Commercial usage of ZnO nanoparticles has increased recently due to its versatile applications, raising serious environmental concern because of its ultimate release of nanoparticles in aquatic ecosystem. Therefore, it is important to understand the impact of ZnO nanoparticle toxicity especially on algal flora, which is the primary producer in the aquatic food chain. In the current study, algal growth kinetics was assessed after the exposure of zinc oxide nanoparticles and its bulk counterpart to Coelastrella terrestris (Chlorophyceae). Zinc oxide nanoparticles were found to be more toxic (y = 34.673x, R² = − 0.101, 1 mg L⁻¹ nanoparticle (NP)) than bulk (y = 50.635x, R² = 0.173, 1 mg L⁻¹ bulk) by entrapping the algal cell surface. Higher toxicity may be due to oxidative stress within the algal cell as confirmed through biochemical analysis. Biochemical parameters revealed stressful physiological condition in the alga under nanoparticle exposure, as lactate dehydrogenase release (18.89 ± 0.2 NP; 13.67 ± 0.2 bulk), lipid peroxidation (0.9147 ± 1.2 NP; 0.7480 ± 0.8 bulk), and catalase activity (4.77 ± 0.1 NP; 3.32 ± 0.1 bulk) were found higher at 1 mg L⁻¹ in the case of nano-form. Surface adsorptions of nanoparticles were observed by SEM. Cell organelle damage, cell wall breakage, and cytoplasm shrinkage were found as responses under toxic condition through SEM and TEM. Toxicity was found to be influenced by dose concentration and exposure period. This study indicates that nano-form of ZnO is found to be more toxic than bulk form to freshwater alga.

A mixed community of bacteria was enriched from groundwater contaminated with naphthalene as the sole carbon source. Based on the results of 16S rRNA sequences, Acinetobacter and Pseudomonas were the predominant species in the naphthalene-enriched culture. Different initial forms of nitrogen, including nitrate, nitrite, and ammonium, were beneficial to naphthalene degradation, which was considered second-order kinetics and naphthalene could be decreased by 94.68% during the incubation period of 30 days with an initial naphthalene concentration of 0.5 mg/L. These clear biogeochemical denitrification signals, the consumption and accumulation of nitrate, nitrite, and ammonium during the incubation period, suggested that naphthalene degradation may be coupled with denitrification and DNRA metabolism. Nitrate and nitrite were reduced mainly as electron acceptors, and ammonium was utilized by microorganisms as an important inorganic nutrient for their growth and reproduction, which promoted the degradation of naphthalene. The results of this study contributed to the removal pathway and transformational mechanism of nitrogen and reveal their involvement in the anaerobic biodegradation of naphthalene.

It was investigated the potential of Rhodococcus erythropolis AW3 as a biosorbent for the removal of crystal violet (CV) dye from natural water and real effluents. The biosorbent was characterized by flow cytometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy X-ray dispersive spectroscopy (EDS), and point of zero charge (pHZPC). Batch biosorption experiments were performed to optimize different parameters involved in the biosorption process. The equilibrium was reached at 90 min at the optimum biosorbent dose of 0.50 g L⁻¹ and pH of 9.0. Results indicated that Langmuir isotherm model was the most suitable to represent the experimental data, and the highest biosorption capacity was 289.8 mg g⁻¹. Kinetic data were well fitted with the pseudo-second-order model. The thermodynamic study showed that the process was favorable, exothermic, and associated with an increase of entropy. Finally, it was demonstrated that the biosorption process using Rhodococcus erythropolis AW3 could be successfully applied to remove CV from natural water and effluents derived from clinical and industrial activities.

Our study evaluated 163 individuals, being 74 soybean farmers, occupationally exposed to pesticides, and 89 individuals from Goias municipalities, Central Brazil, with similar conditions to the exposed group, comprising the control group. Of the 74 soybean farmers, 43 exposed directly to pesticides and 31 exposed indirectly. The exposed group consisted of individuals aged 19 to 63 years, 21 women and 53 men, and the control group had ages ranging from 18 to 64 years, being 36 women and 53 men. 18.9% of the exposed group were poisoned by pesticides, and the most common symptoms were headache and gastrointestinal problems. The genotype frequencies of the rs2031920 (T>C) polymorphism in the CYP2E1 gene present significant differences between the exposed and control groups (p = 0.02), showing that 24.3% of the exposed group were heterozygotes against 6.7% in the control group. For the OGG1 gene, two SNPs, rs1052133 (G>C) and rs293795 (T>C), were evaluated and the genotype frequencies were not statistically different between the exposed and control groups. The DNA damage was distinct (p < 0.05) in the three analyzed comet parameters (tail length, Olive tail moment, %DNA) between groups. However, there was no influence of age and alcohol consumption between the groups associated with the polymorphisms in the CYP2E1 and OGG1 genes and DNA damage. We also did not find altered hematological and biochemical parameters in the exposed group. Thus, this pioneering study at Goias State carried out an overview of the health of soybean farmers. We evaluated classic laboratory exams, associated with exposure markers (comet assay) and susceptibility markers (genetic polymorphisms), emphasizing the need to expand the Brazilian health assessment protocol. We found, in soybean farmers, increased DNA damage and a higher number of heterozygotes in CYP2E1 gene, compared with the control group, despite the lack of association with age, educational level, smoking, drinking habits, and genetic polymorphisms.

Increasing environmental concern, human health and the continuous upgradation in the stringent standards of vehicular emissions have shown much interest in cleaner diesel fuels. Out of various strategies to mitigate the diesel engine emissions, use of water blended diesel in the form of emulsion has grabbed sufficient attention of the fuel research community. Various researches have shown that water-emulsified diesel has sufficient potential to improve the engine performance simultaneously with a significant reduction in the levels of nitrogen oxides (NOₓ) and particulate matter (PM) emissions. Micro-explosion phenomenon of combustion in emulsion fuel helps to provide efficient and complete combustion which in turn improves brake thermal efficiency. The current study presents a comprehensive review of the usage of water-emulsified diesel fuel in CI engines. Focusing on the performance, combustion, and emission analysis, it also talks in detail about the principle and the chemistry involved in making of a stable and homogeneous water–diesel emulsion compatible for CI engine. The literature survey concludes two crucial points. First, the water-blended diesel emulsion serves as an economical, fuel efficient, and cleaner combustion technology. Second, the optimum blend ratio, emulsifier quantity, and proper process differs in almost all the research papers and hence needed to be standardized.

Honeybee (Apis mellifera L.) provides not only bee products of immense value but also render invaluable free service as cross-pollination and propagation of several cultivated and wild species, thereby, maintaining biological diversity. Bee larvae and adults might be killed or suffer various sublethal effects when placed in contact with pollen and nectar contaminated with insecticides. The present work was conducted to investigate the toxicity of seven insecticides on laboratory using oral toxicity test and their side effects on A. mellifera in cotton fields. Results indicated that lambda-cyhalothrin was the most toxic-tested pesticide, recording the lowest LC₅₀ and LC₉₀ values at all tested periods and the lowest LT₅₀ and LT₉₀ at all tested concentrations, followed by abamectin, spinosad, chlorpyrifos, and emamectin benzoate. On the other side, dipel and pyridalyl recording the highest LC₅₀ and LC₉₀ at all tested periods and the highest LT₅₀ and LT₉₀ at all tested concentrations. As for the application of pesticides in cotton fields, the tested pesticides significantly increased the number of dead workers in comparison with control. The tested pesticides significantly decreased bee foraging activities, i.e., number of foraging workers, number of worker collecting nectar, number of worker gathering pollen grains, area of broad workers, and honey bee yields. Dipel and pyridalyl were the most safety pesticides on honey bee workers in laboratory and field, so it could be introduced as a component in IPM programs of cotton pests.

The integrated algal pond system (IAPS) is a passive wastewater treatment technology that can be used to remediate liquid waste from domestic, industrial and agricultural sources. The system exploits the mutualistic interaction between microalgae and bacteria to generate water of a quality suitable for discharge and/or reuse. During the treatment process, biomass in the form of microalgal–bacterial flocs (MaB-flocs) is generated, and this can be harvested and beneficiated in downstream processing. Here, we review literature on MaB-floc and extracellular polymeric substance (EPS) formation and discuss how essential microalgal–bacterial mutualism is at effecting IAPS-based wastewater treatment. Aggregation of microalgae and bacteria into MaB-flocs is clearly an outcome of EPS production by these microorganisms and arises for purposes of chemical and developmental interaction, protection, communication, aggregation and adhesion. The polymeric compounds which form the scaffold of this extracellular matrix comprise polysaccharides, proteins, uronic acid and nucleic acid. Natural EPS can be used as bioflocculant in water purification and in the dewatering and settling of sludge and is therefore an ideal natural replacement for commercially available synthetic polymers. Additionally, EPS are considered high value and can be used in many commercial applications. Thus, and to ensure sustained MaB-floc production in IAPS-based wastewater treatment plants, it is important that correct levels of EPS are maintained to facilitate settling and biomass recovery. Furthermore, it is the associated environmental and operational conditions that most impact EPS production and in turn, MaB-floc formation, and quality of the final IAPS-treated water.

The current research reports an efficient methodology of new sorbent (SSBC) synthesis based on neglected sepia shells for the sequestration of cationic dye (Methylene blue, MB) and an anionic dye (Reactive black 5, RB5) from aqueous solutions. The as-synthesized SSBC was produced by reaction of sepia shell powder with urea in the presence of formaldehyde. In the first part of the work, the sorbent was scrutinized by using scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectrometry, and titration (for determining pHPZC). In the second step, the influence of several parameters including pH effect, sorbent dosage, temperature, and ionic strength on the two dyes’ sorption effectiveness was examined. The sorption isotherms and uptake kinetics were analyzed at the optimum pH. Outlined results showed that the dynamic experimental obtained data followed the Langmuir isotherm profile, while the kinetic profile fitted well to the pseudo-second-order rate equation. Maximum sorption capacities reach up to 0.794 mmol g⁻¹ (254.05 mg g⁻¹) for MB and 0.271 mmol g⁻¹ (269.18 mg g⁻¹) for RB5, at pH 10.5 and 2.3, respectively. By comparing the sorption properties at different temperatures, the endothermic nature of the sorption process was revealed. Sorption processing under microwave irradiation (microwave-enforced sorption, MES) enhanced mass transfer, and a contact time as low as 1 min is sufficient under optimized conditions (exposure time and power) reaching equilibrium, while 2–3 h was necessary for a “simple” sorption. Dye desorption was successfully tested using 0.5 M solutions of NaOH and HCl for the removal of RB5 and MB, respectively. The as-prepared sorbent can be reused for a minimum of 4 cycles of sorption/desorption. Finally, the sorbent was successfully tested on spiked tap water and real industrial wastewater.

The removal behavior and characteristic of cadmium (Cd²⁺) on wheat straw char activated by CO₂ were investigated in this study. The equilibrium, kinetics, and removal isotherms were studied. The results of batch experiments revealed that the removal of Cd²⁺ was described well by pseudo-second-order and Langmuir models. The increase in activation time improved the removal of Cd²⁺, especially for the activation time of 84 min. The results suggested that chemisorption of Cd²⁺ on activated carbon was the main reaction mechanism. The maximum removal capacity of Cd²⁺ onto activated WSC-84 was 75.55 mg/g, which was much higher than other three samples activated by CO₂ with other amounts of time. According to the results of SEM, XPS, and FT-IR, complexation with surface oxygen-containing functional groups, ion exchange, and precipitation were the possible mechanisms of the removal process. It is suggested that the experimental results will enhance the comprehensive understanding of the activation of biomass and its utilization in the restoration of Cd-contaminated soil.

Arsenic (As) is a well-known highly toxic and carcinogenic element. A combination of electrodialytic remediation (EDR) after soil washing with flocculant addition targeting remediation of a soil polluted with As from wood preservation industry is the focus of this paper. The fine fraction (< 0.063 mm) from the washed soil after dry sieving was also considered. The EDR experiments were carried out in a 2-compartment cell applying 0.01 mA/cm² during 14, 7 and 3 days. The suspended soil slurry was placed in cathode compartment separated by anion exchange membrane (AEM) of the anolyte where the pH was kept at 10. The soil was highly polluted with As, and the EDR was able to remove between 50 and 80% corresponding to 400–478 mg As/kg of soil. The major part of the As was removed within the first 3 days (63%), and approx. 10% more of As was released doubling the time of the experiment: 72% in 7 days and 80% in 14 days. The pre-treated soil showed higher As initial concentration, but did not show a clear advantage in terms of removal rate as the original soil (not washed or sieved) showed 80% of As removal comparing with 61% and 50% for washed and fine fraction, respectively (although the absolute removed concentration was similar). The sequential extraction results confirmed that As was bound into more mobile fractions in original soil, and the higher removal was mainly due to its larger exchangeable and reducible fractions compared to the oxidizable and residual fraction in pre-treated soil.