Seed nano-priming with multiple nanoparticles enhanced the growth parameters of lettuce and mitigated cadmium (Cd) bio-toxicity: An advanced technique for remediation of Cd contaminated environments.

Seed nano-priming can be used as an advanced technology for enhancing seed germination, plant growth, and crop productivity; however, the potential role of seed nano-priming in ameliorative cadmium (Cd) bio-toxicity under Cd stress has not yet been sufficiently investigated. Therefore, in this study we investigated the beneficial impacts of seed priming with low (L) and high (H) concentrations of nanoparticles including nSiO2 (50/100 mg L-1), nTiO2 (20/60 mg L-1), nZnO (50/100 mg L-1), nFe3O4 (100/200 mg L-1), nCuO (50/100 mg L-1), and nCeO2 (50/100 mg L-1) on lettuce growth and antioxidant enzyme activities aiming to assess their efficacy for enhancing plant growth and reducing Cd phytotoxicity. The results showed a significant increase in plant growth, biomass production, antioxidant enzyme activities, and photosynthetic efficiency in lettuce treated with nano-primed nSiH + Cd (100 mg L-1), nTiH + Cd (60 mg L-1), and nZnL + Cd (50 mg L-1) under Cd stress. Moreover, nano-priming effectively reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) in lettuce shoots. Interestingly, nano-primed nSiH + Cd, nTiH + Cd, and nZnL + Cd demonstrated efficient reduction of Cd uptake, less translocation factor of Cd with high tolerance index, ultimately reducing toxicity by stabilizing the root morphology and superior accumulation of critical nutrients (K, Mg, Ca, Fe, and Zn). Thus, this study provides the first evidence of alleviating Cd toxicity in lettuce by using multiple nanoparticles via priming strategy. The findings highlight the potential of nanoparticles (Si, Zn, and Ti) as stress mitigation agents for improved crop growth and yield in Cd contaminated areas, thereby offering a promising and advanced approach for remediation of Cd contaminated environments.

Effect of particle size of nanoscale zero-valent copper on inorganic phosphorus adsorption-desorption in a volcanic ash soil.

Zero-valent copper engineered nanoparticles (Cu-ENPs) released through unintentional or intentional actions into the agricultural soils can alter the availability of inorganic phosphorus (IP) to plants. In this study, we used adsorption-desorption experiments to evaluate the effect of particle size of 1% Cu-ENPs (25 nm and 40-60 nm) on IP availability in Santa Barbara (SB) volcanic ash soil. X-Ray Diffraction results showed that Cu-ENPs were formed by a mixture of Cu metallic and Cu oxides (Cu2O or/and CuO) species, while specific surface area values showed that Cu-ENPs/25 nm could form larger aggregate particles compared to Cu-ENPs/40-60 nm. The kinetic IP adsorption of SB soil without and with 1% Cu-ENPs (25 nm and 40-60 nm) followed the mechanism described by the pseudo-second-order (k2 = 0.45-1.13 x 10-3 kg mmol-1 min-1; r2 ≥ 0.999, and RSS ≤ 0.091) and Elovich (α = 14621.10-3136.20 mmol kg-1 min-1; r2 ≥ 0.984, and RSS ≤ 69) models. Thus, the rate-limiting step for IP adsorption in the studied systems was chemisorption on a heterogeneous surface. Adsorption equilibrium isotherms without Cu-ENPs were fitted well to the Freundlich model, while with 1% Cu-ENPs (25 nm and 40-60 nm), isotherms were described best by the Freundlich and/or Langmuir model. The IP relative adsorption capacity (KF) was higher with 1% Cu-ENPs/40-60 nm (KF = 110.41) than for 1% Cu-ENPs/25 nm (KF = 74.40) and for SB soil (KF = 48.17). This study showed that plausible IP retention mechanisms in the presence of 1% Cu-ENPs in SB soil were: i) ligand exchange, ii) electrostatic attraction, and iii) co-precipitate formation. The desorption study demonstrated that 1% Cu-ENPs/40-60 nm increased the affinity of IP in SB soil with a greater effect than 1% Cu-ENPs/25 nm. Thus, both the studied size ranges of Cu-ENPs could favor an accumulation of IP in volcanic ash soils.

Organic matter stabilization and phosphorus activation during vegetable waste composting: Multivariate and multiscale investigation.

The conversion of organic matter and P in the waste composting process affects the efficiency of the composted product. However, the addition of microbial inoculants may improve the conversion characteristics of organic matter and P. In this study, straw-decomposing microbial inoculant (SDMI) was added to investigate its effects on the organic matter stabilization and phosphorus activation during the composting of vegetable waste (VWs). Aliphatic carboxyl-containing compounds were degraded during composting, but the stability of the organic matter and P was improved. The addition of SDMI promoted the degradation of dissolved organic carbon by 81.7 % and improved P stability and thermal stability of organic matter. Hedley sequential P fractionation showed a decrease in the H2O-P proportion by >12 % and increased in the HCl-P proportion by >4 % by the end of composting. Stable forms of P, such as AlPO4 and iron-containing phosphate, were the main forms of P in the final compost. The results provide a basis for producing high-quality vegetable compost products and improving the reutilization potential of VWs.

New insight into the mechanisms of preferential encapsulation of metal(loid)s by wheat phytoliths under silicon nanoparticle amendment.

Silicon nanoparticles (SiNPs) have been widely used to immobilize toxic trace metal(loid)s (TTMs) in contaminated croplands. However, the effect and mechanisms of SiNP application on TTM transportation in response to phytolith formation and phytolith-encapsulated-TTM (PhytTTM) production in plants are unclear. This study demonstrates the promotion effect of SiNP amendment on phytolith development and explores the associated mechanisms of TTM encapsulation in wheat phytoliths grown on multi-TTM contaminated soil. The bioconcentration factors between organic tissues and phytoliths of As and Cr (> 1) were significantly higher than those of Cd, Pb, Zn and Cu, and about 10 % and 40 % of the total As and Cr that bioaccumulated in wheat organic tissues were encapsulated into the corresponding phytoliths under high-level SiNP treatment. These observations demonstrate that the potential interaction of plant silica with TTMs is highly variable among elements, with As and Cr being the two most strongly concentrated TTMs in the phytoliths of wheat treated with SiNPs. The qualitative and semi-quantitative analyses of the phytoliths extracted from wheat tissues suggest that the high pore space and surface area (≈ 200 m2 g-1) of phytolith particles could have contributed to the embedding of TTMs during silica gel polymerization and concentration to form PhytTTMs. The abundant SiO functional groups and high silicate-minerals in phytoliths are dominant chemical mechanisms for the preferential encapsulation of TTMs (i.e., As and Cr) by wheat phytoliths. Notably, the organic carbon and bioavailable Si of soils and the translocation of minerals from soil to plant aerial parts can impact TTM sequestration by phytoliths. Thus, this study has implications for the distribution or detoxification of TTMs in plants via preferential PhytTTM production and biogeochemical cycling of PhytTTMs in contaminated cropland following exogenous Si supplementation.

Soil organic carbon stability mediate soil phosphorus in greenhouse vegetable soil by shifting phoD-harboring bacterial communities and keystone taxa.

Addition of organic amendments, such as manure and straw, to arable fields as a partial substitute for mineral phosphorus (P), are a sustainable practice in high-efficiency agricultural production. Different organic inputs may induce varied soil organic carbon (OC) stability and phoD harboring microbes, subsequently regulate P behavior, but the underlying mechanisms are poorly understood. A 11-year field experiment examined P forms by 31P-nuclear magnetic resonance (NMR), OC chemical composition by 13C NMR, and biologically-based P availability methods, phoD bacterial communities, and their co-occurrence in soils amended with chemical P fertilizer (CF), chemical P partly substituted by organic amendments including pig manure (CM), a mixture of pig manure and corn straw (CMS), and corn straw (CS), with equal P input in all treatments. Organic amendments significantly increased soil labile Pi (CaCl2-P, citrate-P, 2.91-3.26 and 1.16-1.32 times higher than CF) and Po (enzyme-P, diesters, 4.08-7.47 and 1.71-2.14 times higher than CF) contents and phosphatase activities, while significantly decreased aromaticity (AI) and recalcitrance indexes (RI) of soil C, compared with CF. The keystone genera in manured soils (Alienimomas and Streptomyces) and straw-applied soils (Janthinobacterium and Caulobacter) were significantly correlated with soil enzyme-P, microbial biomass P (MBP), diesters, and citrate-P. Soil AI and RI were significantly correlated with the phoD keystone and soil P species. It suggested that the keystone was impacted by soil OC stability and play a role in regulating P redistribution in amended soils. This study highlights how manure and straw incorporation altered soil OC stability, shaped the phoD harboring community, and enhanced soil P biological processes promoted by the keystone taxa. The partial substitution of mineral P by mixture of manure and straw is effectively promote soil P availability and beneficial for environmental sustainability.

Impacts of land uses on spatio-temporal variations of seasonal water quality in a regulated river basin, Huai River, China.

Land use impacts from agriculture, industrialization, and human population should be considered in surface water quality management. In this study, we utilized an integrated statistical analysis approach mainly including a seasonal Mann-Kendall test, clustering analysis, self-organizing map, Boruta algorithm, and positive matrix factorization to the assessment of the interactions between land use types and water quality in a typical catchment in the Huai River Basin, China, over seven years (2012-2019). Spatially, water quality was clustered into three groups: upstream, midstream, and downstream/mainstream areas. The water quality of upstream sites was better than of mid-, down-, and mainstream. Temporally, water quality did not change significantly during the study period. However, the temporal variation in water quality of up-, down-, and mainstream areas was more stable than in the midstream. The interactions between land use types and water quality parameters at the sub-basin scale varied with seasons. Increasing forest/grassland areas could substantially improve the water quality during the wet season, while nutrients such as phosphorus from cropland and developed land was a driver for water quality deterioration in the dry season. Water area was not a significant factor influencing the variations of ammonia nitrogen (NH3-N) and total phosphorus (TP) in the wet or dry season, due to the intensive dams and sluices in study area. The parameters TP, and total nitrogen (TN) were principally linked with agricultural sources in the wet and dry seasons. The parameters NH3-N in the dry season, and chemical oxygen demand (CODCr) in the wet season were mainly associated with point source discharges. Agricultural source, and urban point source discharges were the main causes of water quality deterioration in the study area. Collectively, these results highlighted the impacts of land use types on variations of water quality parameters in the regulated basin.

Plant-derived saponin enhances biodegradation of petroleum hydrocarbons in the rhizosphere of native wild plants.

Plant-derived saponins are bioactive surfactant compounds that can solubilize organic pollutants in environmental matrices, thereby facilitating pollutant remediation. Externally applied saponin has potential to enhance total petroleum hydrocarbon (TPH) biodegradation in the root zone (rhizosphere) of wild plants, but the associated mechanisms are not well understood. For the first time, this study evaluated a triterpenoid saponin (from red ash leaves, Alphitonia excelsa) in comparison to a synthetic surfactant (Triton X-100) for their effects on plant growth and biodegradation of TPH in the rhizosphere of two native wild species (a grass, Chloris truncata, and a shrub, Hakea prostrata). The addition of Triton X-100 at the highest level (1000 mg/kg) in the polluted soil significantly hindered the plant growth (reduced plant biomass and photosynthesis) and associated rhizosphere microbial activity in both the studied plants. Therefore, TPH removal in the rhizosphere of both plant species treated with the synthetic surfactant was not enhanced (at the lower level, 500 mg/kg soil) and even slightly decreased (at the highest level) compared to that in the surfactant-free (control) treatment. By contrast, TPH removal was significantly increased with saponin application (up to 60% in C. truncata at 1000 mg/kg due to enhanced plant growth and associated rhizosphere microbial activity). No significant difference was observed between the two saponin application levels. Dehydrogenase activity positively correlated with TPH removal (p < 0.001) and thus this parameter could be used as an indicator to predict the rhizoremediation efficiency. This work indicates that saponin-amended rhizoremediation could be an environmentally friendly and effective biological approach to remediate TPH-polluted soils. It was clear that the enhanced plant growth and rhizosphere microbial activity played a crucial role in TPH rhizoremediation efficiency. The saponin-induced molecular processes that promoted plant growth and soil microbial activity in the rhizosphere warrant further studies.

The effects of light regime on carbon cycling, nutrient removal, biomass yield, and polyhydroxybutyrate (PHB) production by a constructed photosynthetic consortium.

Microalgae can add value to biological wastewater treatment processes by capturing carbon and nutrients and producing valuable biomass. Harvesting small cells from liquid media is a challenge easily addressed with biofilm cultivation. Three experimental photobioreactors were constructed from inexpensive materials (e.g. plexiglass, silicone) for hybrid liquid/biofilm cultivation of a microalgal-bacterial consortia in aquaculture effluent. Three light regimes (full-spectrum, blue-white, and red) were implemented to test light spectra as a process control. High-intensity full-spectrum light caused photoinhibition and low biomass yield, but produced the most polyhydroxybutyrate (PHB) (0.14 mg g-1); a renewable bioplastic polymer. Medium-intensity blue-white light was less effective for carbon capture, but removed up to 82 % of phosphorus. Low-intensity red light was the only net carbon-negative regime, but increased phosphorus (+4.98 mg/L) in the culture medium. Light spectra and intensity have potential as easily-implemented process controls for targeted wastewater treatment, biomass production, and PHB synthesis using photosynthetic consortia.

Microbial inoculants and struvite improved organic matter humification and stabilized phosphorus during swine manure composting: Multivariate and multiscale investigations.

The combined effects of microbial inoculants (MI) and magnesium ammonium phosphate (MAP; struvite) on organic matter (OM) biodegradation and nutrients stabilization during biowaste composting have not yet been investigated. Therefore, the effects of MI and MAP on OM stability and P species during swine manure composting were investigated using geochemical and spectroscopic techniques. MI promoted the degradation of carbohydrates and aliphatic compounds, which improved the degree of OM mineralization and humification. MI and MAP promoted the redistribution of P fractions and species during composting. After composting, the portion of water-soluble P decreased from 50.0% to 23.0%, while the portion of HCl-P increased from 18.5% to 33.5%, which mean that MI and MAP can stabilize P and mitigate its potential loss during composting. These findings indicate that MI can be recommended for enhancing OM biodegradation and stabilization of P during biowastes composting, as a novel trial for the biological waste treatment.

Assessing simultaneous immobilization of lead and improvement of phosphorus availability through application of phosphorus-rich biochar in a contaminated soil: A pot experiment.

Soil lead (Pb) contamination is often caused by anthropogenic activities. In this study, a pot experiment was conducted to assess the effect of biochars derived from pig-carcass (PCBC) and branches of oriental-plane tree (OPBC) on the bioavailability, redistribution, and phytoavailability of Pb and P, as well as the growth of Ipomoea aquatica Forsk in a Pb-contaminated soil. Application of PCBC increased the total and available P concentrations in the soil as compared to the control, and enhanced the concentrations of labile P and sparingly labile P via direct exogenous P input and improvement of soil pH. Both biochars facilitated P accumulation in plant shoots and roots. Sequential extraction of soil Pb confirmed that biochar application facilitated the transformation of mobile Pb into stable fractions, with greater effects from PCBC than OPBC. Hence, biochar application significantly decreased the soil DTPA-extractable Pb by 90.2% (PCBC) and 64.0% (OPBC) compared to the control, consequently reducing Pb uptake by plants. The Pb immobilization by biochar was driven by the biochar-induced increase of soil pH, Pb-phosphate/carbonate precipitation, ion exchange between Pb2+ and biochar-derived cations (e.g., Ca2+ and K+), and surface complexation with functional groups (e.g., carboxyl, hydroxyl, CO). Application of PCBC simultaneously increased the biomass of plant roots and shoots, by 1.8- and 0.6- folds, respectively. Overall, PCBC showed a potential to function as an effective amendment in the immobilization of Pb and alternative P fertilizer to improve degraded soils.

Improving the humification and phosphorus flow during swine manure composting: A trial for enhancing the beneficial applications of hazardous biowastes.

Improving the recovery of organic matter and phosphorus (P) from hazardous biowastes such as swine manure using acidic substrates (ASs) in conjunction with aerobic composting is of great interest. This work aimed to investigate the effects of ASs on the humification and/or P migration as well as on microbial succession during the swine manure composting, employing multivariate and multiscale approaches. Adding ASs, derived from wood vinegar and humic acid, increased the degree of humification and thermal stability of the compost. The 31P nuclear magnetic resonance spectroscopy and X-ray absorption near-edge structure analyses demonstrated compost P was in the form of struvite crystals, Ca/Al-P phases, and Poly-P (all inorganic P species) as well as inositol hexakisphosphate and Mono-P (organophosphorus species). However, the efficiency of P recovery could be improved by generating more struvite by adding the ASs. The flows among nutrient pools resulted from the diversity in the dominant microbial communities in different composting phases after introducing the ASs and appearance of Bacillus spp. in all phases. These results demonstrate the potential value of ASs for regulating and/or improving nutrients flow during the composting of hazardous biowastes for producing higher quality compost, which may maximize their beneficial benefits and applications.

Treatment processes to eliminate potential environmental hazards and restore agronomic value of sewage sludge: A review.

Land application of sewage sludge is increasingly used as an alternative to landfilling and incineration owing to a considerable content of carbon and essential plant nutrients in sewage sludge. However, the presence of chemical and biological contaminants in sewage sludge poses potential dangers; therefore, sewage sludge must be suitably treated before being applied to soils. The most common methods include anaerobic digestion, aerobic composting, lime stabilization, incineration, and pyrolysis. These methods aim at stabilizing sewage sludge, to eliminate its potential environmental pollution and restore its agronomic value. To achieve best results on land, a comprehensive understanding of the transformation of organic matter, nutrients, and contaminants during these sewage-sludge treatments is essential; however, this information is still lacking. This review aims to fill this knowledge gap by presenting various approaches to treat sewage sludge, transformation processes of some major nutrients and pollutants during treatment, and potential impacts on soils. Despite these treatments, overtime there are still some potential risks of land application of treated sewage sludge. Potentially toxic substances remain the main concern regarding the reuse of treated sewage sludge on land. Therefore, further treatment may be applied, and long-term field studies are warranted, to prevent possible adverse effects of treated sewage sludge on the ecosystem and human health and enable its land application.

Rare earth elements (REE) for the removal and recovery of phosphorus: A review.

There is little doubt that 'rock phosphate' reserves are decreasing, with phosphorus (P) peak to be reached in the coming decades. Hence, removal and recovery of phosphorus (P) from alternative nutrient-rich waste streams is critical and of great importance owing to its essential role in agricultural productivity. Adsorption technique is efficient, cost-effective, and sustainable for P recovery from waste streams which otherwise can cause eutrophication in receiving waters. As selective P sorption using rare earth elements (REE) are gaining considerable attention, this review extensively focuses on P recovery by utilising a range of REE-incorporated adsorbents. The review briefly provides existing knowledge of P in various waste streams, and examines the chemistry and behaviour of REE in soil and water in detail. The impact of interfering ions on P removal using REE, adsorbent regeneration for reuse, and life cycle assessment of REE are further explored. While it is clear that REE-sorbents have excellent potential to recover P from wastewaters and to be used as fertilisers, there are gaps to be addressed. Future studies should target recovery and reuse of REE as P fertilisers using real wastewaters. More field trials of synthesized REE-sorbents are highly recommended before practical application.

Phosphorus application enhances alkane hydroxylase gene abundance in the rhizosphere of wild plants grown in petroleum-hydrocarbon-contaminated soil.

This study assessed the ability of phosphorus (P) fertilizer to remediate the rhizosphere of three wild plant species (Banksia seminuda, a tree; Chloris truncata, a grass; and Hakea prostrata, a shrub) growing in a soil contaminated with total (aliphatic) petroleum hydrocarbon (TPH). Plant growth, photosynthesis (via chlorophyll fluorescence), soil microbial activity, alkane hydroxylase AlkB (aliphatic hydrocarbon-degrading) gene abundance, and TPH removal were evaluated 120 days after planting. Overall, although TPH served as an additional carbon source for soil microorganisms, the presence of TPH in soil resulted in decreased plant growth and photosynthesis. However, growth, photosynthesis, microbial activities, and AlkB gene abundance were enhanced by the application of P fertilizer, thereby increasing TPH removal rates, although the extent and optimum P dosage varied among the plant species. The highest TPH removal (64.66%) was observed in soil planted with the Poaceae species, C. truncata, and amended with 100 mg P kg-1 soil, while H. prostrata showed higher TPH removal compared to the plant belonging to the same Proteaceae family, B. seminuda. The presence of plants resulted in higher AlkB gene abundance and TPH removal relative to the unplanted control. The removal of TPH was associated directly with AlkB gene abundance (R2 > 0.9, p < 0.001), which was affected by plant identity and P levels. The results indicated that an integrated approach involving wild plant species and optimum P amendment, which was determined through experimentation using different plant species, was an efficient way to remediate soil contaminated with TPH.

Petroleum hydrocarbon rhizoremediation and soil microbial activity improvement via cluster root formation by wild proteaceae plant species.

Rhizoremediation potential of different wild plant species for total (aliphatic) petroleum hydrocarbon (TPH)-contaminated soils was investigated. Three-week-old seedlings of Acacia inaequilatera, Acacia pyrifolia, Acacia stellaticeps, Banksia seminuda, Chloris truncata, Hakea prostrata, Hardenbergia violacea, and Triodia wiseana were transplanted in a soil contaminated with diesel and engine oil as TPH at pollution levels of 4,370 (TPH1) and 7,500 (TPH2) mg kg-1, and an uncontaminated control (TPH0). After 150 days, the presence of TPH negatively affected the plant growth, but the growth inhibition effect varied between the plant species. Plant growth and associated root biomass influenced the activity of rhizo-microbiome. The presence of B. seminuda, C. truncata, and H. prostrata significantly increased the TPH removal rate (up to 30% compared to the unplanted treatment) due to the stimulation of rhizosphere microorganisms. No significant difference was observed between TPH1 and TPH2 regarding the plant tolerance and rhizoremediation potentials of the three plant species. The presence of TPH stimulated cluster root formation in B. seminuda and H. prostrata which was associated with enhanced TPH remediation of these two members of Proteaceae family. These results indicated that B. seminuda, C. truncata, and H. prostrata wild plant species could be suitable candidates for the rhizoremediation of TPH-contaminated soil.

Mitigation of petroleum-hydrocarbon-contaminated hazardous soils using organic amendments: A review.

The term "Total petroleum hydrocarbons" (TPH) is used to describe a complex mixture of petroleum-based hydrocarbons primarily derived from crude oil. Those compounds are considered as persistent organic pollutants in the terrestrial environment. A wide array of organic amendments is increasingly used for the remediation of TPH-contaminated soils. Organic amendments not only supply a source of carbon and nutrients but also add exogenous beneficial microorganisms to enhance the TPH degradation rate, thereby improving the soil health. Two fundamental approaches can be contemplated within the context of remediation of TPH-contaminated soils using organic amendments: (i) enhanced TPH sorption to the exogenous organic matter (immobilization) as it reduces the bioavailability of the contaminants, and (ii) increasing the solubility of the contaminants by supplying desorbing agents (mobilization) for enhancing the subsequent biodegradation. Net immobilization and mobilization of TPH have both been observed following the application of organic amendments to contaminated soils. This review examines the mechanisms for the enhanced remediation of TPH-contaminated soils by organic amendments and discusses the influencing factors in relation to sequestration, bioavailability, and subsequent biodegradation of TPH in soils. The uncertainty of mechanisms for various organic amendments in TPH remediation processes remains a critical area of future research.

Effects of microorganism-mediated inoculants on humification processes and phosphorus dynamics during the aerobic composting of swine manure.

There is significant interest in the treatment of swine manure, which is a hazardous biowaste and a source of pathogenic contamination. This work investigated the effects of microorganism-mediated inoculants (MMIs) on nutrient flows related to humification or phosphorus (P) dynamics during the aerobic composting of swine manure. The impact of MMIs on microbe succession was also evaluated. The addition of MMIs had positive effects associated with nutrient flows, including thermal activation, decreases in certain fluorescence emissions, lower mass loss and variations in levels of certain elements and functional groups. MMIs altered the maturation behavior and kinetics of organic matter while improving microbial activity. Phosphorus was found in the compost in the forms of MgNH4PO4·6H2O crystals and Poly-P as the IP species, and Mono-P as the OP species in compost generated from the dissolution or inter-transformation among P pools. These nutrient flows are attributed to changes in the structure of microbial communities as a consequence of introducing MMIs. Diverse microbial compositions were identified in different composting phases, although Bacillus appeared in each phase. This work provides support for the aerobic composting of hazardous biowaste as well as an improved understanding of nutrient flows, as a means of producing higher quality compost.

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.

Rhizoremediation as a green technology for the remediation of petroleum hydrocarbon-contaminated soils.

Rhizoremediation is increasingly becoming a green and sustainable alternative to physico-chemical methods for remediation of contaminated environments through the utilization of symbiotic relationship between plants and their associated soil microorganisms in the root zone. The overall efficiency can be enhanced by identifying suitable plant-microbe combinations for specific contaminants and supporting the process with the application of appropriate soil amendments. This approach not only involves promoting the existing activity of plants and soil microbes, but also introduces an adequate number of microorganisms with specific catabolic activity. Here, we reviewed recent literature on the main mechanisms and key factors in the rhizoremediation process with a particular focus on soils contaminated with total petroleum hydrocarbon (TPH). We then discuss the potential of different soil amendments to accelerate the remediation efficiency based on biostimulation and bioaugmentation processes. Notwithstanding some successes in well-controlled environments, rhizoremediation of TPH under field conditions is still not widespread and considered less attractive than physico-chemical methods. We catalogued the major pitfalls of this remediation approach at the field scale in TPH-contaminated sites and, provide some applicable situations for the future successful use of in situ rhizoremediation of TPH-contaminated soils.

Phosphorus-rich biochar produced through bean-worm skin waste pyrolysis enhances the adsorption of aqueous lead.

In China, more than 10,000 tons of bean-worm, which is rich in protein (68.5%) and essential amino acids (52.8%), is consumed annually. Thus, a large amount of bean-worm skin waste is generated, and is often indiscriminately disposed of, potentially causing environment problems. In this study, bean-worm skin (BWS) waste was pyrolyzed at 500 °C to produce biochar (BWS-BC), and the surface properties of BWS and BWS-BC were characterized using various spectroscopic techniques. Pb(II) adsorption properties of BWS and the corresponding biochar as a function of solution pH, contact time, and equilibrium concentration of Pb(II) were examined using adsorption isotherm, kinetics and thermodynamics studies. The maximum Pb(II) adsorption capacities based on the Langmuir isotherm model were calculated as 45 and 62 mg g-1 for BWS and BWS-BC, respectively, which were comparable to the values obtained for biochars derived from other agro-wastes. The adsorption feasibility, favorability and spontaneity of Pb(II), as derived from the thermodynamic parameters, indicated that chemisorption and precipitation (e.g., hydroxypyromorphite) were the main adsorption mechanism in case of BWS and BWS-BC, respectively. Thus, conversion of BWS to biochar for Pb(II) adsorption can be considered as a feasible, promising and high value-added approach for BWS recycling.