Solid-phase component

For the case, where the soluble component is leaching from an inert solid carrier, a separate solid phase component balance would be required to establish the solute concentration in the solid phase and hence the time dependent value of the equilibrium concentration. Cl. ... 

Most primary and secondary minerals found in soil systems are barely soluble in the soil solution. The amount of mass from the bulk phase to hydrated ions in soil solution is negligible compared to the total mass of the solid phase. In arid and semi-arid soils, concentrations of most trace metals in soil solution may be controlled by their carbonates and to some extent by their hydroxides. Other than carbonates, trace elements in arid and semi-arid soils may also occur as sulfate, phosphate or siliceous compounds, or as a minor component adsorbed on the surface of various solid phase components. The solubility of carbonates, sulfates and other common minerals of trace elements in arid and semi-arid soils will be discussed in Chapter 5. Badawy et al. (2002) reported that in near neutral and alkaline soils representative of alluvial, desertic and calcareous soils of Egypt, the measured Pb2+ activities were undersaturated with regard to the solubility of... 

There are a number of selective sequential dissolution procedures which have been developed for specific elements, matrices, regional soils, and specific purposes (Table 4.1). Additionally, various extractants are used in different sequential procedures for the similar targeted solid-phase component. The review on the extractants of individual fractions of metals in soil was made by Shuman (1991). However, in most protocols the trace elements/heavy metals in their native and waste-amended soils are divided into the following physicochemical forms ... 

The terms of the fractions are more likely to be operationally, rather than chemically, defined. However, each extractant in the sequentially selective procedure mostly targets one major solid-phase component. Therefore, trace elements bound to the targeted fraction can be either... 

The Chemical Extractants for Different Fractions in Solid-phase Components... 

Table 4.5. Extractants for trace elements bound to various solid-phase components in soils... 

BINDING AND DISTRIBUTION OF TRACE ELEMENTS AMONG SOLID-PHASE COMPONENTS IN ARID ZONE SOILS... 

Carbonates, organic matter, Fe and Mn oxides, and clay minerals play important roles in controlling overall reactivity of trace elements in soils and sediments. This chapter addresses the interaction of trace elements with carbonates, organic matter, Fe and Mn oxides and clay minerals. Analytical techniques for trace element speciation in solid-phase and their distribution among various solid-phase components in arid and semi-arid soils are reviewed. Solubilities of trace elements in solid phases and their mineralogical characteristics in arid and semi-arid soils also are discussed. 

Zinc sorbed in the untreated soil after desorption was less than that in the soil with organic matter removed (Kingery et al., 1999). This shows that the Zn maintained in the soil solid phase after desorption was proportional to Zn adsorption of the soil solid-phase. A strong hysteresis between Zn desorption and Zn adsorption curves was found in the untreated and treated soils. This indicates that some sorbed Zn is in the nonexchangeable form and on the specific adsorption sites on soil solid-phase components. 

Iron and Mn oxides are two of the most important solid-phase components controlling distribution and availability of trace elements in arid... 

Trace elements can be adsorbed on the surface of calcite, influencing their solubility in calcareous soils of arid and semi-arid zones. The carbonate bound fraction is the major solid-phase component for many trace elements (Cd, Pb, Zn, Ni and Cu) in arid and semi-arid soils, especially in newly contaminated soils (Table 5.3). In Israeli arid soils treated with metal nitrates, the carbonate bound fraction is the largest solid-phase component (60-80%, 50-60%, 40-60%, 30-40%, and 25-36% for Cd, Pb, Zn, Ni, and Cu respectively). Divalent metallic cations at low aqueous concentrations first associate with calcite via adsorption reactions. Then they may be incorporated into the calcite lattice as a co-precipitate by recrystallization (Franklin and Morse, 1983 Komicker et al., 1985 Davis et al., 1987 Zachara et al., 1988 Reeder and Prosky, 1986 Pingitore and... 

Table 5.5. Distribution of Zn among solid-phase components in some Chinese arid soils3...

Figure 5.6. Relationship between Co and Mn contents extracted from solid-phase of six Israeli arid-zone soils with sequential dissolution procedures (after Han et al., 2002b. Reprinted from J Environ Sci Health, Part A, 137, Han F.X., Banin A., Kingery W.L., Li Z.P., Pathways and kinetics of transformation of cobalt among solid-phase components in arid-zone soils, p 184, Copyright (2002), with permission from Taylor Francis)...

Following the initial fast retention, the slow redistribution of the added metals occurred over time. During one year of incubation under the field capacity regime, heavy metals were slowly transferred among solid-phase components as shown in Figs. 6.1-6.4. Added Cu and Ni were transferred from the EXC and CARB fractions into the ERO and OM fractions and Zn mainly into the ERO fraction. Chromium and Pb moved from the CARB fraction into the OM and ERO fractions, respectively. Cadmium redistributed from the EXC fraction into the CARB fraction. After one year of incubation under the field capacity regime, 65-100% of the added Cd was transferred to the CARB fraction. About 50% and 20% of the added Pb was redistributed to the CARB and ERO fractions, respectively. 

The reduced partitioning index (mean IR values) of Cd, Cr, Cu, Ni and Zn in 45 Israeli arid-zone soils is presented in Fig. 6.7. The trends for mean IR values for five heavy metals in these soils were as follows Cr > Zn = Cu > Ni > Cd (Fig. 6.7) (IR is calculated from Banin et al., 1997a). This indicates that Cr is strongly bound to solid-phase components, possessing... 

Figure 6.15. The average transfer fluxes of Cr and Cu among solid-phase components in Israeli soils. The soils received metal nitrates at the 3T level under the field capacity moisture regime (T total metal content in non-amended soils)...

The annual transfer fluxes of the four metals among solid-phase components between one day and one year of incubation at the two moisture regimes are presented in Fig. 6.18. The overall transfer fluxes of the slow processes were differentiated between the two soils and the two moisture regimes. In general, the transfer fluxes of the metal in the loessial soil was higher than that in the sandy soil because of its abundant solid-phase... 

Figure 6.18. Changes of the annual transfer fluxes (from one day to one year) among solid-phase components with metal loading levels in Israeli soils. Soils received metal nitrates and were incubated in the saturated-paste (SP) and field capacity (FC) moisture regimes...

Changes of Manganese Partitioning Among Solid-phase Components in Arid-zone Soils Pathways and Short- and Intermediate-term Kinetics... 

Pathways and Kinetics of Transformation of Cobalt Among Solid-phase Components at Saturated Arid-zone Soils... 

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