Phytotoxicity Assessment Research Articles

Holistic approach to waste mobil oil bioremediation: Valorizing waste through biosurfactant production for soil restoration

The combustion of mobil oil leads to the emission of toxic compounds in the environment. In this study, the aromatic and aliphatic hydrocarbon fractions present in a waste mobil oil collected from automobile market were comprehensively identified and their toxicity was evaluated using wheat grain. Lysinibacillus sphaericus strain IITR51 isolated and characterized previously could degrade 30–80% of both aliphatic and aromatic hydrocarbons in liquid culture. Interestingly, the strain IITR51 produced 627 mg/L of rhamnolipid biosurfactant by utilizing 3% (v/v) of waste mobil oil in the presence of 1.5% glycerol as additional carbon source. In a soil microcosm study by employing strain IITR51, 50–86% of 3–6 ring aromatic hydrocarbons and 63–98% of aliphatic hydrocarbons (C8 to C22) were degraded. Addition of 60 μg/mL rhamnolipid biosurfactant enhanced the degradation of both aliphatic and aromatic hydrocarbons from 76.88% to 61.21%–94.11% and 78.27% respectively. The degradation of mobil oil components improved the soil physico-chemical properties and increased soil fertility to 64% as evident by the phytotoxicity assessments. The findings indicate that strain IITR51 with degradation capability coupled with biosurfactant production could be a candidate for restoring hydrocarbon contaminated soils.

Assessment of phytotoxicity of potable water treatment plant sludge-bound compost pellets on seed germination of radish (Raphanus sativus L.)

Maintenance of compost pellet stability highly depends on the binding materials used. Potable water treatment plant sludge (WTPS) has the potential to be used as a binding material due to its high content of clay, organic matter, and nutrients. Compost and WTPS may contain heavy metals, toxic compounds, salts, and growth inhibitors and they may be phytotoxic to the plants. The present study aimed to assess the phytotoxicity of different pelleted compost using a seed germination bioassay of Raphanus sativus L. Pellet aqueous extracts (PAEs) were prepared from four types of compost pellets (T1: commercial compost pellet, T2: commercial integrated pellet, T3: WTPS-bound compost pellet, T4: WTPS-bound integrated pellet). The dilution sequence of PAEs at 50% and 100% concentrations were tested for seed germination in Petri dishes in a randomized design with three replicates. pH, EC, and selected heavy metal concentrations (Al3+, Zn2+, Cu2+, and Cr6+) were determined in PAEs. Relative Seed Germination % (RSG%), Relative Radicle Growth % (RRG%), and Germination Index (GI) were calculated for all the treatments after 72 hours. RSG%, RRG%, and GI showed negative correlation with EC. PAEs of T2 showed high phytotoxicity, while T4 showed less phytotoxicity at the 100% concentration level, whereas other treatments did not show any signs of phytotoxicity. All the PAEs at 50% concentration level were free from phytotoxicity. Hence, 10% WTPS on a w/w basis can be used as a binding material in pelletizing loose compost.

Enhanced removal of dibutyl phthalate in a laccase-mediator system: Optimized process parameters, kinetics, and environmental impact

The persistence and recalcitrance of endocrine-disrupting chemicals (EDCs) in the environment have raised momentous concerns due to their carcinogenic, teratogenic, genotoxic, and cytotoxic effects on humans, animals, and plants. Unarguably, dibutyl phthalate (DBP) is one of the most ubiquitous EDCs because of its bioavailability in water, soil, and atmosphere. This study aims to investigate the efficiency of Agaricus bisporus laccase in the degradation of dibutyl phthalate (DBP) in laccase-mediator system. Here, enhanced removal efficiency was recorded during DBP degradation in laccase-mediator systems than in reaction medium containing laccase only. About 98.85% of 30 mg L−1 DBP was efficiently removed in a medium containing 1.3 U mL−1, 0.045 mM Syringaldehyde (SYR) at incubation temperature 30 aC and pH 5 within 24 h. This finding was further corroborated by the synergistic interplay of the optimal parameters in the laccase-SYR system done using response surface methodology (Box-Behnken Design). Furthermore, the addition of 1.5 mM of metal ions in the laccase-SYR system further promoted the enhanced removal of DBP in the following order: Cr3+> Pb2+> Ca2+> Al3+>Zn2+ > Cu2+. A significant decrease in DBP degradation was observed at higher concentrations of metal ions above 1.5 mM due to the inhibition of laccase active sites. The coefficient of correlation (R2 = 0.9885) recorded in the Lineweaver bulk plot affirmed that the removal efficiencies are highly dependent on DBP concentration in the laccase-SYR system. The Gas-Chromatography Mass Spectrometry (GC-MS) analyses affirmed that the ortho-cleavage due to hydrolysis of DBP in the reaction system led to the formation of two metabolic degradation products (MBP and PA). The phytotoxicity assessment affirmed the detoxified status of DBP after treatment with significant improvement (90 and 91%) in the growth of Lens culinaris and Sorghum bicolor. This is the first report on DBP degradation in the laccase-SYR reaction system, underscoring the unique, eco-friendly, economical, and promising alternative to known conventional methods.

Remediation of bensulfuron methyl polluted water and soil by Fe2O3/Fe3O4@C activating peroxymonosulfate: Chloride enhancement effect and phytotoxicity assessment

Remediation of bensulfuron methyl polluted water and soil by Fe2O3/Fe3O4@C activating peroxymonosulfate: Chloride enhancement effect and phytotoxicity assessment

Arsenic resistance and accumulation by two bacteria isolated from Ratanpur Village of Varanasi District, Uttar Pradesh

Arsenic-resistant bacteria were isolated from Ratanpur Village of Varanasi District, Uttar Pradesh, by enrichment technique. The isolates, Proteus alimentorum strain TY6 and Pseudomonas aeruginosa strain K7Pb, showed high resistance to As(V) with minimum inhibitory concentration of 610 mM and 350 mM, respectively, and for As(III), 10 mM and 8 mM, respectively. TY6 could remove 96 ± 0.816 % As(V) and 66 ± 0.471 % As(III), whereas K7Pb could remove 98 ± 0.942 % As(V) and 78 ± 1.247 % As(III). Biotransformation ability was determined using AgNO3 and KMnO4 tests. PCR amplification showed the presence of aio, arr, arx and ars genes. Strains also showed resistance against other heavy metals such as Cd, Cr, Co, Pb, Hg, and Ni. Phytotoxicity assessment on chickpea and Vigna radiata (mung bean) revealed that the arsenic-contaminated water treated with the isolates can be used for irrigation purposes. It is also the first report of arsenic remediation by Proteus alimentorum bacteria (to the best of the authors' knowledge).

Phytotoxic and Insecticidal Activity of Industrial Hemp (Cannabis sativa L.) Extracts against Plodia interpunctella Hübner—A Potential Sunflower Grain Protectant

The biological activity (contact and contact-digestive toxicity, repellent and fumigant effects, effect on the insect’s development and life cycle parameters) of industrial hemp (Cannabis sativa L.) ethanolic extract was assessed against Plodia interpunctella, the most destructive storage pest of sunflower. Additionally, the study aimed to examine the phytotoxic activity of the extract in order to assess its potential as a sunflower grain protectant. Phytotoxicity assessment was based on the effect on germination energy and seed germination and the activity of antioxidative enzymes, enzymes of the polyphenolic metabolism, and the intensity of lipid peroxidation in sunflower seedlings. The antioxidant capacity and content of phenolic compounds (total phenolics and total tannins) were also measured in seedlings. In the experiments, 70% ethanolic extract of dried flowering buds of industrial hemp (variety Helena) was applied at 0.5%, 1.0% and 2.0% concentrations directly on sunflower seeds. Ethanol solution (70%) was the control. The hemp extract (1% and 2%) revealed medium repellence for P. interpunctella larvae (L3–4) while at 2% concentration it caused 42.5% larval mortality after 72 h. Moreover, the insect’s development was prolonged and fecundity significantly reduced in hemp treatments. The extract did not exhibit fumigant activity. Germination energy and germination of sunflower seeds were stimulated in treatment with 2% hemp extract, while most biochemical parameters of the seedlings were not significantly affected by the hemp extract.

Revealing the metabolomics and biometrics underlying phytotoxicity mechanisms for polystyrene nanoplastics and dibutyl phthalate in dandelion (Taraxacum officinale)

Micro/nanoplastics (M/NPs) and phthalates (PAEs) are emerging pollutants. Polystyrene (PS) MPs and dibutyl phthalate (DBP) are typical MPs and PAEs in the environment. However, how dandelion plants respond to the combined contamination of MPs and PAEs remains unclear. In this study, we evaluated the individual and combined effects of PS NPs (10 mg L−1) and DBP (50 mg L−1) on dandelion (Taraxacum officinale) seedlings. The results showed that compared to control and individual-treated plants, coexposure to PS NPs and DBP significantly affected plant growth, induced oxidative stress, and altered enzymatic and nonenzymatic antioxidant levels of dandelion. Similarly, photosynthetic attributes and chlorophyll fluorescence kinetic parameters were significantly affected by coexposure. Scanning electron microscopy (SEM) results showed that PS particles had accumulated in the root cortex of the dandelion. Metabolic analysis of dandelion showed that single and combined exposures caused the plant's metabolic pathways to be profoundly reprogrammed. As a consequence, the synthesis and energy metabolism of carbohydrates, amino acids, and organic acids were affected because galactose metabolism, the citric acid cycle, and alanine, aspartic acid and glutamic acid metabolism pathways were significantly altered. These results provide a new perspective on the phytotoxicity and environmental risk assessment of MPs and PAEs in individual or coexposures.

The synergetic action of FeVO4 and h-BN for decontamination of industrial wastewater pollutants and the assessment of phytotoxicity

The research's primary objective is to successfully utilize the sol-gel method to synthesize FeVO4/h-BN nanocomposite with a smaller bandgap than h-BN (hexagonal boron nitride). The nanocomposite was examined using various techniques, including XRD, SEM, TEM, UV–Vis, PL, FT-IR, XPS, EIS, and Mott-Schottky analysis, to properly evaluate its structure, optical activity, vibrational properties, chemical compositions, and electrochemical studies. The FeVO4/h-BN binary nanocomposite shifts the band gap of synthesized h-BN from 5.8 eV to 2.01 eV. The composite's morphology made it abundantly clear that the spherical FeVO4 was anchored together in a sheet of h-BN. A phytotoxicity test was conducted after the photocatalytic degradation of industrial wastewater from textiles. Correspondingly, interpretation of the photocatalytic process showed the FeVO4/h-BN nanocatalyst degraded against industrial wastewater (IWW), Congo red (CR), and Methylene blue (MB) dye by up to 92.5%, 86.4%, and 96.4%, and antibiotics like metronidazole (MNZ) and cephalexin (CPX) up to 95.8% and 83.5% respectively, within 60 min under visible light. Numerous Physiochemical parameters intensity in the degraded IWW had greatly reduced, denoting lessened toxicity. To understand the photocatalytic degradation mechanism, trapping experiments with different scavengers were pursued. The scavenger study's evidence suggests that holes (h+) deserve greater suspicion for the degradation process. The material's potential for recycling was examined, and it was found to have significant potential insight into recycling prospects. In actual textile wastewater, the FeVO4/h-BN degrading tactic proved itself to be an efficient as well as economical choice.

Comparative stress response assessment of PFOS and its alternatives, F-53B and OBS, in wheat: An insight of toxic mechanisms and relative magnitudes

Emerging alternatives to perfluorooctane sulfonate (PFOS), including 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) and p-perfluorous nonenoxybenzene sulfonate (OBS), have been widely detected in the real environment as PFOS restriction. However, the toxicity in plants and the underlying mechanism of F-53B and OBS remain scarce, especially compared to PFOS. PFOS and their emerging alternatives pose significant potential risks to food, especially for crops, safety and human health with the great convenience of high chemical stability. Germination toxicity, oxidative stress biomarkers, and metabolomics were used to compare the relative magnitudes of toxicity of PFOS and its alternatives in wheat (Triticum aestivum L.). PFOS, F-53B, and OBS inhibited wheat germination compared to the control group, with germination inhibition rates of 45.6%, 53.5%, and 64.3% at 400 μM PFOS, F-53B, and OBS exposure, respectively. Moreover, oxidative stress biomarker changes were observed in PFOS, F-53B, and OBS, with OBS being more pronounced. The chlorophyll concentrations in wheat shoots increased, and the anthocyanin concentration decreased along with the increased exposure concentration. Superoxide dismutase (SOD) activity increased in wheat root but decreased in the shoot. Peroxidase (POD) activity and malondialdehyde (MDA) concentration increased, whereas catalase (CAT) activity decreased. Regarding metabolomics, PFOS, F-53B, and OBS exposure (10 μM) significantly altered 85, 133, and 134 metabolites, respectively. According to KEGG enrichment analysis, F-53B specifically affects lipid metabolism, whereas OBS causes an imbalance in amino acid and carbohydrate metabolism. These findings suggested that PFOS, F-53B, and OBS have distinct toxic mechanisms. Thus, our results indicated that the relative size of the toxicity in wheat is as follows: OBS > F-53B > PFOS, and this finding provides a new reference basis for the phytotoxicity assessment of F-53B and OBS.

Activated peroxymonosulfate with co-doped copper oxide nanomaterials for highly efficient degradation of organic pollutants

In the current work, a series of novel cobalt-doped copper oxide nanomaterials (Co-CuOT, subscript ‘T’ means ‘calcination temperature’) were prepared through the chemical reduction method following by calcination. Their reactivities were screened for the degradation of various organic pollutants including p-chlorophenol (4-CP) in the presence of peroxymonosulfate (PMS) as oxidant precursor. These as-prepared Co-CuOT nanomaterials possess exposed active surface as well as positive Cu-Co synergistic effect, and further enhances the 4-CP degradation by activating PMS. The Co-CuO300/PMS exhibited the best ability toward the 4-CP degradation, achieving 100% degradation of 4-CP and excess 80 % removal efficiency of total organic carbon (TOC) within 10 min at room temperature. The Co-CuO300 sample is two to thirteen folds dominative than the other samples (Co-CuO400, Co-CuO500, CuOcds and CoB), respectively. Attractive reactivities of Co-CuOT nano-catalysts are attributed to the amounts of oxygen vacancies, copper-cobalt synergy, and increased generation of reactive radicals. Based on quenching experiment and electron paramagnetic resonance (EPR) analysis, the degradation of 4-CP in the PMS/Co-CuO300 system was found to mainly depend on the species of free radicals, e. g., hydroxyl radical (•OH), sulfate radical (SO4•−). Meanwhile, Co-CuO300 displayed better recyclability and anti-interference ability. The reactivated catalyst after the fifth run still showed high degradation activity, even completely eliminating 4-CP. Substrate expense indicate that the Co-CuO300/PMS system exhibited high efficiency in the degradation of various types of organic pollutants including phenolic compounds and antibiotics under mild conditions. Phytotoxicity assessment showed that mung beans grew well in both the deionized water and the filtered degradation solution, suggesting highly remarkable elimination of 4-CP in Co-CuO300/PMS system. Overall, Co-CuOT nanocomposites hold great promise for large-scale practical application in the activation of PMS and subsequent degradation of organic pollutants.

Comparative characterisation and phytotoxicity assessment of biochar and hydrochar derived from municipal wastewater microalgae biomass

Microalgae, originating from a tertiary treatment of municipal wastewater, is considered a sustainable feedstock for producing biochar and hydrochar, offering great potential for agricultural use due to nutrient content and carbon storage ability. However, there are risks related to contamination and these need to be carefully assessed to ensure safe use of material from wastewater microalgae. Therefore, this study compared the properties and phototoxicity of biochar and hydrochar produced via pyrolysis and hydrothermal carbonisation (HTC) of microalgae under different temperatures and residence times. While biochar promoted germination and seedling growth by up to 11.0% and 70.0%, respectively, raw hydrochar showed strong phytotoxicity, due to the high content of volatile matter. Two post-treatments, dichloromethane (DCM) washing and further pyrolysis, proved to be effective methods for mitigating phytotoxicity of hydrochar. Additionally, biochar had 35.8–38.6% fixed carbon, resulting in higher carbon sequestration potential compared to hydrochar.

Fabrication of biochar from jarul (Lagerstroemia speciosa) seed hull for ultrasound aided sequestration of ofloxacin from water: Phytotoxic assessments and cost analysis

Water pollution by pharmaceutical pollutants such as antibiotics are rising day by day and antibiotics are considered as emerging contaminants because of their eventual threats for both human health and aquatic ecology. Recently waste biomass derived biochar has drawn a lot of attention, especially as adsorbents, for antibiotics contaminated wastewater sequestration because of their high sorption capability, higher surface area, and microporosity. In this study, waste biomass (Lagerstroemia speciosa) seed coats were used to produce biochar (CLSHB) through a pyrolysis progression followed by chemical activation with NaOH for the effective removal of an antibiotic drug ofloxacin (OFL) from water. The surface area, and pore volume of CLSHB were assessed to be 82.192 m2/g, and 0.189 cm3/g, consecutively. The optimum removal percentage of OFL was obtained to be 91.43 % at solution pH 5.0, adsorbent dose of 1.0 g/L, OFL concentration of 20 mg/L, and sonication time of 90 min. The OFL adsorption data were well-fitted by the Langmuir isotherm model with uptake capacity of 34.60 mg/g, which depicts the monolayer adsorption of OFL onto the CLSHB surface. OFL adsorption kinetics results fit to the pseudo-second-order model, indicating that chemical sorption might be the main mechanism by which the pharmaceutical adhered to the CLSHB surface. The phytotoxicity assessment demonstrated that the treated OFL solution obtained in this process was deemed suitable for seed germination and the total synthesis cost of CLSHB was found to be only 8.7 $/kg. The OFL elimination efficacy with CLSHB decreases from 91.43 % to 73.26 % after fifth cycle of consecutive use, demonstrating the strong stability and reusability of CLSHB.

Interaction of BiVO4 anchored 2D hexagonal boron nitride nanocomposite for photocatalytic water pollutants degradation and phytotoxicity assessment

Water pollution caused by chemical contaminants has become an ongoing issue for society, industry, and government. In comparison to traditional treatment approaches, nanotechnology is currently an ideal medium for microbial and organic pollutant removal from water. This study aims to create BiVO4/h-BN nanocomposites for effective photocatalytic degradation. The nanocomposite was studied using XRD, UV-Vis, FTIR, Zeta potential, SEM, TEM, BET, XPS, PL, EIS, and M-S plot analysis. The morphological analysis showed that the formed boron nitride is a hexagonal structure on which BiVO4 is anchored. The band gap of prepared h-BN is 5.8 eV, whereas the band gap of the binary BiVO4/h-BN nanocomposite is 2 eV. The photocatalytic effectiveness of the nanocomposite was employed to degrade various water-polluting dyes like Rhodamine-B (Rh-B) and Congo red (CR) and antibiotics like Amoxicillin (AMX) and Cephalexin (CPX). Furthermore, under visible light, BiVO4/h-BN nanocomposites decomposed up to 93.3%, 92.9%, 94.1%, and 90.1% against Rh-B, CR, AMX, and CPX after 60 min, according to the photocatalytic treatment study. The degradation efficacy of the catalyst was studied using scavengers to understand the mechanism. The BiVO4/h-BN nanocomposites are a good and inexpensive photocatalyst for degrading techniques. Further phytotoxicity analyses were carried out using the degraded Rh-B dye sample which shows a better result when compared to non-treated dye.

Physico-Chemical Characterization and Phytotoxicity Assessment of Wastewater from Rock Phosphate Processing in Tunisia: From Seed Germination to Seedling Growth

CPG’s wastewater from phosphate ore processing was characterized and its phytotoxicity before and after physicochemical treatment inside washing units was investigated for the first time. Mineralogical, spectral, physicochemical and microbiological characterizations showed that these wastewaters are relatively alkaline due to the high calcium and phosphorus contents. In fact, numerous minerals mainly fluorapatite, clinoptilolite and gypse were identified. In addition to its high salinity (EC = 9890 µS cm−1), the BOD5/COD ratio is equal to 0.949, which allows for the estimation that this effluent is potentially biodegradable. The microbiological characterization revealed the presence of revivable aerobic bacteria as; total coliforms (TC), fecal coliforms (FC), Pseudomonas, anaerobic sulfite bacteria (ASR), and fungi (F), whereas a complete absence of Salmonella, Vibrio cholera (CV), and Helminth egg (HE) was noted. In the second part, the influence of varying concentrations of phosphate wastewater was studied on radish, lentil, wheat and fenugreek seeds. Phosphate effluents were provided at 10%, 25%, 50%, 75% and 100%. Results were compared with a control group of the same seeds, irrigated with tap water. Based on several germination tests, plant irrigated with treated or untreated effluent exhibited a prominent reduction in growth traits at all four harvests. Except plant treated with treated effluent at 25% which generally induced no significant phytotoxicity to all species and which can play a fertilizer role. The adverse effects occurred with effluent-dose dependent manner. The high toxicity of untreated effluent compared to the treated effluent was inferred from the results. Nevertheless, the treated ffluent is still toxic, except at very low concentrations acting as a fertilizer.

Phytotoxicity assessment of dandelion exposed to microplastics using membership function value and integrated biological response index

Microplastic (MP) pollution is a critical environmental issue. Dandelions could be used as a biomonitor of environmental pollution. However, the ecotoxicology of MPs in dandelions remains unclear. Therefore, the toxic effects of polyethylene (PE), polystyrene (PS), and polypropylene (PP) at concentrations of 0, 10, 100, and 1000 mg L−1 on the germination and early seedling growth of dandelion were investigated. PS and PP inhibited seed germination and decreased root length and biomass while promoting membrane lipid peroxidation, increasing O2•−, H2O2, SP, and proline contents, and enhancing the activities of SOD, POD, and CAT. Principal component analysis (PCA) and membership function value (MFV) analysis indicated that PS and PP could be more harmful than PE in dandelion, especially at 1000 mg L−1. In addition, according to the integrated biological response (IBRv2) index analysis, O2•−, CAT, and proline were sensitive biomarkers of dandelion contamination by MPs. Here we provide evidence that dandelion has the potential to be a biomonitor to assess the phytotoxicity of MPs pollution, especially PS with high toxicity. Meanwhile, we believe that if dandelion is to be used as a biomonitor for MPs, attention should also be paid to the practical safety of dandelion.

Synthesis, Characterization and Phytotoxicity Assessment of Intercalated Insect Pheromone, Lignoceric Acid-Zinc Layered Hydroxide Nanohybrid

Synthesis, Characterization and Phytotoxicity Assessment of Intercalated Insect Pheromone, Lignoceric Acid-Zinc Layered Hydroxide Nanohybrid

Piezocatalytic activity of CaO–Bi2O3–B2O3 glass-ceramics under ultrasonic vibrations

Transparent glass-ceramics of CaO–Bi2O3–B2O3 (CBBO) were fabricated using the conventional melt quench technique. X-ray diffraction and Raman spectroscopy were employed to confirm the phase of the prepared samples. Differential scanning calorimetry (DSC) was used to verify that the material was, indeed, glassy. The CBBO glass samples were subjected to heat treatment at 540 °C for 30 min and 1 h based on their crystallization temperature obtained from DSC analysis. This study focused on the piezocatalytic behavior of CBBO glass-ceramic samples. Piezocatalysis experiments were conducted on the fabricated glass-ceramic samples, and it was discovered that the samples heat-treated for 30 min (HT30m) at 540 °C showed maximum dye degradation of 61% under 240 min of ultrasonication. Experiments were repeated multiple times to confirm their reliability. Additionally, a phytotoxicity assessment was performed on the degraded dye using vigna radiata seeds. The antibacterial properties of the CBBO glass-ceramic samples were also investigated via piezocatalysis. It was discovered that the HT30m CBBO glass-ceramic sample removes 98% of Escherichia coli and 99% of Staphylococcus aureus bacteria within 120 min of ultrasonication.

Biodegradation of p-cresol by Serratia marcescens strain HL 1 in batch system: Process optimization, growth kinetic study, phytotoxicity and chlorophyll assessment

The batch experiment was performed for biodegradation of p-cresol from synthetic wastewater using an isolated gram-negative bacterial strain (i.e., Serratia marcescens strain HL 1 (EU371058)). Biodegradation rate affecting parameters such as pH (5.0–10), p-cresol concentration (20–100 mg·L−1), and retention time (24–72 h) were optimized. The maximum degradation (86.32 %) of p-cresol was obtained at an initial concentration of 60 mg·L−1, pH of 7.5, and retention time of 48 h. Based on Haldane model, maximum specific growth (μmax) of the cell was 0.2 h−1, and inhabitation constant (KI) of substrate was 76 mg·L−1. FTIR was used to identify the available functional group in biodegraded p-cresol solution. Conclusively, it was observed that a first-order model could accurately predict reaction kinetics. The rate constant values for the first-order was 0.002 L g VSS−1 h−1. Phytotoxicity and chlorophyll were also investigated.

Enzyme-free carbon dots@MgO nanocomposite as an efficient sensor for on-site detection and degradation of paraoxon toxins

Serial nanocomposites consisting of blue fluorescent carbon dots (B-CDs) and MgO nanoparticles were facilely prepared. Then on-site detection and degradation of ethyl-paraoxon were achieved and evaluated. It was revealed that ethyl-paraoxon was firstly decomposed into p-nitrophenol by MgO. Then, p-nitrophenol could significantly quench the fluorescence of decorated B-CDs due to an inner filter effect (IFE). The 0.05B-CDs@MgO showed excellent comprehensive performance among the serial xB-CDs@MgO samples due to its relatively high degradation ability towards ethyl-paraoxon and potent initial fluorescence emission intensity at an excitation wavelength of 360 nm between pH 4 and 10. Finally, based on the IFE, on-site paper sensors via color recognition app on a smartphone were explored compared with a conventional fluorescence spectrometer. Both the quantitative fluorescence intensities and G/B values showed the multi-piecewise linear correlations to ethyl-paraoxon concentration up to 3000 μg/mL in river water with a limit of detection to 0.06 μg/mL and 3.48 μg/mL as well as high recovery rates between 99%-102% and 95%–116%, respectively. The in vitro cytotoxicity and phytotoxicity assessment of the 0.05B-CDs@MgO revealed dose-dependent effects. Such portable and integrated fluorescent B-CDs@MgO nanocomposites on paper arrays show excellent potential in shortening the detection time and reducing the detection cost as a new strategy for the on-site quantitative detection and degradation of ethyl-paraoxon in actual river water.

Zinc Oxide-Based Nanoformulation Zinkicide Mitigates the Xylem-Limited Pathogen Xylella fastidiosa in Tobacco and Southern Highbush Blueberry.

The xylem-limited pathogen Xylella fastidiosa causes severe economic losses worldwide, and no effective antimicrobial disease management options are available. The goal of this study was to evaluate the efficacy of a novel ZnO-based nanoparticle formulation, Zinkicide TMN110 (ZnK), against X. fastidiosa in vitro and in planta. In vitro, minimum bactericidal concentration (MBC) of ZnK analyzed in Pierce's Disease 2 medium was estimated at approximately 60 ppm. Time-kill kinetics assay showed a 100% reduction of culturable X. fastidiosa in less than 1 h after ZnK treatment. Microfluidic chambers assays showed that ZnK also inhibits X. fastidiosa cell aggregation and growth under flow conditions. Phytotoxicity assessments in the greenhouse demonstrated that ZnK can be applied as a soil drench in 50 ml at 500 ppm/plant/week up to four times to tobacco and blueberry without causing visible damage. ZnK was also evaluated for disease control in the greenhouse using tobacco infected with X. fastidiosa subsp. fastidiosa strain TemeculaL. ZnK soil drench weekly applications at concentrations of 500 followed by 1,000 ppm (500/1,000) and 500/500/1,000 ppm (in 50 ml each), reduced X. fastidiosa populations by >2 to 3 log10 units and disease severity by approximately 57 and 76%, respectively, compared with the untreated control. Similarly, when blueberry plants infected with X. fastidiosa subsp. multiplex strain AlmaEm3 were soil drenched with ZnK at concentrations 1,000/1,000 ppm and 1,000/1,000/500 ppm (in 200 ml each), the bacterial population was reduced by approximately 1 to 2 log10 units, and disease severity decreased by approximately 39 and 43%, respectively. Overall, this study shows antibacterial activity of ZnK against X. fastidiosa and its effectiveness in plants to reduce disease symptoms under controlled conditions.