Black water rivers

Phenolics are responsible for the coloration of black-water rivers, particularly in the tropics. An example is the Rio Negro, which remains distinct in its black color for many miles as it flows into the milky brown Amazon. In and near such black rivers, fauna and flora are considered impoverished (Swain, 1979). 

Black C, produced by wild fires and humic substances (HS), the natural by products of SOM decomposition in soil and water systems, are certainly the classes of organic compounds that most closely approximate this recalcitrant behavior. HS occur widely, being found in large amounts not only in the soil and sediments but also in lakes, rivers, ground waters, and even the open ocean (Stevenson, 1994). Besides these relatively refractory substances, more labile compounds can persist in soil for a much longer time than would be predicted from their inherent recalcitrance to decomposition. SOM stabilization (Figure 5.2) is generally considered to occur by three main mechanisms (i) physical protection, (ii) chemical stabilization, and (iii) biochemical stabilization (Six et al., 2002). 

The mixing zone of river fresh water with salinity less than 0.5%o and sea brackish water with salinity up to 18%> occupies a bend up to 20-30 km in width during high-flow period and western winds and of 3-5 km during the low-flow period and eastern winds [7,30]. The Danube water spreads mainly on the surface with layer from 1-3 to 5 m [9]. The Danube River water runoff and its distribution between delta branches play a very important role not only in hydrological and hydrochemical regime of the delta and mouth nearshore zone but also in formation of ecological conditions in the northwestern part of the Black Sea as a whole [7,9,30]. 

Observations show that the area of hypoxia directly depends on volume of the Danube water runoff during spring-summer flood. Besides, this area depends on the time of the flood peak [9,31]. If the flood peak takes place in April, the river fresh waters are driven out of the northwestern part of the Black Sea in the south direction under the influence of predominated northern winds in this time, and hypoxia is absent. Other situation takes place if the flood peak falls on May or June, when under the impact of the southern winds, main mass of river fresh water remains in the northwestern part of the Black Sea. In this case, hypoxia forms later and in the area between the Danube and Dniester mouths [9,31]. 

Most limnological studies have been completed near the confluence of the Solimoes and Negro rivers, which combine at Manaus to form the Amazon River. These rivers are biogeochemically distinct systems. The Solimoes River, called a whitewater river, is rich in dissolved nutrients and suspended sediments and has extensive, fertile flood-plains. The Negro River is nutrient poor and contains high concentrations of dissolved organic carbon, hence it is called a black-water river. 

At low pH (ca. 3-5), H2O2 can be consumed through iron cycles associated with the oxidation of fulvic acids involving the photo-Fenton reaction (reaction 8) [84]. As previously discussed, reactions (8) and (9) may be important in humic-rich natural waters at low pH such as in black-water rivers of the southeastern United States (e.g., Suwanee River, GA), but their importance in marine waters at higher pH (typically ca. pH 8.2) is unlikely except for some organic rich coastal environments (vide supra). 

Acidic waters formed supposedly by the spontaneous oxidation of metal sulfides with oxygen flowed (and still flow) from mines into nearby lakes and rivers. The sediments of these waters rapidly turn the lakes and rivers black. In some cases, this phenomenon has affected the geographical names, e.g., the Rio Tinto (Black River) in Spain flows near a zinc mine exploited since Roman times (Rossi, 1990 Salley et al.,... 

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]... 

Ludwig W, Dumont E, Meybeck M, Heussner S (2009) River discharges of water and nutrients to the Mediterranean and Black Sea major drivers for ecosystem changes during past and future decades Prog Oceanogr 80(3—4) 199—217... 

The main-laying systems are most diverse, - underground, overground, underwater, and water-surface ones. Many of them pass near towns and villages, cross the beds of small and big rivers, including the Dnepr, approach the Black Sea coast. 

The interactions of POCs with oil-products and synthetic surfactants in river and marine waters are considered, as well as secondary contamination of waters by POCs from bottom sediments. The black box principle was applied to estimating the ecological risk of toxic compounds contamination. 

TLC separation of the components of black dye commercial product (BDCP) was performed on silica layers. The chemical structures of the dye components are shown in Fig. 3.17. Dyes were extracted from the effluent of the dye processing plant, from the untreated river water and from the drinking water treatment plant. The organic extracts were further concentrated and purified using a copolymer of styrene divinyl benzene. The mobile phase for TLC separation consisted of toluene-ethyl acetate (8 1, v/v). The Rp values of dye components were 0.43 (C. I. Disperse Violet 93), 0.48 (C. I. Disperse Orange 37) and 0.59 (C. I. Disperse Blue 373), respectively. 

Analysis of small ions has been published for many applications other than pharmaceutical applications, and has a growing impact in industrial, environmental, biomedical, clinical, and forensic laboratories. Sample matrices range from simple tap water to Kraft black liquor, including river and seawater, beer and wine, environmental water, and nuclear plant water, but also body fluids such as serum, urine, plasma, cerebrospinal fluid, and many others. Those topics alone would require a separate book. 

Clay may even benefit fish. Swain (1979) found that raising the levels of tannic acid in the water caused increasing discomfort and death to guppies (Fig. 11.29). The addition of clay to the water (52mg/ml water for a tannic acid concentration of 35 amol/l) extended the period the guppies survived over six times. Suspended clay particles in white rivers may adsorb phenolics and protect fish that cannot easily live in phenolic-rich black rivers (Swain, 1979). 

Correlation of Structure with Source. Allochthonous-derived DOM (8) was isolated from the Suwannee River at its origin in the Okefe-nokee Swamp in southern Georgia. The fiilvic acid fraction, which is responsible for the black coloration of the water, was extensively characterized (9). Several average molecular models based on quantitative analytical data were presented in that report (10) to denote the mixture characteristics of fiilvic acid. One model, modified to depict biochemical sources and based on quantitative analytical data (10), is presented in Structure 1. Other models of Suwannee River fulvic acid (based on lignins, terpenoids, tannins, and flavonoid sources) were previously proposed (II). 

After this it was perceived, either the river was little shrunk, or that the tombs receded further from it. But this doubt is soon cleared, because even vulgar eyes do judge that waters are sensibly diminished every day. As they decrease the competitors removing ever anon their tents press forward on the bank and follow them retiring. The less the river, is the nearer they approach, the nearer that they are, the more they seem alike. For as much as the black exhalations of Cocytus do tan the lovely fairness of the Queen, so much the Northern Winds add beauty to the King so that they who were before so much unalike, have now so much resemblance, that they are scarce distinguished from one another. 

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