Regioselective oxidation of tetracycline by permanganate through alternating susceptible moiety and increasing electron donating ability.

Permanganate has attracted much attention in wide range of chemistry and particularly in degradation of environmental pollutants. However, few studies have discussed the feature of regioselective reactivity of permanganate with specific moiety of the target compound. Herein, we studied the reaction between permanganate and tetracycline that is an emerging micropollutant with different species containing several electron-rich groups. The second-order rate constants increased from 6.0 to 9.0 and could be quantitatively modeled by considering the speciation of both reactants, yielding kTC0 = 11.7 (mol/L)-1 sec-1, kTC- = 35.7 (mol/L)-1 sec-1, kTC2- = 43.1 (mol/L)-1 sec-1 for individual reaction channels. Degradation products were then identified as the hydroxylated and demethylated compounds. The result suggested a rate-limiting step of simple hydroxylation at the phenolic and/or alkene moieties, while the demethylation should be caused by the unavoidably formed manganese oxide via single electron oxidation. This is supported by the DFT calculation, indicating the primary oxidation of phenolic group of TC0 with activation barrier of 44.5 kcal/mol and of alkene group of TC- and TC2- with activation barriers of 44.0 and 43.4 kcal/mol, respectively. This is in agreement with the experimental results, implying the alternation of regioselectivity associated with the deprotonation process. The result was further supported by performing the Fukui function and electrostatic potential analysis, reflecting the more probable site and better electron donating tendency beneficial to the permanganate oxidation.

Antimony oxidation and adsorption by in-situ formed biogenic Mn oxide and Fe-Mn oxides.

Antimony (Sb), which can be toxic at relatively low concentrations, may co-exist with Mn(II) and/or Fe(II) in some groundwater and surface water bodies. Here we investigated the potential oxidation and adsorption pathways of Sb (III and V) species in the presence of Mn(II) and Mn-oxidizing bacteria, with or without Fe(II). Batch experiments were conducted to determine the oxidation and adsorption characteristics of Sb species in the presence of biogenic Mn oxides (BMOs), which were formed in-situ via the oxidation of Mn(II) by a Mn-oxidizing bacterium (Pseudomonas sp. QJX-1). Results indicated that Sb(III) ions could be oxidized to Sb(V) ions by BMO, but only Sb(V) originating from Sb(III) oxidation was adsorbed effectively by BMO. Introduced Fe(II) was chemically oxidized to FeOOH, the precipitates of which mixed with BMO to form a new compound, biogenic Fe-Mn oxides (BFMO). The BMO part of the BFMO mainly oxidized and the FeOOH of the BFMO mainly adsorbed the Sb species. In aquatic solutions containing both As(III) and Sb(III), the BFMO that formed in-situ preferentially oxidized Sb over As but adsorbed As more efficiently. Chemical analysis and reverse transcription real-time polymerase chain reaction revealed that the presence of Fe(II), As(III) and Sb(III) accelerated the oxidation of Mn(II) but inhibited the activity of Mn-oxidizing bacteria. These results provide significant insights into the biogeochemical pathways of Sb, Mn(II) in aquatic ecosystems, with or without Fe(II).

As(III) oxidation by active chlorine and subsequent removal of As(V) by Al13 polymer coagulation using a novel dual function reagent.

An electrochemically prepared water treatment reagent containing a high concentration of Al(13) polymer and active chlorine (PACC) showed promising potential for the removal of As(III) due to the combined function of oxidation and coagulation. The results indicated that PACC was effective for As(III) removal through oxidation by the active chlorine and subsequent removal of As(V) by coagulation with the Al(13) polymer. The As(III) was oxidized to As(V) by active chlorine in PACC, with a stoichiometric rate of 0.99 mg Cl(2)/mg As(III). The Al(13) polymer was the most active Al species responsible for As(V) removal in PACC. To meet As drinking water standards the stoichiometric weight ratio of Cl(2)/Al within PACC was 0.09 for the treatment of As(III). Considering the process of As(III) oxidation and As(V) coagulation together, the optimal pH conditions for the removal of As by PACC was within the neutral range, which facilitated the reaction of As(III) with active chlorine and favored the formation of Al hydroxide flocs. The presence of humic acid reduced the As(III) removal efficiency of PACC due to its negative influence on subsequent As(V) coagulation, and disinfection byproduct yields were very low in the presence of insufficient or stoichiometric active chlorine.

Catalyzing denitrification of Paracoccus versutus by immobilized 1,5-dichloroanthraquinone.

The accelerating effect of non-dissolved redox mediator (1,5-dichloroanthraquinone) on the biological denitrification was investigated in this paper using 1,5-dichloroanthraquinone immobilized by calcium alginate (CA) and a heterotrophic denitrification bacterium of Paracoccus versutus (GU111570). The results suggested that the denitrification rate was enhanced 2.1 fold by 25 mmol l(-1) 1,5-dichloroanthraquinone of this study, and a positive correlation was found for the denitrification rate and 1,5-dichloroanthraquinone concentrations from 0 to 25 mmol l(-1). According to the change characteristic of NO(3) (-) and NO(2) (-) during the denitrification process, the tentative accelerating mechanism of the denitrification by redox mediators was put forward, and redox mediator might play the role of reduced cofactors like NADH, N(A)DH and SDH, or the similar ubiquinol/ubiquinone (Q/QH(2)) role during the denitrification process.

Micro-electrode system designed to determine H+ concentration distribution at particle-water interface.

The current understanding of the particle-water interface relies primarily on the use of electric double layer theory (EDL theory), in which the concentration distribution of ions with distance can be evaluated. However, although EDL theory provides a theoretical and mathematical basis, obtaining direct experimental results is also necessary. In this study, an instrument system set with a designed H+ selective micro-electrode was developed for in situ determination at the particle-water interface, and a preliminary investigation of the H+ concentration distribution at the particle-water interface was enabled using data collection at 1 nm/step. The experimental results agree with EDL theory and provide direct evidence to support its general assumptions. The compressible effect of the electric double layer with an increase in ionic strength is verified, and the defined length of the diffusion layer in this investigation is shown to have an approximately inverse proportion to the square root of ionic strength. The rise in H+ concentration near the particle surface is also determined during interactions between trace Fe3+ and particles. Results indicate that the method reported here can be applied to conduct dynamic in situ observations; based on its excellent performance, this innovative instrument system has great potential for interface mechanism research in the water environment.

Acidic permanganate oxidation of sulfamethoxazole by stepwise electron-proton transfer.

Permanganate is a versatile chemical oxidant, and has undergone a dramatic evolution toward deep insight into its reaction mechanism. However, the hydrogen abstraction of the NH bond by permanganate remains unclear. We studied the permanganate oxidation of the emerging micropollutant sulfamethoxazole in acidic aqueous solution. The reaction followed autocatalytic kinetics and demonstrated first-order with respect to each reactant. The presence of HMnO4 accelerated the reaction rate, which was four orders of magnitude higher than that of MnO4-. Based on the identified products, the rate-limiting step was determined to be simple NH bond oxidation by metal-oxo species permanganate. The mechanism was then studied computationally by density functional theory (DFT) using ammonia as the simplest model. Results showed that the NH bond oxidation by MnO4- (32.86 kcal/mol) was a concerted mechanism similar to that of CH bond oxidation, whereas HMnO4 oxidation of the NH bond (10.44 kcal/mol) was a stepwise electron-proton transfer. This reminds us that coordination of Brønsted acid could not only produce the stronger electrophile but also change the reaction mode by avoiding the bond cleavage in electron transfer process.

New Insight into and Characterization of the Aqueous Metal-Enol(ate) Complexes of (Acetonedicarboxylato)copper.

Nearly 50 years have passed since the classic studies by Larson and Lister [Larson D. W.; Lister M. W.Can. J. Chem.1968, 46, 823]and Hay and Leong [Hay R. W.; Leong K. N.J. Chem. Soc. A1971, 0, 3639]on the copper-catalyzed decarboxylation of acetonedicarboxylic acid (H3Acdica). Although the authors laid the foundations for what we know about this reaction; still very little information exists regarding the underlying aqueous metal-enol(ate)s of (acetonedicarboxylato)copper. In this study, UV-visible titrations revealed three pK values, pK [Cu(H2A)], pK [Cu(HA)], and pK [Cu(A)]. We associated the first two with ionization of α-carbon CH2 groups in [CuII(H2Acdica)keto]1+ and [CuII(HAcdica)keto]0 to form unstable metal-enolates, {[CuII(HAcdica)enolate]} and {[CuII(Acdica)enolate]}, which through ß-carbonyl oxygen protonation can form metal-enols [CuII(H2Acdica)enol]1+ and [CuII(HAcdica)enol]0. The square-planar CuII center (electron paramagnetic resonance results) plays a dual role of stabilizing negative electron density at the ß-carbonyl oxygen and as an electron sink in [[CuI(HAcdica)enolate]0]‡ and [[CuI(Acdica)enolate]1-]‡ (confirmed through cyclic voltammetry as two single 1e - transfers). The π → π* transition associated with [CuII(HAcdica)enol]0 was used to determine pK [Cu(A)] (deprotonation of enol OH) and enolization rate constant (stopped-flow spectroscopy) but also exhibited a time-dependent decrease in absorbance (on the order of min-1), suggesting a new method to possibly obtain experimental values for the estimated "k CuL" decarboxylation rate constant of metal-enolate [CuL]1- calculated by Larson and Lister. On the basis of our results, we postulate that decarboxylation takes place primarily through {[CuII(HAcdica)enolate]} and [CuII(HAcdica)enol]0. These results add to our understanding of aqueous metal-enol(ate)s, which contain underlying CuII/I redox chemistry, "active methylenes" and enol tautomers and enolate anions, which play roles in many catalytic reactions of interdisciplinary importance.

Enhanced antimony(V) removal using synergistic effects of Fe hydrolytic flocs and ultrafiltration membrane with sludge discharge evaluation.

The integration of adsorbents with ultrafiltration (UF) membranes is a promising method for alleviating membrane fouling and reducing land use. However, a number of problems have become apparent concerning the granular adsorbents used currently, such as high running cost, high chance of causing membrane surface damage, low in situ chemical cleaning efficiency, etc. Herein, to overcome these disadvantages, loose in situ hydrolyzed flocs were directly injected into the membrane tank, providing strong adsorption ability at low cost. To test the feasibility of this method, the heavy metal pollutant antimony (Sb (V)) in a water plant was chosen at a test case, which is similar to arsenic and difficult to remove. We found that Fe-based flocs integrated with an UF membrane showed a large potential advantage in removing Sb(V), even after running for 110 days. We demonstrated that the observed slow transmembrane pressure development could be ascribed to the loose floc cake layer formed, even though some extracellular polymeric substances were induced during operation. We also found that the floc cake layer was easily removed by washing with feed water or dissolved by in situ chemical cleaning under strongly acidic conditions, and many primary membrane pores were clearly observed. In addition, a relative long sludge discharge interval was feasible for this technology and the effluent quality was good, including the turbidity, chromaticity and iron concentration. Based on the excellent performance, these flocs integrated with UF membranes indeed show potential for application in water treatment.

Antiretroviral treatment reduces very-low-density lipoprotein and intermediate-density lipoprotein apolipoprotein B fractional catabolic rate in human immunodeficiency virus-infected patients with mild dyslipidemia.

The relationship between antiretroviral treatment of HIV infection, body fat distribution, insulin resistance, and very-low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) apolipoprotein-B (apoB) kinetics was investigated in 55 HIV-infected patients taking two nucleoside analogs plus either a protease inhibitor (n = 15) or a nonnucleoside reverse transcriptase inhibitor (n = 25), 15 antiretroviral therapy-naive patients, and 12 HIV-negative controls. Compared with the controls, high-density lipoprotein cholesterol was reduced in all groups (P < 0.01). Plasma triglyceride was increased in patients taking protease inhibitors (P < 0.05). VLDL and IDL apoB fractional catabolic rate (FCR) was lower in all treatment groups (P < 0.05) compared with controls. Trunk fat, VLDL apoB absolute secretion rate, and insulin resistance were not different between groups. Peripheral fat was lower in the treated patients (P < 0.05) and correlated with duration of therapy (r = -0.55; P < 0.001). There was a positive correlation between peripheral fat and VLDL apoB FCR (P = 0.002) and IDL apoB FCR (P = 0.002) and a negative correlation with VLDL apoB pool size, VLDL cholesterol, and triglyceride (P < 0.03; P < 0.01; P < 0.002). These results suggest that mild dyslipidemia resulting from antiretroviral therapy is caused by a decrease in VLDL and IDL apoB FCR, which is associated with a loss of peripheral fat.

Low density lipoprotein apolipoprotein B metabolism in treatment-naive HIV patients and patients on antiretroviral therapy.

BACKGROUND: Dyslipidaemia and lipodystrophy have been described in treated HIV patients and in a small percentage of untreated HIV patients. Lipodystrophy in these patients has been shown to be associated with a lower expression of low density lipoprotein (LDL) receptors. METHODS: We have investigated the effect of antiretroviral treatment with either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) on body fat distribution and LDL apolipoprotein B (apoB) kinetics in 12 HIV-negative controls and 52 HIV-infected patients, including antiretroviral treatment-naive (TN) patients (n=13) and patients taking two nucleoside analogues plus either a PI (n=15) or an NNRTI (n=24). RESULTS: LDL cholesterol was not different between groups. Compared with the controls, LDL apoB absolute synthetic rate (ASR) and fractional catabolic rate (FCR) were lower and residence time (RT) was higher in the PI and NNRTI groups (P<0.05). In the TN patients, LDL ASR was lower (P<0.05) and there was a trend for a lower FCR and higher RT compared with the controls (P=0.07). LDL apoB pool size was greater in the PI group compared with the controls (P<0.05). In the PI group, patients on ritonavir (RTV)-containing regimens had a lower LDL apoB ASR (P=0.009) and a trend to a lower LDL apoB FCR and increased RT compared with non-RTV-containing PI regimens (P=0.05). There was a positive correlation between LDL apoB FCR and limb fat/lean body mass (P=0.004) in all subjects. CONCLUSIONS: Decreased LDL FCR, despite unchanged LDL cholesterol, was demonstrated in both treated and untreated HIV patients. It was more marked with RTV-containing regimens and was associated with reduced limb fat. The increased LDL RT may lead to an increased risk of atherogenesis thus contributing to the risk for cardiovascular disease in these patients.

Reaction of aqueous Cu-Citrate with MnO2 birnessite: characterization of Mn dissolution, oxidation products and surface interactions.

Citric acid, a widespread soil rhizosphere plant/microbe carboxylic acid exudate can easily form chelates with heavy metals, increasing their availability in the environment. When Cu(II) from algal control in water bodies or reservoirs and fungicides, such as the Bordeaux mixture, and citrate interact, solubilization through chelation is a possible outcome. Manganese (hydr)oxides represent a significant portion of the subsurface environment and can affect the fate and transport of chemical species through adsorption and oxidation. This study explores the possible interaction between MnO2 and Cu-Citrate under ambient oxic conditions. The calculated Mn(II) dissolution rates during the initial 1h of reaction followed the series Cu(II)>Cu-Citrate 1:0.5>Cu-Citrate 1:1(oxic)>Citrate>Cu-Citrate 1:1(Anoxic), reinforcing the central role of (complexed or un-complexed) Cu(II) during the initial surface-coordination instead of following the s-shaped auto-catalytic curves of Mn(II) dissolution in citrate solution. The use of capillary electrophoresis allowed the detection of an intermediate Cu(II)Acetonedicarboxylate complex and the oxidation products acetonedicarboxylate, acetoacetate, acetone and acetic acid. The mass balance analysis of Cu-Citrate 1:1 suggests the partial adsorption of Cu-Citrate(ads) and catalytic degradation of acetonedicarboxylate through a MnO2-Cu surface sorbed complex. Lastly, XPS analysis confirmed the MnO2 surface Cu(II) reduction along with an outer-hydration layer at the MnO2 interface, where electron transfer and aquo ligand exchange may lead to the oxidation of Cu-Citrate.

Modification of ultrafiltration membrane with nanoscale zerovalent iron layers for humic acid fouling reduction.

Nanoscale zerovalent iron (NZVI) was layered onto ultrafiltration (UF) membrane surface and tested for antifouling properties using humic acid (HA). Scanning electron microscopy showed that a relatively homogeneous layer was formed across the membrane surface by NZVI particles. Strong adhesion was observed between NZVI and UF membrane used. HA was significantly removed and membrane flux was increased in the presence of NZVI layer. Increased loadings of NZVI onto the membrane surface increased resistance to fouling while slightly reducing the clean water permeability of the membrane. However, the pore size of the layer formed by pristine NZVI was large, resulting in more chances of HA molecules getting to the membrane surface even blocking the membrane pores at the beginning. Membrane loaded with NZVI layer performed much better under acidic conditions. During NZVI synthesis, specific surface area of NZVI particle increased with increasing the ratio of ethanol (Vethanol/Vsolution), which also gradually decreased the average pore size of NZVI layer. As a result, the corresponding membrane flux steadily increased. Additionally, the results for permeate samples under different conditions showed that large molecular weight (MW, >30 kDa) and medium MW HA molecules (3-30 kDa) were removed much faster than those of small MW HA molecules (<3 kDa).

A similarity-based data warehousing environment for medical images.

A core issue of the decision-making process in the medical field is to support the execution of analytical (OLAP) similarity queries over images in data warehousing environments. In this paper, we focus on this issue. We propose imageDWE, a non-conventional data warehousing environment that enables the storage of intrinsic features taken from medical images in a data warehouse and supports OLAP similarity queries over them. To comply with this goal, we introduce the concept of perceptual layer, which is an abstraction used to represent an image dataset according to a given feature descriptor in order to enable similarity search. Based on this concept, we propose the imageDW, an extended data warehouse with dimension tables specifically designed to support one or more perceptual layers. We also detail how to build an imageDW and how to load image data into it. Furthermore, we show how to process OLAP similarity queries composed of a conventional predicate and a similarity search predicate that encompasses the specification of one or more perceptual layers. Moreover, we introduce an index technique to improve the OLAP query processing over images. We carried out performance tests over a data warehouse environment that consolidated medical images from exams of several modalities. The results demonstrated the feasibility and efficiency of our proposed imageDWE to manage images and to process OLAP similarity queries. The results also demonstrated that the use of the proposed index technique guaranteed a great improvement in query processing.

Infrared pupillometry, the Neurological Pupil index and unilateral pupillary dilation after traumatic brain injury: implications for treatment paradigms.

Pupillary dysfunction, a concerning finding in the neurologic examination of the patient with an acute traumatic brain injury often dictates the subsequent treatment paradigm. Patients were monitored closely with an infrared pupillometer, with NPi technology, for acute changes in pupillary function. NPi technology applies a scalar value to pupillary function. A retrospective chart review was performed of traumatic brain injury patients with acute unilateral pupillary dilation, admitted to Legacy Emanuel Medical Center's NeuroTrauma Unit, Portland, OR, and followed as outpatients, between January 2012 and December 2013. Clinical exam findings of pupillary size, NPi scores, and brain Magnetic Resonance Imaging and Computed Tomography images were analyzed. Five traumatic brain injury patients were identified with unilateral pupillary dysfunction with long-term follow-up after the initial injury. Each patient was monitored closely in the trauma bay for neurological deterioration with a pupillometer and the clinical exam. Two patients underwent subsequent intracranial pressure monitoring based on a deteriorating clinical scenario, including consistent abnormal unilateral NPi scores. One patient with consistent abnormal NPi scores and an improved clinical exam did not undergo invasive interventions. Two patients showed early improvement in NPi scores correlating with the normalization of their pupillary reactivity. Anisocoria improved in all patients despite concurrent abnormal NPi scores. Magnetic Resonance Imaging and Computed Tomography imaging studies, with a focus on the third nerve, revealed focal abnormalities consistent with the clinical findings. A unilateral blown pupil and abnormal NPi score in a traumatic brain injury patient are not necessarily indicative of intracranial pressure issues, and must be correlated with the entire clinical scenario, to determine the etiology of the third nerve injury and direct potential therapeutic interventions. Early NPi score normalization suggests pupillary function may improve. We found that NPi scores, as a component of the clinical exam, provide a sensitive, noninvasive and quantitative means of following pupillary function acutely and chronically after a traumatic brain injury.

[Formation of disinfection by-products by Microcystis aeruginosa intracellular organic matter: comparison between chlorination and bromination].

In order to illustrate the effects of released algal organic matter in cyanobacteria blooms on raw water quality and water treatment process, intracellular organic matter (IOM) of Microcystis aeruginosa, which is the dominant species in cyanobacteria blooms, was chosen as a precursor and characterized. In addition, the transformation of IOM and the formation of disinfection byproducts were evaluated at different pH of 6.5, 7.1 and 8.4 after chlorination or bromination, with subsequent correlation analysis. The results indicated that IOM was primarily composed of macromolecular matter, i. e. , the species with relative molecular weight of > 30 x 10(3), constituting 68.8% of dissolved organic carbon (DOC). Fluorescence excitation-emission matrix indicated that IOM was mainly composed of aromatic protein-like matter with an intensity of 92.6 AU x L x mg(-1). After reaction with chlorine or bromine, the intensity of aromatic protein-like peaks decreased sharply by 76.6% - 93.3%, and its reduction correlated well with the formation of trihalomethane (THMs, R2 = 0.81) and haloacetic acid (HAAs, R2 = 0.77). The formation of THMs and HAAs increased with the increase in pH. Compared with chlorine, bromine formed more THMs and HAAs, and tended to form highly halogenated HAAs. However, with increasing pH, the reactivity with IOM between chlorine and bromine was closer, i.e, k(OBr-IOM)/k(OCl-(IOM) < k(HOBr-IOM/k(HOCl-IOM).

Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe-Mn binary oxides: influence of Mn/Fe ratio, pH, Ca2+, and humic acid.

Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe-Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe-Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe-Mn binary oxides. To create Fe-Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe-Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to δ-MnO(2) at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO(2) in the binary oxides. The presence of Ca(2+) enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe-Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe-Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater.

Biological catalyzed denitrification by a functional electropolymerization biocarrier modified by redox mediator.

Electropolymerization biocarriers were prepared by the electropolymerization of polypyrrole (PPy) on an active carbon felt (ACF) electrode using doping anions anthraquinone-2-sulfonate (AQS) or Na(2)SO(4). The functional electropolymerization biocarrier (ACF/PPy/AQS) with AQS was used as an immobilized redox mediator for the denitrification process. The characteristics of the electropolymerization biocarriers were analyzed by scanning electron microscope, elemental analyses, Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The results suggested that the denitrification efficiency increased nearly 1.5-fold with ACF/PPy/AQS (0.04 mmol L(-1) AQS) compared to the control. A linear correlation was found for the k value and the AQS concentration (C(AQS)), which was k=624.71C(AQS)+83.87 (R(2)=0.9893). The ORP value stabilized around -200 mV for the denitrification process with ACF/PPy/AQS, which was -25 mV lower than that with ACF/PPy/Na(2)SO(4). Repeated-batch operations indicated that the denitrification efficiency with ACF/PPy/AQS maintained over 90% of the original value and exhibited better catalytic activity and durability.

The structure activity relationship of non-dissolved redox mediators during azo dye bio-decolorization processes.

Structure activity relationships were elucidated by applying chemical structure, electrochemistry and quantum chemical calculations for non-dissolved redox mediators (RM, quinones) with similar chemical structure. The decolorization efficiencies of acid red B by a Halomonas sp. GYW were enhanced 2.68, 2.58, 1.91 and 1.49 times with 1,5-dichloroanthraquinone, 1,8-dichloroanthraquinone, anthraquinone, and 1,4,5,8-tetrachloroanthraquinone, respectively. The order of oxidation reduction potential (ORP) during the decolorization process with four redox mediators agreed with their order of reduction potential (Ea) from cyclic voltammetry. The decolorization rate (k) with four redox mediators has a linear relation with their Ea values (k=269.05Ea+85.782, R(2)=0.9226). The calculated ρ(r(c)) at the Ring Critical Point (RCP) based on Atoms in Molecules (AIM) and the inductive/resonance effects of the four redox mediators were also consistent with the accelerating effects on the decolorization. These established relationships might to be predictive models and mechanistic explanations for the accelerating decolorization with redox mediator.

Reduction of Cr(VI) by Escherichia coli BL21 in the presence of redox mediators.

Anthraquinone-2,7-disulfonate (2,7-AQDS), anthraquinone-1-sulfonate (α-AQS), anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate (AQDS) and anthraquinone-1,5-disulfonate (1,5-AQDS) were selected as redox mediators for Cr(VI) reduction by Escherichia coli BL21. In the presence of 0.8mmoll(-1) AQS, the Cr(VI) reduction efficiency was 98.5% in 7.5h, whereas it was only 21-34% in the absence of a mediator or in the presence of α-AQS, 1,5-AQDS, AQDS, 2,7-AQDS. A linear correlation, k=0.768C(AQS)+1.5531 (R(2)=0.9935), was found for the reaction constant, k (mg Cr(VI) g(-1) dry cell weight h(-1)) and the AQS concentration (C(AQS)). The Arrhenius equation described the Cr(VI) reduction in the tested temperature range, and the pre-exponential factor A was 13.249mg Cr(VI) g(-1) dry cell weight h(-1),and the activation energy Ea was 28.01kJmol(-1). Glucose was the best carbon sources, and the optimum pH was 6.0. The Cr(VI) reduction rate obtained with AQS is a significant improvement over low conventional anaerobic reduction rates.

Bacterial communities in the sediments of Dianchi Lake, a partitioned eutrophic waterbody in China.

Bacteria play an important role in the decomposition and cycling of a variety of compounds in freshwater aquatic environments, particularly nutrient-rich eutrophic lakes. A unique Chinese eutrophic lake--Dianchi--was selected for study because it has two separate and distinct basins, Caohai with higher organic carbon levels and Waihai with lower organic carbon levels. Sediment bacterial communities were studied in the two basins using samples collected in each season from June 2010 to March 2011. Barcoded pyrosequencing based on the 16 S rRNA gene found that certain common phyla, Proteobacteria, Bacteroidetes, Firmicutes and Chloroflexi, were dominant in the sediments from both basins. However, from the class to genus level, the dominant bacterial groups found in the sediments were distinct between the two basins. Correlation analysis revealed that, among the environmental parameters examined, total organic carbon (TOC) accounted for the greatest proportion of variability in bacterial community. Interestingly, study results suggest that increasing allochthonous organic carbon could enhance bacterial diversity and biomass in the sediment. In addition, analysis of function genes (amoA and nosZ) demonstrated that ammonia-oxidizing bacteria (AOB) were dominant in sediments, with 99% belonging to Nitrosomonas. Denitrifying bacteria were comparatively diverse and were associated with some cultivatable bacteria.