Heavy metal accumulation in plants and soil irrigated with wastewater from Mexico city

Analysis by PIXE has been successfully employed in the study of environmental samples since it is possible to detect in a simple and fast way a high number of elements (heavier than Na) with a high sensitivity. In this work the PIXE method has been applied to study the extent of heavy metal contamination in soils and plants from Mixquiahuala, Hidalgo and Tlahuac, D.F. These two agricultural sites have been irrigated with wastewater from Mexico City for more than 50 years. The use of wastewater increased the crop productivity; however, in the areas irrigated for long periods of time, deterioration is now observed and only certain plant species can be grown. In this work, we present the range of variation that was observed for metals such as Fe, Cr, Co, Mn, Ni, Cu, Zn and Pb. Some of these elements were found at concentrations above the potentially hazardous levels in soils; however, they accumulated in plants to a lower extent, probably because of the physical and chemical properties of soils that prevent their translocation to plants. (C) 2004 Elsevier B.V. All rights reserved.