Alkalinity pore water profiles

The pore-water profiles also indicate a possible treatment effect. In the treatment basin before acidification to pH 4.7, much higher levels of ANC (alkalinity) and higher pH were found in the pore water just 1-2 cm below the sediment-water interface (59). In contrast, pore-water pH profiles obtained in the same site in the summers of 1990 and 1991 show pH < 5.0 in the upper 5-10 cm of sediment. Corresponding profiles for a site in the reference basin did not show such a depression (Figure 6a ref. 4). 

Fig. 14. Pore-water profiles of SO, NH4, HPO4, and alkalinity at FOAM, NWC, and DEEP (gravity cores). Profiles from a given station are arranged horizontally.

Figure 8.25. Some chemical and diagenetic properties of organic-rich marine sediments as a function of depth based on DSDP interstitial water profiles. A. Schematic gradients of SO42-, total alkalinity, Ca2+ and Mg2+ in pore waters, and zones of sulfate reduction, methanogenesis and fermentation. Magnesium diffuses into the sediment and organogenic dolomite forms at depth. B. Logarithm of calculated saturation states of interstitial waters with respect to dolomite. Dolomite saturation=0. All these pore waters are oversaturated with respect to dolomite. (After Compton, 1988.)...

There are some minor but important differences between the profiles of the three pore-water constituents at NWC. Structure in the alkalinity profile is small because the values are very close to seawater in magnitude, nevertheless the seasonal pattern described is evident. Ammonia most clearly follows the seasonal pattern of change. Concentration max-... 

FOAM follows the same general time sequence and pattern of change in pore-water concentration profiles as NWC, but with several important differences (Figs. 19, 22, and 25). The high pore-water concentrations at FOAM allow alkalinity to more clearly reflect seasonal patterns. These... 

Fio. 19. Seasonal pore-water alkalinity profiles from box cores at FOAM (overlying water... 

Fig. 3.14 Concentration profiles of pore water from anoxic sediments obtained from an upwelling area off Namibia at a water depth of approximately 1300 m. The analysis of sulfide and methane was carried out in samples that were punched out with syringes from small and quickly sawed-out windows in the fresh sediment core. As for sulfide, these syringe-drawn samples were brought into an alkaline environment, whilst for methane analysis the samples were stored in head space vials for subsequent gas-chromatography analysis. The arrow points to a methane sample that originated from a sealed sediment core obtained by using a sample from the core catcher (after Niewohner et al. 1998).

Fignre 3.1 shows the characteristic profiles of ammoninm and phosphate concentrations that were measnred by photometrical aialysis of pore water obtained from reactive sediments possessing a high amonnt of organic matter. Both parameters demonstrate qnite similarly shaped curves compared to alkalinity. Here, the ratio of the concentrations derived from both profiles lies close to the C N P Redfield-ratio of 106 16 1 and clearly documents their release into the pore water due to the decomposition of organic matter. A typical photometric nitrate profile in reactive sediment zones near the sediment surface is shown in the quantitative evaluation of fluxes and reaction rates presented in Figure 3.7. 

Fig. 15.10 Model calculation of sulfate in pore water, alkalinity and methane in an explicit numeric solution of Pick s Second Law, accounting for the reaction between sulfate and methane and the alkalinty which is affected thereby. The adjustment to the measured profiles depends on the time passed since the slide occurrence and thus permits the reconstruction of the time of its occurrence which took place about 300 years ago.

The interactions of molybdate at the waste/soil interface has been studied by combining acidic, neutral and alkaline ash with sand, clay and peat respectively. The Mo tracer was added to the ash and the diffusion of Mo into the soil was measured. Since the difference in pore water concentration of Mo between coal ash and soil is large (10), the tracer reflects the behaviour of the stable Mo, consequently the Mo-radioactivity profiles can be... 

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