Impact of Treated Wastewater Use on Heavy Metal Accumulation in Soils and Sudan Grass Crops in the Mexicali Valley

This study investigated the impact of using treated wastewater on the accumulation of heavy metals in soils and sudan grass crops. The transfer rate of heavy metals from soil to Sudan grass was determined. The Sudan crop was established in two plots: one irrigated with fresh water from the Colorado River and the other with treated wastewater from the Las Arenitas treatment plant. Metals Pb, Cr, Cd, Ni, and Cu were evaluated at two soil depths. Results showed that the concentration of metals in the treated wastewater is higher than in freshwater but within permissible limits. At a depth of 0-30 cm, the concentrations (mg/kg) of Pb, Cr, Cd, Ni, and Cu in soils irrigated with fresh and treated wastewater were 24.59, 19.25, 0.61, 25.33, 26.70, and 31.78, 20.10, 28.31, 28.33, respectively. These values show significant differences in the concentration of Pb and Cd. Analysis of metals in the Sudan grass showed similar results for soils irrigated with both types of water, with Pb and Cd not detected. The transfer rate was less than one for all metals. These results indicate no contamination or toxicity risks when using treated wastewater in Sudan grass crops. However, continuous monitoring is necessary to prevent contamination risks. These findings provide a scientific basis for developing policies and strategies for sustainable water resource management in arid and semi-arid regions.