Chloride pore water profiles

Assuming oxidized glutathione as the disulfide responsible for the polarographlc wave at -0.59 V, the disulfide concentrations were calculated as 5 uM and 139 uM for the 0-3 and 3-6 cm depths respectively. Below 12 cm, the pore water profile is dominated hy inorganic sulfide. Inorganic sulfide is not present when thiols are present. The thiol concentration Increases with depth until just above the onset of the inorganic sulfide zone which shows increased sulfide content with depth. The highest concentration of thiol corresponds to the pH minimum and to sulfate production as evidenced by the excess sulfate values relative to open ocean sulfate chloride ratios ( ASO in Tables IV and V). 

Most commonly observed pore-water concentration profiles, (a) A nonreactive substance, such as chloride (b) a chemical, such as O2, which undergoes removal in the surface sediment as a result of aerobic respiration (c) a chemical that is consumed by a reaction that occurs in a subsurface layer, such as Fe2+(aq) precipitating with S2-(aq) to form FeS2(s) (d) a chemical released in surface sediments, such as silica via dissolution of siliceous hard parts (e) a chemical released into pore waters from a subsurface layer, such as Mn +(aq) by the reduction of Mn02(s) and (f) a chemical released at one depth (reactive layer 1), such as Fe2+(aq) by reduction of FeOOFI(s), and removal at another depth (reactive layer 2), such as Fe +(aq) precipitating as FeS2(s). Source From Schulz,... 

Another example that can be assessed with this analytical solution results from the following considerations At the beginning of the Holocene, about 10,000 years ago, the sea level rose more than 100 m as a result of thawing ice, which is equivalent to 3 % of the entire water column. This means that seawater had been previously about 3 % higher in concentration. If we assume a chloride concentration of 20,000 mg/1 in the seawater today, and thus a mean concentration of 20,600 mg/1 in seawater of the ice age, then we are able to calculate the non-steady state chloride profile in pore water with the application of the analytical solution of Equation 3.26. 

Fig. 3.10 Calculated concentration profile in the pore water of a marine sediment according to an analytical solution of Pick s Second Law of Diffusion. For reasons of simplification it was assumed that the seawater contained 3 % less chloride concentration since the beginning of the Holocene as a result of thawing ice. This lower concentration (20,000 mg/1) had enough time over 10,000 years to replace the higher concentration (20,600 mg/1) from the sediment.

Fig. 14.16 Comparison of AT anomalies (blue lines) to gas hydrate content estimated dissolved chloride distribution (red lines), and given as percent occupancy of the pore space. Leg 204. Green lines denote estimates based on data from pressure core barrel deployments, the depth of seismic reflectors corresponding to the bottom of the GHSZ (BSR). Location of Insert B shows the temperature profile derived from an infrared image in the vicinity of from Site 1245, and the corresponding chloride concentration in closely-spaced pore water depth between the two graphs is due to the removal of core as gas expansion voids between collected and the pore water samples were taken (modified from Trehu et al. 2004a).

Fig. 1. Chloride (a) and sulphate (b) squeezed pore-water concentration profiles for three boreholes in Pliocene mudrocks at Orciatico, Tuscany, Italy. Boreholes 15, II and 12 (represented by open circles, open squares and an open diamond respectively) are at increasing distance from the exposed contact with the intrusion (40, 150 and approximately 1000m). Adapted from Rochelle et al. (1998).

Assuming that the formation is derived from deposition of marine sediments, the initial pore-water composition would approximate to the salinity of seawater. Pure diffusion computer modelling of these data have enabled ANDRA to predict that the chloride profiles could have been derived from seawater diffusing out of the formation over a period of 100 Ma... 

Fig. 2. Estimated pore-water chloride profiles for a Vraconian (Lower Cretaceous) mudrock formation in Southern France. Borehole MAR203 (a) profiles the whole formation, whilst MAR402 (b) covers the middle to base of the target formation. Data derived from both aqueous leaching of residual solutes (open circles) and mechanical squeezing (open squares) are shown. Adapted from Cave Reeder (1997).

Fig. 3. Pore-water chloride profiles obtained by centrifugation extraction (a) and aqueous leaching of residual solutes (b) from a deep Sellafield borehole. Pore-water data reconstructed by simple mathematical correction (open circles) and multivariate statistical analysis (open squares) are compared to groimdwater data obtained from hydraulic tests (closed squares). Depths are m below rotary table (mbrt). The 2cr error bars are based on a combination of analytical and sampling errors. Adapted from Bath et al. (1996).

The anomalous behaviour for potassium chloride matrices with a value <0.5 emphasizes the complex release of this drug. Peppas [8] did not interpret values of <0.5 but stated that such occurrences were an indication of statistical analysis problems or were due to diffusion through a polymeric network where diffusion occurred partially through a swollen matrix and partly through water-filled pores. In this case, in order to investigate the mechanism of release, the percentage release v. time profile was evaluated for goodness of fit. The details of the use of this statistical... 

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