Biosolids, mycorrhizal fungi and Eucalypts for phytostabilization purposes of sulphidic mine tailings

Abstract

In mine tailings facilities, phytostabilisation is an attractive technology for long-term remediation. We tested the effect of the addition of biosolids combined with a native arbuscular mycorrhizal inoculum (AMF) on growth of a eucalypt (E. cladocalyx), and on trace element stabilization of sulphidic gold mine tailings. A glasshouse trial was established using four substrates: tailings (T); tailings with a layer of 5 cm topsoil (TS); tailings amended with 100 dry t ha-1 biosolids (LB), and tailings amended with 500 dry t ha-1 biosolids (HB). Half pots were inoculated with a mixture of Glomus sp. (WUM51 - 9227), Scutelaspora aurigloba (WUM51 - 53) and Acaulospora levis (WUM46) culture mix, and others were uninoculated controls. Two seeds per pot were sown in the pots and after 30 days all pots were uniformly thinned to 1 plant/pot. Plants were destructively harvested at 150 days after the sowing. Leaf and stem weights, leaf area and plant height were measured for each plant. Nutrients and trace element concentrations in leaves and stems were also determined. Addition of biosolids significantly increased mycorrhizal colonization (both ectomycorrhizal (ECM) and arbuscular mycorrhizal) in roots compared with the other treatments. Biosolids clearly improved the establishment and growth of the eucalypts. At low biosolid doses, mycorrhizal inoculum increased plant biomass production and the effectiveness of nutrient uptake. Trace element concentrations in trees of the biosolid-amended pots were in general high. It is therefore important to reduce the uptake of toxic elements by plants, which can be done successfully by adjusting amendment addition and the use of mycorrhizal inoculation, and then monitoring trace element contents of different taxa growing in the affected area.