Physicochemical properties of nanosized biochar regulated by heat treatment temperature dictates algal responses: From the perspective of fatty acid metabolism

The role of biochar in algal source water treatment: Algal cells integrity and N-Nitrosodimethylamine (NDMA) formation potential

The effects of unmodified and modified biochars (BC) made by tea (TBC), coconut shell (NBC), corn straw (SBC), and orange peel (OBC) on algae removal efficiency and NDMA formation potential (NDMA-FP) in algae-containing water were investigated. The algae removals (12 %-45 %) and NDMA-FP reductions (1 %-20 %) were enhanced by unmodified BC, indicating that the potential application of BC in algae removal and NDMA formation risk control. Cu(Ⅰ/Ⅱ)-modified BC (Cu(Ⅰ/Ⅱ)-BC) significantly promoted algae removal efficiency (up to 80 %) with the most significant physical membrane damage to Microcystis aeruginosa (85-99 %), leading to an increase in NDMA-FP (21 %-31 %). In contrast, Fe(Ⅲ)-modified BC (Fe(Ⅲ)-BC) not only exhibited superior algae removal performance (5 %) with minimal physical damage (membrane damage rate < 15 %), but also provided better control over NDMA-FP (2 %-23 %). Fe(Ⅲ)-BC performed strong adsorption capacity for AOM, with an adsorption efficiency of up to 86 %. NDMA-FP control in algae-containing water by BC depended on its physical damage to cells and AOM adsorption. A positive correlation was observed between membrane damage and AOM adsorption. These findings support optimizing algal removal and NDMA-FP control in drinking water treatment.

Dissolved organic matter mitigates the toxicity of silver nanoparticles to freshwater algae: Effects on oxidative stress and membrane function

The mechanisms underlying the destruction of cell membranes by silver nanoparticles (AgNPs) in the presence of dissolved organic matter (DOM) remain unclear despite extensive studies on the toxicity of AgNPs to the cell membranes of aquatic organisms. This study investigated the impact of dissolved humic acid (DHA) on the toxicity of AgNPs and silver ions (Ag+) to Chlorella vulgaris cell membranes. Specifically, this research examined the alterations in membrane lipid peroxidation, cell membrane permeability, fatty acid (FA) profiles, membrane fluidity, and ultrastructural changes in algal cells resulting from Ag+ and AgNPs, both in the absence and presence of DHA, as well as the potential cytoprotective effect of DHA. The results revealed that DHA promoted C. vulgaris growth, which increased the EC50 of the AgNPs and Ag+ from 180 μg L-1 to 722 μg L-1 and 25 μg L-1 to 193 μg L-1, respectively. DHA addition significantly reduced algal membrane lipid peroxidation caused by Ag+ and AgNPs. Furthermore, DHA increased the permeability and potential of the algal cellular membranes, particularly in the presence of Ag+ and AgNPs. In the absence of DHA, both Ag+ and AgNPs significantly increased the relative content of saturated fatty acids (SFA), while decreasing the unsaturated fatty acids (UFA) levels (p < 0.05). Consequently, both forms of silver decreased the membrane fluidity of algal cells, which increased after adding DHA. Transmission electron microscopy (TEM) showed that the presence of DHA reduced cytoplasmic disintegration and vacuolization during exposure to Ag+ and AgNPs. These results suggest that DHA may regulate the FA composition of algal cell membranes, aiding C. vulgaris in maintaining membrane structure and function under the toxic stress induced by AgNPs and Ag+.

On how titanium dioxide nanoparticles attenuate the toxicity of mercuric chloride to Artemia salina: investigation of fatty acid composition, oxidative stress, and lipid peroxidation

Titanium dioxide nanoparticles (TiO2NPs) as an emerging pollutant in aquatic environments can interact with metals reducing or enhancing their toxicity in these environments. This study examined and compared the toxic effects of mercury ions (Hg2+ ions) on immobilization percentage, fatty acid profile, and oxidative stress of Artemia salina nauplii, individually (Hg) and simultaneously in the presence of 0.10 mg.L-1 (Hg-0.1TiO2NPs) and 1.00 mg.L-1 TiO2NPs (Hg-1TiO2NPs). The interaction between Hg2+ ions and TiO2NPs was evaluated using DLS and AAS-VGA. Simultaneous exposures exhibited an unexpected dual effect on A. salina nauplii. A synergistic effect was observed in Hg-0.1TiO2NPs, while increasing the TiO2NPs concentration in Hg-1TiO2NPs prevented the synergy of the mixture compounds offering an antagonistic effect on nauplii. This dual effect was assigned to a greater number of available active sites and agglomeration of TiO2NPs at higher concentrations. Oxidative stress and lipid peroxidation induced by Hg were diminished in Hg-1TiO2NPs in line with the immobilization results. In Hg, total amounts of saturated fatty acids (∑SFA) increased while total monounsaturated (∑MUFA) and total polyunsaturated (∑PUFA) ones decreased compared with the control. However, they showed no significant change considering the control in Hg-1TiO2NPs, again confirming the antagonistic effect on nauplii. The unsaturated to saturated fatty acids ratio decreased in both Hg and Hg-1TiO2NPs compared with the control, however, this reduction in Hg-1TiO2NPs was lower than in Hg. The present results emphasized getting a more comprehensive understanding of how TiO2NPs impact the bioavailability and toxicity of co-contaminants through their combined effects and interactions.

Advances in sustainable production and applications of nano-biochar

Biochar is a carbonaceous material that can be amplified into nano-biochar (N-BC) using different physicochemical techniques. Contrary to bulk biochar, nano-biochar, and have better physicochemical characteristics, including a large specific surface area, pore properties, distinctive nanostructure, and high catalytic activity. The spotlight of this review is to contribute up-to-date information on the scaling up of biochar into nano-biochar through various sustainable techniques. This review paper is a compilation of research on nano-biochar from biochar including preparation, distinctive characteristics, and intended applications in the environmental and agricultural sectors, along with some other cutting-edge applications, which are all covered in detail in this review paper and also provides the knowledge gap that will be useful for future investigation and development.

Repeated release of cerium oxide nanoparticles altered algal responses: Growth, photosynthesis, and photosynthetic gene expression

The expanding production of engineered nanomaterials (ENMs) can eventually cause their increased release into and presence in aquatic ecosystems, potentially threatening the health of aquatic organisms and the stability of the ecological environment. Generally, ENMs are repeatedly released into real-world aquatic environments in relatively low concentrations, potentially affecting photosynthesis in primary producers such as algae. However, knowledge regarding the effects of repeated exposure to ENMs on algal photosynthesis is still lacking. Herein, the physiological responses of the freshwater algae Chlorella vulgaris following single and repeated exposures to cerium oxide nanoparticles (CeO2 NPs) were investigated at 10 mg/L, with a focus on photosynthesis. The results showed that repeated exposures triggered increased photosynthetic pigment contents, oxidative stress levels, decreased photosynthetic performance, and lower biomass in C. vulgaris compared to a single exposure. Photosynthesis-related genes (i.e., petA, petB, psaA, atpB, and rbcL) were found to be upregulated following repeated exposures. Particularly for petB, repeated rather than single exposure treatment significantly upregulated its expression levels by 2.92-10.24-fold compared to unexposed controls. Furthermore, increased exposure times could aggravate the interaction between CeO2 NPs and algae, elevating 8.13%, 12.13%, and 20.51% Ce distribution on the algal cell surface or intracellularly, compared to a single exposure. This study is the first to investigate the effects of ENM exposure times on algal photosynthesis, providing new insights into the assessment of the risks these materials pose to real-world aquatic environments.

Biochar-enhanced bioremediation of eutrophic waters impacted by algal blooms

The permanent problem of formation of algal blooms in water polluted with nitrogen and phosphorus is one of the formidable environmental problems. Biochar has the potential to solve the issues related to eutrophication due to its special structure and ability to absorb the nutrients. Biochar's exceptional nutrient absorption capacity allows it to absorb excess nutrients, causing the algae to use fewer nutrients. This review deals with effective performance of biochar in reducing the effects caused by algal blooms and improving the environmental conditions. Besides, an analysis of the issues involved addresses the origins and consequences of nitrogen and phosphorus pollution, and the formation of algal blooms is also reviewed. It then delves deeply into biochar, explaining its properties, production methods, and their uses in environmental contexts. The review emphasizes that biochar can be effective in dealing with many challenges associated with environments affected by algal blooms, specifically focusing on the positive effects of biochar and algae to examine their roles in controlling algae growth. Finally, the review emphasizes new achievements and innovative ideas to foster sustainable aquatic ecosystems. The discussions emphasize the central role of biochar in managing nutrient-rich waters and algal blooms.

Negative impacts of perishable waste biochar to Escherichia coli and exploring potential damage factors

Agricultural application of pyrolysis‑carbonized perishable wastes can target reduction treatment and resource utilization of the wastes. However, potential undesirable impact has rarely been assessed. In this study, the adverse effect of perishable waste biochars (PWB) from different pyrolysis temperatures on Escherichia coli (E. coli) was explored and the potential risk factors were further analyzed. The results showed that PWBs pyrolyzed at 350, 500, and 650 °C inhibited the growth of E. coli, and PWB pyrolyzed at 500 °C showed the most inhibition. The exposure to PWB damaged the antioxidative system, as revealed by the concentration-dependent increasing of intracellular ROS. In addition, the toxicity at the gene level in terms of cell division and growth inhibition, the damage of cell membrane, antioxidant system disturbance, and DNA damage occurred, resulting in loss of the cell rules of morphology and eventual death. According to our results, the inhibitory effect on the growth of E. coli was mainly caused by PWB solids, accounting for >70 %. The membrane disruption and oxidative damage of E. coli by PWB were possibly induced by the direct physical interaction between cell and char particles. The growth of E. coli can be partly influenced by PWB extraction solutions that varied between PWB types, due to the differences in pH, released DOC and the production of extracellular ∙OH. The exploration of these potential hazards could provide new insights into the fate and toxicity of PWB in the environment and help guide the safe and sustainable applications for PWB.

Oxidation effects on Microcystis aeruginosa inactivation through various reactive oxygen species: Degradation efficiency, mechanisms, and physiological properties

The study investigated the inactivation of Microcystis aeruginosa using a combined approach involving thermally activated peroxyacetic acid (Heat/PAA) and thermally activated persulfate (Heat/PDS). The Heat/PDS algal inactivation process conforms to first-order reaction kinetics. Both hydroxyl radical (•OH) and sulfate radical (SO4-•) significantly impact the disruption of cell integrity, with SO4-• assuming a predominant role. PAA appears to activate organic radicals (RO•), hydroxyl (•OH), and a minimal amount of singlet oxygen (1O2). A thorough analysis underscores persulfate's superior ability to disrupt algal cell membranes. Additionally, SO4-• can convert small-molecule proteins into aromatic hydrocarbons, accelerating cell lysis. PAA can accelerate cell death by diffusing into the cell membrane and triggering advanced oxidative reactions within the cell. This study validates the effectiveness of the thermally activated persulfate process and the thermally activated peroxyacetic acid as strategies for algae inactivation.

Dual valorization of coastal biowastes for tetracycline remediation and biomethane production: A composite assisted anaerobic digestion

Harnessing coastal biowaste for dual valorization in water treatment and biofuel production holds paramount importance for sustainability and resource challenges. This study investigated the potential of engineered composite (CABC) derived from coastal biowaste-based materials for tetracycline (TC) removal and biomethane production. High-yield calcium carbonate (CaCO3; 95.65%; bivalve shells) and biochar (GA-BC; 41.50%; green macroalgae) were produced and used as precursors for CABC. The characterization results revealed presence of β-CaCO3 and ν2-CO3 aragonite in CaCO3, and composite homogeneity was achieved. The CABC exhibited a maximum TC sorption capacity of 342.26 mg/g via synergistic sorption mechanisms (i.e., surface/pore filling, electrostatic attraction, calcium ion exchange, and chelation). Supplementation of anaerobic digestion process with GA-BC, CaCO3, and CABC was investigated via three consecutive cycles. Biochemical methane potential of glucose as a sole substrate was increased from 157.50 to 217.00, 187.00, and 259.00 mL-CH4, while dual substrate (glucose+TC) treatment was increased from 94.5 to 146.5, 129.0, and 153.00 mL-CH4 for GA-BC, CaCO3, and CABC, respectively. Moreover, system stability and TC removal were increased with the addition of GA-BC (40.90%), CaCO3 (16.30%), and CABC (53.70%). Therefore, this study exemplifies the circular bioeconomy approach, demonstrating the sustainable use of biowaste-derived composite for water treatment and biofuel production.

Biochar and nano biochar: Enhancing salt resilience in plants and soil while mitigating greenhouse gas emissions: A comprehensive review

Salinity stress poses a significant challenge to agriculture, impacting soil health, plant growth and contributing to greenhouse gas (GHG) emissions. In response to these intertwined challenges, the use of biochar and its nanoscale counterpart, nano-biochar, has gained increasing attention. This comprehensive review explores the heterogeneous role of biochar and nano-biochar in enhancing salt resilience in plants and soil while concurrently mitigating GHG emissions. The review discusses the effects of these amendments on soil physicochemical properties, improved water and nutrient uptake, reduced oxidative damage, enhanced growth and the alternation of soil microbial communities, enhance soil fertility and resilience. Furthermore, it examines their impact on plant growth, ion homeostasis, osmotic adjustment and plant stress tolerance, promoting plant development under salinity stress conditions. Emphasis is placed on the potential of biochar and nano-biochar to influence soil microbial activities, leading to altered emissions of GHG emissions, particularly nitrous oxide(N2O) and methane(CH4), contributing to climate change mitigation. The comprehensive synthesis of current research findings in this review provides insights into the multifunctional applications of biochar and nano-biochar, highlighting their potential to address salinity stress in agriculture and their role in sustainable soil and environmental management. Moreover, it identifies areas for further investigation, aiming to enhance our understanding of the intricate interplay between biochar, nano-biochar, soil, plants, and greenhouse gas emissions.

Combined transcriptomic and metabolomic analyses of temperature response of microalgae using waste activated sludge extracts for promising biodiesel production

Waste activated sludge (WAS) as one of the major pollutants with a significant annual production, has garnered significant attention regarding its treatment and utilization. If improperly discharged, it not only caused environmental pollution but also led to the wastage of valuable resources. In this study, the microalgae growth and lipid accumulation using waste activated sludge extracts (WASE) under different temperature conditions were investigated. The highest lipid content (59.13%) and lipid productivity (80.41 mg L-1 d-1) were obtained at cultivation temperatures of 10 and 25 °C, respectively. It was found that microalgae can effectively utilize TN/TP/NH4+-N and other nutrients of WASE. The highest utilization rates of TP, TN and NH4+-N were achieved at a cultivation temperature of 10 °C, reaching 84.97, 77.49 and 92.32%, respectively. The algal fatty acids had carbon chains predominantly ranging from C14 to C18, making them suitable for biodiesel production. Additionally, a comprehensive analysis of transcriptomics and metabolomics revealed up-regulation of genes associated with triglyceride assembly, the antioxidant system of algal cells, and cellular autophagy, as well as the accumulation of metabolites related to the tricarboxylic acid (TCA) cycle and lipids. This study offers novel insights into the microscopic mechanisms of microalgae culture using WASE and approaches for the resource utilization of sludge.

Inactivation of harmful cyanobacteria Microcystis aeruginosa by Cu2+ doped corn stalk biochar treated with different pyrolysis temperatures

In this study, biochars (BCs) derived from corn stalk treated at various pyrolysis temperatures (350-950 °C) were prepared and then loaded with Cu2+ to form highly efficient algaecide, i.e. Cu2+-doped BC composites (Cu-BCs). The results showed BCs pyrolyzed at higher temperatures suppressed the growth of Microcystis aeruginosa in the order of BC550 ≫ BC750 > BC950, while BC350 accelerated cell growth due to the release of inorganic nutrients. The difference could be attributed to the physicochemical characteristics, including specific surface area, adsorption capacity of nutrients and the presence of particularly persistent free radicals. Furthermore, Cu-BCs exhibited the improved inactivation performance, but the 72 h growth inhibition rates and reaction activities of Cu-BCs were still influenced by the Cu2+ loading ratio and pyrolysis temperature. These results, reported for the first time, demonstrated the algae inactivation efficiency of pristine BCs, and Cu-BCs were principally manipulated by the biochar pyrolysis temperature.

Developmental toxicity of perfluorohexane sulfonate at human relevant dose during pregnancy via disruption in placental lipid homeostasis

Perfluorohexyl sulfonate (PFHxS) is the third most abundant per- and polyfluoroalkyl substances and its developmental toxicity remains very poorly understood. Here, pregnant mice exposed to PFHxS at human relevant dose showed increased fetal death incidence in the high-dose PFHxS-H group (P < 0.01). Body distribution analyses suggested that PFHxS crossed the placental barrier reaching the fetus in a dose-dependent manner. Histopathological data demonstrated impairment in the placenta with reduced blood sinus volume, placental labyrinth area as well as thickness of labyrinthine layer. Further lipidomic and transcriptomic data together showed that PFHxS exposure caused significant disruption in placental lipid homeostasis, including total lipid accumulation in the placenta, and dysregulation in phospholipid and glycerol lipid metabolism. Gene expression analyses uncovered elevation in key placental fatty acid transporters including fabp2, whereas protein expression showed transporter specific disruptions following exposure. Together, gestational exposure to human relevant level of PFHxS may increase the incidence of fetal deaths and caused placental dysplasia via disruption in lipid metabolism homeostasis. These findings raise the concern regarding the highly prevalent and persistent chemical towards early sensitive developing stages and provide basis for further understanding of its effects on lipid metabolism and underlying mechanisms.