Work

Assessment of biochar, compost, and iron amendments to enhance the phytostabilisation of arsenic in gold mine waste by the Australian native plant species Poa labillardieri (Steud.)

Year: 2025

Type: article

Abstract: Gold mine waste has elevated arsenic (As) concentrations that exceed the Australian national soil guidance values (100 mg/kg). In Australia, Victoria has reported As concentrations of 47,000 mg/kg, causing concern because As is toxic to living organisms; it is carcinogenic, has human health implications and damages ecosystems. Phytostabilisation is a sustainable alternative that is cost-effective, aims to immobilise As in the roots/rhizosphere and restore soil health. Australian natives were previously investigated for phytoremediation and results identified Poa labillardieri as a potential phytostabilising species. Soil amendments have soil ameliorating abilities and previous studies have shown that soil amendments enhance phytostabilisation. This study aimed to identify a soil amendment to optimise phytostabilisation using P. labillardieri . A greenhouse mesocosm experiment was conducted for 100 days and involved soil amendments, 5% biochar, 5% compost and 1% ferric oxide (Fe 2 O 3 ) applied individually or in combination. The treatment combination of 5% biochar and 5% compost (BC), significantly (p ≤ 0.01) increased root As concentrations (657 ± 135 mg/kg) compared to the unamended control (317 ± 12 mg/kg). Shoot As concentrations ranged between 30 and 44 mg/kg for all treatments. The BC treatment increased soil-to-root bioaccumulation to 0.97, 1 being optimal for phytostabilisation. Soil As concentrations significantly decreased (677 ± 21.5 mg/kg) compared to the unamended control (781 ± 6.32 mg/kg). Additionally, removal of As from soil improved from 6.83 ± 5.93 to 50 ± 24 mg/m 3 and in vitro bioaccessibility decreased from 47.0 ± 6.92 to 35.8 ± 0.72%. The BC treatment had greater root (0.01 ± 0.01 g), shoot (0.05 ± 0.02 g) and total biomass (0.06 ± 0.03 g), compared to the control (0.004 ± 0.002 g root biomass; 0.01 ± 0.01 g shoot biomass; 0.014 ± 0.012 g total biomass). The BC treatment shows potential to assist phytostabilisation using P. labillardieri ; It is recommended that a field trial be conducted with the newly developed phytostabilisation technique involving P. labillardieri and soil amendment 5% biochar plus 5% compost to validate the results under natural climatic conditions. • Poa labillardieri is a candidate for phytostabilisation. • 5 % biochar and 5 % compost (BC), significantly increased root As concentrations. • The BC treatment increased soil-to-root bioaccumulation to 0.97, 1 being optimal. • BC treatment shows potential to optimise phytostabilisation.

Source: Chemosphere

DOI: 10.1016/j.chemosphere.2025.144728