Ozone Conditions Research Articles

Prediction of lung function response for populations exposed to a wide range of ozone conditions

Context: A human exposure–response (E–R) model previously demonstrated to accurately predict population mean FEV1 response to ozone exposure has been proposed as the foundation for future risk assessments for ambient ozone.Objective: Fit the original and related models to a larger data set with a wider range of exposure conditions and assess agreement between observed and population mean predicted values.Materials and methods: Existing individual E–R data for 23 human controlled ozone exposure studies with a wide range of concentrations, activity levels, and exposure patterns have been obtained. The data were fit to the original model and to a version of the model that contains a threshold below which no response occurs using a statistical program for fitting nonlinear mixed models.Results: Mean predicted FEV1 responses and the predicted proportions of individuals experiencing FEV1 responses greater than 10, 15, and 20% were found to be in agreement with observed responses across a wide range of exposure conditions for both models. The threshold model, however, provided a better fit to the data than the original, particularly at the lowest levels of exposure.Conclusion: The models identified in this manuscript predict population FEV1 response characteristics for 18–35-year-old individuals exposed to ozone over a wide range of conditions and represent a substantial improvement over earlier E–R models. Because of its better fit to the data, particularly at low levels of exposure, the threshold model is likely to provide more accurate estimates of risk in future risk assessments of ozone-induced FEV1 effects.

Retraction notice to A hybrid CFD framework for fluidized bed ozonation reactors coupling interface tracking and discrete particle methods

highlights An IT-DP framework was successfully developed for the catalytic ozonation of phenol-like pollutants. The effect of physicochemical properties was investigated in terms of bubble diameter and detachment time profiles. The hybrid CFD model handled agreeably the influence of ozone velocity on multiphase flow patterns. graphical a bstract Interstitial flow snapshots of hydrodynamic flow patterns resulting from IT-DP simulations for bubble abstract In this work, a fluidized bed reactor was investigated theoretically and experimentally for the catalytic ozonation of phenol-like pollutants. First, an interface tracking sub-model dealing with the individual motion of ozone bubbles in the continuous phase, and a discrete particle sub-model accounting for the trajectories of the solid particles were embedded accordingly into a hybrid CFD framework. Second, the effect of physicochemical properties including the surface tension and fluid viscosity was thoroughly evaluated at different hydrodynamic flow regimes. Afterwards, the influence of ozone velocity was quan- tified both on the gas and liquid superficial velocities and on the detoxification efficiency of liquid pollu- tants. Here, the interface tracking-discrete particle hybrid model was found to slightly overestimate radial bubble velocities being almost negligible in the center region of the fluidized bed reactor. As the surface tension increased, the mineralization efficiency was considerably lower and became higher when low-viscosity conditions were used for the ozonation of organic pollutants. Finally, the morphological features of interstitial flow maps at different hydrodynamic and reactive catalytic ozonation conditions highlighted the occurrence of bubble plume-like structures which affected the overall decontamination efficiency of phenol-like pollutants within the gas-liquid-solid ozonation reactor.

Water Ozonation with Copper Catalyst for Organic Pollutants Removal

This work presents high-porous honeycomb copper catalyst for organic pollutants removal from water during the ozonation process. This catalyst demonstrates high efficiency in removing target compounds (oxalic and benzoic acids and methylene blue), appropriate stability and resistance to abrasion. Copper catalyst behavior in the ozonation process was investigated. It was found that under ozonation conditions reversible oxidation/reduction of the copper surface layer takes place. In contact with ozone, copper surface can easily be oxidized resulting in formation of copper oxides. As expected, it leads to decomposition of organic substances during ozonation and reduction of copper catalyst surface layer. Copper (II) oxide was also found to be an active catalyst in oxidation of organic pollutants with ozone, but it is not appropriate to use bulk CuO because of its low abrasion resistance. Copper (II) ions that form due to dissolution of catalyst surface layer with participation of the acidic medium in the ozonation process were detected. Pollutants removal efficiency at different pH values was also studied. It was found that catalytic removal of organic pollutants takes place at low pH, as compared to low efficiency of hydroxyl-radical formation at the acidic pH. A possible scheme for organic pollutants removal during ozonation with copper catalyst was proposed.

Modeling of Stomatal Conductance for Estimating Ozone Uptake of Fagus crenata Under Experimentally Enhanced Free-air Ozone Exposure

We examined a performance of the multiplicative stomatal conductance model to estimate the stomatal ozone uptake for Fagus crenata. Parameterization of the model was carried out by in-situ measurements in a free-air ozone exposure experiment. The model performed fairly well under ambient conditions, with low ozone concentration. However, the model overestimated stomatal conductance under enhanced ozone condition due to ozone-induced stomatal closure. A revised model that included a parameter representing ozone-induced stomatal closure showed better estimation of ozone uptake. Neglecting ozone-induced stomatal closure induced a 20 % overestimation of the stomatal uptake of ozone. The ozone-induced stomatal closure was closely related to stomatal ozone uptake rather than accumulated concentrations of ozone exceeding 40 nmol mol−1. Our results suggest that ozone-induced stomatal closure should be implemented to stomatal conductance model for estimating ozone uptake for F. crenata. The implementation will contribute to adequate risk assessments of ozone impacts on F. crenata forests in Japan.

Proteomic analysis of rice response involved in reduction of grain yield under elevated ozone stress

Ozone threat to crop production is increasing, particularly in Asian countries. Although exposure to ozone significantly reduces grain yields in sensitive rice cultivars, it remains unclear what factors cause different sensitivities to ozone and consequent grain yield reduction. To clarify the ozone-induced metabolic changes affecting rice yields, proteomic analyses were conducted of flag leaves in three rice cultivars (Kirara 397, Koshihikari, Takanari) showing various levels of yield and injury response under elevated ozone conditions. Ozone reduced grain yields in Kirara 397 and Takanari, but not in Koshihikari. In ozone treated Kirara 397, Koshihikari, and Takanari, respectively, 31, 18, and 11 proteins were differently expressed. Ozone exposure decreased proteins associated with photosynthesis and glycolysis in Kirara 397, but increased them in Koshihikari. Especially, Kirara 397 showed a remarkable decrease in proteins related to photosynthetic electron transport, suggesting that the elevated ozone suppressed the photosynthetic apparatus in Kirara 397, thereby suppressing yields. However, proteins involved in photosynthesis and other energy metabolism showed no remarkable decrease in Takanari. These results suggest that ozone-induced yield reduction in Takanari results from mechanisms other than those inhibiting the metabolic pathway in photosynthesis.

Effect of ozone pre-treatment on sludge production of aerobic digestion processes

The effect of ozone in a chemical sludge disintegration process was evaluated. Sludge solution chemical oxygen demand (COD), total suspended solids (TSS) and settling were investigated in single and sequential processes. A significant influence of ozone dose on sludge disintegration was observed: ozone was utilised to degrade the soluble organic matter and to destroy cell surfaces and release the cell liquids. For a single ozonation step, we found an optimum ozone dose in the range of 0.008–0.013 g O3/g TSS to give the best COD and TSS removal efficiency. Disintegrated sludge was treated in a sequential process consisting of consecutive ozonation and bio-aeration (i.e. O3 + biological treatment). The tendency was dependent on accumulated ozone, treatment time and operational conditions. An accumulated ozone dose of 0.055 g O3/g TSS in two separate ozonation processes followed by biological treatments led to COD and TSS removal efficiency of 53 and 46.6%, respectively. The removal efficiency was improved by increasing aerobic treatment time and/or by mixing ozonated sludge with non-ozonated sludge. The settling ability of sludge was found to be fast at very low specific ozone doses. An observed tendency was the effect of ozone on cell disintegration and protein liberation. The use of sequential processes improved the settling tendency of sludge.

Issues with Ozone Attainment Methodology for Houston, TX

ABSTRACT To comply with the federal 8-hr ozone standard, the state of Texas is creating a plan for Houston that strictly follows the U.S. Environmental Protection Agency's (EPA) guidance for demonstrating attainment. EPA's attainment guidance methodology has several key assumptions that are demonstrated to not be completely appropriate for the unique observed ozone conditions found in Houston. Houston's ozone violations at monitoring sites are realized as gradual hour-to-hour increases in ozone concentrations, or by large hourly ozone increases that exceed up to 100 parts per billion/hr. Given the time profiles at the violating monitors and those of nearby monitors, these large increases appear to be associated with small parcels of spatially limited plumes of high ozone in a lower background of urban ozone. Some of these high ozone parcels and plumes have been linked to a combination of unique wind conditions and episodic hydrocarbon emission events from the Houston Ship Channel. However, the regulatory air quality model (AQM) does not predict these sharp ozone gradients. Instead, the AQM predicts gradual hourly increases with broad regions of high ozone covering the entire Houston urban core. The AQM model performance can be partly attributed to EPA attainment guidance that prescribes the removal in the baseline model simulation of any episodic hydrocarbon emissions, thereby potentially removing any nontypical causes of ozone exceedances. This paper shows that attainment of all monitors is achieved when days with observed large hourly variability in ozone concentrations are filtered from attainment metrics. Thus, the modeling and observational data support a second unique cause for how ozone is formed in Houston, and the current EPA methodology addresses only one of these two causes. IMPLICATIONS Observational analysis in Houston provides compelling evidence that ozone design values at some surface monitors are dominantly influenced by large hourly changes in ozone concentration that are not predicted by the regulatory model. The use of these models, with current EPA attainment methodology, produces policies that likely overestimate precursor control requirements because only one cause of ozone is functioning in the model. This issue has significant regulatory and economic implications for Houston, especially under lower National Ambient Air Quality Standards. An attainment methodology that recognizes two unique causes for high ozone potentially offers a more reliable means for developing and justifying control policies.

Wastewater treatment of reactive dyestuffs by ozonation in a semi-batch reactor

Water is quickly becoming both scarce and very expensive. Thus, it has become necessary for every industry to examine proposals for the purification and re-use of their wastewater and effluent streams. The Textile industry is one of the largest industrial consumers of water. Predominantly, wastewater from textile industry contains large amounts of dye and dyeing agents, as well as mordant and sizing agents. Current advanced oxidation processes (AOPs) which include ozone, photochemical and photo catalytic oxidation are techniques used for the treatment of such wastewater. Although AOPs are relatively expensive, they appear to be the most likely candidates for full-scale dye house effluent decolouration.The ozonation of wastewater containing four different textile reactive dyestuffs in a semi-batch reactor have been studied. Various ozonation conditions – ozone dose, ozone consumption efficiency, etc. – were explored and studied for these various types of dyestuffs. The mass transfer coefficient of ozone in water and its relationship to the ozone efficiency was studied. Pseudo-first order decolouration rate constants for all dyestuffs were determined experimentally.

Inactivation of Vegetative and Sporulated Bacteria by Dry Gaseous Ozone

Inactivation by gaseous ozone of different types of microorganisms is successfully achieved provided, as is well known, the gaseous phase is strongly humidified. The inactivation mechanisms and species involved in this process are, however, not yet clearly identified. To gain insight, we considered exposure of bacterial spores to dry rather than humidified ozone, a less complex chemical environment. In contrast to most of the published literature, it is shown that, under strict dry ozone conditions, bacterial spores can be inactivated, but to a degree that is largely dependent on the spore type and substrate material. In this case, the O3 molecule is determined to be responsible for the inactivation process through its diffusion into and oxidative action within the spore, as no outer erosion of the spore is detected. With humidified ozone, a higher inactivation efficiency is observed that is most probably related, in part, to the swelling of the spore, which facilitates the diffusion of oxidative species within it and up to the core; besides O3, these oxidative agents stem from the interaction of O3 with H2O, which in the end leads to a heavily damaged spore structure, in contrast to dry-ozone exposure where the spore integrity is maintained.

The role of radical and molecular reactions in the processes of ozonization of aqueous solutions of non-dissociating compounds

A theoretical approach to determining regions where ozonation proceeds by radical and molecular mechanisms is proposed. Ozonation of aqueous solutions of non-dissociating substances in open and closed reactors is considered. The effect of the values of the rate constants of reactions between the substrate and ozone, OH radicals, and O− ions, as well as that of the conditions of ozonation (pH of the solution, concentration of the reagents, and so on) on the role of radical and molecular reactions in the ozonation of chemical compounds is analyzed.

Photolysis of methyl-parathion thin films: Products, kinetics and quantum yields under different atmospheric conditions

The present study focuses on the photodegradation of methyl-parathion thin films, an organophosphate insecticide, under different atmospheric conditions. The latter include nitrogenated, oxygenated and ozonated atmospheres, under low and high relative humidity conditions. Addition of oxygen to the atmospheric mixture did not seem to affect the reaction rates and quantum yields. Relative humidity affect was minor, with a small enhancement in reaction rate under 254 nm radiation. The addition of ozone (to either dry or humid atmosphere), at all concentrations tested, largely enhanced degradation rates. In the absence of ozone, the obtained quantum yields for photolysis of methyl-parathion thin films under 254 and 313 nm were 0.024 ± 0.007 and 0.012 ± 0.005, respectively. These values are higher than the values previously reported for solutions of methanol and water. Although the presence of molecular oxygen and water vapors did not seem to affect much the reaction rates, it did have a certain effect on the resulted products. More polar products were obtained under oxygenated and ozonated atmospheres, as well as dimers under ozone conditions. The reaction on thin films has yielded more toxic products than usually found in solutions, adding alkylphosphate esters in addition to the oxons formed normally.

Kinetics of inactivation of Pseudomonas aeruginosa in aqueous solutions by ozone aeration

The effect of ozonation on the disinfection of Gram-negative strain, Pseudomonas aeruginosa was investigated as a function of time. Ozone was generated in situ using corona discharge method, with ozone concentrations ranging from (0.29–9.84) × 10− 5 moles L− 1. The microbial inactivation kinetics followed pseudo–first-order kinetics under excess concentration conditions of ozone. With over all second-order constant, k = (4.02 ± 0.20) × 104 M− 1 min− 1, the reaction rate had first-order dependence both on the microbial count and ozone. The influence of temperature and pH on the ozone initiated disinfection of the microbe was also investigated. Molecular ozone is found more effective in disinfection than hydroxyl radicals. Probable mechanism for antimicrobial power of ozone in water systems is discussed. The ozone aeration decreased the biochemical oxygen demand (BOD) value of natural and microbe spiked waters significantly.

Ozone-assisted photocatalytic oxidation of gaseous acetaldehyde on TiO 2/H-ZSM-5 catalysts

TiO 2/H-ZSM-5 catalysts were prepared by impregnation with different amount of TiO 2 loading and calcination at various temperatures. The catalysts were characterized by X-ray diffraction (XRD), ultraviolet and visible spectroscopy (UV–vis) and BET specific surface area. It was demonstrated that the anatase TiO 2 retained stable on H-ZSM-5 after heat treatment even at 700 °C. The activities of samples were investigated under the various conditions of UV, ozone and UV-ozone, respectively by the comparison of acetaldehyde degradation. It was found that the photocatalysis combined with ozonation promoted the acetaldehyde degradation. TiO 2/H-ZSM-5 catalysts were superior to simple TiO 2 and H-ZSM-5 with respect to the ozone-assisted photocatalytic oxidation of gaseous acetaldehyde, and the activity of the catalyst TiO 2/H-ZSM-5 (TiO 2:H-ZSM-5 = 2:10) is the highest one among all those prepared samples. The improvement was attributed to the synergetic effect among adsorption, ozonation and catalytic reaction.

Reaction pathways of glucose oxidation by ozone under acidic conditions

The ozonation of d-glucose-1- 13C, 2- 13C, and 6- 13C was carried out at pH 2.5 in a semi-batch reactor at room temperature. The products present in the liquid phase were analyzed by GC–MS, HPAEC-PAD, and 13C NMR spectroscopy. Common oxidation products of glucose have also been submitted to identical ozonation conditions. For the first time, a pentaric acid was identified and its formation quantitatively correlated to the loss of C-6 of glucose in the form of carbon dioxide. Potential mechanisms for the formation of this pentaric acid are discussed. The well-accepted pathway involving the anomeric position in glucose, gluconic acid, arabinose, and carbon dioxide is reinvestigated. The origin of small molecules such as tartaric, erythronic, and oxalic acids is clarified. Finally, new reaction pathways and tentative mechanisms consistent with the formation of ketoaldonic acids and smaller acids are proposed.

Remediation of lignin and its derivatives from pulp and paper industry wastewater by the combination of chemical precipitation and ozonation

In the present work the degradation of the lignin and its derivatives in the residual water of a paper industry by simple ozonation was investigated. The remediation of lignin was realized using the combination of the pre-treatment with chemical precipitation, using concentrated sulfuric acid (97.1%) at the pH 1 and 3, and of the simple ozonation of the filtered residual water at the pH 1, 3, 8 and 12. Since the high residues content (the initial chemical oxygen demand (COD) is 70,000 mg/L) in the experiments the diluted samples (1:10) were used. The previous precipitation has showed a significant effect on the reduction of the COD (77%) and color (96.1%). The sludge precipitated contents sulfolignin, which in the reaction with sulfuric acid was formed. In ozonation of the filtered residual water during 25 min at the pH 1, 3, 8 and 12 the follows by-products were formed: fumaric, maleic, malonic and formic acids. The biodegradability of the treated water in ozonation increases up 0.067–0.29. The effect of the precipitation and the ozonation conditions on the decolorization kinetics was evaluated.

Improvement of nutrient removal and phosphorus recovery in the anaerobic/oxic/anoxic process combined with sludge ozonation and phosphorus adsorption

The effects of ozonation conditions on the performance of a continuous anaerobic/oxic/anoxic (A/O/A) process with sludge ozonation and phosphorus adsorption were investigated. In this system, excess sludge was ozonated by microbubble ozonation, and then the supernatant of the ozonated sludge was flowed into a phosphorus adsorption column packed with zirconium-ferrite adsorbent. The effluent from the column and the settlings of the ozonated sludge were recirculated in the A/O/A process. Long-term operation of a lab-scale system treating rural wastewater showed that ozonation affected not only the sludge reduction efficiency but also the nitrogen removal efficiency. When the amount of sludge to be ozonated was set at 16% of total MLSS per day, no excess sludge was withdrawn, but the nitrogen removal efficiency was deteriorated. Decreasing the amount of sludge to be ozonated (to 9.4% of total MLSS per day) resulted in efficient nitrogen removal, but the MLSS concentration increased slightly. Phosphorus accumulated in the sludge was re-solubilized by ozonation, and a large part of the solubilized phosphorus consisted of Pi. Almost all Pi was recovered in the phosphorus adsorption column.

Secondary organic aerosol formation from multiphase oxidation of limonene by ozone: mechanistic constraints via two-dimensional heteronuclear NMR spectroscopy

Because it is doubly unsaturated, gaseous limonene and ozone reactions exhibit considerable potential for not only a large quantity of secondary organic aerosol (SOA), but also a diverse and complicated product mixture influenced by reactant conditions. We explore the chemistry of limonene ozonolysis and provide evidence that under low-NOx conditions, the endocyclic double bond is oxidized in the gas phase, while under excess ozone conditions, the residual exocyclic double bond in condensed-phase products is heterogeneously oxidized by ozone. We use regular and multinuclear-multidimensional NMR spectroscopy, in particular 1D 1H-NMR, 1H,1H-COSY correlation spectroscopy, and 1H,13C-HSQC (heteronuclear single quantum coherence). For structural assignments we simulate 1H and 13C NMR spectra with ACDLabs online, relying representative products consistent with the postulated reaction mechanism. The 1-D 1H-NMR data allow us to quantify the extent to which the residual unsaturation is oxidized with rising ozone, confirming our hypothesis that the residual unsaturation is oxidized via heterogeneous uptake of ozone to fresh SOA particles.

Influence of ozonation on the in vitro mutagenic and toxic potential of secondary effluents

Reclamation of municipal effluents by advanced treatment processes is an attractive perspective for facing certain water shortage problems. However, the application of tertiary techniques should be thoroughly examined for their potential hazardous effects. Ozonation is an efficient chemical oxidation method, often used in wastewater reclamation, which may result in by-products that may alter the toxic and mutagenic properties of effluents. In this study, Ames test and Microtox test were used for the evaluation of ozonation efficiency to upgrade secondary effluents quality. In general, the toxic response and mutagenic effect without metabolic activation of test species were influenced mainly by the ozone dose and ozonation duration, whereas the mutagenic effect with metabolic activation was influenced mainly by ozone dose, indicating that ozone conditions strongly affect the formation of by-products. In most cases, the toxicity was increased and reached up to 100% (in relation to that of secondary effluent) after ozonation with 8.0 mg O 3/L for 5 min. On the contrary, in most cases the mutagenic activity towards strain TA98 without metabolic activation was reduced, when ozone dose and contact time increased. However, the mutagenicity was also increased after ozonation at low ozone doses and for contact times less than 5 min. The mutagenic activity of treated effluents towards strain TA98 with metabolic activation remained about the same or was reduced, compared to that of secondary effluent, and was even eliminated after ozonation with 8.0 mg O 3/L for contact times higher than 5 min.

Physico‐Chemical Characterization of Sesame Oil Derivatives

Ozone treatment of commercially available vegetable oils gives rise to the formation of chemical species that are responsible for the therapeutic properties of ozonated oil derivatives in dermatological diseases. In the last years, these products have been successfully used as a topical disinfectant in a number of serious skin affections. The medical application of empirically prepared ozonated oil has yielded striking improvements with unexpected and rapid healing, compelling us to begin a long-range study aiming first to define the main characteristics of the most common ozonated vegetable oils, about which there is usually no medical consensus because of the lack of standardization of their technological parameters. Sesame oil was selected because of its great amount of polyunsaturated acyl groups, as well as natural antioxidants. Moreover, we have determined the kinetics and optimal conditions of ozonation (e.g., ozone concentrations, time of exposure, temperature) for obtaining an ozonated oil characterized by well-established technological and physico-chemical properties, namely an accurate peroxide value determination. On the basis of the results, we have gained an understanding of the modifications of the vegetable oils during the ozonation process.

Optimization of ozone treatment of fresh-cut green leaf lettuce

The optimization of ozone treatment for fresh-cut green leaf lettuce was studied to determine the effects of ozone concentration (0.5–4.5 ppm) and exposure time (0.5–3.5 min) on Listeria monocytogenes counts and the overall visual quality of lettuce. Prior to the optimization study, the effect of temperature on the efficacy of ozone treatment was evaluated in the range of 10–26 °C. No significant effect of temperature on the efficacy of ozone treatment was observed. The quality and safety of lettuce samples treated at the determined optimum ozonation condition (2 ppm) were compared with the chlorinated water (100 ppm), organic acid (0.25 g/100 g citric acid plus 0.50 g/100 g ascorbic acid), and water treatments applied at 10 °C for 2 min. Samples were stored at 4 °C for 12 days. Analysis include aerobic mesophilic count, Enterobactericeae, psychrotrophic bacteria, vitamin C, β-carotene, and sensory quality. Ozone treatment was found to be better than the chlorine and organic acid treatments in maintaining the sensory quality.