The role of soil and plant metabolic processes in controlling trace element behavior and bioavailability to animals.

Metabolic and physiological processes play important roles in regulating the transfer and behavior of trace elements in the soil/plant/animal system. The behaviors of Ni, Cd, Cr, T1, Np, Pu and Tc are used to illustrate important aspects of these processes. Microbial metabolism has both indirect and direct effects on trace element solubility in soils. Once non-nutrient trace elements are solubilized, the ability of plant roots to actively accumulate them is dependent on chemical activity of the element in soil solution, the presence of competing ions and the redox potential and absorption capacity of the root. After absorption in the plant, trace elements are translocated, metabolized and stored; fate and behavior varies with the properties of the element, but is generally analogous to nutrient elements. These processes can dramatically affect the availability of individual elements to animals consuming plants.