Tracking and analysis of DBP precursors' properties by fluorescence spectrometry of dissolved organic matter.

Disinfection by-products (DBPs) play a significant role in human health. Identification of the precursor of DBPs, which constitutes dissolved organic matter (DOM), can help optimize the processes in a drinking water treatment plant (DWTP). This is very important for obtaining more safe water. In this context, a one-year study was performed in a DWTP. Fluorescence spectra of DOM were quantified for determining DOM composition and properties, and the corresponding DBPs formation was analyzed. Hydrophobic neutral and acidic compounds were found to be the two predominant substances forming DBPs, which also were dominant in the DOM. Coagulation and sedimentation were not effective in DOM elimination. Besides, sand filtration caused organic compounds to increase by 14.8% on average, especially 28.59% for aromatic protein II and 18.7% for soluble microbial product-like compounds, which was due to metabolism by microorganisms present in the filter. Carbonaceous DBPs were elevated from 34.8 µg/L in source water to 42.5 µg/L in effluent, along with organic compounds increasing in filtration, and nitrogenous DBPs were under detection in winter. All DBPs appeared at a high level in summer. Accordingly, enhanced coagulation process and measures that can avoid the release of organic compounds during filtration have been suggested. As the source water was rarely affected by human activities in the study area and owing to the wide use of traditional treatment process, the data of this research can be regarded as environmental background values and the results are considered as a significant reference.

Mechanisms for ·[Formula: see text] and ·OH Production on Flowerlike BiVO4 Photocatalysis Based on Electron Spin Resonance.

Many studies have focused on the use of BiVO4 as a photocatalyst, but few have investigated the production of free radicals during the photocatalytic process. Following synthesis of flowerlike BiVO4 and characterization by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) Scanning electron microscopy (EDX), UV-Vis and XPS, we successfully prepared BiVO4. Then we used electron spin resonance (ESR) to determine the production and degradation of individual active free radicals, including the superoxide radical (·[Formula: see text]) and the hydroxyl radical (·OH). In the first experiment, we used ESR to detect the signals of free radicals (·[Formula: see text] and ·OH) under varying oxygen conditions. The results shown that in addition to production by ·[Formula: see text], ·OH could also be produced by oxidation of h+ to OH-. In the next experiment, we detected ·OH under varying pH to identify the result of the first experiment, and found that signal intensities increased with increasing pH, indicating the mechanism for ·OH production. Finally, we conducted a trapping experiment to examine free radical degradation mechanisms. We identified ·OH and h+ as the main active free radicals and showed the complete production about ·OH. These results improve current knowledge of free radical production mechanisms, which can be used to enhance the photocatalytic performance of BiVO4.

Synthesis of Reduced Grapheme Oxide as A Platform for loading ß-NaYF4:Ho3+@TiO2Based on An Advanced Visible Light-Driven Photocatalyst.

In this paper a novel visible light-driven ternary compound photocatalyst (ß-NaYF4:Ho3+@TiO2-rGO) was synthesized using a three-step approach. This photocatalyst was characterized using X-ray diffraction, Raman scattering spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence spectrometries, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller surface area measurement, electron spin resonance, three-dimensional fluorescence spectroscopy, and photoelectrochemical properties. Such proposed photocatalyst can absorb 450 nm visible light while emit 290 nm ultraviolet light, so as to realize the visible light-driven photocatalysis of TiO2. In addition, as this tenary compound photocatalyst enjoys effecitve capacity of charge separation, superior durability, and sound adsorb ability of RhB, it can lead to the red shift of wavelength of absorbed light. This novel tenary photocatalyst can reach decomposition rate of RhB as high as 92% after 10 h of irradiation by visible-light Xe lamp. Compared with the blank experiment, the efficiency was significantly improved. Recycle experiments showed that theß-NaYF4:Ho3+@TiO2-rGOcomposites still presented significant photocatalytic activity after four successive cycles. Finally, we investigated visible-light-responsive photocatalytic mechanism of the ß-NaYF4:Ho3+@TiO2-rGO composites. It is of great significance to design an effective solar light-driven photocatalysis in promoting environmental protection.

The Synthesis of a Core-Shell Photocatalyst Material YF3:Ho3+@TiO2 and Investigation of Its Photocatalytic Properties.

In this paper, YF3:Ho3+@TiO2 core-shell nanomaterials were prepared by hydrolysis of tetra-n-butyl titanate (TBOT) using polyvinylpyrrolidone K-30 (PVP) as the coupling agent. Characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) under TEM, X-ray photoelectron spectroscopy (XPS), fluorescence spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance (ESR) were used to characterize the properties and working mechanism of the prepared photocatalyst material. They indicated that the core phase YF3 nanoparticles were successfully coated with a TiO2 shell and the length of the composite was roughly 100 nm. The Ho3+ single-doped YF3:Ho3+@TiO2 displayed strong visible absorption peaks with wavelengths of 450, 537, and 644 nm, respectively. By selecting these three peaks as excitation wavelengths, we could observe 288 nm (5D4→5I8) ultraviolet emission, which confirmed that there was indeed an energy transfer from YF3:Ho3+ to anatase TiO2. In addition, this paper investigated the influences of different TBOT dosages on photocatalysis performance of the as-prepared photocatalyst material. Results showed that the YF3:Ho3+@TiO2 core-shell nanomaterial was an advanced visible-light-driven catalyst, which decomposed approximately 67% of rhodamine b (RhB) and 34.6% of phenol after 10 h of photocatalysis reaction. Compared with the blank experiment, the photocatalysis efficiency was significantly improved. Finally, the visible-light-responsive photocatalytic mechanism of YF3:Ho3+@TiO2 core-shell materials and the influencing factors of photocatalytic degradation were investigated to study the apparent kinetics, which provides a theoretical basis for improving the structural design and functions of this new type of catalytic material.

Preparation of a Microspherical Silver-Reduced Graphene Oxide-Bismuth Vanadate Composite and Evaluation of Its Photocatalytic Activity.

A novel Ag-reduced graphene oxide (rGO)-bismuth vanadate (BiVO4) (AgGB) ternary composite was successfully synthesized via a one-step method. The prepared composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET) surface area measurement, Raman scattering spectroscopy, and ultraviolet-visible diffuse-reflection spectroscopy (UV-vis DRS). The results showed that bulk monoclinic needle-like BiVO4 and Ag nanoparticles with a diameter of approximately 40 nm formed microspheres (diameter, 5-8 µm) with a uniform size distribution that could be loaded on rGO sheets to facilitate the transport of electrons photogenerated in BiVO4, thereby reducing the rate of recombination of photogenerated charge carriers in the coupled AgGB composite system. Ag nanoparticles were dispersed on the surface of the rGO sheets, which exhibited a localized surface plasmon resonance phenomenon and enhanced visible light absorption. The removal efficiency of rhodamine B dye by AgGB (80.2%) was much higher than that of pure BiVO4 (51.6%) and rGO-BiVO4 (58.3%) under visible light irradiation. Recycle experiments showed that the AgGB composite still presented significant photocatalytic activity after five successive cycles. Finally, we propose a possible pathway and mechanism for the photocatalytic degradation of rhodamine B dye using the composite photocatalyst under visible light irradiation.

Distribution of asthma by occupation: Washington State behavioral risk factor surveillance system data, 2006-2009.

OBJECTIVE: To estimate the prevalence of asthma in workers by occupation in Washington State. METHODS: Data from the 2006-2009 Behavioral Risk Factor Surveillance System (BRFSS) and the BRFSS Asthma Call-Back Survey (ACBS) in Washington State (WA) were analyzed. Using state-added and coded Industry and Occupation questions, we calculated prevalence ratios (PRs) for 19 occupational groups. RESULTS: Of the 41,935 respondents who were currently employed during 2006-2009, the prevalence of current asthma was 8.1% [95% confidence interval (CI) 7.8-8.5%] When compared with the reference group of executive, administration and managerial occupations, three occupational groups had significantly (p < 0.05) higher PRs of current asthma: "Teachers, all levels, and Counselors' (PR 1.3, 95% CI 1.1-1. 6%); 'Administrative Support, including Clerical" (PR 1. 5, 95% CI 1.2-1.9%); and "Other Health Services" (PR 1.5, 95% CI 1.2-1.9). Half of the 2511 ACBS respondent workers (55.1%) indicated that they believed exposure at work had caused or worsened their asthma, but only 10.7% had ever spoken with a health care professional about their asthma being work related. CONCLUSIONS: Some occupations have a higher prevalence of current asthma than other occupations. The systematic collection of industry and occupation data can help identify worker populations with a high burden of asthma and can be used to target disease prevention efforts as well as to aid clinician recognition and treatment. Workers indicated that work-related asthma exposures are not discussed with their health care provider and this communication gap has implications for asthma management.

Antibiofilm activity of Bacillus pumilus SW9 against initial biofouling on microfiltration membranes.

Membrane biofouling, resulting from biofilm formation on the membrane, has become the main obstacle hindering wider application of membrane technology. Initial biofouling proves to be crucial which involves early stages of microbial adhesion and biofilm formation. Biological control of microbial attachment seems to be a promising strategy due to its high efficiency and eco-friendliness. The present study investigated the effects of a bacterium Bacillus pumilus SW9 on controlling the initial fouling formed by four target bacterial strains which were pioneer species responsible for biofouling in membrane bioreactors, using microfiltration membranes as the abiotic surfaces. The results suggested that strain SW9 exhibited excellent antibiofilm activity by decreasing the attached biomass of target strains. The production of extracellular polysaccharides and proteins by four target strains was also reduced. A distinct improvement of permeate flux in dead-end filtration systems was achieved when introducing strain SW9 to microfiltration experiments. Scanning electron microscopy and confocal laser scanning microscopy were performed to further ascertain significant changes of the biofouling layers. A link between biofilm inhibition and initial biofouling mitigation was thus provided, suggesting an alternatively potential way to control membrane biofouling through bacterial interactions.

Characterization, DBPs formation, and mutagenicity of different organic matter fractions in two source waters.

Dissolved organic matters (DOM) are critical in the formation of the mutagenic disinfection byproducts (DBPs). In this study, five DOM fractions were isolated and investigated from a contaminated river and a clean reservoir source waters using resin adsorption. The DOM fractions were characterized with excitation-emission matrix, and several typical DBPs formation potentials and the mutagenicity of each DOM fraction were measured. Among these fractions, hydrophobic neutrals (HON), hydrophilic acids (HIA) and hydrophilic bases (HIB) generated the highest carbon-containing DBPs in the river source water, as did HIB and hydrophobic bases (HOB) in reservoir water. Hydrophobic acids (HOA), HON, and HIA were the three most important fractions forming nitrogen-containing DBPs. Following chlorination, the mutagenicity of HON, HIA, HOA and HIB was 1503, 626, 422 and 116 ng 4-NQO/mg DOC in river water, respectively. Only HIA and HOA were mutagenic with 85 and 10 ng 4-NQO/mg DOC in reservoir water, respectively. The soluble microbial products like substances and aromatic proteins contributed significantly to the mutagenicity of river water; whereas the humic acid-like and fulvic acid-like substances were the primary contributors to the mutagenicity of reservoir water.

Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light.

In this study, Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst was prepared via a sol-gel method, and Fe(3)O(4) particles were used as the core of the colloid. Diffraction peaks of Fe(3)O(4) crystals are not found by XRD characterization, indicating that Fe(3)O(4) particles are well encapsulated by SiO(2). FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe(3)O(4) loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe(3)O(4)/SiO(2)/TiO(2) photocatalyst, whereas photocatalysts modified by Fe(3)O(4)/SiO(2) present excellent visible light absorption performance and photocatalytic activity, especially when the Fe(3)O(4) loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe(3)O(4)/SiO(2)/TiO(2) has the best photocatalytic activity. The best moisture content of soil is 30%~50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm(2) or above 10 mW/cm(2), but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm(2) to 10 mW/cm(2).

Renal transplant in patients with Alport's syndrome.

We evaluated 52 renal grafts transplanted into 41 patients with a pretransplantation diagnosis of Alport's syndrome. Overall 1-, 5-, and 10-year patient and graft survival rates were 95.1%, 90.2%, and 80.5% and 86.8%, 66%, and 45.3%, respectively. Although 14% of renal graft biopsy specimens examined with immunofluorescent microscopy showed linear glomerular basement membrane (GBM) immunoglobulin G deposits, only 1 of 41 patients (2.4%) or 52 grafts (1.9%) developed posttransplantation anti-GBM disease. The incidence of anti-GBM disease was 3.1% (1 of 32 patients) in a subgroup of male transplant recipients. Our analysis suggests that the incidence of anti-GBM disease in transplant recipients with Alport's syndrome is less than previously reported. In addition, it does not appear that HLA-DR alleles, which predispose to the development of anti-GBM disease in native kidneys, have a role in transplant recipients with Alport's syndrome posttransplantation. However, immunosuppression level may have a pathophysiological role in the development of anti-GBM disease. The majority of grafts in transplant recipients with Alport's syndrome failed because of chronic allograft nephropathy (69% of grafts) and acute rejection (22% of grafts). A history of previous acute rejection was the only factor that significantly affected graft outcome.