Bioaccumulation of arsenic in mine waste contaminated soil using Poa labillardieri (Steud.) and soil amendments: A short-term pilot trial

In Australia, Victoria produced ∼2,460,000 kg of gold during the gold rush (1851-1914), with Bendigo as a major gold mining town. Gold mining produced arsenic contaminated waste, and Victoria has reported arsenic concentrations up to 47,100 mg/kg in impacted soil. Soil arsenic concentrations above 100 mg/kg in residential soils with garden access, require site-specific management and remediation. Phytostabilisation, a biological remediation technique is a cost-effective and environmentally sustainable approach to stabilise arsenic in the rhizosphere. Plant growth and metal(loid) bioaccumulation are preliminary assessments of phytostabilisation potential and are investigated in this study. The aim of this study was to conduct a short-term pilot trial to investigate P. labillardieri for plant growth and arsenic bioaccumulation under field conditions and assess soil amendment, 5% biosolids biochar (wet weight (w/w)) plus 5% compost (w/w), for optimisation. The trial was conducted for six months and objectives included quantification of soil characteristics, soil and plant metal(loid) concentrations by acid digestion, arsenic bioaccumulation and microbial analyses by quantitative polymerase chain reaction. Poa labillardieri successfully grew and bioaccumulated arsenic under field conditions with and without the amendment (5% biochar plus 5% compost). The plant only treatment significantly (p = 0.01) bioaccumulated more arsenic in the roots (∼108 mg/kg) than plant plus amendment (∼55 mg/kg); and had a significantly (p = 0.017) higher bioconcentration factor. This demonstrates that this native plant has potential for phytostabilisation without assistance. A long-term field trial with additional analyses is recommended to validate P. labillardieri and the soil amendment for phytostabilisation of gold mine waste impacted soils. The significance of this study was that P. labillardieri was able to thrive in a semi(arid) climate with elevated arsenic concentrations and bioaccumulate arsenic, without the assistance of the amendment.