Short-term evolution of physico-chemical properties of Technosols made from contaminated soils by pyritic sludge

Abstract

The aim of this study was to evaluate, at short term, the physico-chemical and biological quality of residually contaminated soils after the Aznalcóllar mine spill and treated with “tailor-made Technosols”. Two Technosols with different properties (T4 and T6) were used as treatments. Both are composed of ex-situ contaminated soil and two wastes from mining (sludge rich in iron oxyhydroxides and marble sludge); and T4 by a waste from agro-industry (solid olive-mill by-product) and T6 by one from urban activity (vermicompost from gardening). After 6 months of application, samples of Technosols and treated contaminated soils were characterised (soil properties, total, soluble and available concentrations of potentially harmful elements (PHEs), and toxicity bioassay with Lactuca sativa L.) and compared with baseline conditions. Some soils in the Guadiamar Green Corridor presented a significant environmental and human health risk due to their extreme characteristics (pH<4, low fertility and multielemental contamination). After only six months, the application of Technosols on these soils has led to a significant improvement in their physico-chemical and biological properties (pH neutralisation, reduction of mobility PHEs and enrichment in organic carbon). So, in the long term, soil remediation through the Technosols is expected to be effective and proven in future studies.