The distribution of topically applied heavy metals in the soil

Summary Long-term pot experiments were conducted to determine the leaching potential of topically applied lead, cadmium, and nickel through the soil. Four rates of each metal (0, 10, 100 and 200 mg/kg soil), in the nitrate form were used. Metals were extracted with acidic ammonium acetate after 30 weeks of intermittent leaching. The concentration of extractable element varied with the depth in the soil and the type of extractable metal. Lead was confined to the upper few centimeters of soil whereas cadmium moved down to a considerable depth. Nickel was more uniformly distributed over the total soil depth than the other two metals. The concentration gradients observed are discussed with respect to their effect on germination and yield of plants.