Stream beds

SO2 adsorbed on copper oxide bed forming CuSO. Bed is regenerated with H2 or H2—CO mixture giving concentrated SO2 stream. Bed is reduced to Cu, but reoxidized for SO2 adsorption. 

The elements are the simplest form of matter. An element contains only one type of atom and cannot be decomposed into other chemical components. Of the more than 100 known chemical elements, only a few are found in nature in their pure form. Figure J shows three of these Diamonds are pure carbon, nuggets of pure gold can be found by panning in the right stream bed, and sulfur is found in abundance in its elemental form. 

These acidic waters are toxic to plant and animal life, including fish and aquatic insects. Streams affected by acid drainage may be rendered nearly lifeless, their stream beds coated with unsightly yellow and red precipitates of oxy-hydroxide minerals. In some cases, the heavy metals in acid drainage threaten water supplies and irrigation projects. 

To see how this process works, we construct a model in which reaction of a hypothetical drainage water with calcite leads to the precipitation of ferric hydroxide [Fe(OH)3, which we use to represent HFO] and the sorption of dissolved species onto this phase. We assume that the precipitate remains suspended in solution with its surface in equilibrium with the changing fluid chemistry, using the surface com-plexation model described in Chapter 10. In our model, we envisage the precipitate eventually settling to the stream bed and hence removing the sorbed metals from the drainage. 

We do not concern ourselves with the precipitate that lines sediments in the stream bed, since it formed earlier while in contact with the drainage, and hence would not be expected to continue to sorb from solution. Smith et al. (1992), for example, found that in an acid drainage from Colorado (USA), sorption on the suspended solids, rather than the sediments along the stream bed, controls the dissolved metal concentrations. 

Stream beds, drainage ditches, Nova Scotia ... 

Solid samples of tailings material were collected from different depths (2 - 18 m) in drill cores. Precipitates were collected from different locations in the stream bed. Water samples were taken from a well situated in the tailings pond, at three different effluent points on the downstream face of the tailings dam, and also at 30 m as well as 50 m downstream. The physico-chemical parameters of the water were measured during sampling. 

Bradley et al. (1999) studied the degradation of tert-butyl alcohol by indigenous microorganisms in stream-bed sediments from underground gasoline spill sites in Laurens, SC (Laurens) and Charleston, SC (Oasis). Under aerobic conditions, the amount of tert-butyl alcohol mineralizing to carbon dioxide after 27 d was 70% in both Laurens and Oasis sediments. After 80 d, the amount of mineralization reached an asymptiotic level of approximately 84%. No mineralization of /erf-butyl alcohol was observed under strictly anaerobic conditions. 

Bradley, P.M., Landmeyer, J.E., and Chapelle, F.H. Aerobic mineralization of MTBE and ferf-butyl alcohol by stream-bed sediment microorganisms. Environ. Scl. TechnoL., 33(11) 1877-1879, 1999. 

Zirconium is found in small amounts widely spread throughout nature, occurring in many alluvial deposits of lake and stream beds and ocean beaches. The most important mineral is zircon, or zircon orthosilicate, ZrSi04. Other zirconium minerals are eudialite, (Na, Ca, FeleZrSieOislOH, Cl), and baddeleyite, Zr02. It also occurs in monazite sand. The abundance of zirconium in the earth s crust is estimated as 165 mg/kg. 

Pliny the Elder (A.D. 23-79) said that grains of gold were found in the stream-beds of the Tagus in Spain, the Po in Italy, the Hebrus in Thracia, the Pactolus in Asia Minor, and the Ganges in India (5). In the second century before Christ, a cupellation process was used for refining the metal, and in Pliny s time the mercury process was well known (6). 

Diamonds were found originally as loose erysials in geologically undent alluvial stream beds. Later, their host formations were found to be a basic igneous rock [kimberlite) in the Republic of South Africa Diamonds are the products of extremely high-temperature, high-pressure env ironment and tire composed of pure carbon See also Diamond. 

Upper Colorado River Basin Colorado USA 37 streambed sediment samples (8 from nonmined areas) USA Alabama northern impacted by acid mine drainage 25 sites USA Alaska Cook Inlet Basin streams 47 sites USA Black Hills Spearfish, Whitewood, and Bear Butte creeks watersheds USA (conterminous) (541 stream bed samples)... 

A special case is the sampling of small seasonal streams in Mediterranean countries, which must be sampled with extreme care. Some of the seasonal streams have had no water flow for many years, and the stream bed may be covered by fallen bank material in which grass or other plants may have grown. Since, active stream sediment must be sampled, the fallen bank material, covering the old active stream sediment, must be removed by digging before taking the sample at each subsite. The pits should be dug near to the centre of the channel. 

At each stream sediment/water sample site take two photographs, the first to show general upstream topography from the lowermost subsite and the second the nature of the stream bed at the best subsite. 

Stream bed Predominant Boulders and gravel Gravel and sand... 

Sorption of Co onto oxyhydroxides precipitated in stream beds has been shown to be virtually irreversible (9). Diffusion into the crystal lattice of iron-bear gg minerals has also been suggested (10) The slow removal of Co during the second 48-h KTOX extraction is consistent with this mechanism. 

Bottom Sediment. Bottom sediments were scooped from the upper 3-cm of the stream bed close to where the water samples were collected. A plastic scoop was used and a 2-L wide-mouth plastic bottle was used as a sample container, with a minimum quantity of water in the sediment. In the laboratory,... 

Water samples (oa 1 L) were collected by immersing clean mason jars to a depth of 1 cm in midstream. Water samples were extracted immediately with dichloromethane as described earlier. Moss samples (oa 300 g) were collected from rocks on the stream bed and packed in polyethylene bags after gently squeezing out adsorbed water. Samples were later cut into small pieces, thor-... 

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