Immobilisation of metals in a contaminated soil with biochar-compost mixtures and inorganic additives: 2-year greenhouse and field experiments

Abstract

Besides carbon sequestration and improvement of soil properties, biochar (BC) has increasingly been studied as an amendment to immobilise heavy metals in contaminated soils. In a 2-year experiment, we analysed the effects of poplar BC (P-BC, mixed with compost) and gravel sludge with siderite-bearing material (GSFe) on a Cd-, Pb- and Zn-contaminated soil and on metal concentration in Miscanthus × giganteus shoots under greenhouse and field conditions. In the greenhouse, 1% (m/m) P-BC addition reduced NHNO-extractable Cd, Pb and Zn concentrations by 75, 86 and 92%, respectively, at the end of the study. In the leachates, P-BC (1%) could significantly reduce Cd and Zn in both years. In the field, P-BC (3%) induced a reduction of extractable Cd by 87% whereas a combination of P-BC + GSFe reduced Pb by 82% and Zn by 98% in the first year and by 83 and 96% in the second year. In contrast, the metal immobilisation in the soil was hardly reflected in the shoots of Miscanthus × giganteus which generally showed metal concentrations close to control. While Cd was not influenced in both years, Pb and Zn were slightly reduced. Our study confirmed that Miscanthus is an efficient metal excluder, corroborating its suitability for the production of renewable biomass on metal-contaminated soils.

Combined Application of Biochar and Plant Growth-Promoting Rhizobacteria Improves Heavy Metal and Drought Stress Tolerance in Zea mays

“…A similar trend was observed for the BAF of Ni and Zn, where combined application of ARN7 and GS-BC reduced the BAF irrespective of drought stress condition ( Figure 4 c,d). This might be as a result of the involvement of functional groups in the biochar in HM immobilization, chelation, or complex formation, resulting in decreased HM bioavailability and its uptake by plants [ 39 , 40 ]. Our results are in agreement with the findings of Naveed et al [ 33 ], who demonstrated that biochar amendment reduced Pb content in roots and shoots of Vigna radiata .…”

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

“…Furthermore, it has been shown to reduce cadmium discharge from the soil into nearby bodies of water (Ouyang et al 2017 ). Similarly, co-composting with biochar derived from woody biomass decreased zinc, lead, and cadmium concentrations in amended soils by 92, 86, and 5%, respectively (Karer et al 2018 ).…”