Heavy metal uptake by barley growing in polluted soils: relationship with heavy metal speciation in soils

One soil polluted by lead and zinc and three soils contaminated with different copper (Cu), lead (Pb), and zinc (Zn) solutions in the laboratory were sown with barley (Hordeum distichum) to study the relationship between metal uptake and metal speciation in soil. The pH and organic matter content played a fundamental role in metal speciation and in particular in the amount of metal in exchangeable form. The results show that Zn is transported from roots towards leaves and a major uptake occurs. Cu and Pb are accumulated to a lesser extent than Zn and immobilized by root cells; for Cu and Pb a restriction of internal transport occurs. Tests performed by contaminating the soil during plant growth showed that soil having an acidic pH value and a lower organic matter content was not able to bind the metals, which were consequently sorbed by plants in high amounts.