On November 5, 2015, after the collapse of the Fundão tailings dam, a massive amount of iron mine waste was released into the Doce River system in southeast Brazil. The aim of our study was to determine the mass fractions of potentially toxic elements in soil affected by the deposition of material by the waste wave. A preliminary screening was performed with portable X-ray fluorescence spectrometry (PXRF) and principal component analysis (PCA). The EPA 3050B method was further applied to digest the samples for quantitative determination of As, Ba, Cr, Cu, Mn, Ni, Pb, V, and Zn by inductively coupled plasma mass spectrometry. PCA was useful to classify the mine waste samples based on the Fe signal from the PXRF spectra, in spite of the heterogeneous nature of the material discharged into the Doce River system. The anomalous levels of As (up to 164 mg kg⁻¹) and Mn (as high as 2410 mg kg⁻¹) found in some mine waste and affected soil samples are within the background ranges typically observed in the soils of the Iron Quadrangle region. The toxicity characteristic leaching procedure shows no evidence of hazards regarding As, but a high natural background level of Mn was found in the mobile fraction. This preliminary environmental assessment highlights the importance of evaluation of long-term effects on soil directly impacted, as well as on the aquatic biota of the Doce River system and adjacent coastal environment given the large affected area, which includes regions with varying background levels of toxic elements.

In this study, in-house isolated laccase isoforms, i.e., Lac-I and Lac-II of the basidiomycete Pycnoporus sanguineus (CS43), were evaluated in relation to their Remazol Brilliant Blue R (RBBR) dye degradation capacity. A modified Dhouib medium additionally supplemented with 3% ethanol as a secondary inducer was used to propagate P. sanguineus CS43 for enhanced production of laccase under liquid state fermentation. The crude laccase extract was purified by passing through ion exchange diethylaminoethanol (DEAE)-Sepharose and gel filtration-based Sephadex G-200 column chromatography. The purified laccase fractions were subjected to the electrophoresis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed two laccase isoforms Lac-I and Lac-II with 66 and 68 kDa, respectively. To explore the industrial applicability, for RBBR dye, degradation efficiencies ranged from 82 to 88% after 3 h of incubation for both; Lac-I and Lac-II at both concentrations were recorded. However, with 8 U/mL, the degradation ranged between 70 to 80% during the first 5 min of incubation. Enhanced degradation of RBBR dye was obtained in the presence of violuric acid and N-hydroxypthalamide as laccase mediators. Finally, using RBBR as a substrate kinetic characterization of both Lac-I and Lac-II isoforms was performed that revealed K ₘ (0.243 and 0.117 mM for Lac-I and Lac-II) and V ₘₐₓ (1.233 and 1.012 mM/Sec for Lac-I and Lac-II) values, respectively.

Little is known about the potential toxicity of Cu nanoparticles (nCu), Cr nanoparticles (nCr), and their mixtures to aquatic organisms. To fill this gap, a comprehensive toxicity assessment was conducted using Daphnia magna as a test organism, including a 48-h acute toxicity test, a 21-day chronic test, and a feeding experiment. Four biomarkers were estimated after exposure to nCu, nCr, and their mixtures for 7 days, including acetylcholinesterase (AChE), catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST). The results at all endpoints showed that nCu was more toxic than nCr. The 48-h median lethal concentration values of nCu and nCr were 0.63 and 1.57 mg/L, respectively. Significant inhibition of reproduction and growth of D. magna was found, and the intrinsic rate of natural increase was a sensitive parameter for nCu and nCr during the 21-day exposure. A concentration-dependent decrease in filtration and ingestion was observed which was consistent with inhibition of reproduction and growth of D. magna. The biochemical responses revealed an increase in GST activity and decrease in AChE activity, while SOD and CAT activities were increased at low concentrations and decreased at high concentrations for all exposures. Collectively, our results confirmed that nanoscale Cu and Cr can exert negative effects at different levels on D. magna.

The process for extracting sugarcane juice (Saccharum officinarum) represents the point of greatest contamination in sugarcane mills. Sodium dithiocarbamate also known as metam-sodium or MS is added to inhibit the growth of microorganisms especially Leuconostoc mesenteroides which is responsible for forming polysaccharides. Metam-sodium, upon decomposition, produces highly toxic byproducts. According to literature, under acidic conditions, MS is hydrolyzed resulting in methylamine (MA), CH₃NH₂, and carbon disulfide (CS₂), and in dilute alkaline solutions, MS produces an oxidation reaction characterized by the formation of elemental sulfur (S) and methyl isothiocyanate (MITC). In this paper, it was studied how MS decomposes to MITC and/or MA considering the effects of the matrix (methanol and water); of temperature (4 and 25 °C); of processing time (0, 1, 2, 3, 4 days); and of pH (4.0, 4.5, 7.0). A second experimental design considering the effects of the matrix (water and sugarcane juice); of temperature (4, 25, 35, 45 °C); of processing time (30, 300 min); and of pH (4.0, 4.5, 7.0) was derived from the results obtained considering MITC and/or MA formation. According to the statistical analysis of these results (p < 0.05), the order of the influential factors was as follows: time > matrix > pH > temperature. Results also indicated that the water matrix at pH = 4.5 and 45 °C had the lowest degradation rate (k), with a value of 8.82 day⁻¹, while for the sugarcane juice matrix at the same pH and temperature conditions was larger, with a k value of 30.07 day⁻¹. These results show that the matrix is also important for the degradation of dithiocarbamate to MITC and to MA.

Several studies have demonstrated that the most effective way to control eutrophication is to reduce phosphorus input at the scale. Water quality monitoring programs need to separately evaluate the different polluting sources to provide a suitable estimate of their relative contributions and thus accurately prioritize possible restoration actions. Urban area cases, where a portion of untreated wastewater is often discharged directly into receiving surface waters by combined sewer overflows (CSOs) during rain events, remain unsolved. In this context, an urban watershed located in Northern Italy with 60 CSOs has been chosen as a case study, and four rainy events have been hourly monitored. The proposed monitoring program consists of the combined use of caffeine and turbidity to estimate the volume and phosphorus load spilled into the river from the CSOs, respectively. Caffeine proved to be a suitable molecule to quantify the volume of wastewater discharged into water bodies, based on a per capita caffeine load of 10.8 mg inhab⁻¹ d⁻¹, estimated in the present work. This research showed that, on average, more than half of the total phosphorus loads transported by the river is due to the CSO discharges (56.5%). The knowledge of the prevailing responsibility of the CSO discharges for the Lambro River quality allows prioritizing effective restoration actions.

Distribution of ten taste and odor (T&O) compounds were investigated in 135 finished water samples from 43 drinking water treatment plants (DWTPs). 2-Methylisoborneol (MIB), geosmin, and 2,4,6-trichloroanisole (2,4,6-TCA) were detected in 53.4, 41.5, and 14.1% of the samples, respectively. The corresponding concentrations were in the range of 18.0–53.1 ng L⁻¹ for MIB, 4.2–6.4 ng L⁻¹ for geosmin, and 0.5–6.6 ng L⁻¹ for 2,4,6-TCA. The other seven T&O compounds, β-ionone, 2,3,6-trichloroanisole (2,3,6-TCA), 2,3,4-trichloroanisole (2,3,4-TCA), 2,4,6-tribromoanisole (2,4,6-TBA), 2-isobutyl-3-methoxypyrazine (IBMP), 2-isopropyl-3-methoxypyrazine (IPMP), and trans-2,cis-6-nonadienal (NDE) were never found in all samples. The results from finished water of DWTPs compared with associated reservoirs indicated that 2,4,6-TCA was formed in the water treatment processes. To determine the chemical formation of 2,4,6-TCA by chlorination, the concentrations of different chloroanisoles in anisole-containing water at pH 5.5–9.0 and 25 °C were measured. The results from chlorination showed that only 2-chloroanisole (2-CA), 4-chloroanisole (4-CA), and 2,4-dichloroanisole (2,4-DCA) could be detected. Their formation rates were all below 3.3% at each pH value, but the reaction was more active at pH 5.5 because of acid catalyzed effect. Accordingly, the chemical formation of 2,4,6-TCA by chlorination was not confirmed in this study, which suggested that the formation of 2,4,6-TCA was related to the methylation of 2,4,6-trichlorophenol with fungi. These findings increase our understanding on the formation of 2,4,6-TCA and provide insights into managing and controlling T&O problems in drinking water.

Electrocoagulation (EC) technology is an attractive alternative for industrial wastewater treatment due to its simplicity, low operation cost, less sludge production, less chemical addition, and larger and more stable floc formation. The main objective of this research is to investigate the effect of using powdered residuals from water purification plants (PRWPP) on dye removal efficiency and energy consumption under various operational conditions (pH, initial dye concentration, and applied voltage) in order to enhance the EC performance. A series of laboratory-scale experiments were conducted using an EC bench-scale reactor with iron electrodes. The addition of PRWPP to the EC system increases the dye removal efficiency from 32.9 to 97.2% and decreases the energy consumption from 6.08 to 2.06 kWh/kg dye removed. The highest dye removal efficiency was achieved at a PRWPP dosage of 2 g/l, an applied voltage of 5 V, and an initial pH value ranging from 6 to 9. The higher the dye influent concentrations discharged to EC, the lower the removal efficiency achieved and current efficiency. PRWPP has a beneficial effect on the EC performance in terms of the dye removal efficiency as well as the energy consumption.

This work studies the degradation of safranin T (SF, a recalcitrant pollutant) by an electrochemical process and three photochemical advanced oxidation technologies (TiO₂ photocatalysis, UV/H₂O₂, and photo-Fenton). The degradation routes of each process were elucidated initially. Based on the mineralization extent, improvement of the treated solutions’ biodegradability, and energy consumption, the most suitable process was identified. Interestingly, in the electrochemical system, safranin T was efficiently eliminated through electrogenerated HOCl. In contrast, the popular photo-Fenton process was unable to degrade SF. Moreover, the pollutant was refractory to highly energetic UV₂₅₄ irradiation. Meanwhile, the UV/H₂O₂ and TiO₂ photocatalysis processes removed SF slowly. Interestingly, the electrochemical system produced biodegradable solutions. Furthermore, the electrical energy consumption (EC) for the 100% removal of SF showed that the electrochemical process only spent 0.04 and 0.06% of the EC needed by TiO₂ photocatalysis and UV/H₂O₂, respectively. Therefore, the fast SF degradation, the high biodegradability intensification, and the very low energy consumption evidenced the relative advantages of the electrochemical process for the remediation of water containing safranin T. Finally, to obtain a deeper understanding of SF degradation by the electrochemical system, an analysis of structural transformations was made. It was found that the electrogenerated HOCl initially attacked the central azine and the aromatic amines on SF. Subsequently, aliphatic compounds were formed, which due to their biodegradable character could be completely eliminated by a conventional biological system or discharged into natural media.

Determination of hexavalent chromium (Cr (VI)) in tannery effluent is an important analytical objective for environmental monitoring and assessment. Here, a simple, accurate, and sensitive automated flow injection analysis (FIA) method is proposed in this paper. The procedure is based on a highly selective reaction between Ponceau S and Cr (VI) under acidic condition. The absorbance of the complex compounds was measured using an optical detector at 505 nm. The chemical factors and FIA variables that affect the system were fully discussed and optimized via univariate experimental design. Under the optimal conditions, a linear dynamic range of 0.1–3.0 mg/L with a satisfactory determination coefficient (R ²) of 0.9996 was obtained. The detection limit and relative standard deviation were 0.08 mg/L and 2.27%, respectively. Finally, the method was successfully applied to determine Cr (VI) in field samples of tannery effluent and the results have no significant difference comparing with one official method, indicating this FIA method could be practically promising for determination of Cr (VI) in tannery effluent.

The effect of exogenously applied citric acid (CA) on phytoextraction and antioxidant defense was analyzed using willow species (Salix viminalis, S. alba, and S. matsudana) grown in soil contaminated with cadmium (Cd). Citric acid has been used as a chelating agent for the purpose of accelerating the solubility of Cd in soil and enhancing the phytoextraction of selected plants. Willows were exposed to 6 mg/kg of Cd, following the same with citric acid (20 mM/kg soil). Results revealed a positive effect of citric acid in mobilization of accumulated Cd from roots to shoots and leaves. The addition of citric acid alleviated Cd toxicity by helping plants to overcome oxidative stress, through CA’s chelating properties and the increased activity of antioxidant enzymes. Different protection strategies were evident through modification of activities of antioxidant enzymes such as catalase (CAT), ascorbate-peroxidase (APx), and guaiacol peroxidase (GPx) in young versus mature leaves in plants exposed to Cd. Furthermore, results revealed that addition of citric acid may be beneficial in the reduction of the negative effect of Cd stress on photosynthesis. The efficiency of coupling phytoextraction with the chelating agents represents a good strategy for decreasing damages caused by cadmium and has good potential in decontamination of a polluted environment.