O3 Dose Research Articles

Treatability and Kinetic Analysis of BPA-containing Wastewater by Catalytic Ozone Processes Using ZnSO4 and ZnO Catalysts

ABSTRACT BPA (Bisphenol-A) is an organic colorless crystalline synthetic compound with the chemical formula of (CH3)–C–(C6H4-OH)2. The chemical structure of BPA consists of two methyl functional groups which are connected by a bridge to the phenol rings. The purpose of this study is to investigate the treatability of containing BPA wastewater using by homogeneous (ZnSO4 catalyst) and heterogeneous (ZnO catalyst) catalytic ozone processes (COPs). The BPA removals of ZnO catalyst COP method and ZnSO4 catalyst COP methods were compared and using the ZnO catalyst COP process gave better results than the ZnSO4 catalyst COP process. For the BPA removals, the experimental parameters including pH, catalysts dose, ozone dose, and reaction time parameters were optimized by changing one parameter at a time. As a result of 12.5 min of ZnSO4 oxidation, 94.16% of BPA removal was achieved under the optimum conditions (pH 6.32, 1 mg/L ZnSO4 dose, 2400 mg/L O3 dose). However, under optimum conditions (pH 6.32, 50 mg/L ZnO dose, 2400 mg/L O3 doze, 20 min reaction time), the BPA removals have been obtained as 98.52%. The second-order kinetic model has been found to be the most suitable model for both processes and the regression coefficients (R2) have been found as 0.999 and 0.9979 for ZnSO4 and ZnO catalysts COPs, respectively. The reaction rate constants (k) have also been calculated as 0.0939 L.mg−1.min−1 and 0.0509 L.mg−1.min−1 for BPA in homogeneous and heterogeneous COPs, respectively.

Dynamics of Foliar Responses to O3 Stress as a Function of Phytotoxic O3 Dose in Hybrid Poplar.

With background concentrations having reached phytotoxic levels during the last century, tropospheric ozone (O3) has become a key climate change agent, counteracting carbon sequestration by forest ecosystems. One of the main knowledge gaps for implementing the recent O3 flux-based critical levels (CLs) concerns the assessment of effective O3 dose leading to adverse effects in plants. In this study, we investigate the dynamics of physiological, structural, and morphological responses induced by two levels of O3 exposure (80 and 100 ppb) in the foliage of hybrid poplar, as a function of phytotoxic O3 dose (POD0) and foliar developmental stage. After a latency period driven by foliar ontological development, the gas exchanges and chlorophyll content decreased with higher POD0 monotonically. Hypersensitive response-like lesions appeared early during exposure and showed sigmoidal-like dynamics, varying according to leaf age. At current POD1_SPEC CL, notwithstanding the aforementioned reactions and initial visible injury to foliage, the treated poplars had still not shown any growth or biomass reduction. Hence, this study demonstrates the development of a complex syndrome of early reactions below the flux-based CL, with response dynamics closely determined by the foliar ontological stage and environmental conditions. General agreement with patterns observed in the field appears indicative of early O3 impacts on processes relevant, e.g., biodiversity ecosystem services before those of economic significance – i.e., wood production, as targeted by flux-based CL.

Intensified ozonation in packed bubble columns for water treatment: Focus on mass transfer and humic acids removal

Ozonation has been widely applied for the oxidation of contaminants in wastewater, and the disinfection of water. However, low ozone (O3) mass transfer efficiency in common ozonation reactors requires high O3 doses and causes high energy consumption. In this study, to intensify the O3 mass transfer and oxidation of humic acids (HA) solution, a lava rock packed bubble column (LBC) and a metal pall ring packed bubble column (MBC) were developed and evaluated. In comparison with non-packed bubble column (BC), both LBC and MBC enhanced the O3 mass transfer efficiency and the generation of hydroxyl radicals, thereby increasing the HA removal from an aqueous solution. At applied O3 dose of 33.3 mg/(Lcolumn h), the HA removal efficiency in BC was only 47%. When MBC and LBC were applied, it increased to 66% and 72%, respectively. Meanwhile, the O3 utilization efficiency in LBC reached 68%, which was higher than that in MBC (50%) and BC (21%). Consequently, LBC has the lowest energy consumption (EEO) for HA removal (1.4 kWh/m3), followed by MBC (1.6 kWh/m3) and BC (2.9 kWh/m3). LBC had better performance than MBC due to the adsorptive and catalytic roles of lava rock on the ozonation process. This study demonstrates the advantages of using lava rocks as packed materials in O3 bubble column over metal pall rings in intensifying O3 mass transfer and organic matters removal, which provides some insights into promoting the industrial application of O3.

Low Ozone Concentrations Affect the Structural and Functional Features of Jurkat T Cells

Autohemotherapy is the most used method to administer O2-O3 systemically. It consists in exposing a limited amount of blood to a gaseous O2-O3 and reinfusing it, thus activating a cascade of biochemical pathways involving plasma and blood cells that gives rise to antioxidant and anti-inflammatory responses. The therapeutic effects strictly depend on the O3 dose; it is therefore necessary to understand the relationship between the O3 concentration and the effects on blood cells involved in antioxidant and immune response. Here we performed a basic study on the effects of the low O3 concentrations used for autohemotherapy on the structural and functional features of the human T-lymphocyte-derived Jurkat cells. Ultrastructural, biomolecular, and bioanalytic techniques were used. Our findings showed that 10, 20, and 30 µg O3 concentrations were able to trigger Nrf2-induced antioxidant response and increase IL-2 secretion. However, viability and proliferation tests as well as ultrastructural observations revealed stress signs after treatment with 20 and 30 µg O3, thus designating 10 µg O3 as the optimal concentration in combining cell safety and efficient antioxidant and immune response in our in vitro system. These data offer novel evidence of the fine regulatory role played by the oxidative stress level in the hormetic response of T lymphocytes to O2-O3 administration.

Relationship Between Relative Crop Yield/Woody Plant Biomass and Ground-level Ozone Pollution in China

Currently, ground-level ozone (O3) pollution is increasingly serious in China, and highly threatens plant productivity. In this study, we summarized the relationship between relative crop yield or woody plant biomass and O3 metrics, including M7 (the mean of hourly concentrations from 09:00 to 16:00), SUM06 (sum of hourly concentrations above 60 nmol·mol-1), W126 (Sigmoidal weighted sum of the hourly concentrations during a specified period), PODY[phytotoxic O3 dose above a threshold flux of Y nmol·(m2·s)-1], and the most commonly used AOT40 (accumulated O3 concentrations over an hourly threshold of 40 nmol·mol-1), and proposed their critical level to protect plants against O3 damage. Based on the AOT40 metric, we found that the O3 risk threshold that caused a 5% decrease in yield was 5.93 μmol·mol-1·h for rice, 2.69 μmol·mol-1·h for winter wheat, 8.67 μmol·mol-1·h for maize, and 4.17 μmol·mol-1·h for soybean, indicating that maize may be more tolerant to O3 than the other three crops in China. The O3 risk threshold that led to a 5% reduction in total biomass was 12.20 μmol·mol-1·h across five poplar clones (based on experiment) and 10.87 μmol·mol-1·h across 17 woody plants (based on integrated analysis). On the other hand, some perspectives were presented concerning the establishment of O3 response relationships for important productivity-related parameters, and the improvement of accuracy in O3 regional risk assessment. It is also important to consider how to couple other important factors affecting plant O3 sensitivity (such as soil nitrogen and plant age) into the regional assessment model.

Treatment of Leachate from Open Dumpsite of Municipal Solid Waste by Ozone Based Advanced Oxidation Process

ABSTRACT Open dumping of Municipal Solid Waste (MSW) results in generation of leachate that contains large amounts of organic matter, ammonia, heavy metals, chlorinated organics, phenolic compounds, phthalates, and pesticide residues which irreparably contaminate both surface and groundwater. Advanced Oxidation Processes (AOP) have been reported as one of the effective treatment methods, especially in improving the biodegradability of the leachate as well as effective in removing recalcitrant organics. With AOP pre-treatment rendered the leachate becomes more amenable to further treatment using biological treatment, adsorption, or ion-exchange processes. The study reported in this paper mainly aims at assessing the suitability of ozone and peroxone (O3+H2O2) based advanced oxidation processes (AOP) for the treatment of MSW leachate from the open dumpsite. The effect of reaction time, impact of O3 dose, and H2O2 concentration on the efficiency of COD removal, improvement in the biodegradability of the leachate, and pH change were determined as the performance parameters for the treatment process. The maximum COD removal efficiency was found to be 46% and 82% with ozone alone (3975 mg/L) and with ozone (9275 mg/L) + 50 mg/L H2O2 each with 120 min. reaction time. It is also found that the BOD5/COD ratio has been increased from 0.09 to 0.58 at optimum O3 + 50 mg/L H2O2 treatment would offer as an effective method for increasing the biodegradability.

Combining carbon and oxygen isotopic signatures to identify ozone-induced declines in tree water-use efficiency.

Ground-level ozone (O3) pollution affects the plant carbon and water balance, but the relative contributions of impaired photosynthesis and the loss of stomatal functioning to the O3-induced reductions in water-use efficiency (WUE) remain unclear. We combined the leaf stable dual isotopic signatures of carbon (δ13C) and oxygen (δ18O) with related instantaneous gas exchange performance to determine the effects of O3 dose on the net photosynthetic rate (An), stomatal conductance (gs) and intrinsic WUE (iWUE=An/gs) in four tree species (one being a hybrid) exposed to five O3 levels. The iWUE declined for each step increase in O3 level, reflecting progressive loss of the coupling between leaf carbon gain and water loss. In ambient compared with charcoal-filtered air, the decreased iWUE was associated with reductions in both An and gs (i.e., decreased δ13C and increased δ18O). In elevated O3 treatments, however, the iWUE declines were caused by reduced An at constant or increased gs. The results show that the dual isotope approach provides a robust way to gather time-integrated information on how O3 pollution affects leaf gas exchange. Our study highlights that O3-induced decoupling between photosynthesis and stomatal regulation causes large and progressive declines in the WUE of forest trees, demonstrating the need for incorporating this hitherto unaccounted for effect into vegetation models.

Application of (V)UV/O3 technology for post-treatment of biologically treated wastewater: A pilot-scale study

For the first time, high energy VUV photons and generation of O3 by (V)UV lamps were applied together for removal of active pharmaceutical ingredients (APIs) from biologically treated wastewater (BTWW) in pilot-scale. The core of the pilot container unit was a photoreactor assembly consisting of six photoreactors, each containing a low-pressure Hg lamp (UV dose of 1.2 J/cm2 and 6.6 J/cm2 at 185 nm and 254 nm, respectively). BTWW was irradiated (4.75 min residence time) by (V)UV light in presence of in situ photochemically generated O3 from coolant air of the lamps. Experiments were conducted at the site of two wastewater treatment plants. Out of seven target APIs (namely carbamazepine, ciprofloxacin, clarithromycin, diclofenac, metoprolol, sitagliptin, and sulfamethoxazole), 80–100% removal was accomplished for five and 40–80% for two compounds. Two degradation products of carbamazepine were detected. Degradation products of other target compounds were not found. The applied O3 dose was 30–45 μg O3/mg dissolved organic carbon. Inactivation of up to log-4.8, log-4.5 and log-3.8 could be achieved for total coliform, Escherichia coli and Enterococcus faecalis, respectively. SOS Chromotest indicated no genotoxicity nor acute toxicity. Generation of neither NH4+, NO2− nor NO3− was observed during post-treatment. Electric energy per order values were calculated for the first time for (V)UV/O3 treatment in BTWW with a median value of 1.5 kWh/m3. This technology can be proposed for post-treatment of BTWWs of small settlements or livestock farms to degrade micropollutants before water discharge or for production of irrigation water. Further studies are essential in pilot-scale for other applications.

Coagulation-flocculation followed by catalytic ozonation processes for enhanced primary treatment during wet weather conditions

Combined sewer overflows (CSO), generated during the wet weather flow from the combination of the inflow and stormwater runoff in sewer system, result in an overflow of untreated wastewater from sewer system, which might ultimately contain different micropollutants (MPs). In this study, a coagulation-flocculation-sedimentation (CFS) pretreated CSO spiked with MPs was treated by catalytic ozonation using carbon, iron, and peroxide-based catalysts. The catalysts were characterized and their activity on MPs removal was studied at two different ozone (O3) doses (5 and 10 mg L−1). The effect of the treatment on the spiked CSO effluent was also assessed from the acute toxicity of the effluent using Microtox®, Yeast, and Macrophage cell-line toxicity assay tests. All the carbon-based catalysts showed large surface area, which was strongly influenced by the activation technique in the preparation of the catalysts. The CFS treatment strongly reduced the turbidity (≥60%) but had marginal effect on the UV254, dissolved organic carbon (DOC), and pH. Sludge Based Carbon (SBC) showed strong adsorption capacity (≥60% removal efficiency) for all MPs studied compared to other carbon and iron-based catalysts. Ozonation alone was effective for the degradation of easily oxidizable MPs (sulfamethoxazole, mecoprop, and 2,4-dichlorophenoxyl acetic acid), achieving more than 80% degradation efficiency at 10 mg L−1 of ozone, but not effective for atrazine (≤60% degradation efficiency) at similar O3 dose. Catalytic ozonation (at 10 mg L−1 O3 dose) improved the degradation of the MPs at low catalyst dosage but higher dosage strongly inhibited their degradation. In all cases, the effluents showed negligible acute toxicity, indicating the suitability of the process for the treatment of CSO.

Metabolic and physiological alterations indicate that the tropical broadleaf tree Eugenia uniflora L. is sensitive to ozone

Eugenia uniflora L. is an important fruit tree native to tropical South America that adapts to different habitats, thanks to its metabolic diversity and ability to adjust the leaf antioxidant metabolism. We hypothesized that this metabolic diversity would also enable E. uniflora to avoid oxidative damage and tolerate the enhanced ozone (O3) concentrations that have been registered in the (sub)tropics. We investigated whether carbohydrates, polyphenols and antioxidants are altered and markers of oxidative damage (ROS accumulation, alterations in leaf gas exchange, growth and biomass production) are detected in plants exposed to two levels of O3 (ambient air and twice elevated ozone level in a O3-FACE system for 75 days). Phytotoxic O3 dose above a threshold of 0 nmol m−2 s−1 (POD0) and accumulated exposure above 40 ppb (AOT40) were 3.6 mmol m−2 and 14.898 ppb h at ambient, and 4.7 mmol m−2 and 43.881 ppb h at elevated O3. Twenty-seven primary metabolites and 16 phenolic compounds were detected in the leaves. Contrary to the proposed hypothesis that tropical broadleaf trees are relatively O3 tolerant, we concluded that E. uniflora plants are sensitive to elevated O3 concentrations. Experimental POD0 values were lower than the critical levels for visible foliar O3, because of low stomatal conductance. In spite of this low stomatal O3 uptake, we found classic O3 injury, e.g. reduction in carbohydrates and fatty acids concentrations; non-significant changes in the polyphenol profile; inefficient antioxidant responses; increased contents of ROS and indicators of lipid peroxidation; reductions in stomatal conductance, net photosynthesis, root/shoot ratio and height growth. However, we also found some compensation mechanisms, e.g. increased leaf concentration of polyols for protecting the membranes, and increased leaf number for compensating the decline of photosynthetic rate. These results help filling the knowledge gap about tropical tree responses to O3.

Novel ozone flux metrics incorporating the detoxification process in the apoplast: An application to Chinese winter wheat

A modified Ball-Berry-Leuning model of stomatal conductance was applied to data from fully open-air ozone (O3)-enrichment experiments with winter wheat (Triticum aestivum L.). The O3 fluxes reaching both surface of cell wall (Fcw) and plasmalemma (Fpl) were estimated considering apoplastic ascorbate, a major scavenger of O3. The difference (D) between Fcw and Fpl was defined as detoxification capacity of O3 by reaction with ascorbate in the leaf apoplast (ASCapo). The accumulated stomatal O3 flux above D nmol O3 m−2 s−1 (AFstD) and the accumulated Fpl (AFpl) were calculated over the optimal integration period covering the whole reproductive development of wheat, and used to derive O3AFstD yield-response relationships in comparison with PODY (phytotoxic O3 dose above a threshold of Y nmol m−2 s−1) and AOT40 (accumulated O3 dose over a threshold of 40 ppb). There was a good agreement between the observed and modeled values of ASCapo and stomatal conductance. AFstD and AFpl performed better than PODY and AOT40 in terms of R2 and intercept. However, the AFstD metric was more suitable for assessing grain yield loss due to lower sensitivity of the regression slope to variations in the input parameters, compared with AFpl. The average critical level (CL) of four cultivars for 5% grain-yield reduction was 1.53 mmol m−2 using POD6 and 2.81 mmol m−2 using AFstD, with the latter being well above the POD6-derived value for European cultivars (1.3 mmol m−2). The minimum hourly averaged O3 concentration contributed to CLs was below 20 ppb according to AFstD, a value that is lower than that suggested by POD6 (≈27 ppb). O3 flux-response relationships and CLs on the basis of quantified detoxification capacity shall facilitate the understanding of the different degrees of susceptibility to O3 among species or cultivars, and improve the assessments of O3 impacts on plants.

Prediction of Oxidant Exposures and Micropollutant Abatement during Ozonation Using a Machine Learning Method

Oxidation of micropollutants (MPs) by ozonation proceeds via the reactions with molecular ozone (O3) and hydroxyl radicals (•OH). To predict MP abatement during ozonation, a model that can accurately predict oxidant exposures (i.e., ) needs to be developed. This study demonstrates machine learning models based on the random forest (RF) algorithm to output oxidant exposures from water quality parameters (input variables) that include pH, alkalinity, dissolved organic carbon concentration, and fluorescence excitation-emission matrix (FEEM) data (to characterize organic matter). To develop the models, 60 different samples of natural waters and wastewater effluents were collected and characterized, and the oxidant exposures in each sample were determined at a specific O3 dose (2.5 mg/L). Four RF models were developed depending on how FEEM data were utilized (i.e., one model free of FEEM data, and three other models that used FEEM data of different resolutions). The regression performance and Akaike information criterion (AIC) were evaluated for each model. The models using high-resolution FEEM data generally exhibited high prediction accuracy with reasonable AIC values, implying that organic matter characteristics quantified by FEEM can be important factors to improve the accuracy of the prediction model. The developed models can be applied to predict the abatement of MPs in drinking water and wastewater ozonation processes and to optimize the O3 dose for the intended removal of target MPs. The machine learning models using higher-resolution FEEM data offer more accurate prediction by better calculating the complex nonlinear relationship between organic characteristics and oxidant exposures.

Consequences of ozonation for the limited coagulation of non-proteinaceous AOM and formation of aldehydes as ozonation by-products

Limited knowledge of how ozonation affects algal organic matter (AOM) character and removal hinders assessing the suitability of ozonation for treating AOM-laden waters. This study examines pre-ozonation-coagulation and coagulation-post-ozonation of AOM, specifically its non-proteinaceous fraction (NP). O3 doses of 0.05–4.0 mg per 5 mg dissolved organic carbon were applied at pH 5.5, 7.8, and 9.0; coagulation was performed in pH range 5.0–9.0. Coagulation alone exhibited maximum removal of 15%, and pre-ozonation before coagulation had different impacts depending on both the O3 dose and ozonation pH. In case of pH 5.5 and 7.8, the lowest and highest O3 doses improved the removal (by max. 7%); by contrast, the medium O3 dose deteriorated coagulation. In case of pH 9.0, at which different oxidation pathways predominate, the low and medium O3 doses had negligible effects, while the highest O3 dose improved NP removal (by max. 11%). Noteworthy is that despite these trends appeared throughout the whole coagulation pH range, NP removal depended also on coagulation pH. Post-ozonation after coagulation contributed to NP removal (additional 5–6%) at the highest O3 dose. In general, positive effects of ozonation were ascribed to charge alterations and partial mineralization of NP, adverse effects to changes in molecular weights. Additionally, aldehydes (up to 34.2 μg mg-1 DOC; predominantly formaldehyde and acetaldehyde) were formed whenever ozonation was involved, more with increasing O3 dose, and regardless the ozonation pH. The results emphasize the importance of optimizing ozonation so as to reach the benefits and avoid the undesirable effects on water quality.

Effective removal of contaminants from biotreated leachate by a combined Fe(III)/O3 process: Efficiency and mechanisms

Refractory organics and toxic metals are still the main contaminants in the landfill leachate effluents from membrane bioreactors (MBRs) (expressed as biotreated leachate). In this study, a combined Fe(III)/O3 process was employed for the removal of multiple contaminants from a biotreated leachate in Qingdao city, China. Effects of ozone dose, Fe(III) dose, initial pH and reaction time on the removal efficiency of refractory organics were systemically investigated. The degradation mechanisms of organics were discussed based on a combination of microscopic and spectroscopic analyses. In addition, the removal efficiency of toxic metals from biotreated leachate was also performed. The results indicated that refractory organics in the leachate were effectively degraded in the Fe(III)/O3 system. The removal efficiencies of COD, TOC and UV254 were 80.23%, 74.85% and 85.01%, respectively, under the following optimum operational conditions: O3 dose of 100 mg/min, Fe(III) dose of 6 g/L, reaction time of 25 min, and initial pH of 6.5. At this conditions, the effluent COD and BOD5 were satisfied the discharge standard of pollutants to open seas in Qingdao city, China. Spectroscopic analysis suggested that refractory organics in the leachate were effectively destroyed and mineralized during the Fe(III)/O3 process. Additional, in-situ formation of Fe-containing particles (mainly as Fe(OH)3) contributed to the adsorptive removal of organics and toxic metals (i.e., Cu, Ni, As, Cr, Pb and Zn).

Effectiveness of ozone pretreatment on bioconversion of oily bilge water into biopolymer

Oily bilge water (OBW) is complex wastewater generated from ship operation. In the present study, the application of ozonation pretreatment before the sequential batch reactor (SBR) for removing organics and polyhydroxyalkanoates (PHA) production from complex OBW were investigated. OBW was subjected to lab-scale ozone pretreatment under the various experimental conditions such as a specific reaction time (0 min–120 min), inlet ozone dose (0.5 g/L–2.5 g/L) and solution pH (4–8). Pretreatment of OBW by ozone improved biodegradability index (BDI) from 0.36 to 0.52. The GC–MS analysis revealed that the BDI enhancement was due to the formation of water-soluble carboxylic groups after 75 min of ozonation operated at solution pH 6 and 2 g/ L of O3 dose. The CODs removal efficiency was 68 % and 92 % for SBR and ozonized SBR respectively. Also, the biopolymer production rate was increased by 4.5 folds for ozonized SBR as the bioconversion of carboxylic compounds by using a mixed bacterial consortium (MBC) was stress-free. The functional groups and thermal property of the produced PHA were tested by various analytical techniques. These results confirmed that the bioconversion of ozonized OBW into valuable biological polyesters using MBC.

Tertiary treatability of molasses secondary effluents for color and organics: performance and limits of ozonation and adsorption

Molasses wastewaters (MWWs) such as baker’s yeast and distilleries effluents are usually pretreated by anaerobic, followed by aerobic biodegradation. This removes almost all the BOD, enough for meeting the current discharge standards in many low- and middle-income countries. However, as shown in the present work, the biotreated effluent still contains high levels of recalcitrant COD, color (melanoidins) and inorganic salts that end up in rivers (approx. 1000 mg/L COD, 2850 Pt–Co color units, 5000 mg/L TDS and 5400 μS/cm conductivity). To address this global problematics, and given the lack of proven cost-effective advanced treatment trains for MWW, this study assessed the performance and limits of ozonation and activated carbon (AC) adsorption (contrasting with O3 applications on raw MWW). The applied versus the reacted O3 doses were quantified, allowing also to estimate the ozone uptake rate as a new tool for characterizing the reactivity of the wastewaters. The effects of the treatments on different key parameters were studied: COD, color, aromaticity (UV254 nm), toxicity (Microtox) and biodegradability (by respirometry). O3 reduced the color (> 95%), but causing low COD mineralization (< 35%) and biodegradability enhancement (only 8% more). Meanwhile, adsorption was efficient on both COD and color (97–91%), but needing high AC dosage. In consequence, a more sustainable treatment train was suggested, i.e., upgrading the activated sludge with aerobic granular sludge technology and transforming the granules into AC.

Flux-Based Ozone Risk Assessment for a Plant Injury Index (PII) in Three European Cool-Temperate Deciduous Tree Species

This study investigated visible foliar ozone (O3) injury in three deciduous tree species with different growth patterns (indeterminate, Alnus glutinosa (L.) Gaertn.; intermediate, Sorbus aucuparia L.; and determinate, Vaccinium myrtillus L.) from May to August 2018. Ozone effects on the timing of injury onset and a plant injury index (PII) were investigated using two O3 indices, i.e., AOT40 (accumulative O3 exposure over 40 ppb during daylight hours) and PODY (phytotoxic O3 dose above a flux threshold of Y nmol m−2 s−1). A new parameterization for PODY estimation was developed for each species. Measurements were carried out in an O3 free-air controlled exposure (FACE) experiment with three levels of O3 treatment (ambient, AA; 1.5 × AA; and 2.0 × AA). Injury onset was found in May at 2.0 × AA in all three species and the timing of the onset was determined by the amount of stomatal O3 uptake. It required 4.0 mmol m−2 POD0 and 5.5 to 9.0 ppm·h AOT40. As a result, A. glutinosa with high stomatal conductance (gs) showed the earliest emergence of O3 visible injury among the three species. After the onset, O3 visible injury expanded to the plant level as confirmed by increased PII values. In A. glutinosa with indeterminate growth pattern, a new leaf formation alleviated the expansion of O3 visible injury at the plant level. V. myrtillus showed a dramatic increase of PII from June to July due to higher sensitivity to O3 in its flowering and fruiting stage. Ozone impacts on PII were better explained by the flux-based index, PODY, as compared with the exposure-based index, AOT40. The critical levels (CLs) corresponding to PII = 5 were 8.1 mmol m−2 POD7 in A. glutinosa, 22 mmol m−2 POD0 in S. aucuparia, and 5.8 mmol m−2 POD1 in V. myrtillus. The results highlight that the CLs for PII are species-specific. Establishing species-specific O3 flux-effect relationships should be key for a quantitative O3 risk assessment.

Toxicity of environmental ozone exposure on mice olfactory bulbs, using Western blot technique

Environmental ozone (O3) exposure has adverse effects on different body systems. This experimental work aimed to study the effect(s) of O3 exposure on the olfactory bulbs (OB) of Swiss Webster and C57BL/6J mouse strains, using Western blot technique. Both mice strains were exposed to different O3 doses for different number of exposures and durations. The results indicated that O3 exposure caused a significant increase in the level of the proteins involved in the oxidative stress state such as 4-hydroxynonenal (4HNE) and Cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1), in addition to the total OB proteins in Swiss Webster mouse strain. However, this effect was not observed in C57BL/6J mouse strain. Furthermore, CYP1A1 was completely absent in the Green fluorescent protein (GFP) C57BL/6J O3 exposed mice. Moreover, O3 exposure caused a significant decrease in the body weight of the tested mice from the two strains.

Have improvements in ozone air quality reduced ozone uptake into plants?

Peak levels of ozone (O3)—quantified by concentration metrics such as accumulated O3 exposure over a threshold of 40 ppb (AOT40) and the sigmoidal-weighted cumulative exposure (W126)—have decreased over large parts of the United States and Europe in the last several decades. Past studies have suggested that these improvements in AOT40 and W126 indicate reductions in plant injury, even though it is widely recognized that O3 flux into leaves, not ambient O3 concentration, is the cause of plant damage. Using a new dataset of O3 uptake into plants derived from eddy covariance flux towers, we test whether AOT40, W126, or summer mean O3 are useful indicators of trends in the cumulative uptake of O3 into leaves, which is the phytotoxic O3 dose (POD or PODy, where y is a detoxification threshold). At 32 sites in the United States and Europe, we find that the AOT40 and W126 concentration metrics decreased over 2005–2014 at most sites: 25 and 28 sites, respectively. POD0, however, increased at a majority (18) of the sites. Multiple statistical tests demonstrate that none of the concentration metrics—AOT40, W126, and mean O3—are good predictors of POD0 temporal trends or variability (R2 ≤ 0.15). These results are insensitive to using a detoxification threshold (POD3). The divergent trends for O3 concentration and plant uptake are due to stomatal control of flux, which is shaped by environmental variability and plant factors. As a result, there has been no widespread, clear improvement in POD over 2005–2014 at the sites we can assess. Decreases in concentration metrics, therefore, give an overly optimistic and incomplete picture of the direction and magnitude of O3 impacts on vegetation. Because of this lack of relation between O3 flux and concentration, flux metrics should be preferred over concentration metrics in assessments of plant injury from O3.

Catalytic ozonation of an azo-dye using a natural aluminosilicate

Catalytic ozonation of Orange II (100 mg/L) was studied using aluminosilicate Montanit300® (M) modified with H2SO4 (MS) and HCl (MH). Characterization of these samples was performed through several techniques: SEM/EDX, FTIR, XRD, FRX, TPD pyridine, surface area, pHPZC. Acid treatment increased surface area, Si:Al ratio and quantity of acid sites, but reduced pHPZC and Fe and Mn content.Ozonation experiments achieved complete decoloration and remarkable TOC conversions of 66, 65, 88 and 91 % by single ozonation and catalytic ozonation with MH, MS and M, respectively. Higher M and MS activity under acidic pH was attributed to Mn leaching. Decreased mineralization efficiency in the presence of tert-butanol suggested a radical mechanism. At neutral pH, M showed no activity, while MS presented mild activity owing to its enlarged hydrophobicity.The M sample sustained mineralization levels over 20 h. Lower O3 dose caused quick MS deactivation. However, it was reversed through calcination and prevented with a higher oxidant dose.Mn is naturally found in Montanit300®, thus making it an inexpensive catalyst. The development of a dynamic cycle combining reduced and oxidized forms of Mn was key to the outstanding activity observed.