Mobilization of heavy metals from contaminated calcareous soils by plant born, microbial and synthetic chelators and their uptake by wheat plants

Extractability of heavy metals (Zn, Ni, and Cd) from a contaminated soil by plant born (phytosiderophores), microbial (desferal) and synthetic chelators (DTPA) has been studied. For this purpose a highly calcareous soil was contaminated by amendments of sewage sludge Dr a mixture of inorganic Zn, Ni and Cd salts at two different rates during a one month incubation period. After that the contaminated soils were extracted by the following extractants: ammonium nitrate, pH 6.4 (AN); DTPA, pH 7.3; ammonium bicarbonate + DTPA, pH 7.6 (AB-DTPA); desferal, pH 7.3 (DES); and phytosiderophores from wheat, pH 7.3 (PS). In addition, a short term uptake study with wheat seedlings of different Fe nutritional status (preculture +/-Fe in nutrient solution). Heavy metal contaminated soil was supplied in dialysis tubes for 48 h in this experiment. The results clearly indicate that PS and DES are the most efficient and AN the least efficient extractant for Fe, Zn, Ni acid Cd. The high mobilization potential of FS was also expressed in a distinct higher uptake (up to factor 5) of heavy metals from contaminated soils in dialysis tubes by Fe deficient wheat seedlings compared with +Fe precultured control plants.