Ozone as a Tobacco Toxicant

Ozone is very toxic to tobacco, causing serious injury in greenhouses and fields. Certain varieties, differing in sensitivity, have proved useful as indicators of the presence, and to some extent the level, of air-polluting ozone. Environmental factors alter plant response to ozone and must be taken into account. What is now recognized as typical ozone injury to tobacco was first observed in Connecticut in 1951, Maryland in 1952, eastern North Carolina in 1953, and Ontario, Canada, in 1955. Cracking of rubber strips exposed daily at six locations in 1959 in the Connecticut Valley showed ozone concentrations were highest the day before a fleck outbreak, resulting in more than a million dollar loss. Measurement with a Mast ozone recorder from July to mid-October for two seasons at Beltsville, Md., six miles northeast of the District of Columbia, indicated 2.5 pphm as the average daily maximum value, 5 pphm as the level when plant injury is expected, and 10 pphm as very high and infrequent. The neutral buffered Kl method indicated higher ozone values, but about 15 pphm was maximum with this method. Shading portions of leaves for three hours in midday prevented ozone injury. Increased injury in the different tobacco areas was related to increased culture of more susceptible varieties. Although various antiozonants applied to the leaf, or even applied to cloth shade, reduce damage, the development of resistant tobaccos has proved the better means of control. Premature senescence and related chlorosis as well as fleck were prevented by carbon-filtered air, indicating that ozone may be a more important toxicant than previously recognized. Possibly oxidants other than ozone contributed to plant injury, but, if present, they were removed by carbon-filters. Growth of an ozone-sensitive tobacco Bel-W3, as indicated by dry weight, was only half as much in ambient as in carbonfiltered air in one experiment with chambers continued for 5 weeks. Evidence of synergistic action of sulfur dioxide and ozone is reported. Subthreshold concentrations of these toxicants produced injury following exposure of tobacco to mixed gases, whereas no injury resulted from the same concentration of the individual gases.     

Ozone Injury to Pinus Strobus

In a study of the ozone-induced needle blight of eastern white pine in central New York, acute injuries naturally induced on field trees during a year of relatively low ozone concentrations (1 966) were compared with injuries induced during a year of higher concentrations (1967). Injuries were more frequent and severe and were associated with higher mean ozone concentrations in 1967 than in 1966. Characteristic symptoms were induced on foliage of pine branches exposed to controlled doses of ozone as low as 7 ± 1 pphm for four hours or 3 ± 1 pphm for 48 hours. Such doses were equalled or exceeded two and four times, respectively, in the field during the 1 967 season. Ozone sensitivity of pine needle tissue was increased by fumigation in atmospheres containing water mist. High concentrations of ozone (40-60 pphm) caused general injury of foliage of both ozone-susceptible and resistant trees; the symptoms were unlike those found in the field or caused by fumigation with low concentrations of ozone.     

Response of Bean and Tobacco to Ozone: Effect of Light Intensity,Temperature and Relative Humidity

Pinto bean (Phaseolus vulgaris, L.) and Bel W₃ tobacco (Nicotiana tabacum, L.) were grown and exposed to 40 pphm ozone for 1 hr under a range of light intensities, temperatures, and relative humidities. Foliar injury to the more sensitive plant leaves was determined on the third day after exposure. Each atmospheric factor was independently assessed. Two significant three-way interactions were found: exposure light intensity by growth light intensity by species, and growth temperature by exposure temperature by species. Three significant two-way interactions were found for humidity: growth humidity by exposure humidity, growth humidity by species, and exposure humidity by species. The sensitivity of each species to ozone changed with changes in each environmental condition.     

Increasing interannual and altitudinal ozone mixing ratios in the Catalan Pyrenees

Interannual, seasonal, daily and altitudinal patterns of tropospheric ozone mixing ratios, as well as ozone phytotoxicity and the relationship with NO_x precursors and meteorological variables were monitored in the Central Catalan Pyrenees (Meranges valley and Forest of Guils) over a period of 5 years (2004–2008). Biweekly measurements using Radiello passive samplers were taken along two altitudinal transects comprised of thirteen stations ranging from 1040 to 2300 m a.s.l. Visual symptoms of ozone damage in Bel-W3 tobacco cultivars were evaluated biweekly for the first three years (2004–2006). High ozone mixing ratios, always above forest and vegetation protection AOT40 thresholds, were monitored every year. In the last 14 years, the AOT40 (Apr–Sept.) has increased significantly by 1047 μg m^?3 h per year. Annual means of ozone mixing ratios ranged between 38 and 67 ppb_v (38 and 74 ppb_v during the warm period) at the highest site (2300 m) and increased at a rate of 5.1 ppb_v year^?1. The ozone mixing ratios were also on average 35–38% greater during the warm period and had a characteristic daily pattern with minimum values in the early morning, a rise during the morning and a decline overnight, that was less marked the higher the altitude. Whereas ozone mixing ratios increased significantly with altitude from 35 ppb_v at 1040 m–56 ppb_v at 2300 m (on average for 2004–2007 period), NO₂ mixing ratios decreased with altitude from 5.5 ppb_v at 1040 m–1 ppb_v at 2300 m. The analysis of meteorological variables and NO_x values suggests that the ozone mainly originated from urban areas and was transported to high-mountain sites, remaining aloft in absence of NO. Ozone damage rates increased with altitude in response to increasing O₃ mixing ratios and a possible increase in O₃ uptake due to more favorable microclimatic conditions found at higher altitude, which confirms Bel-W3 as a suitable biomonitor for ozone concentrations during summer time. Compared to the valley-bottom site the annual means of ozone mixing ratios are 37% larger in the higher sites. Thus the AOT40 for the forest and vegetation protection threshold is greatly exceeded at higher sites. This could have substantial effects on plant life at high altitudes in the Pyrenees.     

Synoptic weather patterns and their relationship to high ozone concentrations in the Taichung Basin

Frequent high ozone days (defined as daily maximum ozone concentration ⩾80 ppb) during recent years in the Taichung Basin have caused much concern. High ozone days occur mainly during autumn and spring. Statistically, there is no clear linear relationship between a single meteorological variable and ozone concentration. In this study, data from 1996–2000 has shown that high ozone concentrations occur during two types of synoptic weather patterns. The first type is a continental cyclone emanating from mainland China, the southern part of it swept towards Taiwan by easterly winds. The second pattern is a tropical depression moving northwards toward the region, the northern part of it affecting Taiwan via easterly winds. Both types cover Taiwan with easterly winds, which are blocked by the Central Mountain Ranges (altitude of 2000–3000 m). The ranges create lee cyclogenesis to the west, which is unfavorable for pollutant dispersion and leads to serious air pollution episodes.The statistical results of the synoptic weather patterns in relation to ozone concentrations are based on the 5 yr data (1996–2000). This was obtained from a network of air-pollution monitoring sites in the study area, while the vertical data come from two 3-day tethersonde experimental campaigns conducted during March and October 2000, measuring air pressure, air temperature, relative humidity, wind speed and direction, non-methane hydrocarbons, NO_x and O₃.     

The Effect of Water Vapor on Ozone Synthesis in the Photo-oxidation of Alpha-pinene

A study of the effect of water vapor on the photochemical system NO₂ + alphapinene + hv was conducted. A Hotpack Environmental Room was used as a constant temperature chamber, a bank of ultraviolet and fluorescent lamps as a source of simulated solar radiation, and a 150-liter FEP Teflon bag as a reaction vessel. Representative concentrations of 10 pphm NO₂ and 50 pphm alphapinene were used in a 3 × 2 × 2 factorial design where absolute humidities of 0.0000, 0.0090, 0.01 80 g H₂O/g dry air were varied.

Matheson zero air was passed through a clean air train and used as the diluent. Nitrogen dioxide was added to the reaction mixture by a permeation tube, and water and alpha-pinene by evaporation techniques.

Variables measured as a function of time over a 2-hour irradiation period were total oxidants (Mast Ozone Meter), condensation nuclei (General Electric Small Particle Detector), ozone (Regener Chemiluminescent Ozone Meter), nitrogen dioxide and nitric oxide (Technicon Autoanalyzer), and alpha-pinene (Perkin- Elmer Model 800 gas chromatograph).

Upon irradiation, systems containing nitrogen dioxide and alpha-pinene formed oxidants, ozone, condensation nuclei, and nitric oxide. Based on the differences between simultaneous oxidant and ozone measurements, the formation of peroxide- like compounds may be inferred. During the course of the irradiation, nitrogen dioxide and alpha-pinene were consumed. The concentration-time profiles of all variables were characteristic of those exhibited by typical photochemical smog systems.

An effect of water vapor on the systems studied was demonstrated. Increasing humidity decreased net mean/time oxidant and ozone production and net maximum condensation nuclei production. These effects were significant at a 0.05 confidence level. Effects of water on average mean/time NO₂, NO, and alphapinene concentrations were insignificant at this level. The oxidant to ozone ratio was found to decrease with increasing humidity.

The significant decreases in net oxidant and ozone production and NO₂ consumption with increasing water vapor concentration in systems of nitrogen dioxide alone, suggests that water manifests an effect on pertinent inorganic reactions, and the data also suggest additional water participation in the organic reactions.     

Importance of Moisture on Stomatal Behavior Of Plants Subjected to Ozone

The stomatal resistance, measured with a ventilated diffusion porometer at various times before, during, and after exposure to 20–25 pphm ozone, was followed in water-stressed or well-watered beans, beans exposed at either low (37%) or high (73%) atmospheric humidity, and two tobacco cultivars exposed at the same two humidities. The two tobacco cultivars that were compared were the 0₃-susceptible Bel W-3 and the 0₃-resistant Consolidated L. The stomata of the water-stressed but unwilted bean plants closed quickly from a resistance of 2.9 ± 0.3 sec/cm to 8.4 ± 1.0 sec/cm when exposed to O₃ whereas those in the unstressed plants closed slowly from a resistance of 2.5 ± 0.6 sec/cm to 5.2 ± 0.8 sec/cm after exposure to O3 for 10 min. Exposure to 0₃ for 30 min in the moist atmosphere caused no change in stomatal resistance of the bean plants whereas in the dry atmosphere the stomata closed from a resistance of 3.7 ± 0.4 sec/cm to 6.7 ± 0.6 sec/cm, but opened again when ozonation was terminated. With tobacco exposed to O₃ in a dry atmosphere the stomata of the 0₃-resistant cultivar closed more rapidly than the 0₃-susceptible variety, whereas in a moist atmosphere the stomata of both cultivars closed slowly and equally during the 60 min of ozonation.     

Nitrogen Dioxide and Nitric Oxide in Non-Urban Air

Measurement of NO₂ and NO has been carried out in Piedmont, N. C. and in the southern Appalachian Mountains. Average values for the Piedmont were: continuous NO₂ measured 30 ft above surface, 0.76 pphm (14.3 μg/m³), 1 20 ft, 0.61 pphm (11.5 μg/m³); simultaneous values (also Piedmont) (2-hr discrete samples) taken at an earlier time at 4 ft, NO₂, 0.56 pphm (10.6 μg/m³), NO, 0.19 pphm (2.34 μg/m³). The mountain top values (5120 ft, 1573 m) were: NO₂, 0.46 pphm (6.4 μg/m³), NO, 0.26 pphm (2.72 μg/m³). The results of this study furnish further proof that tropospheric NO and NO₂ are produced at the surface of the earth. Data obtained are consistent with the belief that a major sink for NO_x is reaction with O3 and ultimate conversion to nitrate.

Ozone values frequently increased and NO_x values decreased ahead of cold fronts, probably as a result of deep vertical mixing. Also, in small scale turbulence the changes in NO_x values and in the O₃ values tended to be “out of phase,” i.e., as O₃ concentration increased, NO_x concentration decreased and vice versa. Values of NO_x from Green Knob, N. C. (mountain top) also tended to be higher at times when O₃ values were lowest.

The NO₂ hourly average values in Piedmont, N. C, demonstrated a diurnal cycle reminiscent of diurnal urban changes. An early morning peak was followed by a minimum in mid-afternoon. Next, the values rose to a broad evening peak and then decreased slowly during the night. Reported urban concentrations are usually about ten times those found in Piedmont, N. C.     

A New Method for Determining the Contribution of a Refinery to Local SO2 Levels in an Industrial Region

A new method was developed for determining the contribution of one pollutant source to the air quality in an industrialized region. Although the method is general, it is presented in reference to a 130,000 bbl/day petroleum refinery and its effect on ambient SO₂ concentrations in Sarnia, Ontario. The plumes from SO₂ emitters located upwind of the refinery were represented by a single hypothetical plume which influences monitoring stations located upwind as well as downwind from the refinery. However, the refinery emissions affect only the downwind stations. A simple equation was derived by means of which the concentration at the downwind station could be calculated from the concentration at the upwind station and the refinery emission. This equation contains two coefficients A and B which were evaluated such that the difference between the cumulative frequency distributions of the measured and calculated SO₂ concentrations at the downwind station was minimized. For the meteorological conditions and monitoring stations considered, it was found that the refinery contributed less than 4.5 pphm to ambient SO₂ concentrations over 1 hr periods. This result and the validity of the method are discussed.     

Ozone Suppression of White Pine Net Photosynthesis

Reduction in rates of net photosynthesis following exposure to ozone was observed in eastern white pine saplings prior to the development of visible injury. Branches exposed to consecutive doses of 50–80 pphm ozone for 4 hr and 80–90 pphm ozone for 3 hr appeared to have suppressed net photosynthetic rates but results were confounded by diurnal rate variation. Photosynthetic rates of treated branches returned to normal levels following this initial ozone exposure. A second ozonation involving dosages of 90–100 pphm for 5 and 3 hr was sufficient to reduce rates of net photosynthesis by approximately 80 percent.     

Trends in near-surface ozone concentrations in Switzerland: the 1990s

A time series analysis of ozone monitoring data from several locations in Switzerland from 1991 to 1999 is presented. Different methods are used to address changes in the ozone level during these years and to account for the influence of changing meteorological conditions. The results show a slight decrease of the peaks but a highly significant increase of the mean value of around 0.5–0.9 ppb yr⁻¹. The frequency distribution has changed in the sense that very low values have become less frequent and that there is a strong increase in frequency of occurrence of half-hourly mean values between about 45 and 55 ppb. A selection procedure reveals slight tendencies towards different trends of afternoon ozone peaks in summer depending on weather and pollution situations. Ozone peaks tend to decrease on fair weather days at rural sites (but increase at urban sites) and show a small increase on cloudy and windy days. A non-linear regression model is used to estimate trends of summertime afternoon ozone peaks in the presence of meteorological variability. In the model, the long-term signal is additively split into a linear part and a part which is modulated by global radiation. The coefficients for both terms are statistically significant at many sites, with an increasing linear trend at the sites north of the Alps of around 1 ppb yr⁻¹ and a decrease of ozone peaks under fair weather conditions relative to cloudy conditions. When additionally considering the effect of precursor concentrations in the regression models, both trends are weakened, which means that they can partly be explained by changes in local to regional emissions. However, at the sites north of the Alps remains a tendency towards a positive linear “base trend” of around 0.4 ppb yr⁻¹. This could possibly be due to increasing background ozone concentrations.     

Long term changes in nitrogen oxides and volatile organic compounds in Toronto and the challenges facing local ozone control

Ground level ozone represents a significant air quality concern in Toronto, Canada, where the national 65 ppb 8-h standard is repeatedly exceeded during the summer. Here we present an analysis of nitrogen dioxide (NO₂), ozone (O₃), and volatile organic compound (VOC) data from federal and provincial governmental monitoring sites from 2000 to 2007. We show that summertime VOC reactivity and ambient concentrations of NO₂ have decreased over this period of time by up to 40% across Toronto and the surrounding region. This has not resulted in significant summertime ozone reductions, and in some urban areas, it appears to be increasing. We discuss the competing effects of decreased ozone titration leading to an increase in O₃, and decreased local ozone production, both caused by significant decreases in NO_x concentrations. In addition, by using local meteorological data, we show that annual variability in summer ozone correlates strongly with maximum daily temperatures, and we explore the effect of atmospheric transport from the southwest which has a significant influence on early morning levels before local production begins. A mathematical model of instantaneous ozone production is presented which suggests that, given the observed decreases in NO_x and VOC reactivity, we would not expect a significant change in local ozone production under photochemically relevant conditions. These results are discussed in the context of Toronto's recent commitment to cutting local smog-causing pollutants by 20% by 2012.     

Study of atmospheric ozone formation by means of a neural network-based model

The occurrence of high ozone levels in the atmosphere of urban areas has become a serious pollution problem in a number of large cities in the world. Although mathematical models have been proposed for predicting ozone concentrations as a function of a number of gas components, sometimes there are uncertainties due to lack of the combined effects of meteorological factors and the complex chemical reaction system involved. The application of neural network models, based on measured values of air pollutants and meteorological factors at different locations within the S?o Paulo Metropolitan Area, combine chemical and meteorological information. This has shown to be a promising tool for predicting ozone concentration. Simulations carried out with the model indicate the sensitivity of ozone in relation to different air pollution and weather conditions. Predictions using this model have shown good agreement with measured values of ozone concentrations.     

Effects of the density of meteorological observations on the diagnostic wind fields and the performance of photochemical modeling in the greater Seoul area

The high ozone episode in the greater Seoul area (GSA) for the period of 27 July–1 August 1997 was modeled by the California Institute of Technology (CIT) three-dimensional photochemical model. During the period, ozone concentrations around 140 ppb were observed for 2 days. Two sets of diagnostic wind fields were constructed by using observations from the weather stations operated by the Korea Meteorological Administration. One set of wind fields utilized only observations from the surface weather stations (SWS) and the other set also utilized observations from the automatic weather stations (AWS) that were more densely distributed than the SWS. The results showed that utilizing observations from the AWS could represent fine variations in the wind field such as those caused by topography. A better wind field gave a more reasonable spatial distribution of ozone concentrations. The model performance of ozone prediction was also improved to some extent, but only marginally acceptable owing to large day-to-day variations. Overshoots of primary pollutants particularly for NO₂ were observed as pollutants were accumulated where low wind speeds were maintained. More precise information on diurnal and daily variations in emissions was warranted in order to better model the photochemical phenomena over the GSA.     

The influence of tropospheric ozone on the air temperature of the city of Toronto,Ontario, Canada

Weekday/weekend variations in tropospheric ozone concentrations were examined to determine whether ground-level greenhouse gases have a significant impact on local climate. The city of Toronto, Canada, was chosen due to a high volume of commuter traffic and frequent exposure to high ozone episodes. Due to day-of-the-week variations in commuter traffic, ozone concentrations were shown to vary significantly between weekdays and weekends. During high ozone episodes weekend air temperatures were significantly higher than those observed on weekdays. As no meteorological phenomenon is known to occur over a 7 day cycle the observed temperature variations were attributed to anthropogenic activity.     

Systematic Development of an Artificial Neural Network Model for Real-Time Prediction of Ground-Level Ozone in Edmonton,Alberta, Canada

Abstract

Ground-level ozone is a secondary pollutant that has recently gained notoriety for its detrimental effects on human and vegetation health. In this paper, a systematic approach is applied to develop artificial neural network (ANN) models for ground-level ozone (O₃) prediction in Edmonton, Alberta, Canada, using ambient monitoring data for input. The intent of these models is to provide regulatory agencies with a tool for addressing data gaps in ambient monitoring information and predicting O₃ events. The models are used to determine the meteorological conditions and precursors that most affect O₃ concentrations. O₃ time-series effects and the efficacy of the systematic approach are also assessed. The developed models showed good predictive success, with coefficient of multiple determination values ranging from 0.75 to 0.94 for forecasts up to 2 hr in advance. The inputs most important for O₃ prediction were temperature and concentrations of nitric oxide, total hydrocarbons, sulfur dioxide, and nitrogen dioxide.     

Origin of Bel-W3, Bel-C and Bel-B tobacco varieties and their use as indicators of ozone

Since 1962, the tobacco variety Bel-W3 (Nicotiana tabacum L.), has been used in many countries as an indicator of the presence of phytotoxic concentrations of O(3). It is super-sensitive to O(3) and may produce easily recognizable symptoms for several weeks on the new, fully expanded leaves. Bel-B and Bel-C, tolerant and sensitive to O(3), respectively, are sometimes used along with Bel-W3. Information is provided on the origin and nature of these varieties. This includes their use as indicators of elevated O(3) concentrations, strength and limitations, and the inheritance and nature of resistance to O(3) in Bel-B. The varieties were the product of research initiated in 1957 to determine the cause and to reduce losses from tobacco weather fleck. Bel-C and Bel-B display the classical upper leaf surface injury; whereas, Bel-W3 develops primarily bifacial lesions. Data are provided to show differences in the amounts of acute and chronic injury on each variety when exposed to different O(3) exposure doses in controlled environments and under field conditions. There is discussion of the influence of environmental factors on response to O(3) by the varieties and the possibility of synergistic action of O(3) and SO(3) when tobacco is exposed to mixtures of these gases. The methods and results obtained with Bel-W3 in the Dutch National Monitoring Network for Air Pollution are presented in detail. Use of Bel-W3 world-wide as an indicator of elevated O(3) concentrations has been a significant factor in increasing the awareness of O(3) as a pollutant.     

Surface ozone measurements and meteorological influences in the urban atmosphere of Istanbul

Hourly measurements of ozone concentration in the urban atmosphere of Istanbul were carried out from February 1998 to July 1999. An assessment of the annual variations and relationships of ozone concentrations and meteorological variables was made. Annual variations were first examined without considering meteorological variables, and meteorological influences on ozone seasonal values were then examined. Furthermore, a typical ozone threshold period was analysed by considering meteorological variables for a case study. Meteorological conditions favourable for high ozone concentrations appeared when Istanbul and its surrounding region were dominated by an anticyclonic pressure system. During conducive ozone days, southerly and southwesterly winds with low speeds (daytime mean value <11m1sSUP align=right>-1) influence Istanbul.     

Variations of surface O3 in August at a rural site near Shanghai: influences from the West Pacific subtropical high and anthropogenic emissions

Large day-to-day variability in O₃ and CO was observed at Chongming, a remote rural site east of Shanghai, in August 2010. High ozone periods (HOPs) that typically lasted for 3?C5?days with daily maximum ozone exceeding 102?ppb were intermittent with low ozone periods (LOPs) with daily maximum ozone less than 20?ppb. The correlation analysis of ozone with meteorological factors suggests that the large variations of surface ozone are driven by meteorological conditions correlated with the changes in the location and intensity of the west Pacific subtropical high (WPSH) associated with the East Asian summer monsoon (EASM). When the center of WPSH with weaker intensity is to the southeast of Chongming site, the mixing ratios and variability of surface ozone are higher. When the center of WPSH with stronger intensity is to the northeast of Chongming site, the mixing ratios and variability of surface ozone are lower. Sensitivity simulations using the GEOS-Chem chemical transport model indicate that meteorological condition associated with WPSH is the primary factor controlling surface ozone at Chongming in August, while local anthropogenic emissions make significant contributions to surface ozone concentrations only during HOP.