Impacts of bamboo biochar on the phytoremediation potential of Salix psammophila grown in multi-metals contaminated soil

Mechanism of clay mineral modified biochar simultaneously immobilizes heavy metals and reduces soil carbon emissions

Heavy metal pollution in farmland soil has become increasingly severe, and multi-element composite pollution has brought enormous harm to human production and life. Environmental changes in cold regions (such as freeze-thaw cycles and dry-wet alternations) may increase the potential physiological toxicity of heavy metals and exacerbate pollution risks. In order to reveal the effectiveness of sepiolite modified biochar in the remediation of the soil contaminated with lead (Pb), cadmium (Cd), and chromium (Cr), the rice husk biochar pyrolyzed at 500 and 800 °C were selected for remediation treatment (denoted as BC500 and BC800). Meanwhile, different proportions of sepiolite were used for modification (biochar: sepiolite = 1: 0.5 and 1: 1), denoted as MBC500/MBC800 and HBC500/HBC800, respectively. The results showed that modified biochar with sepiolite can effectively improve the immobilization of heavy metals. Under natural conservation condition, the amount of diethylenetriaminepentaacetic acid (DTPA) extractable Pb in BC500, MBC500, and HBC500 decreased by 5.95, 12.39, and 13.55%, respectively, compared to CK. Freeze-thaw cycles and dry-wet alternations activated soil heavy metals, while modified biochar increased adsorption sites and oxygen-containing functional groups under aging conditions, inhibiting the fractions transformation of heavy metals. Furthermore, freeze-thaw cycles promoted the decomposition and mineralization of soil organic carbon (SOC), while sepiolite hindered the release of active carbon through ion exchange and adsorption complexation. Among them, and the soil dissolved organic carbon (DOC) content in HBC800 decreased by 49.39% compared to BC800. Additionally, the high-temperature pyrolyzed biochar (BC800) enhanced the porosity richness and alkalinity of material, which effectively inhibited the migration and transformation of heavy metals compared to BC500, and reduced the decomposition of soil DOC.

Phytoremediation of contaminated sediment combined with biochar: Feasibility, challenges and perspectives

The accumulation of contaminants in sediments is accelerated by human activities and poses a major threat to ecosystems and human health. In recent years, various remediation techniques have been developed for contaminated sediments. In this review, a bibliometric analysis of papers on sediment remediation indexed in the WOS database between 2009 and 2023 was conducted using VOSviewer. We describe the development of biochar and plants for sediment contaminant removal. However, the single processes of biochar remediation and phytoremediation can be impeded by (i) low efficiency, (ii) poor tolerance of plants towards pollutants, (iii) difficulty in biochar to degrade pollutants, and (iv) biochar aging causing secondary pollution. Fortunately, combination remediation, realized through the combination of biochar and plants, can overcome the shortcomings of their individual applications. Therefore, we suggest that the remediation of contaminants in sediments can be accomplished by combining biochar with macrophytes and considering multiple limiting factors. Here, we explore the challenges that co-remediation with biochar and macrophytes will face in achieving efficient and sustainable sediment remediation, including complex sediment environments, interaction mechanisms of biochar-macrophyte-microorganisms, emerging pollutants, and integrated life cycle assessments, which can provide references for combined biochar and plant remediation of sediments in the future.

Effect of iron-loaded sludge biochar amendments on phytoremediation potential of Cr-contaminated soils by Leersia hexandra swartz

In this study, the effect of iron-loaded sludge biochar (ISBC) with different amendment dosages (mass ratio of biochar to soil equal to 0, 0.01, 0.025 and 0.05) on the phytoremediation potential of Leersia hexandra swartz (L. hexandra) to Cr-contaminated soil was investigated. With increasing ISBC dosage from 0 to 0.05, plant height, aerial tissue biomass and root biomass increased from 15.70 cm, 0.152 g pot-1 and 0.058 g pot-1 to 24.33 cm, 0.304 g pot-1 and 0.125 g pot-1, respectively. Simultaneously, the Cr contents in aerial tissues and roots increased from 1039.68 mg kg-1 to 2427.87 mg kg-1 to 1526.57 mg kg-1 and 3242.62 mg kg-1, respectively. Thus, the corresponding bioenrichment factor (BCF), bioaccumulation factor (BAF), total phytoextraction (TPE) and translocation factor (TF) values were also increased from 10.52, 6.20, 0.158 mg pot-1 (aerial tissue)/0.140 mg pot-1 (roots) and 0.428 to 15.15, 9.42, 0.464 mg pot-1 (aerial tissue)/0.405 mg pot-1 (roots) and 0.471, respectively. The significant positive effect of ISBC amendment was primarily attributed to the following three aspects: 1) the root resistance index (RRI), tolerance index (TI) and growth toxicity index (GTI) of L. hexandra to Cr were increased from 100%, 100% and 0%-216.88%, 155.02% and 42.18%, respectively; 2) the bio-available Cr content in the soil was decreased from 1.89 mg L-1 to 1.48 mg L-1, while the corresponding TU (toxicity units) value was declined from 0.303 to 0.217; 3) the activities of urease, sucrase and alkaline phosphatase in soil were increased from 0.186 mg g-1, 1.40 mg g-1 and 0.156 mg g-1 to 0.242 mg g-1, 1.86 mg g-1 and 0.287 mg g-1, respectively. In summary, ISBC amendment was able to significantly improve the phytoremediation of Cr-contaminated soils by L. hexandra.

Facilitated remediation of heavy metals contaminated land using Quercus spp. with different strategies: Variations in amendments and experiment periods

Phytoremediation using trees combined with soil amendments has gained much attention for its highly cost-effective trait. In natural field conditions, however, the results may not reflect the true performance of amendments based on short-term laboratory studies. In this three-year field trial, various soil amendments such as rice straw biochar, palygorskite, a combined biochar of rice straw biochar and palygorskite, and hydroxyapatite were used to systematically study the potential of the low-accumulator (Quercus fabri Hance) and high-accumulator (Quercus texana Buckley) for cadmium (Cd) and zinc (Zn) to remediate severely contaminated soils. Soil amendments enhanced the dendroremediation capacity of Quercus as the growth period prolonged. In 2021, the rice straw biochar treatment increased Cd and Zn accumulation by 1.76 and 2.09 times in Q. fabri, respectively, compared to the control. Cd and Zn accumulation increased to 1.78 and 2.10 times, respectively, under combined biochar treatment for Q. texana compared to the control. Metals accumulation was mainly enhanced by soil amendments through increasing the growth biomass of Q. fabri and improving the biomass and bioconcentration ability of Q. texana. Overall, soil amendments effectively improved the phytoremediation efficiency of Quercus in the long term, and selecting suitable amendments should be fully considered in phytoremediation.

Nerium oleander could be used for sustainable management of traffic-borne elemental-enriched roadside soils

Metal pollutants released from motor vehicles are deposited in roadside environments. Metals are non-biodegradable and biomagnify in the food chain causing significant health hazards at all levels of the ecosystem. Hence, management of contaminated roadside verges is critically important and should be kept in mind while planning specific management strategies of such areas. Native vegetation could help to decontaminate heavy metal polluted soils in the best sustainable way. Therefore, this study was designed to assess the potential of Nerium oleander to accumulate heavy metals commonly released by automobiles such as Pb, Cd, Ni, and Zn along with various C and N compounds from five different locations along a busy road in Punjab, Pakistan, during summer and winter seasons. N. oleander showed the ability to absorb C, N, and heavy metals Pb and Cd; the maximum concentration of Pb and Cd was 8.991 mg kg-1 and 0.599 mg kg-1, respectively. These pollutants negatively affected photosynthetic pigments, gas exchange attributes, soluble proteins, and free amino acids. But antioxidant activity of N. oleander was found to be increased in both seasons. The metal accumulation in the plant was higher in the summer though. We highly recommend that by growing N. oleander at roadside verges for decontamination of vehicular pollutants could lead to sustainable management of these corridors.

Metal tolerance capacity and antioxidant responses of new Salix spp. clones in a combined Cd-Pb polluted system

To investigate the physiochemical characteristics of two new clones, Salix matsudana 'J172' (A7) and Salix matsudana 'Yankang1' (A64) in combined Cd-Pb contaminated systems, a hydroponic experiment was designed. The plant biomass, photosynthesis, antioxidant responses and the accumulation of metals in different plant parts (leaf, stem, and root) were measured after 35-day treatments with Cd (15, 30 µM) and Pb (250, 500 µM). The results showed that exposure to Cd-Pb decreased the biomass but increased the net photosynthetic rate for both A7 and A64, demonstrating that photosynthesis may be one of the metabolic processes used to resist Cd-Pb stress. Compared with control, roots exposed to Cd-Pb had higher activity of superoxide dismutase and more malondialdehyde concentrations, which indicated the roots of both clones were apt to be damaged. The concentrations of soluble protein were obviously higher in the roots of A64 than A7, indicating the roles of the antioxidative substance were different between two willow clones. Soluble protein also had significant relationship with translocation factors from accumulation in roots of A64, which illustrated it played important roles in the tolerance of A64 roots to heavy metals. The roots could accumulate more Pb rather than transport to the shoots compared with Cd. The tolerance index was more than 85% on average for both clones under all the treatments, indicating their tolerance capacities to the combined stress of Cd and Pb are strong under the tested metal levels. Both clones are the good candidates for phytoremediation of Cd and Pb by the root filtration in the combined contamination environment.

Evaluation of dendroremediation potential of ten Quercus spp. for heavy metals contaminated soil: A three-year field trial

Woody plants have gained considerable attention for remediating soils contaminated with heavy metals because of their cost-efficient and ecologically friendly nature. However, most studies on potential phytoremediation evaluation are limited to short-term experiments in greenhouse or field, meaning that differences may exist between laboratory results and application in natural environment. In this study, ten Quercus spp. were tested in a consecutive 3-year field trial (2018-2020) to assess their dendroremediation abilities for Cd and Zn contaminated soil. The results revealed that nine Quercus spp. demonstrated good survival ability without any stress, except for Quercus velutina Lam., in the 3-year growth period. In 2020, Quercus texana Buckley and Quercus fabri Hance plants produced the greatest biomass (2100 and 1880 g plant^-1) among the nine Quercus spp. Quercus texana had the highest total Cd accumulation (39.3 mg plant^-1) in 2020, which was 8.5 times higher than that in 2018, followed by Quercus pagoda Raf. (8.85 mg plant^-1) and Q. fabri (8.07 mg plant^-1) plants, respectively, whereas Cd accumulation increased by 7.4 times for Q. pagoda and 22 times for Q. fabri compared to 2018. The results from 2020 indicated that Q. fabri had the highest Zn accumulation (205 mg plant^-1), followed by Quercus nigra L. (149 mg plant^-1) and Q. texana (140 mg plant^-1), respectively, and these values increased 14, 6.4, and 6.2 times in comparison to 2018. The comprehensive bioaccumulation index (CBAI) was proposed to evaluate the dendroremediation potential of Quercus spp., suggesting that Q. texana and Q. fabri had the most outstanding potential for remediation of Cd and Zn polluted soil, with the values of 0.82 and 0.60, respectively. In summary, Q. texana and Q. fabri are ideal for remediating Cd/Zn-contaminated soil, and long-term field trials and the CBAI method are helpful for comprehensively evaluating the remediation capacity of trees.

Promotion effect of graphene on phytoremediation of Cd-contaminated soil

Echinacea purpurea (L.) Moench was selected as a remediation plant in this study, and different concentrations of graphene oxide (GO) were added to Cd-contaminated soil. Through pot experiments, the effect of E. purpurea on Cd-contaminated soil was determined at 60 days, 120 days, and 150 days. A preliminary study on the remediation mechanism of GO was explored through changes in the forms of Cd in the rhizosphere soil, soil pH, and soil functional groups. Results showed that the optimal concentration of GO was 0.4 g/kg, and under the condition, the accumulation of Cd in the roots of E. purpurea was as high as 113.69 ± 23.86 mg/kg, and the maximum EF reached 5.87 ± 1.34. Compared with those of the control group, accumulated Cd concentration and EF in the roots increased by 60.34% and 2.32, respectively. Correlation analysis showed that the absorption and accumulation of Cd was negatively correlated with the exchangeable Cd content at 120 days, and the exchangeable Cd was negatively correlated with the relative content of functional groups in the soil with 0.4 g/kg GO (E2). The artificial application of GO to the soil can be used as an effective way to improve the effect of E. purpurea in the remediation of Cd soil pollution, and it has great application potential in the stabilization of plants and vegetations and restoration of high-concentration Cd-contaminated soil.

Effects of Contaminated Soil on the Survival and Growth Performance of European (Populus tremula L.) and Hybrid Aspen (Populus tremula L. × Populus tremuloides Michx.) Clones Based on Stand Density

This study was conducted to assess the survival rates, growth, and chlorophyll fluorescence (Fv/Fm) of four hybrid aspen (14, 191, 27, 291) and two European aspen (R3 and R4) clones cultivated in creosote- and diesel oil-contaminated soil treatments under three different plant densities: one plant per pot (low density), two plants per pot (medium density), and six plants per pot (high density) over a period of two years and three months. Evaluating the survival, growth, and Fv/Fm values of different plants is a prerequisite for phytoremediation to remediate polluted soils for ecological restoration and soil health. The results revealed that contaminated soils affected all plants’ survival rates and growth. However, plants grown in the creosote-contaminated soil displayed a 99% survival rate, whereas plants cultivated in the diesel-contaminated soil showed a 22−59% survival rate. Low plant density resulted in a higher survival rate and growth than in the other two density treatments. In contrast, the medium- and high-density treatments did not affect the plant survival rate and growth to a greater extent, particularly in contaminated soil treatments. The effects of clonal variation on the survival rate, growth, and Fv/Fm values were evident in all treatments. The results suggested that hybrid aspen clones 14 and 291, and European aspen clone R3 were suitable candidates for the phytoremediation experiment, as they demonstrated reasonable survival rates, growth, and Fv/Fm values across all treatments. A superior survival rate for clone 291, height and diameter growth, and stem dry biomass production for clone 14 were observed in all soil treatments. Overall, a reasonable survival rate (~75%) and Fv/Fm value (>0.75) for all plants in all treatments, indicating European aspen and hybrid aspen have considerable potential for phytoremediation experiments. As the experiment was set up for a limited period, this study deserves further research to verify the growth potential of different hybrid aspen and European aspen clones in different soil and density treatment for the effective phytoremediation process to remediate the contaminated soil.

Plant Growth and Nutrient Composition of Shrub and Arbor Willows Grown in Cu-Contaminated Flooded Soil

Flooding can adversely worsen metal-contaminated soil and influence phytoremediation efficiency; thus, it is crucial to explore the eco-physiological responses of plants to the combined stress of metals and flooding. Here, the plant growth, photosynthesis, and nutrient composition in the arbor willow (Salix jiangsuensis ‘J172’) and shrub willow (Salix integra ‘Yizhibi’) were studied using a pot experiment with Cu-contaminated soil (239.5 mg·kg−1) under flooded versus non-flooded conditions. S. integra showed a larger bioconcentration factor (BCF) than S. jiangsuensis in both treatments. Flooding markedly decreased the BCFs while obviously increasing the translocation factor in the two willows (p< 0.05). Flooding enhanced the leaf C:P and N:P ratios while significantly decreased root C:P and N:P ratios, compared to the non-flooded condition. The shrub willow exhibited better tolerance to flooding, with little alteration in biomass and photosynthetic rate, and showed greater potential Cu accumulation capacity, even though its total biomass was significantly lower than that of the arbor willow. Our study also helps further understanding of nutrient balance and stoichiometry of willows in response to flooding and Cu contamination, promoting the management of Cu-contaminated flooded soils.

Assessment of the antioxidative response and culturable micro-organisms of Lygeum spartum Loefl. ex L. for prospective phytoremediation applications

Abundant plant species in arid industrial areas are mining phyto-resources for sustainable phyto-management. However, the association with their rhizosphere is still poorly known for phytoremediation purposes. This study aims to assess the heavy metals (HMs) and metalloids uptake of Lygeum spartum Loefl. ex L. growing in cement plant vicinity and screen associated culturome for potential phytoremediation use. Bioaccumulation factor (BAF), the translocation factor (TF), and the mobility ratio (MR) were studied along with four sites. Lipid peroxidation (MDA), free proline (Pro), Non-protein thiols (NPTs), and reduced glutathione (GSH) were tested for evaluating the plant antioxidative response. Bacteria and fungi associated with L. spartum Loefl. ex L. were identified by 16S rRNA and fungal internal transcribed spacer (ITS1-ITS2) gene sequencing. Our results showed an efficient uptake of As, Pb, and Zn and enhanced GSH (0.34 ± 0.03) and NPTs (528.7 ± 14.4 nmol g^-1 FW) concentrations in the highly polluted site. No significant variation of Arbuscular Mycorrhizal Fungi (AMF) was found. Among 29 bacterial isolates, potential bioremediation were Bacillus simplex and Bacillus atrophaeus. Thus, L. spartum Loefl. ex L. and its associated microbiota have the potential for phytoremediation applications. Novelty statement: This work has been set in line with the investigation of the integrative biology of Lygeum spartum Loefl ex L. and the screening of its associated microbiome for potential phytoremediation applications. This work is the first work conducted in a cement plant vicinity investigating the associated fungi and bacteria of L. spartum Loefl. ex L. and been part of a sectorial research project since 2011, for assessing the impact of industrial pollution and recognizing the accumulation potential of plant species for further phyto-management applications.

Phytoextraction and recovery of rare earth elements using willow (Salix spp.)

Soil and water contaminations are caused by rare earth elements (REEs) due to mining and industrial activities, that threaten the ecosystem and human health. Therefore, phytoremediation methods need to be developed to overcome this problem. To date, little research has been conducted concerning the phytoremediation potential of Salix for REEs. In this study, two Salix species (Salix myrsinifolia and Salix schwerinii) and two Salix cultivars (Klara and Karin) were hydroponically exposed to different concentrations of six-REE for 4 weeks. The treatments were: T1 (Control: tap water), T2 (La: 50 mg/L) and T3 (La 11.50 + Y 11 + Nd 10.50 + Dy 10 + Ce 12 and Tb 11.50 in mg L^-1). The effects of the REE on Salix growth indicators (height, biomass, shoot diameter and root length), concentrations of REE in the produced biomass, and accumulation of REE in different parts of the Salix (stem, root, and leaf) tissues, were determined. In addition, the retention of REE in ashes following Salix combustion (800 and 1000 °C) was determined. The result indicates that with La and REE exposure, the height growth, dry biomass, shoot diameter and root length of all Salix remained equivalent to the control treatment excluding Klara, which displayed relatively higher growth in all parameters. Further, among the REE studied, the highest La concentration (8404 μg g^-1 DW) and La accumulation (10,548 μg plant^-1) were observed in Karin and Klara root respectively. Translocations and bioconcentration factors were discovered at <1 for all Salix, which indicates their phytostabilization potential. The total REE concentrations in bottom ashes varied between 7 and 8% with retention rates between 85 and 89%. This study demonstrates that Salix are suitable candidates for REE phytostabilization and the remediation of wastewater sites to limit metals percolating to the water layers in the ecosystem.

Study on the physicochemical properties changes of field aging biochar and its effects on the immobilization mechanism for Cd2+ and Pb2

It has been widely reported that biochar can be used as a cost-effective amendment to immobilize of heavy metal contaminants in soil. While less research has been conducted on effect of biochar long-term field aging on its properties and the adsorption capability. In this study, the characteristics of aged biochar were investigated by comprehensive characterization to elucidate its mechanism transformation for heavy metal immobilization. Our results showed that, compared to fresh biochar, the relative content of C of aged biochar was reduced by 34.12%, while O was increased by 8.79%. Additionally, the specific surface area, pore volume, pore size and oxygen-containing functional groups of aged biochar were significantly increased compared to the fresh biochar. Batch adsorption experiment indicated that the maximum adsorption for Cd2+ (Qm = 32.157 mg/g) and Pb2+ (Qm = 39.216 mg/g) on aged biochar surface was much larger than that of Cd2+ (Qm = 7.573 mg/g) and Pb2+ (Qm = 8.134 mg/g) on fresh biochar. The underlying adsorption mechanisms for Cd2+ and Pb2+ on fresh biochar were dominated by coprecipitation, cation exchange and cation-π interaction, whereas surface complexation and cation exchange appeared to be more vital for aged biochar, as more active adsorption sites and Oxygen-containing functional groups were formed on its surface during aging, which was well explained by BET, XPS, FTIR and Elemental Analysis. Our study found that the physicochemical properties of biochar changed significantly during field aging. Although these changes increased the adsorption of heavy metals by biochar, the reduced stability of biochar to passivated heavy metal ions.

Recent Developments in Microbe-Plant-Based Bioremediation for Tackling Heavy Metal-Polluted Soils

Soil contamination with heavy metals (HMs) is a serious concern for the developing world due to its non-biodegradability and significant potential to damage the ecosystem and associated services. Rapid industrialization and activities such as mining, manufacturing, and construction are generating a huge quantity of toxic waste which causes environmental hazards. There are various traditional physicochemical techniques such as electro-remediation, immobilization, stabilization, and chemical reduction to clean the contaminants from the soil. However, these methods require high energy, trained manpower, and hazardous chemicals make these techniques costly and non-environment friendly. Bioremediation, which includes microorganism-based, plant-based, microorganism-plant associated, and other innovative methods, is employed to restore the contaminated soils. This review covers some new aspects and dimensions of bioremediation of heavy metal-polluted soils. The bioremediation potential of bacteria and fungi individually and in association with plants has been reviewed and critically examined. It is reported that microbes such as Pseudomonas spp., Bacillus spp., and Aspergillus spp., have high metal tolerance, and bioremediation potential up to 98% both individually and when associated with plants such as Trifolium repens, Helianthus annuus, and Vallisneria denseserrulata. The mechanism of microbe's detoxification of metals depends upon various aspects which include the internal structure, cell surface properties of microorganisms, and the surrounding environmental conditions have been covered. Further, factors affecting the bioremediation efficiency and their possible solution, along with challenges and future prospects, are also discussed.

Co-planting of Quercus nuttallii, Quercus pagoda with Solanum nigrum enhanced their phytoremediation potential to multi-metal contaminated soil

To screen the efficient tree-herb co-planting patterns to remediate the heavy metal polluted soil, a greenhouse experiment was conducted for 150 days to examine the plant growth and metals accumulation across three co-planting patterns, including Solanum nigrum (S) co-planted with Quercus nuttallii (NS) or Quecrus pagoda (PS), and those three species are co-planted together (NPS). Results showed that the NPS pattern slightly decreased the tree biomass, while NS and PS treatments improved the plant growth (1.51-10.68%). It is worth noting that the NS treatment significantly (p < 0.05) increased photosynthetic pigment content (82.61-113.93%), net CO₂ assimilation (21.44%), and the uptake of Cd (44.58%) in Q. nuttallii; the PS treatment significantly (p < 0.05) increased the net CO₂ assimilation (8.61%) and the uptake of Cd (42.23%), Zn (31.18%) in Q. pagoda; and the uptake of Cd and Zn in the NPS co-planting treatment were only slightly increased. For S. nigrum, the photosynthetic pigment content was elevated and the metal accumulation in itself also maintained the relative stable in all the co-planting treatments. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate heavily polluted soil by heavy metals. Novelty statement: Co-planting with multiple plant species, as a novel strategy, has great value for the remediation of heavy metal contaminated soil. The paper aimed to explore the suitable co-planting pattern of Quercus, arbor trees which showed phytoremediation potential, co-planted with Cd hyperaccumulator, Solanum nigrum. The result suggested the co-planting with S. nigrum enhanced the plant growth, photosynthesis, and metals extraction of Q. nuttallii and Q. pagoda. Co-planting also improved ecological adaptation of S. nigrum via elevating pigment content. Thus, co-planting of Quercus with S. nigrum was a promising way to remediate polluted soil.

The effect of particle size of bamboo biochar on the phytoremediation of Salix psammophila C. to multi-metal polluted soil

Biochar shows great potential in soil remediation. The benefits of biochar on soil depend onits intrinsic properties and soil characteristics. However, the influence of particle sizes of biochar on soil remediation is not clear. In a pot experiment, we evaluated the effects of bamboo biochar (BBC) particle sizes (P1 < 0.15 mm, 0.15 mm < P2 < 0.25 mm, 0.25 mm < P3 < 0.50 mm) on phytoremediation efficiency of Salix psammophila C. cultivated in multi-metal polluted soil. We added the BBC at 3% (w/w) in tested soil. Next, the BBC was thoroughly mixed with soil and weighting to the pot, and S. psammophila cuttings were planted and grown for six months in the amended soil under model growth condition.Results revealed the addition of different sizes of BBC particles affected soil quality, plant growth, and HMs accumulation in plants. All sizes of BBC treatments improved Cd and Zn accumulation, whereas plants in P2 treatment showed the greatest accumulation, increased by 52.41 and 25.55% compared with the control (1,503 and 19,928 μg·plant^-1). Overall, the results indicated BBC enhanced the phytoremediation efficiency of S. psammophila. Plants cultivated in P2 treatment showed the most significant effect on remediating contaminated soil.