Effects of Organic and Inorganic Amendments and Incubation Time on Fractionation of Lead in a Contaminated Calcareous Soil

Soil pollution with heavy metals has become a global concern because of its damaging effects on the environment, including threats to human health, toxicity in plants, and long-term effects on soil fertility. This study was conducted to investigate the effect of organic amendments (biochar 640°C, and biochar 420°C) and inorganic amendments (Pumice, Leca, Zeolite and Bentonite) andincubation time on the chemical forms of Pb in a contaminated calcareoussoil. Treatments consisted of two incubation times (90 and 180 days) and three amendment levels (0, 1, and 5 wt%). The experiment was conducted in a factorial arrangement with completely randomized design, with three replications.  At the end of the incubation times, the chemical fractions of Pb were determined by Tessier sequential extraction method. The experimental resultsindicated that application of amendments effectively decreased the Pb concentrations in the exchangeable fraction (F1) of contaminated soils. The 5% biochar 640 showed the highest decrease in the F1 fraction of Pb. The results showed that Pb concentration increased the exchangeable (16.52%), carbonated (1.02%), oxide (9.53%), and residual (2.1%) fractions and decreased the organic fraction (15.26%) during the time. With the passing of time, treatment with Biochar 640°C and bentonite (5%) was the most effective in decreasing Pb concentration in exchangeable fraction.