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Ferrihydrite, a nanocrystalline iron (oxyhydr)oxide mineral, is widely distributed in soils and sediments on Earth and is probably an important component and/or precursor of widespread nanophase iron minerals on Mars. Terrestrial ferrihydrite often co‐occurs with amorphous silica and/or contains a certain amount of Si in its structure. However, it remains ambiguous how environmental Si concentration affects the formation‐evolution and structure‐spectral features of ferrihydrite in the Fe(III)‐Si systems. To this end, hydrolysis experiments were carried out for Fe‐Si systems at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0–0.80), followed by characterizing the products detailly. X‐ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Mössbauer spectroscopy, and transmission electron microscopy results showed that at Si/(Fe + Si) molar ratios ≤0.30, the main phase of the products was ferrihydrite, of which the unit cells enlarged, the crystallinity decreased, and the existing state of Fe changed with increased Si contents; at Si/(Fe + Si) molar ratios ≥0.40, ferrihydrite was no longer formed and a novel amorphous Fe‐O‐Si phase was instead obtained, with the excess Si forming amorphous silica. The visible and near‐infrared spectroscopy, the most powerful tool to detect hydrous minerals on the surface of Mars at global or regional scales, showed weakness in identifying ferrihydrite‐like materials obtained in the Fe‐Si systems. Raman spectroscopy can identify ferrihydrite and Si‐containing ferrihydrite but cannot differentiate between them. Mössbauer spectroscopy showed great potential in both identifying and differentiating between ferrihydrite and Si‐containing ferrihydrite, and thus can be used to characterize the poorly ordered iron (oxyhydr)oxides on Mars. Plain Language Summary: On the surface of ancient Mars where liquid water was available, Fe‐Si hydrolysis systems were likely common as a result of the high abundances of Fe and Si in the crust of Mars. By performing hydrolysis experiments of Fe‐Si systems at an unprecedented wide range of Si/(Fe + Si) molar ratios, we found that the hydrolysis products of Fe‐Si systems varied among combinations of ferrihydrite, Si‐containing ferrihydrite, an unknown Fe‐O‐Si phase, and amorphous silica. We also found that the visible and near‐infrared reflectance spectroscopy, the most powerful tool to remotely detect hydrous minerals on the surface of Mars at global and regional scales, showed weakness in identifying ferrihydrite, Si‐containing ferrihydrite, and the novel Fe‐O‐Si phase; Raman can be used to identify ferrihydrite‐like materials but cannot be used to differentiate between ferrihydrite and Si‐containing ferrihydrite; mid‐infrared spectroscopy can differentiate ferrihydrite from Si‐containing ferrihydrite and the novel Fe‐O‐Si phase; Mössbauer spectroscopy (recorded at varied temperatures) provided clues to identifying and further differentiating between ferrihydrite‐like materials and thus holds great potential for detecting Fe/Si‐rich phases on the surface of Mars. Key Points: Hydrolysis experiments of Fe(III)‐Si systems were performed at an unprecedentedly wide range of initial Si/(Fe + Si) molar ratios (0∼0.80)The environmental Si concentration controls the formation and evolution of ferrihydrite in the Fe(III)‐Si systemsMössbauer spectroscopy shows great potential in identifying and differentiating between ferrihydrite‐like materials [ABSTRACT FROM AUTHOR]

Terrestrial microbial communities may take advantage of running waters and runoff to enter rivers and mix with aquatic microorganisms. However, the environmental factors governing the interchange of the microbial community within a watercourse and its surrounding environment and the composition of the resulting community are often underestimated. The present study investigated the effect of flow rate on the mixing of water, soil, sediment and biofilm at four sites along the Lancang River and one branch of the river in winter and summer and, in turn, the resultant changes in the microbial community within each habitat. 16S rRNA gene-based Illumina high-throughput sequencing illustrated that bacterial communities were apparently distinct among biofilm, water, soil and sediment. Biofilms had the lowest richness, Shannon diversity and evenness indices compared with other habitats, and those three indices in all habitats increased significantly from winter to summer. SourceTracker analysis showed a significant coalescence between the bacterial communities of sediment, water and biofilm samples at lower flow rates. Additionally, the proportion of Betaproteobacteria in sediment and biofilms increased with a decrease in flow rate, suggesting the flow rate had a strong impact on microbial community composition and exchange among aquatic habitats. These results were further confirmed by a Mantel test and linear regression analysis. Microbial communities in all samples exhibited a significant but very weak distance–decay relationship (r  = 0.093, P  = 0.024). Turbidity played a much more important role on water bacterial community structure in summer (i.e. rainy season) (BIOENV, r  = 0.92). Together, these results suggest that dispersal is an important factor affecting bacterial community structure in this system. [ABSTRACT FROM AUTHOR]

The minimization and methane production of textile dyeing sludge (TDS) can be simultaneously attained via anaerobic digestion (AD). However, the possible toxicity and complex recalcitrant organic matters involved in limited the hydrolysis of TDS. Therefore, the low-temperature of thermal pretreatment (LTTP) lasting for 1 h at temperatures from 60 to 100 °C was employed to accelerate the hydrolysis and subsequent methane generation of TDS. The results showed that LTTP with temperatures higher than 70 °C obviously improve the AD performance of TDS. Highest accumulative methane production was achieved for 100 °C pretreated TDS and from thermal analysis point of view it was due to the disintegration of some recalcitrant macromolecules in TDS. Nevertheless, 90 °C pretreated TDS did not perform favorable methane yield as expected, attributing to the inhibited acetogenesis as well as the hindered methanogenesis which was simultaneously competed by dye reducer for electrons. [ABSTRACT FROM AUTHOR]

The soluble redox mediator had been employed for catalyzing anaerobic bio-reduction of recalcitrant contaminants such as azo compounds (mainly azo dyes), nitroaromatics, halogenated pollutants and high valence heavy metal, etc. However, the continuous dosing of soluble redox mediators would not only be economically unreasonable, but also have a risk of causing secondary pollution. Therefore the insoluble/immobilized redox mediators were widely studied in last decades trying to overcome above drawbacks. This paper reviewed insoluble redox mediators including carbonaceous (activated carbon, emerging activated carbon fiber, carbon nanotubes, graphene oxide and biochar) and natural materials (humin and henna plant), as well as immobilized redox mediators such as immobilizing model quinones or humic acid on calcium alginate, polyurethane foam, Poly(ethylene terephthalate) fiber, anion exchange resin, etc. The catalyzing performance, characteristics, disadvantages (if any) and lab-scale applications of those insoluble/immobilized RMs were critically discussed, in order to provide reference for the evolvement and promoting further utilizations of novel insoluble/immobilized redox mediators. In addition, future research needed was suggested towards the engineering application of insoluble/immobilized redox mediators. [ABSTRACT FROM AUTHOR]

Under the impact of climate change and human activities, the stationarity of hydrometeorological extreme value series has been losing in many regions, which makes occurrence rules of hydrometeorological extreme events more complicated. In this study, the efficiencies of trend test methods such as Spearman rank correlation test and Mann-Kendall test, as well as the efficiencies of change-point test methods such as moving T test, moving rank sum test, Pettitt test, and sequential Mann-Kendall test were analyzed quantitatively through Monte Carlo simulation. Five representative level stations in the Yangtze River estuary were selected, and the methods listed above were used in the trend and change-point detection of the annual maximum tidal level records in the period of 1950–2008. It was found that obvious rising tendency existed in the annual maximum tidal level series for all these 5 stations, and year 1980 (for 3 stations) and year 1979 (for 2 stations) were statistically significant change-points. Two subseries were divided with the change-point as the dividing point for all these actual series in the stations. Frequency analyses were carried out, respectively, for all of the subseries, and the impact of nonstationary changes in annual maximum tidal levels on probability distribution was evaluated quantitatively. [ABSTRACT FROM AUTHOR]

In this study, a new composite flocculant was prepared by premixing polymeric aluminum ferric sulfate (PAFS) with cationic polyacrylamide (CPAM) to treat textile dye wastewater. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were conducted to investigate the structure and morphology of the PAFS-CPAM. The effects of flocculant dosage, initial pH of textile dye wastewater, and settling time after flocculation on the removal of turbidity and chemical oxygen demand (COD) were examined. The flocculation efficiency of PAFS-CPAM for dye treatment was compared with PAFS, CPAM, PAFS/CPAM (PAFS followed by CPAM), and CPAM/PAFS (CPAM followed by PAFS). The synergy of PAFS and CPAM increased the (Fe-Al)b species of PAFS-CPAM. Treatment with PAFS-CPAM was more effective in removing turbidity and COD than PAFS, CPAM, PAFS/CPAM, and CPAM/PAFS. The turbidity and COD removal rates of textile wastewater were higher than 80 and 90% in the pH range of 5.5 to 8.5, respectively. Furthermore, PAFS-CPAM demonstrated excellent performance in reducing sludge volume after flocculation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40062. [ABSTRACT FROM AUTHOR]

In this research, considering the importance and complexity of the water-level forecast in tidal reach, a case study was done in the tidal reach of the Yangtze River. Through the analysis of the characteristics of water-level variations, tidal harmonic analysis was introduced into tidal reach, which was commonly applied in oceanic water-level forecast. An automatic partial tide selection and optimization pattern was used to calibrate harmonic constants, long-term water-level forecast models were developed for Yanglin, Xuliujing, Tianshenggang, and Jiangyin stage stations, and then the long-term forecast models were used to hindcast historical water-level events at the aforementioned stations. Most of the results were highly accurate, but there were also some occasional significant errors, which could be attributed to the effects of upstream runoff and downstream storm surge. Based on these findings, response functions of water-level forecast error to the variation of upstream runoff and the variation of storm surge were developed, which were used in the real-time correction of the simulation results obtained from the long-term forecast model. The forecast accuracy was evidently improved. These models have already been used in water-level forecast in the tidal reach of the Yangtze River for the construction of two large bridges, and they also have the potential to contribute to water-level forecast in similar tidal reaches of other rivers. [ABSTRACT FROM AUTHOR]

The thin surface soil layer and karst features in karst terrains lead to poor filtration, poor pre-purification and rapid infiltration, so that karst groundwater systems are particularly vulnerable to contamination. Due to its extensive use in past, gamma-hexachlorocyclohexane (γ-HCH) is ubiquitous in various environmental compartments of China, even though it has been prohibited since 1984. However, very little is known about its movement and behavior in special karst system. In this study, a dynamic fugacity model was established for γ-HCH in epikarst system via dividing the karst soil into multiple layers coupled with the physical–chemical properties of γ-HCH. The simulated results in soil profile were in good agreement with the measured values of γ-HCH. The modeled results predict that only 18 g γ-HCH will be left in the studied area in 2020, which is only 0.4% of the largest reserves in 1983, and about 99.99% of γ-HCH will remains in soil. The concentrations of γ-HCH in air, plant and 0–20 cm layer soil in the studied area descended quickly after HCHs was prohibited in 1984, while its concentration in soil layer deeper than 20 cm (deeper soil) increased continuously till 1997. The dominant transfer process of γ-HCH between the adjacent compartments in the studied area was from 0−20 cm layer to the deeper soil. Sensitivity analysis results showed that emission rate, infiltration coefficient, total organic carbon of soil, degradation rate in soil, compartment area and volume were the top six influential parameters for predicting γ-HCH concentration. [ABSTRACT FROM AUTHOR]

Oxidation of acidic dye Eosin Y has been investigated with Fenton process and photo-Fenton process (solar light or artificial light source). With UV–Fenton process and Fenton, 42.5% and 21.3% of dye could be removed from the water, respectively. However, 94.1% of dye was removed in solar-Fenton in 90min. Based on solar-Fenton process, the effect of pH value and the concentration of dye, Fe2+, H2O2 as well as oxalic acid concentration on Eosin Y degradation efficiency were investigated. In 60min, 96% of Eosin Y was degraded when the pH value was 3.5 and the concentration of Fe2+, H2O2 and oxalic acid was 10mol/L, 600mg/L and 300mg/L, respectively. The Eosin Y degradation was dependent on the dye concentration. That is higher Eosin Y concentration resulted in lower degradation efficiency. Under the conditions of pH 3.5, the Eosin Y apparent kinetics equation was −dC/dt =0.000249[Eosin Y]0.78[Fe2+]1.14[H2O2]1.26. Meanwhile, this research also proved that oxalic acid could improve the photocatalytic efficiency in the solar-Fenton process. [Copyright &y& Elsevier]

An anaerobic process, termed the spiral symmetry stream anaerobic bioreactor (SSSAB), had been developed by setting inner components of elliptic plates and gas collection pipes. And our previous study had demonstrated that a SSSAB was more efficient and stable than a same-sized up-flow anaerobic sludge bed (UASB) reactor. This study investigated the optimum treatment efficiency and super-high-rate mechanisms for the SSSAB. The performance with super-high-rate organic loading rate (OLR), volumetric removal rate (VRR) and improved volumetric methane production (VMP) of 361.5 kg COD/(m 3 d), 268.3 kg COD/(m 3 d) and 73.0 m 3 /(m 3 d), respectively, were revealed for a lab-scale SSSAB. The elliptic plates set in the SSSAB could form spiral flow which increased along with the shortening of hydraulic retention time (HRT). The super-high-rate mechanisms were analyzed in terms of biomass, transfer condition around granules and sludge activity. The sludge retention ability in the SSSAB was achieved by the gas entrapment role of elliptic plates and gas collection pipes. The transfer condition around the granular sludge was changed to adapt to the variation of OLR. The rich channels of granules provided a favorable environment for substrate in and product out. The difference of methane productions between the batch test and the reactor operation illustrated that high substrate concentration and especially dramatic mixing condition in the SSSAB were significantly responsible for the super-high efficiency of SSSAB. [ABSTRACT FROM AUTHOR]

Abstract: Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model “redox” reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC–MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ-l-Glutamyl-l-cysteinyl-glycine (GSH) and l-histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites. Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC–MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions. EC–MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances. [Copyright &y& Elsevier]

Abstract: In this paper, results of an experimental study of polymeric phosphate-aluminum chloride (PPAC) as a modified coagulation reagent used to treat wastewater and fractal characteristics of flocs in a sewage treatment process were presented. Operating variables such as P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed, which could influence the coagulation behavior of PPAC were experimentally tested. The evaluation of treatment efficiency was determined by measuring both the reduction of chemical oxygen demand (COD) and residual turbidity. It showed that the optimum removal efficiency was achieved when the P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed were 1.2, 9.0, 0.36g/L and 100rpm respectively. Under optimum conditions, the removal efficiency was 73.5% and 99.5% for COD and turbidity. In addition, radial basis function (RBF) neural network established in this paper was used to predict the flocculation efficiency. The results revealed a promising operational forecasting capability. Furthermore, an inverted optical microscope was used to investigate the fractal structure of flocs formed during coagulation–flocculation. The results showed that under optimum conditions, with the increase of fractal dimension of the flocs, the COD removal efficiency increased while the flocs became denser with large cutter size. [Copyright &y& Elsevier]