Ventilation and posture effects on inhalation exposures to volatile cleaning ingredients in a simulated domestic worker cleaning environment.

Associations between cleaning chemical exposures and asthma have previously been identified in professional cleaners and healthcare workers. Domestic workers, including housecleaners and caregivers, may receive similar exposures but in residential environments with lower ventilation rates. Study objectives were to compare exposures to occupational exposure limits (OELs), to determine relative contributions from individual cleaning tasks to overall exposure, and to evaluate the effects of ventilation and posture on exposure. Airborne chemical concentrations of sprayed cleaning chemicals (acetic acid or ammonia) were measured during typical cleaning tasks in a simulated residential work environment. Whole-house cleaning exposures (18 cleaning tasks) were measured using integrated personal sampling methods. Individual task exposures were measured with a sampling line attached to subjects' breathing zones, with readings recorded by a ppbRAE monitor, equipped with a photoionization detector calibrated for ammonia and acetic acid measurements. Integrated sampling results indicated no exposures above OELs occurred, but 95th percentile air concentrations would require risk management decisions. Exposure reductions were observed with increased source distance, with lower exposures from mopping floors compared to kneeling. Exposure reductions were also observed for most but not all tasks when ventilation was used, with implications that alternative exposure reduction methods may be needed.

Combination of neural networks and DFT calculations for the comprehensive analysis of FDMPO radical adducts from fast isotropic electron spin resonance spectra.

The 4-hydroxy-5,5-dimethyl-2-trifluoromethylpyrroline-1-oxide (FDMPO) spin trap is very attractive for spin trapping studies due to its high stability and high reaction rates with various free radicals. However, the identification of FDMPO radical adducts is a challenging task since they have very comparable Electron Spin Resonance (ESR) spectra. Here we propose a new method for the analysis and interpretation of the ESR spectra of FDMPO radical adducts. Thus, overlapping ESR spectra were analyzed using computer simulations. As a result, the N- and F-hyperfine splitting constants were obtained. Furthermore, an artificial neural network (ANN) was adopted to identify radical adducts formed during various processes (e.g., Fenton reaction, cleavage of peracetic acid over MnO(2), etc.). The ANN was effective on both "known" FDMPO radical adducts measured in slightly different solvents and not a priori "known" FDMPO radical adducts. Finally, the N- and F-hyperfine splitting constants of ·OH, ·CH(3), ·CH(2)OH, and CH(3)(C═O)O(·) radical adducts of FDMPO were calculated using density functional theory (DFT) at the B3LYP/6-31G(d,p)//B3LYP/6-31G++//B3LYP/EPR-II level of theory to confirm the experimental data.

Direct-Read Fluorescence-Based Measurements of Bioaerosol Exposure in Home Healthcare.

Home healthcare workers (HHCWs) are subjected to variable working environments which increase their risk of being exposed to numerous occupational hazards. One of the potential occupational hazards within the industry includes exposure to bioaerosols. This study aimed to characterize concentrations of three types of bioaerosols utilizing a novel fluorescence-based direct-reading instrument during seven activities that HHCWs typically encounter in patients' homes. Bioaerosols were measured in an indoor residence throughout all seasons in Cincinnati, OH, USA. A fluorescence-based direct-reading instrument (InstaScope, DetectionTek, Boulder, CO, USA) was utilized for all data collection. Total particle counts and concentrations for each particle type, including fluorescent and non-fluorescent particles, were utilized to form the response variable, a normalized concentration calculated as a ratio of concentration during activity to the background concentration. Walking experiments produced a median concentration ratio of 52.45 and 2.77 for pollen and fungi, respectively. Fungi and bacteria produced the highest and lowest median concentration ratios of 17.81 and 1.90 for showering, respectively. Lastly, our current study showed that sleeping activity did not increase bioaerosol concentrations. We further conclude that utilizing direct-reading methods may save time and effort in bioaerosol-exposure assessment.

Efficiency of hydroxyl radical formation and phenol decomposition using UV light emitting diodes and H2O2.

A novel process combining hydrogen peroxide (H2O2) and radiation emitted by ultraviolet light emitting diodes (UV LEDs) has been investigated. The UV LEDs were used as UV-C light sources emitting radiation in the range 257-277 nm for decomposition of the model substance phenol in water. In addition, the effect of H2O2 to phenol molar ratio and initial phenol concentration was examined. Two parameters, the decomposition efficiency of phenol and characterization of hydroxyl radical (HO*) production from H2O2 when illuminated with UV radiation, were selected to provide detailed information regarding the performance of the UV LEDs in the treatment process. A new concept was introduced to characterize and describe the production of HO* radicals produced when photons were absorbed by H2O2 molecules. The phenol decomposition efficiency at the initial concentration of 100 mg/L was the most pronounced at the lowest emitted wavelength. A significant correlation was found between the phenol decomposition efficiency and the photons absorbed by H2O2 (i.e. formation of radicals).

Free radical reaction pathway, thermochemistry of peracetic acid homolysis, and its application for phenol degradation: spectroscopic study and quantum chemistry calculations.

The homolysis of peracetic acid (PAA) as a relevant source of free radicals (e.g., *OH) was studied in detail. Radicals formed as a result of chain radical reactions were detected with electron spin resonance and nuclear magnetic resonance spin trapping techniques and subsequently identified by means of the simulation-based fitting approach. The reaction mechanism, where a hydroxyl radical was a primary product of O-O bond rupture of PAA, was established with a complete assessment of relevant reaction thermochemistry. Total energy analysis of the reaction pathway was performed by electronic structure calculations (ab initio and semiempirical methods) at different levels and basis sets [e.g., HF/6-311G(d), B3LYP/6-31G(d)]. Furthermore, the heterogeneous MnO2/PAA system was tested for the elimination of a model aromatic compound, phenol from aqueous solution. An artificial neural network (ANN) was designed to associate the removal efficiency of phenol with relevant process parameters such as concentrations of both the catalyst and PAA and the reaction time. Results were used to train and test ANN to identify an optimized network structure, which represented the correlations between the operational parameters and removal efficiency of phenol.

Low-frequency ultrasound in biotechnology: state of the art.

The use of low-frequency (10-60 kHz) ultrasound for enhancement of various biotechnological processes has received increased attention over the last decade as a rapid and reagentless method. Recent breakthroughs in sonochemistry have made the ultrasound irradiation procedure more feasible for a broader range of applications. By varying the sonication parameters, various physical, chemical and biological effects can be achieved that can enhance the target processes in accordance with the applied conditions. However, the conditions that have provided beneficial effects of ultrasound on bioprocesses are case-specific and are therefore not widely available in the literature. This review summarizes the current state of the art in areas where sonochemistry could be successfully combined with biotechnology with the aim of enhancing the efficiency of bioprocesses, including biofuel production, bioprocess monitoring, enzyme biocatalysts, biosensors and biosludge treatment.

Optimization of pulp mill effluent treatment with catalytic adsorbent using orthogonal second-order (Box-Behnken) experimental design.

Novel catalytic adsorbent (ruthenium on carbon) was employed for the treatment of pulp mill effluent in the presence of hydrogen peroxide. Mathematical model and optimization of the process regarding the most favorable COD (%), TOC (%) and color (%) removal rates was developed and performed with experimental design taking into account catalytic adsorption process kinetics. As the initial experimental design, 3(3-1) half-fractional factorial design (H-FFD) was accomplished at two levels to study the significance of the main effects, such as catalytic adsorbent (g l(-1)) and hydrogen peroxide (ppm) concentrations using the response surface methodology (RSM). Finally, a four factor-three coded level central composite design (CCD) with 28 runs was performed in order to fit a second-order polynomial model. Validation of the model was accomplished by different criteria including coefficient of determination and the corresponding analysis of variance. The achieved removal rates for TOC (up to 75%), COD (up to 73%) and color (up to 68%) were observed for the defined optimal conditions: 1g l(-1) of ruthenium on carbon, 7 ppm of hydrogen peroxide, pH = 4 and ambient temperature. The proposed method benefited significantly improved TOC, COD and color removal efficiency, regenerability and reusability of the catalytic adsorbent and unaltered initial pH of an effluent in comparison to traditional adsorption or oxidation processes.

The hindering effect of experimental strategies on advancement of alkaline front and electroosmotic flow during electrokinetic lake sediment treatment.

The current study focused on the hindering of alkaline front during electrokinetic copper migration in artificially contaminated lake sediments and the effect of several experimental strategies on electroosmotic flow. Fourteen laboratory scale experiments in triplicates were performed using plastic container where the distance between electrodes was 30 cm at 40 mA, 60 mA and 120 mA electric currents (under density of 0.15 mA cm(-2), 0.23 mA cm(-2) and 0.53 mA cm(-2), respectively) with different Cu concentrations (500 mg kg(-1), 1000 mg kg(-1), 1500 mg kg(-1), 2000 mg kg(-1) and 2500 mg kg(-1)) for 14 days. Tests were conducted with/without electric current and with/without the employment of membranes or barriers. Selected membranes and barriers proved to be efficient in hindering the alkaline front and thus improving copper migration in the sediments. During electrokinetic treatment and the use of the nylon membrane 85% of Cu was removed from sediments. Additionally, 80% and 70% of Cu was removed when cation exchange membrane and filter paper barrier were used. During the electrokinetic treatment Cu as well as the electroosmotic flow was always directed towards the cathode. The highest electroosmotic flow was observed with the lowest (500 mg kg(-1)) Cu concentration. Moreover, the electroosmotic flow and electrical gradient increased with the increase in electric current and was found to be the highest at 120 mA. When there were no membranes, barriers or acid used, severe pH jump was observed at a normalized distance of 0.5-0.6 from the anode. However, when membranes or barriers were employed, there was no pH jump present in the sediments.

Chemical evaluation of potable water in Eastern Qinghai Province, China: human health aspects.

Electric conductivity, pH, COD(Mn), nutrient concentration, chloride and sulfate concentrations, total dissolved sodium, potassium, calcium, magnesium, manganese, iron, cadmium, copper, arsenic, nickel, zinc, chromium and lead were evaluated to clarify concerns about the quality and safety of water used for drinking purposes in Qinghai Province, China. For this purpose, 12 water samples were collected from different villages, Qinghai (Koko Nor) Lake and medicinal springs close to the Town of Pingang during a study visit to China in 2003. The results showed that National Chinese and WHO drinking water standards were exceeded for nutrient concentration (3.2 mg l(-1) of TOT-N and 0.2 mg l(-1) of TOT-P) from Qinghai Lake. The presence of elevated electric conductivity (550 mS m(-1)) in mineral water resort samples should be a matter of a public concern. Also, samples from medicinal springs showed high concentrations of Fe (up to 1.9 mg l(-1)), As (up to 0.1 mg l(-1)) and Ni (0.05 mg l(-1)), which may be detrimental for human health if the water is consumed on a daily basis. The concentrations of Cu, Cd, Cr and Pb did not exceed the National Chinese and WHO drinking water standards, and therefore, water from the sampling area does not pose any significant threat to the consumers' health regarding these metals.

Copper and trace element fractionation in electrokinetically treated methanogenic anaerobic granular sludge.

The effect of electrokinetic treatment (0.15 mA cm(-2)) on the metal fractionation in anaerobic granular sludge artificially contaminated with copper (initial copper concentration 1000 mg kg(-1) wet sludge) was studied. Acidification of the sludge (final pH 4.2 in the sludge bed) with the intention to desorb the copper species bound to the organic/sulfides and residual fractions did not result in an increased mobility, despite the fact that a higher quantity of copper was measured in the more mobile (i.e. exchangeable/carbonate) fractions at final pH 4.2 compared to circum-neutral pH conditions. Also addition of the chelating agent EDTA (Cu2+:EDTA4- ratio 1.2:1) did not enhance the mobility of copper from the organic/sulfides and residual fractions, despite the fact that it induced a reduction of the total copper content of the sludge. The presence of sulfide precipitates likely influences the copper mobilisation from these less mobile fractions, and thus makes EDTA addition ineffective to solubilise copper from the granules.

Visible light activated TiO2/microcrystalline cellulose nanocatalyst to destroy organic contaminants in water.

Hybrid TiO(2)/microcrystalline cellulose (MC) nanophotocatalyst was prepared in situ by a facile and simple synthesis utilizing benign precursors such as MC and TiCl(4). The as-prepared nanocomposite was characterized by XRD, XPS, BET surface area analyzer, UV-vis DRS and TGA. Surface morphology was assessed by the means of SEM and HR-TEM. Statistics-based factorial design (FD) was adopted to investigate the effect of precursors concentrations and therefore to optimize the nanocomposite synthesis through catalytic adsorption of methylene blue (MB) from aqueous solutions. The results indicated that TiO(2)/MC nanocomposites were photocatalytically active in diminishing 40-90% of MB in 4h.

Theoretical and practical aspects of chemical functionalization of carbon nanofibers (CNFs): DFT calculations and adsorption study.

The nitric acid-functionalized commercial carbon nanofibers (CNFs) were comprehensively studied by instrumental (XRD, BET, SEM, TGA) and theoretical (DFT calculations) methods. The detailed surface study revealed the variation in the characteristics of functionalized CNFs, such as a decreased (up to 34%) surface area and impacted structural, electronic and chemical properties. The effects of functional groups were studied by comparison with pristine nanofibers. The results showed that the C-C bond lengths of the modified CNFs varied significantly. Chemical functionalization altered the frontier orbitals of the pristine material, and therefore altered the nature of their interactions with other substances. Moreover, the pristine and modified CNFs were tested for the removal of phenol from aqueous solutions. It was observed that surface modification tuned the adsorption capacity of carbon nanofibers (up to 0.35 mmol g(-1)), whereas original fibers did not demonstrate any adsorption capacity of phenol.

The effect of electrodialytic treatment and Na2H2EDTA addition on methanogenic activity of copper-amended anaerobic granular sludge: treatment costs and energy consumption.

The effect of electrodialytic treatment in terms of a current density, pH and Na(2)H(2)EDTA addition on the methanogenic activity of copper-amended anaerobic granular sludge taken from the UASB reactor from paper mill was evaluated. Moreover, the specific energy consumption and simplified operational and treatment costs were calculated. Addition of Na(2)H(2)EDTA (at pH7.7) to copper-amended sludge resulted in the highest microbial activity (62 mg CH(4)-COD g VSS(-1)day(-1)) suggesting that Na(2)H(2)EDTA decreased the toxic effects of copper on the methanogenic activity of the anaerobic granular sludge. The highest methane production (159 %) was also observed upon Na(2)H(2)EDTA addition and simultaneous electricity application (pH7.7). The energy consumption during the treatment was 560, 840, 1400 and 1680 kW h m(-3) at current densities of 0.23, 0.34, 0.57 and 0.69 mA cm(-2), respectively. This corresponded to a treatment costs in terms of electricity expenditure from 39.2 to 117.6 € per cubic meter of sludge.

Optimisation of electro-Fenton denitrification of a model wastewater using a response surface methodology.

Electro-Fenton denitrification of a model wastewater was studied using platinized titanium electrodes in a batch electrochemical reactor. The model wastewater was prepared from components based on the real aquaculture effluent with nitrate concentrations varying from 200 to 800 mg L(-1). The technical as well as scientific feasibility of the method was assessed by the relationship between the most significant process variables such as various Fenton's reagent to hydrogen peroxide ratios (1:5; 1:20 and 1:50) and current densities (0.17 mA cm(-2), 0.34 mA cm(-2) and 0.69 mA cm(-2)) and their response on denitrification efficiency in terms of nitrate degradation using central composite Box-Behnken experimental design was determined. The goodness of the model was checked by the coefficient of determination R(2) (0.9775), the corresponding analysis of variance P>F and a parity plot. The ANOVA results indicated that the proposed model was significant and therefore can be used to optimize denitrification of a model wastewater. The optimum reaction conditions were found to be 1:20 Fenton's reagent/hydrogen peroxide ratio, 400 mg L(-1) initial nitrate concentration and 0.34 mA cm(-2) current density. Treatment costs in terms of electricity expenditure at 0.17, 0.34 and 0.69 mA cm(-2) was 7.6, 16 and 41.8 euro, respectively, per kilogram of nitrates and 1, 2 and 4 euro, respectively, per cubic meter of wastewater.

Comparative kinetic analysis of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol.

The kinetic study of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol in water was performed to qualitatively assess the effect of ultrasound on the process kinetics. Various kinetic parameters such as the apparent kinetic rate constants, the surface utilization coefficient and activation energy of phenol oxidation over RuI(3) catalyst were investigated. Comparative analysis revealed that the use of ultrasound irradiation reduced the energy barrier of the reaction but had no impact on the reaction pathway. The activation energy for the oxidation of phenol over RuI(3) catalyst in the presence of ultrasound was found to be 13kJmol(-1), which was four times smaller in comparison to the silent oxidation process (57kJmol(-1)). Finally, 'figures-of-merit' was utilized to assess different experimental strategies such as sonolysis alone, H(2)O(2)-enhanced sonolysis and sono-catalytic oxidation of phenol in order to estimate the electric energy consumption based on the kinetic rate constants of the oxidation process.

Visible light induced photobleaching of methylene blue over melamine-doped TiO2 nanocatalyst.

TiO(2) doping with N-rich melamine produced a stable, active and visible light sensitized nanocatalyst that showed a remarkable efficiency towards the photobleaching of a model compound - methylene blue (MB) in aqueous solution. The photobleaching followed a mixed reaction order kinetics with the distinctive induction and acceleration periods.

Electro-Fenton, hydrogenotrophic and Fe2+ ions mediated TOC and nitrate removal from aquaculture system: different experimental strategies.

A number of methods for denitrification were studied including Electro-Fenton method, hydrogenotrophic as well as innovative Fe(2+) mediated denitrification and their technical feasibility in terms of changes in TOC and nitrate concentrations, effect of different Fenton's reagent dosage, current and the effect of the pH was investigated. This study was carried out using tailor made electrodialytic reactor. It was found that the highest TOC removal was achieved at pH 2.2 and 2.4 (77.1% and 97.8%, respectively) at the anode and the lowest accumulation of 33% at pH of 6.2 at the cathode. The highest TOC removal in terms of using different H(2)O(2) concentrations was achieved at 40 mM reaching as high as 97.3%. Regardless experimental strategy, initially nitrates migrated towards the cathode due to the strong hydraulic gradient under the applied electric current. During the course of experiments, nitrates were transported towards the anode where their concentration decreased. The highest nitrate removal was achieved at 0.12 mA cm(-2) electric current density (94.8%) at the anode and a complete removal at the cathode. Hydrogenotrophic denitrification was the highest reaching 92.5%, however, when Fe(2+) ions as electron donor was used for the destruction of nitrates, only 66.6% removal was achieved. Denitrification using only Fe(2+) ions was a factor 1.4 less than using electrically generated hydrogen or a Fenton's reagent.

ESR ST study of hydroxyl radical generation in wet peroxide system catalyzed by heterogeneous ruthenium.

Ru-based catalysts gained popularity because of their applicability for a variety of processes, including carbon monoxide oxidation, wet air catalytic oxidation and wastewater treatment. The focus of a current study was generation of hydroxyl radicals in the wet peroxide system catalyzed by heterogeneous ruthenium, spin-trapped by DEPMPO and DIPPMPO by means of electron spin resonance spin-trapping technique (ESR ST). The mechanism of free radicals formation was proposed via direct cleavage of hydrogen peroxide over ruthenium active sites. The chemical reactions occurring in the system were introduced according to the experimental results. Also, radical production rate was assessed based on concentration changes of species involved in the bulk liquid phase oxidation.