Arsenic (As)-contaminated gold mine waste is a global problem and poses a significant risk to the ecosystem and community (e.g., carcinogenic, toxicity). Arsenic concentrations of 77,000 mg/kg and 22,000 mg/kg in mine waste have been reported for Canada and Australia, respectively. Research is investigating environmentally sustainable techniques to remediate As-rich mine waste. Biological techniques involving plants (phytoremediation) and soil amendments have been studied to bioaccumulate As from soil (phytoextraction) or stabilise As in the rhizosphere (phytostabilisation). Identified plant species for phytoremediation are predominately fern species, which are problematic for arid to semi-arid climates, typical of gold mining areas. There is a need to identify native plant species that are compatible with arid to semi-arid climates. Arsenic is toxic to plants; therefore, it is vital to assess soil amendments and their ability to reduce toxicity, enhance plant growth, and improve soil conditions. The effectiveness of a soil-amending phytoremediation technique is dependent on soil properties, geochemical background, and As concentrations/speciation; hence, it is vital to use field soil. There is a lack of studies involving mine waste soil collected from the field. Future research is needed to design soil-amending phytoremediation techniques with site-specific mine waste soil and native plant species.

Persistent organohalogen pollutants—including halogenated nitrophenols (HNCs), trichloroethylene (TCE), and per- and polyfluoroalkyl substances (PFAS)—pose serious environmental and health risks due to their stability, toxicity, and bioaccumulation potential. This review critically assesses current remediation technologies including advanced oxidation processes (AOPs), adsorption, membrane filtration, and thermal treatments. While these methods can be effective, they are often limited by high costs, energy demands, toxic byproduct formation, and sustainability concerns. Emerging biological approaches offer promising alternatives. Among these, fungal-based degradation methods (mycodegradation) remain significantly underrepresented in the literature, despite fungi demonstrating a high tolerance to contaminants and the ability to degrade structurally complex compounds. Key findings reveal that white-rot fungi such as Phanerochaete chrysosporium and Trametes versicolor possess enzymatic systems capable of breaking down persistent organohalogens under conditions that inhibit bacterial activity. This review also identifies critical research gaps, including the need for direct comparative studies between fungal and bacterial systems. The findings suggest that integrating mycodegradation into broader treatment frameworks could enhance the environmental performance and reduce the long-term remediation costs. Overall, this review highlights the importance of diversifying remediation strategies to include scalable, low-impact biological methods for addressing the global challenge of organohalogen contamination.

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.

Arsenic (As) contaminated gold mine waste represents a significant issue for ecosystem and human health, as it is a known carcinogen and environmental toxin. Bendigo in Victoria, Australia, has reported As concentrations up to 22,000 mg/kg, exceeding the national soil guidance values (100 mg/kg) by 220-fold. To reduce exposure and potential human health risk, remediation or risk management strategies are required. Traditional remediation, such as excavation and landfill, often fail to improve soil conditions and are expensive. Biological remediation using plants (phytoremediation) represents a cost-effective strategy that results in the restoration of soil function and ecosystem services. There is a need to identify native plants for phytoremediation as current research focuses on fern species, which are not suitable for Bendigo. This study aimed to identify a native phytostabilising plant by conducting a mesocosm experiment involving Juncus usitatus, Poa labillardieri, and Themeda triandra. Plants grew in mine waste for 100 days; all survived and bioaccumulated As in the roots (phytostabilisation). Poa labillardieri grew significantly more biomass (roots 0.24 ± 0.01 g; shoots 0.22 ± 0.03 g (d/w)) and bioaccumulated the most As (~ 100 mg/kg plant biomass). The bacterial community was investigated to assess soil health and As association. The rhizosphere microbiota stabilised after root colonisation for Poa labillardieri and Themeda triandra, as indicated by richness and evenness changes. The two dominant phyla were Actinobacteriota and Proteobacteria, which displayed As tolerance. A keystone taxon, Latescibacterota, exhibited a positive relative association with As remediation. Poa labillardieri is a good candidate for future phytostabilisation trials.

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 (Fe₂O₃) 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/m³ 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.

Phytoremediation is a cost-effective and sustainable method for the remediation of minewaste contaminated with heavy metals such as arsenic (As). However, mine waste soil is often nutrient-limited, especially in nitrogen (N), impairing plant growth and phytoremediation. This study aimed to assess how planting density together with soil amendments, biochar, and an isolated indigenous nitrogen-fixing bacterium (NFB) (Bacillus subtilis) affect the efficacy of phytoremediation by Juncus pauciflorus of an As-contaminated mine waste soil from Bendigo, Victoria. Three plant densities, including 9, 26, and 44 plants/m², were grown in As-contaminated mine waste soil amended with biochar (10% w/w) and B. subtilis (8.1 × 10⁸ CFU/mL) and incubated for 100 days. Plant biomass, plant As uptake, soil As concentration, bacterial abundance (total and NFB using 16S and nifH gene copy numbers, respectively), and total soil N were assessed. Juncus pauciflorus at a higher density (44 plants/m²) promoted the greatest biomass and total As uptake, 70.22 g/m² and 209.53 mg/m², respectively. Plant density significantly influenced the root–shoot partitioning of As. Higher densities increased shoot uptake (BAF_soil→shoot), and TF_root→shoot values remained >1 across all treatments, confirming the active translocation of As to the shoots, suggesting both phytostabilisation and phytoextraction potential by J. pauciflorus. Planting density significantly reduced soil As, ranging from 8000 mg/kg to 9500 mg/kg, compared to the initial concentration (13,032 mg/kg). The abundance of 16S and nifH genes was stable among treatments, ranging from 7 log₁₀ copies/g to 12 log₁₀ copies/g. TN content in soils amended with 44 plants/m² contained the highest TN content at day 33, approximately 7000 mg/kg. This study is the first to report that higher planting density of J. pauciflorus amended with biochar and NFB provides the strongest phytoremediation performance in highly As-contaminated mine soil by enhancing As uptake and accumulation in aboveground biomass. Most importantly, the results show that plant density also regulates the plant’s remediation strategy, shifting J. pauciflorus between phytostabilisation at dense planting and greater phytoextraction at lower density. These findings support the use of native plants in combination with biochar and microbial amendment as a sustainable strategy for remediating As-contaminated mine waste.