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PubMed2003

Ozone sensitivity of Fagus sylvatica and Fraxinus excelsior young trees in relation to leaf structure and foliar ozone uptake.

During the summer of 2001, 2-year-old Fraxinus excelsior and Fagus sylvatica plants were subjected to ozone-rich environmental conditions at the Regional Forest Nursery at Curno (Northern Italy). Atmospheric ozone concentrations and stomatal conductance were measured, in order to calculate the foliar fluxes by means of a one-dimensional model. The foliar structure of both species was examined (thickness of the lamina and of the individual tissues, leaf mass per area, leaf density) and chlorophyll a fluorescence was determined as a response parameter. Stomatal conductance was always greater in Fraxinus excelsior, as was ozone uptake, although the highest absorption peaks did not match the peaks of ozone concentration in the atmosphere. The foliar structure can help explain this phenomenon: Fraxinus excelsior has a thicker mesophyll than Fagus sylvatica (indicating a greater photosynthesis potential) and a reduced foliar density. This last parameter, related to the apoplastic fraction, suggests a greater ability to disseminate the gases within the leaf as well as a greater potential detoxifying capacity. As foliar symptoms spread, the parameters relating to chlorophyll a fluorescence also change. PI (Performance Index, Strasser, A., Srivastava, A., Tsimilli-Michael, M., 2000. The fluorescence transient as a tool to characterize and screen photosynthetic samples. In: Yunus, M., Pathre, U., Mohanty, P., (Eds.) Probing Photosynthesis: Mechanisms, Regulation and Adaptation. Taylor & Francis, London, UK, pp. 445-483.) has proved to be a more suitable index than Fv/Fm (Quantum Yield Efficiency) to record the onset of stress conditions.

Air Pollutants↗

PubMed2003

Detecting plant effects is necessary to give biological significance to ambient ozone monitoring data and predictive ozone standards.

The use of mechanical monitors and passive samplers has made it possible to assess concentrations of ozone over wide areas and to develop air quality standards, like AOT40 and SUM60. Monitored ozone data and AOT40 and SUM60 are also used to predict ozone injury on local and regional scales. The data and the standards do not include or account for environmental and biological variables that affect ozone uptake and plant injury. Ground proofing via vegetation surveys must be done to verify and validate plant injury predictions. If this is not done, then the standards have no biological significance and are only exercises in air quality assessment.

Air Pollution↗

PubMed2005

Parameter evaluation and model validation of ozone exposure assessment using Harvard Southern California Chronic Ozone Exposure Study data.

To examine factors influencing long-term ozone (O3) exposures by children living in urban communities, the authors analyzed longitudinal data on personal, indoor, and outdoor O3 concentrations, as well as related housing and other questionnaire information collected in the one-year-long Harvard Southern California Chronic Ozone Exposure Study. Of 224 children contained in the original data set, 160 children were found to have longitudinal measurements of O3 concentrations in at least six months of 12 months of the study period. Data for these children were randomly split into two equal sets: one for model development and the other for model validation. Mixed models with various variance-covariance structures were developed to evaluate statistically important predictors for chronic personal ozone exposures. Model predictions were then validated against the field measurements using an empirical best-linear unbiased prediction technique. The results of model fitting showed that the most important predictors for personal ozone exposure include indoor O3 concentration, central ambient O3 concentration, outdoor O3 concentration, season, gender, outdoor time, house fan usage, and the presence of a gas range in the house. Hierarchical models of personal O3 concentrations indicate the following levels of explanatory power for each of the predictive models: indoor and outdoor O3 concentrations plus questionnaire variables, central and indoor O3 concentrations plus questionnaire variables, indoor O3 concentrations plus questionnaire variables, central O3 concentrations plus questionnaire variables, and questionnaire data alone on time activity and housing characteristics. These results provide important information on key predictors of chronic human exposures to ambient O3 for children and offer insights into how to reliably and cost-effectively predict personal O3 exposures in the future. Furthermore, the techniques and findings derived from this study also have strong implications for selecting the most reliable and cost-effective exposure study design and modeling approaches for other ambient pollutants, such as fine particulate matter and selected urban air toxics.

Air Pollutants↗

PubMed1993

U.S. Environmental Protection Agency's Ozone Epidemiology Research Program: a strategy for assessing the effects of ambient ozone exposure upon morbidity in exposed populations.

The Clean Air Act Amendments of 1990 mandate a future reduction of ambient ozone levels in many areas of the country, the cost of which will be great. In order to assess the current public health burden of ambient ozone exposure and to provide information for assessment of potential health benefits of improved air quality, the Health Effects Research Laboratory of the U.S. EPA has undertaken an Ozone Epidemiology Research Program. The research strategy which will guide this scientific program is described in this paper. Criteria for selection of important research questions as well as issues which cut across all questions and study designs are discussed. In particular, this program emphasizes the study of effects which reflect morbidity in the population. The three questions identified as being of most immediate importance involve the relationship of short-term ambient ozone exposure to acute respiratory illness, the relationship of recurrent exposure to chronic respiratory disease, and the relationship of recurrent exposure to development of acute respiratory illness. Specific research approaches and initial projects to address these three questions are described.

Animals↗

PubMed1983

Ozone killing action against bacterial and fungal species; microbiological testing of a domestic ozone generator.

The action of ozone generated from a small domestic device was examined with a view to using it in clinical isolation units accommodating immunosuppressed patients. Over a six-hour period in an average size room the device did not generate sufficient ozone to suppress bacterial and fungal growth. A useful bactericidal action, against a variety of human pathogens was achieved with ozone concentrations between 0.3 to 0.9 ppm. Bactericidal ozone concentrations are close to the limit permitted for human exposure however and further experiments are indicated.

Bacteria↗

PubMed1992

Effect of ozone on the activities of reactive oxygen scavenging enzymes in RBC of ozone exposed Japanese charr (Salvelinus leucomaenis).

The effect of ozone exposure on the activities of reactive oxygen scavenging enzymes (SOD, catalase, GSH-Px) in RBC of Japanese charr (Salvelinus leucomaenis) was examined. Ozone (0, 0.4 and 0.7 ppm as initial concentrations) was exposed to Japanese charr for 30 min, which definitely caused serious membrane damage to RBC of fish. Ozone exposure at 0.4 and 0.7 ppm decreased activities of both catalase and GSH-Px by 80 to 57% of the control. On the other hand, the activities of SOD remained unaffected even by 0.7 ppm ozone exposure. A hypothesis on the RBC membrane damage and participation of SOD and heme-iron was proposed.

Animals↗

PubMed2004

Formation of by-products in the course of intermediate ozonation of groundwater pretreated with ozone and polyaluminium chloride.

Formation of aldehydes and trihalomethanes during intermediate ozonation of water pretreated with ozone and polyaluminium-chloride was monitored in a pilot-scale study to optimize the drinking water treatment technology. The raw water was the groundwater, rich in natural organic matter, originated from the territory of the Northern Banat region in Vojvodina Province, Serbia and Montenegro. Monitoring of the parameters that have to meet prescribed criteria (permanganate value, TOC and THMFP removal) could not give an indication on how to split the required ozone dose between preozonation and intermediate ozonation. As the effects obtained regarding THMFP and TOC removal were similar, monitoring of aldehydes was performed, and this clearly showed that preozonation should be carried out with a dose > or = 0.4 mg O3/mg TOC to obtain the water with the smallest contents of aldehydes and the lowest specific content of glyoxal in the GAC filter influent.

Aldehydes↗

PubMed1993

No general ozone-specific indicator among the hexane- and dichloromethane-soluble components of Picea abies needles exposed to ozone in open-top chambers.

The effect of ozone (< 10, 200 or 400 microg m(-3) on hexane- and dichloromethane-soluble components of Picea abies needles was determined by fumigating potted grafts from mature trees. The trees (>55 and 125 years, 2.5 m high), representing six clones of Norway spruce, were fumigated in open-top chambers at two locations in Norway for one growth season. The needles were extracted with hexane and dichloromethane; 142 compounds from the hexane extract and 164 silylated compounds from the dichloromethane extract were analysed by gas chromatography although no identifications were made. The concentration of four of the compounds from the hexane extract changed with ozone dose in a way that made them promising as indicators, but the present analytical method could not verify this possibility. None of the other 302 compounds qualified as a general indicator of ozone stress in Norway spruce, as none changed its concentration with ozone dose consistently in all romets of all clones. Most of the variation in the experiment is mainly attributable to genetic variation and to climate.

Journal Article↗

PubMed2001

Observations of ozone formation in power plant plumes and implications for ozone control strategies.

Data taken in aircraft transects of emissions plumes from rural U.S. coal-fired power plants were used to confirm and quantify the nonlinear dependence of tropospheric ozone formation on plume NO(x) (NO plus NO(2)) concentration, which is determined by plant NO(x) emission rate and atmospheric dispersion. The ambient availability of reactive volatile organic compounds, principally biogenic isoprene, was also found to modulate ozone production rate and yield in these rural plumes. Differences of a factor of 2 or greater in plume ozone formation rates and yields as a function of NO(x) and volatile organic compound concentrations were consistently observed. These large differences suggest that consideration of power plant NO(x) emission rates and geographic locations in current and future U.S. ozone control strategies could substantially enhance the efficacy of NO(x) reductions from these sources.

Journal Article↗

PubMed2002

On the "ozone deficit problem": what are Ox and HOx catalytic cycles for ozone depletion hiding?

Studies on the role of vibrational excitation in the reactants for the O2 + O2, OH + O2, and HO2 + O2 reactions show that they can be important sources of ozone in the stratosphere, particularly at conditions of local thermodynamic disequilibrium. The results suggest that the Ox and HOx cycles commonly viewed as catalytic sinks of ozone may actually lead to its production, and hence help to clarify the "ozone deficit problem". This paper also presents an explanation for the general overestimation of the OH abundance in the upper stratosphere and lower mesosphere through standard HOx chemistry.

Atmosphere↗

PubMed2001

Global tropospheric ozone dynamics. Part II: Numerical modelling of tropospheric ozone variability.

Various causes of tropospheric changes have been considered in Part I in connection with the analysis of observation data. It is clear however, that the principal instrument for understanding numerous and often interacting causes of ozone changes is numerical modelling. A review of the current status of the numerical modelling has been made for the variability of the ozone concentration in the troposphere. Observation data on tropospheric ozone and relevant numerical modelling results show that a necessity exists to get more adequate global observational data.

Air Pollutants↗

PubMed2005

Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species.

Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury.

Air Pollutants↗

PubMed2005

Ozone-induced changes in the chloroplast structure of conifer needles, and their use in ozone diagnostics.

Ozone induces characteristic symptoms in the chloroplasts of the needles of several coniferous species. Chloroplasts are (1) reduced in size and (2) the stroma is electron dense. Moreover, (3) these chloroplast alterations are more pronounced in the outer mesophyll cell layers and in the upper side of the needle compared to the inner layers and lower side. The syndrome, including the three symptoms (1)-(3), is found in the green needles of Scots pine and Norway spruce not only in the experimental fumigations, but also in mature trees in the field, and has potential for diagnosis of ozone stress. For sound ozone diagnostics all three symptoms must be present in the samples studied. The symptoms in relation to needle anatomy and physiology is discussed, and recommendations for sampling and analysis are given.

Acclimatization↗

PubMed2006

Merits of ozonation and catalytic ozonation pre-treatment in the algal treatment of pulp and paper mill effluents.

Since the performance of algal treatment for pulp mill effluent decreases with increasing color intensity and AOX content, which mainly originate from the chlorine bleaching of Kraft pulp, the separated CEH bleaching effluent was pre-treated by both the conventional and the heterogeneous catalytic ozonation processes. An increase in the BOD(5)/COD ratio from 0.11 to 0.28 and 87% color abatement in terms of Pt-Co were achieved by catalytic ozonation, which had the best treatment performance. Biodegradability enhancement of the CEH effluent correlated well with a decrease in toxicity, high-molecular-weight-compound content, and AOX abatement. By the pre-treatment of the CEH bleaching effluent, the overall efficiencies of algal treatment of the combined pulp mill effluent in terms of the fractional removal of COD and color were increased from 76% and 53% to 86-90% and 96-99%, respectively. Effects of both the conventional and the catalytic ozonation pre-treatments on subsequent biological treatment were close to each other and they reduced the filling period of the Sequential Batch Reactor (SBR) cycle from 8 to 5 days.

Biodegradation, Environmental↗

PubMedDate not supplied

Reactions of ozone with fatty acid monolayers: a model system for disruption of lipid molecular assemblies by ozone.

Ozone concentrations of 0.03 ppm are shown to initiate physical disruption of both oleic and linoleic acid spread monolayers in a few seconds. Approximately equal yields of water soluble products in nitrogen- and oxygen-containing environments as well as in the two acid systems suggest that the dominant reaction pathway involves direct attack on fatty acid double bonds and not oxidative chain reactions. A possible explanation for the observed loss of monolayer material is provided by the Criegee mechanism for ozonide rearrangement following ozone attachment to double bonds. In this scheme polar intermediates are generated which could pass into the aqueous subphase before recombination can occur. alpha-Tocopherol exhibits a protective effect only when present at a high fraction in the fatty acid monolayer (6 mole%). These systems provide an efficient elementary model for studying the physical effects of ozone on lipid membrane structure.

Fatty Acids↗

PubMed2006

The use of ozone in dentistry and medicine. Part 2. Ozone and root caries.

A previous paper, recently published in Primary Dental Care, gave an overview of the medical uses of ozone and outlined some of its uses in dentistry. The current paper focuses on a description of use of ozone in the management of root caries and considers recent studies in this area. There has been relatively limited research into the non-invasive (pharmaceutical) management of root caries. The best management strategy still remains to be developed. Initial studies have indicated that an application of ozone for a period of either 10 or 20 seconds is capable of clinically reversing leathery root carious lesions. It is suggested that, subject to confirmation from extensive trials, this simple and non-invasive technique may benefit many patients with root caries throughout the world since this approach to treat root caries can easily be employed in primary care clinics and in the domiciliary treatment of home-bound elderly people and immobile patients in hospices and hospitals.

Anti-Infective Agents↗

PubMed2005

Ground-based zenith sky abundances and in situ gas cross sections for ozone and nitrogen dioxide with the Earth Observing System Aura Ozone Monitoring Instrument.

High-accuracy spectral-slit-function calibration measurements, in situ ambient absorption gas cell measurements for ozone and nitrogen dioxide, and ground-based zenith sky measurements with the Earth Observing System Aura Ozone Monitoring Instrument (OMI) flight instrument are reported and the results discussed. For use of high-spectral-resolution gas absorption cross sections from the literature in trace gas retrieval algorithms, accurate determination of the instrument's spectral slit function is essential. Ground-based measurements of the zenith sky provide a geophysical determination of atmospheric trace gas abundances. When compared with other measurements, they can be used to verify the performance of the OMI flight instrument. We show that the approach of using published high-resolution absolute absorption cross sections convolved with accurately calibrated spectral slit functions for OMI compares well with in situ gas absorption cell measurements made with the flight instrument and that use of these convolved cross sections works well for reduction of zenith sky data taken with the OMI flight instrument for ozone and nitrogen dioxide that are retrieved from measured spectra of the zenith sky with the differential optical absorption spectroscopy technique, the same method to be used for the generation of in-flight data products. Finally, it is demonstrated that the spectral stability and signal-to-noise ratio performance of the OMI flight instrument, as determined from preflight component and full instrument tests, are sufficient to meet OMI mission objectives.

Air Pollutants↗

PubMed2001

Ozonation of blood during extracorporeal circulation. II. Comparative analysis of several oxygenator-ozonators and selection of one type.

Exposure of human blood ex vivo to oxygen-ozone (O2-O3) using either dialysis exchangers or normal oxygenators gives rise to a number of problems, one of which linked to platelet activation, leads to rapid occlusion and no gas exchange. Semipermeable membranes were found unsuitable because, except for one, they were gas-transfer inefficient, allowed ultrafiltration and were more or less vulnerable to O3. Over the last three years we have examined several types of hydrophobic O3-resistant hollow fiber capillaries but, if the polypropylene surface is not properly coated, there is platelet aggregation and blood coagulation. These problems while far less relevant with O2 alone, become prohibitive in the presence of ozone. Recently new oxygenators have been prepared with special materials to make them more biocompatible and it has become possible to oxygenate and ozonate up to 5L of blood in about an hour, thus making the treatment of critical patients feasible.

Blood Gas Analysis↗