Adsorption of Lead on Agricultural Land at Žitný Ostrov (Slovakia)

Abstract Heavy metals are important environmental pollutants threatening the health of human populations and natural ecosystems. Like other inorganic and organic contaminants, the fate of heavy metals in the environment is largely controlled by sorption reaction with soil colloids. The ecological effects of heavy metals in soils are closely related to the content and speciation of the elements in the solid and liquid phases of soils. In connection with the possible binding mechanisms of heavy metals in soils, the concept of specific and non–specific adsorption was discussed. Recent results have indicated that the adsorption of heavy metals on the soil particles is not only restricted to the formation of surface complexes but can also take place in the interior of minerals. Heavy metal sorption by the organic residues at all concentrations was very high. A positive relationship between the rate of adsorption and dosage was obtained indicating that the adsorption process was influenced by increasing the dosage of the residue as well as the shaking period. The sorption data obtained were fitted Freundlich and Langmuir isotherms out of which the Freundlich adsorption model was found to have the best fit for Pb. Movement and attenuation of heavy metals in soils are among other processes controlled by sorption onto the surfaces of soil particles. Processes like precipitation/coprecipitation, complexation and competitive effects of other cations may also influence the attenuation, but in all cases, sorption will be involved, and at natural and slightly polluted concentration levels sorption may be the predominating attenuation process. The Pb sorption on ten investigated soils from the Žitný ostrov area (Slovakia) has been studied in laboratory conditions. The aims were the estimation of adsorbed amount of lead S, determination of adsorption parameters for several soil types (L1, L2, L3, L4 loam soils, SL1, SL2, SL3, SL4 sandy-loam soils, CL5 clay-loam soil, C6 clay soil) and comparison of the obtained results with the results introduced in publishing works. Batch adsorption experiments were performed with a very wide range of lead concentrations (0,01-500 mg/l Pb2+) at a constant soil/solution ratio. The parameters KF, n of Freundlich isotherm and parameters Qmax, KL of Langmuir isotherm were determined experimentally.