Prx

where:

K = adsorption or distribution coefficient Cs = concentration adsorbed on soil surfaces (ug/g of soil)

Cw = concentration in water (ug/ml)

Table 9.12.6 lists the adsorption coefficients for several metals. The greater the coefficient Kd, the greater the extent of adsorption. Furthermore, changes in metal concentration, as well as pH, can have a significant effect on the extent of adsorption as shown in Figure 9.12.2.

A negative adsorption occurs when anions (negatively charged metal ions) are repulsed by negative soil particle charges. This repulsion causes high mobility and migration of anions in water. This process is also known as anion exclusion.

—Ahmed Hamidi

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