Elevated Ozone Research Articles

Elevated Ozone Modulates Herbivore-Induced Volatile Emissions of Brassica nigra and Alters a Tritrophic Interaction.

Plants damaged by herbivores emit volatile organic compounds (VOCs) that are used by parasitoids for host location. In nature, however, plants are exposed to multiple abiotic and biotic stresses of varying intensities, which may affect tritrophic interactions. Here, we studied the effects of ozone exposure and feeding by Pieris brassicae larvae on the VOCs emitted by Brassica nigra and the effects on oriented flight of the parasitoid Cotesia glomerata. We also investigated the oriented flight of C. glomerata in a wind-tunnel with elevated ozone levels. Herbivore-feeding induced the emission of several VOCs, while ozone alone had no significant effect. However, exposure to 120ppb ozone, followed by 24hr of herbivore-feeding, induced higher emissions of all VOCs as compared to herbivore-feeding alone. In accordance, herbivore-damaged plants elicited more oriented flights than undamaged plants, whereas plants exposed to 120ppb ozone and 24hr of herbivore-feeding elicited more oriented flights than plants subjected to herbivore-feeding alone. Ozone enrichment of the wind-tunnel air appeared to negatively affect orientation of parasitoids at 70ppb, but not at 120ppb. These results suggest that the combination of ozone and P. brassicae-feeding modulates VOC emissions, which significantly influence foraging efficiency of C. glomerata.

Adaptability of Indocalamus decorus to climate change based on physiological and biochemical responses to elevated carbon dioxide and ozone

Carbon dioxide (CO2) and ozone (O3) are important greenhouse gases that contribute to global climate change. The effects of elevated CO2 and/or O3 on plants remain unclear. Plant responses to mixtures of the two gases at high concentrations are likely to be complex. Previous studies have shown that the ability to tolerate elevated levels of the two gases varies among plant species; physiological adaptability in the face of changing atmospheric composition also differs among taxa. However, the effects of mixtures of the two greenhouse gases on the growth and physiology of bamboo are largely unexplored, even though bamboos are important vegetation elements throughout tropical and subtropical regions of the planet. In this study, we used open-topped chambers (OTCs) to double the concentrations of atmospheric CO2 and O3, and examined changes in membrane lipid peroxidation, photosynthetic physiology, and antioxidase activities in Indocalamus decorus leaves. After 103 days of treatment, elevated O3 depressed net photosynthetic rate (Pn) without changing stomatal function, but caused no significant oxidative damage in the leaves. High levels of antioxidase activities were maintained in the leaves, indicating that this species had a strong tolerance to elevated O3. Decreases in reactive oxygen content and antioxidase activity in the leaves highlighted the significant positive effects of elevated CO2 on photosynthesis in I. decorus. When a mixture of both gases was supplied at high concentrations, we detected no oxidative damage, although photosynthetic capacity was reduced. Negative effects of O3 were very marked during the early part of the treatment period, but the effects of CO2 were positive. CO2 mitigated the oxidative damage caused by O3 and promoted the growth of I. decorus. Thus, I. decorus tolerated the two greenhouse gases, and was able to adapt to elevated CO2 and O3 levels. These findings contribute to the current knowledge base on the response of bamboo to global climate change.

Effects of elevated ozone on physiological, anatomical and ultrastructural characteristics of four common urban tree species in China

Fast urbanization has led to ozone (O3) being the main pollutant in summer in most of China. To assess future ground-level O3 effects on the service of urban greening species and clarify the underlying mechanism of O3 damage, four common urban greening species, Ailanthus altissima (AA), Fraxinus chinensis (FC), Platanus orientalis (PO) and Robinia pseudoacacia (RP) were exposed to non-filtered air (NF) and to elevated O3 (E-O3) in open-top chambers. E-O3 induced visible injury in all species as well as microscopic alterations such as collapse of the palisade parenchyma cells, callose accumulation, or chloroplast and mitochondrial accelerated senescence. E-O3 significantly reduced light-saturated CO2 assimilation (Asat), the maximum activity of Rubisco (Vcmax), the maximum electron transport rate (Jmax), and fluorescence parameters such as the quantum yield of noncyclic electron transport (ϕPSII), and the quenching of photochemical efficiency of PSII (qP). It also increased total antioxidant capacity, phenolics and ascorbate contents. No significant interaction between O3 and species was found in photosynthetic performance and antioxidant systems, suggesting that the four species selected were sensitive to O3. Of all four species, AA was the most sensitive species due to a combination of earlier injury onset, anatomical features, lower antioxidant responses and higher stomatal conductance. The sensitivity of tree species to O3 is a factor to be considered for urban greening. Ozone may affect important urban forest ecosystem services by reducing CO2 assimilation.

Combining effects of ozone and carbon dioxide application on photosynthesis of Thai jasmine rice (Oryza sativa L.) cultivar Khao Dawk Mali 105

This research investigated the effects of elevated ozone and carbon dioxide on photosynthesis of rice ('Oryza sativa' L.) cultivar Khao Dawk Mali 105. Seedlings were kept in indoor climate control chambers which were set to typically background level of ozone (<10 ppb) by passing inlet air from outside through charcoal filter prior to enter to the chambers. Plant samples were fumigated by ozone concentration level at 40 ppb, 70 ppb and carbon dioxide concentration level at 700 ppm. For combined effects, elevated carbon dioxide concentration 700 ppm was given into two combination treatments of ozone concentration level at 40 and 70 ppb. Control groups were grown in charcoal-filter chambers with no additional ozone. Plant samples then were fumigated with ozone and carbon dioxide for 28 days at tillering stage (at the rice age of 42 to 70 days), and analyzed weekly for photosynthesis rate, leaf chlorophyll, total soluble sugar and biomass. The results showed that ozone significantly caused reduction in photosynthesis, leaf chlorophyll, total soluble sugar and total biomass of rice. The ozone concentration level of 70 ppb significantly (p <= 0.05) affected rice more than 40 ppb treatment. Nevertheless, elevated carbon dioxide reduced the negative effects of ozone from both ozone concentration levels. Moreover, higher photosynthesis was observed in combined treatment, when compared with the control group. Finally, increasing of ozone caused reduction in rice photosynthesis; however, elevated carbon dioxide could significantly adverse the effects of ozone.

Effects of Elevated Ozone on Stoichiometry and Nutrient Pools of Phoebe Bournei (Hemsl.) Yang and Phoebe Zhennan S. Lee et F. N. Wei Seedlings in Subtropical China

Tropospheric ozone (O3) is considered one of the most critical air pollutants in many parts of the world due to its detrimental effects on plants growth. However, the stoichiometric response of tree species to elevated ozone (O3) is poorly documented. In order to understand the effects of elevated ozone on the stoichiometry and nutrient pools of Phoebe bournei (Hemsl.) Yang (P. bournei)and Phoebe zhennan S. Lee et F. N. Wei (P. zhennan), the present study examined the carbon (C), nitrogen (N), and phosphorous (P) concentrations, stoichiometric ratios, and stocks in foliar, stem, and root for P. bournei and P. zhennan with three ozone fumigation treatments (Ambient air, 100 ppb and 150 ppb). The results suggest that elevated ozone significantly increased the N concentrations in individual tissues for both of P. bournei and P. zhennan. On the contrary, elevated ozone decreased the C:N ratios in individual tissues for both of P. bournei and P. zhennan because the C concentration remained stable under the ozone stress. The P concentration, and C:P and N:P ratios in individual tissues for both P. bournei and P. zhennan did not exhibit consistent variation tendency with elevated ozone. Elevated ozone sharply reduced the total C, N, and P stocks and altered the pattern of C, N, and P allocation for both P. bournei and P. zhennan. The present study suggests that tropospheric ozone enrichment should be considered an important environmental factor on stoichiometry of tree species.

Ozone-Induced Type 2 Immunity in Nasal Airways. Development and Lymphoid Cell Dependence in Mice.

Inhalation exposures to ozone commonly encountered in photochemical smog cause airway injury and inflammation. Elevated ambient ozone concentrations have been epidemiologically associated with nasal airway activation of neutrophils and eosinophils. In the present study, we elucidated the temporal onset and lymphoid cell dependency of eosinophilic rhinitis and associated epithelial changes in mice repeatedly exposed to ozone. Lymphoid cell-sufficient C57BL/6 mice were exposed to 0 or 0.5 parts per million (ppm) ozone for 1, 2, 4, or 9 consecutive weekdays (4 h/d). Lymphoid cell-deficient, Rag2(-/-)Il2rg(-/-) mice were similarly exposed for 9 weekdays. Nasal tissues were taken at 2 or 24 hours after exposure for morphometric and gene expression analyses. C57BL/6 mice exposed to ozone for 1 day had acute neutrophilic rhinitis, with airway epithelial necrosis and overexpression of mucosal Ccl2 (MCP-1), Ccl11 (eotaxin), Cxcl1 (KC), Cxcl2 (MIP-2), Hmox1, Il1b, Il5, Il6, Il13, and Tnf mRNA. In contrast, 9-day ozone exposure elicited type 2 immune responses in C57BL/6 mice, with mucosal mRNA overexpression of Arg1, Ccl8 (MCP-2), Ccl11, Chil4 (Ym2), Clca1 (Gob5), Il5, Il10, and Il13; increased density of mucosal eosinophils; and nasal epithelial remodeling (e.g., hyperplasia/hypertrophy, mucous cell metaplasia, hyalinosis, and increased YM1/YM2 proteins). Rag2(-/-)Il2rg(-/-) mice exposed to ozone for 9 days, however, had no nasal pathology or overexpression of transcripts related to type 2 immunity. These results provide a plausible paradigm for the activation of eosinophilic inflammation and type 2 immunity found in the nasal airways of nonatopic individuals subjected to episodic exposures to high ambient ozone.

Elevated Ozone Deteriorates Grain Quality of Japonica Rice cv. Koshihikari, Even if it Does Not Cause Yield Reduction.

BackgroundIt is becoming clear that ozone affects not only grain yield but also grain quality in rice. However, the biochemical mechanisms responsible for ozone-induced changes in appearance quality or components are poorly understood. We analyzed appearance quality and starch composition in the rice cultivars “Koshihikari” (japonica) and “Kasalath” (indica) grown under elevated ozone conditions.ResultsElevated ozone significantly increased the proportion of immature (mainly chalky) kernels in “Koshihikari” but not in “Kasalath”. Scanning electron microscopy of transverse sections of kernels showed that endosperm starch granules of “Koshihikari” ripened under elevated ozone were loosely packed with large spaces and contained irregular rounded granules. Amylose content was increased in “Koshihikari” kernels with ozone exposure, but was unchanged in “Kasalath” kernels. Distribution analysis of amylopectin chain length showed that ozone induces a decrease of long-side chains and alterations of short side-chains in “Koshihikari” kernels. Furthermore, Starch Synthase (SS) IIIa transcript levels in “Koshihikari” caryopses were decreased by elevated ozone.ConclusionsThe japonica cultivar “Koshihikari” showed significant deterioration in appearance quality of kernels caused by abnormal starch accumulation due to exposure to ozone. The alteration patterns of amylose and amylopectin in ozone-exposed rice kernels are similar to those in rice kernels harvested from SSIIIa-deficient mutants. These findings suggest that the increase of chalky kernels in ozone-treated “Koshihikari” is partly attributable to the repressed expression of SSIIIa involved in amylopectin side-chain elongation with ozone exposure. Elevated ozone reduced appearance quality in “Koshihikari” although it did not impair starch properties contributing to the eating quality of cooked rice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0079-4) contains supplementary material, which is available to authorized users.

Assessing Factors Linked with Ozone Exceedances in Seoul,Korea through a Decision Tree Algorithm

Since prolonged exposure to elevated ozone (O3) concentrations is known to be harmful to human health, appropriate control strategies for ozone are needed for the non-attainment area such as Seoul, Korea. The goal of this research is to assess factors linked with the 1-hour ozone exceedance through a decision tree model. Since ozone is a secondary pollutant, lag times between ozone and explanatory variables for ozone formation are taken into account in the model to improve the accuracy of the simulation. Results show that while ozone concentrations of the previous day and NO2 concentrations in the morning are major drivers for ozone exceedances in the early afternoon, meteorology plays more important role for ozone exceedances in the late afternoon. Results also show that a selection of lag times between ozone and explanatory variables affect the accuracy of predicting 1-hour ozone exceedances. The result analyzed in this study can be used for developing control strategies of ozone in Seoul, Korea.

Forests and ozone: productivity, carbon storage, and feedbacks.

Tropospheric ozone is a serious air-pollutant, with large impacts on plant function. This study demonstrates that tropospheric ozone, although it damages plant metabolism, does not necessarily reduce ecosystem processes such as productivity or carbon sequestration because of diversity change and compensatory processes at the community scale ameliorate negative impacts at the individual level. This study assesses the impact of ozone on forest composition and ecosystem dynamics with an individual-based gap model that includes basic physiology as well as species-specific metabolic properties. Elevated tropospheric ozone leads to no reduction of forest productivity and carbon stock and to increased isoprene emissions, which result from enhanced dominance by isoprene-emitting species (which tolerate ozone stress better than non-emitters). This study suggests that tropospheric ozone may not diminish forest carbon sequestration capacity. This study also suggests that, because of the often positive relationship between isoprene emission and ozone formation, there is a positive feedback loop between forest communities and ozone, which further aggravates ozone pollution.

Divergent responses of methanogenic archaeal communities in two rice cultivars to elevated ground-level O3

Inhibitive effect of elevated ground-level ozone (O3) on paddy methane (CH4) emission varies with rice cultivars. However, little information is available on its microbial mechanism. For this purpose, the responses of methane-metabolizing microorganisms, methanogenic archaea and methanotrophic bacteria to O3 pollution were investigated in the O3-tolerant (YD6) and the O3-sensitive (IIY084) cultivars at two rice growth stages in Free Air Concentration Elevation of O3 (O3-FACE) system of China. It was found that O3 pollution didn't change the abundances of Type I and Type II methanotrophic bacteria at two rice stages. For methanogenic archaea, their abundances in both cultivars were decreased by O3 pollution at the tillering stage. Furthermore, a greater negative influence on methanogenic archaeal community was observed on IIY084 than on YD6: at tillering stage, the alpha diversity indices of methanogenic archaeal community in IIY084 was decreased to a greater extent than in YD6; IIY084 shifted methanogenic archaeal community composition and decreased the abundances and the diversities of Methanosarcinaceae and Methanosaetaceae as well as the abundance of Methanomicrobiales, while the diversity of Methanocellaceae were increased in YD6. These findings indicate that the variations in the responses of paddy CH4 emission to O3 pollution between cultivars could result from the divergent responses of their methanogenic archaea.

Increases in volatile organic compound emissions of Scots pine in response to elevated ozone and warming are modified by herbivory and soil nitrogen availability

Climate change in the boreal forests include, e.g., warming, increased tropospheric ozone concentration, higher nitrogen (N) deposition and increased risk of insect outbreaks. Climate change influences emissions of biogenic volatile organic compounds (BVOCs) affecting plant defense, communication and atmospheric feedbacks. We studied the effects of elevated temperature (ca. 1 °C), elevated ozone (ca. 1.5 × ambient), two soil N availability levels (prevailing and 120 kg N ha−1 a−1) and herbivory on BVOC emission rates, net photosynthesis and resin canals (BVOCs storage), of Scots pine (Pinus sylvestris) seedlings in an open-field exposure in central Finland. Shoot BVOCs were collected in July 2012 within a few days after feeding by larvae of pine-sawfly Acantholyda posticalis, a month later in August, and in May 2013. Elevated temperature caused twofold to fourfold increases in total emissions of non-oxygenated monoterpenes (MTs), oxygenated MTs and sesquiterpenes (SQTs) and several reactive compounds, and higher N enhanced some of these changes. Ozone and higher N together increased emissions of several MTs and total SQTs. Higher number of resin canals and higher net photosynthesis might have contributed to BVOC increases. Herbivory had the strongest effect on SQT emissions (threefold increase) shortly after feeding. In the following spring, herbivory reduced emission rates of some MTs, but also synergistically increased MTs emissions with temperature but suppressed the increase caused by ozone. Results suggest that warming and ozone, particularly in areas with increased soil N availability, can increase BVOC emissions from young boreal forests in the near future, and herbivory may modify these responses.

Plant surface reactions: an opportunistic ozone defence mechanism impacting atmospheric chemistry

Abstract. Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. Plant injuries have been linked to the uptake of ozone through stomatal pores and oxidative damage of the internal leaf tissue. But a striking question remains: can surface reactions limit the stomatal uptake of ozone and therefore reduce its detrimental effects to plants?In this laboratory study we could show that semi-volatile organic compounds exuded by the glandular trichomes of different Nicotiana tabacum varieties are an efficient ozone sink at the plant surface. In our experiments, different diterpenoid compounds were responsible for a strongly variety-dependent ozone uptake of plants under dark conditions, when stomatal pores are almost closed. Surface reactions of ozone were accompanied by a prompt release of oxygenated volatile organic compounds, which could be linked to the corresponding precursor compounds: ozonolysis cis-abienol (C20H34O) – a diterpenoid with two exocyclic double bonds – caused emissions of formaldehyde (HCHO) and methyl vinyl ketone (C4H6O). The ring-structured cembratrien-diols (C20H34O2) with three endocyclic double bonds need at least two ozonolysis steps to form volatile carbonyls such as 4-oxopentanal (C5H8O2), which we could observe in the gas phase, too.Fluid dynamic calculations were used to model ozone distribution in the diffusion-limited leaf boundary layer under daylight conditions. In the case of an ozone-reactive leaf surface, ozone gradients in the vicinity of stomatal pores are changed in such a way that the ozone flux through the open stomata is strongly reduced.Our results show that unsaturated semi-volatile compounds at the plant surface should be considered as a source of oxygenated volatile organic compounds, impacting gas phase chemistry, as well as efficient ozone sink improving the ozone tolerance of plants.

The Effect of Elevated Ozone Concentrations with Varying Shading on Dry Matter Loss in a Winter Wheat-Producing Region in China.

Surface-level ozone pollution causes crop production loss by directly reducing healthy green leaf area available for carbon fixation. Ozone and its precursors also affect crop photosynthesis indirectly by decreasing solar irradiance. Pollutants are reported to have become even more severe in Eastern China over the last ten years. In this study, we investigated the effect of a combination of elevated ozone concentrations and reduced solar irradiance on a popular winter wheat Yangmai13 (Triticum aestivum L.) at field and regional levels in China. Winter wheat was grown in artificial shading and open-top-chamber environments. Treatment 1 (T1, i.e., 60% shading with an enhanced ozone of 100±9 ppb), Treatment 2 (T2, i.e., 20% shading with an enhanced ozone of 100±9 ppb), and Control Check Treatment (CK, i.e., no shading with an enhanced ozone of 100±9 ppb), with two plots under each, were established to investigate the response of winter wheat under elevated ozone concentrations and varying solar irradiance. At the field level, linear temporal relationships between dry matter loss and cumulative stomatal ozone uptake were first established through a parameterized stomatal-flux model. At the regional level, ozone concentrations and meteorological variables, including solar irradiance, were simulated using the WRF-CMAQ model (i.e., a meteorology and air quality modeling system). These variables were then used to estimate cumulative stomatal ozone uptake for the four major winter wheat-growing provinces. The regional-level cumulative ozone uptake was then used as the independent variable in field data-based regression models to predict dry matter loss over space and time. Field-level results showed that over 85% (T1: R2 = 0.85 & T2: R2 = 0.89) of variation in dry matter loss was explained by cumulative ozone uptake. Dry matter was reduced by 3.8% in T1 and 2.2% in T2 for each mmol O3·m-2 of cumulative ozone uptake. At the regional level, dry matter loss in winter wheat would reach 50% under elevated ozone concentrations and reduced solar irradiance as determined in T1, and 30% under conditions as determined in T2. Results from this study suggest that a combination of elevated ozone concentrations and reduced solar irradiance could result in substantial dry matter loss in the Chinese wheat-growing regions.

Detection of protein and DNA damage induced by elevated carbon dioxide and ozone in Triticum aestivum L. using biomarker and comet assay.

This study was designed to compare the genetic effects of elevated carbon dioxide (CO2) and ozone (O3), alone or in combination, under irrigated and non-irrigated conditions on proteins and DNA of wheat (Triticum aestivum L.). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), isozymes, random amplified polymorphic DNA (RAPD), and comet assays were used. SDS-PAGE analysis revealed distinctive polymorphisms (100%) based on the number of polypeptide bands (169) with molecular weights ranging from 300.0 to 24.00 kDa, band intensity, appearance, and loss of bands when compared with control samples. Six isozymes, malate dehydrogenase, amylase, leucine-aminopeptidase, esterase, peroxidase, and catalase, generated 100% polymorphism values based on zymogram number, relative front, and optical intensities. RAPD revealed 276 DNA bands with a distinctive polymorphism value of 92.31% based on the number of amplified DNA products, ranging from 45 to 1100 bp, and band intensity. In the comet assay, the highest extent of nuclear DNA damage was observed as tail length 8.70 μm, tailed DNA 8.01%, and tail moment unit 34.18 in non-irrigated O3-treated wheat nuclei. These results show that O3-treatment alone induced high levels of oxidative protein and DNA damage in wheat plant, especially in a non-irrigation system. Interestingly, CO2 in combination with O3 could ameliorate the negative impact of O3-oxidative stress. This study shows that protein and DNA biomarkers, and the comet assay, could be used for the reliable estimation of genotoxicity following the exposure of economic crop plants to air pollutants.

Chemical and Natural Plant Extract in Ameliorating Negative Impact of Tropospheric Ozone on Wheat Crop: A Case Study in a Part of Semiarid North West India

ABSTRACTCurrent rise in concentration of tropospheric ozone (O3) has deleterious effect on growth and yield of crops. Wheat is one of the most O3 sensitive crops. Application of Chemical antioxidants may be beneficial to lessen the harmful effects of O3 on crops. A two year study growing wheat (variety PBW550) was carried at the farms of Indian Agricultural Research Institute, New Delhi in 2010–11 and 2011–12 to evaluate the efficacy of some natural and environment friendly antioxidant chemicals in ameliorating the negative impacts of elevated ozone on growth and productivity of wheat. The treatments were i) charcoal filtered air (CF) ii) 1% ascorbic acid (AA), iii) 100 ppm quercetin (Q), iv) 10% marigold leaves extract (Tagetes patula var pusa arpita) (T) and v) elevated O3 control (C). Additional 25–35 ppb of O3 over the ambient levels was maintained in all open top chambers except the CF treatment. The seasonal daily average O3 concentration in ambient air was 38 ppb in 2010–11 and 29 ppb in 2011–12 during the crop growth period. The exogenous application of antioxidants increased the levels of endogenous leaf ascorbic acid. The activity of antioxidant enzymes (superoxide dismutase, catalase and peroxidase) was lowered by 5 to 34% in antioxidants sprayed plants as compared to elevated O3 control (C). The application of antioxidants increased the yield of wheat by 23–26% in AA, 13–15% in Q and 8–10% in T as compared to C. The micronutrient (Cu, Fe, Zn and Mn) content of wheat grains on application of exogenous ascorbic acid was higher. The application of antioxidant chemicals was effective in alleviating the negative impacts of elevated O3 on enzyme activity and nutritional quality of wheat which increased the growth and yield of the crop

How do increasing background concentrations of tropospheric ozone affect peatland plant growth and carbon gas exchange?

Abstract In this study we have demonstrated that plants originating from upland peat bogs are sensitive to increasing background concentrations of ozone. Peatland mesocosms from an upland peat bog in North Wales, UK were exposed to eight levels of elevated background ozone in solardomes for 4 months from May to August, with 24 h mean ozone concentrations ranging from 16 to 94 ppb and cumulative AOT0 24hr ranging from 45.98 ppm h to 259.63 ppm h. Our results show that plant senescence increased with increasing exposure to ozone, although there was no significant effect of increasing ozone on plant biomass. Assessments of carbon dioxide and methane fluxes from the mesocosms suggests that there was no change in carbon dioxide fluxes over the 4 month exposure period but that methane fluxes increased as cumulative ozone exposure increased to a maximum AOT 0 24hr of approximately 120 ppm h and then decreased as cumulative ozone exposure increased further.

Barrier Wind Formation in the Upper Green River Basin of Sublette County, Wyoming, and Its Relationship to Elevated Ozone Distributions in Winter

AbstractMeteorological factors affect the concentrations and distributions of pollutants during episodes of degraded air quality. Over the last 10 years, the upper Green River basin (UGRB) of Sublette County, Wyoming, has experienced numerous wintertime ozone episodes stimulated by emissions from oil and natural gas development operations, resulting in the region being determined to be in marginal nonattainment of the National Ambient Air Quality Standards. Examination of surface wind field patterns in the UGRB using observations from a network of surface monitoring stations for 2011 and 2012, with an emphasis on ozone-episode days, confirms that increased ozone concentrations are most frequently measured on days on which winds are light and variable. Dispersion and dilution of ozone and its precursor pollutants on these days is therefore inefficient, and so these episodes invariably occur within and close by the gas fields. On days that instead experience afternoon southeasterly winds, episodes can often be observed at locations on the northwestern perimeter of the basin remote from pollutant source regions. Simulations using the Weather Research and Forecasting Model, conducted for the case study of 15 February 2011, identify these southeasterlies as barrier winds caused by southwesterly flow at 700 hPa impinging on the Wind River Mountains that flank the UGRB to the northeast. Characterization of the barrier wind and the overall airflow patterns facilitates more accurate future forecasting of the time-dependent geographical distribution of increased concentrations of ozone and other pollutants in the region.

Source apportionment of emissions from light-duty gasoline vehicles and other sources in the United States for ozone and particulate matter

ABSTRACTFederal Tier 3 motor vehicle emission and fuel sulfur standards have been promulgated in the United States to help attain air quality standards for ozone and PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm). The authors modeled a standard similar to Tier 3 (a hypothetical nationwide implementation of the California Low Emission Vehicle [LEV] III standards) and prior Tier 2 standards for on-road gasoline-fueled light-duty vehicles (gLDVs) to assess incremental air quality benefits in the United States (U.S.) and the relative contributions of gLDVs and other major source categories to ozone and PM2.5 in 2030. Strengthening Tier 2 to a Tier 3-like (LEV III) standard reduces the summertime monthly mean of daily maximum 8-hr average (MDA8) ozone in the eastern U.S. by up to 1.5 ppb (or 2%) and the maximum MDA8 ozone by up to 3.4 ppb (or 3%). Reducing gasoline sulfur content from 30 to 10 ppm is responsible for up to 0.3 ppb of the improvement in the monthly mean ozone and up to 0.8 ppb of the improvement in maximum ozone. Across four major urban areas—Atlanta, Detroit, Philadelphia, and St. Louis—gLDV contributions range from 5% to 9% and 3% to 6% of the summertime mean MDA8 ozone under Tier 2 and Tier 3, respectively, and from 7% to 11% and 3% to 7% of the maximum MDA8 ozone under Tier 2 and Tier 3, respectively. Monthly mean 24-hr PM2.5 decreases by up to 0.5 μg/m3 (or 3%) in the eastern U.S. from Tier 2 to Tier 3, with about 0.1 μg/m3 of the reduction due to the lower gasoline sulfur content. At the four urban areas under the Tier 3 program, gLDV emissions contribute 3.4–5.0% and 1.7–2.4% of the winter and summer mean 24-hr PM2.5, respectively, and 3.8–4.6% and 1.5–2.0% of the mean 24-hr PM2.5 on days with elevated PM2.5 in winter and summer, respectively.Implications: Following U.S. Tier 3 emissions and fuel sulfur standards for gasoline-fueled passenger cars and light trucks, these vehicles are expected to contribute less than 6% of the summertime mean daily maximum 8-hr ozone and less than 7% and 4% of the winter and summer mean 24-hr PM2.5 in the eastern U.S. in 2030. On days with elevated ozone or PM2.5 at four major urban areas, these vehicles contribute less than 7% of ozone and less than 5% of PM2.5, with sources outside North America and U.S. area source emissions constituting some of the main contributors to ozone and PM2.5, respectively.

Ozone reaction with interior building materials: Influence of diurnal ozone variation, temperature and humidity

Abstract Elevated tropospheric ozone concentrations are associated with increased morbidity and mortality. Indoor ozone chemistry affects human exposure to ozone and reaction products that also may adversely affect health and comfort. Reactive uptake of ozone has been characterized for many building materials; however, scant information is available on how diurnal variation of ambient ozone influences ozone reaction with indoor surfaces. The primary objective of this study is to investigate ozone-surface reactions in response to a diurnally varying ozone exposure for three common building materials: ceiling tile, painted drywall, and carpet tile. A secondary objective is to examine the effects of air temperature and humidity. A third goal is to explore how conditioning of materials in an occupied office building might influence subsequent ozone-surface reactions. Experiments were performed at bench-scale with inlet ozone concentrations varied to simulate daytime (ozone elevated) and nighttime (ozone-free in these experiments) periods. To simulate office conditions, experiments were conducted at two temperatures (22 °C and 28 °C) and three relative humidity values (25%, 50%, 75%). Effects of indoor surface exposures were examined by placing material samples in an occupied office and repeating bench-scale characterization after exposure periods of 1 and 2 months. Deposition velocities were observed to be highest during the initial hour of ozone exposure with slow decrease in the subsequent hours of simulated daytime conditions. Daily-average ozone reaction probabilities for fresh materials are in the respective ranges of (1.7–2.7) × 10−5, (2.8–4.7) × 10−5, and (3.0–4.5) × 10−5 for ceiling tile, painted drywall, and carpet tile. The reaction probability decreases by 7%–47% across the three test materials after two 8-h periods of ozone exposure. Measurements with the samples from an occupied office reveal that deposition velocity can decrease or increase with time. Influence of temperature and humidity on ozone-surface reactivity was not strong.

An analysis of ozone damage to historical maize and soybean yields in the United States

Numerous controlled experiments find that elevated ground-level ozone concentrations ([O3]) damage crops and reduce yield. There have been no estimates of the actual yield losses in the field in the United States from [O3], even though such estimates would be valuable for projections of future food production and for cost-benefit analyses of reducing ground-level [O3]. Regression analysis of historical yield, climate, and [O3] data for the United States were used to determine the loss of production due to O3 for maize (Zea mays) and soybean (Glycine max) from 1980 to 2011, showing that over that period production of rain-fed fields of soybean and maize were reduced by roughly 5% and 10%, respectively, costing approximately $9 billion annually. Maize, thought to be inherently resistant to O3, was at least as sensitive as soybean to O3 damage. Overcoming this yield loss with improved emission controls or more tolerant germplasm could substantially increase world food and feed supply at a time when a global yield jump is urgently needed.