Biochar ageing in polluted soils and trace elements immobilisation in a 2-year field experiment

11 páginas.- 8 figuras.- 5 tablas.- 52 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.envpol.2021.118025

Biochar application to soils has become a focus of research during the last decade due to its high potential for C sequestration. Nevertheless, there is no exhaustive information on the long-term effects of biochar application in soils contaminated with trace elements. In this work, a 2-year field experiment was conducted comprising the application of different types of biochar to acidic and moderately acidic soils with high concentrations of As, Cu, Pb, Ba and Zn. In addition, representative samples of each biochar were buried in permeable bags that allowed the flow of water and microorganisms but not their physical interaction with soil aggregates. The biochars significantly adsorbed trace elements from polluted soils. However, given the high total concentration of these persistent trace elements in the soils, the application of biochars did not succeed in reducing the concentration of available metals (CaCl2 extractable fraction). After 2 years of ageing under field conditions, some degradation of the biochars from olive pit, rice husk and wood were observed. This study provides novel information concerning the biochar alterations during ageing in polluted soils, as the decrease of aryl C signal observed by 13C nuclear magnetic resonance (NMR) spectroscopy and the presence of O-containing groups shown by Fourier Transform mid-Infrared Spectroscopy (FT-IR) in aged biochar which enhanced trace elements adsorption. Scanning electron microscopy (SEM) revealed slight changes on surface morphology of aged biochar particles.

EI / FEDER and The Spanish Ministry of Economy, Industry and Competitiveness (MINEICO) are acknowledged for funding this research [projects CGL2016-76498-R and CGL2015-64811-P]. P. Campos is grateful to “Fundaci ́on Tatiana P ́erez de Guzm ́an el Bueno” is thanked for funding pre-doctoral contract of Paloma Campos. MINEICO is also thanked for funding the post-doctoral contract (Ram ́on y Cajal) of J.M. De la Rosa. ́Agueda S ́anchez-Martín and Araceli de la Rosa are thanked for technical assistance in laboratory and field.

Peer reviewed