This study aims to investigate the photocatalytic degradation performance, mechanism, and dynamics of methyl orange (MO) which is a widely used organic dye in textile industries as well a hazardous wastewater pollutant. The degradation process was catalyzed by employing a synthesized Fe₃O₄ magnetic nanoparticle (NP) using the coprecipitation method. The structural and morphological properties of the synthesized Fe₃O₄ NPs were investigated by employing XRD, HR-SEM, and XPS, which proved that acquired Fe₃O₄ NPs were in a pure phase. Moreover, the crystallite sizes fall in the range of 28–31.8 nm and were estimated by applying the Scherrer equation on the XRD spectrum as well as calculated independently by applying a statistical approach on the SEM micrographs. The UV–Vis maximum in the visible range at 468.8 nm consists of two absorption frequency bands due to the effect of the hydrogen-bond interaction between water and the azo nitrogens in the MO. A non-monotonic spectral dynamic accompanied by peak wavelength shifts, as well as the absolute signal amplitude and signal area of the MO band, suggests that a cleavage of the azo bond is not the only and/or the dominant process in the photocatalytic oxidization of the MO in a protic solvent. The overall absorbance process is a complicated response to a combination of nonspecific and specific solute-solvent interactions, dipole-dipole interactions, hydrogen-bonding networks, and other possible intermolecular interactions such as hydrophobic/hydrophilic interactions. A bi-exponential decay was found to be the best fitting function to model the decay of the time-dependent electrical conductivity of the MO aqueous solution under photocatalytic oxidization. The Fe₃O₄ NPs exhibited a 98.3% removal of MO within 110 min. Photocatalytic degradation of methyl orange can be modeled to the first-order model with a rate constant k of 0.037 min⁻¹ taking into account the initial concentration of 1175 ppm of MO. The degradation/decolorization efficiency deduced from the low-frequency band of the visible spectra is around 99.4% after 110 min. The real-time degradation/decolorization efficiencies deduced from the overall absorbance maxima and the low-frequency band have a discrepancy of 50.1% at 20 min and 12.3% at 60 min representing the progressive attenuation of the H-bond impact dissociation of MO (degradation/decolorization).

Fungi are one of the bioaerosols in indoor air of hospitals. They have adverse effects on staff and patients. The aim of this study was to investigate the effects of three incubation temperature on the density and composition of airborne fungi in an indoor and outdoor space of hospital. Sabouraud dextrose agar was used for culture the fungi. For improvement of aseptic properties, chloramphenicol was added to this medium. The density of airborne fungi was less than 282 CFU/m³. The highest density was detected in emergency room and the lowest of them was in neonatal intensive care unit (NICU) and operation room (OR). Results showed that fungi levels at 25 °C were higher than 37 and 15 °C (p = 0.006). In addition, ten different genera of fungi were identified in all departments. The predominant fungi were Fusarium spp., Penicillium spp., Paecilomyces spp., and Aspergillus niger. Moreover, the density and trend of distribution of Fusaruim spp. in the indoor space was directivity to outdoor space by ventilation system. The present study has provided that incubation temperature had effect on airborne fungi remarkably. We are suggested that more studies would be conducted on incubation temperature and other ambient factors on airborne fungi.

An electrokinetic batch treatment scheme was investigated combining sequential electrocoagulation (EC) and chemical coagulation treatment (CC) processes. Synthetic and microbrewery wastewaters were tested in this investigation. The generated results demonstrated the capacity for the integration of EC-CC to effectively remove phosphorus contamination from wastewater under varying operating conditions. The effect of several operational parameters such as current density, conductivity, nutrient loading, and electrolysis time were investigated. The results showed that increased salinity can significantly accelerate the removal of phosphorous during EC treatment with 84.2% and 92.4% removal found for the applied power of 5 and 10 W, respectively. The addition of a sequential chemical coagulant stage following treatment by EC demonstrated the potential for an integrated EC-CC system to lower energy consumption while maintaining effective nutrient removal capabilities. Removal of phosphorous at 95% and 98% was achieved in just 10 min of EC treatment coupled with the addition of 15 mg/L aluminum sulfate. The estimated power consumption over a 10-min period was found to be 0.28 Kwh/m³ with a dissolution rate of 0.28 g/cm² min held at a constant current density. The experimental anode dissolution rate for the synthetic wastewater ranged between 0.13 and 0.24 g/cm² min encompassing all salinity levels. The anode dissolution rate increased during treatment of microbrewery wastewater with 0.67 g/cm² min for 10 W EC treatment. This was attributed to the increase in current density and nutrient loading resulting in increased energy consumption and electrode passivation.

The presence of heavy metals in food is a threat to human health. Exposure to heavy metals as a result of consumption of contaminated vegetables, as well as their toxicity, is a serious problem.Different branches of industry and the road traffic have a significant impact on environmental pollution with heavy metals. Municipal and industrial sewage also is an important source of those substances. Furthermore, the mineral content of vegetables depends on factors such as the natural content of trace elements in the environment, their levels in mineral fertilizers, and fertilizer doses. In the soil, a natural source of these metals is bedrock. In soils used for agricultural purposes, some quantities of metals are introduced together with fertilizers, both organic and mineral. Additionally, another sources of the metals are plant protection products.Heavy metal dynamics in the soil and their uptake by plants are influenced by soil properties, which play a key role in the bioavailability of these metals. Metal mobility and assimilation are also influenced by the addition of organic and inorganic matter. A significant body of evidence also suggest that the age of the soil plays an important role in modulation of metal bioavailability to plants.Apart from being influenced by the soil-related factors, absorption of metals differs in different types of plants. A significant variation in metal concentrations was also found depending on their location in plant tissues, on plant species, or even on varieties of the same species.

Environmental fate and impacts of graphene oxide (GO) nanoparticles are strongly influenced by their subsurface behaviors. The present work examined the aggregation and transport behaviors of GO in saturated sand columns under different temperature (6 and 24 °C), surfactant concentration (0.04% and 0.4%), cation valence, and electrolyte concentration conditions. In monovalent electrolyte (NaCl), although the presence of cationic surfactant (CTAB) notably increased GO stability and mobility, GO ripening happened due to their concurrent aggregation and transport in the columns. GO particles were more mobile at a lower temperature probably because the CTAB coating of GO increased with decreasing temperature, leading to stronger electrostatic repulsion. Furthermore, GO retention in the media increased with the increase of NaCl concentration due to the enhanced compression of the electric double layer. In multivalent electrolyte (CaCl₂ or AlCl₃), the presence of CTAB greatly improved GO stability and mobility and no deposition occurred in saturated porous media under all the tested conditions. This is because the CTAB coating of GO diminished the cation bridging effects in both GO-GO and GO-sand systems. Results from extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory considering steric repulsion suggest that secondary minimum aggregation and depositions were the main mechanisms of GO retention transport in monovalent electrolyte in saturated porous media.

Combustion of fossil fuels including coal is one of the sources of mercury pollution. Combustion waste from fly ash disposal sites poses a problem for the environment and constitutes a potential source of Hg, thus phytostabilisation is a crucial goal in the mitigation of fossil fuel impact. The paper presents mercury (Hg) concentration in technosols from combustion waste and in individual biomass components (fine roots, bark, stem wood and leaves) of alder species (black, gray and green alder) introduced as part of a long-term experiment to develop a method of phytostabilisation and afforestation of a lignite combustion disposal site. Mercury content in the combustion waste was elevated compared to the data for natural soils from uncontaminated forest areas, however, it did not exceed the amounts considered to be toxic. Hg content in technosols was related to clay and silt fraction content and phosphorus content. Mercury in the alder biomass accumulated mainly in the underground part, especially in the fine roots and displayed a positive correlation with acid and alkaline phosphatase and sulfur content, with no differences in the accumulation of Hg between the alder species. The obtained results indicate that the fine roots are the frontier of Hg biosorption in developed alder systems on combustion waste disposal sites.

Tannins are special plant metabolites used in leather processing that act as pollutants. These substances are toxic to aquatic biota and can cause cell rupture. These harmful effects make the treatment of tannery wastewater difficult. Phytoplankton species are community components that are rarely considered in the biodegradation of organic compounds. However, in association with bacteria, these organisms can improve the biodegradation of pollutants by different mechanisms. The aim of the present study was to evaluate the potential of non-axenic cultures of Chlorella vulgaris containing Lactobacillus casei and Synechococcus sp. containing Rhizobium rosettiformans and Sphingomonas koreensis to biodegrade tannic acid (TA). Cultures in BG-11 medium containing TA (250 mg L⁻¹) were incubated under a photoperiod or in the dark and monitored for 96 h. The cultures with added TA grew more than the control cultures under both the photoperiod and dark conditions. A reduction in the TA concentration and the TA metabolite gallic acid was observed under both conditions. Ellagic acid was identified and demonstrated resistance to biodegradation under the evaluated conditions, and neither of the other metabolites was detected. BG-11 culture medium is poor in organic material; therefore, microalgae and cyanobacteria contribute to bacterial metabolism. Under experimental conditions, phytoplankton species seem to contribute to the biodegradation of tannin residues, and in natural environments, they may aid in the bioremediation of sites contaminated by these pollutants.

The presence of toxic metals in soil enables them to be absorbed by plants. The RDC 42/2013 published by Brazilian Health Regulatory Agency (ANVISA) defines the maximum values of cadmium (0.4 mg kg⁻¹) and lead (0.6 mg kg⁻¹) in yerba mate commercialized in Common Market of the South (Mercosul). This work is a retrospective study that aimed to evaluate cadmium and lead levels in processed yerba mate and in natura leaves in Southern Brazil. The cadmium and lead concentrations in 370 processed yerba mate and 122 in natura leave samples obtained in Southern Brazil were analyzed. In 47.56% of the processed samples, the levels of cadmium and/or lead were found to be above the authorized levels. The cadmium levels found in the processed yerba mate were 0.37 ± 0.19 mg kg⁻¹, and the corresponding values for lead were 0.34 ± 0.21 mg kg⁻¹. Values above the authorized levels were also found in the non-processed leaves. Studies are required to determine whether these levels are natural or represent contamination.

Mobile sources are considered to be one of the most important sources of air pollution among which are motor vehicles, recognized as the major contributor of air pollutants in urban areas. To determine the emissions for CO, SO₂, and NO₂ from motor vehicles as part of the attempt to realize the extent of traffic air pollution, measurements were carried out in two heavily traversed traffic tunnels in Tehran metropolitan area. The concentrations of pollutants and metrological and traffic data were collected through intensive measurements from September 27 to October 17, 2016. Resalat Tunnel fleet was composed of about 10% diesel-fueled vehicles and 90% non-diesel-fueled vehicles while throughout the entire duration of our campaign, only non-diesel-fueled vehicles traversed Niayesh Tunnel. Under an average traffic speed of 43 km h⁻¹, emission factors from Resalat Tunnel campaign were measured to be (6.59 ± 2.69)E+3, (1.42 ± 0.84)E+2, and 6.80 ± 4.99 mg km⁻¹ for CO, SO₂, and NO₂, respectively. These values were respectively 11% higher, 22% lower, and 40% higher than those from Niayesh Tunnel measurements which were recorded at a traffic speed of 30 km h⁻¹. Current results indicate that the vehicular emissions in certain countries, especially the developing ones and in this case, Iran, are quite different from those measured in developed countries and that the high emission levels of SO₂ in Iran are associated with the high sulfur content of the gasoline.

Alkali-leaching residual wire sludge (AWRS) is an abundant by-product in the harmless disposal process of wire rope sludge. In this study, we modified AWRS through thermal treatment to produce a low-cost and highly efficient adsorbent for the removal of Cu²⁺ and Ni²⁺ from wastewater. The results indicated that AWRS calcinated at 700 °C exhibited maximum Cu²⁺ and Ni²⁺ removal capacities (36.48 mg/g and 46.58 mg/g, respectively). The adsorption process was observed to follow the Elovich kinetic model and the Langmuir–Freundlich isotherm model. The sorption of Cu²⁺ and Ni²⁺ on AWRS700 was highly pH dependent and behaved optimally at the solution pH values of 6 and 5, respectively. Column studies and physicochemical analyses (XRD, SEM-EDS, and XPS) indicated that the sorption of Cu²⁺ and Ni²⁺ on AWRS700 was mainly governed by the chemisorption mechanism, and this was attributed to active metal oxides (Fe₂O₃, CaO, and Al₂O₃) in AWRS700. Specifically, Cu²⁺ is mainly adsorbed on AWRS700 in the form of Cu(OH)₂, CuO₂, and CuFeO₂, and Ni²⁺ is mainly adsorbed in the form of NiAlO₄, Ni₂O₃, and Ni(OH)₂. Given the low-cost and high adsorption efficiency of AWRS700, the developed AWRS700 is a promising adsorbent for Cu²⁺ and Ni²⁺ removal from wastewater.