Lakes particle stability

TABLE 5. Experimental Particle Stability Factors in Lakes... 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

Experimental measurements in each lake included particle concentration and size measurements in the water column, sedimentation fluxes in sediment traps, and chemical and size characteristics of materials recovered from sediment traps. The colloidal stability of the particles in the lake waters was determined with laboratory coagulation tests. Colloidal stability was described by the stability ratio (a). For a perfectly stable suspension, a = 0 for a complete unstable one, a = 1.)... 

Model simulations of particle volume concentrations in the summer as functions of the particle production flux in the epilimnion of Lake Zurich, adapted from Weilenmann, O Melia and Stumm (1989). Predictions are made for the epilimnion (A) and the hypolimnion (B). Simulations are made for input particle size distributions ranging from 0.3 to 30 pm described by a power law with an exponent of p. For p = 3, the particle size distribution of inputs peaks at the largest size, i.e., 30 pm. For p = 4, an equal mass or volume input of particles is in every logaritmic size interval. Two particle or aggregate densities (pp) are considered, and a colloidal stability factor (a) of 0.1 us used. The broken line in (A) denotes predicted particle concentrations in the epilimnion when particles are removed from the lake only in the river outflow. Shaded areas show input fluxes based on the collections of total suspendet solids in sediment traps and the composition of the collected solids. 

Figure 5.2 illustrates the effect of various stabilizers on the slurry sedimentation time after stopping US application in the determination of lead from lake sediments in particle sizes < 2 mm [26], The presence of nitric acid has the twofold effect of stabilizing slurries and increasing analyte leaching. The latter effect is a function of both the acid concentration and the nature of the target analyte [10]. 

Some of the physical characteristics listed for lakes in the literature include particle size distribution, moisture content, oil absorption, bulk density, specific gravity, and pH stability. These properties may or may not be of interest, depending on the user s application. 

The observation of Weilenmann et al. (1989) (see Figure 14.6) on some Swiss hard water lakes shows that two important factors affecting the stability of particles in lakes are (1) [Ca 1 and (2) organic matter (like humic substances). Ca destabilizes and organic matter stabilizes colloidal particles in lakes. 

Tipping E., Ohnstad M. (1984b), Colloid stability of iron oxide particles from a freshwater lake. Nature, 308, 266-268. 

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