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  Human exposure time-series modeling requires longitudinal time-activity diaries to evaluate the sequence of concentrations encountered, and hence, pollutant exposure for the simulated individuals. However, most of the available data on human activities are from cross-sectional surveys that typically sample 1 day per person. A procedure is needed for combining cross-sectional activity data into multiple-day (longitudinal) sequences that can capture day-to-day variability in human exposures. Properly accounting for intra- and interindividual variability in these sequences can have a significant effect on exposure estimates and on the resulting health risk assessments. This paper describes a new method of developing such longitudinal sequences, based on ranking 1-day activity diaries with respect to a user-chosen key variable. Two statistics, "D" and "A", are targeted. The D statistic reflects the relative importance of within- and between-person variance with respect to the key variable. The A statistic quantifies the day-to-day (lag-one) autocorrelation. The user selects appropriate target values for both D and A. The new method then stochastically assembles longitudinal diaries that collectively meet these targets. On the basis of numerous simulations, the D and A targets are closely attained for exposure analysis periods >30 days in duration, and reasonably well for shorter simulation periods. Longitudinal diary data from a field study suggest that D and A are stable over time, and perhaps over cohorts as well. The new method can be used with any cohort definitions and diary pool assignments, making it easily adaptable to most exposure models. Implementation of the new method in its basic form is described, and various extensions beyond the basic form are discussed.

Abstract  The dynamic core of the Ocean–Land–Atmosphere Model (OLAM), which is a new global model that is partly based on the Regional Atmospheric Modeling System (RAMS), is described and tested. OLAM adopts many features of its predecessor, but its dynamic core is new and incorporates a global geodesic grid with triangular mesh cells and a finite-volume discretization of the nonhydrostatic compressible Navier–Stokes equations. The spatial discretization of horizontal momentum is based on a C-staggered grid and uses a method that has not been previously applied in atmospheric modeling. The temporal discretization uses a unique form of time splitting that enforces consistency of advecting mass flux among all conservation equations. OLAM grid levels are horizontal, and topography is represented by the shaved-cell method. Aspects of the shaved-cell method that pertain to the OLAM discretization on the triangular mesh are described, and a method of conserving momentum in shaved cells on a C-staggered grid is presented. The dynamic core was tested in simulations with multiple vertical model levels and significant vertical motion. The tests include an idealized global circulation simulation, a cold density current, and mountain-wave flow over an orographic barrier, all of which are well-known standard benchmark experiments. OLAM gave acceptable results in all tests, demonstrating that its dynamic core produces accurate and robust solutions.

Abstract  Many regulations issued by the U.S. Environmental Protection Agency (EPA) are based on the results of computer models. Models help EPA explain environmental phenomena in settings where direct observations are limited or unavailable, and anticipate the effects of agency policies on the environment, human health and the economy. Given the critical role played by models, the EPA asked the National Research Council to assess scientific issues related to the agency's selection and use of models in its decisions. The book recommends a series of guidelines and principles for improving agency models and decision-making processes. The centerpiece of the book's recommended vision is a life-cycle approach to model evaluation which includes peer review, corroboration of results, and other activities. This will enhance the agency's ability to respond to requirements from a 2001 law on information quality and improve policy development and implementation.

Abstract  Using a one-dimensional radiative-convective model, we perform a sensitivity study of the effect of ozone depletion in the stratosphere on the surface temperature. There could be a cooling of the surface temperature by 0.2 K due to chlorofluoromethane-induced ozone depletion at steady state (assuming 1973 release rates). This cooling reduces significantly the greenhouse effect due to the presence of chlorofluoromethanes. Carbon tetrafluoride has a strong 3 band at 7.8 m, and the atmospheric greenhouse effect is shown to be 0.07 and 0.12 K (ppbv)1 with and without taking into account overlap with CH4 and N2O bands. At concentration higher than l ppbv, absorption by the 3 band starts to saturate and the greenhouse effect becomes less efficient.

Abstract  Rotavirus is the leading cause of severe acute gastroenteritis among infants and young children, accounting for an estimated 527,000 deaths among children aged <5 years worldwide in 2004 (1,2). In the United States, rotavirus causes few deaths (20-60) each year, but remains a substantial cause of morbidity among children, resulting in approximately 55,000--70,000 hospitalizations, 205,000-272,000 emergency department (ED) visits, and 410,000 physician office visits. In the continental United States, rotavirus activity follows a distinct winter-spring seasonal pattern. In winter months, approximately 50% of hospitalizations and ED visits and 30% of outpatient visits for acute gastroenteritis among U.S. children aged <3 years are caused by rotavirus. To prevent rotavirus disease, in February 2006, a human-bovine rotavirus vaccine, RotaTeq (Merck & Co., Inc., Whitehouse Station, New Jersey), was recommended for routine use among U.S. infants . To summarize rotavirus activity through May 3, during the current 2007-08 season, CDC analyzed data from the National Respiratory and Enteric Virus Surveillance System (NREVSS) and the New Vaccine Surveillance Network (NVSN). The results indicated that, when compared with the 15 previous seasons spanning 1991-2006, rotavirus activity during the current season appeared delayed in onset by 2-4 months and diminished in magnitude by >50%. Additional surveillance and epidemiologic studies are needed to confirm the impact of rotavirus vaccination on the 2007-08 season and to monitor the impact of the vaccine on the incidence and epidemiology of rotavirus during future seasons.

Abstract  Principal components analysis (PCA) and correlation analysis were used to estimate the contributionf four components related to pollutant sourcesn the total variationn concentrationsf Cu, Zn, Pb, Cd, As, Se, Hg, Fe and Mnn surface soil samples from a valleyn east China with numerous copper and zinc smelters. Resultsndicate that when carryingut sourcedentificationfnorganic pollutants their tendency to migraten soils may resultnifferences between the pollutant compositionf the source and the receptor soil, potentially leading to errorsn the characterizationf pollutants using multivariate statistics. The stability and potential migrationr movementf pollutantsn soils must therefore be takennto account. Soil physicochemical properties mayffer additional usefulnformation. Twoifferent mechanisms have been hypothesized for correlations between soil heavy metal concentrations and soilrganic matter content and these may be helpfulnnterpreting the statistical analysis.

Abstract  Ambient observations have indicated that high concentrations of ozone observed in the Houston/Galveston area are associated with plumes of highly reactive hydrocarbons, mixed with NOx, from industrial facilities. Ambient observations and industrial process data, such as mass flow rates for industrial flares, indicate that the VOCs associated with these industrial emissions can have significant temporal variability. To characterize the effect of this variability in emissions on ozone formation in Houston, data were collected on the temporal variability of industrial emissions or emission surrogates (e.g., mass flow rates to flares). The observed emissions variability was then used to construct regionwide emission inventories with variable industrial emissions, and the impacts of the variability on ozone formation were examined for two types of meteorological conditions, both of which lead to high ozone concentrations in Houston. The air quality simulations indicate that variability in industrial emissions has the potential to cause increases and decreases of 10–52 ppb (13–316%), or more, in ozone concentration. The largest of these differences are restricted to regions of 10–20 km2, but the variability also has the potential to increase regionwide maxima in ozone concentrations by up to 12 ppb.

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  Global mean tropospheric ozone concentration is expected to increase by more than 20% by 2050. Although the present levels of ozone may not induce visible symptoms in most of the plants, they can result in substantial production losses and reproductive output. There are wide variations in ozone sensitivity among varieties in same species. This paper reports variations in ozone sensitivity for two tropical soybean (Glycine max L.) varieties (PK 472 and Bragg) exposed to projected elevated ozone concentrations of 70 and 100ppb for 4h daily from germination to maturity under natural field conditions. Differential sensitivities of cultivars to ozone were assessed by comparing the levels of antioxidative potential, metabolite production, growth behaviour, biomass accumulation and yield responses. The activity of catalase decreased whereas peroxidase increased in both the varieties upon exposure to O sub(3), however, the magnitude of change was always higher in PK 472 as compared to Bragg. The larger magnitude of reductions in the levels of antioxidants, metabolites and nutrients also reflected the greater sensitivity of PK 472 compared to Bragg. The differential response of biochemical characteristics corresponded to significant reductions in plant length, number and area of leaves, component-wise biomass and yield parameters of PK 472 as compared to Bragg. This work emphasizes the greater sensitivity of a newly developed variety PK 472 of soybean compared to that of the older variety, Bragg. Further, the effects of ozone on different plant characteristics were found to be more prominent during reproductive than vegetative growth in these two varieties. In view of the anticipated increasing tropospheric O sub(3) concentrations the in near future, the results of the present study can be utilized in screening out more resistant varieties of soybean for greater agricultural productivity.

Abstract  Halogen atoms and oxides are highly reactive and can profoundly affect atmospheric composition. Chlorine atoms can decrease the lifetimes of gaseous elemental mercury(1) and hydrocarbons such as the greenhouse gas methane(2). Chlorine atoms also influence cycles that catalytically destroy or produce tropospheric ozone(3), a greenhouse gas potentially toxic to plant and animal life. Conversion of inorganic chloride into gaseous chlorine atom precursors within the troposphere is generally considered a coastal or marine air phenomenon(4). Here we report mid-continental observations of the chlorine atom precursor nitryl chloride at a distance of 1,400km from the nearest coastline. We observe persistent and significant nitryl chloride production relative to the consumption of its nitrogen oxide precursors. Comparison of these findings to model predictions based on aerosol and precipitation composition data from long-term monitoring networks suggests nitryl chloride production in the contiguous USA alone is at a level similar to previous global estimates for coastal and marine regions(5). We also suggest that a significant fraction of tropospheric chlorine atoms(6) may arise directly from anthropogenic pollutants.

Abstract  An investigation of global ultraviolet (G(UV)), global (G) and diffuse (G(d)) solar intensities, continuously recorded over a period of five years at a station in Athens, Greece, and stored on the basis of hourly time intervals since 1996, has revealed the following: (a) UV-global irradiation, associated with the 290-395 nm wavelength region, constitutes 4.1 % of global solar. (b) UV-global irradiance ranges from an average minimum of 2.4 W m(-2) and 3. 1 % of global solar in January to an average maximum of 45 W m(-2) and 7.8%, respectively, in June, both considered at 13:00, solar time. (c) There exists a good correlation among the two dimensionless irradiance ratios G(UV)/G(d) and G(d)/G in the form of an exponential relationship. (d) UV-global monthly irradiation data show evidence of temporal variability in Athens, from 1996 to 2000. (e) Anthropogenic and photochemical atmospheric pollutant agents (O-3, CO, SO2, NOx smoke) causing air pollution episodes seem to affect differently solar irradiance components. The main results of analysis (measurements within +/-2 h from solar noon) indicate that a buildup Of O-3 and NOx inside the urban Athens plume during cloudless and windless warm days could cause: (i) UV-global irradiance depletion between 5.4% and 14.4%. (ii) Diffuse solar irradiance enhancement up to 38.1%. (iii) Global solar irradiance attenuation ranging up to 6.3%. (C) 2002 Elsevier Science Ltd. All rights reserved.

Abstract  Biomass burning represents an important source of atmospheric aerosols and greenhouse gases, yet little is known about its interannual variability or the underlying mechanisms regulating this variability at continental to global scales. Here we investigated fire emissions during the 8 year period from 1997 to 2004 using satellite data and the CASA biogeochemical model. Burned area from 2001–2004 was derived using newly available active fire and 500 m. burned area datasets from MODIS following the approach described by Giglio et al. (2006). ATSR and VIRS satellite data were used to extend the burned area time series back in time through 1997. In our analysis we estimated fuel loads, including organic soil layer and peatland fuels, and the net flux from terrestrial ecosystems as the balance between net primary production (NPP), heterotrophic respiration (Rh), and biomass burning, using time varying inputs of precipitation (PPT), temperature, solar radiation, and satellite-derived fractional absorbed photosynthetically active radiation (fAPAR). For the 1997–2004 period, we found that on average approximately 58 Pg C year−1 was fixed by plants as NPP, and approximately 95% of this was returned back to the atmosphere via Rh. Another 4%, or 2.5 Pg C year−1 was emitted by biomass burning; the remainder consisted of losses from fuel wood collection and subsequent burning. At a global scale, burned area and total fire emissions were largely decoupled from year to year. Total carbon emissions tracked burning in forested areas (including deforestation fires in the tropics), whereas burned area was largely controlled by savanna fires that responded to different environmental and human factors. Biomass burning emissions showed large interannual variability with a range of more than 1 Pg C year−1, with a maximum in 1998 (3.2 Pg C year−1) and a minimum in 2000 (2.0 Pg C year−1).

Abstract  ABSTRACT: BACKGROUND: The island factor of the cities of Las Palmas de Gran Canaria and Santa Cruz de Tenerife, along with their proximity to Africa and their meteorology, create a particular setting that influences the air quality of these cities and provides researchers an opportunity to analyze the acute effects of air-pollutants on daily mortality. METHODS: From 2000 to 2004, the relationship between daily changes in PM10, PM2.5, SO2, NO2, CO, and ozone levels and daily total mortality and mortality due to respiratory and heart diseases were assessed using Generalized Additive Poisson models controlled for potential confounders. The lag effect (up to five days) as well as the concurrent and previous day averages and distributed lag models were all estimated. Single and two pollutant models were also constructed. RESULTS: Daily levels of PM10, PM2.5, NO2, and SO2 were found to be associated with an increase in respiratory mortality in Santa Cruz de Tenerife and with increased heart disease mortality in Las Palmas de Gran Canaria, thus indicating an association between daily ozone levels and mortality from heart diseases. The effects spread over five successive days. SO2 was the only air pollutant significantly related with total mortality (lag 0). CONCLUSIONS: There is a short-term association between current exposure levels to air pollution and mortality (total as well as that due specifically to heart and respiratory diseases) in both cities. Risk coefficients were higher for respiratory and cardiovascular mortality, showing a delayed effect over several days.

Abstract  A single-column chemistry-climate model has been applied to evaluate peroxide exchanges measured over a coniferous forest during the BEWA2000 field campaign, July-August 2001. Simulations indicate that for suppressed nocturnal turbulent mixing, the H2O2 mixing ratios are sensitive to the representation of sources and sinks, e.g., non-stomatal uptake and chemical transformations, the latter tightly linked to atmosphere?biosphere NOx exchanges through its control on HO2 production. Comparison of observed and simulated H2O2 fluxes suggests that the commonly applied method to estimate uptake resistances results in a significant underestimation of the dry deposition flux. By using a very small surface uptake resistance, as observed, the modeled surface fluxes are still too low due to an underestimation of the simulated turbulent transport. Further, a reasonable agreement between simulated and observed methylhydroperoxide and hydroxymethylhydroperoxide mixing ratios in and above the canopy air is observed. Our analysis indicates the important role of daytime as well as nocturnal turbulent exchanges, which control the efficiency of dry deposition and downward transport of peroxides that are chemically produced higher up in the boundary layer. In turn, this chemical production depends on the upward transport of emitted precursor gases and their oxidization products. This demonstrates that improved simulations of atmosphere-biosphere peroxide exchanges rely heavily on improved model representations of boundary layer and canopy turbulent exchanges.

Abstract  To analyze cellular responses to ozone (O3), we performed a large-scale analysis of the Arabidopsis transcriptome after plants were exposed to O3 for 12 h. By using cDNA macroarray technology, we identified 205 non-redundant expressed sequence tags (ESTs) that were regulated by O3. Of these, 157 were induced and 48 were suppressed by O3. A substantial proportion of these ESTs had predicted functions in cell rescue/defense processes. Using these isolated ESTs, we also undertook a comprehensive investigation of how three hormones, ethylene (ET), jasmonic acid (JA), and salicylic acid (SA), interact to regulate O3-induced genes in various genetic backgrounds of Arabidopsis, such as the ET-insensitive ein2-1, JA-resistant jar1-1, and SA-insensitive npr1-1. The expression of half of the 157 induced genes, especially cell rescue/defense genes, was controlled by ET and JA signaling, indicating that O3-induced defense gene expression at this stage was mainly regulated by ET and JA. Clustering analysis of the 157 O3-induced gene expressions revealed that multiple signal pathways act mutually antagonistically to induce the expression of these genes, and many cell rescue/defense genes induced by ET and JA signal pathways were suppressed by SA signaling, suggesting that the SA pathway acts as a strong antagonist to gene expression induced by ET and JA signaling.

Abstract  The environment in which the encounter of antigen with the immune system occurs determines whether tolerance, infectious immunity, or autoimmunity results. Geographical areas with low supplies of vitamin D (for example Scandinavia) correlate with regions with high incidences of multiple sclerosis, arthritis, and diabetes. The active form of vitamin D has been shown to suppress the development of autoimmunity in experimental animal models. Furthermore, vitamin D deficiency increases the severity of at least experimental autoimmune encephalomyelitis (mouse multiple sclerosis). Targets for vitamin D in the immune system have been identified, and the mechanisms of vitamin D-mediated immunoregulation are beginning to be understood. This review discusses the possibility that vitamin D status is an environmental factor, which by shaping the immune system affects the prevalence rate for autoimmune diseases such as multiple sclerosis, arthritis, and juvenile diabetes.