Concentration in fresh water

Chemical Formation. A potential chemically mediated source of H202 would be the presence of reduced metals in oxygenated waters (15, 21, 32-34, 36-38). This pathway has never been demonstrated in fresh waters, although Miles and Brezonik (35) showed that 02 concentrations varied over 24 h in humic waters with iron present. No measurements of H202 were made, but most likely H202 was formed as the 02 was consumed. The net impact of these processes on H202 concentration in fresh waters is not likely to be important in waters rich in humic substances. However, this assumption has not been verified experimentally. 

EPA recommends a criterion continuous concentration (CCC) of 87 g/L and a criteria maximum concentration (CMC) of 750 g/L (EPA 1999). The CCC is an estimate of the highest concentration of aluminum in fresh water to which aquatic organisms can be exposed indefinitely without resulting in an unacceptable effect the CMC is the highest concentration in fresh water to which aquatic organisms can be exposed for a brief period without resulting in an unacceptable effect. 

Figure 10.18. Effect of pH on residual metal concentration in fresh waters. Dissolved zinc is plotted against pH. (a) Zinc in relatively undisturbed major rivers including the Yangtze (Chiang Jiang) and tributaries of the Amazon and Orinoco, (b) Zinc normalized to total dissolved solids for the same set of major rivers, (c) Zinc in pH-adjusted aliquots of Mississippi River water (April 1984, 103 mg liter suspended load, pH 7.7) the adjusted aliquots were allowed to equilibrate overnight before filtration and analysis. (From Shiller and Boyle, 1985.) (d) Zinc in different mountain lakes in the southern parts of the Swiss Alps. These lakes are less than 10 km apait, so that the atmospheric inputs can be considered to be uniform over this scale, but their water composition (pH) is influenced by different bedrocks in their catchments. A similar dependence on pH has also been observed for Cd and Pb but this dependence is less pronounced with Cu(II) when solute complex formation counteracts adsorption (data 1983-1992). (From Sigg et al., 1995, in press.)...

The detection limits for cobalty nickel, and lead in aqueous solution by atomic absorption are about 50 fig. per liter. Normally these elements occur at lower concentrations in fresh waters, and direct measurement by atomic absorption is not possible. A rapid, simple, accurate, and sensitive chelation-extraction method for determining lead, cobalt, and nickel is attained by chelating the metals with ammonium pyrrolidine dithiocarbamate at a pH of 2.8, extracting the metal-chelates with methyl isobutyl ketone, and aspirating the ketone layer. Results obtained by this method agreed well with results obtained by spectrographic methods. As little as 1 fig. of lead, cobalt, and nickel per liter can be detected. This is at least one order of magnitude lower than most other wet chemical procedures. 

Regulation of Trace Metal Concentrations in Fresh Water Systems Peter Baccini... 

Nitrate ions are generally derived from the oxidation of organic matter with a high protein content. Their presence may be indicative of a source of pollution, and their occurrence usually is associated with shallow groundwater sources. Concentrations in fresh water generally do not exceed 5 mg h , although in rural areas where nitrate fertilizer is applied liberally,... 

On this basis, Bowen states that only in the case of the elements, chromium, copper, lead and tin, would the mean concentration in fresh water rise significantly, while the change in concentration of all elements in ocean water would be immeasurably small. Of these four elements, copper is asserted to be potentially the most dangerous, since the dissolution of the world output of copper in the total mass of fresh water would raise its concentration above the toxic limit for some algae. Mercury must also be considered as a candidate for the distinction of being the most hazardous metal pollutant of the hydrosphere, since it is highly toxic and the amount produced annually is greater than the amount added to the ocean in fresh water (Table 40). 

A mixture of 0.10 mol of freshly distilled 3-methyl-3-chloro-l-butyne (see Chapter VIII-3, Exp. 5) and 170 ml of dry diethyl ether was cooled to -100°C and 0.10 mol of butyllithium in about 70 ml of hexane was added at this temperature in 10 min. Five minutes later 0.10 mol of dimethyl disulfide was introduced within 1 min with cooling betv/een -100 and -90°C. The cooling bath vjas subsequently removed and the temperature was allowed to rise. Above -25°C the clear light--brown solution became turbid and later a white precipitate was formed. When the temperature had reached lO C, the reaction mixture was hydrolyzed by addition of 200 ml of water. The organic layer and one ethereal extract were dried over potassium carbonate and subsequently concentrated in a water-pump vacuum (bath... 

To 75 ml of a 50 aqueous solution of KOH were added 0.25 mol of chloroform, 0.2 g of triethylbenzylammonium chloride and 0.10 mol of freshly distilled 1,2-cyclononadiene (see this chapter, Exp. 20) and the mixture was stirred vigorously for 10-12 h. Water (200 ml) was added and the products were extracted with diethyl ether. The extracts were dried over magnesium sulfate, concentrated in a water-pump vacuum and the residue was distilled through a short Vigreux column. The adduct, b.p. 80 C/0.15 mmHg, n j 1.5300, was obtained in 75% yield. 

Hove 1. The procedure described in Ref. 1 was modified. To a solution of 2.0 mol of lithium acetylide in 1.2 1 of liquid ammonia in a 4-1 round-bottomed, three-necked flask (see Fig. 2) was added 1.5 mol of freshly distilled benzaldehyde with cooling at about -45°C. After an additional 30 min finely powdered ammonium chloride (2 mol) was introduced in 15 min. The ammonia was allowed to evaporate, then water (1.1 1) was added and the product was extracted with diethyl ether. After drying over magnesium sulfate the extract was concentrated in a water-pump vacuum. High-vacuum distillation,... 

A solution of 0.10 mol of freshly distilled diethylaminopropyne in 80 ml of dry (distilled from phosphorus pentoxide) acetonitrile was cooled to 5°C and dry carbon dioxide was introduced into the vigorously agitated solution at a rate of about 0.3 1/min. The temperature rose above 20°C within a few minutes, but was kept at about 30°C by occasionally immersing the flask in a bath of ice-water. The introduction of CO2 was continued until the temperature had dropped to 25°C and the typical odour of the yneamine had disappeared completely. The yellow solution was concentrated in a water-pump vacuum. The residue, a sirupy liquid, had the theoretically required weight and consisted of reasonably pure (about 955 ) allenyl-diamide. If desired the product car be distilled (short-path distillation) in a high vacuum. It solidified upon standing at -25 C. 

A detailed review of the methods for deterrnination of low manganese concentration in water and waste is available (179). A review on the speciation of Mn in fresh waters has been reported (180). Reviews for the chemical analysis of Mn in seawater, soil and plants, and air are presented in References 181, 182, and 183, respectively. 

Phthalates in Water. Reported levels of phthalates in natural waters are, in general, low. Concentrations found in fresh waters range from nondetectable up to 10 )-lg/L. Measured concentrations (54) in Swedish rivers vary from 0.3 to 3.1 )-lg/L. The highest values are found near industrial discharge points. 

Free ionic silver readily forms soluble complexes or insoluble materials with dissolved and suspended material present in natural waters, such as sediments and sulfide ions (44). The hardness of water is sometimes used as an indicator of its complex-forming capacity. Because of the direct relationship between the availabiUty of free silver ions and adverse environmental effects, the 1980 ambient freshwater criterion for the protection of aquatic life is expressed as a function of the hardness of the water in question. The maximum recommended concentration of total recoverable silver, in fresh water is thus given by the following expression (45) in Fg/L. 

As of the 1990s, the EPA recommends that the dissolved form of silver be used as a better estimate of the bioavailable fraction and recommends using 85% of the total recoverable quantity. Thus, in fresh water at hardnesses of 50, 100, and 200 mg/L CaCO, the concentration of dissolved silver should not exceed 1.0, 3.5, and 11 Fg/L, respectively. The concentration of dissolved silver in salt water should not exceed 1.9 Fg/L (46). 

Copper has been employed as a bactericide, moUuscicide, and fungicide for a long time and is of importance in the control of schistosomiasis (see also Antiparasitic AGENTS, ANTHELMINTICS FUNGICIDES, AGRICULTURAL). Addition of copper to lake water acts as an efficient deterrent to transmittal of the disease by eliminating snails that act as hosts for the responsible parasite. Copper is commonly utilized at ca 0.1 mg/L as an algicide. In fresh water, acute toxicosis in fish is unusual if the copper concentration is below 0.025 mg/L (70) (see Poisons, economic). 

When dissolved in more saline waters, xanthan gum produces a higher apparent viscosity than the same concentration of polyacrylamide (292). Prehydration of xanthan in fresh water followed by dilution in the saline injection water has been reported to provide higher viscosity than direct polymer dissolution in the same injection water. Optical rotation and intrinsic viscosity dependence on temperature indicate xanthan exists in a more ordered conformation in brine than in fresh water (293). 

In adsorption studies from saline environments it is necessary to prepare the water-soluble polymer and peptized montmorillonite in fresh water at high concentrations and to add each to a saline solution. Polyelectrolytes will frequently not "yield" the same viscosity as when they are dissolved in fresh water. Montmorillonite will flocculate in saline solutions. With fresh water mixing of components, reproducible results are obtained in the saline studies. After component mixing, agitation of the slurry is maintained with gentle stirring via... 

Van den Berg [131] used this technique to determine nanomolar levels of nitrate in seawater. Samples of seawater from the Menai Straits were filtered and nitrite present reacted with sulfanilamide and naphthyl-amine at pH 2.5. The pH was then adjusted to 8.4 with borate buffer, the solution de-aerated, and then subjected to absorptive cathodic stripping voltammetry. The concentration of dye was linearly related to the height of the reduction peak in the range 0.3-200 nM nitrate. The optimal concentrations of sulfanilamide and naphthyl-amine were 2 mM and 0.1 mM, respectively, at pH 2.5. The standard deviation of a determination of 4 nM nitrite was 2%. The detection was 0.3 nM for an adsorption time of 60 sec. The sensitivity of the method in seawater was the same as in fresh water. 

The older methods for the measurement of protein in natural waters usually depended upon the presence of aromatic amino acids in the protein, and calculated total protein on the basis of an average tyrosine, tryptophan, or phenylalanine content. A method representative of this type was the Folin reagent method published by Debeika et al. [281]. While these methods were useful in fresh water and in some coastal regions, they were not sensitive enough for the lower concentrations to be found in oceanic waters. 

A spectrophotometric method based on the light absorption of the coloured Co111 complexes has been used to determine EDTA and NTA in fresh water [424]. In these few cases, actual well-defined compounds were present at concentrations high enough so that the individual compound could be isolated, identified, and measured. This is seldom the case for the chelators in seawater we are usually measuring an attribute, not a compound, with little idea of the actual identity of the compounds. 

Studies by Braman and Tompkins [98] have shown that nonvolatile methyltin species Me Sniq + (n = 1-3), are ubiquitous at ng/1 concentrations in natural waters including both marine and fresh water sources. Their work, however, failed to establish whether tetramethyltin was present in natural waters because of the inability of the methods used to trap this compound effectively during the... 

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