ABSTRACT
This chapter collates the evidence for fixation of cadmium (Cd) and zinc (Zn) and discusses the relevance of fixation reactions in the risk assessment of these elements in soil.
After a trace element is added to soil, several reactions may occur, which change its concentration in the soil-pore water and the fraction available to organisms. Immobilization reactions in soil have a characteristic initial fast reaction (minutes to hours), which is then followed by a slow reaction (days to years). The slow immobilization reaction removes the trace element from the pool that is in dynamic equilibrium with the soil solution to a pool from which desorption may be very slow, if detectable at all within a realistic time frame (Figure 9.1). This slow immobilization reaction gradually reduces the availability of trace elements with increased aging time in soil and is hereafter termed “fixation
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