Biochar from crop residues for remediation of trace element polluted soils

Póser presentado en el 17th International Conference on Chemistry and the Environment (ICCE 2019) 16th and 20th of June, 2019 Thessaloniki (Greece).- Puede descargar el programa completo en https://icce2019.org/content/ICCE-2019-Conference-Programme.pdfBiochar is the solid material rich in aromatic carbon produced through the pyrolysis (heating under limited oxygen conditions) of residual biomass (De la Rosa et al., 2014). Paz-Ferreiro et al. (2014) showed that biochars can reduce the bioavailability and leachability of heavy metals in contaminated soils. Trace elemen t polluted soils is a worldwide concern covering 37% of the degraded soils in the European Union (EEA, 2007). The aim of this study is to produce a biochar from agricultural residues efficient in the restoration of soils contaminated with trace elements. In this study, the influence of biochar on soil enzymatic activity and plant germination were studied in two Typic Xerofluvent soils polluted with trace elements, which were sampled in an area affected by the breaching of a tailing dam occurred in 1998 (Aznalcóllar mine accident; SW Spain) with two respective levels of contamination (MPS; moderately polluted soil and HPS; highly polluted soil). Biochars used in this study were produced from four different biomasses: rice husk, pruned olive trees, olive pits and “alperujo” (a byproduct of the olive oil). The feedstock was pyrolysed in a 0.64L steel reactor under N2 atmosphere. Pyrolysis temperature and reaction time were controlled, thus biochars were produced with temperatures ranging between 400 and 500 ºC whereas reaction time ranged from 1 to 4h. Each soil was mixed with 0, 2, 5 and 10% of biochar, and the pots were made in triplicate. All the pots were incubated under controlled conditions (60% of water holding capacity; 25 ºC) during 65 days and sown (Brassica rapa spp. Pekinensis). The plant experiment also lasted 65 days. The following parameters were determined for this study: bioavailability of trace elements (As, Cd, Cu, Fe, Ni, Pb, Sr and Zn), germination rates, plant biomass, partitioning of trace elements into Brassica leaves (Ba, Cd, Cu, Fe, Ni, Pb, Sr and Zn), pH, dehydrogenase (DHA) and β-glucosidase (BGA) activities in biochar amended and un-amended soils. Changes in bioavailability of trace elements in soils were influenced by incubation conditions, not by biochar application. Soil pH increased with the dose of biochar. DHA showed 10 times greater activity in MPS than HPS. Furthermore, biochar amended MPS showed greater DHA than control soils. BGA decreased with increasing biochar rate application. No significant differences were observed in the germination rates in MPS, whereas germination increased with biochar dose for HPS.References De la Rosa, J.M., Paneque, M., Miller, A.Z. & Knicker, H. (2014). Relating physical and chemical properties of four different biochars and their application rate to biomass production of Lolium perenne on a Calcic Cambisol during a pot experiment of 79 days. Science of the Total Environment, 499, 175-184. EEA. (2007). Progress in Management of Contaminated Sites. CSI 015. Copenhagen, Denmark: European Environmental Agency. Paz-Ferreiro, J., Lu, H., Fu, S., Méndez, A. & Gascó, G. (2014). Use of phytoremediation and biochar to remediate heavy metal polluted soils: a review. Solid Earth, 5, 65-75.The Spanish Ministry of Economy, Industry and Competitiveness (MINEICO) and AEI/FEDER are thanked for funding the project CGL2016-76498-R. P. Campos thanks the “Fundación Tatiana Pérez de Guzmán el Bueno” for funding her PhD.Peer reviewe