In the textile industry, the amount of dye unfixed in fabrics is discarded with wastewaters. Effluents of this nature can be treated efficiently by adsorption on activated bone char, but the reuse of adsorbent is necessary for the technique to be economically feasible. Therefore, the objective of this work was to study the process of desorption of BF-5G blue dye from a bone char fixed-bed column. Solutions of sodium chloride, acetic acid and ethyl alcohol were tested as regenerating agents. Due to the hydrophobicity effect of organic solvent molecules, the highest desorption capacity was observed for ethyl alcohol solution, and the fixed bed was reused after six cycles of adsorption. The other solutions did not promote significant desorption. The results showed that adsorption of the dye involved irreversible interactions between adsorbate molecules and bone char. However, the use of acetic acid solution resulted in the neutralisation of some of the adsorbent surface charges, allowing the fixed bed to operate for a longer time in the second cycle than in the first.

Great efforts have been made over the years to assess the effectiveness of air pollution controls in place in the metropolitan area of São Paulo (MASP), Brazil. In this work, the community multiscale air quality (CMAQ) model was used to evaluate the efficacy of emission control strategies in MASP, considering the spatial and temporal variability of fine particle concentration. Seven different emission scenarios were modeled to assess the relationship between the emission of precursors and ambient aerosol concentration, including a baseline emission inventory, and six sensitivity scenarios with emission reductions in relation to the baseline inventory: a 50% reduction in SO₂ emissions; no SO₂ emissions; a 50% reduction in SO₂, NOₓ, and NH₃ emissions; no sulfate (PSO₄) particle emissions; no PSO₄ and nitrate (PNO₃) particle emissions; and no PNO₃ emissions. Results show that ambient PM₂.₅ behavior is not linearly dependent on the emission of precursors. Variation levels in PM₂.₅ concentrations did not correspond to the reduction ratios applied to precursor emissions, mainly due to the contribution of organic and elemental carbon, and other secondary organic aerosol species. Reductions in SO₂ emissions are less likely to be effective at reducing PM₂.₅ concentrations at the expected rate in many locations of the MASP. The largest reduction in ambient PM₂.₅ was obtained with the scenario that considered a reduction in 50% of SO₂, NOₓ, and NH₃ emissions (1 to 2 μg/m³ on average). It highlights the importance of considering the role of secondary organic aerosols and black carbon in the design of effective policies for ambient PM₂.₅ concentration control.

Surface waters are used by local populations for different purposes, such as recreational activities, water source for human and animal consumption, and irrigation among others, which lead to the need for management strategies on water health and associated risks. During this study, we investigated physicochemical parameters, fecal coliform bacteria, and infectious human enterovirus detection to determine the water quality in different beaches (categorized as an urban area, non-urban areas, and an intermediate position) from San Roque Dam, in Argentina. Multivariate techniques were applied. Principal component analysis allowed identification of subgroup of variables responsible for the water quality. A cluster analysis and multivariate analysis of variance showed the urban beach as the highest pollution area. The following variables (measured at the urban beach) would be enough to describe the quality of the aquatic body: nitrites, fecal coliforms, total phosphorous, and infectious human enterovirus. The infectious human enterovirus was an independent variable detected in 69.1% of the samples showing a steady frequency of detection during the whole period studied and could identify human fecal contaminations as a source of water pollution. The selected variables would contribute to water quality regarding the risk for human health using San Roque dam waters for recreational propose.

Non-thermal plasma (NTP) degradation of low-concentration acetone was investigated in a cylindrical dielectric barrier discharge reactor. The effects of oxygen content and flow rate on the removal efficiency at various discharge powers were examined in real-time. The acetone removal efficiency decreases drastically and then remains stable or increases gradually as the O₂ content increases from 0 to 25%, and further to 50%. The organic by-products were characterized and quantified using a real-time proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) instrument. The observed organic compounds, with concentrations about ppbv/ppmv by volume, were mainly formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, and acetic acid. The discharge power was a critical factor affecting the concentration of the organic by-products and the selectivity toward CO₂. The mechanism study based on the by-product monitor in real-time showed that acetone firstly fragments into methyl radicals, acetyl radicals, and H; then, the methyl and acetyl radicals are oxidized by O or OH radicals into acetaldehyde, methanol, and other compounds. It seems that acetaldehyde could be an intermediate in acetone decomposition. Firstly, most of the acetone molecules were decomposed into acetaldehyde molecules; then, the acetaldehyde molecules continued to be decomposed and oxidized into other compounds, such as acetic acid and formaldehyde. These investigations not only proposed a detail decomposition mechanism for acetone in dielectric barrier discharge reactor, but also provided a potential way to analyze and evaluate the practicability of NTP removal of VOCs.

The assembly of graphene oxide with biomass or polymers to form 3D hydrogels with excellent mechanical properties has become a research hotspot. In this work, the sponge-like kaolin/chitosan (CS)/reduced graphene oxide (rGO) composite was prepared for adsorption by simple self-assembly without cross-linking agent. The morphology, composition, surface properties, and pore size of as-prepared materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), zeta potential analyzer, Brunauer-Emmett-Teller surface area measurement (BET), and scanning electron microscopy (SEM). The effects of raw material ratio, contact time, temperature, pH, ionic strength, and recycling times on adsorption performance were investigated in detail. The results indicate that the composite has good absorption capacity for Cr(VI) and alizarin yellow R (AYR). Besides, composite hydrogel also exhibits excellent flexibility and good repeatability, which confirms its great potential as an adsorbent to remove pollutants in the water environment.

In the current study, the toxicity bioassay of three pollutants abamectin (ABM), thiamethoxam (TMX), and acrylamide (ACR) against land snails Theba pisana was measured. Also, the ecotoxicological effects of dietary exposure to sublethal concentration (1/20 LC₅₀) of these pollutants for 2-week exposure and 1-week recovery on some physiological endpoints evaluated as feeding activity, growth response, and carbonic anhydrase activity as a marker in charge of shell formation and seromucoid level as a marker in charge of mucus synthesis of the snails were studied. The results exhibited that the 48-h LC₅₀ values were 0.91, 313.8, and 45.7 μg/g dry food for ABM, TMX, and ACR, respectively. The sublethal concentrations of these pollutants in the diet after 2-week exposure were found to reduce the food consumption and inhibit growth rate of the snails. Also, the data illustrated that carbonic anhydrase activity was significantly decreased. On the other hand, there was a significant increase in the seromucoid level as a marker responsible for mucus synthesis in ABM- and TMX-exposed snails, while ACR showed significantly decreased level when compared to control. After 1-week recovery, the tested endpoints of treated snails were slightly repaired but still less than that of the untreated animals. The overall outcome of this investigation suggests the utility of this animal as a good bioindicator organism for ABM, TMX, and ACR exposure in pollution monitoring studies.

The northern Beibu Gulf is one of the major habitats for the Indo-Pacific humpback dolphin (Sousa chinensis) in China. In this habitat, the core distribution zone of humpback dolphins was confined to the Sanniang Bay (SNB) and Dafengjiang River Estuary (DRE) areas. In our present research, the sediments of 14 sampling sites across the SNB and DRE waters were collected and further conducted for microbiomic and environmental analysis to explore the ecosystem characteristics of major humpback dolphin habitats in Northern Beibu Gulf. The environmental condition includes ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), dissolved reactive phosphorus (DRP), sulfur content in the form of sulfuric acid (SO₄²⁻-S), Fe, and heavy metals (including Cu, Zn, Cd, Pb, and As). The composition of the bacterial community was characterized by 16S ribosomal DNA analysis of the V3–V4 regions using the Illumina-based sequencing platform. The environmental characteristic of the nutrient elements and heavy metals indicated that SNB suffered more anthropogenic impact than DRE. The comparably higher concentration of NH₄⁺-N, NO₃⁻-N, DRP, Pb, and Cd in the SNB region was detected. The comparably higher nutrients in the SNB may have resulted in higher biomass and lower dissolved oxygen (DO) profile, which was further proved by Landsat thermal image data. The microbiome analysis showed that the DRE region was oligotrophic and SNB reflected an anaerobic environment in the sediments. Environmental factors rather than the spatial distance determined the similarity of bacterial community among different sites. Ecological associations between environmental, oceanographic, and bacterial characteristics were illustrated, which exhibited strong mutual associations. Our findings presented a feasibility that integrates empirical and remote sensing data to distinguish ecological features and evaluate ecosystem healthiness for the humpback dolphin habitats.

The transportation sector consumes 25% of world energy with 23% of the world’s total carbon emission. Therefore, it is necessary to investigate the integrated effect of fossil fuel source of energy consumption, economic development, and total population on CO₂ emission based on environmental degradation transportation sector. We employed the econometric methodologies such as a hybrid error correction model, regression coefficients, platykurtic distribution, Dickey-Fuller test, and co-integration test in order to justify empirical analysis for Pakistan transport sector. Results reveal that an increase in economic growth, urbanization, and energy consumption increased transport-based environmental degradation urbanization. Moreover, very interestingly, during this period, energy consumption has increased by 13.5%, and it shows a high dependence of economic growth on energy consumption. Further, the CO₂ emission and energy consumption per capita has a positive relationship. Finally, this study has proposed some suggestion for policy and decision-makers to mitigate environmental degradation as well as make transport sector environmentally sustainable.

Fluoride is widely distributed in the environment, and excessive fluoride intake can induce cytotoxicity, DNA damage, and cell cycle changes in many tissues and organs, including the kidney. Accumulating evidence demonstrates that selenium (Se) administration ameliorates sodium fluoride (NaF)-induced kidney damage. However, the potentially beneficial effects of Se against NaF-induced cytotoxicity of the kidney and the underlying molecular mechanisms of this protection are not fully understood. At present, in this study, the normal rat kidney cell (NRK-52E) was used to investigate the potentially protective mechanism of Se against NaF-induced apoptosis, by using the methods of pathology, colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blot. The experiment was designed with a control group, two NaF-treated groups (NaF, 5, 20 mg/L), two sodium selenite-treated groups (Na₂SeO₃, 17.1, 34.2 μg/L), and four Se + NaF-treated groups (Na₂SeO₃, 17.1, 34.2 μg/L; NaF, 5, 20 mg/L). The results indicate that selenium can attenuate apoptosis and AMPK phosphorylation in the NRK-52E cell induced with fluoride. These results imply that selenium is capable to modulate fluoride-induced NRK-52E cell apoptosis via regulating the expression levels of the proteins involved in mitochondrial pathway and changes in p-AMPK expressions may also be a key process in preventing fluorosis.

In order to overcome photocatalytic technology application limitations in water due to weak light intensity, it is crucial to synthesize photocatalysts that respond to weak light. In this study, porous and oxygen-doped carbon nitride (CN-MC) was synthesized via supramolecular preassembly technology using melamine and cyanuric chloride. The carbon nitride catalyst produced via this technology has a relatively high surface area (63.2 m² g⁻¹), irregular pores, and oxygen doping characteristics, which enhance the light capture capacity, increase the number of reactive sites, and accelerate electron–hole separation efficiency. Thus, the CN-MC exhibited excellent photocatalytic activity during the degradation of organic pollutants Rhodamine B (RhB, 95% removal within 6 h) and tetracycline hydrochloride (TC-HCl, 70% removal within 6 h) under low-intensity light (the light intensity = 0.8~1.8 mW cm⁻² with a wavelength range of 300–700 nm). Mechanistic analysis showed that ·O₂⁻ and ·OH were the dominant active free radicals during RhB and TC-HCl photocatalytic degradation over CN-MC. The proposed synthesis strategy effectively improves the photocatalytic activity of graphite carbon nitride under weak light by producing a porous morphology and oxygen atom doping.