Remediation of soil polluted with Pb and Cd and alleviation of oxidative stress in Brassica rapa plant using nanoscale zerovalent iron supported with coconut-husk biochar

Enhanced tetracycline removal from aqueous systems using starch-functionalized iron-graphene oxide nanocomposites: Synthesis, characterization, and mechanistic insights

The increasing presence of tetracycline antibiotics in aquatic ecosystems poses a critical environmental challenge, necessitating innovative remediation strategies. This study presents the development and characterization of starch-functionalized iron-graphene oxide (SFIGO) and starch-functionalized iron oxide (SFIO) nanocomposites adsorbents for tetracycline removal from water, with emphasis on sustainable synthesis and enhanced performance. Biluochun tea and cassava extract were used as renewable precursors in green synthesis to create a composite material that combines iron oxide's magnetic properties, graphene oxide's high surface area, and starch's biocompatibility. Comprehensive characterization using FTIR, XRD, SEM-EDX, TEM, and XPS revealed SFIGO's unique hierarchical architecture, featuring wrinkled graphene oxide sheets with well-dispersed iron-oxide nanoparticles. Batch adsorption studies demonstrated SFIGO's superior performance, achieving a maximum adsorption capacity of 865.79 mg/g at 298 K, significantly higher than SFIO's 634.83 mg/g. The adsorption process followed pseudo-second-order kinetics and showed endothermic behavior, with negative Gibbs free energy values, confirming process spontaneity. Multiple binding mechanisms, including π-π interactions, electrostatic attractions, and surface complexation, contributed to SFIGO's enhanced performance. The material demonstrated robust performance across various water matrices and maintained high removal efficiency. These findings advance our understanding of composite materials in environmental remediation and provide a sustainable solution for pharmaceutical pollutant removal.

An empirical and statistical investigation on decarbonizing groundwater using industrial waste-based biochar: Trading-off zero-waste management and zero-emission target

This study recommended a trade-off between zero-waste management of a brewery industry and zero-aim target of the drinking water sector. This study mainly aimed to decrease the carbon dioxide (CO2) emissions resulting from groundwater treatment using biochar derived from malt sprout (MS) which is a waste by-product of a brewery industry. Also, CO2 resulting from groundwater treatment was collected and gas adsorption was performed to define the CO2 adsorption capacity of each biochar. Data Envelopment Analysis (DEA) was performed to determine the effect of groundwater quality on CO2 emissions. In the result of experimental and computational analysis, a new carbon capture indicator (CCIB) was derived depending on biochar adsorption process, in this study. The results revealed that averagely 28.98 % of reduction on CO2 emission from groundwater treatment was reported using the mixture of three malt sprout derived biochar. MS1 had the highest carbon capture capacity which was derived at 300 °C. According to (DEA) results, the optimum total organic carbon (TOC) should be 3.2 mg/L for the minimum CO2 emission. Also, optimum biochar dose, contact time and gas flow were 8 g, 10 min and 965 mL/d, respectively for the maximum CO2 adsorption by biochar according to Box-Behnken design method.

Monte Carlo simulation framework for assessing heavy metal exposure and adverse health effects in fly-in fly-out workers

Heavy metals (HMs) are persistent, non-biodegradable pollutants in airborne particulate matter (PM) that pose serious health risks. Fly-in fly-out (FIFO) workers, exposed to prolonged pollution, are especially at risk, yet their health risks remain underexplored. This study develops a framework to assess HMs exposure and health risks in FIFO workers. Over 12 months, samples of six HMs (Fe, Zn, Cd, As, Ni, Pb), were collected from indoor and outdoor environments at a major FIFO worksite in Bushehr, Iran. health risks, including cancer and other diseases, were estimated using Monte Carlo simulation. FIFO workers faced 21.42 % higher health risks than drive-in drive-out (DIDO) workers, with Pb (0.11 ± 0.194 μg/m3) as the most significant factor, showing a hazard quotient (HQ) of 2.88 and cancer risk (CR) of 1.28E-05. Indoor FIFO workers had 11 % lower health risks than outdoor workers, primarily due to reduced exposure to As (0.03 ± 0.02 μg/m3), strongly linked to cancer, with HQ of 7.89 and CR of 5.04E-04. Ni (0.027 ± 0.036 μg/m3) was the main contributor to non-cancerous hazards, with HQ of 26.1 and CR of 6.50E-05, while Cd (0.005 ± 0.004 μg/m3) showed a significant risk difference, with HQ of 3.70 and CR of 4.91E-05. Conversely, Fe (8.93 ± 5.49 μg/m3) and Zn (0.1 ± 0.19 μg/m3) were associated with the lowest non-cancer hazards (HQ 7.08E-04 and 1.05). Additionally, FIFO workers in open environments faced 16.35 % higher risks than those in enclosed spaces, peaking at 19.79 %. overall, FIFO workers have higher health risks than DIDO workers. Improving ventilation, prioritizing indoor work, and Shortening exposure reduce these risks.

Cadmium resistance microbes and TiO2 nanoparticles alleviate cadmium toxicity in wheat

Cadmium toxicity in the soil is an alarming issue, and among innumerable approaches, microbe-facilitated nanoparticle application for alleviation of Cd stress is a well-accepted technique. The present study explored the efficiency of combined TiO2-NPs and Staphylococcus aureus M1 strains for Cd mitigation in wheat plants. Results depicted that Cd stress attenuates the growth attributes while the collective application of NPs and microbes significantly upsurges the growth attributes as contrasted to Cd treatment. Combined TiO2-NPs and microbes application increased the total chlorophyll (12), a (10), b (11), and carotenoids (13%) under Cd (50 mg kg- 1) compared to microbial treatment. MDA (4), H2O2 (3), and EL (5%) were significantly down-regulated with combined TiO2-NPs and microbes application under Cd (50 mg kg- 1) compared to microbial treatment. CAT (17), SOD (7), POD (8), and APX (29%) were increased with combined TiO2-NPs and microbes application under Cd (50 mg kg- 1) comparison to microbial treatment. Cd accumulation in roots (34), shoots (23), and grains (27%) were significantly reduced under Cd (50 mg kg- 1) with combined TiO2-NPs and microbes application, contrary to microbial treatment. Subsequently, combined TiO2-NPs and microbial strains Staphylococcus aureus M1 application is a sustainable solution to boost crop production under Cd stress.

Effects of four different amendments on bioavailable lead in contaminated soils: coupling sequential extraction with in vivo and in vitro assays

Applying amendments to contaminated soil has been considered a successful strategy to control lead (Pb) pollution. In this study, four different types of amendment (calcium hydrogen phosphate, CHP; hydroxyapatite, HA; ordinary Portland cement, OPC; lime, LI) at two treatment levels were used to immobilize Pb in three contaminated soils. The effectiveness of Pb immobilization was assessed by coupling a sequential extraction procedure (fraction) with in vivo mouse model (Pb relative bioavailability, Pb RBA) and in vitro gastrointestinal assays (bioaccessibility). For all four amendments, Pb RBA generally decreased in YNGJ and HNZZ, with a stronger effect at a high treatment level, but less effective in HNJY. In contrast, when in vitro gastrointestinal simulation tests were used, Pb bioaccessibility determined by SBRC and PBET was generally reduced in most cases, especially in soils treated with phosphate amendments. Sequential extraction procedure demonstrated that the addition of 4 amendments generally decreased the proportion of E1 + C2 compared to untreated soils, while increasing R5, O4, or F3. The relationship between Pb fractions and RBA/bioaccessibility indicated that the bioavailable Pb is primarily from the sum of E1 and C2. The finding of this study highlighted reducing E1 + C2 was a primary strategy to further decrease bioavailable Pb in amended soils, and monitoring Pb fractions may provide a concise and alternative method for comprehending the oral bioavailability of Pb to humans.

Assessment of Tamarix smyrnensis for Phytoremediation Capacity of Laterite Mine Spoils

The phytoremediation potential of the halophytic plant, Tamarix smyrnensis (T. smyrnensis), was examined in toxic metal spoils assisted by biochar and irrigation by air nanobubbles. The substrate (spoil) used in the present study was derived from areas close to laterite (Ni-containing ores) mines. The efficiency of biochar addition in two rates (5 t/ha and 20 t/ha) to improve microbial properties and stabilize soil aggregates was also examined. Furthermore, the effect of irrigation with air-nanobubble-supplemented water was evaluated for the remediation of toxic metal spoils. The physiological condition of the plant species was investigated in terms of biomass, height, chlorophyll content, and antioxidant enzymes. The alkali and heavy metal accumulation and their distribution in the plant parts were assessed to explore whether toxic metals could accumulate in the root and further translocate to the aboveground tissues. The growth of T. smyrnensis was not adversely affected by its cultivation in lateritic spoil, and the highest rate of biochar exhibited a beneficial effect on plant growth in terms of weight (aerial and subterranean biomass). The highest biochar application rate led to significant increases in total chlorophyll content, showing a 97.6% increase when biochar is used alone and a 136% increase when combined with nanobubble irrigation. Remarkably, only when combining irrigation with air nanobubbles and low biochar supplementation did the translocation of the metals from soil to the aboveground tissues occur as the translocation factor was estimated to be greater than unity (TF > 1). The bioconcentration factors remained below 1.0 (BCF < 1) across all treatments, demonstrating limited mobilization from soil to plant tissues despite the application of soil amendments. Finally, the application of nanobubbles increased slightly but not substantially the total uptake of metals, which showed a significant decrease compared to the control groups when the lower dosage of biochar was utilized.

Optimization of exogenous CeO2 nanoparticles on Pak choi (Brassica rapa L. var. chinensis) to alleviate arsenic stress

Arsenic (As) is a regulated hazardous substance that persists in the environment, causing issues related to environmental health, agriculture, and food safety. Cerium oxide nanoparticles (CeO2 NPs) are emerging sustainable solutions for alleviating heavy metal stress. However, their effectiveness and optimization for foliar application in reducing As stress, especially in Pak choi, has not been reported yet. Hence, this study aims to examine the effects of foliar application of CeO2 NPs (75,000,000, 150,000,000, and 300,000,000 ng/L) on the growth, nutrient availability, and antioxidant enzymatic activities of Pak choi plants under As stress. The findings showed that foliar application of 75,000,000 ng/L CeO2 NPs significantly increased shoot length (77.32%), root length (80.98%), and number of leaves (80.23%) as compared to control without NPs. The lowest dose of CeO2 NPs (75,000,000 ng/L) increased antioxidant enzyme activities such as peroxidase (86.10%), superoxide dismutase (81.48%), and catalase (52.07%), while significantly reducing malondialdehyde (44.02%), hydrogen peroxide (34.20%), and electrolyte leakage (43.53%). Furthermore, foliar application of 75,000,000 ng/L CeO2 NPs significantly increased the content of zinc (81.02%), copper (56.99%), iron (88.04%), manganese (68.37%), magnesium (76.83%), calcium (61.16%), and potassium (84.91%) in leaves when compared to control without NPs. The same trend was observed for shoot and root nutrient concentrations. Most importantly, 75,000,000 ng/L CeO2 NPs foliar application significantly reduced shoot As (45.11%) and root As (20.89%) concentration compared to control, providing a reassuring indication of their potential to reduce As concentration in plants. Our study's findings are of utmost importance as they indicate that lower concentrations of foliar-applied CeO2 NPs can be more effective in enhancing crop nutrition and reducing heavy metals than higher concentrations. This article is intended to present critical issues of As contamination in agricultural soils, which imposes substantial risks to crop productivity and food security.

Enhanced Phytoextraction Technologies for the Sustainable Remediation of Cadmium-Contaminated Soil Based on Hyperaccumulators-A Review

Heavy metal pollution in soil is a significant challenge around the world, particularly cadmium (Cd) contamination. In situ phytoextraction and remediation technology, particularly focusing on Cd hyperaccumulator plants, has proven to be an effective method for cleaning Cd-contaminated agricultural lands. However, this strategy is often hindered by a long remediation cycle and low efficiency. To address these limitations, assisted phytoextraction has been proposed as a remediation strategy based on the modification of certain traits of plants or the use of different materials to enhance plant growth and increase metal absorption or bioavailability, ultimately aiming to improve the remediation efficiency of Cd hyperaccumulators. To thoroughly understand the progress of Cd hyperaccumulators in remediating Cd-polluted soils, this review article discusses the germplasm resources and assisted phytoextraction strategies for these plants, including microbial, agronomic measure, chelate, nanotechnology, and CO2-assisted phytoextraction, as well as integrated approaches. This review paper critically evaluates and analyzes the numerous approaches and the remediation potential of Cd hyperaccumulators and highlights current challenges and future research directions in this field. The goal is to provide a theoretical framework for the further development and application of Cd pollution remediation technologies in agricultural soils.

Bioenhanced remediation of dibutyl phthalate contaminated black soil by immobilized biochar microbiota

To address the contamination caused by DBP residues prevalent in black soils, this study developed a multifunctional bioremediation material (BHF@DK-P3) using humic acid and iron-modified corn stover biochar in combination with microbiota. The microbiota contained DBP-degrading bacteria (Enterobacterium sp. DNB-S2), phosphorus-solubilizing bacteria (Enterobacter sp. P1) and potassium-solubilizing bacteria (Paenibacillus sp. KT), and formed a good mutualistic symbiosis. In the biochar microenvironment, the microflora had lower DBP biotoxicity responses and more cell membrane formation. The addition of BHF@DK-P3 brought the structure of the DBP-contaminated black soil closer to the optimal three-phase ratio. The microbiota was able to perform their biological functions stably under both DBP stress and acid-base stress conditions. The stability of soil aggregates and the efficiency of N, P, K nutrients were improved, with available phosphorus increasing by 21.45%, available potassium by 12.54% and alkali-hydrolysable nitrogen by 14.74%. The relative abundance of copiotrophic bacterial taxa in the soil increased and the relative abundance of oligotrophic bacterial taxa decreased, providing a good mechanism for the conversion and utilization of soil nutrients. Biochar and microbiota jointly influenced soil carbon and nitrogen metabolism in response to DBP.

Reducing Cd and Pb Accumulation in Potatoes: The Role of Soil Passivators in Contaminated Mining Soils

This work aimed to explore safe techniques for the utilization of farmland surrounding mining areas contaminated with heavy metals-specifically cadmium (Cd) and lead (Pb)-in order to achieve food security in agricultural production. A potato variety (Qingshu 9) with high Cd and Pb accumulation was used as the test crop, and seven treatments were set up: control (CK), special potato fertilizer (T1), humic acid (T2), special potato fertilizer + humic acid (T3), biochar (T4), calcium magnesium phosphate fertilizer (T5), and biochar + calcium magnesium phosphate fertilizer (T6). The remediation effect of the combined application of different passivators on the accumulation of cadmium and lead in potatoes in the contaminated soil of a mining area was studied. The results showed that, compared with CK, all passivator treatments improved the physical and chemical properties of the soil and reduced the available Cd and Pb content in the soil and in different parts of potatoes. The T6 treatment yielded the most significant reduction in the available Cd and Pb content in the soil, the Cd and Pb content in the potato pulp, and the enrichment factor (BCF) and transfer factor (TF) of the potatoes. Compared with T4 and T5, the content of available Cd in the soil decreased by 1.22% and 4.71%, respectively; the soil available Pb content decreased by 3.13% and 3.02%, respectively; the Cd content in the potato pulp decreased by 68.08% and 31.02%, respectively; and the Pb content decreased by 31.03% and 20.00%, respectively. The results showed that the application of biochar combined with calcium magnesium phosphate fertilizer had a better effect in terms of reducing the available Cd and Pb content in the soil and the Cd and Pb content in the potato flesh compared to their individual application. Biochar and calcium magnesium phosphate fertilizer can synergistically increase the content of soil available nutrients and reduce the activity of heavy metals in the soil to prevent the transfer and accumulation of cadmium and lead to potatoes, as well as improve their yield and quality. The results of this study provide technical support for safe potato planting and agricultural soil management.

Biosynthesis of nanoparticles using microorganisms: A focus on endophytic fungi

The concept of this review underscores a significant shift towards sustainable agricultural practices, particularly from the view point of microbial biotechnology and nanotechnology. The global food insecurity that causes increasing ecological imbalances is exacerbating food insecurity, and this has necessitated eco-friendly agricultural innovations. The chemical fertilizers usage aims at boosting crop yields, but with negative environmental impact, thus pushing for alternatives. Microbial biotechnology and nanotechnology fields are gaining traction for their potential in sustainable agriculture. Endophytic fungi promise to synthesize nanoparticles (NPs) that can enhance crop productivity and contribute to ecosystem stability. Leveraging on endophytic fungi could be key to achieving food security goals. Endophytic fungi explore diverse mechanisms in enhancing plant growth and resilience to environmental stresses. The application of endophytic fungi in agricultural settings is profound with notable successes. Hence, adopting interdisciplinary research approaches by combining mycology, nanotechnology, agronomy, and environmental science can meaningfully serve as potential pathways and hurdles for the commercialization of these biotechnologies. Therefore, setting regulatory frameworks for endophytic nanomaterials use in agriculture, by considering their safety and environmental impact assessments will potentially provide future research directions in addressing the current constraints and unlock the potential of endophytic fungi in agriculture.

Biochar addition under straw return reduces carbon dioxide and nitrous oxide emissions in acidic tea field soil

Straw return and biochar application are prevalent agricultural practices that bolster soil health, enhancing crop yields. However, their synergistic effects on carbon dioxide (CO2) and nitrous oxide (N2O) emissions in the acidic tea field soil at different age stages have not been fully elucidated. Herein, tea field soil with 5 and 15 years planting (5a and 15a, respectively) were individually incubated in five distinct indoor experiments: control, soil with urea (N), soil with urea and biochar (N + C), soil with urea and straw (N + S), and soil with urea, biochar, and straw (N + C + S). The results demonstrated that the pH values under 15a (4.1-5.6) were significantly lower than those under 5a (5.8-7.3), and both straw and biochar addition effectively improved soil acidification. Straw or biochar addition alone acted as carbon sources, leading to heightened N2O and CO2 emissions. N + S increased N2O emissions (3.17 and 5.85-fold) and CO2 cumulative emissions (6.43 and 2.33-fold) under 5a and 15a compared with the control. Relative to N treatment, biochar addition alone increased CO2 emission (1.22 and 1.35-fold) under 5a and 15a, and increased N2O emissions by 14.73% under 5a, decreased N2O emissions by 74.65% under 15a. However, the combined application of straw and biochar reduced N2O (49.4%,17.58%) and CO2 emissions (57.83% and 33.60%) due to stimulating biochar adsorption, respectively, compared with N + S treatment under 5a and 15a. Therefore, biochar and straw addition together can effectively increase soil fertilizer and inhibit greenhouse gas emissions, this study provides an insightful way and effective option for improving acid soil and protecting high soil health with a low greenhouse gas emission intensity.

Exploring the traits and possible ecological risks of heavy metals in biochars derived from rice husk and sugar beet pulp

This research investigated the properties and potential environmental hazards associated with biochars derived from rice husk (RH) and sugar beet pulp (SBP), both of which are rich in heavy metals (HMs). The results indicated that the concentration of various HM fractions is significantly affected by the type of feedstock and the pyrolysis temperature. Specifically, the total concentrations of HMs in biochars produced at 600 °C were found to be 10-140% higher than those in the original biomasses, a phenomenon attributed to the precipitation of HMs. Cd was a notable exception, exhibiting a reduction of 3-7% in the resultant biochars when compared to biomass, likely attributable to its volatilization. The results also revealed that the F1 + F2 fraction of HMs were largely transformed into F3 + F4 fraction during combustion, indicating that pyrolysis may reduce the ecotoxicity of HMs present in contaminated biomass. However, the process did not effectively diminish the F1 and F2 fractions of Cr and Cd. Elevated pyrolysis temperature significantly enhanced the reduction of HMs phytoavailability. Specifically, the phytoavailability of HMs in biochars produced at 600 °C exhibited a decrease ranging from 10 to 92% when compared to the original biomass. Conversely, an unexpected rise in the phytoavailable fractions of Cr and Cd was noted in both RH and SBP biochars as the pyrolytic temperature increased, which correspondingly raised the potential ecological risk index (PERI). All materials analyzed exhibited a very high risk level, with PERI values exceeding 800, primarily due to the significant toxicity of Cd. Excluding Cd from consideration, the biomasses and their resultant biochars displayed PERI values ranging from 7 to 13. It is important to acknowledge that pyrolysis may not effectively diminish the environmental toxicity associated with HMs present in contaminated biomass, thereby limiting its safe application.

Rice husk biochar is more effective in blocking the cadmium and lead accumulation in two Brassica vegetables grown on a contaminated field than sugarcane bagasse biochar

Heavy metal-contaminated soil has a great impact on yield reduction of vegetable crops and soil microbial community destruction. Biochar-derived waste biomass is one of the most commonly applied soil conditioners in heavy metal-contaminated soil. Different heavy metal-contaminated soil added with suitable biochars represent an intriguing way of the safe production of crops. This study investigated the effects of two types of biochar [rice husk biochar (RHB) and sugarcane bagasse biochar (SBB)] on Cd and Pb accumulation in Shanghaiqing (SHQ, a variety of Brassica campestris L.) and Fengyou 737 (FY, a variety of Brassica napus), as well as on the soil microbial community, through a field experiment. RHB and SBB were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmet-Teller method. The results showed that RHB and SBB displayed the higher pH, cation exchange capacity and pore properties, and the addition of RHB and SBB enhanced soil pH and rhizosphere microorganisms promoting vegetables yield. RHB treatments were more effective than SBB in reducing upward transfer of Cd and Pb, blocking the accumulation of Cd and Pb in the edible parts of SHQ and FY, and decreasing soil Cd and Pb bioavailability. Additionally, RHB and SBB changed the composition of the rhizosphere soil microbial community. The application of biochar promoted the growth of ecologically beneficial bacteria (Nitrospira, Opitutus, and Gemmatimonas) and fungi (Mortierella and Holtermanniella), whereas reducing the enrichment of plant pathogenic fungi (Alternaria, Stagonosporopsis, Lectera, and Periconia) in rhizosphere soil. Our findings demonstrated that the application of RHB significantly reduces Cd and Pb accumulation in the edible parts by decreasing the soil Cd and Pb bioavailability and altering the rhizosphere microbial community composition in two Brassica vegetables grown on Cd/Pb-contaminated soils. Thus, the application of two biochar, especially RHB is a feasible strategy for the safe production of vegetable crops in Cd/Pb co-contaminated soils.

Nutrient strengthening and lead alleviation in Brassica Napus L. by foliar ZnO and TiO2-NPs modulating antioxidant system, improving photosynthetic efficiency and reducing lead uptake

With the anticipated foliar application of nanoparticles (NPs) as a potential strategy to improve crop production and ameliorate heavy metal toxicity, it is crucial to evaluate the role of NPs in improving the nutrient content of plants under Lead (Pb) stress for achieving higher agriculture productivity to ensure food security. Herein, Brassica napus L. grown under Pb contaminated soil (300 mg/kg) was sprayed with different rates (0, 25, 50, and 100 mg/L) of TiO2 and ZnO-NPs. The plants were evaluated for growth attributes, photosynthetic pigments, leaf exchange attributes, oxidant and antioxidant enzyme activities. The results revealed that 100 mg/L NPs foliar application significantly augmented plant growth, photosynthetic pigments, and leaf gas exchange attributes. Furthermore, 100 mg/L TiO2 and ZnO-NPs application showed a maximum increase in SPAD values (79.1%, 68.9%). NPs foliar application (100 mg/L TiO2 and ZnO-NPs) also substantially reduced malondialdehyde (44.3%, 38.3%), hydrogen peroxide (59.9%, 53.1%), electrolyte leakage (74.8%, 68.3%), and increased peroxidase (93.8%, 89.1%), catalase (91.3%, 84.1%), superoxide dismutase (81.8%, 73.5%) and ascorbate peroxidase (78.5%, 73.7%) thereby reducing Pb accumulation. NPs foliar application (100 mg/L) significantly reduced root Pb (45.7%, 42.3%) and shoot Pb (84.1%, 76.7%) concentration in TiO2 and ZnO-NPs respectively, as compared to control. Importantly, macro and micronutrient analysis showed that foliar application 100 mg/L TiO2 and ZnO-NPs increased shoot zinc (58.4%, 78.7%) iron (79.3%, 89.9%), manganese (62.8%, 68.6%), magnesium (72.1%, 93.7%), calcium (58.2%, 69.9%) and potassium (81.5%, 68.6%) when compared to control without NPs. The same trend was observed for root nutrient concentration. In conclusion, we found that the TiO2 and ZnO-NPs have the greatest efficiency at 100 mg/L concentration to alleviate Pb induced toxicity on growth, photosynthesis, and nutrient content of Brassica napus L. NPs foliar application is a promising strategy to ensure sustainable agriculture and food safety under metal contamination.

Optimized combination of zero-valent iron and oxygen-releasing biochar as cathodes of microbial fuel cells to enhance copper migration in sediment

Membrane-less single-medium sediment microbial fuel cells (single-SMFC) can remove Cu2+ from sediment through electromigration. However, the high mass transfer resistance of the sediment and amount of oxygen at the cathode of the SMFC limit its Cu2+ removal ability. Therefore, this study used an oxygen-releasing bead (ORB) for slow oxygen release to increase oxygen at the SMFC cathode and improve the mass transfer property of the sediment. Resultantly, the copper removal efficiency of SMFC increased significantly. Response surface methodology was used to optimize the nano zero-valent iron (nZVI)-modified biochar as the catalyst to enhance the ability of the modified ORB (ORBm) to remove Cu2+ and slow release of O2. The maximum Cu2+ removal (95 %) and the slowest O2 release rate (0.41 mg O2/d·g ORBm) were obtained when the CaO2 content and ratio of nZVI-modified biochar to unmodified biochar were 0.99 g and 4.95, respectively. When the optimized ORBm was placed at the single-SMFC cathode, the voltage output and copper removal increased by 4.6 and 2.1 times, respectively, compared with the system without ORBm. This shows that the ORBm can improve the migration of Cu2+ in the sediment, providing a promising remediation method for Cu-contaminated sediments.

The Impact of Organic Selenium (IV) on Hypericum perforatum L. under Cadmium Stress and Non-Stress Conditions

The issue of soil contamination by heavy metals is widely acknowledged. Some plants, including medicinal species like St. John's wort (Hypericum perforatum L.), exhibit accumulation traits, allowing them to accumulate elevated levels of metals, e.g., cadmium (Cd), within their cells. Selenium (Se) may increase the tolerance of plants to abiotic stress caused by the presence of heavy metal in the environment. Depending on its form (oxidation state, organic/inorganic), Se influences plant growth, secondary metabolite content, and biotic stress, as well as incorporates into shoots, providing economic and health benefits for consumers. So far, there are no data on the influence of organic Se(IV) on plants. Our study aimed to determine the effect of organic Se(IV) on the growth, active compound levels (anthranoids, polyphenols), and ultrastructure of St. John's wort without and under cadmium stress. The phytochemical analysis and microscopic examination was performed on shoots from different days of St. John's wort in vitro culture on a few variants of Murashige and Skoog medium with Cd (25 and 400 µM) and/or organic Se (IV). Exposure to Se(IV) did not affect hypericins but increased the polyphenol content in the shoots and the biomass. Se(IV) caused an increase in starch grain number in chloroplasts, whereas Cd exposure resulted in the degradation of the chloroplast structure, increased cell vacuolation, as well as swollen mitochondrial cristae. The addition of Se(IV) to these combinations reduced the degree of degradation and growth inhibition and a high content of Se(IV) in plants was observed. Se(IV) had no impact on Cd content at environmental Cd concentrations, but showed an effect at extremely high Cd concentrations. Thus, organic Se(IV) has a beneficial effect on St. John's wort growth, polyphenol content, and incorporation in shoots and prevents Cd toxicity. Media enriched with organic Se(IV) have both economic advantages and health benefits due to a higher plant growth rate and increased concentrations of polyphenols with strong antioxidant properties, relatively enriched with Se. However, organic Se(IV) should be used with caution in polluted areas. In perspective, speciation analysis and molecular study are crucial to understand the fate and effect of Se (IV) on plants.

Heavy metals and trace minerals in commonly available shark species from North East Arabian Sea: A human health risk perspective

Shark is a seafood commodity that is a good source of minerals and accumulates heavy metals and trace elements through biomagnification, which can pose health risk if taken above the permissible limit. A study was conducted on commonly landed eleven shark species (Scoliodon laticaudus, Rhizopriodon oligolinx, Sphyrna lewini (CR), Carcharhinus macloti, Carcharinus limbatus, Carcharhinus amblyrhynchoides, Carcharhinus sorrah, Carcharinus falciformes(VU), Glaucostegus granulatus, Chiloscyllium arabicum, Loxodon macrorhinus) and analyzed for their heavy metal content, Hazard Index, Total Hazard Quotient, Metal Pollution Index, and also calculated the health risk associated with the consumption. Most of the heavy metals and trace minerals were found to be within the acceptable limit. The Targeted Hazard Quotient (THQ) and the Hazard Index (HI) of all the species except two were less than 1 (HI ≤ 1.0). The Metal Pollution Index (MPI) is showing either no impact or very low contamination. An overall study on hazard identification and health risk characterization in terms of heavy metals shows contamination of some heavy metals in sharks, but there is no potential human health risk associated with consumption.

Geochemical fractionation of iron in paper industry and municipal landfill soils: Ecological and health risks insights

Industrial processes and municipal wastes largely contribute to the fluctuations in iron (Fe) content in soils. Fe, when present in unfavorable amount, causes harmful effects on human, flora, and fauna. The present study is an attempt to evaluate the composition of Fe in surface soils from paper mill and municipal landfill sites and assess their potential ecological and human health risks. Geochemical fractionation was conducted to explore the chemical bonding of Fe across different fractions, i.e., water-soluble (F1) to residual (F6). Different contamination factors and pollution indices were evaluated to comprehend Fe contamination extent across the study area. Results indicated the preference for less mobile forms in the paper mill and landfill, with 26.66% and 43.46% of Fe associated with the Fe-Mn oxide bound fraction (F4), and 57.22% and 24.78% in the residual fraction (F6). Maximum mobility factor (MF) of 30.65% was observed in the paper mill, and 80.37% in the landfill. The enrichment factor (EF) varied within the range of 20 < EF < 40, signifying a high level of enrichment in the soil. The individual contamination factor (ICF) ranged from 0 to >6, highlighting low to high contamination. Adults were found to be more vulnerable towards Fe associated health risks compared to children. The Hazard Quotient (HQ) index showed the highest risk potential pathways as dermal contact > ingestion > inhalation. The study offers insights into potential Fe contamination risks in comparable environments, underscoring the crucial role of thorough soil assessments in shaping land use and waste management policies.

Nano-biochar as a potential amendment for metal(loid) remediation: Implications for soil quality improvement and stress alleviation

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.

Comprehensive evaluation of the risk system for heavy metals in the rehabilitated saline-alkali land

A comprehensive assessment of the heavy metal system in the rehabilitated saline-alkali land holds significant importance, as the in-situ remediation process utilizing amendments substantially alters the initial physicochemical properties of the soil, which could lead to the migration or reactivation of previously stabilized heavy metals. In this context, the present study aims to evaluate the heavy metal content and health risk within the improved saline-alkali soil-plant system. Moreover, a comprehensive evaluation based on the TOPSIS-RSR method is carried out to accurately gauge the soil health status. The findings indicate that the modification process has an impact on the concentrations of heavy metals in the soil and crops, causing either an increase or decrease. However, the level of heavy metal pollution in the improved saline-alkali soil and rape remains within safe limits. The results of the migration of heavy metals after amendment application indicated that the migration of heavy metals in the soil was influenced by the properties of the heavy metals, the composition of the amendment, and leaching. Furthermore, the total non-carcinogenic hazard quotients in the soil and rape were within the safe threshold for all populations. The findings provided novel insights into the status and risk assessment of the pollution of improved saline-alkali soil.