This study focused on the treatment of effluent contaminated with chromium, being driven by the application of magnetic field studies in living cells and organisms. The objective was to quantify the removal of chromium(VI), total chromium, and total organic carbon (TOC) by applying a magnetic field generated by permanent magnets of neodymium in mixed culture. The resistance of microorganisms was evaluated for 4 h and 17 min against the application of a magnetic field at frequencies of 3, 5, and 10 Hz, which correspond to flow rates of 3.93, 7.07, and 14.92 cm³ s⁻¹ in the system loop, respectively. The initial concentration of Cr(VI) was 100 mg L⁻¹. The magnetic field frequency of 5 Hz showed a higher removal of Cr(VI) (100 %), total chromium (82 %), and TOC (34 %) compared with frequencies of 3 and 10 Hz and the absence of magnetic field exposure.

Dhaka and its neighboring areas suffer from severe air pollution, especially during dry season (November–April). We investigated temporal and directional variations in particulate matter (PM) concentrations in Dhaka, Gazipur, and Narayanganj from October 2012 to March 2015 to understand different aspects of PM concentrations and possible sources of high pollution in this region. Ninety-six-hour backward trajectories for the whole dry season were also computed to investigate incursion of long-range pollution into this area. We found yearly PM₁₀ concentrations in this area about three times and yearly PM₂.₅ concentrations about six times greater than the national standards of Bangladesh. Dhaka and its vicinity experienced several air pollution episodes in dry season when PM₂.₅ concentrations were 8–13 times greater than the World Health Organization (WHO) guideline value. Higher pollution and great contribution of PM₂.₅ most of the time were associated with the north-westerly wind. Winter (November to January) was found as the most polluted season in this area, when average PM₁₀ concentrations in Dhaka, Gazipur, and Narayanganj were 257.1, 240.3, and 327.4 μg m⁻³, respectively. Pollution levels during wet season (May–October) were, although found legitimate as per the national standards of Bangladesh, exceeded WHO guideline value in 50 % of the days of that season. Trans-boundary source identifications using concentration-weighted trajectory method revealed that the sources in the eastern Indian region bordering Bangladesh, in the north-eastern Indian region bordering Nepal and in Nepal and its neighboring areas had high probability of contributing to the PM pollutions at Gazipur station.

Lignite (PK), bituminous (FI) and biomass (SE) fly ashes (FAs) were mineralogically and geochemically characterised, and their element leachability was studied with batch leaching tests. The potential for acid neutralisation (ANP) was quantified by their buffering capacity, reflecting their potential for neutralisation of acid mine drainage. Quartz was the common mineral in FAs detected by XRD with iron oxide, anhydrite, and magnesioferrite in PK, mullite and lime in FI, and calcite and anorthite in SE. All the FAs had high contents of major elements such as Fe, Si, Al and Ca. The Ca content in SE was six and eight times higher compared to PK and FI, respectively. Sulphur content in PK and SE was one magnitude higher than FI. Iron concentrations were higher in PK. The trace element concentrations varied between the FAs. SE had the highest ANP (corresponding to 275 kg CaCO₃ tonne⁻¹) which was 15 and 10 times higher than PK and FI, respectively. The concentrations of Ca²⁺, SO₄²⁻, Na⁺ and Cl⁻ in the leachates were much higher compared to other elements from all FA samples. Iron, Cu and Hg were not detected in any of the FA leachates because of their mild to strong alkaline nature with pH ranging from 9 to 13. Potassium leached in much higher quantity from SE than from the other ashes. Arsenic, Mn and Ni leached from PK only, while Co and Pb from SE only. The concentrations of Zn were higher in the leachates from SE. The FAs used in this study have strong potential for the neutralisation of AMD due to their alkaline nature. However, on the other hand, FAs must be further investigated, with scaled-up experiments before full-scale application, because they might leach pronounced concentrations of elements of concern with decreasing pH while neutralising AMD.

Acrylamide (ACR), an environmental toxin though being investigated for decades, remains an enigma with respect to its mechanism/site of actions. We aim to explicate the changes in cerebral ganglions and giant fibers along with the behavior of worms on ACR intoxication (3.5–17.5 mg/mL of medium/7 days). Neurotransmitter analysis revealed increased levels of excitatory glutamate and inhibitory gamma amino butyrate with reduced levels of dopamine, serotonin, melatonin, and epinephrine (p < 0.001). Scanning electron microscopy showed architectural changes in cerebral ganglions at 3.5 mg/mL/ACR. The learning behavior as evidenced by Pavlovian and maze tests was also altered well at 3.5 mg/mL of ACR. Electrophysiological assessment showed a reduction in conduction velocity of the medial and lateral giant nerve fibers. We speculate that the observed dose/time-dependent changes in neurotransmission, neurosecretion, and conduction velocity on ACR intoxication at 17.5 mg/ml, possibly, could be due to its effect on nerve fibers governing motor functions. The bioaccumulation factor in the range of 0.38–0.99 mg/g of ACR causes a detrimental impact on giant fibers affecting behavior of worm. The observations made using the simple invertebrate model implicate that the cerebral ganglionic variations in the worms may be useful to appreciate the pathology of the neurological diseases which involve motor neuron dysfunction, esp where the availability of brain samples from the victims are scarce.

Ivermectin (IVM) is a broad-spectrum antiparasitic drug that is regularly employed in veterinary medicine. In this work, the sorption and desorption of IVM in two Brazilian soils (N1-sand and S2-clay) as well as its leaching capacity, dissipation under aerobic conditions, and degradation in aqueous solution by photocatalysis with TiO₂ in suspension were evaluated. The kinetic sorption curves of IVM were adjusted to a pseudo-second-order model. The sorption and desorption data were well fitted with the Freundlich isotherms in the log form (r > 0.96). The Freundlich sorption coefficient (K F ᵃᵈˢ) and the Freundlich desorption coefficient (K F ᵈᵉˢ) were 77.7 and 120 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹ and 74.5 and 138 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹, for soils N1 and S2, respectively. A greater leaching capacity of IVM was observed for the sandy soil N1 than for the clay soil S2. Under aerobic conditions, the dissipation (DT₅₀) at 19.3 °C was 15.5 days (soil N1) and 11.5 days (soil S2). Photocatalysis with UVC and TiO₂ in suspension resulted in the degradation of 98 % of IVM (500 μg L⁻¹) in water in 600 s. The toxicity (Daphnia similis) of the solutions submitted to the photocatalytic process was completely eliminated after 10 min.

Dissolved organic matter (DOM) in wastewater can be characterized using fluorescence excitation-emission matrix and parallel factor (EEM-PARAFAC) analysis. Wastewater from animal farms or pharmaceutical plants usually contains high concentration of antibiotics. In this study, the quenching effect of antibiotics on the typical components of DOM was explored using fluorescence EEM-PARAFAC analysis. Four antibiotics (roxarsone, sulfaquinoxaline sodium, oxytetracycline, and erythromycin) at the concentration of 0.5∼4.0 mg/L and three typical components of DOM (tyrosine, tryptophan, and humic acid) were selected. Fluorescence quenching effects were observed with the addition of antibiotics. Among these four antibiotics, roxarsone (2.9∼20.2 %), sulfaquinoxaline sodium (0∼32.0 %), and oxytetracycline (0∼41.8 %) led to a stronger quenching effect than erythromycin (0∼8.0 %). From the side of DOM, tyrosine and tryptophan (0.5∼41.8 %) exhibited a similar quenching effect, but they were higher than humic acids (0∼20.2 %) at the same concentration of antibiotics. For humic acid, a significant quenching effect was observed only with the addition of roxarsone. This might be the first report about the fluorescence quenching effect caused by antibiotics. The results from this study confirmed the interference of antibiotics on the fluorescence intensity of the main components of DOM and highlighted the importance of correcting fluorescence data in the wastewater containing antibiotics.

Currently, the toxic effects and carcinogenic potential of individually treated arsenic (As) or cadmium (Cd) are well documented both in animal and human tissues. However, there are no data focusing on the genotoxicity of these heavy metals as a mixture at the very low concentrations of permissible limits for drinking water. In this study, we examine the genotoxicity and carcinogenic potential of single and combined treatments of As and Cd, as well as attempt to elucidate the mechanism of action of certain cell defense systems such as antioxidants, gene repair, heat shock, cell cycle control, and the apoptosis pathway. Zebrafish (Danio rerio), reared under controlled conditions with artificial diets, were treated with As and Cd, either individually or in combination, at concentrations commonly found in water (10 ppb for As and 5 ppb for Cd) and tenfold higher concentrations for 48 h. Our results indicate that separately, As and Cd treatments at low dose selectively induce antioxidant enzymes, gene repair, and caspase-independent apoptosis in gill tissue, by targeting the mitochondria, leading to oxidative stress and sub-lethal levels of DNA damage. However, tenfold higher (100 ppb As + 50 ppb Cd) treatment caused significant downregulation of genes involved in double-strand break repair and molecular chaperone genes. Additionally, the highest BCL2/BAX ratio (1.6) and lowest expression levels of caspase-3 (8.4-fold) in all treated groups were observed in same condition. These results demonstrate that both single and combined exposure to As and Cd at permissible levels is potentially safe and causes repairable genotoxicity in gill tissue. However, the highest concentration is potentially carcinogenic due to ineffective DNA repair and insufficient apoptosis.

Long-term monitoring of the content of perchloroethylene (PCE) in a river ecosystem affected by groundwater contamination was performed at a site in the Czech Republic. The quality of surface water was monitored quarterly between 1994 and 2013, and fish were collected from the affected ecosystem to analyse the content of PCE in their tissue in 1998, 2011 and 2012. Concentrations of PCE (9–140 μg/kg) in the tissue of fish collected from the contaminated part of the river were elevated compared to the part of the river unaffected by the contamination (ND to 5 μg/kg PCE). The quality of surface water has improved as a result of groundwater remediation during the evaluated period. Before the remedial action, PCE concentrations ranged from 30 to 95 μg/L (1994–1997). Following commencement of remedial activities in September 1997, a decrease in the content of PCE in the surface water to 7.3 μg/L (1998) and further to 1 μg/L (2011) and 1.1 μg/L (2012) led to a progressive decrease in the average concentration of PCE in the fish muscle tissue from 79 μg/kg (1998) to 24 (2011) and 30 μg/kg (2012), respectively. It was determined that the bioconcentration of PCE does not have a linear dependence because the decrease in contamination in the fish muscle tissue is not directly proportional to the decrease in contamination in the river water. The observed average bioconcentration factors were 24 and 28 for the lower concentrations of PCE and 11 for the higher concentrations of PCE in the river. In terms of age, length and weight of the collected fish, weight had the greatest significance for bioconcentration, followed by the length, with age being evaluated as a less significant factor.

Stormwater filtration system has proven to be effective for the removal of dissolved and particulate pollutants from roadways and car parking areas. However, the long-term treatment performance of filtration systems strongly depends on the hydraulic conductivity and sorption capacity of the filter media. This paper sought to provide information regarding the hydraulic performance, characteristics and metal concentration profiles in sediments accumulated at the surface of filtration systems (SDPL) and core filter media (FMC). The lifespan of the filter media was used to estimate the lifespan of the filter media. The results showed that saturated hydraulic conductivity of the filtration systems have significantly reduced over the operational time, yet acceptable (Kf = 5.9 × 10⁻⁵ to 1.4 × 10⁻⁴ m/s). The accumulated sediments (SDPL) were predominantly composed of fine particles with 70 % < 63 μm but the heavy metals were rather uniformly distributed in the different size fractions. The concentrations of heavy metals, particularly Cu, Pb and Zn were significantly higher in the SDPL and decreased with depth of the filter bed. However, Cr and Ni increased with depth of filter media demonstrating their removal was mainly by adsorption. Concentrations of Ba, Mn, Ti and V were comparable to Zn levels indicating comparable concentrations in roadway runoff. Simultaneous adsorption of multiple heavy metals in a column experiment demonstrated that the filter media could remain operational for over 34 years. However, there is a significant concern about their lifespan, particularly due to significant reduction in the hydraulic performance and the possibility of clogging of the systems over time. Therefore, to minimize hydraulic failure, the accumulated sediment be scraped off every 7 years.

In this study, the decolorization of a dye solution via bio-Fenton process with in situ generation of H₂O₂ by enzymatic catalyzed oxidation of glucose was investigated. For this purpose, magnetite was synthesized and was used as the support for glucose oxidase immobilization. The particle size of the magnetite was estimated to be around 42 nm according to the obtained scanning electron microscope images. The magnetite crystal size was obtained approximately 26 nm by X-ray diffraction spectrum. Effective variables on immobilization were investigated. The best immobilization conditions were achieved at pH 6, temperature of 10 °C, glucose oxidase/support ratio of 1800 U/g, and time of 2.5 h. In these conditions, 450 U of glucose oxidase was immobilized per grams of magnetite. The immobilized glucose oxidase was used for the decolorization of acid yellow 12 in batch experiments. Decolorization conditions were optimized by response surface methodology. Four parameters including pH, temperature, glucose, and Fe²⁺ concentrations in five levels were investigated. The optimum conditions were obtained as follows: pH = 4.5, T = 29 °C, initial glucose concentration of 1.5 g/L, and Fe⁺² concentration of 1.4 g/L. Decolorization efficiency after 120 min at optimal conditions in the presence of 0.3 g immobilized enzyme (450 U/g) in 100 cm³ solution was observed to be equal to 62.27 %.