Lead adsorption-desorption isotherms to predict its plant availability in diverse soils of India

The present study investigates the complex relationship between soil properties and adsorption-desorption dynamics of lead (Pb) within soils, examining two distinct temperature environments and its impact on plant accessibility. Through laboratory and pot experiments encompassing twenty-five soils with diverse physico-chemical properties, important findings emerged, which highlighted the essential role of free-sesquioxide (Fe₂O₃ and Al₂O₃) as the primary soil component dictating Pb adsorption, followed by electrical conductivity (EC), and cation exchange capacity (CEC). Notably, the adsorption capacity of Pb across soils exhibited enhancement with increasing initial metal concentrations and temperatures, delineating the temperature-dependent nature of the adsorption process. Thermodynamic analysis revealed that adsorption was endothermic, supported by positive enthalpy (∆H°) values. Additionally, negative ∆G° values at both temperatures confirmed the spontaneous nature of the adsorption process. The average values of desorption Index was close to be 1 for some soils suggesting reversible adsorption-desorption. As high as 76 and 67% variability in Pb content in plant could be explained by adsorption parameters. These findings provide valuable insights into Pb adsorption-desorption in soil ecosystems, guiding the development of effective strategies for Pb remediation in contaminated soils.