Parámeter Series Observations Soil Cr > Ni >Pb>Cd Before apply biosolids Biosólids Cr >Pb> Ni >Cd First samples Wastewater Ni > Cr  >Pb>Cd Irrigations Forage (2003) Pb> Ni > Cd >Cr Oat and alfalfa Forage (2004) Ni >Pb> Cd >Cr Oat and alfalfa Ingested by sheep Pb> Ni > Cr >Cd 1.5 kg forage day-1 Initial sheep tissues Ni >Pb> Cd >Cr Kidney, liver, muscle Final sheep tissues Ni >Pb> Cd >Cr Kidney, liver, muscle

Table 5: Series of heavy metal concentrations for the food chain including soil treated with biosolids, wastewater, oat forage, and sheep tissues at the Juarez Valley, Mexico, 2003-2004.