Influence of soil and agricultural technique in metal absorption by vegetables

The aim of this work is to verify the influence of soil and agricultural techniques in the metal absorption by the vegetables. Metal concentrations were evaluated in soil and vegetable samples from different regions and cultivated by different agricultural techniques. PIXE, 252Cf-PDMS and Radiochemical techniques were applied. Si, Zr, Ce, Th and Pb, identified in soil samples, were not biologically available. Ga, Ge, As and Br, identified in tubercles, show that spray pesticides used on the vegetable leaves were absorbed by them. 232Th and 238U, presented in the soil, were not absorbed by the vegetables. Airborne particles from anthropogenic sources (CFn, VCn) were absorbed by the vegetables. Compounds from mineral sources, presented in soil, (V+, VCO3, HPO4, Cr+, CrOH+ Mn+, FeH, Fe(OH)n) and bioorganic compounds (N+, Ca(CN)n +, CnH+) were identified in the vegetables. Metal absorbed by the vegetables is not dependent on metal concentration in soil. Different tubercles cultivated in the same soil show similar metal absorption. The exogenous contributions, such as the elements presented in water irrigation, pesticides, fertilizers and airborne particles deposited on leaves can be absorbed by the vegetables. Absorption by the roots depends on the chemical compound of the elements. Pesticide sprays and air pollution can cause more contamination in the vegetables than in the soil. The use of this methodology allows the identification of possible sources of metals in soils and in vegetables and metal speciation. (author)