INORGANIC AND ORGANIC SOIL AMENDMENTS USED FOR THE IMMOBILIZATION OF CADMIUM IN CONTAMINATED SOILS - Management of Hazardous Residues Containing Cd - page 100

1. I NTRODUCTION
Soil contamination with potentially toxic elements (PTE) is a worldwide
problem. Excessive accumulation of PTE in agricultural soils may not only
result in environmental contamination, but also lead to elevated PTE uptake by
crops, which may affect food quality and safety (McLaughlin and Singh 1999;
Zhu et al, 2008). Among PTE, cadmium (Cd) and lead (Pb) have been
recognized as priority pollutants by the United States Environmental
Protection Agency (USEPA) and other organizations. Cadmium may easily
reach the food chain through common agricultural practices such as
fertilization, irrigation or pesticide application (Meeüs et al., 2002). Other
anthropogenic activities primarily associated with industrial processes,
atmospheric fallouts, manufacturing and the disposal of domestic and
industrial waste materials may also result in a significant input of soil Cd.
The Pampas Region, Argentina, is one of the largest temperate field
cropland areas of the Southern Hemisphere. At present, the concentrations and
dispersion values of PTE in agricultural or grazed soils in this region are
similar to other non-contaminated soils of the world (Lavado et al., 2004).
However, these soils recently started to receive an increased amount of
phosphate fertilizers. Depending on its provenance, Cd in the phosphate rock
can be present in relatively large amounts, from 0 to 150 mg Cd kg −1 (López
Camelo et al, 1997). Hence, there is an increasing local concern for protecting
the environmental quality of croplands of the Pampas Region.
In contrast to agricultural soils, some urban areas of Argentina and its
surroundings are starting to show signs of anthropogenic accumulation of Cd
and other PTE (Wannaz et al, 2006; Lavado, 2006). Anthropogenic sources of
cadmium for urban and peri-urban areas include traffic emission (vehicle
exhaust particles, tire wear particles, brake lining wear particles), industrial
emission (power plants, coal combustion, metallurgical industry, chemical
plants, etc.), domestic emission, weathering of building and pavement surface,
atmospheric deposition and so on (Sindern et al, 2007; Christoforidis, Stamatis
2009; Lu et al, 2009; Morton-Bermea et al, 2009; Wei, Yang 2010). Some
alluvial soils of the Riachuelo River in Buenos Aires province were also
reported to accumulate between 1-5 mg Cd kg -1 due to anthropogenic activity
(Ratto et al, 2004). High concentration of Cd in sediments may lead to Cd
release to water and pose risk to aqueous organisms and human health. Lavado
et al. (1998) reported that concentrations of Cd and other PTE in some urban
and peri-urban soils of Buenos Aires province, were much higher than
thresholds proposed by several international standards and by the Argentine