4. Conclusions
The metal concentrations (Cd, Pb and Zn) in soybean crops grown close to different emission sources in Córdoba, Argentina, revealed a toxicological risk for a potential Chinese consumer. Tak- ing into account that the maximum levels in agricultural soils were exceeded in some areas by Pb, it is important to perform further studies related to the maximum permitted levels for heavy metals in agricultural soils with different physical and chemical condi- tions. For our particular samples, the seed quality parameters were not affected by a higher metal content, reflecting no relationship existing between physiological or morphological quality with toxic metal accumulation.
Significant differences were found in the physical (pH, OM, EC) and chemical parameters (metal concentrations) between the rhi- zosphere and bulk topsoils, indicating that rhizosphere soil is an important soil compartment with respect to food safety, due to the bioaccumulation of toxic metals. Considering these findings, it is necessary to perform an evaluation and possible modification of agricultural soil guidelines, which should in fact only consider the exchangeable fraction of metals and the physical characteristics of different soil types, rather than the pseudototal fraction.
Finally, considering the bioaccumulation and magnification of toxic heavy metals such as Pb and Cd, the potential risk of con- suming meat from cattle whose main sources of food are products derived from soybeans should be taken into account in future research.