The surfactant/cosolvent mixture, which had a density of 0.994 g/cm3, was also representative of a neutral buoyancy flood solution (Shook et al, 1998). It is important to recognize that "neutral buoyancy" refers to density of flushing fluid after solubilization of the DNAPL. Thus, the initial density of the surfactant formulation must be less than that of the resident aqueous phase. Figure 5b shows the location and shape of the 4% Tween 80 + 5% EtOH front after flushing Box B with 0.5 pore volumes of solution. The lower density of the 4% Tween 80 + 5% EtOH solution (0.994 g/cm3) relative to the density of resident pore water (0.998 g/cm3) caused the injected solution to flow preferentially along the top of Box B (Figure 5b). This effect can become severe at low flow rates (Taylor, 1999). The... 

D = dispersion coefficient v = average pore water velocity p = bulk density 0 = saturated water content x = distance in the direction of flow t = time. 

As it can be observed in Table I, the volumes obtained from water adsorption are quite similar to the calculated micropore and mesopore volume. These results indicate that the approach considered in this study is suitable. Water adsorbs initially on microporosity (up to P/Po 0.6), as a solid-like structure. In these pores the density of adsorbed water can be considered to be similar to the ice density. On the other hand, the similar values of Vmeso and Vh2o 0.6-0.95 indicate that water adsorbs on mesopores as a liquid. 

Pore volumes have been obtained from water adsorption considering two different water densities. The density of water in solid phase (0.92 g/cc) has been used to estimate the micropore volume from the amount of water adsorbed until relative pressure around 0.6. In the other hand, the liquid water density has been used to calculate the water volume adsorbed on the relative pressure range around 0.6-0.95. The pore volumes obtained from water adsorption data are quite similar to the corresponding micropore and mesojxrre volumes obtained by nitrogen adsorption, which seems to corroborate that water adsorbs in the microporosity as solid ice, while it adsorbs in the mesoporosity as liquid. 

Figure 3 Comparison of pore water CH4 concentrations (circles) with root density depth distribution (dry weight mass of roots per 3 cm depth interval of a 6.5 cm diameter core) (hars) in a wet meadow site at the Toohk Lake LTER site, 1995 (source King et al., 1998).

In Eq. [3-22], concentration is expressed as mass of chemical per volume of porous media. The volume of porous media, also termed aquifer volume, is defined to include both particle grains and pore water. Equation [3-22] can be rewritten in terms of the aqueous chemical concentration (Caq), the sorbed chemical concentration (Cs), the water-filled porosity, n, the distribution coefficient Kd, and the bulk density of the porous material pb. Bulk density is defined as the weight of dry solids divided by the volume of aquifer from which they were taken. 

Copper concentration in pore water = ICC6 mol/liter Copper concentration on aquifer solids = ICC3 mol/kg Aquifer bulk density = 2.5 g/cm3 Aquifer porosity = 0.3. 

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