Continental waters acidic

Continental water contains dissolved species that render it acidic. The acidity comes from a variety of sources from the dissociation of atmospheric C02 in rainwater—and particularly from dissociation of soil-zone C02 (Section 4.4.2)— to form H2C(and natural and anthropogenic sulphur dioxide (S02) to form H2S03 and H2S04 (see Boxes 3.7 3.8). Reaction between a mineral and acidic weathering agents is usually called acid hydrolysis. The weathering of CaCO, demonstrates the chemical principle involved ... 

This shows that at typical pH values for continental waters the HCOf anion is 200 times more abundant than the CO( anion. Repeating this exercise for a range of pH values results in the graphical relationship shown in Fig. 5.5. Note that when pH falls below 5 on Fig. 5.5, almost all of the weak acid anions (HCO, and C03 ) have disappeared and at pH of 4 only undissociated acid (H2C03) remains. This relationship is used as the basis for measuring alkalinity (Box 5.2). 

This process is currentiy used by Vista Chemical, successor to Continental Oil Company s chemical business, and by Condea. In the Ethyl Corporation process dilute sulfuric acid is used in place of water in the hydrolysis step producing alum rather than alumina. 

Traditionally, butter was made by allowing cream to separate from the milk by standing the milk in shallow pans. The cream is then churned to produce a water in oil emulsion. Typically butter contains 15% of water. Butter is normally made either sweet cream or lactic, also known as cultured, and with or without added salt. Lactic butter is made by adding a culture, usually a mixture of Streptococcus cremoris, S. diacetylactis and Betacoccus cremoris. The culture produces lactic acid as well as various flavouring compounds, e.g. diacetyl, which is commonly present at around 3 ppm. As well as any flavour effect the lactic acid inhibits any undesirable microbiological activity in the aqueous phase of the butter. Sweet cream butter has no such culture added but 1.5 to 3% of salt is normally added. This inhibits microbiological problems by reducing the water activity of the aqueous phase. It is perfectly possible to make salted lactic butter or unsalted sweet cream butter if required. In the UK most butter is sweet cream while in continental Europe most butter is lactic. 

Pontanen and Morris [8] compared the structure of humic acids from marine sediments and degraded diatoms by infrared and C13 and proton NMR spectroscopy. Samples of marine sediments taken from the Peru continental shelf were extracted with water, sodium hydroxide (0.05mol 1 J) and sodium pyrophosphate (0.05mol l-1) under an atmosphere of nitrogen and fractionated by ultrafiltration. Humic acids of molecular weight 300000 and above were examined. Diatoms were collected from... 

Mitchell, North Carolina, Air Waste, 43, 1074-1083 (1993). Arakaki, T., C. Anastasio, P. G. Shu, and B. C. Faust, Aqueous-Phase Photoproduction of Hydrogen Peroxide in Authentic Cloud Waters Wavelength Dependence, and the Effects of Filtration and Freeze-Thaw Cycles, Atmos. Environ., 29, 1697-1703 (1995). Arakaki, T., and B. C. Faust, Sources, Sinks, and Mechanisms of Hydroxyl Radical ( OH) Photoproduction and Consumption in Authentic Acidic Continental Cloud Waters from Whiteface Mountain, New York The Role of the Fe(r) (r = II, III) Photochemical Cycle, . /. Geophys. Res., 103, 3487-3504 (1998). Atkinson, R., D. L. Baulch, R. A. Cox, R. F. Hampson, Jr., J. A. Kerr, M. J. Rossi, and J. Troe, Evaluated Kinetic and Photochemical... 

Except for much greater Cl accumulation in soils of arid regions, the soil chemistry of I and Br resembles that of Cl, except that I and Br are retained more strongly, especially by acid soils. The major input of I to soils appears to be atmospheric. Endemic iodine deficiency (goiter in humans) occurs in mountainous and continental areas isolated from the sea. Fortunately, supplementing NaCl with small amounts of I effectively supplies the I required in animal diets. Iodide and Br are both potentially toxic, but no natural cases have been reported. Bromide reactions in soils have been investigated as a tracer for die movement of water, nitrate, and soil solutions in soils. 

Thus, fulvic acids may originate from continental plants, and when carried by rivers and streams to the reservoirs, seas and oceans, they constitute the major part of the allochthonous water humus. Kalle (1966) suggested they were only partly responsible for the yellow substance (Gelbstoffe) present in oceanic waters, the concentration of which in the water decreases with the increase of salinity. He considered that a part of the yellow substance was of autochthonous origin. It seems probable, that its existence in water is due to transformed products of excretion of dissolved and thinly dispersed OM which was discovered in littoral algae during studies conducted by Khailov (1962), Sieburth and Jensen (1969) and Sieburth (1969). 

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