Identification and Translocation of Potentially Toxic Elements in Sorghum Plants Grown in Central Mexico

Contamination of agricultural soil by potentially toxic elements (PTEs) can be caused by volcanic emissions and the use of agrochemicals; this threatens human food security, as PTEs can be transferred from the soil to plant tissues. Sorghum is the fifth most important cereal crop worldwide, and Mexico is one of the countries with the highest sorghum production. However, these crops are vulnerable to pests; thus, agrochemicals are applied to eliminate them. In this study, the identification and translocation of PTEs into sorghum plants grown in urban and volcanic areas of central Mexico were evaluated. Sorghum plants and soil samples were collected at four sites (S1, S2, S3, and S4) in these areas. The concentrations of PTEs in the soil samples and in the different tissues of the sorghum plants were determined by inductively coupled plasma optical emission spectroscopy. It was found that these sites are contaminated with PTEs, which were attributed to volcanic emissions and anthropogenic activities. In addition, the translocation factor values for zinc, nickel, and manganese showed that these PTEs were retained in the roots of the sorghum plants; however, the average concentrations of these PTEs in the grains of the plants were higher than the translocation factor values. This result indicates that the aerial parts of the sorghum plants could have been contaminated with PTEs from the air, which could then enter humans throughout the food chain.