Acidity, Alkalinity, and Salinity

Aqnatic biota are sensitive to extremes of pH. Largely because of osmotic effects, they cannot live in a medinm having a salinity to which they are not adapted. Thus, a freshwater fish soon succumbs in fhe ocean, and sea fish normally cannof live in freshwater, although some fish, most notably salmon, can function in both media. Excess salinity soon kills plants not adapted to it. There are. 

FIGURE 4.3 A generalized plot of the growth of an aquatic organism as a function of pH. 

The most common source of pollutant acid in water is acid mine drainage. The sulfuric acid in such drainage arises from the microbial oxidation of pyrite or other sulfide minerals as described in Section 3.5. The values of pH encountered in acid-polluted water may fall below 3, a condition deadly to most forms of aquatic life except the culprit bacteria mediating the pyrite and iron(II) oxidation, which thrive under very low pH conditions. Industrial wastes frequently have the potential to contribute strong acid to water. Sulfuric acid produced by the air oxidation of pollutant sulfur dioxide (see Chapter 7) enters natural waters as acidic rainfall. In cases where the water does not have contact with a basic mineral, such as limestone, the water pH may become dangerously low. This condition occurs in some Canadian and Scandinavian lakes, for example. 

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Some aqueous models accept only total inorganic carbon rather than titration alkalinity or carbonate alkalinity. For this reason, the sea water analysis of Table III includes total inorganic carbon which was calculated from pH, total alkalinity and salinity using the apparent sea water constants of Mehrbach et al.(82) for the dissociation of carbonic acid and the boric acid dissociation constant of Lyman (83), as expressed by Li et al. (84). 

Some important inorganic water pollutants are mentioned earlier as part of the discussion of pollutant trace elements. Inorganic pollutants that contribute acidity, alkalinity, or salinity to water are considered separately in this chapter. Still another class is that of algal nutrients. This leaves unclassified, however, some important inorganic pollutant species, of which cyanide ion, CN , is probably the most important Others include ammonia, carbon dioxide, hydrogen sulfide, nitrite, and sulfite. 

Wood is particularly valuable for many conditions which are corrosive to common metals (e.g. acids and external exposure), and for contact with foodstuffs and beverages. It is not subject to corrosion in the electrochemical sense of the term applied to metals, but in saline conditions it can be attacked by the products of metal corrosion (alkali and iron salts) where poor technology or unsuitable wood species are used. Although wood is attacked by both extremely alkaline and acid conditions, particularly those which are oxidising, it can be employed over a wider pH range than most other materials. 

Increasing the water-wet surface area of a petroleum reservoir is one mechanism by which alkaline floods recover incremental oil(19). Under basic pH conditions, organic acids in acidic crudes produce natural surfactants which can alter the wettability of pore surfaces. Recovery of incremental oil by alkaline flooding is dependent on the pH and salinity of the brine (20), the acidity of the crude and the wettability of the porous medium(1,19,21,22). Thus, alkaline flooding is an oil and reservoir specific recovery process which can not be used in all reservoirs. The usefulness of alkaline flooding is also limited by the large volumes of caustic required to satisfy rock reactions(23). 

As a consequence of the previous considerations Kieber et al. [75] have developed an enzymic method to quantify formic acid in non-saline water samples at sub-micromolar concentrations. The method is based on the oxidation of formate by formate dehydrogenase with corresponding reduction of /3-nicotinamide adenine dinucleotide (j6-NAD+) to reduced -NAD+(/3-NADH) jS-NADH is quantified by reversed-phase high performance liquid chromatography with fluorimetric detection. An important feature of this method is that the enzymic reaction occurs directly in aqueous media, even seawater, and does not require sample pre-treatment other than simple filtration. The reaction proceeds at room temperature at a slightly alkaline pH (7.5-8.5), and is specific for formate with a detection limit of 0.5 im (SIN = 4) for a 200 xl injection. The precision of the method was 4.6% relative standard deviation (n = 6) for a 0.6 xM standard addition of formate to Sargasso seawater. Average re-... 

Vertical concentration profiles of (a) temperature, (b) potential density, (c) salinity, (d) O2, (e) % saturation of O2, (f) bicarbonate and TDIC, (g) carbonate alkalinity and total alkalinity, (h) pH, (i) carbonate, ( ) carbon dioxide and carbonic acid concentrations, and (k) carbonate-to-bicarbonate ion concentration ratio. Curves labeled f,p have been corrected for the effects of in-situ temperature and pressure on equilibrium speciation. Curves labeled t, 1 atm have been corrected for the in-situ temperature effect, but not for that caused by pressure. Data from 50°27.5 N, 176°13.8 W in the North Pacific Ocean on June 1966. Source From Culberson, C., and R. M. Pytkowicz (1968). Limnology and Oceanography, 13, 403-417. 

As previously mentioned, the primary processes responsible for variations in the deep sea C02-carbonic acid system are oxidative degradation of organic matter, dissolution of calcium carbonate, the chemistry of source waters and oceanic circulation patterns. Temperature and salinity variations in deep seawaters are small and of secondary importance compared to the major variations in pressure with depth. Our primary interest is in how these processes influence the saturation state of seawater and, consequently, the accumulation of CaC03 in deep sea sediments. Variations of alkalinity in deep sea waters are relatively small and contribute little to differences in the saturation state of deep seawater. 

Hydrilla tolerates a wide range of ecological conditions. It occurs in water that is clear to very turbid, oligotrophic to highly eutrophic and at depths of more than 15 meters. It can tolerate alkaline to acidic conditions and moderate salinity. Its low light requirement enables it to successfully compete with other submersed aquatic plants ( ). 

Dissolve the immunogen in isotonic saline (other immunogens may require slight acidity, alkalinity, or other special condition) to a volume of 0.5 ml per rabbit for the primary injection or 0.25 ml for boosters (i.e., the same concentration for both injections). Emulsify the solution with three volumes of Freund s complete adjuvant, using a double-hub connector and two syringes as described above. The total volume of emulsion will then be 2 ml per rabbit for the primary inoculation or 1 ml for a booster. Use the emulsion within an hour of preparation. 

In emulsification and entrainment, the crude oil is emulsified in situ owing to IFT reduction, and it is entrained by the flowing aqueous alkaline solution (Subkow, 1942). The conditions for this mechanism to occur are high pH, low acid number, low salinity, and OAV emulsion size < pore throat diameter. 

Given any two of the four quantities SC, Aik, pH, Pcoj/ the other two can always be calculated provided appropriate equilibrium constants are available (the equilibrium constants depend on temperature, salinity, and pressure). The standard analytical technique for the carbonate species in seawater measures alkalinity and total carbon simultaneously in an acid titration. Hydrogen ion concentration can then be determined with the equation ... 

Tetrahydrate, white, odorless, cryst powder saline taste. Stable when kept cool and dry, but is dec with liberation of oxygen in warm Or moist air. Dec above 60. Sol in about 40 parts water, the soln being alkaline and dec with the liberation of HjO, and then of oxygen. In the presence of acids, Hj02 is formed. Keep welt dosed and in a cool place. 

Emirates (UAE) coast are exposed to high amounts of salinity (mainly chloride and sulfate). These two active ions are responsible for the corrosion of marine structures, especially at the tidal zones, and responsible for the corrosion of substructures on the coastal areas. Concrete protects reinforcement through its high alkalinity however, corrosion starts when this alkalinity breaks down due to penetration of acids, water, and oxygen into the proximity of the reinforcement. More research and studies should be conducted on corrosion in the UAE marine enviromnent and on methods of protection because there are many large projects and constructions both offshore and onshore along the coast line. 

The recovery of naturally acidic oils by alkaline flooding fits into the phase alteration category. The recovery mechanisms of these floods are varied since the surface active salts, which are formed by the in situ acid-base reaction, can adsorb onto the oil-water interface to promote emulsification or can absorb onto the rock surface to alter wettability. The exact recovery mechanism, recently reviewed by Johnson (3) depends on the pH and salinity of the aqueous phase, acidity of the organic phase and wettability of the rock surface (4,5). In this study an additional alkaline recovery mechanism is explored. This mechanism. Emulsification and Coalescence, depends on the valency of the electrolyte as well as the pH and salinity of the aqueous phase. The Emulsification and Coalescence mechanism for the recovery of acidic oils is similar to the Spontaneous Emulsification mechanism suggested by Schechter et al. (6) for the recovery of nonacidic oils with petroleum sulfonate solutions. 

Fourcroy at first classed acids, alkalis, and alkaline earths as sels purs or sels prinUtifs true salts (formed from alkalis and earths with acids) are called sels composis. In 1795 he reserved the name sel for true salts, combinaisons des acides ou salifians avec les bases salifiables alcalines ou terreuse. Silica and alumina are called earths terres) lime, magnesia, and baryta are saline earths substances saUno-terreuses). All salts except nitrate of ammonia are incombustible. ... 

Some typical data for iso- and iso-NPG polyester resins are given in Figure 9.9 for an alkaline, acidic and saline environment. 

On 11 December 1823, at the Royal Society, William Front presented his landmark paper On the Nature of Acid and Saline Matters Usually Existing in the Stomach of Animals ". This presentation was unique in two ways. First, Front had specifically identified hydrochloric acid in the gastric juice of many species (man, dog, rabbit, horse, calf and hare), and second, he was able to quantify the free and total hydrochloric acid and chloride present. The acid was measured by neutralization with potash solution of known strength and the chloride by titration with silver nitrate. He also proposed that chloride may be secreted from blood to lumen by electrical means and that, when gastric acid was secreted, the blood would become alkaline (now recognized as the postprandial alkaline tide). More than 100 years were to elapse before his subsequent proposal was confirmed. 

The entire carbonate balance in a sample of sea water can be evaluated from a knowledge of the total alkalinity and pH, provided we also know the dissociation constants of carbonic acid and boric acid in sea water of various salinities and temperatures. 

As will have become apparent, nickel and corrosion-resistant nickel alloys have wide ranges of application, particularly in industries where strongly acidic, strongly alkaline or strongly saline environments are encountered. Table 4.29 lists some of the more important applications in those industries where these conditions most frequently arise, i.e. in the chemical, petrochemical, oil and gas, nuclear and conventional power generating, textile, paper, marine, desalination and food processing industries. The list is by no means exhaustive and there are many other applications of a similar nature in these and other industries. The table should, nevertheless, serve... 

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