Valorization of sulfide rich tailings with nature-based solutions for pasture lands

Abstract

Soil degradation caused by the mining activities is one of the major impacts and challenges for society. Nature-based solutions, such as Technosols, are an alternative for their recovery, which can be accelerated by the use of microorganisms. The objective of this study was to evaluate the viability of implementing risk-free grazing land on sulfide-rich tailings recovered with a Tecnosol with/without a fungal inoculum (Rhizoglomus irregulare and Trichoderma sp.). A mesocosm assay was carried out, under greenhouse and controlled conditions, with sulfide-rich tailings from the Aznalcóllar mine and a Technosol designed with alkaline and eutrophic properties for eight months. Three treatments were established (Tailing + Technosol with fungal inoculation (YM), Tailing + Technosol without fungal inoculation (NM), and Tailing with fungal inoculation (Control)) and a commercial pasture was sown. Several parameters related to the materials collected in each treatment, plant development and multielemental composition of the shoots in two growth cycles were determined. The single application of the fungal inoculum was not sufficient to improve the sulfide-rich tailings and to allow plant germination. Independently of the inoculum application, the Technosol improved the physico-chemical characteristics of the tailings (e.g., increased pH, fertility and decreased the availability of potentially toxic elements). Shoots from the YM and NM treatments showed no significant differences in yield and development and no any risk to animal consumption. The results confirmed that sulfide-rich tailings can be environmentally recovered and socio-economically valorized through the application of a Technosol and pasture land.