The Phytoremediation of Arsenic-Contaminated Waste by Poa labillardieri, Juncus pauciflorus, and Rytidosperma caespitosum

Phytoremediation represents a potentially effective and environmentally friendly technology to remediate arsenic (As) in mine waste soils. However, soil amendments are often required to improve phytoremediation due to depleted nutrients in mine waste. This study aims to assess the effect of biosolids biochar, applied at different rates (0%, 5%, and 10%) on As phytoremediation using three plant species: Poa labillardieri, Rytidosperma caespitosum, and Juncus pauciflorus. This study was conducted in a replicated greenhouse pot study using soil from an abandoned mine site. Dry plant biomass, As concentration in plants and soil, and soil microbial abundance were investigated. Juncus pauciflorus produced eight times more root and shoot biomass than R. caespitosum in soils amended with 10% biochar. The highest As uptake was also observed in J. pauciflorus grown in soils amended with 10% biochar (7.10 mg/plant), while R. caespitosum had the lowest As uptake in soils without biochar (0.16 mg/plant). In soils amended with 10% biochar, the total bacterial community decreased to approximately 8.50 log10 copies/g, compared to the initial soil (9.05 log10 copies/g), while the number of gene copies of the nifH gene increased, suggesting the importance of nitrogen-fixing bacteria to promote plant growth. Taguchi analysis confirmed that plant species was the key factor for As phytoremediation, followed by biochar application dose. This study showed that J. pauciflorus and the addition of 10% biochar was the best treatment for remediating As-contaminated mine waste, offering the potential for use commercially. Moreover, the utilisation of biochar derived from biosolids as a soil amendment for enhancing phytoremediation represents good circular economy practice to manage excessive biosolids production.