Soil mineralogical perspective on immobilization/mobilization of heavy metals

Abstract

Knowledge on the fate and transport of heavy metals is essential for predicting the environmental impact of metal contamination on agricultural soils. This chapter presents an overview of various factors that are involved in controlling the retention and mobility of heavy metals in soils with a special reference to soil mineralogy. The bioavailability of most elements, in particular heavy metals, in soils is governed by adsorption-desorption, complexation, precipitation and ionexchange processes. The most important surfaces involved in metal adsorption in soils are active inorganic colloids such as clay minerals, oxides and hydroxides of metals, metal carbonates and phosphates and organic colloids. In addition to soil mineralogy, other important parameters controlling heavy metal retention and their distribution are soil texture, structure, pH, redox condition, cation and anion concentration, ionic strength, organic matter, microbial and root activity and climatic conditions. However, the ultimate fate of elements depends on a combination of several factors that are working together in the soil system. Finally, several remediation strategies have also been highlighted based on the fundamental principles of metal immobilization on mineral containing soil amendments.