HEAVY-METALS IN SOILS AND ALFALFA (MEDICAGO-SATIVA L) IRRIGATED WITH 3 SOURCES OF WASTE-WATER

A field study was carried out to examine the concentrations of heavy metals (Cd, Co, Cr, Cu, Pb, Ni, Mn and Zn) in Medicago sativa L. irrigated with three sources of wastewater (high, medium and low levels of contaminants) in Irrigation District 03, located in the state of Hidalgo, Mexico. The concentrations of Pb (13 mg/kg) and Cd (4 mg/kg) in soil irrigated with wastewater with a high level of contaminants were twice as high as in the soil irrigated with wastewater with a medium level of contaminants. Only a trace of Cd and Pb, and 0.35 mg/kg of Cr were found in leaves of M. sativa grown on soil irrigated with well water (not contaminated); in plants grown on soil irrigated with wastewater the ranges in concentrations of Cd, Pb and Cr were 1.8 to 4.0; 4.5 to 21.5 and 0.35 to 6.0 mg/kg respectively.