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Background: Biochar can enhance phytoremediation in petroleum hydrocarbon polluted soils, making it an intriguing soil amendment option for remediating polluted soil. Biochar can improve the fertility of depleted soils through a range of mechanisms. This study can contribute valuable insights into the origin of biochar and enhance our understanding of the efficacy of different biochar types in remediating petroleum hydrocarbon polluted soils. Aims: To assess the efficacy of different biochar types and plant growth in remediating petroleum hydrocarbon polluted soils. Methods: A field experiment was conducted at the automobile workshop (commonly called mechanic village) from July to October 2021, using a randomized complete block design. The land was sectioned into designated plots with three replicates. Maize stalk biochar (MSB) and nipa palm biochar (NPB) were treated differently in each plot at a rate of 20 t ha−1. Plots containing no biochar were used as controls. Initial and final soil analyses were conducted. Results: Preliminary soil assessments revealed higher values of soil bulk density (1.51 g cm−3), moisture content (35.02%), organic carbon (41.01 g kg−1), cation exchange capacity (13.27 cmol kg−1), total petroleum hydrocarbon content (PHCt) (775.83 mg kg−1), cadmium (Cd) (5.41 mg kg−1), chromium (Cr) (25 mg kg−1), lead (Pb) (33.51 mg kg−1), and zinc (Zn) (0.91 mg kg−1) in the polluted soil than in the unpolluted counterpart. The polluted soil displayed lower hydraulic conductivity (Ks) (1.17 cm h−1), available phosphorus (69.46 mg kg−1), manganese (Mn) (6.38 mg kg−1) and iron (Fe) (4.18 mg kg−1) contents than the unpolluted soil. The PHCt, Cd, and Cr were significantly decreased following the application of biochar. NPB recorded the lowest petroleum hydrocarbon (19%), lead (37%), manganese (57%), and zinc (69%) contents, whereas MSB had the lowest cadmium (50%) and chromium (27%) contents when compared with the control. Between heavy metal accumulations in the leaves and fruits, a greater accumulation of Cd, Cr, and Pb was found in the leaves, whereas Ni accumulation was found in the fruits. The highest Cd (47.0 mg kg−1) and Ni (8.3 mg kg−1) accumulations in the leaves were recorded in NPB treated plots. Similarly, Cd (5.3 mg kg−1), Cr (3.7 mg kg−1), Pb (21.6 mg kg−1), and Ni (23.4 mg kg−1) accumulation in the fruits recorded the highest values in the NPB treated plots. The NPB plants were the tallest compared with the other treatments. In addition, NPB plants had the widest leaf area compared with other treatments. Conclusion: The results indicated that the amendment of NPB may be suitable for the phytoremediation of soils polluted with petroleum hydrocarbons. [ABSTRACT FROM AUTHOR]

The agri-food industry, produces organic residues that could be reused as fertilizer, thereby allowing the recycling of nutrients for crops and the replacement of mineral fertilizers. In this context, here we examined the capacity of anaerobic digestates and mixed residues (digestates plus spent mushroom substrates) to supply nutrients to lettuce (Lactuca sativa L.) grown in a greenhouse experiment. Moreover, the potential leaching of nutrients into the soil was evaluated in a column assay. The results obtained from organic residues treatments were then compared to those achieved in soil treated with mineral fertilizer and in untreated soil. Digestates treatments minimized the potential risk of nitrate (NO3−) leaching by allowing the slow release of NO3− maintaining crop yield. Given our observations, this type of organic residues emerges as an alternative to mineral fertilizer. The loss of NO3−-N from the total amount of N applied reached ∼3% in the mixed residues treatments, 36–46% in the digestate treatments, and 68% in the mineral fertilizer treatment. The mixed treatments showed low available N content as a result of immobilization in the soil, which is a limiting factor for crop production. Moreover, the organic residues treatments had no negative effect on lettuce seed germination or plant growth with respect to parameters such as chlorophyll, total polyphenols, and heavy metals in aerial biomass. The findings reported herein contribute to a better understanding of nutrient availability provided by organic residues materials and the capacity of these amendments to replace mineral fertilizers and avoid nutrient loss by leaching. Digestate treatments showed a similar capacity to maintain lettuce production as mineral fertilizer. Mixed treatments did not provide mineral N for the crop by N immobilization in soil. Nitrate loss when organic residues were applied was lower than for the mineral fertilizer treatment. Soil amendment with organic residues has no negative effects on lettuce yield. Digestates emerge as an alternative to mineral fertilizers for lettuce production, reducing soil nutrient loss. [ABSTRACT FROM AUTHOR]

The land application of sewage sludge can cause different environmental problems due to the high content of potentially toxic elements (PTEs). The objective of this study was to compare the effect of urban biological sewage sludge (i.e. the waste of activated sludge process) and its derived biochar as the soil amendments on the bioavailability of PTEs and their bioaccumulation by corn (Zea mays L.) under two months of greenhouse conditions. The soil was treated by adding biochar samples at 0 (control), 1, 3, 5% w/w. The diethylenetriamine pentaacetic acid (DTPA)-extractable concentrations of PTEs including Zn, Pb, Cd, Cr, Ni, Fe, and Cu in soil and their accumulation by plant shoot and root were measured. Conversion of the biological sewage sludge into the biochar led to decrease the PTEs bioavailability and consequently decreased their contents in plant tissues. The DTPA extractable metal concentrations of produced biochar in comparison to the biological sewage sludge reduced 75% (Cd), 65% (Cr), 79% (Ni and Pb), 76% (Zn), 91% (Cu) and 88% (Fe). Therefore, the content of Ni, Fe, Zn and Cd in corn shoot was decreased 61, 32, 18 and 17% respectively in application of 5% biochar than of raw sewage sludge. Furthermore, the application of 5% biochar enhanced the physiological parameters of the plants including shoot dry weight (twice) and wet weight (2.25 times), stem diameter (1.70 times), chlorophyll content (1.03 times) in comparison to using 5% raw sewage sludge. The results of the study highlight that application of the biochar derived from urban biological sewage sludge in soil could decrease the risk of PTEs to the plant. [ABSTRACT FROM AUTHOR]

Agricultural soils contaminated with heavy metals (HMs) impose a threat to the environmental and to human health. Amendment with biochar could be an eco-friendly and cost-effective option to decrease HMs in contaminated soil. This paper reviews the application of biochar as a soil amendment to immobilise HMs in contaminated soil. We discuss the technologies of its preparation, their specific properties, and effect on the bioavailability of HMs. Biochar stabilises HMs in contaminated soil, enhance the overall quality of the contaminated soil, and significantly reduce HM uptake by plants, making it an option in soil remediation for HM contamination. Biochar enhances the physical (e.g. bulk density, soil structure, water holding capacity), chemical (e.g. cation exchange capacity, pH, nutrient availability, ion exchange, complexes), and biological properties (e.g. microbial abundance, enzymatic activities) of contaminated soil. Biochar also enhances soil fertility, improves plant growth, and reduces the plant availability of HMs. Various field studies have shown that biochar application reduces the bioavailability of HMs from contaminated soil while increasing crop yield. The review highlights the positive effects of biochar by reducing HM bioavailability in contaminated soils. Future work is recommended to ensure that biochars offer a safe and sustainable solution to remediate soils contaminated with HMs. [ABSTRACT FROM AUTHOR]

The pollution of soils and groundwater by heavy metal pollutants is a widespread environmental problem, particularly in Iran. One cost-effective method to remediate the polluted soils is phytoremediation, in which different plants are used to extract the heavy metals from soil and accumulate them in their organs. In this study, the phytoremediation potential of native plants of Southwestern Iran in removing nickel and lead from polluted soil was assessed separately and in combination with organic amendments of compost and biochar.Hence, the pot experiments were conducted in the greenhouse using soil gathered from the Pazanan oil refineryin Gachsaran, located at Kohgiluyeh and Boyer-Ahmad Province. Then, the hierarchical cluster analysis was applied to classify the different treatments of amendments.The results indicated that the phytoremediation strength of three native species for Ni uptake was C. procera> St. Plumosa > M. sativa; and for Pb uptake was St. Plumosa > C. procera> M. sativa. Also, the utilisation of organic materials originated from urban waste caused to increase in the Ni and Pb accumulation in root and shoot of these species as well as the residual concentration of the metals in soil. Based on the cluster analysis, the treatment of biochar 2% showed the most effect on the residual concentration of heavy metals in soil (1128.00 mgkg−1);the treatment of biochar 1% represented the highest accumulation of metals at the root (158.82 mgkg−1), while all treatments of different amounts of amendments have the same effect on the accumulation of heavy metals in the shoot (151.38 mgkg−1). In general, cluster analysis showed that the organic amendments, especially biochar even at low amounts can improve the phytoremediation capability of the studied native species in removing Ni and Pb from polluted soil. [ABSTRACT FROM AUTHOR]

Remediation of brown fields is a challenge and this paper aimed at quantifying the extent of heavy metal pollution in contaminated soils and used a Nano based amendment to encapsulate it by means of aggregation and agglomeration in the interstices of soil particles making them inert and sorbing them permanently. Cation heavy metals predominantly priority heavy metals in any brown field viz. Cadmium, Nickel and Lead have been studied on three soils representing a steel mill waste site, battery works unit site and an unscientific solid waste dumpsite. The order of sorption of metal ions was Pb>Cd>Ni. The efficiency of material for desorption under-harsh conditions were evaluated using a strong acid, weak acid and chelating agents such as EDTA. It was found that Nano based amended soils retained more than 55% heavy metals even under harsh conditions proving the potential of Nano technology as a superior material. [ABSTRACT FROM AUTHOR]

This work investigated the effect of soil amendments on the mobility of heavy metals and P in acidic and calcareous heavy metal polluted soils after incubated for one year. Compared to phosphate alone, the phosphate+bentonite amendment had lower available P concentrations (13.1 and 16.3% in the acidic and calcareous soils, respectively) and similar heavy metal immobilization capacity. The lime amendment increased soil P availability possibly by increasing the negative charges of soil particles in both soils. Lime amendment greatly reduced the DTPA-extractable concentrations of Cd, Cu, Mn, Ni, Pb and Zn in both soils; greater reductions were observed with higher rate compared to the lower rate and in the acidic soil compared to the calcareous soil, especially for Cd, Mn, Ni and Zn (23.9–95.3% lower than the control). The bentonite in the phosphate+bentonite treatment may have reduced soil P availability by adsorption of soluble P. Based on the results, phosphate+bentonite instead of phosphate alone may be used to reduce heavy metal and P availability in heavy metal contaminated soil. When only lime is used, caution should be taken with respect to potential soil P losses and subsequent off-site degradation in water and environmental quality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wheat straw, rice husk, pig manure, and oyster shell were used for co-pyrolysis. • Co-pyrolysis promoted syngas heat value and biochar characteristics. • Co-pyrolysis biochar was superior to limestone for soil remediation. • Application of COPB could be financially viable due to yield increase of cabbage. Co-pyrolysis is a potentially effective method for both biomass waste management and multi-functional biochar-based product design. It involves the thermochemical decomposition of biomass waste under anoxic conditions, which can reduce the cost of disposal and produce biochar with beneficial properties. Herein, this study aimed to investigate the properties and environmental applications of biochar from single- and mixed- feedstocks of wheat straw, rice husk, pig manure, and oyster shell at 450 ℃, respectively. A pot experiment with Chinese cabbage was carried out to compare the effects of biochars with limestone on soil Cd and Pb immobilization at two harvest periods. The results indicated that co-pyrolysis of various biomasses exhibited synthetic effects on promoting the calorific value of syngas and enhancing the quality of produced biochar. The pot experiment revealed a significant promotion on soil pH, soil organic matter, cation exchange capacity, and soluble Ca, which consequently reduced Cd and Pb availability. In contrast with limestone treatment, soil amendment with single biomass-derived and co-pyrolysis-derived (COPB) biochars had a significant positive impact on soil fertility and microbial biomass. Application of COPB at a 0.5% dosage consistently and most effectively enhanced the shoot biomass, increased leaf Vitamin C content but reduced leaf content of nitrate and heavy metals in both harvests. Using COPB for soil remediation would be financially visible due to the enhancement of crop yield. Therefore, this study proposes a strategy for targeted enhancement of the functions of biochar derived from co-pyrolysis of selected biomass waste for soil remediation and agricultural production. [ABSTRACT FROM AUTHOR]

Various phosphate compounds have been known as highly beneficial amendments for soils contaminated by heavy metals (Pb, Zn, Cu, Cd). Considering their application in agriculture as nutrient source (fertilizer) and potential for soil remediation, they have been a focus of several studies. In this work, we have attempted to evaluate the efficiency of three phosphates (a commercial product TCP, and pure phosphates MPP and DAP) to reduce the bioavailability of Pb and Cd pollutants in contaminated soil. Evaluation was made on the basis of two most common tests for leachability and extractability of heavy metals: TCLP and sequential extraction analysis. Data indicates that all three amendments can reduce concentration of extractable Pb and Cd, and MPP and DAP can be somewhat more efficient. [ABSTRACT FROM AUTHOR]

To ascertain the effect of biochar on remediation of paddy soil contaminated by heavy metals under different irrigation regimes (flooding irrigation (FI), intermittent irrigation (II) and wet irrigation (WI)), rice straw biochar (RSB) and rice husk biochar (RHB) were applied into soil contaminated by Cd and Cu. The concentrations of available Cd and Cu were significantly reduced by RSB, and decreased by 6.8–15.9%, 11.1–20.0% and 6.8–18.2%, and 6.2–12.9%, 7.0–14.8% and 5.6–17.7% under FI, II and WI regimes, respectively. The application of RHB generally reduced the content of acid extractable and reducible Cd under FI and II regimes, and promoted its transformation to oxidizable and residual form. Similarly, both biochars reduced the acid extractable Cu in paddy soil and promoted its transformation to reducible and oxidizable form under three irrigation regimes (especially in II). This is significantly related to the increase of soil pH, organic matter content and cation exchange capacity by biochar. The preliminary results of this study indicate that biochar application combined with intermittent irrigation could be an effective measure to enhance the paddy soil quality. However, future studies are still needed to evaluate the long-term impact of biochar on heavy metal bioavailability under different water conditions. [ABSTRACT FROM AUTHOR]

The spent biomass of water hyacinth (Eichhornia crassipes) after oyster mushroom cultivation is not much suitable for application as soil amendment. As a means to avoid environmental pollution and to decrease waste to landfill, the spent biomass was primarily composted with cow dung and then feed to red wiggler earthworm (Eisenia fetida) to transform it into vermicompost. The produced vermicompost showed significant reduction in salt concentration, electrical conductivity, available K concentration, C/N ratio and increase in pH, available N and P. The representative heavy metals (Fe, Cu, Zn, Pb and Cd) detected in the spent biomass of water hyacinth were derived from the initial plant biomass. Among these metals, concentration of Fe increased and that of Zn decreased significantly in the vermicompost, while the other metals did not show significant change. When applied as amendment to control soil for growth of radish plants, the vermicompost treatment resulted in significantly higher shoot and root biomass. Also, the amendment decreased the bioavailability of metals (especially Cd) and their accumulation in radish plants. The metal concentrations in the vermicompost and in the radish plants were found to fall within the permissible limits for compost and the normal range present in plants, respectively, indicating the suitability of the vermicompost for use as organic fertilizer. Utilization of the water hyacinth as substrate for oyster mushroom cultivation and recycling the spent mushroom substrate through vermicomposting could therefore provide food and fertilizer with no waste to landfill, changing the status of the invasive aquatic weed from a prolific pest to a potentially usable product. [ABSTRACT FROM AUTHOR]

Contamination of agricultural soil with chromium (Cr) ions has threatened global crop, human and ecosystem health. Its two oxidation states viz. Cr(III) and Cr(VI) are most stable and readily available to the plants. The study explored the impact of increasing exposure (up to 500 ppm) of Cr(III) and Cr(VI) on bio-physical traits of 15-day-old seedlings (in vitro) as well as 60-day-old tomato plant (in vivo), and highlighted the importance of buffel grass (Cenchrus pennisetiformis) in mitigating Cr levels in the tomato plants. In vitro, Petri plate bioassays with 13 different concentrations (20–500 ppm) of Cr(III) and Cr(VI) depicted the highly toxic effect of metal ions ≥ 200 ppm on all bio-physical traits of tomato seedlings. In vivo, soil spiked with Cr(III) and Cr(VI) (200, 300, and 400 mg/kg) was amended with 1% and 2% dry biomass of buffel grass. Phytotoxicity was higher in Cr(VI)-spiked soil compared with Cr(III)-spiked soil. Cr was mainly accumulated in tomato roots, and more Cr was translocated from roots to shoots from Cr(VI)-spiked soil than Cr(III)-spiked soil. Soil amendments with 2% weed biomass reduced metal toxicity in plants, particularly at 200 and 300 mg/kg of Cr. Protein profiles through SDS-PAGE revealed 12–50 kDa (mainly PR proteins) as an important region in tomato leaf, where many new bands were expressed under different treatments, particularly in the treatments provided with buffel grass. PCA-based biplot clearly separated Cr tolerance treatments from highly sensitive treatments. For the cultivation of tomato plants in Cr(III) and Cr(VI) contaminated soil (200 and 300 mg/kg), the biomass of Cloncurry buffel grass should be considered an effective and easily available phyto-management option. [ABSTRACT FROM AUTHOR]

Amendment tailing heaps with compost may deplete metal(loid)s concentration and improve the conditions for plant development. This research aimed to compare the Tecoma stans ability to grow on soil from the Sonora desert and mining waste (MW) after amendment with compost. Amendment the MW, with compost, decreased soluble As, Cd, Cu, Mn, Pb, and Zn up to 47, 33, 11, 34, 69, and 34%, respectively; increased ten times the leaves weight, and thirteen times the leaf area of the plants. Arsenic, Cd, Pb, Cu, and Zn in plants tissues decreased 27, 28, 27, 12, and 11%, respectively. The bioaccumulation and translocation factors were lower than one, so T. stans do not accumulate these elements. Polyunsaturated fatty acids 18:2ω6 and 18:3ω3 were increased, suggesting lower alteration of thylakoidal membrane integrity due to compost treatment. But, the amendment to the tailing was not enough to deplete the abiotic stress. Amendment mine tailing with vermicompost depletes changes in polyunsaturated fatty acid of Tecoma stans [ABSTRACT FROM AUTHOR]

Heavy metal contamination in agricultural land is an alarming issue in Vietnam. It is necessary to develop suitable remediation methods for environmental and farming purposes. The present study investigated the effectiveness of using peanut shell-derived biochar to remediate the two heavy metals Zn and Pb in laboratory soil assays following Tessier's sequential extraction procedure. The concentration of heavy metals was analyzed using Inductively coupled plasma mass spectrometry (ICP-MS). This study also compared the effectiveness of the blend of biochar and apatite applied and the mere biochar amendment on the chemical fractions of Pb and Zn in the contaminated agricultural soil. Results have shown that the investigated soil was extremely polluted by Pb (3047.8 mg kg−1) and Zn (2034.3 mg kg−1). In addition, the pH, organic carbon, and electrical conductivity values of amended soil samples increased with the increase in the amendment's ratios. The distribution of heavy metals in soil samples was in the descending order of carbonate fraction (F2) > residue fraction (F5) > exchangeable fraction (F1) > Fe/Mn oxide fraction (F3) > organic fraction (F4) for Pb and F5   ≈   F2 > F1 > F3 > F4 for Zn. The peanut shell-derived biochar produced at 400 °C and 600 °C amended at a 10% ratio (PB4:10 and PB6:10) could significantly reduce the exchangeable fraction Zn from 424.82 mg kg−1 to 277.69 mg kg−1 and 302.89 mg kg−1, respectively, and Pb from 495.77 mg kg−1 to 234.55 mg kg−1 and 275.15 mg kg−1, respectively, and immobilize them in soil. Amending the biochar and apatite combination increased the soil pH, then produced a highly negative charge on the soil surface and facilitated Pb and Zn adsorption. This study shows that the amendment of biochar and biochar blended with apatite could stabilize Pb and Zn fractions, indicating the potential of these amendments to remediate Pb and Zn in contaminated soil. [ABSTRACT FROM AUTHOR]

The impact of pig slurry (PS) application on the structural dynamics of humic substances (HS) and on the mobility of Cu, Zn, Ni, and Pb in a dystrophic Red Nitosol planted with winter forage grasses was evaluated. After four PS applications, the humic acids (HA) and fulvic acids (FA) were characterized by spectroscopy techniques allied to chemometrics methods. The metals contents in soil, in HS and in the tissues of plant were quantified. PS application increases the total organic carbon, especially the nonhumic carbon, which contribute to increase FA content. The carbon in FA and HA increases with the highest PS dose applied, especially aliphatic structures in FA and aromatic structures in HA. The amount of Pb and Cu in FA and HA increases respectively, as well as Cu, Zn, Ni, and Pb bioavailable. PS applications increase the biomass production in grasses and the metals content accumulated in the tissues. Our study shows that the PS application modifies the structure of SOM, incorporating fragments, and modifying its dynamics, which regulates the dynamics and the accumulation of metals in soils and plants. The association of metals with soluble structures seems to inactivate their toxicity and does not affect plant growth. [ABSTRACT FROM AUTHOR]

The assessment of remediation on metal-polluted soils is usually focused on total and/or bioavailable metal content. However, these chemical variables do not provide direct information about reductions in heavy metals pressure on soil microorganisms. We propose the use of bacterial communities to evaluate the efficiency of three remediation techniques: crushed mussel shell (CMS) and pine bark (PB) as soil amendments and EDTA-washing. A soil sample was polluted with different doses of Cu, Ni, and Zn (separately). After 30 days of incubation, the remediation techniques were applied, and bacterial community tolerance to heavy metals determined. If bacterial communities develop tolerance, it is an indicator that the metal is exerting toxicity on them. Soil bacterial communities developed tolerance to Cu, Ni, and Zn in response to metal additions. After remediation, bacterial communities showed decreases in bacterial community tolerance to Cu, Ni, and Zn for all remediation techniques. For Cu and Ni, soil EDTA-washing showed the greatest reduction of bacterial community tolerance to Cu and Ni, respectively, while for Zn the soil amendment with PB was the most effective remediation technique. Thus, bacterial community tolerance to heavy metals successfully detect differences in the effectiveness of the three remediation techniques. [ABSTRACT FROM AUTHOR]

Many countries around the world are suffering from serious problems associated with soil heavy metal pollution, especially developing countries. Heavy metal contaminants in soils mainly result from soil natural weathering and anthropogenic activities such as industrial and agricultural activities, coal-burning as well as transportation. It is widely acknowledged that heavy metal pollution may lead to the deterioration of soil environmental quality and the loss of soil ecological functions. Therefore, the control and remediation for soil heavy metal pollution need to be urgently carried out to guarantee human health and food security. To date, soil amendments are increasingly employed to remediate heavy metal contaminated soils. In recent years, the research progress at an international scale is reviewed with regard to soil amendments used for the remediation of heavy metal polluted soils by laboratory and field-scale studies. A summary is provided with soil amendment types, metal stabilization mechanisms, as well as the influences of soil amendment application on soil properties. At last, future research prospects are put forward to broaden the development of this field. It is expected to provide valuable references for the research and practice of heavy metal stabilization in polluted soils. [ABSTRACT FROM AUTHOR]

Repeated and excessive use of inorganic phosphorus fertilisers adversely affects soil fertility, reduces plant phosphorus (P)-use efficiency, increases soil heavy metal concentrations and poses human health risks via food chain interaction. Organic amendments (OAs) are considered as cost-effective and environment-friendly supplement to inorganic P fertilisers that are produced from scarce phosphate rocks. Numerous studies have reported the synergistic and antagonistic effects of OAs on crop production, P solubility and availability, and immobilisation of heavy metals. However, the results of these studies are found to be variable and demand a critical review. This article summarises the environmental and health implications of continuous inorganic P fertilisers application along with a detailed overview of commonly available OAs and their efficacy to stimulate plant growth and yield. Moreover, this review describes the potentiality of OAs to increase the bioavailability of P in soil, discusses how and to what extent these soil amendments can immobilise heavy metals and reduce plant uptake, and finally provides future research directions for organic farming and sustainable agricultural practices. Continuous use of inorganic phosphate fertilisers (iPFs) adversely affects soil fertility, reduces plant phosphorus-use efficiency, increases soil heavy metal concentrations, and poses severe human health risks. This article summarises the potential of organic amendments (OAs) over iPFs to stimulate plant growth and yield, increase phosphorus availability in soil, and reduce plant heavy metal uptake by immobilising them in soil. This summary will contribute towards organic farming and sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Repeated and excessive use of inorganic phosphorus fertilisers adversely affects soil fertility, reduces plant phosphorus (P)-use efficiency, increases soil heavy metal concentrations and poses human health risks via food chain interaction. Organic amendments (OAs) are considered as cost-effective and environment-friendly supplement to inorganic P fertilisers that are produced from scarce phosphate rocks. Numerous studies have reported the synergistic and antagonistic effects of OAs on crop production, P solubility and availability, and immobilisation of heavy metals. However, the results of these studies are found to be variable and demand a critical review. This article summarises the environmental and health implications of continuous inorganic P fertilisers application along with a detailed overview of commonly available OAs and their efficacy to stimulate plant growth and yield. Moreover, this review describes the potentiality of OAs to increase the bioavailability of P in soil, discusses how and to what extent these soil amendments can immobilise heavy metals and reduce plant uptake, and finally provides future research directions for organic farming and sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) toxicity is serious abiotic stress that is significantly reducing crop productivity and posing a serious threat to human health, soil and environmental quality. Therefore, it is urgently needed to find appropriate measures to mitigate the adverse impacts of HMs on soil, plants, humans and the environment. Biochar (BC) has emerged as an excellent soil amendment to minimize the adverse impacts of HMs and to improve soil fertility and environmental quality. Biochar application decreases HMs uptake and their translocation to plant parts by forming complexes and precipitation. Biochar also has improved soil pH, soil fertility and soil cation exchange capacity (CEC) and it also increases adsorption of HMs thus reduces their mobility and subsequent availability to plants. BC application also maintains membrane stability and improves uptake of nutrients, osmolytes accumulation, antioxidant activities, and gene expression, therefore, improves the plant performance under HMs stress. Biochar application also improves the photosynthetic performance by increasing the synthesis of photosynthetic pigments, stomata conductance and increasing the water uptake by plants. Besides this, BC also scavenges ROS by increasing the antioxidant activities, gene expression, and accumulation of proline in HMs contaminated soils. This review highlights the role of BC to mitigate the HMs toxicity in plants. We have discussed the role of BC in the modification of soil properties to induce tolerance against HMs toxicity. Moreover, we have discussed various mechanisms mediated by BC at the plant level to induce tolerance against HMs. Additionally, we also identified research gaps that must be fulfilled in future research studies. [ABSTRACT FROM AUTHOR]

Biodiversity can enhance soil multifunctionality through strengthening biotic interactions in soil food webs, but largely unknown in agroecosystems. We therefore predicted that vermicompost, serving as an organic amendment and soil health conditioner, could enhance trophic interactions among bacteria, fungi and nematodes and mediate synergies and trade-offs among soil functions, especially when substituting synthetic fertilizer was applied to soils. Soil multifunctionality was assessed from plant growth and product quality, carbon and nutrient cycling, water and climate regulation in an intensive cropping system. Pepper, tomato and spinach were cultivated in rotation annually, with substituting vermicompost as a nutrient replacement for synthetic fertilizer for 5 years. Results showed that substituting a moderate dose of vermicompost for synthetic fertilizer offered the highest soil multifunctionality by enhancing synergies among multiple functions. The vermicompost-stimulated multifunctionality was primarily attributed to the cascading effects of the complex food web structure induced by omnivorous nematode. These effects were regulated by the physicochemical environment of the vermicompost-amended soil. Notably, the multifunctional benefits degraded when higher rates of vermicompost were applied, suggesting that over-use of vermicompost combined with an inadequate amount of synthetic fertilizer could simplify soil food web structure and decrease soil functions, mainly due to the nutrient limitation and increasing harmful substances as indicated by C:N stoichiometry, heavy metals and antibiotic resistance genes. In intensive agricultural systems, finding an optimal balance of organic amendments and synthetic fertilizer that supports complex soil food web interactions is therefore crucial for promoting multiple soil functions and particularly sustaining the production of high-quality food crops. • The highest soil multifunctionality was observed in moderate vermicompost substitution. • Moderate vermicompost addition enhanced synergies among multiple functions. • Soil food web structure coordinated by omnivores was associated with multifunctionality. • Vermicompost supported multifunctionality of ecologically intensive agriculture. [ABSTRACT FROM AUTHOR]

This study evaluates pyrolysis products obtained from biomasses (silver grass, pine, and acacia) harvested from heavy-metal-contaminated soil. To do so, we utilized two methods: a batch one-stage pyrolysis, and a continuous two-stage pyrolysis. The study results show that the yields and characteristics of bio-oils and biochars varied depending on the pyrolysis process and the type of biomass. The two-stage pyrolysis having two reactors (auger and fluidized bed reactors) appeared to be very suitable for specific chemicals production such as acetic acid, acetol, catechol, and levoglucosan. The biochar obtained from the fluidized-bed reactor of two-stage pyrolysis had high thermal stability, high crystallinity, high inorganic content, and a small number of functional groups. In contrast, the biochar obtained from the one-stage pyrolysis had low thermal stability, low crystallinity, a high carbon content, and a large number of functional groups. The biochar obtained from the two-stage pyrolysis appeared to be suitable as a material for catalyst support and as an adsorbent. The biochar obtained from one-stage pyrolysis appeared to be a suitable as a soil amendment, as an adsorbent, and as a precursor of activated carbon. All biochars showed a negative carbon footprint. In the end, this study, which was conducted using two different processes, was able to obtain the fact that products of pyrolysis biomass contaminated with heavy metals have different characteristics depending on the process characteristics and that their utilization plans are different accordingly. If the optimal utilization method proposed through this study is found, pyrolysis will be able to gain importance as an effective treatment method for biomass contaminated with heavy metals. [Display omitted] • Results of one-stage and two-stage pyrolysis of contaminated biomass were compared. • Two-stage pyrolysis turned out to be suitable for specific chemicals production. • Biochar from fluidized-bed reactor has potential as catalyst support and absorbent. • Biochar from fixed-bed reactor has potential as soil amendment and absorbent. • All biochars seemed to be applicable in construction field as sustainable materials. [ABSTRACT FROM AUTHOR]

Rapid industrialization and urbanization have resulted in the widespread contamination of soil by potentially toxic metal(loid)s (PTMs). Among these, arsenic (As), cadmium (Cd), chromium (Cr) lead (Pb) and nickel (Ni) are particularly concerning, affecting millions of hectares of arable land globally and posing significant threats to food security and human health. Biochar (BC) has emerged as a promising soil amendment due to its ability to mitigate soil pollution by immobilizing contaminants. But how biochar-linked free radicals affect this process in plants and soil remains murky. Additionally, the mechanism of the geochemical transformation of PTMs in soil-plant systems influenced by biochar-based free radicals is unclear. Here, the influence of free radicals on immobilization, and transformation of PTMs in the soil-plant system under various BC and Comp treatment was investigated. Six treatment groups (1% and 2% biochar, compost, combined application, and control) were randomly assigned to pots in a randomized complete block design (RCBD) to test their effects on maize growth. Results revealed that there was a noticeable rise in the concentration of free radicals in both the BC and Comp treatments compared to the control and the combined application of BC and Comp treatments. The biochar treatment showed a slight reduction in these functional groups, suggesting possible adsorption or sequestration onto the BC surface while the Comp treatment led to an increase in functional groups associated with carbohydrates, proteins, and lipids, indicating enhanced organic matter content. The combined treatment exhibited intermediate effects, suggesting a synergistic interaction between Comp and biochar. X-ray diffraction analysis indicated that the BC did not demonstrate significant alterations in soil mineralogy, suggesting minimal direct effects on mineral dissolution or transformation. Conclusively, biochar-generated free radicals, especially hydroxyl radicals (•OH), play a crucial role in PTMs (i.e., Cd, Cr, Ni, As and Pb) immobilization in soil-plant systems. This study provides novel insights into biochar's mechanisms for mitigating PTMs pollution, paving the way for optimized soil amendment strategies. • BC and Comp influence free radicals generation in the soil-plant system. • BC & Comp treatments affect maize growth influence PTMs availability. • BC-based free radicals play a pivotal role in the geochemical transformation of PTMs. • Reveals distinct effects of BC and Comp amendments on soil functional groups. • BC and Comp demonstrate synergistic effects on FR generation and PTM transformation. [ABSTRACT FROM AUTHOR]

This study aimed to contribute to the rehabilitation and remediation of mine tailings and heavy metal (HM) contaminated environments through phytostabilization using plants with added economic benefits such as citronella (Cymbopogon nardus Rendle.). A greenhouse pot experiment of citronella was evaluated in Cu-Ni mine tailings by monitoring its growth rate, physiological responses, and HM accumulation as affected by the application of four different soil amendments under greenhouse conditions. The treatments include T1 (control) as tailings without amendments, T2 as tailings + 10% cow manure (v/v), T3 as tailings + 10% compost (mixture of organic farm waste and manure, v/v), T4 as tailings + lime at 5 tons ha–1, T5 as tailings + lime (2x) at 10 tons ha–1, and T6 as tailings + 10% fly ash (FA) by volume. After 24 wk, soil amendments enhanced dry matter yield and increased chlorophyll content, leading to higher photosynthetic rate and rubisco activity in the leaves of citronella. These amendments reduced the availability of HM in tailings and consequently reduced its translocation to aboveground parts and the concentration in shoots. Cow manure, FA, and compost increased the total N, available P, and exchangeable K in tailings. Applications of FA, compost, lime, and cow manure significantly enhanced the survival and growth of citronella in tailings and thereby increased the potential of citronella as phytostabilization agents of Cu-Ni tailings. The high dry [ABSTRACT FROM AUTHOR]

Chemical fertilizers have been extensively used in Sri Lanka, and they have contributed to the pollution of groundwater and soil. Therefore, a field experiment was conducted to reduce the potential risk of toxic metal contamination of rice farming through sustainable nutrient management, with the scope of replacing the conventional chemical fertilizers. The field experiment comprised the addition of organic amendments, consortium of biofertilizers, and chemical fertilizers. Two improved rice varieties and three traditional rice varieties were grown. The plant-available and total Cd, As, Pb, and Hg in soil, rice roots, and grains in each system were analyzed. The results revealed that organic soil management is an effective soil remediation technique for rice soil to neutralize the toxic heavy metals (e.g. Pb, Hg, Cd) and metalloids (As) and lead to a harvest with minimum heavy metal contamination (p < 0.05). Natural soil amendments such as compost, biochar, and biofertilizers, which reduce the heavy metal concentrations of soil and rice grains, could be recommended for soil application, instead of chemical fertilizers, for both the traditional and the improved rice varieties. [ABSTRACT FROM AUTHOR]

Simple Summary: The utilization of organic wastes, for example, poultry waste, sugarcane press mud, and farmyard manure is extremely common among farmers from South Asia including Pakistan. We assess the biochemical nature and dietary benefit for plants and record the presence of heavy metals in garlic following cultivation in a soil amended with these organic wastes. Present investigation showed the grouping of toxicity and bioaccumulation of heavy metals with a particular link to their source of origin and highlight the hazard of some of them for public health through their excessive utilization. Selecting appropriate manure can significantly reduce health risks for humans. In South Asia, the high costs of synthetic fertilizers have imposed research on alternative nutrient inputs. We aimed to identify potential trace elements (PTE) present in some organic manure that might be a source of environmental pollutions and risk to public health following consumption. The study aims to evaluate how different organic waste (poultry waste, PW; press mud, PM; and farmyard manure, FYM) influences the heavy metal migration in soil, the accumulation in garlic, and their potential health risks. Organic waste caused a higher accumulation of certain metals (Zn, Cu, Fe, and Co), whereas Mn, Cd, Cr, and Pb were in lower concentrations in soil. Amendments of soil with PM revealed a higher accumulation of Cd, Cr, Fe, and Pb, whereas PW resulted in Cu and Zn accumulation in garlic. Treatment of soil with FYM exhibited higher metal concentration of Co and Mn. An environmental hazard indices study revealed that pollution load index (PLI) was highest for Cu following treatment with PM. The health risk index (HRI) was greater for Cd following amendment with PM. Maximum daily intake of metals (DIM) was observed for Zn after treatment with PW. The Pb exhibited maximum bioconcentration factor (BCF) in PM-amended plants. Based on these findings, we concluded that garlic grown on contaminated soil with organic waste may pose serious health hazards following consumption. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency in agricultural soil is a worldwide concern. P modification of biochar, a common soil conditioner produced by pyrolysis of wastes and residues, can increase P availability and improve soil quality. This study aims to investigate the effects of P-modified biochar as a soil amendment on the growth and quality of a medicinal plant (Pseudostellaria heterophylla). P. heterophylla were grown for 4 months in lateritic soil amended with P-modified and unmodified biochar (peanut shell) at dosages of 0, 3% and 5% (by mass). Compared with unmodified biochar, P-modified biochar reduced available heavy metal Cd in soil by up to 73.0% and osmotic suction in the root zone by up to 49.3%. P-modified biochar application at 3% and 5% promoted the tuber yield of P. heterophylla significantly by 68.6% and 136.0% respectively. This was different from that in unmodified biochar treatment, where tuber yield was stimulated at 3% dosage but inhibited at 5% dosage. The concentrations of active ingredients (i.e., polysaccharides, saponins) in tuber were increased by 2.9–78.8% under P-modified biochar amendment compared with control, indicating the better tuber quality. This study recommended the application of 5% P-modified biochar for promoting the yield and quality of P. heterophylla. [ABSTRACT FROM AUTHOR]

Petroleum substances are among the xenobiotics that most often contaminate the natural environment. They have a strong effect on soil, water, and other components of the environment. The aim of this pot experiment has been to determine the effect of different soil material amendments (compost, 3%; bentonite, 2% relative to the soil mass or calcium oxide, in amounts corresponding to one full hydrolytic acidity) on the content of heavy metals in aerial parts of maize (Zea mays L.) grown on soil polluted with petrol (0, 2.5, 5, and 10 cm3 kg−1 of soil). The content of all heavy metals, except copper, in the aerial biomass of maize was positively correlated, but biomass yield negatively correlated, with the increasing doses of petrol. The highest increase in the content of heavy metals was noted for chromium and manganese. Materials used for phytostabilisation (compost, bentonite, and calcium oxide) had a significant effect on the content of heavy metals and biomass yield of maize. They contributed to the modified accumulation of elements, especially chromium, copper, and cobalt in the aerial biomass of maize. In comparison with the control series (without material amendments), the application of calcium oxide proved to be most effective. It had the most evident influence on the chemical composition of maize, limiting the accumulation of lead, zinc, manganese, and iron and increasing biomass yield. [ABSTRACT FROM AUTHOR]

A large amount of waste material and tailings, generated from opencast mineral extraction, released different heavy metals and metalloids that polluted the mine surroundings soil. In the present investigation, an attempt was made to revegetate the open-cut mine affected area. Bulk soil samples were collected from derelict Frogmore tungsten mine site, and after physicochemical characterization of the soil samples, pot culture experiments were conducted in a green house. The different experimental soils like control soil, polluted soil, and polluted soil treated with the combined amendment, viz. Nano chailings (8 t/ha) + Nano composite of Zeolites + Nano Clay (Bentonite) (5%) + Nano composite of Zeolite + Zero valent iron (5%) + 5 t/ha FYM (Farm Yard Manure), were used in the investigation and maize (Zea mays L.) was taken as a test crop. This paper focused on amendments based on nano-enhanced materials. Amongst heavy metals like Cd, Ni, Zn, Cu, Pb, etc., Pb recorded the highest amount (125 mg/kg), which caused drastic reduction in different growth parameters of maize plant grown in mine spoiled soil. Microscopic structural changes, such as decrease in intercellular spaces, stomatal opening, shrinkage of palisade and epidermal cells, occurred in maize leaves grown in the mine polluted soil. Experimental results also revealed significant decrease in the fresh weight, dry weight, height, and girth of maize plants grown in mine spoiled soil. The contaminant distribution in the mine site should be considered in the design of management and remediation strategies. The possible practical consequences of these findings might be the application of nano-enhanced materials for the remediation and revegetation of the abandoned mine spoiled soils. [ABSTRACT FROM AUTHOR]

The study was investigated the influence of pyrolysis conditions on the yield and nutrient properties of yak dung-based biochar and its potential of agro-environmental applications. A series of biochars were made by hydrothermal carbonization (HTC) under the different atmospheres, such as Nitrogen (N2) and carbon dioxide (CO2), processing temperatures (200-300 °C) and residence times (1-2 h). The results showed the yield of yak dung-based biochar ranges from 35.33 wt% to 58.29 wt%. The concentration of nitrogen (N), phosphorus (P) and potassium (K) in biochar varied from 28.18 mg·g−1 to 15.54 mg·g−1, 16.23 mg·g−1 to 25.31 mg·g−1 and 0.59 mg·g−1 to 1.02 mg·g−1, respectively. And the contents of micronutrients Zn and Fe varied from 4.6 mg·g−1 to 17.42 mg·g−1, and 15.28 mg·g−1 to 29.22 mg·g−1, respectively. The yield, total carbon (C), N, hydrogen (H) and oxygen (O) content of biochar decreased with increasing processing temperature, while the total P and K content, pH and Brunauer-Emmett-Teller (BET) surface area increased; moreover, the P and K content of biochar produced in N2 increased more compared with CO2. The heavy metal contents of copper (Cu), cadmium (Cd), chromium (Cr), platinum (Pb) and arsenic (As) all were lower in yak dung-based biochar compare with other manures or sewage sludge-based biochar. Biochar produced in N2 had higher nutrient content indicating the potential of application for fertilizer compared with it in CO2; while the biochar produced in CO2 with larger surface area characteristic and more abundant functional groups showing higher potential of application for the soil amendments and nutrient control materials. Our study provides some new insights for biochar production according to its application. [ABSTRACT FROM AUTHOR]

The elevated level of metals in the soil increases the assimilation of these metals by plants causing a serious health risk to humans. A series of pot experiments were conducted to study Pb, Cu, and Zn uptake by Zea mays to investigate the role of vermiculite for metals immobilization in the soil root zone. The metals accumulation was decreased (13.17% to 29.21% in above-ground parts and 4.18% to 69.74% in roots) and total plant biomass increased (1.43% in control soil and 10.54% in polluted soil) in vermiculite amended soils. The effective immobilization of metals in vermiculite amended soil was revealed by decreased values of translocation factors for root-stalk and subsequently for stalk-leaves under varying metal concentrations. Vermiculite amendment to soil had no observable effect on the chemical structure while there were few changes in the functional group of the soil structure. The study reveals that vermiculite can be amended to the soil for reducing phytoavailability of toxic metals to plant uptake and in return flow processes for controlling food-chain contamination and groundwater pollution without compromising with crop production. [ABSTRACT FROM AUTHOR]

The potential of Colosphospermum mopane for phytoremediation of heavy metal (HM) contaminated soil was evaluated. C. mopane seedlings were planted on soils from the vicinity of Cu-Ni mine as affected by different soil amendments (Compost and fly ash-FA) and mycorrhizal inoculation in terms of growth and HM accumulation through a 2-factorial pot experiment. The survival and dry matter yield of C. mopane seedlings was enhanced by FA and compost as well as mycorrhiza. Soils with compost had high survival and dry matter yield and were enhanced by mycorrhiza. FA also enhanced the survival and dry matter yield but at lower magnitude. Except for Mn, FA and compost reduced the concentration of Cu, Ni, Pb, As, and Zn in shoots and roots of the C. mopane seedlings. Mycorrhiza reduced the Cu, Pb, Ni, and Zn concentrations in shoots but not with As. FA and compost modified the soil pH, EC, and the total and available contents of heavy metals in soil thus the difference in growth and uptake of HMs. Overall, results showed that FA or compost together with mycorrhiza can enhance the survival and growth of C. mopane seedlings in HM contaminated soils by reducing its availability and uptake by plants. [ABSTRACT FROM AUTHOR]

Prolonged wastewater irrigation in agriculture has led to the accumulation of heavy metals in soil, endangering both the soil quality and food safety, thereby posing a potential threat to human health through the consumption of contaminated crops. The present study aimed to enhance the yield of mustard (Brassica juncea L. cv. Varuna and NRCHB 101) plants and stabilize heavy metals (Cd, Cr, Ni, Cu, and Zn) in wastewater-irrigated soil using rice husk ash (RHA), rice mill by-product, collected from Chandauli region of Eastern Uttar Pradesh, India. Results demonstrated significant improvements in growth, biomass, physiology, and yield of mustard plant with increasing RHA application in wastewater irrigated soil (p ≤ 0.05). Heavy metal accumulation in different parts of mustard plants decreased as RHA application rate increased. Applying RHA at 2% in soil proved to be most effective in reducing Cd, Cr, Ni, Cu, and Zn accumulation in seeds by 29%, 29.6%, 23.1%, 21.3% and 20.1%, respectively in Varuna and 30.1%, 21.4%, 11.1%, 12.1%, and 28.5%, respectively in NRCHB 101cultivars. The present findings showed that RHA amendment in wastewater irrigated soil had reduced bioaccumulation of Cd, Cr, Ni, Cu, and Zn and consequently their toxicity in cultivated mustard plants. A novel application of RHA is unveiled in this research, offering a promising solution to promote sustainable agriculture and to reduce heavy metal associated health risks within the soil-mustard system. [Display omitted] • Effectiveness of rice husk ash amendment in soil-mustard system was investigated. • Rice husk ash application improved mustard growth in contaminated soil. • Soil pH and organic matter had negative relationships with heavy metals in seeds. • Use of Rice husk ash at the rate of 2% effectively reduced heavy metal in seeds. • Heavy metal contaminated soil can be remedied by using rice husk ash. [ABSTRACT FROM AUTHOR]

Metal(loid) contamination of agricultural soils has become an alarming issue due to its detrimental impacts on soil health and global agricultural production. Therefore, environmentally sustainable and cost-effective solutions are urgently required for soil remediation. Biochar, particularly nano-biochar, exhibits superior and high-performance capabilities in the remediation of metal(loid)-contaminated soil, owing to its unique structure and large surface area. Current researches on nano-biochar mainly focus on safety design and property improvement, with limited information available regarding the impact of nano-biochar on soil ecosystems and crop defense mechanisms in metal(loid)-contaminated soils. In this review, we systematically summarized recent progress in the application of nano-biochar for remediation of metal(loid)-contaminated soil, with a focus on possible factors influencing metal(loid) uptake and translocation in soil-crop systems. Additionally, we conducted the potential/related mechanisms by which nano-biochar can mitigate the toxic impacts of metal(loid) on crop production and security. Furthermore, the application of nano-biochar in field trials and existing challenges were also outlined. Future studies should integrate agricultural sustainability and ecosystem health targets into biochar design/selection. This review highlighted the potential of nano-biochar as a promising soil amendment for enhancing the remediation of metal(loid)-contaminated agricultural soils, thereby promoting the synthesis and development of highly efficient nano-biochar towards achieving environmental sustainability. • The direct and indirect effects of nano-biochar on metal(loid) immobilization were conducted. • Feedstock and doses of nano-biochar affect metal(loid) accumulation and translocation in crops. • Nano-biochar offers opportunities for soil remediation of metal(loid) contaminants and sustainable agriculture. [ABSTRACT FROM AUTHOR]

The lack of power resources leads to the rapid development of biomass power generation. Biomass power generation technology can not only rationally utilize biomass resources, but also alleviate energy crisis. But if this biomass ash is not handled properly, indiscriminate dumping can cause serious environmental problems such as dust, air and water pollution. The purpose of this study was to use the basic physical and chemical properties of biomass waste ash and biochar to evaluate the effects of mixed uses on soil pH、heavy metal remediation and plant growth. Plant growth was undertaken using ryegrass to examine the potential value of an ash-biochar mixture to ameliorate soil acidity and heavy metal pollution. The special fertilizer for rice was prepared by adding ammonium dihydrogen phosphate, potassium chloride, and urea to the ash and biochar. The results showed that the mixed use of ash and biochar could ameliorate soil acidification, reduce the absorption of cadmium and lead by the plants (43 % and 35 %, respectively), and promote plant growth. Determining of its total nutrients, soluble phosphorus, nitrate nitrogen, and particle size supported that it fell within the high concentration fertilizer range of the national standard for compound fertilizers. The special fertilizer can be used as high quality fertilizer to promote crop growth. In-depth research on the treatment and recycling of biomass power generation waste ash has an essential effect on reducing secondary environmental pollution and waste recycling.It can reduce random dumping, thereby reducing dust, air and water pollution. This was conducted to provide a reference for the preparation of soil amendments and to develop a better amendment and high-quality special fertilizer for rice with biomass waste ash and biochar. [Display omitted] • Ash and biochar addition increased soil pH and promoted plant growth. • Ash and biochar can inhibited cadmium uptake and lead by ryegrass. • Special fertilizers based on ash and biochar reach the quality fertilizer standards. • The special fertilizer improved soil fertility and rice growth. [ABSTRACT FROM AUTHOR]

Nowadays, special attention has been paid to remediate contaminated media through low-cost and high-efficiency biosorbents. In this research, the sorption of zinc (Zn2+) and copper (Cu2+) by cattle manure vermicompost (VC) and VC-amended soil and the effect of common ions on sorption was studied. The VC was characterized by using FT-IR spectra, SEM, BET analyses. Isotherm experiments were carried out with different concentrations of Zn2+ and Cu2+ (0–100 mg L−1) in the presence of 10 mM of background electrolytes (Ca2+, Mg2+, SO42-, and Cl−) as the binary system and the absence of other ions (single system). Data of Zn2+ and Cu2+ adsorption onto VC were fitted to the Langmuir equation. The maximum adsorption capacity (Qmax) of Zn2+ and Cu2+ onto VC in the single system was 7.27 and 17.73 mg g−1, respectively, which decreased in the following order Ca2+ > Mg2+ > SO42– > Cl – in the binary system. The effect of electrolytes on Zn2+ adsorption was more significant than Cu2+ and the Qmax of Zn2+ and Cu2+ decreased on average 20.4 and 10.8%, respectively. The VC addition increased adsorption in soil. Results indicate that VC had potential for the removal of Zn2+ and Cu2+ from single and binary systems. [ABSTRACT FROM AUTHOR]

Contaminations of heavy metals such as lead (Pb) and cadmium (Cd) in medicinal plants (MPs) not only restrict their safe consumption due to health hazards but also lower their productivity. Biochar amendments in the soil are supposed to immobilize the toxic metals, improve the soil quality, and agricultural productivity. However, the impact of biochar on growth attributes, metal accumulation, pharmacologically active compounds of MPs, and health risk is less explored. An experiment was performed on three medicinal plants [Bacopa monnieri (L.), Andrographis paniculata (Burmf.) Nees, and Withania somnifera (L.)] grown in a greenhouse in soil co‐contaminated with Pb and Cd (at two concentrations) without and with biochar amendments (2% and 4% application rates). The fractionation of Pb and Cd, plant growth parameters, stress enzymes, photosynthetic capacity, pharmacologically active compounds, nutrient content, uptake and translocation of metals, antioxidant activities, and metabolite content were examined in the three MPs. The accumulation of Pb and Cd varied from 3.25–228 and 1.29–20.2 mg kg−1, respectively, in the three MPs, while it was reduced to 0.08–18 and 0.03–6.05 mg kg−1upon biochar treatments. Plants grown in Pb and Cd co‐contaminated soil had reduced plant biomass (5%–50% depending on the species) compared to control and a deleterious effect on photosynthetic attributes and protein content. However, biochar amendments significantly improved plant biomass (21%–175%), as well as photosynthesis attributes, chlorophyll, and protein contents. Biochar amendments in Pb and Cd co‐contaminated soil significantly reduced the health hazard quotient (HQ) estimated for the consumption of these medicinal herbs grown on metal‐rich soil. An enhancement in secondary metabolite content and antioxidant properties was also observed upon biochar treatments. These multiple beneficial effects of biochar supplementation in Pb and Cd co‐contaminated soil suggested that a biochar amendment is a sustainable approach for the safe cultivation of MPs. [ABSTRACT FROM AUTHOR]

Rising global population and urbanization are major causes of waste generation, energy demand and carbon emissions. The atmospheric CO2 concentration has increased of 44% from 284 ppm in 1850 to 409 ppm in 2018. In 2017, the world energy consumption was 582 quadrillion British thermal units (qBtu), including 495 qBtu of fossil fuels and 87 qBtu of renewable and nuclear energy sources. Therefore, there is a need for new energies and methods of carbon sequestration, for instance by recycling biomass into biochar. Here, we review the thermochemical valorization of waste biomass by pyrolysis, gasification, torrefaction and carbonization to produce biochar with promising and environmental applications. We detail parameters that control biochar yields, quality and composition. Physical and chemical routes of biochar activation are also described. We focus on the utilization of biochar as soil amendment and for the adsorption of pollutants from wastewater. We conclude by a discussion on the techno-economic and lifecycle assessment of biochar production technologies. [ABSTRACT FROM AUTHOR]

The pot culture experiment for two consecutive years was conducted at Department of Soil Science and Agricultural Chemistry, MPKV, Rahuri to study the influence of various soil amendments on concentrations of heavy metals viz. Cd, Cr, Ni and Pb in berseem fodder crop. The pots were filled with soil irrigated with sewage water for more than thirty five years. The soil was treated with different amendments viz. FYM, gypsum, fly ash and their combinations. All the pots were supplied with recommended dose of chemical fertilizers by maintaining five plants per pot. The experiment was laid out in CRD with eight treatments and three replications. Initial soil properties were pHe 8.38, ECe 4.1 dSm-1, organic carbon 7.6 g kg-1, calcium carbonate 83.8 g kg-1, heavy metals viz. Cd, Cr, Ni and Pb were 0.35, 2.60, 2.23, 10.34 mg kg-1, respectively. Total four cuttings of berseem in each year were taken and analyzed for heavy metal concentrations. Two years pooled mean showed that, there was significant effect of different soil amendments on decreasing concentration of cadmium, chromium and lead as compared to control. Pooled mean of both years showed that the combined application of FYM + gypsum + fly ash each @ 10 g kg-1 soil (T8) registered significantly lower concentration of Cd, Cr and Pb in berseem as compared to rest of the treatments, but found at par with treatment (T5) FYM + gypsum each @ 10 g kg-1 soil. The reduction in concentrations of these heavy metals were higher in treatments where FYM was applied either alone or in combination with other amendments followed by gypsum and fly ash. Pooled mean values of two years showed significantly higher crude protein content due to application of FYM + gypsum + fly ash each @10 gkg-1 soil (T8 ) and at par with treatment T5. Pooled mean of two years showed numerically higher crude fiber due to treatment T8 (application of FYM + gypsum + fly ash each @ 10 g kg-1 soil) followed by T5 (application of FYM + gypsum each @ 10 g kg-1 soil). Significantly higher Acid Detergent Fiber (ADF) was recorded in T2 (application of FYM @10 g kg-1 soil) followed by T3 (application of gypsum @ 10 g kg-1 soil) treatment. [ABSTRACT FROM AUTHOR]

Chromite mining activities in Balochistan are causing serious heavy metal contamination in agricultural soils. Due to high adsorption capacity of biochar, its amendment in heavy metal-contaminated soils is known for reducing soil toxicity to crops. This pot-based study investigated influences of wood-derived biochar and farmyard manure-derived (cow dung-derived) biochar as mixtures with air-dried poultry manure on the growth and concentration of heavy metals in edible tissues of tomato and lettuce. These biochars were separately mixed with poultry manure as 1:1 ratio on air-dry weight bases. Soil was contaminated with chromite mine tailing debris at 2% amendment rate (980 g soil + 20 g debris). Biochar-poultry manure mixtures were applied in soil at 10% and 20% amendment rates (respectively, 900 g soil + 100 g mixture and 800 g soil and 200 g mixture of poultry manure and biochar in 1:1 mixture ratio). After harvest of tomato, lettuce was grown in the same soil. As compared to control, amendments of biochar-poultry manure mixtures had a significantly positive influence on growth of both crops. There was ~ 254.49% - 871.9% (~3.5 - 9 fold) increase in aboveground biomass of tomato and 25.67% - 94.59% increase in aboveground plant biomass of lettuce. These fertilizers also increased significantly water use efficiency by ~3.5 - 12.5 times (364.8% - 1166.6%) of tomato plants (as only tomato plants were analyzed for WUE). Furthermore, these amendments reduced concentration of heavy metals in plants of both crops. As compared to contaminated control treatment, amendment of biochar-poultry manure mixtures increased the concentration of soluble mineral phosphorus by 288% - 914% in soil. Our study suggests that amendment of wood-derived biochar and cow manure-derived biochar as mixtures with poultry manure, significantly improved growth of both crops and increased concentration of bioavailable phosphorus in soil. [ABSTRACT FROM AUTHOR]

Based on the literature and experimental results, three kinds of amendments, namely, rice biochar, hydroxyapatite and potassium dihydrogen phosphate(KH2PO4), and deeper ploughing were selected to evaluate the field application effect of soil amendments and agronomic measures on the remediation of Cd contamination in greenhouses. Cd-contaminated greenhouse screening was conducted from 2015 to 2017. In September 2017, comparative tests of eight treatments were performed in September 2017, and a selective test was performed in September 2018. The results of the screening of contaminated areas indicated that the distributions of over-standard sites and Cd content were significantly different. Greenhouse No. 4, in which the highest over-standard rate was 83.33% and the average content of Cd in soil was 0.535 mg/kg, was used as a comparative test experimental site for eight treatments. Greenhouse No. 1 was selected as the optimum test greenhouse for selective testing, with three plots having average Cd concentrations of 0.530, 0.568 and 0.792 mg/kg. The 8 months following comparative treatment showed that the content of available Cd following the treatment of rice biochar+hydroxyapatite+deeper ploughing(treatment T6) was reduced by 32.55% and 24.96% compared with the CK(the control) and 2 months following treatment, respectively. The content of available Cd using rice biochar+KH2PO4+deeper ploughing(treatment T7) treatment decreased by 47.88% and 31.00% compared with the CK and 2 months following treatment. The selective test results showed that in rice biochar+hydroxyapatite+deeper ploughing: the total Cd content of decreased from 0.489 to 0.372 mg/kg(23.86% lower), compared with the CK, and the mean content of available Cd decreased by 10.71% after 8 months, which was the lowest available Cd measured(0.133 mg/kg). In addition, the bean plant Cd content, bioconcentration factor(BCF) and translocation coefficient(TF) decreased by 15.86%, 23.68% and 25.77%, respectively. Rice biochar+hydroxyapatite+deeper ploughing is a favoured technology for the remediation of Cd-contaminated protected vegetable fields. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effect of cellulosic wastes and nanoscale zero-valent iron (nZVI) on the soil properties and the nutrient uptake by Quercus castaneifolia C.A.Mey seedlings. The seedlings were planted in pots (unpolluted soil) and cadmium (Cd) was added to the pots in three concentrations (10, 20, 30 mg.kg−1). Cellulosic wastes were mixed with the soil (at the same time as the planting) in four levels (W: 0, 10, 20, 30 g.100g−1 soil). The reduction method was used to prepare nZVI, then the nanoparticles were injected into the polluted pots in four levels (N: 0, 1, 2, and 3 mg.kg−1). The lowest concentration of Cd in leaves, stems and roots and for all the contamination levels was observed in N3. All the cellulosic wastes and N3 significantly increased the soil pH at all the levels of contamination. An increasing trend of the soil carbon (C) content was observed by adding the cellulosic wastes. The highest pH and C content were observed in W3. The lowest bioavailable Cd contents for all the contamination levels was observed in N3. According to the results, nZVI and cellulosic wastes could help the plants establishing in heavy metal-polluted lands. [ABSTRACT FROM AUTHOR]

• Compost, phosphate sludge, marble waste allowed alfalfa growth in metal-contaminated soil. • Rhizobacteria and/or mycorrhizae inoculation with amendments promoted safe cultivation. • The organic and mineral amendments reduced CaCl 2 -soluble Zn, Cu, and Pb concentrations. • Mineral amendments stimulated plant proline production and improved soil properties. Assisted natural remediation (ANR) has been highlighted as a promising, less expensive, and environmentally friendly solution to remediate soil contaminated with heavy metals. We tested the effects of three amendments (10% compost, C; 5 or 15% phosphate sludge, PS5 and PS15; and 5 or 15% marble waste, MW5 and MW15) in combination with microorganism inoculation (rhizobacteria consortium alone, mycorrhizae alone, and the two in-combination) on alfalfa in contaminated soil. Plant concentrations of Zn, Cu, and Pb were measured, along with proline and malondialdehyde production. The microbiological and physicochemical properties of the mining soil were evaluated. Application of the amendments allowed germination and promoted growth. Inoculation with the rhizobacteria consortium and/or mycorrhizae stimulated plant growth. PS and MW stimulated the production of proline. Inoculation of alfalfa with the rhizobacteria-mycorrhizae mixture and the application of MW allowed the safe cultivation of the legume, as shown by the low concentrations of metals in plant shoots. Zn and Pb concentrations were below the limits recommended for animal grazing and accumulated essentially in roots. Soil analyses showed the positive effect of the amendments on the soil physicochemical properties. All treatments increased soil pH (around 7), total organic carbon, and assimilable phosphorus content. Notably, an important decrease in soluble heavy metals concentrations was observed. Overall, our findings revealed that the applied treatments reduced the risk of metal-polluted soils limiting plant growth. The ANR has great potential for success in the restoration of polymetallic and acidic mining soils using the interaction between alfalfa, microorganisms, and organo-mineral amendments. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Objective: This research aimed to assay the dehydration and stabilization of surplus biosolids from a wastewater activated sludge treatment plant, with sludge-treatment wetlands, at the Iguazú National Park (Misiones, Argentina). Materials and Methods: A 12-cell sludge-treatment reed beds (STRB) system was built and operated for four years. Afterwards, the accumulated sediments were analyzed for total solids (TS) concentration, volatile solids (VS) reduction, specific oxygen-uptake rate (SOUR), and heavy metals and pathogens concentrations. Results and Discussion: TS concentration increased from 0.55 % to 14.3 %, VS were reduced by 33.3 %, and SOUR lowered to 1.09 mg O2gTS-1 h-1. These figures and the final concentrations of heavy metals and pathogenic microorganisms (102 MPN E.coli.gTS-1) indicated a degree of stabilization and sanitation that allowed classifying these biosolids as Class A, according to the Argentine guidelines, National Resolution 410/18, and enabled their reuse for soil amendment in landscapes and other agronomic purposes. Conclusion: The technology tested showed good results applied under a tropical climate, with annual temperatures between 17 and 27 °C, rainfall of 1870 mm y-1, and planted with autochthonous vegetation. Furthermore, it allowed the reuse of 221 t (144 m3 ) of a harmless product in an environmentally sustainable way. [ABSTRACT FROM AUTHOR]

Gas-to-liquid (GTL) sludge is a specific wastewater treatment by-product, which is generated during the industrial process of natural gas conversion to transportation fuels. This least studied sludge is pathogen-free and rich in organic carbon and plant nutrients. Therefore, it can be reused for soil enhancement as a sustainable management strategy to mitigate landfill gas emissions. In this field study, we compared the performance of soil treatments with GTL sludge to the more conventional chemical fertilizers and cow manure compost for the cultivation of cotton under hyperarid conditions. After a complete growing season, GTL sludge application resulted in the enhancement of soil properties and plant growth compared to conventional inputs. As such, there was a significant dose-dependent increase of soil organic matter (4.01% and 4.54%), phosphorus (534 and 1090 mg kg−1), and cumulative lint yield (4.68 and 5.67 t ha−1) for GTL sludge application rates of 1.5% and 3%, respectively. The produced fiber quality was adequate for an upland cotton variety (Gossypium hirsutum var. MAY 344) and appeared more dependent on the prevailing climate conditions than soil treatments. On the other hand, the adverse effects generally related to industrial sludge reuse were not significant and did not affect the designed agro-environmental system. Accordingly, plants grown on GTL sludge-amended soils showed lower antioxidant activity despite significant salinity increase. In addition, the concentrations of detected heavy metals in soil were within the standards' limits, which did not pose environmental issues under the described experimental conditions. Leachate analysis revealed no risks for groundwater contamination with phytotoxic metals, which were mostly retained by the soil matrix. Therefore, recycling GTL sludge as an organic amendment can be a sustainable solution to improve soil quality and lower carbon footprint. To reduce any environmental concerns, an application rate of 1.5% could be provisionally recommended since a two-fold increase in sludge dose did not result in a significant yield improvement. [Display omitted] • Gas-to-liquid sludge is a carbon-rich by-product of GTL wastewater treatment. • GTL sludge land application mitigates the risks of landfill gas emissions. • GTL sludge improves soil and plant properties under hyperarid conditions. [ABSTRACT FROM AUTHOR]

Soil quality deterioration and heavy metal contamination have greatly limited soil productivity in mining areas. As soil is a complex system with various properties and interactions, it is imperative to conduct a comprehensive investigation to understand the amendment's mechanisms at work in the soil in mining areas as well as effective ways to address its deteriorating quality. In this study, a potassium dihydrogen phosphate-modified maize straw-cow dung biochar (PBC) was applied as a soil amendment. Various physicochemical properties of the soil including organic matter, total nitrogen, available phosphorus, and pore characteristics were analyzed. This study also assessed soil-saturated water content and soil moisture characteristic curve. Lettuce biomass was measured and changes in various speciation of Pb and Cd in the soil, and the accumulation of Pb and Cd in lettuce were examined. Results showed that the addition of PBC increased soil organic matter, total nitrogen, and available phosphorus while reducing soil bulk density, it also increased soil porosity, saturated water content, and capillary water capacity. Soil structure analysis using CT scanning revealed that 3% PBC increased the macrospores volume fraction while 5% PBC made the pores more uniform. Lettuce biomass increased by 53.3%. 5% PBC resulted in a 56.79% and 38.30% reduction in Pb and a 44.56% and 16.60% reduction in Cd in roots and shoots of lettuce respectively. PBC facilitated the transformation of Pb and Cd from unstable fractions to stable fractions through complexation and precipitation. Overall, the addition of PBC effectively improved soil nutrients, porosity, and water-holding capacity, promoted plant growth, immobilized Pb and Cd, as well as reduced the bioavailability in contaminated-soil from mining areas. This study provides an effective strategy and a new perspective for the remediation of Pb–Cd-contaminated soils. [Display omitted] • An efficient method for the amendment of heavy metal-contaminated mining soil; • Soil water retention and pore structure has been improved by adding a phosphorus-modified biochar; • Soil saturated water content, organic matter, and total N content were the main factors affecting lettuce growth; • Increased Pb and Cd stable fractions restricted the migration of Pb and Cd from the soil to lettuce. • Lettuce biomass increased by 42.81–53.3%, while Pb and Cd contents reduced by 38.30–56.79% and 16.6–44.56%. [ABSTRACT FROM AUTHOR]

Here, tobermorite was prepared by a solvothermal technology using calcite and quartz with a mixed solvent of ethanol and water. Factors including reaction temperature, time and KOH content were studied to optimize the preparation procedure. To study the relationship between ethanol content-material structural characteristics-adsorption capacity, a series of materials were prepared in different mixed solvent proportions of ethanol and water, and their structural characteristics and adsorption capacity were compared. We found that the adsorption capacity of different samples for Pb2+ and Cd2+ was positively correlated with negatively correlated with the surface area and negatively correlated with the crystallinity of materials. Then, the material prepared by 30% ethanol solution (30-T) with the best adsorption performance was used for further research; the results were fitted by kinetic and thermodynamic models, and adsorbed materials were analyzed by various characterizations, suggesting that the adsorption process was ascribed to comprehensive pathways including ion exchange, chemical precipitation, and surface-complexation. Then, the 30-T was further used to remediate heavy metals contaminated soil, and the remediation effect was examined by the DTPA-extractable method and the European Community Bureau of Reference (BCR) sequential extraction method. The DTPA-extractable results showed that tobermorite observably reduced the bioavailability of Pb and Cd, and the BCR results suggested that the acid-soluble and reducible fractions of Pb and Cd were transformed to the oxidizable and residual fractions after remediation. In summary, tobermorite has great potential in the remediation of heavy metal polluted-aquatic environment/system and soil. • Tobermorite was successfully prepared in mixed solvent of ethanol and water. • Tobermorite was used to remove Pb2+ and Cd2+ in the water. • The adsorption mechanism was ascribed to comprehensive pathways. • The amendment reduced soil acidity and the bioavailable Pb and Cd in soil. • Tobermorite could translate Pb and Cd in soil to more stable fractions. [ABSTRACT FROM AUTHOR]

The release of metal-based nanoparticles (MNPs) into sewage systems is worrisome due to their potential impact on crop-soil systems that are amended with sewage sludge. This study aimed to investigate the effects of copper oxide nanoparticles (CuO NPs) in composted sewage sludge (CSS) on rice-soil systems and to assess the health risks associated with consuming CuO NP-contaminated rice produced by CSS amendment. CSS was treated with three doses of CuO NPs, resulting in Cu levels below the sludge limits (1500 mg Cu kg−1) for reuse as a soil amendment. Results showed that CuO NPs in CSS at environmentally acceptable levels had no negative effect on rice growth and yield. In fact, they enhanced biomass production, tillering capacity, and soil fertility by increasing N and K levels in the soil. In addition, CuO NPs in CSS (450–1450 mg Cu kg−1) promoted the accumulation of macro- and micro-minerals in rice grains, thereby improving the nutritional value of rice. However, Cu contamination in CSS led to elevated levels of toxic metals, especially As, in rice grains, posing potential health risks to both adults and children. In the presence of higher CuO NPs contamination in CSS, the hazard quotient of As exceeded one, indicating an increased risks of toxic metal exposure via rice consumption. This study raises concerns about potential long-term threats to human health posed by MNPs contamination in CSS and highlights the need to reevaluate the permissible limits of hazardous elements in sludge to ensure its safe reuse in agriculture. [Display omitted] • CuO nanoparticles (NPs) in sewage sludge didn't harm rice growth, yield or quality. • CuO NPs increased biomass production, tillering capacity, and soil N and K levels. • Elevated CuO NP contamination increased contents of potentially toxic metals in rice. • Hazard index values exceeded one and increased with CuO NPs levels in sludge. • It is critical to re-assess heavy metal limits in sludge for safe agricultural use. [ABSTRACT FROM AUTHOR]

This study investigated the effect of 3 biochar application rates (1%, 5%, and 10%) on the pH, surface charge, and bioavailability of Cu, Pb, Zn on a degraded Acrisols soil and their accumulation in water spinach (Ipomoea aquatica). After an incubation period of 28 days, a titration experiment confirmed that increasing the biochar application rates enhanced the negative charge along with an increased pH. In an experiment spiked with metals, the 0.01 M CaCl2-extractability of the metals after incubation significantly decreased with the increasing rate of biochar additions. This is mostly attributed to a rise in the soil pH and an increase in the negative charge as result of the biochar additions. Metal extractability continued to decrease over the next 1,344 h, most probably due to the aging effect. Immobilization speeds exhibited in the order Pb>Cu>Zn, can be partially attributed to the bigger ionic radius of Pb compared to those of Cu and Zn. By the end of incubation period, extractable Cu, Pb and Zn was significantly reduced, irrespective rates of biochar application 1%, 5% or 10%. In a greenhouse experiment, water spinach was unable to grow in the 10%biochar addition because of a high alkaline pH of 9.2. The Cu, Pb, and Zn concentrations and bioaccumulation factor in the grown water spinach decreased along with the increasing biochar application rates in the order 5%>1%>0%, showing a good agreement with the 0.01 M CaCl2-extractable concentrations. The bioaccumulation factors of Pb were far less than those of Cu and Zn, reflecting the immobilization speeds as concluded in the incubation tests. Therefore, biochar amendment into degraded soil for metal immobilization is feasible, provided the appropriate rate for crop growth is applied. [ABSTRACT FROM AUTHOR]

The seed germination plant growth parameters and level of heavy metal accumulation were investigated in pakchoi cultured in four contaminated soils with different levels of heavy metals supplemented with citric acid (CA) or calcium phosphate (CP). Results showed that the seed germination energy, germination percentage and germination index parameters were similar, while the seed vigor (SV) significantly (p < 0.05) decreased as the soil pollution level increased. The lengths of the shoots and roots presented the same trend as SV. All the seedlings grew in heavily polluted soil without any amendments before harvesting; therefore, no plant material was available for subsequent analyses. The photosynthesis parameters of pakchoi cultured in lightly polluted soil without amendment (LPS), lightly polluted soil with CA (LPSA) and moderately polluted soil with CP (MPSP) were similar. The concentrations of Pb, Zn, Mn, Cu and Cd in the shoots, roots and whole plants were in the order of MPSP > LPSA > LPS. Pakchoi cultured in MPSP showed the most promising results in terms of plant height, biomass and heavy metal accumulation. Pakchoi presented the highest translocation and bioaccumulation factors for Cd and the lowest for Pb. Soil pollution and the type of chemical amendment had no effect on the seed germination of pakchoi. Citric acid addition in lightly polluted soil improved pakchoi growth and heavy metal extraction. Pakchoi cultured in moderately polluted soil with calcium phosphate amendment presented the highest biomass and heavy metal concentration. [ABSTRACT FROM AUTHOR]