Concentrations of dissolved sulfate

Geochemists (e.g., Thorstenson et al., 1979 Thorstenson, 1984) have long recognized that at low temperature many redox reactions are unlikely to achieve equilibrium, and that the meaning of Eh measurements is problematic. Lindberg and Runnells (1984) demonstrated the generality of the problem. They compiled from the watstore database more than 600 water analyses that provided at least two measures of oxidation state. The measures included Eh, dissolved oxygen content, concentrations of dissolved sulfate and sulfide, ferric and ferrous iron, nitrate and ammonia, and so on. 

The redox potential within the cells is substantially lower than in the plasma (May and Williams, 1980), and may vary depending upon particular cellular biochemical activities and a myriad of potential redox couples such as reduced and oxidized glutathione species. In general, greater levels of reduced glutathione in the intracellular fluids than in the plasma may provide an indication of an overall lower oxidation condition within the cells. However, it is interesting to note that intracellular fluids have relatively high concentrations of dissolved sulfate (Table 4), in spite of the more reduced conditions inferred to be present. 

Gradients in stable sulfur isotope ratios and concentration of dissolved sulfate in... 

Attack associated with nonuniformity of the aqueous environments at a surface is called concentration cell corrosion. Corrosion occurs when the environment near the metal surface differs from region to region. These differences create anodes and cathodes (regions differing in electrochemical potential). Local-action corrosion cells are established, and anodic areas lose metal by corrosion. Shielded areas are particularly susceptible to attack, as they often act as anodes (Fig. 2.1). Differences in concentration of dissolved ions such as hydrogen, oxygen, chloride, sulfate, etc. eventually develop between shielded and nearby regions. 

Geochemical results show that the degree of sulfide oxidation is dependent upon the temperature of the piles and the rock sulfide content. In the basal drain effluent of the Type III pile, a decrease in pH was observed throughout the summer as the pile warmed. Sulfate concentrations also increase with the warming of the pile and decrease as the pile cools. The decrease in pH is correlated with an increase in the concentrations of dissolved metals. 

The results of dissolved sulfate concentrations are summarized in Figure 4D. Sulfate concentrations are highest in the top of the evaporative panne (core 1) sediments. Sediments of the evaporative panne and tidal creek (cores 1 and 3 respectively) do not reproduce the anticipated closed system behavior for sediments undergoing sulfate reduction, i.e. progressive decrease with depth (12). 

Although lead and cadmium sulfate are both soluble, a body of water contaminated with these toxicants in the presence of sulfate and biodegradable organic matter shows very low concentrations of dissolved lead and cadmium, although levels are relatively high in the sediments of the body of water. Explain. 

Inorganic sulfur compounds are at a much lower concentration in surface waters than in the ocean. Nevertheless, rivers move a large amount of dissolved sulfate to the sea each year (Meybeck, 1987) and industrial activities and agriculture have added much to this flux. Typically estimates are perhaps a little less than a lOOTg(S) yr with additional loads of the same magnitude as those from industrial and agricultural sources. There is also some... 

The exposure of sulfide minerals contained in mine wastes to atmospheric oxygen results in the oxidation of these minerals. The oxidation reactions are accelerated by the catalytic effects of iron hydrolysis and sulfide-oxidizing bacteria. The oxidation of sulfide minerals results in the depletion of minerals in the mine waste, and the release of H, SO4, Fe(II), and other metals to the water flowing through the wastes. The most abundant solid-phase products of the reactions are typically ferric oxyhydroxide or hydroxysulfate minerals. Other secondary metal sulfate, hydroxide, hydroxy sulfate, carbonate, arsenate, and phosphate precipitates also form. These secondary phases limit the concentrations of dissolved metals released from mine wastes. 

Recrystallization. The suspension of crystals obtained above is centrifuged (20,000 r.p.m. at 0°) and the crystals are dissolved in M/30 phosphate buffer, pH 6.0, containing 5% of sodium chloride, to a concentration of about 30 mg. of protein/ ml. The protein dissolves slowly, but completely, in 1-2 hours. The concentration of ammonium sulfate is estimated with Nessler reagent." By adding a saturated solution of ammonium sulfate as above, the concentration is raised to s 0.23. The solution is then nucleated with /3-galactosidase crystals, and is further stirred. Crystals begin to appear after H hour, and the process is complete in 24-36 hours. The product has a specific activity of 575,000 yield, 65%. 

Biological activities, such as photosynthesis and respiration, physical phenomena, such as natural or induced turbulence with concomitant aeration, and above all processes such as the precipitation and dissolution of CaC03 and of other minerals influence pH regulation through their respective abilities to decrease and increase the concentration of dissolved carbon dioxide. Besides photosynthesis and respiration, other biologically mediated reactions affect the H" ion concentrations of natural waters. Oxygenation reactions often lead to a decrease in pH, whereas processes such as denitrification and sulfate reduction tend to increase pH. 

---