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PubMed2006

Modelling stomatal ozone flux and deposition to grassland communities across Europe.

Regional scale modelling of both ozone deposition and the risk of ozone impacts is poorly developed for grassland communities. This paper presents new predictions of stomatal ozone flux to grasslands at five different locations in Europe, using a mechanistic model of canopy development for productive grasslands to generate time series of leaf area index and soil water potential as inputs to the stomatal component of the DO(3)SE ozone deposition model. The parameterisation of both models was based on Lolium perenne, a dominant species of productive pasture in Europe. The modelled seasonal time course of stomatal ozone flux to both the whole canopy and to upper leaves showed large differences between climatic zones, which depended on the timing of the start of the growing season, the effect of soil water potential, and the frequency of hay cuts. Values of modelled accumulated flux indices and the AOT40 index showed a five-fold difference between locations, but the locations with the highest flux differed depending on the index used; the period contributing to the accumulation of AOT40 did not always coincide with the modelled period of active ozone canopy uptake. Use of a fixed seasonal profile of leaf area index in the flux model produced very different estimates of annual accumulated total canopy and leaf ozone flux when compared with the flux model linked to a simulation of canopy growth. Regional scale model estimates of both the risks of ozone impacts and of total ozone deposition will be inaccurate unless the effects of climate and management in modifying grass canopy growth are incorporated.

Biomass↗
PubMed2005

Oxidative damage in substantia nigra and striatum of rats chronically exposed to ozone.

The purpose of this work was to study if chronic low-dose ozone exposure could per se induce oxidative damage to neurons of striatum and substantia nigra. Thirty male Wistar rats were divided into three groups--Group 1: exposed to an air stream free of ozone; Group 2: exposed for 15 days to ozone; Group 3: exposed for 30 days to ozone. Ozone exposure was carried out daily for 4 h at a 0.25 ppm dose. Each group was then tested for (1) motor activity, (2) quantification of lipid peroxidation levels, (3) Klüver-Barrera staining, and (4) immunohistochemistry for tyrosine hydroxylase (TH), dopamine and adenosine 3',5'-monophosphate-regulated phosphoprotein of 32 kD (DARPP-32), inducible nitric oxide synthase (iNOS), and superoxide dismutase (SOD), to study neuronal alterations in striatum and substantia nigra. Results indicate that ozone exposure causes a significant decrease in motor activity. Ozone produced lipid peroxidation, morphological alterations, loss of fibers and cell death of the dopaminergic neurons. The DARPP-32, iNOS and SOD expression increased with repetitive ozone exposure. These alterations suggest that ozone causes oxidative stress which induces oxidative damage to substantia nigra and striatum of the rat.

Algorithms↗
PubMed2006

Effects of ozonation process on lignin-derived compounds in pulp and paper mill effluents.

The effect of ozonation process on pulp and paper mill effluents was investigated. The objectives were to: (1) identify various compounds in wastewater from a pulp and paper mill, (2) evaluate decolorization and organic removal efficiency by conventional bubble reactor and (3) evaluate the biodegradability at various progressive stages of ozonation. The qualitative GC/MS analyses were performed before and after the biological treatment and ozonation process. Two groups of compounds were observed in this wastewater: lignin-derived compounds and aliphatic compounds used in the pulp and paper production process (i.e. n-alkanes, fatty alcohols, fatty acid and ester). Treatment efficiency was measured by decolorization and TOC removal rates. Additionally, the utilization coefficient (k) and BOD/COD ratio were determined to observe the biodegradability of ozonized effluents. The results indicated that after 45 min, the ozonation of effluents yielded almost colorless effluent with over 90% decolorization efficiency and with corresponding ozone capacity rate of 20.0 mg O(3)L(-1). This decolorization was not always accompanied by the mineralization of the organic matters therefore ozonation was not related to TOC removal rates. The BOD/COD ratio increased from 0.10 to a maximum value of 0.32 with ozone flow rate (O/F) of 4.0 L min(-1). It was confirmed by the utilization coefficient as first order BOD equation, the magnitude k value increased from 0.21 day(-1) to maximum value of 0.47 day(-1) as the ozonation time was raised to 60 min with O/F 4.0 L min(-1).

Color↗
PubMed2006

Absorption kinetics of ozone in water with ultrasonic radiation.

A mathematical model was proposed to depict classical unsteady state method that was used to determine volumetric mass transfer coefficient of ozone from gaseous phase to aqueous phase during sonolysis. The rate constant of ozone self-decomposition with ultrasonic radiation, which was one of the parameters in the model, was determined with separate experiments. The results showed that self-decomposition rate constants of ozone were enhanced by ultrasound. The self-decomposition rate constant of ozone is linearly dependent on ultrasonic power, but the increase of the decomposition rate could not enhance ozone mass transfer coefficient. The volumetric mass transfer coefficients of ozone were also enhanced by ultrasonic radiation, while ultrasonic power had little effect on volumetric mass transfer coefficient of ozone. The degassing effect of ozone due to ultrasonic radiation was insignificant in the sparged system when ozone was bubbled during sonolysis.

Absorption↗
PubMed2005

Variations of respiratory activity and glutathione in activated sludges exposed to low ozone doses.

Ozonation is one of the most effective treatments for reducing the production of activated sludges in wastewater treatment plants. However, because microorganisms are present in the form of microcolonies, some bacteria may be exposed to sub-lethal ozone doses that could lead to adaptation and resistance to further exposition to oxidative treatment. This represents a major question as it may limit the effect of the treatment, especially when low ozone doses are applied. The critical ozone dosage, defined as the lowest specific transferred ozone concentration leading to a decrease in the maximum oxygen uptake rate was estimated to range between 0.9 and 13.6mg O(3)g(-1) COD(sludges), according to the sludges tested. The lowest ozone dosage leading to the decrease of GSH and GSHt concentrations could be estimated to be lower than 10mg O(3)g(-1) COD(sludges) for GSH, and close to 10mg O(3)g(-1) COD(sludges) for GSHt. After sludge exposure to low ozone doses, no higher amounts of glutathione were synthesized, suggesting that no development of resistance to ozonation occurred after sludge treatment with low ozone doses.

Bacteria↗
PubMed2006

Oxidative degradation of N-nitrosodimethylamine by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide.

This study investigates the oxidative degradation of N-nitrosodimethylamine (NDMA), a probable human carcinogen, by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide (AOP O(3)/H(2)O(2)). The rate constants of reactions of NDMA with ozone and hydroxyl radical ((*)OH) were determined to be 0.052+/-0.0016M(-1)s(-1) and (4.5+/-0.21)x10(8)M(-1)s(-1), respectively. The experiments performed with buffered deionized water varying solution pH and employing H(2)O(2) and HCO(3)(-) clearly showed that the reaction with (*)OH dominates the NDMA oxidation during ozonation. Conventional ozonation with up to 160 microM (=7.7 mgL(-1)) ozone led to less than 25% NDMA oxidation in natural waters. The AOP O(3)/H(2)O(2) required 160-320 microM ozone ([O(3)](0)/[H(2)O(2)](0)=2:1) to achieve 50-75% NDMA oxidation. However, multiple injections of ozone of the same overall dose somewhat improved the oxidant utilization efficiency by minimizing (*)OH scavenging contribution of oxidants. Methylamine (MA) was found to be a major amino product from NDMA oxidation initiated by (*)OH. The mechanism of NDMA oxidation to MA is discussed based on the results obtained in this study and the previous literature. Bromate formation may be the limiting factor for NDMA oxidation during ozonation and ozone-based AOPs in bromide-containing waters.

Dimethylnitrosamine↗
PubMed1990

A nonlinear pharmacologic model of the acute effects of ozone on the human lungs.

A pharmacologic model describing the quantitative relationship between short-term exposure to ozone and pulmonary airway resistance is described. The model simulates the following processes: (1) removal of a fraction of inhaled ozone in the airways of the head; (2) ozone oxidation of membrane-bound fatty acids in the target tissue in the lower airways; (3) rupture of cell membranes, releasing inflammatory mediators into the intercellular space; (4) migration of inflammatory cells into the injured tissue, releasing additional mediators and thus amplifying the inflammatory effect of ozone in a positive feedback loop; (5) stimulation of irritant receptors by ozone directly and by inflammatory mediators leading to vagally mediated bronchoconstriction. Mathematically the model consists of a logistic equation determining losses in the head, and a set of four differential equations simulating the uptake of ozone in the target tissue and the ensuing inflammation and bronchoconstriction. The observed human response to ozone in chamber studies is nonlinear, and it was necessary to introduce a nonlinear feedback loop for inflammation in the model to replicate this. Despite limited data upon which to base the model, it successfully predicts the human response to ozone reported in a series of published short-term chamber studies and is superior to "effective dose" (the product of ozone concentration, minute ventilation, and exposure duration) used by other investigations to describe dose-response relationships. Nonlinear multicompartment pharmacologic models such as this one can exhibit very complex behavior making the estimation of model parameters difficult, but they hold promise because the physiologic processes under study are themselves complex nonlinear phenomena.

Airway Resistance↗
PubMed2000

Cyclooxygenase-2 participates in the late phase of airway hyperresponsiveness after ozone exposure in guinea pigs.

We examined the role of cyclooxygenase in airway hyperresponsiveness and inflammation after ozone exposure in guinea pigs using a non-selective (indomethacin) and a selective (JTE-522) cyclooxygenase-2 inhibitor. Spontaneously breathing guinea pigs were exposed to ozone (3 ppm) for 2 h after treatment with vehicle, indomethacin (10 mg/kg) or JTE-522 (10 mg/kg). Airway responsiveness to inhaled histamine (PC(200)) and bronchoalveolar lavage were assessed before, immediately and 5 h after ozone exposure. Ozone caused a significant airway hyperresponsiveness immediately after exposure, which persisted after 5 h. Neither JTE-522 nor indomethacin affected airway hyperresponsiveness immediately after ozone exposure, but significantly attenuated airway hyperresponsiveness 5 h after exposure, suggesting that cyclooxygenase-2 may participate in the late phase of airway hyperresponsiveness but not in the early phase. Ozone caused a significant increase in the concentration of prostaglandin E(2) and thromboxane B(2) in bronchoalveolar lavage fluid immediately after exposure, which decreased to the basal level 5 h after exposure. This increase in prostaglandin E(2) and thromboxane B(2) was significantly inhibited by JTE-522. An expression of cyclooxygenase-2 was detected not only after ozone exposure but also before, and there was no difference in the number of cyclooxygenase-2-positive cells at any time point. An exogenously applied thromboxane A(2) mimetic, U-46619 (10(-5) M), induced airway hyperresponsiveness 5 h after inhalation, but not immediately or 3 h after inhalation. These data suggest that cyclooxygenase-2 may be constitutively expressed before ozone exposure in guinea pig airway and may synthesize prostaglandin E(2) and thromboxane A(2) transiently under ozone stimulation and that thromboxane A(2) may, in turn, induce the late phase of airway hyperresponsiveness.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2002

Characterization of ozone decomposition in a soil slurry: kinetics and mechanism.

A series of soil slurry experiments were performed in a carefully conceived reactor set-up to investigate the characteristics of the catalytic decomposition of ozone on a sand and iron surface. Real time on-line monitoring of ozone in the reaction module was possible using flow injection analysis coupled with a computer-controlled UV detector and data acquisition system. The effects of the soil media and size, ozone dosage, pH and p-CBA as a probe compound were examined at the given experimental conditions. Two apparent phases existed, and ozone instantaneously decomposed within one second in the first phase. These were defined as the instantaneous ozone demand (ID) phase, and the relatively slow decay stage. The interactions of ozone with the soil organic matter (SOM) and metal oxides were attributed mostly to the instantaneous decomposition of ozone. From the probe (p-CBA) experiments, 60-68% of total p-CBA removal occurred during the ID phase. The generation of hydroxyl radicals (OH.) was demonstrated and was closely related with metal oxides as well as SOM. Metal oxides in soil surface were considered to have relatively faster reaction rate with ozone and provide more favorable reactive sites to generate higher amount of OH. than SOM. Even at one-tenth concentration of the sands, a goethite-induced catalytic reaction outfitted the removal rate ofp-CBA among all the soils tested. More than 40% of total p-CBA removal occurred on the soil surface. It was inferred that the radical reaction with the probe compound seemed to take place not only on the soil surface but also in the solid-liquid interface. Ozone decomposition and the reaction between OH. and p-CBA appeared to be independent of any change in pH.

Catalysis↗
PubMed2002

Ozonation of naphthalene sulfonic acids in aqueous solutions. Part I: elimination of COD, TOC and increase of their biodegradability.

Ozonation of 11 naphthalene sulfonic acids (NSA) in the aqueous solution was studied by bubbling at 31 degrees C at an ozone dose rate of 5.56 mg min(-1) l(-1). COD, TOC and BOD5 of these compounds were tested. It was found that COD and TOC can be removed effectively by ozonation as expected. More than 40% COD of compounds No. I (2-amino-1-NSA), No. 5 (1-hydroxy-7-amino-5-NSA), No. 6 (6-hydroxy-1-NSA), No. 8 (6-amino-1,4-naphthalene disulfonic acid) and No. 11 (I -hydroxy-6-amino-3-NSA) has been eliminated at an ozone dosage of 5.56 mg min(-1) l(-1) for 2 h. Although TOC removal was very different, a good biodegradability was reached for NSAs with an average ozone consumption of 3.0 mgl(-1) for a TOC0 concentration of 100 mg(-1). Ozonation and biotreatment should be good alternatives for these compounds, especially after 20% TOC reduction and TOC removal were more sensitive in predicting an increase in biodegradability during ozonation, than that of COD. NSAs are similar in their behavior with reference to ozone consumption. In order to obtain a good biodegradability of NSAs at a TOC0 concentration of 100 mgl(-1), an ozone consumption between 2.0 and 4.0 mg mg(-1) ACOD is needed for this setup and 3.0 mg O3 mg(-1) TOC0 requirement may be more practical in predicting the biological behavior of naphthalene compounds.

Biodegradation, Environmental↗
PubMed2003

Background ozone monitoring and phytodetection in the greater rural area of Corinth--Greece.

Natural background ozone levels were monitored in three places within the greater rural area of Corinth, namely Bogdani Hill, Astronomical Observatory of Krionerion, and Kiato, and compared with ambient ozone monitored in the metropolitan area of Athens. Measurements were made sequentially, for a few weeks at each place, during the summer of 2000. In addition, ozone phytodetection, using tobacco (Nicotiana tabacum L.) plants of the Bel-W3 and Zichnomirodata varieties, was conducted in 12 places (the above included). Moreover, stomatal conductance was measured in the Bel-W3 plants, as well as in leaves of cultivated grape-vines (Vitis vinifera L.) and in needles of Aleppo pine (Pinus halepensis Mill.) trees and compared with the diurnal pattern of ozone concentrations. The 24 and 12 (08:00-20:00) hourly averages of ozone concentrations were high in Athens (37; 51 ppb), at Bogdani Hill (53; 56 ppb) and at the Astronomical Observatory (56; 55 ppb), but relatively low in Kiato (30; 34 ppb). Furthermore, the average daily AOT40 (accumulated exposure over 40 ppb for the daylight hours) (ppbh) was 193 in Athens, 212 at Bogdani Hill, 192 at the Astronomical Observatory and 47 in Kiato. Ozone concentrations exhibited the usual diurnal pattern in Athens (altitude 50 m), where they were maximum during midday and early afternoon hours, as well as at Bogdani Hill (300 m) and in Kiato (5 m) where, however, they were maximal 1-3 h later. At the Astronomical Observatory (altitude 920 m) ozone remained constant during both daylight and night hours. The differences in diurnal patterns are consistent with those in places of different elevation, reported elsewhere. The Bel-W3 plants were injured at all 12 places; Zichnomirodata plants exhibited lower injury and only in some of the places; probable ozone symptoms were also observed on vine plants and pine trees. The greatest injury was observed at the high altitude places of Astronomical Observatory and Mougostos. Stomatal conductance, in all three species, peaked during morning and early midday hours when ozone levels were higher in the high altitude, and lower in the low altitude, places.

Environmental Monitoring↗
PubMed2003

Chloroplastic responses of ponderosa pine (Pinus ponderosa) seedlings to ozone exposure.

Integrity of chloroplast membranes is essential to photosynthesis. Loss of thylakoid membrane integrity has been proposed as a consequence of ozone (O(3)) exposure and therefore may be a mechanistic basis for decreased photosynthetic rates commonly associated with ozone exposure. To investigate this hypothesis, Pinus ponderosa seedlings were exposed to ambient air or ozone concentrations maintained at 0.15 or 0.30 microliter l(-1) for 10 h day(-1) for 51 days during their second growing season. Over the course of the study, foliage samples were periodically collected for thylakoid membrane, chlorophyll and protein analyses. Additionally, gas-exchange measurements were made in conjunction with foliage sampling to verify that observed chloroplastic responses were associated with ozone-induced changes in photosynthesis. Needles exposed to elevated ozone exhibited decreases in chlorophyll a and b content. The decreases were dependent on the duration and intensity of ozone exposure. When based on equal amounts of chlorophyll, ozone-exposed sample tissue exhibited an increase in total protein. When based on equal amounts of protein, ozone-exposed samples exhibited an increase in 37 kDa proteins, possibly consisting of breakdown products, and a possible decrease in 68 kDa proteins, Rubisco small subunit. There was also a change in the ratio of Photosystem I protein complexes CPI and CPII that may have contributed to decreased photosynthesis. Net photosynthetic rates were decreased in the high ozone treatment suggesting that observed structural and biochemical changes in the chloroplast were associated with alterations of the photosynthetic process.

Chlorophyll↗
PubMed1997

Chronic exposure of rats to ozone and sulfuric acid aerosol: biochemical and structural responses.

Groups of rats were exposed to either 0.12 or 0.20 ppm of ozone, 20, 100, or 150 ppm of sulfuric acid aerosol (0.4-0.8 microm diameter), or their mixtures in whole body exposure chambers for up to 90 days. Matched control animals were exposed to filtered air in comparable chambers. The rats were examined biochemically and morphometrically for centriacinar fibrosis or other indicators of pollutant-induced changes in the terminal bronchiole-alveolar duct junction region of the lung at the end of the exposures. By evaluating different markers of lung injury, we had previously demonstrated a synergistic interaction between ozone and sulfuric acid aerosol after acute exposures to these same concentrations of the pollutants. The present experiments were designed to answer the question of whether there was any interaction between ozone and respirable sized aerosols of sulfuric acid, synergistic or antagonistic, after chronic exposures. Exposure of rats to 0.12 or 0.20 ppm of ozone elicited tissue and cellular changes at the bronchiole-alveolar duct junction. Concurrent exposure to sulfuric acid aerosol did not affect the extent or magnitude of these changes. Intermittent exposure (12 h per day) to ozone, with or without the acid aerosol, elicited a greater response than did continuous exposure (24 h per day). No consistent effects of exposure to sulfuric acid aerosol alone were observed, either morphometrically or biochemically. The biochemical data were consistent with the morphometric analyses, showing trends towards or significantly increased lung 4-hydroxyproline content in the rats exposed to ozone, with or without sulfuric acid aerosol, in the intermittent exposure experiment, but not after continuous exposure. No interactive effects between ozone and sulfuric acid aerosol were observed with any of the biochemical parameters examined. We conclude that ozone and sulfuric acid aerosols do not exhibit synergistic interactions after chronic exposures (90 days) of rats to the concentrations tested in this study, which correspond to concentrations showing synergistic interactions in previously performed acute studies. We also observed that exposure of rats to ozone for 12 h per day elicited greater lung changes, which we interpret to indicate a mild fibrotic response, than did exposure of rats for 24 h per day, whether or not there was accompanying exposure to the acid aerosol.

Aerosols↗
PubMed1998

Interactions between human bronchoepithelial cells and lung fibroblasts after ozone exposure in vitro.

Long-term exposure to ozone has been shown to cause lung fibrosis and increased collagen synthesis by fibroblasts in experimental animals. As the bronchial epithelium appears to play a major regulatory role in inflammatory processes, we investigated whether ozone induces bronchoepithelial cells in vitro to increase gene expression of procollagens and other fibrogenic mediators in human lung fibroblasts. Membrane cultures of human airway epithelial cells (BEAS-2B) in the presence or absence of lung fibroblast (HFL-1) cultures were exposed to air or 500 ppb ozone for 1 h, followed by (co-)incubation periods of 11 and 23 h. After ozone exposure of the co-cultures, there were substantial increases of steady-state mRNA levels of both alpha1 procollagens type I and III as well as TGF beta1 in the fibroblasts above the corresponding air control levels. In the absence of ozone, the presence of epithelial cells always caused significant decreases in the basal steady-state mRNA levels of both procollagens as compared to their absence. There were no significant effects of ozone on the secretion or gene expression of TGF beta2, PDGF or IL-8 in any cell type. In contrast, co-culture condition induced altered patterns of IL-8 gene expression or of PDGF production in fibroblasts and bronchoepithelial cells, respectively, both in the absence or presence of ozone. In summary, our data demonstrate that the effect of ozone on fibroblasts was mediated by epithelial cells and that mutual regulatory interactions between the different cell types occur. Thus, our co-cultivation system in vitro appears to be able to mimic the in vivo situation providing insight into the nature of cellular interactions and modulation by ozone, which may occur in the whole organism after long-term exposure.

Bronchi↗
PubMedDate not supplied

Generation of oxidative stress in human cutaneous models following in vitro ozone exposure.

Ozone, one of the main components of photochemical smog, represents an important source of environmental oxidative stress. The skin, being the outermost barrier of the body, is directly exposed to environmental oxidant toxicants. Skin sebum and cellular plasma membrane lipids contain polyunsaturated fatty acids which are primary targets for ozone and free radical attack induced lipid peroxides. These ozonation processes in skin can also generate aldehydes, hydroxyhydroperoxides and specific Criegee's ozonides. In order to evaluate in vitro human skin susceptibility to ozone, we have exposed cultured immortalized human keratinocytes (DK7-NR) and the reconstructed human epidermis Episkin to 10 ppm of ozone in a specific incubator. We measured the formation of protein carbonyls by an ELISA method and monitored the oxidative stress using the fluorogenic probe 2',7'-dichlorofluorescin-diacetate (DCFH-DA). Results showed a time-dependent increase of fluorescence levels (linked to oxidative stress) in both models exposed to ozone. Using this protocol, we investigated the protective potential of different products including vitamin C, a thiol derivative and a plant extract. All products dramatically reduced oxidative responses during ozone exposure. Decreases observed in fluorescence levels were between 60 and 90% as compared to non-protected controls. These results demonstrate: (a) cutaneous in vitro models are remarkably susceptible to oxidative stress generated by an environmental air pollutant as ozone, and (b) raw antioxidants, thiols and vitamin C were efficient products to prevent ozone induced cellular oxidative damage.

Acetylcysteine↗
PubMed1997

Aromatic hydroxylation in nasal lavage fluid following ambient ozone exposure.

Ozone at ambient concentrations affects lung function and initiates an inflammatory response of the airways. However, the underlying mechanisms are poorly understood. In vitro studies have shown that ozone reacts with water to give reactive hydroxyl radicals capable of oxidizing a wide range of biomolecules. We conducted a study to determine if in vivo hydroxyl radical attack on human airways occurs under natural exposure to ozone. The relation of orthotyrosine to para-tyrosine as a measure of hydroxyl radical attack was analyzed in nasal lavage samples of 44 primary school children in an epidemiologic study. Repeated nasal lavages were performed between May and October 1991 both following "low" (daily half-hour maximum < 140 micrograms/m3, approximately 70 ppb) and "high" (daily half-hour maximum > 180 micrograms/m3, approximately 90 ppb) ozone exposure. Concomitantly, lung function tests were performed. On average, 11.6 (6-16) nasal lavages were performed for each of 24 study days (10 days following "low" ozone exposure and 14 days following "high" ozone exposure). Average ortho-tyrosine (median; 5-95% percentile) for each child was 0.037 mumol/L (0.016-0.064 mumol/L) and average para-tyrosine was 15.7 mumol/L (9.8-24.1 mumol/L). Ortho-tyrosine (as percentage of tyrosine) was significantly higher following days with "high" ozone exposure (0.18%) vs. days following "low" ozone exposure (0.02%; p = .0001). Ortho-tyrosine showed an inverse relationship with forced vital capacity (p = .01) but was not related to inflammation of the upper airways as assessed by cell counts of polymorphonuclear neutrophils. Hydroxyl radical attack subsequent to ambient ozone occurs in the upper airways of healthy children and is related to lung function decrements.

Air Pollutants↗
PubMed2001

Future UV radiation in Central Europe modelled from ozone scenarios.

Photobiologically and photochemically relevant UV radiation for the time around the years 2015 and 2050 is estimated by radiative transfer calculations using variable ozone content based on model simulations. The future cloud conditions are assumed unchanged. Assuming various emission scenarios of chlorfluorohydrocarbons (CFCs) and other trace gases, and taking into account future temperature development and changing atmospheric dynamic conditions, ozone values are simulated. On the basis of these data, three different scenarios of the future total ozone content over Central Europe are analysed, which represent from current knowledge, probable as well as optimistic (high ozone and low UV irradiance) and pessimistic (low ozone and high UV irradiance) conditions. According to these scenarios the future development of the UV radiation is expected not to follow the increasing trend of UV irradiation observed during the last three decades. The predicted changes are highly variable with season. During late winter and spring, the enhanced recent UV values will persist for the next decades. Till 2015 a further slight increase is predicted for springtime. In contrast, during summer and fall, the UV level is assumed to remain on the recent level. For 2050 a decrease to values close to that of an anthropogeneous nearly undisturbed ozone chemistry, as it was found around 1970, is predicted. In addition to average long-time variations of the UV irradiance, short-time increase may occur due to ozone minihole events or due to a large volcanic eruption. The latter can produce a marked increase in UV radiation for several months. During ozone minihole events, with maximum occurrence in spring, UV irradiance is typically increased for a few days. Such episodes must be taken into account additionally to the average UV development. They will occur also in the future and result in UV radiation increases against undisturbed conditions, which are similar to present minihole events. These differences are much larger than the average changes predicted for future ozone development.

Europe↗
PubMed2001

Ozone removal in the sampling of parts per billion levels of terpenoid compounds: an evaluation of different scrubber materials.

Some reactive volatile organic compounds (VOCs) are prone to degradation during sampling in an ozone-rich environment. A wide variety of different chemicals have been used to remove the ozone prior to sampling, but the possibility of interference by such chemicals with the sampled VOCs has not been thoroughly examined. In the present investigation, the retention/degradation of four terpenes (alpha-pinene, beta-pinene, 3-carene, and limonene) and isoprene together with some of their oxidation products (alpha-pinene oxide, nopinone, 4-acetyl-1-methylcyclohexene (AMCH), methylglyoxal, and methacrolein) has been studied, using various ozone-removing chemicals in an attempt to evaluate their potential as ozone scrubbers in the sampling of ambient air. The chemicals included in this first screening and their ozone-removing capacity are as follows: KI, MnO2, and Na2SO3 removed ozone for more than 24 h when exposed to 73-78 ppb (150-160 microg/m3) at a sampling flow rate of 500 mL/min. Silanized poly(1,4-phenylene sulfide) (PFS) removed ozone for 5 h, unsilanized PFS removed ozone for 1 h and 50 min, and Na2S2O3 removed ozone for 20 min. The recovery of the selected compounds with the different scrubbers was >95% for all compounds for KI; >95% for the terpenes oxidation products; >90% for the terpenes and isoprene for PFS; >90% for the terpenes and isoprene for MnO2 on copper nets, Na2SO3, and Na2S2O3; and <90% for the terpenes and isoprene for carulite (a commercial mixture between MnO2, CuO, and Al2O3), CuO, and indigo carmine.

Air Pollutants↗