Contaminated Mine Soils Research Articles

Rehabilitation of mine soils by phytostabilization: Does soil inoculation with microbial consortia stimulate Agrostis growth and metal(loid) immobilization?

Metal(loid) soil pollution resulting from mining activities is an important issue that has negative effects on the environment (soil acidification, lack of vegetation, groundwater pollution) and human health (cancer, chronic diseases). In the context of a phytostabilization process for the bioremediation of a mine soil highly contaminated by arsenic (As) and lead (Pb), a pot experiment was set up to study the effect of plant sowing and microbial inoculation on soil properties, metal(loid) (im)mobilization in soil and accumulation in plant, and plant growth. For this, mine soil was sown with endemic metallicolous Agrostis seeds and/or inoculated with endogenous microbial consortia previously selected for their As and Pb tolerance. Agrostis was able to develop on the contaminated mine soil and immobilized metal(loid)s through metal(loid) accumulation in the roots. Its growth was improved by microbial consortium inoculation. Moreover, microbial consortium inoculation increased soil organic content and electrical conductivity, and led to an increase in soil microbial activities (linked to C and P cycles); however, it also induced a metal(loid) mobilization. In conclusion, microbial consortium inoculation stimulated the growth of endemic Agrostis plants and thus ameliorated the phytostabilization of a former mine soil highly polluted by As and Pb. This study is thus a good example of the benefits of coupling several approaches such as phytostabilization and bioaugmentation for the bioremediation of former mine contaminated sites.

Differential response of Oryza sativa L. and Phragmites australis L. plants in trace elements contaminated soils under flooded and unflooded conditions.

Drastic changes in the water regime of trace elements (TEs) contaminated soils under semiarid conditions, from completely dry to flooding situations, may alter the solubility of the contaminants and, therefore, their potential mobility and availability to plants. Certain macrophyte species have shown a promising suitability for their use in the phytoremediation of TEs contaminated soils under fluctuating flooded-unflooded conditions, as a consequence of their high resistance and tolerance to contamination. Similarly, different water conditions occur during rice (Oryza sativa) cultivation, a species often used as a model plant for TEs toxicity studies. The aim of this work was to study the tolerance and oxidative response to TEs of common reed (Phragmites australis) and rice grown in contaminated mining soils, when exposed to different water saturation conditions. Both species (common reed and rice) were cultivated in three different contaminated soils from the Sierra Minera of La Unión-Cartagena (SE-Spain) under contrasting water saturation conditions (flooded and unflooded) in a pot experiment. Soil EC and elevated metal (mainly Cd and Zn) soluble concentrations conditioned the survival of the plants. Whereas, As accumulation in the aerial part of both species influenced the most oxidative stress homeostasis. Common reed showed to be a good candidate for its use in the phytostabilization of TEs contaminated soils under both flooded and unflooded conditions.

Effects of sheep bone biochar on soil quality, maize growth, and fractionation and phytoavailability of Cd and Zn in a mining-contaminated soil

Biochar prepared from various feedstock materials has been utilized in recent years as a potential stabilizing agent for heavy metals in smelter-contaminated soils. However, the effectiveness of animal bone-derived biochar and its potential for the stabilization of contaminants remains unclear. In the present study, sheep bone-derived biochar (SB) was prepared at low (500 °C; SBL) and high temperatures (800 °C; SBH) and amended a smelter-contaminated soil at 2, 5, and 10% (w/w). The effects of SB on soil properties, bioavailable Zn and Cd and their geochemical fractions, bacterial community composition and activity, and the response of plant attributes (pigments and antioxidant activity) were assessed. Results showed that the SBH added at 10% (SBH10) increased soil organic carbon, total nitrogen, and phosphorus, and also increased the oxidizable and residual Zn and Cd fractions at the expense of the bioavailable fractions. The SBH10 lowered the Zn and Cd contents in maize roots (by 57 and 60%) and shoot (by 42 and 61%), respectively, compared to unamended control. Additionally, SBH10 enhanced urease (98%) and phosphates (107%) activities, but reduced dehydrogenase (58%) and β-glucosidase (30%) activities. Regarding the effect of the pyrolysis temperature, SBH enhanced the activity of Acidobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Verrucomicrobia, Chlorobi, and Microgenomates, but reduced Actinobacteria and Parcubacteria in comparison to SBL. However, only the SBL10 reduced the Proteobacteria community (by 9%). In conclusion, SB immobilized Zn and Cd in smelter-affected soils, enhanced the bacterial abundance and microbial function (urease, phosphates), and improved plant growth. However, validation of the results, obtained from the pot experiment, under field conditions is suggested.

Effect of fertilization, carbon‐based material, and redmud amendments on the bacterial activity and diversity of a metal(loid) contaminated mining soil

AbstractSoil amendments can be used to improve phytoremediation of polluted soils. Little is known about the effects of single or combined amendment addition on the bacterial community. Two carbon‐based amendments, a biochar and an activated carbon, and two redmuds were applied to a lead and arsenic contaminated mine spoil Technosol, alone or in combinations. The bacterial community was evaluated using enzyme activities, Biolog EcoPlates, and next‐generation sequencing with reference to untreated soil and fertilized soil. Fertilization had a negative effect on the bacterial community diversity and activity. The two carbon‐based materials decreased β‐glucosidase activity but increased carbon‐related activity (Biolog EcoPlates) while the two redmuds increased the overall activity of the bacterial community. The combination of biochar and redmud increased both the diversity and activity of the bacterial community. All treatments induced a shift in the bacterial community structure. The treatments containing the neutralized redmud and/or biochar clustered together, whereas the treatments with nonprocessed redmud and activated carbon were closer to nonamended soil, while the bacterial community of the fertilization treatment was different from it. Treatments with biochar and/or neutralized redmud resulted in a similar community composition while the bacterial community of the treatments with activated carbon and nonprocessed redmud remained more similar to that of the nonamended technosol.

Response of maize to coniferous tree woods biochar and sheep manure application to contaminated mine soil

Metallic trace element (MTE) soil contamination is a serious problem needed to be urgently faced to ensure safe food supply and protect human health over the world. The present work is a potting experiment conducted using two levels of biochar (2.5%; 5%) and animal manure (10%; 20%) to investigate their potential role in soil improvement and development of maize seeds grown in a former iron mine soil. Results show that both amendments increased soil pH. A successful growth of maize has been observed in presence of both organic amendments. Plants were well developed with leaves which were large, green, and longer comparing to untreated contaminated soil suggesting that biochar and animal manure reduced physical symptoms of metal toxicity. Biochar and animal manure amendments increased almost all the measured morphological characteristics especially shoot length (biochar: 16.44 cm, animal manure: 18.26 cm, and untreated soil: 13.37cm) and dry biomass of shoots (biochar: 0.11 g, animal manure: 0.18g, and untreated soil: 0.05g) and roots (biochar: 0.29 g, animal manure: 0.17 g, and untreated soil: 0.16 g) as well as length and numbers of leaves and leaf area. However, more studies are needed to explore the amendment role on biochemical, physiological, and accumulation of MTE by maize.

Increase in Total Petroleum Hydrocarbons Removal Rate in Contaminated Mining Soil Through Bioaugmentation with Autochthonous Fungi During the Slow Bioremediation Stage

The removal of total petroleum hydrocarbons (TPHs) from contaminated mining soil was carried out under in vitro conditions. The aerobic consumption of TPH in the slow bioremediation stage via biostimulation with native microorganisms and biostimulation-bioaugmentation with autochthonous fungal isolates was evaluated. The initial TPH concentration was 70,880 ± 975 mg TPH/kg soil, soil was amended with nutrients at a C:N:P ratio of 100:15:1, the water content was adjusted to the soil field capacity, and batch microcosm reactors were incubated at room temperature (20.5 ± 3.1°C) for 90 days. The bioaugmentation process was tested using four hydrocarbonoclastic fungal strains isolated from the same contaminated mining soil individually and a mixed culture of the four isolates. The molecular characterization of the isolated fungi was based on sequence analysis of 18S rRNA, and the fungi were identified as Aspergillus niger MT786339.1, Aspergillus fumigatus MT786338.1, Aspergillus terreus MT786341.1, and Aspergillus flavus MT786340.1. The best TPH removal was achieved by inoculation with the fungal consortium (57 ± 1.97%) at 45 days (slow stage) after initiating the biostimulation process, followed by inoculation with Aspergillus niger (49 ± 1.2%), Aspergillus terreus (44 ± 0.67%), Aspergillus fumigatus (35 ± 0.98%), and Aspergillus flavus (32 ± 0.38%), while the degradation rate achieved with native microorganisms was only 21.6 ± 1.5%; statistical analysis of the results showed significant differences.

Bone-derived biochar improved soil quality and reduced Cd and Zn phytoavailability in a multi-metal contaminated mining soil.

Reusing by-products such as cow bones in agriculture can be achieved thorough pyrolysis. The potential of bone-derived biochar as a promising material for metals immobilization in contaminated mining soils has not yet been sufficiently explored. Therefore, cow bones were used as biochar feedstock were pyrolyzed at 500°C (CBL) and 800°C (CBH) and. The two biochars were applied to a mine contaminated soil at 0 (control), 2.5, 5 and 10%, w/w, dosages; then, the soils were incubated and cultivated by maize in the greenhouse. Cadmium (Cd) and zinc (Zn) bioavailability and their sequentially extracted fractions (acid soluble, reducible, oxidizable, and residual fraction), soil microbial function, and plant health attributes were analyzed after maize harvesting. Bone-derived biochar enhanced the content of dissolved organic carbon (up to 74%), total nitrogen (up to 26%), and total phosphorus (up to 27%) in the soil and improved the plant growth up to 55%, as compared to the control. The addition of CBL altered the acid soluble fraction of both metals to the residual fraction and, thus, reduced the content of Zn (55 and 40%) and Cd (57 and 67%) in the maize roots and shoots, respectively as compared to the control. The CBL enhanced the β-glucosidase (51%) and alkaline phosphatase activities (71%) at the lower doses (2.5-5%) as compared to control, while the activities of these enzymes decreased with the higher application doses. Also, CBL improved the antioxidants activity and maize growth at the 2.5-5% application rate. However, the activity of the dehydrogenase significantly decreased (77%), particularly with CBH. We conclude that CBL, applied at 2.5-5% dose, can be utilized as a potential low cost and environmental friendly amendment for stabilization of toxic metals in contaminated mining soils and producing food/feed/biofuel crops with lower metal content.

Green remediation of toxic metals contaminated mining soil using bacterial consortium and Brassica juncea.

Microorganism-assisted phytoremediation is being developed as an efficient green approach for management of toxic metals contaminated soils and mitigating the potential human health risk. The capability of plant growth promoting Actinobacteria (Streptomyces pactum Act12 - ACT) and Firmicutes (Bacillus subtilis and Bacillus licheniformis - BC) in mono- and co-applications (consortium) to improve soil properties and enhance phytoextraction of Cd, Cu, Pb, and Zn by Brassica juncea (L.) Czern. was studied here for the first time in both incubation and pot experiments. The predominant microbial taxa were Proteobacteria, Actinobacteria and Bacteroidetes, which are important lineages for maintaining soil ecological activities. The consortium improved the levels of alkaline phosphatase, β-D glucosidase, dehydrogenase, sucrase and urease (up to 33%) as compared to the control. The bacterial inoculum also triggered increases in plant fresh weight, pigments and antioxidants. The consortium application enhanced significantly the metals bioavailability (DTPA extractable) and mobilization (acid soluble fraction), relative to those in the unamended soil; therefore, significantly improved the metals uptake by roots and shoots. The phytoextraction indices indicated that B.juncea is an efficient accumulator of Cd and Zn. Overall, co-application of ACT and BC can be an effective solution for enhancing phytoremediation potential and thus reducing the potential human health risk from smelter-contaminated soil. Field studies may further credit the understanding of consortium interactions with soil and different plant systems in remediating multi-metal contaminated environments.

Streptomyces pactum addition to contaminated mining soils improved soil quality and enhanced metals phytoextraction by wheat in a green remediation trial

Streptomyces pactum (Act12), an agent of a gentle in situ remediation approach, has been recently used in few works in phytoextraction trials; however, the impact of Act12 on soil quality and metal phytoavailability has not been assessed in multi-metal contaminated soils. Consequently, here we assessed the potential impact of Act12 on the wheat (Triticum aestivum L.) growth, antioxidants activity, and the metal bioavailability in three industrial and mining soils collected from China and contained up to 118, 141, 339, and 6625 mg Cd, Cu, Pb, and Zn kg−1 soil, respectively. The Act12 was applied at 0 (control), 0.75 (Act-0.75), 1.50 (Act-1.5), and 2.25 (Act-2.25) g kg−1 (dry weight base) to the three soils; thereafter, the soils were cultivated with wheat (bio-indicator plant) in a pot experiment. The addition of Act12 (at Act-1.5 and Act-2.25) promoted wheat growth in the three soils and significantly increased the content of Cd, Cu, and Zn in the roots and shoots and Pb only in the roots (up to 121%). The Act12-induced increase in metals uptake by wheat might be attributed to the associated decrease in soil pH and/or the increase of metal chelation and production of indole acetic acid and siderophores. The Act12 significantly decreased the antioxidant activities and lipid peroxidation in wheat, which indicates that Act12 may mitigate metals stress in contaminated soils. Enhancing metals phytoextraction using Act12 is a promising ecofriendly approach for phytoremediation of metal-contaminated mining soils that can be safely utilized with non-edible plants and/or bioenergy crops.

Immobilization persistence of Cu, Cr, Pb, Zn ions by the addition of steel slag in acidic contaminated mine soil

Adding steel slag to the acidic contaminated mine soil can immobilize heavy metal ions, but immobilization persistence of the metal ions needs to be determined. In this study, dynamic column simulation experiments were set up to compare the immobilization persistence of Cu, Cr, Pb and Zn ions in original soil and with the addition of slag, lime or fly ash to the soil during a simulated 36-month of acid rain leaching. After adding slag and lime, the pH, organic matter content and cation exchange capacity of soil were significantly increased. Compared with the original soil, additions of slag and lime to the soil were able to persistently immobilize the metal ions, whereas fly ash additions had little effect. During simulation, the metal ion concentrations in the slag group leaching solution were essentially consistent with Standard IV for groundwater. The metal ions were immobilized to form instable hydroxides and stable fractions following adding slag to soil. The hydroxide could rerelease metal ions by acid rain leaching, part of which were re-immobilized into stable fractions by entering slag lattice and complexing with soil organic matter. Therefore, adding slag to soil can persistently immobilize metal ions for heavy metal-contaminated acidic mine soil.

Influence of Biochar Particle Size and Concentration on Pb and As Availability in Contaminated Mining Soil and Phytoremediation Potential of Poplar Assessed in a Mesocosm Experiment

Metal(loid)s found at many sites as a result of human activities induce contamination of ecosystems, which threatens the environment and public health. Several approaches can be used in order to reduce such negative impacts of pollutants, and among them, phytoremediation has gained attractive attention. The objective of the present study was to assess the capacity of Populus euramericana, Dorskamp cultivar, for the phytoremediation of metal(loid)s on a technosol (former mining site) highly contaminated mainly with Pb and As, and amended with biochars having different particle sizes. In a 46-day mesocosm glasshouse pot experiment, technosol was mixed at three ratios (0, 2, or 5% w/w) with four different hardwood-derived biochars (with various particle sizes) in order to study the biochar application rate and particle size effects on soil pore water (SPW) characteristics, on poplar growth, and on metal(loid) distribution and concentrations in the plant organs. The results showed that all biochars tested had a significant impact on several SPW physico-chemical parameters. Especially, biochar additions reduced available Pb concentrations but with no effect on As. In such conditions, Populus growth in amended technosol increased whatever rate and particle size of biochar used. Metal(loid) concentrations and repartition in plant organs showed the following: (1) for Pb, a higher root concentration with low aerial part translocation, which depended on biochar used, and (2) for As, mainly a root sequestration. We identified biochar with the finest particle size and combined with P. euramericana, Dorskamp, was the most suitable as remediation tools for Pb stabilization in post-mining contaminated soils.

Evaluation of Metal Tolerance of Fungal Strains Isolated from Contaminated Mining Soil of Nanjing, China.

Simple SummaryIn this study, cadmium, chromium, and lead tolerant microbes have been isolated from contaminated mining soil and characterized. Molecular characterization of isolated fungi was performed and amplified sequences were deposited in the GenBank NCBI database. Metal tolerance of the various strains has been determined by measuring the minimum inhibitory concentrations (MICs) and the tolerance indexes of all the tested strains against Cd, Cr, and Pb. Bioaccumulation capacities of Trichoderma harzianum and Komagataella phaffi have also been assessed. These findings helped us find a novel strain of Komagataella phaffi and suggested it to be the potential mycoremediation microbe to alleviate the contamination of Cd, Cr, and Pb. Future studies of this fungal strain can help us to understand its resistance mechanism against other heavy metals, too.Rapidly increasing industry has resulted in greater discharge of hazardous chemicals in the soil. In the current study, soil samples were collected from Nanjing mine (32°09′19.29″ N 118°56′57.04″ E) and subjected to heavy metal analysis and microbe isolation. A total of 460 fungi were isolated, and five of these were yeast strains. Most of the strains exhibited tolerance to one metal. Five multimetal tolerant strains were selected and identified as Aspergillus sclerotiorum, Aspergillus aculeatus, Komagataella phaffii, Trichoderma harzianum, and Aspergillus niger. Isolated strains were grown in high concentrations of cadmium (Cd), chromium (Cr) and lead (Pb), for induced-tolerance training. The tolerance index (TI) revealed the highest Cd tolerance of novel K. phaffii strain at 5500 ppm (TI: 0.2). K. phaffii also displayed resistance at 4000 ppm against Cr (TI: 0.32) and Pb (TI: 0.32). In contrast, tolerance training for A. niger was not that successful. K. phaffii also displayed the highest bioaccumulation capacity for Cd (25.23 mg/g), Cu (21.63 mg/g), and Pb (20.63 mg/g) at 200 ppm. Scanning electron microscopy (SEM) explored the morphological changes in the mycelia of stressed fungi. Results of this study describe this delicate approach to be species and metal dependent and suggest a potential utilization of this fungal strain for the bioremediation of contaminated soils.

Potential of Eucalyptus globulus for the phytoremediation of metals in a Moroccan iron mine soil-a case study.

The contamination left by abandoned mines demands sustainable mitigation measures. Hence, the aim of this study was to examine the phytoremediator ability of Eucalyptus globulus Labill. to be used for cleaning up metal-contaminated soils from an African abandoned iron (Fe) mine (Ait Ammar, Oued Zem, Morocco). Plantlets of this species were exposed to a control (CTL), a reference (REF), and a mine-contaminated soil (CS). Morphological (growth, leaf area) and physiological stress biomarkers (photosynthetic efficiency, pigments content, leaf relative water, and malondialdehyde (MDA) levels) and metal bioaccumulation were assessed. The growth and leaf area of E. globulus increased overtime in all soils, although at a lower rate in the CS. Its photosynthetic efficiency was not markedly impaired, as well as MDA levels decreased throughout the experiment in CS. In this soil, higher metal contents were detected in E. globulus roots than in leaves, especially Fe (roots: 15.98-213.99 μg g-1; leaves: 5.97-15.98 μg g-1) and Zn (roots: 1.64-1.99 μg g-1; leaves: 0.67-1.19 μg g-1), indicating their reduced translocation. Additionally, though at low extent, the plants bioaccumulated some metals (Pb > Zn > Cu) from CS. Overall, E. globulus may be potentially used for the phytoremediation of metals in metal-contaminated soils.

Evaluation of Different Amendment Combinations Associated with Trifolium repens to Stabilize Pb and As in a Mine-Contaminated Soil

Assisted phytoremediation using amendments is a cost-effective and environmentally friendly approach to control soil pollution. However, amendment type, combination and application rate can influence process effectiveness. In the present study, the effect of the association of red mud and carbon-based amendments on the physicochemical properties of a former mine soil as well as the growth and metal(loid) uptake of Trifolium repens was investigated. For this purpose, a mesocosm experiment was set up using a former mine technosol highly contaminated by As and Pb, amended with red mud combined with different carbon-based amendments, i.e., bamboo biochar, oak biochar, steam activated carbon and acidic activated carbon, and sown with Trifolium repens. The final goal was to determine which amendment combination allows soil metal(loid) immobilization and an efficient plant growth. Results showed that all the four different treatments improved soil characteristics by increasing pH and electrical conductivity and reducing redox potential. All the treatments were also effective in reducing soil pore water lead concentrations. Among the four treatments, the addition of red mud and acidic activated carbon in the soil showed better results regarding Trifolium repens growth. Finally, when grown on the soil amended with red mud and acidic activated carbon, Trifolium repens presented mainly a metal(loid) storage in roots, making it a right candidate for the establishment of a vegetation cover.

Foliar Application of SiO2 Nanoparticles Alters Soil Metabolite Profiles and Microbial Community Composition in the Pakchoi (Brassica chinensis L.) Rhizosphere Grown in Contaminated Mine Soil.

Silica nanoparticles (SiO2-NPs) are promising in nanoenabled agriculture due to their large surface area and biocompatible properties. Understanding the fundamental interaction between SiO2-NPs and plants is important for their sustainable use. Here, 3 week-old pakchoi (Brassica chinensis L.) plants were sprayed with SiO2-NPs every 3 days for 15 days (5 mg of SiO2-NPs per plant), after which the phenotypes, biochemical properties, and molecular responses of the plants were evaluated. The changes in rhizosphere metabolites were characterized by gas chromatography-mass spectrometry (GC-MS)-based metabolomics, and the response of soil microorganisms to the SiO2-NPs were characterized by high-throughput bacterial 16S rRNA and fungal internal transcribed spacer (ITS) gene sequencing. The results showed that the SiO2-NP spray had no adverse effects on photosynthesis of pakchoi plants nor on their biomass. However, the rhizosphere metabolite profile was remarkably altered upon foliar exposure to SiO2-NPs. Significant increases in the relative abundance of several metabolites, including sugars and sugar alcohols (1.3-9.3-fold), fatty acids (1.5-18.0-fold), and small organic acids (1.5-66.9-fold), and significant decreases in the amino acid levels (60-100%) indicated the altered carbon and nitrogen pool in the rhizosphere. Although the community structure was unchanged, several bacterial (Rhodobacteraceae and Paenibacillus) and fungal (Chaetomium) genera in the rhizosphere involved in carbon and nitrogen cycles were increased. Our results provide novel insights into the environmental effects of SiO2-NPs and point out that foliar application of NPs can alter the soil metabolite profile.

Evaluation of Cynara cardunculus L. and municipal solid waste compost for aided phytoremediation of multi potentially toxic element\u2013contaminated soils

The suitability for aided phytoremediation of Cynara cardunculus L. var. altilis and municipal solid waste compost (MSWC) applied at 2% and 4 % rates was evaluated in a multi potentially toxic element (PTE)-contaminated mining soil (Pb ~ 15,383 mg kg−1, Zn ~ 4076 mg kg−1, As ~ 49 mg kg−1, Cd ~ 67 mg kg−1, Cu ~ 181 mg kg−1, and Sb ~ 109 mg kg−1). The growth of C. cardunculus significantly increased with compost amendment and followed the order: MSWC-4% > MSWC-2% > Control. PTE concentrations in the roots of plants grown on amended soils decreased compared with control plants (i.e., less than ~ 82, 94, and 88% for Pb, Zn, and Cd respectively). PTE translocation from roots to shoots depended on both PTE and amendment rate but values were generally low (i.e., < 1). However, PTE mineralomasses were always higher for plants grown on MSWC-amended soils because of their higher biomass production, which favored an overall PTE bioaccumulation in roots and shoots. After plant growth, labile As and Sb increased in amended soils, while labile Pb, Zn, Cu, and Cd significantly decreased. Likewise, dehydrogenase and urease activities increased significantly in planted soils amended with MSWC. Also, the potential metabolic activity and the catabolic versatility of soil microbial communities significantly increased in planted soils amended with MSWC. Overall, our results indicate that C. cardunculus and MSWC can be effective resources for the aided phytoremediation of multi PTE-contaminated soils.

Isolation and Characterization of Pseudomonas sp. Cr13 and Its Application in Removal of Heavy Metal Chromium.

The purpose of this study was to elaborate the characteristics of Pseudomonas sp. Cr13, including physiological and biochemical characteristics, optimization of growth conditions, minimum inhibitory concentration of Cr6+ and resistance to other heavy metals, removal efficiency of Cr6+, and antibiotics sensitivity. A strain Pseudomonas sp. Cr13 was screened from mine-contaminated soils, which could tolerate high concentration of Cr6+ (up to 250mgl-1) and Cd2+ (50mgl-1). The optimum pH, NaCl concentration, and temperature for growth were 6, 10% NaCl, and 30°C, respectively. The removal efficiency of Cr6+ by strain Pseudomonas sp. Cr13 was studied. The removal efficiency of Cr6+ decreased with the increased concentration of Cr6+. Under the optimal conditions, the maximum of the removal rate can reach up to 94.26% in contaminated soils. In addition, antibiotics sensitivity of this strain was investigated. It was found that this strain was sensitive to nine types of antibiotics, which would lay a good foundation for the choice of selective marker in genetic engineering modification of this strain. The results in this article would lay a good foundation for the bioremediation of heavy metals pollution in the future. Pseudomonas sp. Cr13 can tolerate high concentration of Cr6+ and partially remove Cr6+, which make Cr13 an attractive option for the bioremediation of heavy metal chromium (Cr). Our findings suggest that Pseudomonas sp. Cr13 is a potential bacterium with the ability of bioremediation of heavy metal Cr.

Fe/Mn- and P-modified drinking water treatment residuals reduced Cu and Pb phytoavailability and uptake in a mining soil

Management of industrial hazardous waste is of great concern. Recently, aluminum rich drinking water treatment residuals (Al-WTR) received considerable attention as a low-cost immobilizing agent for toxic elements in soils. However, the suitability and effectiveness of modified Al-WTR as stabilizing agent for toxic metals such as Cu and Pb in mining soil is not assessed yet. We examined the impact of different doses (0, 0.5, 1.5, and 2.5%) of raw and Fe/Mn- and P- modified Al-WTR on the bioavailability and uptake of Cu and Pb by ryegrass in Cu and Pb contaminated mining soil. The addition of Fe/Mn-and P- modified Al-WTR to the soil reduced significantly the concentrations of Pb (up to 60% by Fe/Mn-Al-WTR and 32% by P-Al-WTR) and Cu (up to 45% by Fe/Mn-Al-WTR and 18% by P-Al-WTR) in the shoots and roots of ryegrass as compared to raw Al-WTRs and untreated soil. Our results demonstrate that modification of the raw Al-WTR increased its pH, CEC, specific surface area, active functional groups (Fe-O and Mn-O), and thus increased its immobilization efficiency. Our results highlight the potential of the modified Al-WTR, particularly the Fe/Mn-Al-WTR, for the remediation of Cu and Pb contaminated soils and recommend field scale verification.

Use of Brassica juncea and Dactylis glomerata for the phytostabilization of mine soils amended with compost or biochar

Phytostabilization of mine soils contaminated by potentially toxic elements (PTEs) requires plants tolerant to PTE toxicity and to the poor soil physico-chemical characteristics of these areas. A pot experiment was carried out to assess the phytostabilization potential of Brassica juncea and Dactylis glomerata in mine soils amended with compost and biochar. Furthermore, the Environmental Risk of the soils and the effects of the phytostabilization process on the microbiological population size and activity in the soils were also determined. According to the Ecological Risk Index (ERI) the soils studied presented “very high risk” and As, Cd and Pb were the target elements for phytostabilization. Both amendments improved soil conditions (e.g., increasing total-N and total organic-C concentrations) and contributed to PTE (Cd, Pb and Zn) immobilization in the soil. Compost showed a more marked effect on soil microbial biomass and nutrients release in soil, which led to higher B. juncea and D. glomerata biomass in compost treated soils. Biochar treatment showed a positive effect only on D. glomerata growth, despite it provoked strong PTE immobilization in both soils. The addition of both amendments resulted in an overall reduction of PTE concentration in the plants compared to the control treatment. In addition, both plant species showed higher accumulation of PTE in the roots than in the shoots (transfer factor<1) independently of the treatment received. Therefore, they can be considered as good candidates for the phytostabilization of PTE contaminated mine soils in combination with organic amendments like biochar and compost.

Performance of Streptomyces pactum-assisted phytoextraction of Cd and Pb: in view of soil properties, element bioavailability, and phytoextraction indices.

Microbe-assisted phytoremediation provides an eco-friendly and cost-effective approach to reclaim Cd- and Pb-contaminated soils. In this work, incubation and pot experiments were established to investigate the effect of Streptomyces pactum (Act12) combined with compost on soil physicochemical properties, enzymatic activities, and thereby acted on phytoextraction of Cd and Pb by using potherb mustard (Brassica juncea Coss.). The addition of Act12 and compost increased EC (7.2%), available phosphorus (P) (14.9%), available potassium (K) (17.0 folds), DOC (37.7%), OM (2.8 folds), urease (49.8%), dehydrogenase (2.2 folds), and alkaline phosphatase (23.0 folds) of soil, while reduced pH (7.7%) compared with control. Significant decrease of available Cd and Pb uptake was observed after adding compost and Act12 by 29.1% and 32.2%. Presence of compost and Act12 enhanced the biomass by 3.98 folds and 1.83 folds in shoots and roots of plant. Results showed the assimilation of Cd and Pb in shoots was increased by 103.8% and 48.7% due to the increased of biomass. Meanwhile, the rhizosphere effect of soil microorganisms increased the uptake of Cd (60.4%) and Pb (19.2%) in roots. These findings suggested that Act12 joined with compost-strengthened potherb mustard phytoremediation of Cd- and Pb-polluted soils, which may provide new insights into the clean-up of mining-contaminated soils in field practice.