Estuary seawater

Estuary seawater Estuary of Tinto and Odiel Rivers, Spain 31... 

HCOJ, COg, CO2, and Dissolved Inorganic Carbon in the Changjiang River Estuary Seawaters... 

Diluted estuary seawater is generally more aggressive to materials than that of the open sea. This paradox can be explained in several ways precipitation of calcium and magnesium carbonates does not occur in diluted seawater, biological activity is slowed down, and domestic or industrial effiuents can modify the physicochemical equilibria and possibly themselves cause corrosive action. 

The tabulation of published data on the concentration of rare earth elements and the Nd isotopic composition of natural waters is published separately in a Woods Hole Oceanographic Institution (WHOI) Technical Report (Sholkovitz 1996). In this Handbook article these data tables will be referred to as tables A1 through A14. These A tables include data for rivers, estuaries, seawater, enclosed basins, anoxic basins, pore waters and hydrothermal waters. The tabulated data are also contained on Microsoft Excel files included on a disk as part of the Technical Report. Readers can receive a copy of the Technical Report by writing to the following address ... 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Honeyman and Santschi 1989). Therefore, flocculation of colloids to form settling particles in estuaries is an important mechanism for trace element removal (Sholkovitz 1977). This is particularly true of Fe, which is a ubiquitous colloidal species and is removed at low salinities. Additional removal may occur by adsorption onto floes, as demonstrated by mixing of organic-rich waters with seawater in the laboratory (Sholkovitz 1977). 

Chlorinated waters are being discharged to estuaries and coastal waters in increasing quantities. In such systems the chlorine reacts with the natural bromide and ammonia at pH 8 to produce the highly toxic hypobromous acid, hypobromite ion, and haloamines. For normal seawater of pH 8, the initial products of chlorination are a mixture of hypobromous acid and the hypobromite ion. Both of these compounds are unstable with respect to decomposition and disproportionation. 

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

Very limited work has been published on the determination of anions in estuary and coastal waters. However, there is no doubt that the open seawater analysis methods discussed in Chap. 2 would in many instances be applicable to estuary and coastal waters. 

To overcome the suppression effect of amines in the determination of ammonia, Hampson [56] investigated the effect of nitrite ions added either as nitrite or as nitrous acid. Figure 5.2 indicates that very considerable suppression by nitrite does occur, although it is not as strong as with any of the amines. Again, it is not great so long as the nitrite N concentration is less than the ammonia N concentration, but rapidly increases as the nitrite concentration exceeds the ammonia concentration. In fact, the nitrite modified method was found to be satisfactory in open seawater samples and polluted estuary waters. 

The determination of ammonia in non-saline waters does not present any analytical problems and, as seen above, reliable methods are now available for the determination of ammonia in seawaters. In the case of estuarine waters, however, new problems present themselves. This is because the chloride content of such waters can vary over a wide range from almost nil in rivers entering the estuary to about 18 g/1 in the edges of the estuary where the water is virtually pure seawater. 

Figure 6.2. (a) The effects of salinity on the sensitivity of standard additions of ammonia in laboratory mixed waters ( ) and in waters from the Tamar estuary (A) expressed as percentage of response in river water. For comparison, the salt error curves reported by Loder and Gilbert [3] are also shown (... and —, respectively), (b) Contribution of reactive index and organic absorbance to the optical blacks in the Chemlab Colorimeter. = River water-seawater mixture, o = De-ionized water-seawater mixture. Source [2]... 

Adsorption on XAD-2 and XAD-4 resins followed by solvent desorption and head space GS has been employed for the preconcentration and determination of volatile organosulfur compounds in estuary and seawater [330]. 

Estuarine fungi contribute substantially to plant detritus due to their abundance and potential for degradation. Fungi are known to accumulate soluble atrazine from seawater through sorption, and release up to 2.2% as hydroxyatrazine and other atrazine metabolites another 4.6% is more tightly associated and less available to the external environment. The combined processes result in atrazine accumulation, and may contribute to its transport and redistribution through the estuary (Schocken and Speedie 1982, 1984). 

In seawater the thickness" of the double layer as given by k1 (Eq. 3.9) is a few Angstroms, equal approximately to a hydrated ion. In other words, the double layer is compressed and hydrophobic colloids, unless stabilized by specific adsorption or by polymers, should coagulate. Some of this coagulation is observed in the estuaries where river water becomes progressively enriched with electrolytes (Fig. 7.14a). That these colloids exist in seawater for reasonable time periods is caused... 

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