Remediation and improvement of abandoned iron mine soil bio-physicochemical properties by amendments and bioenergy plant Ricinus communis L

Abstract

Abandoned iron mine soil (MS) contains elevated concentrations of heavy metals (HMs) with poor bio-physicochemical characteristics, causing significant risk to the environment including associated living organisms if not handled properly. Studies related to iron ore MS remediation and reclamation with commercially important bioenergy plants and economically viable amendments are still scarce and elusive. This study investigates the influence of farmyard manure (FYM), NPK fertilizer and the blending of different ratios of garden soil (0–100 %) on the MS bio-physicochemical parameters and the response of Ricinus communis L. The pot experiment was carried out for 90 days in a naturally illuminated net house to record the growth parameters, tolerance index (TI), metal accumulation, bioaccumulation factor (BAF), total metal extract by plant (MetalEx) and improvement of soil bio-physicochemical properties after harvesting. Study shows MS has low pH, low organic carbon (OC), and matter (OM), water holding capacity (WHC) and lack of key nutrients along with low soil microbial biomass carbon (Cmic) and nitrogen (Nmic) with high levels of Fe, Cu, Pb, and Ni with 2032.33, 34.52, 64.94 and 70.67 mg kg−1 respectively. The amendments of NPK and FYM enhanced the growth of R. communis by 179.86 and 441.32 % respectively. The TI, chlorophyll and carotenoid levels show an upward trend along the growing period. The accumulation of HMs in NPK unit was found in order of Fe > Ni > Pb > Cu and for FYM unit as Fe > Pb > Cu > Ni. The BAF and MetalEx values were significantly high for FYM treatment sets. The soil properties like OC, OM, Cmic and Nmic improved after harvesting by 13, 17, 8.84 and 6.38-fold, respectively. Overall, the study concludes that the application of FYM showed better results than NPK. R. communis has found to bear a substantial potential to accumulate high concentrations of HMs and grow well in multi-metal contaminated MS. © 2024 Elsevier Ltd