Abstract  Floral scent is used by pollinators during foraging to identify and discriminate among flowers. The ability to discriminate among scents may depend on both scent intensity and the ratios of the concentrations of the volatile compounds of a complex mixture rather than on the presence of a few compounds. We used four scent-emitting cultivars of snapdragon (Antirrhinum majus) to test this hypothesis by examining the ability of honeybees to differentiate among their scents. Each cultivar produced three monoterpenes (myrcene, E-β-ocimene, and linalool) and five phenylpropanoids (methylbenzoate, acetophenone, dimethoxytoluene, cis-methylcinnamate, and trans-methylcinnamate). Cultivars were reliably classified by their scents in a canonical discriminant analysis. Honeybees were unable to discriminate among the scents of flowers of the same cultivar in our assay. The ability of honeybees to discriminate among the scents of different cultivars was a function of the intensity of the floral scent. Discrimination was also correlated to the distance among the scents described by the discriminant analysis; the cultivars that had the greatest differences observed in the discriminant analysis were the easiest to discriminate. Our results show that honeybees are capable of using all of the floral volatiles to discriminate subtle differences in scent.

Abstract  Oxidant air pollution symptoms were first reported in bioindicator plants in the Mexico City Air Basin (MCAB) in 1971 (de Bauer 1972). Classic injury symptoms on well-known bioindicator plants strongly supported the presumption that symptoms were caused by photochemical oxidants, of which ozone (O3) is the primary pollutant. Symptoms in indicator plants characteristic of injury caused by peroxyacetyl nitrate (PAN), ethylene, and sulfur dioxide (SO2) were also reported (de Bauer 1972; de Bauer and Hernández-Tejeda 1986). These discoveries were followed in 1976 by the observation of O3 injury symptoms in native pine species in forests in Ajusco (AJ), just south of Mexico City (de Bauer and Hernández-Tejeda 1986; Krupa and de Bauer 1976). Then in the 1980s, a dramatic and severe decline occurred in sacred fir (Abies religiosa) stands in the highly polluted area of the Desierto de los Leones (DL) National Park southwest of Mexico City (Alvarado-Rosales and Hernández-Tejeda 2002). Thousands of trees died, leaving dead zones called cemeteries. Air pollution was widely believed to be an important causal factor in the widespread mortality of sacred fir within the park (Ciesla and Macias-Samano 1987). Topographic conditions, including volcanic mountain ranges circumscribing much of the Basin, thermal atmospheric inversions, and prevailing winds which carry pollutants from the urban zone to forested areas to the south-southwest (SSW), create conditions favoring high pollution exposure for these forests (Bravo and Torres 2002; Jáuregui 2002).

Abstract  The aim was to study the influence of abiotic (elevated ozone) or biotic stress (Phytophthora citricola) or their combination on soil biological components and processes in the rhizosphere of young beech trees. Ectomycorrhizal and overall microbial community composition was studied at two soil depths in a lysimeter experiment with 7 year old trees of Fagus sylvatica. As a functional parameter, potential enzyme activities were measured in mycorrhizosphere soil and on excised mycorrhizal tips. The degree of mycorrhization, structure and potential enzymatic activities of mycorrhizal communities were only slightly influenced by treatments. Soil enzyme activities were depressed under elevated ozone and stimulated by P. citricola under ambient but not under elevated ozone. Overall microbial community composition (PLFA) and ectomycorrhizal diversity changed with depth. PLFA analyses not only suggested a reaction of the microbial community to elevated ozone but also indicated an increase in plant stress related components. No influence of the biotic stress on ectomycorrhizal or overall microbial community structure was detected. Changes in the mycorrhizosphere community structure and function due to ozone may be explained by the quality of plant derived carbon.

Abstract  Climate change and extreme weather events affect plants and animals and the direct impact of anthropogenic climate change has been documented extensively over the past years. In this review, I address the main consequences of elevated CO2 and O3 concentrations, elevated temperature and changes in rainfall patterns on the interactions between insects and their host plants. Because of their tight relationship with host plants, insect herbivores are expected to suffer direct and indirect effects of climate change through the changes experienced by their host plants, with consequences to population dynamics, community structure and ecosystem functioning.

Abstract  Discussions and applications of the policies and practices of the U.S. Environmental Protection Agency (USEPA) in ecological risk assessment will benefit from continued clarification of the concepts of assessment endpoints and of levels of biological organization. First, assessment endpoint entities and attributes can be defined at different levels of organization. Hence, an organism-level attribute, such as growth or survival, can be applied collectively to a population-level entity such as the brook trout in a stream. Second, assessment endpoints for ecological risk assessment are often mistakenly described as “individual level,” which leads to the idea that such assessments are intended to protect individuals. Finally, populations play a more important role in risk assessments than is generally recognized. Organism-level attributes are used primarily for population-level assessments. In addition, the USEPA and other agencies already are basing management decisions on population or community entities and attributes such as production of fisheries, abundance of migratory bird populations, and aquatic community composition.

Abstract  Biomonitoring by means of the supersensitive cultivar Nicotiana tabacum Bel-W3 is frequently used to obtain information on ozone effects on plants and estimates of ozone exposure. However, most of biomonitoring surveys do not account for other environmental variables (predictors in a statistical model) and their inherent multicollinearity with ozone. We tested the relative role of different predictors (fixed: time and site; random: ozone, temperature and humidity) on height growth and on the development of visible foliar symptoms of N. tabacurn Bel-W3 plants. To do this, we investigated a relatively small area (256 km(2)), used a random design at every stage of the survey, controlled watering and protected plants from direct solar radiation and wind. QA/QC procedures were adopted at every stage of the investigation. Linear correlation shows that Leaf Injury Index (LII) and height increment (HI.) positively related to ozone concentration, elevation and temperature, and negatively to relative humidity. All the predictors correlate to each other. However, relationships between response and ozone vary with the site and the monitoring week. The effect of the random factor ""ozone"" in combination with fixed factors ""site"" and ""time"" on the response variables was therefore formally investigated using the ANCOVA model. Besides ozone, the interactions ""ozone x site"" and ""ozone x time"" resulted always significant (0.001 < P < 0.05). While the factor ""time"" emphasize the inherent development of injury and growth through time, the interaction ""ozone x site"" pointed out the importance of local conditions. When watering, solar radiation, wind and plant characteristics were controlled, the remaining site-specific covariates of interest were temperature (T) and humidity (RH). When T and RH were accounted for by means of partial correlation analysis, no significant relationship was found between ozone and LII. On the other side, 03 and RH resulted significant for both absolute and relative height increment. In short, LII seemed to be not solely dependent on ozone, T and RH, but showed to integrate their combined effect. On the other side, H.I. seemed to be favoured by high RH and T, and depressed by high ozone. Based on the above results, we recommend caution when handling bioindicator data: if the purpose is to infer ozone concentrations by leaf injury data, results may be affected by a serious bias, as the frequently reported correlations may be partly an artefact due to co- variation between predictors. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  High surface ozone concentrations are recognized as an emerging threat to food security in Asia. This study aimed at determining the effects of ozone on the nutritive quality of rice straw, a by-product of rice grain production and a major feed resource for ruminant livestock. Further, the question was addressed whether negative effects of ozone can be mitigated through molecular breeding. Rice plants from three different genotypes were exposed to four different ozone treatments in fumigation chambers from transplanting to maturity. These genotypes were (i) IR64, one of the most wide spread indica varieties in the world, (ii) Nipponbare, a typical japonica variety, and (iii) SL41, an ozone tolerant breeding line that carried chromosomal inserts at the ozone tolerance QTL OzT9 in the genetic background of Nipponbare. The treatments consisted of (i) charcoal filtered air, (ii) simulated ambient ozone concentration, (iii) 2 × ambient ozone concentration, and (iv) 2.5 × ambient ozone concentration. The effects of ozone on the chemical composition of straw were clearly dependent of the ozone level, and were significant even at ambient ozone concentration. Increases in crude ash, lignin and phenolics concentration adversely affected the digestibility as demonstrated in incubation experiments simulating rumen digestion in vitro. Negative ozone effects included reductions in the rate and extent of gas production due to inhibition of microbial fermentation, reduced formation of short chain fatty acids (SCFA), and a decrease in the true organic matter digestibility. The ozone tolerant genotype SL41 was less responsive to ozone than its more susceptible recurrent parent Nipponbare in terms of lignin and phenolics formation, organic matter digestibility and SCFA production. These data demonstrate that the feed quality of rice straw is affected by ozone even at ambient concentration, and that these negative effects are mitigated by the ozone tolerance QTL OzT9.

Abstract  A comparison of the maps of stomatal ozone uptake (AFst0) and concentrations exceeding 40 ppb (AOT40) for dominant temperate deciduous tree species (Quercus serrata, Fagus crenata, Betula ermanii) was conducted in Japan. Estimations of stomatal ozone uptake were accomplished using estimated ozone concentration, climate data, and vegetation data. Key parameters such as stomatal conductance parameters for each species were collected from scientific literature in Japan. Stomatal closure induced by vapour pressure deficit affected the AFst0 values in warmer part of Japan. For this reason, the areas with high AOT40 did not always correspond to the areas with high AFst0. The result showed that ozone risk assessment using AOT40 is VPD-constrained in central Japan, which implies an overestimation of risk compared to AFst0. While in Europe AOT40 is higher where water stress is recurrent, AOT40 peaked in the cool and humid climate region of central-eastern Japan where also stomatal ozone uptake reached maximum values.

Abstract  During two measurement campaigns, from August to September 2008 and 2009, we quantified the major ecosystem fluxes in a hemiboreal forest ecosystem in Jaryselja, Estonia. The main aim of this study was to separate the ecosystem flux components and gain insight into the performance of a multi-species multilayered tree stand. Carbon dioxide and water vapor fluxes were measured using the eddy covariance method above and below the canopy in conjunction with the microclimate. Leaf and soil contributions were quantified separately by cuvette and chamber measurements, including fluxes of carbon dioxide, water vapor, nitrogen oxides, nitrous oxide, methane, ozone, sulfur dioxide, and biogenic volatile organic compounds (isoprene and monoterpenes). The latter have been as well characterized for monoterpenes in detail. Based on measured atmospheric trace gas concentrations, the flux tower site can be characterized as remote and rural with low anthropogenic disturbances. Our results presented here encourage future experimental efforts to be directed towards year round integrated biosphere-atmosphere measurements and development of process-oriented models of forest-atmosphere exchange taking the special case of a multi-layered and multi-species tree stand into account. As climate change likely leads to spatial extension of hemiboreal forest ecosystems a deep understanding of the processes and interactions therein is needed to foster management and mitigation strategies. (C) 2010 Elsevier BM. All rights reserved.

Abstract  Ozone (O3) is the air pollutant of major concern for vegetation. Levels in Mediterranean cities may exceed the criteria for vegetation protection. Ozone may induce a number of plant responses, e.g., visible injury on the leaves, that affect the ornamental value of urban forests. Antioxidant application may protect sensitive plants from ozone. The most successful synthetic antioxidant is ethylenediurea (EDU). Here we set the optimal EDU dose and concentration (260 mg m-2 leaf, 450 ppm) for protecting adult Fraxinus excelsior trees from ozone visible injury by means of EDU applications as soil drench.

Abstract  This study considered effects of reduced [O(3)] on wheat yield. Open-top chamber charcoal filtered air treatments were compared with non-filtered treatments for field-grown wheat. 30 experiments meeting requirements were found, representing nine countries in North America, Europe and Asia. 26 experiments reported improved yield and 4 experiments reduced yield by filtration, a significant positive effect. Average yield improvement was 9%. Average daytime [O(3)] was reduced by filtration from 35 to 13 nmol mol(-1). Filtration efficiency was 63% for O(3) and 56% for SO(2). For NO(x) it was observed that NO(2) was reduced and NO increased by filtration. Thus, filters convert NO(2) to NO. Most experiments reported low or very low [SO(2)] and [NO(x)]. Thus, O(3) can be concluded to be the main phytotoxic component in the experiments. Elevated [NO(2)] was observed in one experiment. The conclusion is that current [O(3)] over large parts of the world adversely affect wheat yield.

Abstract  Against a backdrop of increasing climate change, the effects of site conditions, drought events and ozone stress on the size-growth relationship in Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica [L.]) stands are analyzed. The size-growth relationship is represented by a straight line defined by intercept and slope of a simple linear equation with stem diameter at height 1.30 m as independent variable and annual stem diameter increment at height 1.30 as dependent variable. On the basis of 64 long-term experimental plots dating back to 1871 and representing an ecological gradient from fertile to poor sites, it is shown that poorer sites exhibit shallower slopes of the linear size-growth relationships than fertile sites. Annual measurements of the size-growth relationship, including the extremely dry years of 1976 and 2003, also showed that lower stand growth rates result in shallower size-growth relationship slopes. By comparing stands with and without experimental twice-ambient ozone exposure between 2000 and 2007, it was found that ozone stress can significantly reduce the slope of the size-growth relationship. This indicates that limiting site condition, whether acute or chronic in nature, distinctly reduces the superiority of tall trees, and that a lower degree of resource limitation increases the steepness of the size-growth relationship. The causes for this behavior and the consequences for stand dynamics, silvicultural treatment and prognostication by models are discussed.

Abstract  Ascorbic acid (AsA, vitamin C) is one of the most important nutritional quality factors in many horticultural crops and has many biological activities in the human body. Dehydroascorbate reductase (EC 1.8.5.1; DHAR) plays an important role in maintaining the normal level of ascorbic acid (AsA) by recycling oxidized ascorbic acid. To increase AsA content of potato, we isolated and characterized the cDNAs encoding two isoform DHARs localized in cytosol and chloroplast from potato, and developed two types of transgenic potato plants overexpressing cytosolic DHAR gene and chloroplastic DHAR, respectively. Incorporation of the transgene in the genome of potato was confirmed by PCR and real time RT-PCR. The overexpression of cytosolic DHAR significantly increased DHAR activities and AsA contents in potato leaves and tubers, whereas chloroplastic DHAR overexpression only increased DHAR activities and AsA contents in leaves, and did not change them in tubers. These results indicated that AsA content of potato can be elevated by enhancing recycling ascorbate via DHAR overexpression, moreover, cytosolic DHAR might play main important roles in improving the AsA contents of potato tubers.

Abstract  Surface ozone (O(3)) is a potent phytotoxic air pollutant that reduces the productivity of agricultural crops. Growing use of fossil fuel and climate change are increasing O(3) concentrations to levels that threaten food supply. Historically, farmers have successfully adapted agricultural practices to cope with changing environments. However, high O(3) concentrations are a new threat to food production and possibilities for adaptation are not well understood. We simulate the impact of ozone damage on four key crops (wheat, maize, rice and soybean) on a global scale and assess the effectiveness of adaptation of agricultural practices to minimize ozone damage. As O(3) concentrations have a strong seasonal and regional pattern, the adaptation options assessed refer to shifting crop calendars through changing sowing dates, applying irrigation and using crop varieties with different growth cycles. Results show that China, India and the United States are currently by far the most affected countries, bearing more than half of all global losses and threatened areas. Irrigation largely affects ozone exposure but local impacts depend on the seasonality of emissions and climate. Shifting crop calendars can reduce regional O(3) damage for specific crop-location combinations (e.g. up to 25% for rain-fed soybean in India) but has little implication at the global level. Considering the limited benefits of adaptation, mitigation of O(3) precursors remains the main option to secure regional and global food production. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  We present the Chemistry of Atmosphere-Forest Exchange (CAFE) model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. CAFE integrates all key processes, including turbulent diffusion, emission, deposition and chemistry, throughout the forest canopy and mixed layer. CAFE utilizes the Master Chemical Mechanism (MCM) and is the first model of its kind to incorporate a suite of reactions for the oxidation of monoterpenes and sesquiterpenes, providing a more comprehensive description of the oxidative chemistry occurring within and above the forest. We use CAFE to simulate a young Ponderosa pine forest in the Sierra Nevada, CA. Utilizing meteorological constraints from the BEARPEX-2007 field campaign, we assess the sensitivity of modeled fluxes to parameterizations of diffusion, laminar sublayer resistance and radiation extinction. To characterize the general chemical environment of this forest, we also present modeled mixing ratio profiles of biogenic hydrocarbons, hydrogen oxides and reactive nitrogen. The vertical profiles of these species demonstrate a range of structures and gradients that reflect the interplay of physical and chemical processes within the forest canopy, which can influence net exchange.

Abstract  Hourly measurements of O(3), NO, NO(2), PAN, HNO(3) and NO(y) concentrations, and eddy-covariance fluxes of O(3) and NO(y) over a temperate deciduous forest from June to November, 2000 were used to evaluate the dry deposition velocities (V(d)) estimated by the WRF-Chem dry deposition module (WDDM), which adopted Wesely (1989) scheme for surface resistance (R(c)), and the Noah land surface model coupled with a photosynthesis-based Gas-exchange Evapotranspiration Model (Noah-GEM). Noah-GEM produced better V(d)(O(3)) variations due to its more realistically simulated stomata! resistance (R(s)) than WDDM. V(d)(O(3)) is very sensitive to the minimum canopy stomatal resistance (R(i)) which is specified for each seasonal category assigned in WDDM. Treating Sep-Oct as autumn in WDDM for this deciduous forest site caused a large underprediction of Vd(O(3)) due to the leafless assumption in 'autumn' seasonal category for which an infinite R(i) was assigned. Reducing R(i) to a value of 70 s m(-1), the same as the default value for the summer season category, the modeled and measured V(d)(O(3)) agreed reasonably well. HNO(3) was found to dominate the NO(y) flux during the measurement period: thus the modeled V(d)(NO(y)) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances (R(a) and R(b)), both being sensitive to the surface roughness length (z(0)). Using an aropriate value for z(0) (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime V(d)(NO(y)). The differences in V(d)(HNO(3)) between WDDM and Noah-GEM were small due to the small differences in the calculated R(a) and R(b) between the two models: however, the differences in R(c) of NO(2) and PAN between the two models reached a factor of 1.1-1.5, which in turn caused a factor of 1.1-1.3 differences for V(d). Combining the measured concentrations and modeled V(d), NO(x), PAN and HNO(3) accounted for 19%, 4%, and 70% of the measured NO(y) fluxes, respectively. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s(-1) and 0.36 cm s(-1) by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s(-1). In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O3 concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation.

Abstract  Background Ambient fine particles (particular matter <2.5 μm diameter [PM2.5]) and ozone exacerbate respiratory conditions including asthma. There is little documentation determining whether children are more vulnerable to the effects of ambient pollution than adults, or whether pollution causes life-threatening episodes requiring intensive care unit (ICU) admission. Objective We investigate the relationship between severe asthma morbidity and PM2.5 and ozone in the warm season, and determine whether there is an age-related susceptibility to pollution. Methods Daily time-series analysis of 6008 asthma ICU admissions and 69,375 general (non-ICU) asthma admissions in 4 age groups (<6, 6-18, 19-49, and 50+ years) in 74 New York City hospitals for the months April to August from 1999 to 2006. The regression model adjusted for temporal trends, weather, and day of the week. Risks were estimated for interquartile range increases in the a priori exposure time window of the average of 0-day and 1-day lagged pollutants. Results Age was a significant effect modifier for hospitalizations, and children age 6 to 18 years consistently had the highest risk. Among children age 6 to 18 years, there was a 26% (95% CI, 10% to 44%) increased rate of ICU admissions and a 19% increased rate of general hospitalizations (95% CI, 12% to 27%) for each 12-μg/m3 increase in PM2.5. For each 22-ppb increase in ozone, there was a 19% (95% CI, 1% to 40%) increased risk for ICU admissions and a 20% (95% CI, 11% to 29%) increased risk for general hospitalizations. Conclusion Warm weather patterns of ozone and PM2.5 disproportionately affect children with asthma and appear responsible for severe attacks that could have been avoided.

Abstract  The study evaluated the effect of ozone application on the composite-to-composite bond. Three hundred and twenty cylindrical composite specimens were divided into two groups: group 1 was subjected to a 60 s ozone application, whereas group 2 remained untreated. Four subgroups were obtained from each group according to the intermediate repair agent: an adhesive, a silane, silane/adhesive combination, or flowable composite. Repair composite cylinders were built-up. The composite repair strength was tested after 24 h and after thermocycling with a shear test. Additionally, 4 mm x 4 mm x 2 mm composite specimens were prepared and stored 24 h in deionized water. Half of the specimens were subjected to ozone application and the other served as control. The elastic modulus (E) and the Vicker's hardness (VH) of the composite surfaces were tested immediately and after thermocycling. Significant differences among the experimental groups were detected (p < 0.001). The composite repair strength was affected by the pretreatment and by the intermediate agent, whereas, the thermocycling was not significant. The partial eta-squared statistics showed that the intermediate agent was the main factor affecting the composite repair strength, whereas the pretreatment played a minor role. No differences were observed between ozone and control groups when the same intermediate agent and the same aging conditions were applied. Repairing with flowable composite tended to achieve higher bond strengths (20.7 and 26.5 MPa in ozone and control groups, respectively, after 24 h). The use of silane coupling agent showed the lowest composite repair strengths. Ozone did not affect E and VH (p > 0.05) and the thermocycling affected only E (p < 0.05). In conclusion, the application of ozone does not impair the composite-to-composite bond.

Abstract  Multipollutant models are frequently used to differentiate roles of multiple pollutants in epidemiologic studies of ambient air pollution. In the presence of differing levels of measurement error across pollutants under consideration, however, they can be biased and as misleading as single-pollutant models. Their appropriate interpretation depends on the relationships among the pollutant measurements and the outcomes in question. In situations where two or more pollutant variables may be acting as surrogates for the etiologic agent(s), multipollutant models can help identify the best surrogate, but the risk estimates may be influenced by inclusion of a second variable that is not itself an independent risk factor for the outcome in question. In this paper, these issues will be illustrated in the context of an ongoing study of emergency visits in Atlanta. Emergency department visits from 41 of 42 hospitals serving the twenty-county Atlanta metropolitan area for the period 1993-2004 (n=10,206,389 visits) were studied in relation to ambient pollutant levels, including speciated particle measurements from an intensive monitoring campaign at a downtown station starting in 1998. Relative to our earlier publications, reporting results through 2000, the period for which the speciated data are now available is now tripled (six years in length). Poisson generalized linear models were used to examine outcome counts in relation to three-day moving average concentrations of pollutants of a priori interest (ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, oxygenated hydrocarbons, PM10, coarse PM, PM2.5, and the following components of PM2.5: elemental carbon, organic carbon, sulfate, water-soluble transition metals.) In the present analysis, we report results for two outcome groups: a respiratory outcomes group and a cardiovascular outcomes group. For cardiovascular visits, associations were observed with CO, 3 NO2, and PM2.5 elemental carbon and organic carbon. In multipollutant models, CO was the strongest predictor. For respiratory visits, associations were observed with ozone, PM10, CO and NO2 in single-pollutant models. In multipollutant models, PM10 and ozone persisted as predictors, with ozone the stronger predictor. Caveats and considerations in interpreting the multipollutant model results are discussed.

Abstract  A lack of data on responses of mature tree growth and water use to ambient ozone (O3 ) concentrations has been a major limitation in efforts to understand and model responses of forests to current and future changes in climate. ò Here, hourly to seasonal patterns of stem growth and sap flow velocity were examined in mature trees from a mixed deciduous forest in eastern Tennessee (USA) to evaluate the effects of variations in ambient O3 exposure and climate on patterns of stem growth and water use. ò Ambient O3 caused a periodic slowdown in seasonal growth patterns that was attributable in part to amplification of diurnal patterns of water loss in tree stems. This response was mediated by statistically significant increases in O3 -induced daily sap flow and led to seasonal losses in stem growth of 30-50% for most species in a high-O3 year. ò Decreased growth and increased water use of mature forest trees under episodically high ambient O3 concentrations suggest that O3 will amplify the adverse effects of increasing temperatures on forest growth and forest hydrology.

Abstract  This article describes the governing equations, computational algorithms, and other components entering into the Community Multiscale Air Quality (CMAQ) modeling system. This system has been designed to approach air quality as a whole by including state-of-the-science capabilities for modeling multiple air quality issues, including tropospheric ozone, fine particles, acid deposition, and visibility degradation. CMAQ was also designed to have multiscale capabilities so that separate models were not needed for urban and regional scale air quality modeling. By making CMAQ a modeling system that addresses multiple pollutants and different spatial scales, it has a "one-atmosphere" perspective that combines the efforts of the scientific community. To implement multiscale capabilities in CMAQ, several issues (such as scalable atmospheric dynamics and generalized coordinates), which depend on the desired model resolution, are addressed. A set of governing equations for compressible nonhydrostatic atmospheres is available to better resolve atmospheric dynamics at smaller scales. Because CMAQ is designed to handle scale-dependent meteorological formulations and a large amount of flexibility, its governing equations are expressed in a generalized coordinate system. This approach ensures consistency between CMAQ and the meteorological modeling system. The generalized coordinate system determines the necessary grid and coordinate transformations, and it can accommodate various vertical coordinates and map projections. The CMAQ modeling system simulates various chemical and physical processes that are thought to be important for understanding atmospheric trace gas transformations and distributions. The modeling system contains three types of modeling components (Models-3): a meteorological modeling system for the description of atmospheric states and motions, emission models for man-made and natural emissions that are injected into the atmosphere, and a chemistry-transport modeling system for simulation of the chemical transformation and fate. The chemical transport model includes the following process modules: horizontal advection, vertical advection, mass conservation adjustments for advection processes, horizontal diffusion, vertical diffusion, gas-phase chemical reactions and solvers, photolytic rate computation, aqueous-phase reactions and cloud mixing, aerosol dynamics, size distributions and chemistry, plume chemistry effects, and gas and aerosol deposition velocity estimation. This paper describes the Models-3 CMAQ system, its governing equations, important science algorithms, and a few application examples.

Abstract  The National Children's Study is considering a wide spectrum of airborne pollutants that are hypothesized to potentially influence pregnancy outcomes, neurodevelopment, asthma, atopy, immune development, obesity, and pubertal development. In this article we summarize six applicable exposure assessment lessons learned from the Centers for Children's Environmental Health and Disease Prevention Research that may enhance the National Children's Study: a) Selecting individual study subjects with a wide range of pollution exposure profiles maximizes spatial-scale exposure contrasts for key pollutants of study interest. b) In studies with large sample sizes, long duration, and diverse outcomes and exposures, exposure assessment efforts should rely on modeling to provide estimates for the entire cohort, supported by subject-derived questionnaire data. c) Assessment of some exposures of interest requires individual measurements of exposures using snapshots of personal and microenvironmental exposures over short periods and/or in selected microenvironments. d) Understanding issues of spatial-temporal correlations of air pollutants, the surrogacy of specific pollutants for components of the complex mixture, and the exposure misclassification inherent in exposure estimates is critical in analysis and interpretation. e) "Usual" temporal, spatial, and physical patterns of activity can be used as modifiers of the exposure/outcome relationships. f) Biomarkers of exposure are useful for evaluation of specific exposures that have multiple routes of exposure. If these lessons are applied, the National Children's Study offers a unique opportunity to assess the adverse effects of air pollution on interrelated health outcomes during the critical early life period.