The present study was aimed at determining the efficacy of rock phosphate (RP) 3% loaded in a green coconut shell, chicken manure, and vegetable waste to make green coconut-modified biochar (GMB), ...chicken manure modified-biochar (CMB), and vegetable waste-modified biochar (VMB) in the fixation of Cr, Pb, Cu, Zn, Ni, and Cd in Sharafi goth and Malir polluted soils. The impact of RP impregnated with organic waste material to produce modified biochars (MBs) on stabilizing PTEs from polluted soils and reducing their uptake by mustard plant has not yet been thoroughly investigated. All modified BCs in 0.5, 1, and 2% doses were used to stabilize Cr, Pb, Cu, Zn, Ni, and Cd in two polluted soils and to reduce their uptake by the mustard plant. The obtained results revealed that the maximum mustard fresh biomass was 17.8% higher with GMB 1% in Sharafi goth polluted soil and 25% higher with VMB 0.5% in Malir polluted soil than in the control treatment. After applying modified BCs, immobilization of Cr, Pb, Cu, Ni, and Cd was observed in both soils and it reduced the uptake of these elements by mustard plants. On the other hand, although Zn mobilization increased by 0.38% for CMB 0.5% and by 5.9% for VMB 0.5% in Sharafi goth polluted soil, as well as by 3.15% for GMB 1%, 6.34% for GMB 2%, and 4.78% for VMB 0.5% in Malir polluted soil, this was due to changes in soil pH and OM. It was found that GMB 1%, CMB 0.5%, and VMB 0.5% have the potential to increase Zn uptake by mustard, while VMB 2% can reduce the element uptake by the plant. Redundancy analysis showed that soil chemical parameters were negatively correlated with PTEs in both soils and reduced their uptake by mustard. The present study revealed that MBs can stabilize PTEs in industrial and wastewater soils polluted with multiple metals and reduce their uptake by plants.
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•Impact of rock phosphate-modified biochars on the fixation of PTEs in two soils was investigated.•Modified biochars potentially stabilize PTEs in both polluted soils.•Modified biochars clearly reduced the uptake of PTEs by mustard plant.•Changes in fresh and dry biomasses of mustard were observed after applying modified biochars.•Long-term ex-situ trials must be conducted to assess the potential of different modified biochars.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Earthworm (EW) for remediation of toxic elements (TE) contaminated soil is reviewed.•The influence of TEs on EW abundance in contaminated soils is discussed.•Factors affecting TEs ...accumulation and elimination by EW have been summarized.•Dynamics and fates of TEs in EW-amended soils are critically discussed.•The review elucidates EW potentials for risk mitigation in contaminated soil.
Global concerns towards potentially toxic elements (PTEs) are steadily increasing due to the significant threats that PTEs pose to human health and environmental quality. This calls for immediate, effective and efficient remediation solutions. Earthworms, the 'ecosystem engineers', can modify and improve soil health and enhance plant productivity. Recently, considerable attention has been paid to the potential of earthworms, alone or combined with other soil organisms and/or soil amendments, to remediate PTEs contaminated soils. However, the use of earthworms in the remediation of PTEs contaminated soil (i.e., vermiremediation) has not been thoroughly reviewed to date. Therefore, this review discusses and provides comprehensive insights into the suitability of earthworms as potential candidates for bioremediation of PTEs contaminated soils and mitigating environmental and human health risks. Specifically, we reviewed and discussed: i) the occurrence and abundance of earthworms in PTEs contaminated soils; ii) the influence of PTEs on earthworm communities in contaminated soils; iii) factors affecting earthworm PTEs accumulation and elimination, and iv) the dynamics and fate of PTEs in earthworm amended soils. The technical feasibility, knowledge gaps, and practical challenges have been worked out and critically discussed. Therefore, this review could provide a reference and guidance for bio-restoration of PTEs contaminated soils and shall also help developing innovative and applicable solutions for controlling PTEs bioavailability for the remediation of contaminated soils and the mitigation of the environment and human risks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tomato wilt disease, caused by the
Fusarium oxysporum
is an ever-increasing threat for agricultural production, and unreasonable fertilization and pesticide abuse caused environmental challenge. ...Increasing evidence suggested that microbiomes or those associated with crops, played key roles on plant health. Plant disease dynamics were affected by multiple biotic and abiotic factors including phytopathogen population density, the genetic type of the pathogen and the host, in particular, the composition and assembly of the host-associated microbiome. However, it was unclear how pathogen invasion interaction and correlate with endophytic bacterial communities in natural field conditions. To study this, we sampled temporally the tomato plants that were exposed to
F. oxysporum
invasions over one crop season. High-throughput sequencing were performed to explore the correlation between agricultural practice, pathogen invasion, and endophytic microbiota communities. Results showed that pathogen invasion had clear effect on the endophytic and a strong link between increased pathogen densities and reduced abundance of
Bacillus
sp., which are crucial taxonomy for suppressiveness to
F. oxysporum in vitro
and in greenhouse condition. In summary, monitoring the dynamics of endophytic bacteria communities and densities of pathogen could thus open new avenue for more accurate disease diagnostics and high-efficiency screening antagonisms methods in the future, and our results will broaden the agricultural view of beneficial microbiota as biological control agents against plant pathogen.
In this study, a novel MgO-biochar composite was generated for nutrient recovery from biogas slurry using magnesium chloride (MgCl
2
) and ammonia hydroxide (NH
3
·H
2
O). Biochar properties, ...including pH, CEC, pHpzc, magnesium content, surface area, and total pore volume (
V
total
), were evaluated. Moreover, the removal of NH
4
+
and PO
4
3−
in both single and bi-solute system were investigated. Results indicated that NH
3
·H
2
O pretreatment and MgO-coating enhanced biochar pH, CEC, and pHpzc. Additionally, there were generally higher surface area and
V
total
in MgAWS
550
. The maximum adsorption capacities for NH
4
+
and PO
4
3−
, respectively, increased as WS
550
(0.555 and 1.57 mg g
−1
) < MgWS
550
(15.4 and 21.8 mg g
−1
) < MgAWS
550
(17.5 and 31.3 mg g
−1
). Moreover, higher removal efficiencies were achieved in the bi-solute system, and over 25% and 90% of NH
4
+
and PO
4
3−
, respectively, was removed from biogas slurry by MgASW
550
. Mechanically, NH
4
+
removal was mainly attributed to ionic exchange, while PO
4
3−
adsorption on MgO-coated biochars was due to electrostatic attraction and precipitation. Furthermore, the formation of struvite (MgNH
4
PO
4
·6H
2
O) further enhanced N and P in the bi-solute system.
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.
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•Application of Streptomyces pactum promoted plant growth & metals uptake.•Application of Bacillus sp. improved enzymes activity & metals availability.•Co-inoculation improved microbial community, enzymes activity, & plant growth.•Co-inoculation altered Cd, Cu, Pb, &Zn fractions & increased their bioavailability.•Co-application enhanced metals phytoextraction by Brassica juncea.
Bacterial consortium-of Actinobacteria (Streptomyces pactum) and Firmicutes (Bacillus subtilis and Bacillus licheniformis) promoted soil enzymes activities, metals availability, plant growth and thereby enhanced metals phytoextraction efficiency by Brassica juncea.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Soil heavy metal pollution is one of the most serious environmental problems in China, especially cadmium (Cd), which has the most extensive contaminated soil coverage. Therefore, more economical and ...efficient remediation methods and measures are needed to control soil Cd contamination. In this study, different amendments (biochar (B), organic fertilizer (F), lime (L)) and actinomycetes (A) inoculants were applied to Cd contaminated farmland to explore their effects on wheat growth. Compared with Control, all treatments except A treatment were able to significantly increase the underground parts dry mass of wheat, with the highest increase of 57.19 %. The results showed that the B treatment significantly increased the plant height of wheat by 3.45 %. All treatments increased wheat SOD activity and chlorophyll content and reduced the MDA, which contributes to wheat stress resistance under Cd contamination. F, L and AF treatments can significantly reduce the Cd content in wheat above- and underground parts by up to 56.39 %. Soil amendments can modify the physical and chemical properties of the soil, which in turn affects the absorption of Cd by wheat. Moreover, the addition of soil amendments significantly affects the composition and structure of the rhizospheric soil bacterial community at the wheat jointing stage. The application of organic fertilizer increases the richness and diversity of the bacterial community, while lime makes it significantly decreases it. T-test and microbiome co-occurrence networks show that actinomycetes could not only effectively colonize in local soil, but also effectively enhance the complexity and stability of the rhizosphere microbial community. Considering the practical impact of different treatments on wheat, soil microorganisms, economic benefits and restoration of soil Cd contamination, the application of organic fertilizer and actinomycetes in Cd contaminated soil is a more ideal remediation strategy. This conclusion can be further verified by studying larger repair regions and longer consecutive repair cycles to gain insight into the repair mechanism.
•The application of organic fertilizer combined with actinomycetes inoculants performs well in promoting wheat dry mass of underground parts, reducing Cd accumulation in this parts and improving wheat stress resistance.•The addition of actinomycetes can effectively increase the complexity of the microbial network structure and contribute to the stability of the inter-root microecology of the plant.•The combination of actinomycetes and organic fertilizer may be an effective method to control heavy metals in soil.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Purpose
Biochar has been used as an amendment to immobilize toxic metals (TMs) and increase nutrient content in the contaminated soil. In this study, Ca(H
2
PO
4
)
2
-engineered swine manure biochar ...(PSMB) and swine manure biochar (SMB) were prepared and investigated to evaluate their effects on the availability of toxic metals (Cd and Pb) and soil nutrient content in Fengxian (FX)- and Kunming (KM)-contaminated soils through incubation experiment.
Materials and methods
The soil samples were collected at 0–20 cm depth from two contaminated farmlands close to abandoned Pb smelters, which are located in FX and KM. Swine manure was obtained from the rural hog lot in Yangling, China. Each biochar (SMB and PSMB) was mixed with the air-dried soil samples (FX and KM) at a dosage of 1% and 3%
w
/
w
, respectively. Then, a portion of 3 kg of the mixture was placed in plastic pots and incubated for 30 days in a greenhouse. After the soil incubation experiment, pot experiments were performed in a greenhouse of Northwest A&F University, Yangling, China.
Results and discussion
Adding PSMB at a rate of 3% maximally decreased the concentrations of DTPA-extractable Cd (34.02 and 47.73%) and Pb (18.70 and 24.58%) in FX and KM soil. The BCR data revealed that the percentage of acid-soluble Cd and Pb fraction in FX and KM soils remarkably decreased whereas the percentages of residual Cd fraction and reducible Pb fraction in FX and KM soils significantly increased in all the biochar-amended soils compared with control. To confirm these results, a pot experiment was conducted to investigate the effects of amendments on growth and uptake of toxic metals in Chinese cabbage (
Brassica rapa
L. spp.
pekinensis
). The results showed that the addition of PSMB3% significantly (
P < 0.05
) increased the biomass of plants and reduced the absorption of toxic metals in plant.
Conclusions
The results revealed that the dry biomass increased and the absorption of toxic metals decreased in plants. All treatments of biochar were beneficial and application of PSMB 3% was most effective in enhancing plant biomass and reducing the accumulation of toxic metals in the plants.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, metallic copper (Cu) was supported on nanoscale zero-valent iron (nZVI) to form a nanoscale bimetallic composite (nZVI-Cu), which was used to activate persulfate (PS) to simultaneously ...remove the compound contaminants Cr(VI) and tetracycline hydrochloride (TCH) in simulated wastewater. nZVI, nZVI-Cu, and nZVI-Cu-activated PS (nZVI-Cu/PS) were characterized by SEM, TEM, XRD, and XPS. The effects of the bimetallic composite on Cr(VI) and TCH removal were compared in the nZVI, nZVI-activated PS (nZVI/PS), nZVI-Cu, and nZVI-Cu/PS systems. The results showed that nZVI and Cu can form a nanobimetallic system, which can create galvanic cells; thus, the galvanic corrosion of nZVI and the transfer of electrons are accelerated. For a single contaminant, the removal efficiency of Cr(VI) and TCH is the highest when nZVI is loaded with 3 wt% and 1 wt% Cu, respectively. The ratio of nZVI-Cu with 3 wt% Cu to PS is 7:1, and the removal efficiency of Cr(VI) and TCH compound contaminants is ~ 100% after 60 min under acidic conditions, which indicates that the Cr(VI) reduction and TCH oxidation were complete in the nZVI-Cu/PS system. The mechanisms of simultaneous removal of Cr(VI) and TCH in the nZVI-Cu/PS system are proposed. The removal of Cr is because of the adsorption-reduction effects of the nZVI-Cu bimetallic material. The degradation of TCH is mainly due to the action of oxidative free radicals generated by Fe
2+
-activated PS. The free radical capture experiments showed that SO- 4· plays a major role in the process of TCH degradation.
► Both water-soluble Cu and Zn increased at the initial stage of composting. ► HA–Cu and HA–Zn were positively correlated with HA and H/F respectively. ► The distribution coefficients of HA–Cu and ...HA–Zn reached 27.50% and 3.33%. ► The HA–Cu/HA–Zn ratio increased from 1.29 to 2.73 over the composting period.
Influence of humic substances (HS) on bioavailability of Cu and Zn was characterized during 120days co-composting of sewage sludge and maize straw. At the initial stage of composting, Cu and Zn in sewage sludge were released as organic matter was degraded, and water soluble Cu and Zn increased markedly. Water soluble Cu and FA content decreased after 21days whereas water soluble Zn increased during the whole process. Both HA–Cu and HA–Zn were significantly and positively correlated with HA and H/F, respectively. At the end of composting, the distribution coefficients of HA–Cu and HA–Zn reached 27.50% and 3.33% respectively with HA–Cu/HA–Zn ratio increased from 1.29 to 2.73. The results suggest that Cu combined with HA more strongly than Zn, and composting treatment could decrease bioavailability of Cu markedly.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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