Accumulation of lead and associated metals (Cu and Zn) at different growth stages of soybean crops in lead-contaminated soils: food security and crop quality implications

The Pb, Cu and Zn content, the physicochemical parameters in soils (EC, OM%, soil texture and pH) and the metal accumulation of Glycine max plants at different growth stages were evaluated. Topsoil and soybean samples were collected in the vicinity of a former battery-recycling plant, with the results showing that only the concentrations of Pb in soils corresponding to sites located near to the lead emission source were above the maximum permissible levels. However, soybean crops accumulated Pb above the permitted levels at all studied sites, revealing a potential toxicological risk for direct consumption. Thus, the accumulation of Pb in soybean was directly related to the translocation factor of the metal from roots to aerial parts of the plant. This was evidenced as a lower accumulation at early growth stages and a higher accumulation at maturity, with the distribution between organs coinciding with nutrient incorporation and remobilization in the plant. Moreover, the bioconcentration factor revealed that the bioaccumulation of lead in soybean was a consequence of the lead-recycling plant activity in the past. Taken together, results of the present study demonstrated that soybean crops can incorporate and accumulate potentially toxic metals, such as lead.