Chemosphere最新文献

In agricultural and waste management systems, dairy manure wastewater is often recycled for irrigation. However, a key challenge lies in handling suspended solids (SS) and effectively dewatering sludge. To address this, an innovative polycationic soybean protein-based flocculant (SPI+) was developed and applied to enhance flocculation and sludge dewatering efficiency. The polycationic protein chains of SPI+ were synthesized by grafting 2-(methacryloyloxy)ethyl trimethylammonium chloride (META) monomers onto soybean protein isolate (SPI) chains using an energy-efficient thiol-ene photografting method. This approach achieved a grafting ratio of 85%, endowing the SPI+ with a stable and strong positive zeta-potential (+30 mV) across a range of pH conditions. The SPI + exhibited exceptional flocculation performance, achieving a 96% flocculation efficiency, reducing sludge filtration resistance by 55%, and lowering filter cake moisture content by 10%. The SPI + flocculation and dewatering performance is comparable with synthetic-based commercial flocculant. This remarkable performance of SPI+ is attributed to its ability to effectively neutralize charges, form robust inter-particle bridges, and interact strongly with extracellular polymeric substances (EPS), particularly their protein components, within the sludge matrix. These properties significantly enhance both sludge aggregation and dewaterability. The underlying mechanisms of flocculation and dewatering were further elucidated using confocal imaging, surface morphology analysis of flocs, and quantification of EPS protein and polysaccharide content, providing valuable insights into its functional efficacy.

The goal of this study was to compare the bioaccumulation of the PCB mixture Aroclor 1254 in zebrafish to cardiac and neurologic outcomes. The establishment of effect concentrations (ECs) for cardiac and neurotoxic effects of PCBs in early life stage fish is challenging due to a lack of measured PCB concentrations in test media (e.g., fish tissue), the lack of standard exposure methods, and the propensity of PCBs to adsorb to test glassware and materials resulting in discrepancies in ECs from different studies with similar endpoints. Reporting tissue concentrations in test organisms will allow for standardization across different tests and thus may improve estimations of effect thresholds. Early life stage zebrafish (Danio rerio) are a common environmental toxicological model well represented within the literature, making them ideal for comparisons across multiple studies. Embryos were exposed at 6 h post fertilization (hpf) to aqueous Aroclor 1254 for 96 h with or without renewal in addition to a PCB 126 positive control for cardiotoxicity. PCB concentrations were measured in both exposure solutions and tissue samples. Measured concentrations of Aroclor 1254 in test solutions ranged from 8.7% to 870% of nominal concentrations. Heart rate, pericardial edema, and neurological endpoints (eye tremors) were measured in 102 hpf larvae. Pericardial edema was not present in Aroclor 1254-treated zebrafish but was observed in those exposed to PCB-126. Concentration-dependent bradycardia was observed in zebrafish exposed to Aroclor 1254 and PCB-126. Similarly, a concentration-dependent increase in eye tremor behavior was observed in embryos exposed to Aroclor 1254. Data produced by this study demonstrate novel toxicological effects of Aroclor 1254 and highlight the importance of measuring PCBs in both exposure and receptor media.

Polycyclic aromatic hydrocarbons (PAHs) are a diverse class of chemicals that occur in complex mixtures including parent and substituted PAHs. To understand the hazard posed by complex environmental PAH mixtures, we must first understand the structural drivers of activity and mode of action of individual PAHs. Understanding the toxicity of alkylated PAHs is important as they often occur in higher abundance in environmental matrices and can be more biologically active than their parent compounds. 104 alkylated PAHs were screened from 11 different parent compounds with emphasis on substituted phenanthrenes and their structurally dependent toxicity differences. Using a high-throughput early life stage zebrafish assay, embryos were exposed to concentrations between 0.1 and 100 μM and assessed for morphological and behavioral outcomes. The aryl hydrocarbon receptor (AHR) is often implicated in the toxicity of PAHs and the induction of cytochrome P4501A (cyp1a) is an excellent biomarker of Ahr activation. Embryos were evaluated for cyp1a induction using a fluorescence reporter line. Alkyl and polar phenanthrene derivatives were further assessed for spatial cyp1a expression and Ahr dependence of morphological effects. In the alkyl PAH screen 35 (33.7%) elicited a morphological or behavioral response and of those 23 (65%) also induced cyp1a. 31 (29.8%) of the chemicals only induced cyp1a. Toxicity varied substantially in response to substitution location, the amount of ring substitutions and alkyl chain length. Cyp1a induction varied by parent compound group and was a poor indicator of morphological or behavioral outcomes. Polar phenanthrenes were more biologically active than alkylated phenanthrene derivatives and their toxicity was not dependent upon the Ahr2, Ahr1a or Ahr1b when tested individually, despite cyp1a induction by 50% of polar phenanthrenes. Our results demonstrated that induction of cyp1a did not always correlate with PAH toxicity or Ahr dependence and that the type and location of phenanthrene substitution determined potency.

Heavy metal stress is one of the exorbitant problems faced by plants. Lead (Pb) stress is one of the prevalent stressors in agricultural fields. Nanofertilizers are being currently employed for mitigating heavy metal stress in plants. This study assessed the suitability of zinc oxide nanoparticles (ZnONPs) in ameliorating Pb stress in Brassica juncea (L.) Czern. var. Pusa Jagannath. The tested plants were grown in pots using a randomized block design, placed in herbal garden of Jamia Hamdard and treated with different amounts of Pb and nanozinc viz. control (T0), 250 ppm ZnONPs (T1), 500 ppm ZnONPs (T2), 1000 ppm ZnONPs (T3), 250 μM Pb (T4), 500 μM Pb (T5), and their combinations i.e. 250 μM Pb and 500 ppm ZnONPs (T6), 500 μM Pb and 500 ppm ZnONPs (T7), 250 μM Pb and 1000 ppm ZnONPs (T8) and 500 μM Pb and 1000 ppm ZnONPs (T9). The plants were tested for variations in morpho-physiological parameters, yield traits, biochemical attributes, antioxidant enzyme activity, and cell viability using confocal microscopy. Maximum dose of Pb (500 μM) decreased morphological and yield traits such as leaf area (-51%), shoot length (-17%), root length (-34%), number of seeds per plant (-73%), weight of the seeds (-35%), pod number (-47%), shoot and root fresh weight by -63% and -56%, along with reduction in total chlorophyll (-12%), carotenoid (-38%) content, nitrate reductase (-64%) activity, total soluble protein (-40%), total soluble sugar (-31%) and antioxidant enzymes (SOD, CAT and APX by -14%, -4%, -15% respectively) in comparison to control. Stress markers like proline (195%) and MDA (266%) were elevated in Pb-treated plants.The increased level of total phenol content (89%) and total flavonoid content (478%) was also noted in Pb treated plants which acted as non-enzymatic antioxidant defense. The foliar application of ZnONPs (1000 ppm) was found to be effective in ameliorating Pb induced stress, as depicted by the increases in root length (43%), shoot length (38%), pod number (46%), seed weight (70%), number of seeds per plant (105%), chlorophyll content (41%), carotenoid content (28%), total soluble protein content (20%), and nitrate reductase activity (59%) in comparison to control. When ZnONPs (1000 ppm) was supplemented in Pb (250 μM) treated plants, antioxidant enzymes (SOD and CAT increased by 83%, and APX by 75%) and stress markers such as proline amplified by 387%, and total soluble sugar (61%), with respect to control. ZnONPs also improved the cell viability under Pb stress as revealed by confocal microscopy. In summary, foliar spray of ZnONPs proved effective in mitigating the Pb-induced stress in mustard which could be an effective strategy to alleviate the deleterious effects of Pb stress (500 μM) in mustard plants so as to realize its sustainable production under abiotic stress.

Nanosized cobalt (Co) particles exhibit unique chemical, magnetic, electronic, and catalytic properties. Like nanoscale metallic iron, nanostructured Co and its composite nanostructures also show significant potential for the removal of toxic metal cations from water and wastewater. To explore this potential, composite nanorods (CNRs) of nanosized Co immobilized polyaniline (PANI) nanorods (NRs) matrix (PANI-Co CNRs) were synthesized and effectively applied for the treatment of lead ions (Pb²⁺), serving as a model for heavy metal pollutants in water bodies. Physico-chemical characterization of PANI-Co CNRs revealed that weak ferromagnetic Co nanoparticles (NPs) were effectively deposited onto the surface of the PANI NRs. The enhanced surface properties and superior reactivity of PANI-Co CNRs resulted in greater Pb²⁺ removal efficiency compared to their individual components. The adsorption kinetics were notably rapid, with the time required to reach equilibrium varying between 60 and 150 min for initial concentrations ranging from 50 to 150 mg/L, all at a pH of 5.0. The isotherm data revealed an impressive Pb²⁺ adsorption capacity of 1130 mg/g at 25 °C, as determined using the non-linear Langmuir model. Exothermic and spontaneous Pb²⁺ removal process was deduced from the thermodynamic investigations. Among co-contaminating metal ions, only Cu²⁺ ions significantly affected the Pb²⁺ removal performance of the PANI-Co CNRs, implying its possible applications in decontaminating industrial effluent laden with various metal ions. Mechanistic investigation revealed that the treatment process primarily involves the adsorption and precipitation of Pb²⁺ onto the surface of PANI-Co CNRs, followed by its subsequent reduction to form metallic Pb (Pb⁰).

This study was designed to investigate the dichotomous effects of titanium dioxide nanoparticles (TiO₂NPs) at varying concentrations (0, 50, 100, 1000, and 2500 ppm) on the physiological, biochemical, and antioxidative defense responses of Persian dragonhead plants cultivated in hydroponic conditions. Over 21 days of treatment, an increase in fresh shoot biomass by 26.2% and plant height by 18.2% was observed at exposure to 50 ppm TiO₂NPs. Exposure to 100 ppm NPs negatively affected the biosynthesis of carotenoids, chlorophyll pigments (a, b, and total), and protein content. Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) analysis revealed TiO₂NPs deposition within intercellular spaces and cell walls of root tissues. The physiological stress was prominent in response to 2500 ppm NPs as evidenced by a significant increase in proline and sugar content compared to the control. The enzymatic antioxidative defense was significantly upregulated by the enhanced activity of catalase (CAT) across exposure ranges 100-2500 ppm NPs, ascorbate peroxidase (APX) at 100 and 2500 ppm NPs, and peroxidase (POD) at 100 ppm NPs in plant roots. The antioxidant proficiency was further corroborated by increases in total flavonoids by 30.43% at 2500 ppm, saponins by 253.7%, and iridoids by 22.3% at 100 ppm NPs, relative to control. The results suggest that TiO₂NPs fostered growth promotion at sub-lethal doses, and induced adverse biochemical changes at elevated concentrations, prompting the activation of intrinsic defense mechanisms to enhance plant resilience against NPs stresses. The optimal nano-stimulation performance was observed at 50 ppm TiO₂NPs, which was suggested for the high yield targets, signifying a potential boon for agricultural productivity.

Synthesis of metal-doped biochar have gained prominence due to their adsorption capability for heavy metal(loid)s. In this study, iron-doped biochar (Fe-BC) was fabricated through pyrolysis of waste mushroom substrate (WMS) with red mud (RM). The synthesised Fe-BC was employed as an adsorbent for Pb removal. During pyrolysis of WMS, introducing RM contributed to the enhanced syngas formation, this observation was attributed to the catalytic function of Fe species in RM. The Fe-BCs were made at three different temperatures (500, 600, and 700 °C), and their adsorption capabilities for Pb were evaluated. Among the prepared Fe-BCs, Fe-BC fabricated at 700 °C (Fe-BC-700) demonstrated the highest Pb adsorption performance (243.07 mg g^-1). This performance primarily stemmed from the presence of zero-valent Fe and surface functional groups (-OH) in Fe-BC-700. Pb removal by Fe-BC-700 was dominated by surface precipitation and complexation mechanisms. Therefore, this study highlights a promising approach for producing an effective adsorbent for Pb removal from industrial wastewater by utilizing wastes such as RM and WMS.