Long-term Effects Of Ozone Research Articles

Health Effects of Ozone on Respiratory Diseases.

Ozone is known to cause bronchial inflammation and airway hyper-responsiveness via oxidative injury and inflammation. While other ambient air pollutants such as particulate matter (PM) and nitrogen dioxide showed decreasing trends in mean annual concentrations, ozone concentrations have not declined recently in most countries across the world. Short-term exposure to high concentrations of ozone has been associated with increased mortality and cardiovascular and respiratory morbidity in many regions of the world. However, the long-term effects of ozone have been less investigated than the short-term exposure due to the difficulty in modeling ozone exposure and linking between individual exposures and health outcome data. A recently developed model of ozone exposure enabled the investigation of long-term ozone effects on health outcomes. Recent findings suggested that long-term exposure to ozone was associated with an increased risk of cardiovascular and respiratory mortality. Longitudinal studies using large cohorts also revealed that long-term exposure to ozone was associated with a greater decline in lung function and the progression of emphysema. The development of long-term standards for ozone as well as PM should be considered to protect the respiratory health of the general population and people with chronic respiratory diseases.

A National Spatiotemporal Model for Ambient Ozone Concentration in the United States Using Universal Kriging and Land-use Regression: 2005-2014

Accurate prediction models for ambient air pollution concentrations are a key component of modern air pollution epidemiology, and epidemiological studies regarding long-term effects of ozone are urgently needed. Large-scale models are necessary for cohort studies with national recruitment, and models are also needed to accurately characterize fine-scale spatial gradients in a region. We applied a spatiotemporal modeling approach, previously used in individual cities for ozone and nationally for other pollutants, to predict weekly ambient ozone concentration over the contiguous United States for the period from 2005 through 2014. Methods: Using long-term regulatory ozone monitoring data collected daily (n=669 sites) and short-term spatially-rich cohort-specific data collected as two-week time integrated averages (n=1958 sites) divided into nine regions across the country, we fit a regionalized likelihood-based spatiotemporal model using land-use regression on dimension reduced land-use covariates combined with universal kriging. Ten-fold cross-validated predictions, leaving out sites, were used to compute R2 (from root mean-squared error) in three different ways: spatial R2 to assess accuracy in predicting long-term average exposures at locations without data, temporal R2 to assess accuracy in predicting the time series of weekly exposures at locations without data, and spatiotemporal R2 to assess overall prediction accuracy. Results: Overall cross-validated performance was high. Spatial R2 was 0.69, spatiotemporal R2 was 0.78, and median site-specific temporal R2 was 0.80. Spatial performance varied by modeling region and season. Conclusion: We report a novel, successful national-scale spatiotemporal model for outdoor ozone concentrations for the contiguous U.S. Strengths of this model include its national scale and its ability to make accurate fine-scale predictions spatially at all arbitrary points and temporally at one-week intervals, suggesting future usefulness to a wide variety of epidemiological studies.

Drought stress does not protect Quercus ilex L. from ozone effects: results from a comparative study of two subspecies differing in ozone sensitivity

Long-term effects of ozone (O3) exposure and drought stress were assessed on two subspecies of Quercus ilex: ssp. ilex and ssp. ballota. Two-year-old seedlings were continuously exposed for 26 months in open-top chambers to three O3 treatments: charcoal filtered air, non-filtered air and non-filtered air supplemented with 40 nl · l(-1) O3. Additionally, two irrigation regimes were adopted: half of the plants were well-watered and the others received half of the water supplied to control plants. Growth, shoot water potential and gas exchange rates were assessed seasonally, and biomass accumulation was determined at the end of the experiment. Drought stress caused higher reductions of gas exchange, growth and biomass accumulation than O3 exposure in both subspecies. The combination of O3 and drought stress caused further decreases of accumulated aboveground biomass but no additive effects were observed on gas exchange rates or root biomass. Thus, drought stress did not protect Q. ilex from O3 effects on biomass when the response of the whole plant was considered. Q. ilex ssp. ballota was more sensitive to O3 and ssp. ilex was more affected by drought stress. The different O3 sensitivity was not only related to pollutant uptake but also to the ability of plants for resource acquisition and allocation. Based on biomass dose-response functions, Q. ilex is more resistant to O3 than other European evergreen tree species, however, O3 represents an additional stress factor that might be impairing plant ability to withstand current and future climate change.

Long-term effects of ozone on CO2 exchange in peatland microcosms

Abstract Effects of elevated tropospheric ozone concentration on the CO2 exchange of peatland microcosms and the photosynthetic capacity of the dominating sedge, Eriophorum vaginatum, were studied in a four-year open-field experiment. The net ecosystem CO2 exchange and the dark respiration rate of the microcosms were measured with the closed chamber method. The CO2 assimilation rate and chlorophyll fluorescence (maximal photochemical efficiency of PSII, Fv/Fm) of E. vaginatum leaves were also measured. The gross photosynthesis rate of the microcosms was transiently decreased by ozone exposure during the first year. During the fourth year, the gross photosynthesis and dark respiration rate were both slightly increased by ozone exposure but this was due to the increased density of sedge leaves and no difference was found in Fv/Fm. In overall, chronic ozone exposure had only slight effect on the CO2 exchange of the peatland microcosms.

The effects of tropospheric ozone on the species dynamics of calcareous grassland

Although ozone has been shown to reduce the growth of individual species and to alter the composition of simple species mixtures, there is little understanding of its long-term effects on species dynamics and composition in real communities. Intact turfs of calcareous grassland were exposed to four different ozone regimes in open-top chambers over three consecutive summers. Treatments provided a mean seasonal AOT40 ranging from approximately zero to 15 ppm h. Cumulative ozone exposure was a significant factor in compositional change, but only explained 4.6% of the variation. The dominant grass species ( Festuca rubra) showed a consistent decline in cover in the high ozone treatment over time and the forb Campanula rotundifolia was lost from all three ozone treatments. The frequency of some species ( Galium verum and Plantago lanceolata) increased with ozone exposure. Long-term effects of ozone on species composition in chalk grassland may be a function of both the sensitivity of individual species and the response of the dominant species.

Design and performance of a free-air exposure system to study long-term effects of ozone on grasslands

Studying long-term effects of ozone on perennial plant communities in situ is difficult because of the need for large observation plots and long exposure times, and because of confounding effects of altered microclimatic conditions in most systems. A novel free-air fumigation system was designed for multi-year exposures of semi-natural grassland plots to either ambient or elevated ozone concentrations at a Swiss sub-alpine site. The system operates by releasing ozone-enriched air from either one of two 120° sectors, placed in each of the two main wind directions. Ozone-enriched air is rapidly mixed with ambient air behind a small transparent windscreen mounted at canopy height around the 7-m diameter circular plots. Ozone generation and dispensing during daylight hours is PC controlled and depends upon wind speed, wind direction and ambient ozone. In 2001, from April to October fumigation was possible during 85% of the time. The ozone-enrichment factor (EF, [O 3] enriched/[O 3] control) in ozone plots relative to control plots averaged 1.48 (±0.24 SD), and EF was highest with winds of around 2 m s −1. The seasonal cumulative ozone exposure (AOT40) at canopy level was 5 ppm h in the control and 30 ppm h in the ozone-treated plots, with less than 10% variation between replicates, and 13 ppm h in ambient air at 2 m. Variation in ozone across the plot-diameter was <5% for 24-h mean concentrations, but differed by a maximum of 20% in terms of AOT40. There was no difference in microclimatic conditions between experimental plots and ambient conditions. It is concluded that the system is suitable for long-term ozone experiments at relatively low running costs, but that the variation in ozone distribution across the plots may lead to systematic differences in cumulative exposure over longer periods of time which need to be taken into account when relating exposure to biological effects.

Ecological issues related to ozone: agricultural issues

Research on the effects of ozone on agricultural crops and agro-ecosystems is needed for the development of regional emission reduction strategies, to underpin practical recommendations aiming to increase the sustainability of agricultural land management in a changing environment, and to secure food supply in regions with rapidly growing populations. Major limitations in current knowledge exist in several areas: (1) Modelling of ozone transfer and specifically stomatal ozone uptake under variable environmental conditions, using robust and well-validated dynamic models that can be linked to large-scale photochemical models lack coverage. (2) Processes involved in the initial reactions of ozone with extracellular and cellular components after entry through the stomata, and identification of key chemical species and their role in detoxification require additional study. (3) Scaling the effects from the level of individual cells to the whole-plant requires, for instance, a better understanding of the effects of ozone on carbon transport within the plant. (4) Implications of long-term ozone effects on community and whole-ecosystem level processes, with an emphasis on crop quality, element cycling and carbon sequestration, and biodiversity of pastures and rangelands require renewed efforts. The UNECE Convention on Long Range Trans-boundary Air Pollution shows, for example, that policy decisions may require the use of integrated assessment models. These models depend on quantitative exposure–response information to link quantitative effects at each level of organization to an effective ozone dose (i.e., the balance between the rate of ozone uptake by the foliage and the rate of ozone detoxification). In order to be effective in a policy, or technological context, results from future research must be funnelled into an appropriate knowledge transfer scheme. This requires data synthesis, up-scaling, and spatial aggregation. At the research level, interactions must be considered between the effects of ozone and factors that are either directly manipulated by man through crop management, or indirectly changed. The latter include elevated atmospheric CO 2, particulate matter, other pollutants such as nitrogen oxides, UV-B radiation, climate and associated soil moisture conditions.

Predicting the regional impact of ozone and precipitation on the growth of loblolly pine and yellow-poplar using linked TREGRO and ZELIG models

To simulate the long-term effects of ozone on forests in the US, we linked TREGRO, a mechanistic model of an individual tree, to ZELIG, a forest stand model, to examine the response of forests to five ozone exposure regimes (0 to ∼100 ppm h SUM06 per year) in 100-year simulations. TREGRO and ZELIG were parameterized using biological and meteorological data from three climate sites in the southeastern US. TREGRO was used to generate 3-year exposure–response relationships between ozone and growth of loblolly pine ( Pinus taeda L.) and yellow-poplar ( Liriodendron tulipifera L.). Ratios (response at ozone exposure: response at base case) of total tree mass, leaf mass, and fine root/leaf mass were calculated and used to modify growth functions in ZELIG. At the end of the ZELIG simulation, the change in basal area of loblolly pine ranged from an increase of 44% to a decrease of 87%, depending on precipitation and ozone exposure. The basal area of yellow-poplar, simulated in competition with loblolly pine was not affected over most of its range. Over the range of the two species, the simulated changes in basal area due to ozone exposure were generally within ±10% of the base case. Competitive interactions between the species were not altered.

Ozone threshold doses and exposure-response relationships for the development of ozone injury symptoms in wild plant species.

The relative ozone sensitivities of 25 German native herbaceous plant species, representative of arable field margins or disturbed habitats, were examined over three consecutive growing seasons. Plants were grown from seed, potted into natural soils and exposed in open-top chambers for the entire season to different ozone-exposure regimes covering a range of concentrations from <5 to 48 ppb (seasonal 8 h daily mean). The assessment of ozone effects was carried out by recording the first day of visible symptom appearance and the percentage of injured leaves at the end of vegetative growth. Species exhibited contrasting patterns of symptom expression under ozone stress, with either ozone-specific symptoms or ozone-enhanced foliar pigmentation and senescence. Classifications of species according to their ozone susceptibility varied depending on whether measurement was of the total extent of visible injury, ozone threshold doses for the incidence of symptoms, or modelled exposure-response relationships. The most sensitive species exhibiting ozone-specific symptoms were Cirsium arvense and Sonchus asper, which responded to accumulated ozone exposures <1500 ppb.h (AOT40). For these and three other species, an AOT40 peak of a single day was found to be responsible for the incidence of ozone-specific symptoms, i.e. injury occurred rapidly within a few days of the day with the highest AOT40, while other species responded only to longer-term ozone exposures. The relative ozone sensitivity of the species was calculated by combining the different sensitivity criteria, and possible systematic trends (taxonomic or evolutionary features) are pointed out. The results suggest it may be possible to use a particular group of native herbaceous plant species with contrasting patterns of ozone sensitivity as a biomonitoring system in the field. This allows plant responses to be related either to peak values or to prolonged ozone exposure, making it possible to distinguish between short- and long-term effects of ozone.

Long-term effects of ozone on Fagus sylvatica L. ? An open-top chamber exposure study

The Landesumweltamt North-Rhine Westfalia is operating eight open-top chambers as well as six reference plots at a site on a westerly exposed slope (540 m a.s.) in the Egge mountains, 130 km northeast of the Ruhr area. Since 1991 eighteen 6 yr old beech trees (Fagus sylvatica L.) per plot/chamber were exposed either to ambient air (AA), non-filtered air (NF) or charcoal-filtered air. Ambient air pollutants (O3. SO2, NOx) as well as meteorological parameters were monitored continuously inside chambers as well as in the ambient. Growth parameters (bud development, stem diameter, shoot length, shoot diameter, leaf area, leaf colouration, leaf abscission) were assessed over the years 1992–1994.

Combined Use of Ozone and Granular Activated Carbon (GAC) in Potable Water Treatment; Effects on GAC Quality After Reactivation

Abstract Common processes in potable water treatment regarding dissolved organics removal (natural organic matter, NOM, and organic micropollutants, OMP) include oxidation techniques – like ozonation -and adsorption onto granular activated carbon (GAC). This paper deals with combined ozonation and GAC filtration. Effects on water quality are discussed: partial oxidation of dissolved organics by ozone, leading to changing adsorption behavior and enhanced biodegradation in GAC columns. Special emphasis is laid on long term effects of ozone on GAC quality after several thermal reactivations. Long term experience indicates that ozonation prior to GAC filtration, leading to moderate ozone concentrations in the GAC influent, does not influence GAC quality negatively, even after more than ten reactivation cycles.

Effects of ozone and simulated acidic precipitation on above- and below-ground growth of loblolly pine (Pinustaeda)

Loblolly pine (Pinustaeda L.) seedlings from two families differing in ozone sensitivity were exposed to four ozone concentrations (charcoal-filtered (subambient ozone concentration), nonfiltered (ambient ozone concentration), non-filtered × 1.7, and nonfiltered × 2.5) and three levels of acidic precipitation (pH = 3.3, 4.3, and 5.3) in modified open-top chambers for one growing season at Auburn, Alabama. Seedlings were planted in the ground in root-exclusion tubes that isolated root systems of individual seedlings. Foliage, stem, and root biomass, three-dimensional root surface area (root surface area × π; in cm3), final height, and groundline diameter were recorded and analyzed. Foliage dry matter and root surface area decreased and root to shoot ratio significantly increased with increasing ozone concentrations for the ozone-sensitive family. There were no significant pH effects for this family. No significant differences in either ozone or pH treatments occurred for the ozone-tolerant family. The possible implications on long-term effects of ozone and acidic precipitation on loblolly pine growth are discussed.