Interactive effects of biochar and mussel shell activated concoctions on immobilization of nickel and their amelioration on the growth of rapeseed in contaminated aged soil

The effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea mays L.) exposed to nickel stress

The issue of heavy metal pollution such as nickel poses a significant environmental concern, exerting detrimental effects on the growth and viability of plant life. Plants have various mechanisms to effectively manage heavy metal stress, including the ability to modify their amino acid type and content. This adaptive response allows plants to mitigate the detrimental effects caused by excessive heavy metal accumulation. The aim of this study was to investigate the effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea mays L.) cv. 'PL438' exposed to Ni stress. After disinfecting and soaking in water for 24 h, corn seeds were primed with bacterial biofertilizers (T2: NPK + FZ), fungal biofertilizers (T3: Arbuscular mycorrhizal fungi (AMF) + Trichoderma (T)), or a combination of them (T4: NPK + FZ + AMF + T) and were cultured by the hydroponic method in completely controlled conditions. Then, they were simultaneously exposed to nickel chloride at various rates (0, 75, or 150 µM) at the three-leaf stage. They were harvested two weeks later and were subjected to the measurement of Ni content, nitrate and nitrite content, nitrate reductase activity, and amino acid profile by high-performance liquid chromatography. The results showed that the application of Ni at higher rates increased Ni, nitrate, and nitrite contents and nitrate reductase activity. The study of Ni accumulation and TF revealed that Ni accumulated in the roots to a greater extent than in the shoots and TF was < 1 in all treatments. The shoot amino acid profile showed that the treatment of Ni+2 increased som amino acids such as aspartic acid, asparagine, serine, histidine, and glycine versus the control, whereas T4 Ni+2 increased aspartic acid, glutamic acid, threonine and arginine. The change in amino acids in Ni-treated plants may play a key role in their adaptation to Ni stress. The findings indicate that biofertilizers played a crucial role in mitigating the negative impacts of Ni on corn plants through alterations in amino acid composition and decreased absorption and translocation of Ni.

Biochar as a partner of plants and beneficial microorganisms to assist in-situ bioremediation of heavy metal contaminated soil

Synergistic remediation of heavy metal (HM) contaminated soil using beneficial microorganisms (BM) and plants is a common and effective in situ bioremediation method. However, the shortcomings of this approach are the low colonisation of BM under high levels of heavy metal stress (HMS) and the poor state of plant growth. Previous studies have overlooked the potential of biochar to mitigate the above problems and aid in-situ remediation. Therefore, this paper describes the characteristics and physicochemical properties of biochar. It is proposed that biochar enhances plant resistance to HMS and aids in situ bioremediation by increasing colonisation of BM and HM stability. On this basis, the paper focuses on the following possible mechanisms: specific biochar-derived organic matter regulates the transport of HMs in plants and promotes mycorrhizal colonisation via the abscisic acid signalling pathway and the karrikin signalling pathway; promotes the growth-promoting pathway of indole-3-acetic acid and increases expression of the nodule-initiating gene NIN; improvement of soil HM stability by ion exchange, electrostatic adsorption, redox and complex precipitation mechanisms. And this paper summarizes guidelines on how to use biochar-assisted remediation based on current research for reference. Finally, the paper identifies research gaps in biochar in the direction of promoting beneficial microbial symbiotic mechanisms, recognition and function of organic molecules, and factors affecting practical applications.

Mechanism and synergistic effect of sulfadiazine (SDZ) and cadmium toxicity in spinach (Spinacia oleracea L.) and its alleviation through zinc fortification

Cadmium (Cd) and antibiotic's tendency to accumulate in edible plant parts and fertile land is a worldwide issue. The combined effect of antibiotics and heavy metals on crops was analyzed, but not mitigation of their toxicity. This study investigated the potential of zinc oxide nanoparticles (ZnO NPs) to alleviate the SDZ and Cd toxicity (alone/combined) to promote spinach growth. Results revealed that the ZnO 200 mg L-1 spray decreased the malondialdehyde (MDA) 14%, hydrogen peroxide (H2O2) 13%, and electrolyte leakage (EL) 7%, and increased the superoxide dismutase (SOD) 8%, peroxidase (POD) 25%, catalase (CAT) 39% and ascorbate peroxidase (APX) 12% in spinach leaves under combined SDZ+Cd (25 mg Kg-1 +50 mg Kg-1) stress compared to ZnO 100 mg L-1 spray. Likewise, ZnO NPs 200 mg L-1 spray enhanced the zinc (Zn) 97%, iron (Fe) 86%, magnesium (Mg) 35%, manganese (Mn) 8%, and potassium (K) 23% in shoots under combined SDZ+Cd (25 mg Kg-1 +50 mg Kg-1) stress compared to ZnO 100 mg L-1 spray. Further, ZnO 200 mg L-1 spray reduced Cd uptake in roots by 9% and shoots 15% under combined SDZ+Cd (25 mg Kg-1 +50 mg Kg-1) stress compared to ZnO 100 mg L-1. Overall, ZnO NPs alleviated the SDZ and Cd toxicity and enhanced spinach growth in all treatments.

Application of biochar and humic acid improves the physiological and biochemical processes of rice (Oryza sativa L.) in conferring plant tolerance to arsenic-induced oxidative stress

Biochar (BC) and humic acid (HA) are well-documented in metal/metalloid detoxification, but their regulatory role in conferring plant oxidative stress under arsenic (As) stress is poorly understood. Therefore, we aimed at investigating the role of BC and HA (0.2 and 0.4 g kg-1 soil) in the detoxification of As (0.25 mM sodium arsenate) toxicity in rice (Oryza sativa L. cv. BRRI dhan75). Arsenic exhibited an increased lipid peroxidation, hydrogen peroxide, electrolyte leakage, and proline content which were 32, 30, 9, and 89% higher compared to control. In addition, the antioxidant defense system of rice consisting of non-enzyme antioxidants (18 and 43% decrease in ascorbate and glutathione content) and enzyme activities (23-50% reduction over control) was decreased as a result of As toxicity. The damaging effect of As was prominent in plant height, biomass acquisition, tiller number, and relative water content. Furthermore, chlorophyll and leaf area also exhibited a decreasing trend due to toxicity. Arsenic exposure also disrupted the glyoxalase system (23 and 33% decrease in glyoxalase I and glyoxalase II activities). However, the application of BC and HA recovered the reactive oxygen species-induced damages in plants, upregulated the effectiveness of the ascorbate-glutathione pool, and accelerated the activities of antioxidant defense and glyoxalase enzymes. These positive roles of BC and HA ultimately resulted in improved plant characteristics with better plant-water status and regulated proline content that conferred As stress tolerance in rice. So, it can be concluded that BC and HA effectively mitigated As-induced physiology and oxidative damage in rice plants. Therefore, BC and HA could be used as potential soil amendments in As-contaminated rice fields.

Synergistic effect of biochar-based compounds from vegetable wastes and gibberellic acid on wheat growth under salinity stress

Soil salinization is a prevalent form of land degradation particularly in water-deficient regions threatening agricultural sustainability. Present desalinization methods demand excessive water use. Biochar has been recognized as a potential remedy for saline soils and Gibberellic acids (GA3) are known to mediate various biochemical processes aiding in stress mitigation. This study was undertaken at The Islamia University of Bahawalpur during winter 2022-23 to explore the combined effect of biochar and GA3 on wheat (Triticum aestivum L.) in saline conditions. Employing a fully randomized design wheat seeds in 24 pots were subjected to two salinity levels with three replications across eight treatments: T1 to T8 ranging from controls with different soil electrical conductivities (ECs) to treatments involving combinations of GA3, biochar and varying soil ECs. These treatments included T1 (control with soil EC of 2.43dS/m), T2 (salinity stress with soil EC of 5.11dS/m), T3 (10 ppm GA3 with soil EC of 2.43dS/m), T4 (10 ppm GA3 with soil EC of 5.11dS/m), T5 (0.75% Biochar with soil EC of 2.43dS/m), T6 (0.75% Biochar with soil EC of 5.11dS/m), T7 (10 ppm GA3 combined with 0.75% biochar at soil EC of 2.43dS/m) and T8 (10 ppm GA3 plus 0.75% biochar at soil EC of 5.11dS/m). The results indicated that the combined applications of GA3 and biochar significantly enhanced plant growth in saline conditions viz. germination rate by 73%, shoot length of 15.54 cm, root length of 4.96 cm, plant height of 16.89 cm, shoot fresh weight 43.18 g, shoot dry weight 11.57 g, root fresh weight 24.26 g, root dry weight 9.31 g, plant water content 60.77%, photosynthetic rate 18.58(CO2 m-2 s-1) carotenoid 3.03 g, chlorophyll a 1.01 g, chlorophyll b 0.69 g, total chlorophyll contents by 1.9 g as compared to the control. The findings suggest that the combined application of these agents offers a sustainable and effective strategy for cultivating wheat in saline soils. The synergy between biochar and GA3 presents a promising avenue for sustainable wheat cultivation in saline conditions. This combined approach not only improves plant growth but also offers an innovative, water-efficient solution for enhancing agricultural productivity in saline-affected regions.

Nickel (Ni) phytotoxicity and detoxification mechanisms: A review

Scientists studying the environment, physiology, and biology have been particularly interested in nickel (Ni) because of its dual effects (essentiality and toxicity) on terrestrial biota. It has been reported in some studies that without an adequate supply of Ni, plants are unable to finish their life cycle. The safest Ni limit for plants is 1.5 μg g^-1, while the limit for soil is between 75 and 150 μg g^-1. Ni at lethal levels harms plants by interfering with a variety of physiological functions, including enzyme activity, root development, photosynthesis, and mineral uptake. This review focuses on the occurrence and phytotoxicity of Ni with respect to growth, physiological and biochemical aspects. It also delves into advanced Ni detoxification mechanisms such as cellular modifications, organic acids, and chelation of Ni by plant roots, and emphasizes the role of genes involved in Ni detoxification. The discussion has been carried out on the current state of using soil amendments and plant-microbe interactions to successfully remediate Ni from contaminated sites. This review has identified potential drawbacks and difficulties of various strategies for Ni remediation, discussed the importance of these findings for environmental authorities and decision-makers, and concluded by noting the sustainability concerns and future research needs regarding Ni remediation.

Biometric and gonadosomatic indices and chemical constituents of edible tissues and exoskeletons of Callinectes amnicola and their potential for reuse in the circular economy paradigm

The study investigates some biological indices and chemical compositions of Callinectes amnicola and their potential for reuse in the context of the circular economy paradigm. The total of 322 mixed-sex C. amnicola collected over a period of six months was examined. The morphometric and meristic characteristics were estimated for biometric assessment. The gonads were obtained from the female crabs for gonadosomatic indices. The shell was obtained using the hand removal technique by detaching it from the crab body. The edible and shell portions were processed separately and subjected to chemical analysis. Our findings showed that females had the highest sex ratio across the six months. The slope values (b) for both sexes exhibited negative allometric growth across all months since the slope values obtained were less than 3 (b < 3). The values obtained for Fulton's condition factor (K) of crabs in all examined months were greater than 1. The edible portion had the highest moisture level at 62.57 ± 2.16% and varied significantly (P < 0.05). The high amount of total ash obtained in the shell sample showed that ash is the main mineral present in crab shells and showed a significant difference (P < 0.05). The shell sample had the highest concentrations of Na and CaCO₃. Based on the findings of this study, it was observed that the shell waste contains some essential and transitional minerals (Ca, CaCO₃, Na, and Mg) and can be utilized as catalysts in several local and industrial applications, such as pigments, adsorbents, therapeutics, livestock feeds, biomedical industries, liming, fertilization, and so on. Proper valorization of this shell waste should be encouraged rather than discarding it.

Comparative efficacy of Parthenium hysterophorus (L.) derived biochar and iron doped zinc oxide nanoparticle on heavy metals (HMs) mobility and its uptake by Triticum aestivum (L.) in chromite mining contaminated soils

In this study we investigated the efficacy of a novel material parthenium weed (Parthenium hysterophorus L.) biochar (PBC), iron doped zinc oxide nanoparticles (nFe-ZnO), and biochar modified with nFe-ZnO (Fe-ZnO@BC) to adsorb heavy metals (HMs) and reduce their uptake by wheat (Triticum aestivum L.) in a highly chromite mining contaminated soil. The co-application of the applied soil conditioners exhibited a positive effect on the immobilization and restricted the HMs uptake below their threshold levels in shoot content of wheat. The maximum adsorption capacity was because of large surface area, cation exchange capacity, surface precipitation, and complexation of the soil conditioners. The scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed porous smooth structure of parthenium weed derived biochar that helped in HMs adsorption, increase the efficiency of soil fertilizers and nutrients retention which help in the enhancement soil condition. Under different application rates the highest translocation factor (TFHMs) was obtained at 2 g nFe-ZnO rate followed the descending order: Mn > Cr > Cu > Ni > Pb. The overall TFHMs was found <1.0 indicating that low content of HMs accumulation in roots from soil slight transferred to shoot, thus satisfying the remediation requirements.

Effects of biochar-based materials on nickel adsorption and bioavailability in soil

The potential for toxic elements to contaminate soil has been extensively studied. Therefore, the development of cost-effective methods and materials to prevent toxic element residues in the soil from entering the food chain is of great significance. Industrial and agricultural wastes such as wood vinegar (WV), sodium humate (NaHA) and biochar (BC) were used as raw materials in this study. HA was obtained by acidizing NaHA with WV and then loaded onto BC, which successfully prepared a highly efficient modification agent for nickel-contaminated soil, namely biochar-humic acid material (BC-HA). The characteristics and parameters of BC-HA were obtained by FTIR, SEM, EDS, BET and XPS. The chemisorption of Ni(II) ions by BC-HA conforms to the quasi-second-order kinetic model. Ni(II) ions are distributed on the heterogeneous surface of BC-HA by multimolecular layer adsorption, which accords with the Freundlich isotherm model. WV promotes better binding of HA and BC by introducing more active sites, thus increasing the adsorption capacity of Ni(II) ions on BC-HA. Ni(II) ions in soil are anchored to BC-HA by physical and chemical adsorption, electrostatic interaction, ion exchange and synergy.

Recent advances in biochar amendments for immobilization of heavy metals in an agricultural ecosystem: A systematic review

Over the last several decades, extensive and inefficient use of contemporary technologies has resulted in substantial environmental pollution, predominantly caused by potentially hazardous elements (PTEs), like heavy metals that severely harm living species. To combat the presence of heavy metals (HMs) in the agrarian system, biochar becomes an attractive approach for stabilizing and limiting availability of HMs in soils due to its high surface area, porosity, pH, aromatic structure as well as several functional groups, which mostly rely on the feedstock and pyrolysis temperature. Additionally, agricultural waste-derived biochar is an effective management option to ensure carbon neutrality and circular economy while also addressing social and environmental concerns. Given these diverse parameters, the present systematic evaluation seeks to (i) ascertain the effectiveness of heavy metal immobilization by agro waste-derived biochar; (ii) examine the presence of biochar on soil physico-chemical, and thermal properties, along with microbial diversity; (iii) explore the underlying mechanisms responsible for the reduction in heavy metal concentration; and (iv) possibility of biochar implications to advance circular economy approach. The collection of more than 200 papers catalogues the immobilization efficiency of biochar in agricultural soil and its impacts on soil from multi-angle perspectives. The data gathered suggests that pristine biochar effectively reduced cationic heavy metals (Pb, Cd, Cu, Ni) and Cr mobilization and uptake by plants, whereas modified biochar effectively reduced As in soil and plant systems. However, the exact mechanism underlying is a complex biochar-soil interaction. In addition to successfully immobilizing heavy metals in the soil, the application of biochar improved soil fertility and increased agricultural productivity. However, the lack of knowledge on unfavorable impacts on the agricultural systems, along with discrepancies between the use of biochar and experimental conditions, impeded a thorough understanding on a deeper level.

Influences of lithium on soil properties and enzyme activities

Lithium is an emerging environmental contaminant under the current sustainable energy strategy, but little is known about its contamination characteristic in soil. In this study, soil properties and enzyme activities in soils treated with 10-1280 mg kg^-1 lithium were measured. The results showed that the content of ammonium nitrogen, total nitrogen, and exchangeable potassium significantly increased by 64.39%-217.73%, 23.06%-131.86%, and 4.76%-16.10%, while electric conductivity and available phosphorus content in lithium treated soils was respectively as 1.10-fold-13.44-fold and 1.27-fold-6.66-fold comparing to CK value. Soil pH and cation exchange capacity slightly declined and increased, respectively, and there was no significant variation in total organic carbon. However, nitrate nitrogen and sulfate content significantly decreased under higher lithium stress. On the other hand, lower lithium treatment level of 10, 20, 40, or 80 mg kg^-1 selectively promoted the activities of sucrase, urease, aryl sulfatase, and peroxidase, while the protease, neutral phosphatase, phytase, and lipase were significantly inhibited under all lithium levels, indicating a weaken geochemical cycling of carbon, nitrogen, phosphorus, and sulfur. Then, lithium's 10% and 50% ecological dose (ED10 and ED50) was respectively fitted as 21.18 and 1408.67 mg kg^-1 basing on Geometric Mean Index. The influences of lithium on soil were adverse. This study provided important insights into understanding the characteristics of lithium contamination, informing risk assessment and guiding remediation.

A critical review on biochar-assisted free radicals mediated redox reactions influencing transformation of potentially toxic metals: Occurrence, formation, and environmental applications

Potentially toxic metals have become a viable threat to the ecosystem due to their carcinogenic nature. Biochar has gained substantial interest due to its redox-mediated processes and redox-active metals. Biochar has the capacity to directly adsorb the pollutants from contaminated environments through several mechanisms such as coprecipitation, complexation, ion exchange, and electrostatic interaction. Biochar's electron-mediating potential may be influenced by the cyclic transition of surface moieties and conjugated carbon structures. Thus, pyrolysis configuration, biomass material, retention time, oxygen flow, and heating time also affect biochar's redox properties. Generally, reactive oxygen species (ROS) exist as free radicals (FRs) in radical and non-radical forms, i.e., hydroxyl radical, superoxide, nitric oxide, hydrogen peroxide, and singlet oxygen. Heavy metals are involved in the production of FRs during redox-mediated reactions, which may contribute to ROS formation. This review aims to critically evaluate the redox-mediated characteristics of biochar produced from various biomass feedstocks under different pyrolysis conditions. In addition, we assessed the impact of biochar-assisted FRs redox-mediated processes on heavy metal immobilization and mobility. We also revealed new insights into the function of FRs in biochar and its potential uses for environment-friendly remediation and reducing the dependency on fossil-based materials, utilizing local residual biomass as a raw material in terms of sustainability.

Zinc fortification and alleviation of cadmium stress by application of lysine chelated zinc on different varieties of wheat and rice in cadmium stressed soil

Sustainable and cost-effective methods are required to increase the food production and decrease the toxic effects of heavy metals. Most of the agriculture land is contaminated with cadmium (Cd). The present study was designed to minimize the toxic effect of Cd stress (0, 10 and 20 mg kg1-) on tolerant and sensitive varieties of wheat (Punjab-2011; Sammar) and rice (Kisan Basmati; Chenab) under Zn-lysine (Zn-lys) application as foliar spray (0, 12.5 and 25 mM) and seed priming (0, 3 and 6 ppm). Remarkable decrease was observed in plant growth, physiology and biochemistry as well as increase in Cd uptake, roots to shoots and grains of both crops. Cd significantly reduced the root and shoot lengths, root and shoot dry weights, transpiration rate, photosynthetic rate, stomatal conductance and water use efficiency as well as chlorophyll contents associated with enhanced electrolyte leakage (EL), malondialdehyde (MDA) and H2O2 and Cd uptake in different plant parts including grains of both crop varieties. The foliar application of Zn-lys (0, 12.5 and 25 mM) ameliorated the toxic effect of Cd on growth and physiology associated with decrease in EL, MDA and H2O2 and improved the activities of SOD, POD, CAT and APX enzymes with decreasing Cd uptake in tolerant varieties of wheat and rice as compared to seed priming. Furthermore, it has been investigated that the foliar application of Zn-lys is effective to improve quality of wheat and rice tolerant varieties (Punjab-2011 and Chenab) under Cd contamination soils.

Alleviation of adverse effects of nickel on growth and concentration of copper and manganese in wheat through foliar application of ascorbic acid

We investigated the role of ascorbic acid (AsA) to alleviate nickel (Ni) induced adverse effects on growth and concentration of Ni, copper (Cu), and manganese (Mn) in hydroponically grown wheat varieties viz. Galaxy, Punjab-2011, and FSD-08. Plants were exposed to five levels of Ni viz. 0, 5, 10, 15, and 20 mg L^-1. After 1 week, AsA (1 mM) was sprayed onto the Ni-stressed plants. FSD-08 produced the maximum SDW with and without AsA compared to other varieties. FSD-08, Galaxy, and Punjab-2011 witnessed 2.61-, 2.83-, and 7.5-fold increases in SDW with AsA, respectively. Wheat plants contained the maximum Ni in shoots and roots with a Ni level of 20 mg L^-1 irrespective of varieties. Nickel in shoots decreased with AsA witnessing 13, 12, and 10% decrease in FSD-08, Punjab-2011, and Galaxy, respectively. Nickel in roots of FSD-08 decreased by 18% while increased by 3.34-fold and 3.50-fold in Galaxy and Punjab-2011, respectively with AsA. Nickel decreased Cu in shoot and Mn in shoot and root while Cu in roots of all wheat varieties increased. It was concluded that AsA improved the growth of Ni-stressed and FSD-08 performed better by maintaining good growth and less Ni in shoots compared to other varieties.