Heavy metals in rivers

Speciation of Heavy Metals in River Water Investigated by Chemometric Methods... 

Factor Analysis of the Total Concentrations of Heavy Metals in River Sediments... 

REGULATION OF DISSOLVED HEAVY METALS IN RIVERS, LAKES, AND OCEANS... 

Regulation of Dissolved Heavy Metals in Rivers, Lakes, and Oceans 655... 

The role of settling particles in regulating the concentrations of heavy metals in rivers, lakes, and oceans has been discussed in Chapter 10. 

Salomons, W., Eysink, W., In "Biogeochemical and Hydrodynamic Processes Affecting Heavy Metals in Rivers, Lakes and Estuaries". Delft Hydraulics Laboratory Publication No. 253 Delft 1981, The Netherlands. 

Whitton, B. A., Use of plants to monitor heavy metals in rivers. In Biomonitoring of Environmental Pollution, Yasuno, M. and Whitton, B. A., Eds., Tokai University Press, Tokyo, 1988. 

Table 4 indicates that Fe was mostly extracted after the third (average extraction in all samples 44%), fifth (avg. 32%) and second phase (avg. 24%) of sequential extraction. These results conclude that Fe is mostly present in the form of hydroxides [82], and that it seems to be the main substrate for heavy metals in river sediment samples. Because the second phase is abundant (average 24%), it means that beside iron s hydro- and crystalline-oxides, there are fractions of soluble amorphous iron hydroxides. A decrease of redox-potential will first dissolve the most soluble amorphous hydroxides and than less soluble hydro- and crystalline-oxides of iron, and dissolution of all forms of hydroxides is followed by release of heavy metals to the environment. 

From Figure 10 it is evident that there are good correlations between Mn and Mg extracted after the first phase of sequential extraction (most soluble fraction) and Mg extracted after the second phase. These results indicate binding of soluble Mn and Mg with magnesium in the form of Mg-carbonates. These correlations are in corroboration with another section of Fig. 10, the correlation between Mn and Mg, both extracted after the second phase. This correlation indicates interactions between Mg-carbonates and Mn-hydroxides, the two main substrates for heavy metals in river sediment samples. This means that a slight decrease of pH value and ionic strength will release heavy metals associated with both Mg-carbonate and Mn-hydroxide substrates. 

E. Munoz, S. Palmero, M.A. Garcfa-Garcfa, A continuous flow system design for simultaneous determination of heavy metals in river water samples, Talanta 57 (2002) 985—992. 

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