Effect of cyclic wetting-drying on distribution of different quantities of lead loaded to three soils from Western Azerbaijan

Bioavailability, toxicity, and mobility of potentially toxic element (PTEs) in soils depend on their partition between solution and solid-phase and their further redistribution among solid-phase components. The wetting-drying consequence cycle is one of the most important factors in controlling the behavior and fate of PTEs in contaminated soils. The aim of this study was to assess the distribution of different applications of lead (Pb) in three soils, with different calcium carbonate contents, after incubation under a wetting-drying (WD) soil moisture regime using sequential extraction procedure. To quantify the binding intensity and to assess the mobility and availability of applied Pb, the reduced partition index (IR) and the percentage or absolute concentration of Pb in soluble + exchangeable fractions were used, respectively. This trail was conducted as a factorial experiment based on randomized complete block design with three factors, soil (in 3 levels), Pb concentration (in 4 levels) and drying-wetting cycles (in 5 levels) in three replications. Results showed that, the binding intensity of Pb significantly increased by WD, however, decreased as the Pb application quantities to soils increased. However, in different soils, no significant differences were recorded. Although, the first WD cycle significantly decreased the soluble + exchangeable fraction of Pb, the further WD cycles had no significant effect. However, mobility and availability, and consequently the potential environmental risks of Pb, increased by increasing Pb applications to soils.