Chemosphere最新文献

As a fast and efficient process, a periodate (PI)-based advanced oxidation process was used to degrade direct red 89 (DR89), wherein hydrogen peroxide (H₂O₂) was employed to activate PI (H₂O₂/PI process) to investigate the effect of operating parameters and mixture composition. The PI was efficiently activated by H₂O₂ to degrade 67% of DR89 within 1 min. Acidic pH was more favorable to high-efficiency degradation than the basic pH; at pH 3 degradation rate was 94.31%, while it was only 20.92% at pH 11. The degradation rates were further enhanced with increasing H₂O₂ and PI dose up to certain optimum values, later it decreased which was dependent upon the amount of hydroxyl (^●OH) and iodyl (IO₃^●) radicals produced. The quenching experiments suggested that IO₃^●, ^●OH, ¹O_2, and O₂^●- are the predominant reactive species during H₂O₂/PI process, while O₂^●- radicals are the primary precursor of other reactive oxygen species. The results of this study suggested that H₂O₂/PI is the efficient and rapid treatment method to degrade persistent organic pollutants (POPs) from polluted wastewater sources.

The effects of a single feeding cycle followed by a continuous aeration phase (AND_C) and a step-feeding cycle followed by intermittent aerobic/idle phases (AND_I) on the production and emission of nitrous oxide (N₂O) from aerobic granular sludge (AGS) from real domestic sewage were studied. Higher N₂O emissions were observed in the AND_I treatment, and 9.2 ± 4.1% of the influent TN was emitted as N₂O, while in the AND_C treatment, 4.6 ± 2.5% of the influent TN was emitted as N₂O. Both strategies were similar for carbon and total phosphorus removal; but AND_I was advantageous for ammonium nitrogen and total nitrogen removal. Regarding the microbial populations associated with N₂O production, genera such as Thauera, a heterotrophic denitrifier, were found to have a relative abundance of 2.1% in AND_C and 3.8% in AND_I. Defluviccocus and Tetrasphaera, organisms capable of denitrification and phosphorus removal, especially the latter, were present in AND_C. Under AND_I conditions, these organisms may have been replaced by fast-growing organisms, such as Thauera. Principal component analysis (PCA) showed that incomplete denitrification was the dominant effect in the AND_C strategy. This may be related to the nitrate and phosphate concentrations and effluent characteristics (low C:N ratio). In the AND_I strategy, incomplete denitrification and low polyhydroxyalkanoate (PHA) consumption were the main effects. This is indicated by the high nitrite and phosphate concentrations. Therefore, according to the PCA results, the combination of the AND_C and AND_I strategies can play a crucial operational role in the dynamics of N₂O production and emission, especially considering that real domestic wastewater was used in the present research.

Many processes can contribute to the attenuation of the frequently detected and toxic herbicides atrazine and metolachlor in surface water, including photodegradation. Multi-element compound-specific isotope analysis has the potential to decipher between these different degradation pathways as Cl is a promising tool for both pathway identification and a sensitive indicator of degradation for both atrazine and metolachlor. In this study, photodegradation experiments of atrazine and metolachlor were conducted under simulated sunlight in buffered solutions (direct photodegradation) and with nitrate (indirect photodegradation by OH radicals) to determine kinetics, transformation products and isotope fractionation for C, N and for the first time Cl. For metolachlor, the C-Cl dual isotope slope (Λ_C/Cl = 0.46 ± 0.19) is identical to previously reported values for hydrolysis and biodegradation in soils, suggesting the same reaction mechanism (C-Cl bond breakage by SN₂ nucleophilic substitution). For atrazine, both direct and indirect photodegradation resulted in a pronounced inverse isotope effect for chlorine (ε_Cl = 6.9 ± 3.3 ‰, and ε_Cl = 2.3 ± 1.2 ‰, respectively), leading to characteristic dual isotope slopes (Λ_C/Cl = -0.49 ± 0.17 and Λ_C/Cl = -0.31 ± 0.10, respectively). These values are distinct from those previously reported for abiotic hydrolysis, biotic hydrolysis and oxidative dealkylation which are all relevant processes in surface water, opening the path for pathway identification in future field studies.

Nematodes are the most diverse and dominant group of marine meiofauna with high potential as bioindicators of the ecological quality status (EcoQS). The present study explores, for the first time, the applicability of the nematode metabarcoding to infer EcoQS index based on the calibration of ecological behaviors of nematodes Amplicon Sequence Variants (ASVs). To achieve this, we analyzed the nematode community in sediment eDNA samples collected in 2018 and 2021 in areas around three offshore oil platforms in the Danish west coast of the North Sea. One training dataset based on eDNA and environmental data from the three platforms in 2021 covering a wide range of environmental gradients has been used as a training dataset to assign the nematodes ASVs to Ecological Groups. These assignments then allowed us to infer the EcoQS both around these three platforms and in an independent dataset (one of the platforms sampled in 2018). The EcoQS inferred from the nema-gAMBI is perfectly in line with the pollution gradient of the platforms. In fact, stations located close to the platforms (i.e., 100 m and 250 m) show a relatively lower EcoQS than those at greater distance (i.e., reference or 3000 m). The nema-gAMBI seems to capture well the EcoQS variability around platforms and correlates well with the environmental parameters (e.g., trace element and hydrocarbon pollution). Indeed, the nema-gAMBI is positively and significantly correlated with the traditional macrofauna-based AMBI. The present proof of concept strongly advocates for the application of the nematode eDNA-based index in the evaluation of EcoQS.

Use of phosphorus (P)-inactivating material to immobilize P released from sediment, typically under anoxic condition, is a method often considered to reduce lake internal P loading for eutrophication control. This study found that immobilizing the released P from sediment induced accumulation of algal-available P (NaHCO₃ and Fe oxide paper strip extractable P) in P-inactivating material which was even higher than those in raw sediment at initial stage (by 29.7% and 85.7%), although algal-available P substantially decreased in sediment after addition of the material and in the separated sediment from the mixtures. Given the possibility of exposing P-inactivating material to phytoplankton systems in overlying water typically during sediment resuspension, the accumulation suggested the potential of the resuspended material changing as P source for phytoplankton growth, increasing the uncertainties of sediment P immobilization method. Future work should focus more on the resuspension characteristics of P-inactivating material and on enhancing the capability of immobilizing algal-available P by the materials during internal P pollution control, especially in shallow lake.

The research focuses on extracting nickel and other valuable elements through oxidative bioleaching from two distinct arsenic-rich ores of varying grades. This process involved utilizing a mix of mesophilic and moderately thermophilic bacteria in shake flasks with different pulp density levels to bio-leach nickeline. Mesophilic bacteria achieved over 99% nickel dissolution from both low- and high-grade ores within 10 and 28 days, respectively, at pulp densities of 0.5% and 1%. In contrast, abiotic control and chemical tests showed significantly lower nickel dissolution rates (approximately 6.9% and 26.1% for low-grade; 10.3% and 45% for high-grade samples). Moderately thermophilic bacteria achieved complete nickel dissolution from the low-grade ore at a 0.5% pulp density, while dissolution from the high-grade ore reached approximately 63%. In comparison, abiotic controls and chemical achieved only 19% and 39% dissolution for the high-grade ore, and 21.9% and 45% for the low-grade ore, respectively. X-ray diffraction (XRD) analysis confirmed the formation of scorodite as a secondary phase due to arsenic solubilization from primary minerals in the presence of iron. Kinetic modelling revealed that the bioleaching of the low-grade ore was predominantly controlled by a mixed reaction mechanism, whereas chemical factors limited the bioleaching rate of the high-grade ore. This research underscores the efficacy of oxidative bioleaching using mixed bacterial cultures and highlights its potential for efficiently extracting nickel and other valuable metals (cobalt and copper) from arsenic-bearing ores under controlled pulp density conditions.

This study evaluated the integration of electrocoagulation into a lab-scale membrane bioreactor (EC-MBR) for treating wastewater from a detergent manufacturing plant. The EC-MBR system achieved a higher chemical oxygen demand (COD) and anionic surfactant removal efficiencies of 95.1% and 99.7% compared to 93.3% and 98.7% in the MBR system, respectively. Sludge volume index and mixed liquor supernatant turbidity revealed superior sludge settling and flocculation ability, respectively, in the EC-MBR system compared to the MBR system. Membrane fouling was less severe in the EC-MBR system, linked to reduced concentrations of soluble microbial products and loosely bond extracellular polymeric substances, especially their protein to carbohydrate ratio, as well as increased particle size in the mixed liquor. Fourier transform infrared spectroscopy (FTIR) analysis indicated that the membrane cake layer was mainly composed of protein and carbohydrate. Scanning electron microscopy (SEM) revealed microbial clusters in the MBR system composed of rod- and oval-shaped bacteria, while the EC-MBR system primarily showed spherical microbial structures. The EC-MBR system demonstrated low energy consumption (1.75 kWh m^-³) and operating costs ($0.55 m^-³), highlighting its efficiency and cost-effectiveness for sustainable wastewater management.

Biodegradation of microplastics (MPs) through microalgal strains would be of eco-friendly approach for significant pollution abatement. Polystyrene (PS) is a major contaminant in the marine environment; however studies on marine microalgal degradation of PS MPs have been very limited. In the present study, six marine microalgal strains viz. Picochlorum maculatum, Dunaliella salina, Amphora sp., Navicula sp., Synechocystis sp. and Limnospira indica were investigated for their ability to degrade PS MPs for the incubation period of 45 days. Results from weight reduction, ATR-FTIR, SEM, and molecular docking analysis confirmed that microalgae formed biofilms on PS MPs, causing structural changes, and laccase-driven enzymatic breakdown. A maximum weight loss of 23.2 ± 0.21% and a minimum of 11.3 ± 0.026% were caused by the colonized microalgae Synechocystis sp. and Amphora sp. respectively. The study indicated that a higher reduction rate was observed in the Synechocystis sp. Treated PS MPs with a rate of 0.0058 g/day and a lower half-life of 119.34 days. SEM analysis showed that microalgae caused pits, erosion, and damage to the PS film. ATR-FTIR confirmed the chemical modifications and proved biodegradation. Laccase enzyme activity was higher in Synechocystis sp., and molecular docking showed the laccase interaction with the derivatives of PS, elucidating the breakdown process. This study highlights the potential of microalgae for eco-friendly microplastic degradation and paves the way for future research on the by-products of this process. Exploring the ecological impact of by-products and optimizing scalable methods can further enhance the sustainability and practical applications of this promising solution.