ABSTRACT
Evaluation Methods and Techniques for the Immobilization of Heavy Metals in Phosphate-Amended Soils ............................................................... 204
Heavy Metal Speciation Methods ................................................................ 205 Extraction Procedures of Chemical Speciation of Heavy Metals in Soils ............................................................................................ 205 Chemical Modeling of Metal Speciation in Soil Solutions .................. 205 Spectroscopic and Microscopic Techniques ........................................... 206
Methods for Assessing Metal Phytoavailability/Toxicity and Mobility .... 206 Immobilization Mechanisms of Heavy Metals in PhosphateAmended Soils ..................................................................................................... 207
Phosphate-Induced Adsorption of Metal Ions ........................................... 208 Metal Phosphate Precipitates or Minerals .................................................. 208 Adsorption or Complexation of Metals on Phosphate Surfaces ............. 209
Effects of Different Phosphate Materials on the Mobility and Availability of Heavy Metals in Soils ............................................................... 211
Immobilization Effectiveness of Different Phosphate Materials ............. 211 Mobility and Phytoavailability of the Most Common Heavy Metals in Phosphate-Amended Soils ....................................................................... 218
Pb ................................................................................................................. 218 Cd ................................................................................................................. 219 Cu and Zn ................................................................................................... 220 As ................................................................................................................. 221
Environmental Risks of the Immobilization of Heavy Metals in Phosphate-Amended Soils ................................................................................. 221
Accumulation of Heavy Metals in Soils ...................................................... 221 P Leaching, Nutrition Imbalance, and Soil Acidication in Phosphate-Amended Soils ............................................................................222
Conclusions ..........................................................................................................225 References ............................................................................................................. 226
The pollution sources of heavy metals in soils are mainly derived from anthropogenic activities associated with atmospheric pollution from motor vehicles, combustion of fossil fuels, agricultural fertilizers and pesticides, organic manures, disposal of urban and industrial wastes, metallurgical industries, and mining and smelting of nonferrous metals (Alloway 1990). During the last three decades, heavy metal pollution in China’s agricultural soils has become a serious situation due to highly intensive cultivation and rapid industrialization and urbanization. As a result, about 20 million ha of cultivated land (20% of the country’s arable land) has been polluted (Chen 1996), bringing serious threats to the ecosystem and public health. Recently, an occurrence of Cd toxicity in rice caused widespread public concern and anxiety, highlighting China’s dependence on food derived from contaminated soils (Bi et al. 2013; Liu et al. 2013).
