The Impact of Additional Pb Input on the Dynamics of Pb-Enriched Agricultural Soils
J.B. Diatta
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Department of Agricultural Chemistry, Agricultural University,
ul. Wojska Polskiego 71 F, 60-625, Poznań, Poland
Pol. J. Environ. Stud. 2006;15(2):219-227
Agricultural ecosystems are differently sensitive to heavy metal inputs, which at present are directly related to human activities. Lead is of particular concern due to its ability to threaten soil quality and human health. The investigated soil samples were collected from different agricultural soils (under cereal croppings) moderately subjected to activity of the Głogów Copper Smelter (Poland). They consisted of an acidic soil (Dystri-Gleyic Fluvisols - S1) and three near neutral to slightly alkaline soils (Haplic Luvisols - S2, Gleyic Fluvisols - S3 and Molli-Gleyic Fluvisols - S4). These soils were tested in order to determine the impact of additional Pb inputs on its dynamics and mobility. Of all the soils studied, S2, S3 and S4 have exhibited higher acid buffer capacities than S1. Lead sorption parameters, such as Langmuir adsorption maximum (amax) and parameters related to interaction energies (b) as well as the Freundlich partition parameter (KF), were used for comparing the reactivity and dynamics of added Pb into these soils. The data showed that S2, S3 and S4 retained more Pb than did S1, characterized by low specific surface area (SSA) and cation exchange capacity (CEC). Charge-based (SDCEC) and specific surface-based (SDSSA) sorption densities were also used for evaluating the direct impact of additional Pb inputs. These parameters revealed that S2, S3 and S4 may support greater inputs of Pb with less threat to its mobility, in contrast to S1. Therefore, any practices leading to additional Pb inputs into the latter soil may result in serious Pb mobility. The negative values of the Gibbs free energy changes (ΔGo) for Pb dynamics in the studied soils confirm that the ion exchange process proceeded naturally and spontaneously with a markedly high affinity for Pb ions developed by S2, S3 and S4, and low affinity by S1.
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