Insight into cesium immobilization in contaminated soil amended with biochar, incinerated sewage sludge ash and zeolite

Abstract

Radioactive cesium (Cs) in the soil represents a severe threat to human health and the environment. Plant uptake is an important pathway for the migration of Cs to the human food chain. It is therefore essential to find effective amendments for reducing the phytoavailability of Cs. In this study, we aimed to evaluate the effectiveness and possible mechanisms of biochar (BC), incinerated sewage sludge ash (ISSA) and zeolite (ZL) on the immobilization of Cs in the contaminated soil. Greenhouse pot experiment was conducted using Napier grass ( Pennisetum purpureum ) to investigate the effects of BC, ISSA and ZL (10% application rate, w/w) on the soil properties, plant biomass, the accumulation and distribution of Cs in the grass grown on the contaminated soil added with Cs as a rate of 100 mg kg −1 . The results showed that all amendments enhanced the grass growth, with the maximum biomass recorded in the ISSA treatment. The concentrations of Cs in the leaf blade, leaf sheath and root of grass significantly decreased with all amendment applications. Especially the BC application showed the lowest Cs concentration in grass, decreased by up to 95% compared to control (no amended soil). Moreover, the obtained results in terms of pH, cation exchange capacity, surface charge, specific surface area and potassium concentration of amendments and potting soils highlighted the remarkable efficiency of biochar to adsorb Cs and reduce the plant uptake of Cs providing key evidences for Cs immobilization. • Cs immobilization in soil amended with three sorbent materials was investigated. • The additions of BC, ISSA and ZL significantly restricted the Cs transfer to plant. • The BC showed the most significant inhibition effect on the plant uptake of Cs. • Cs was immobilized by BC due to its high sorption capacity and K concentration.