Ambient O3 Concentrations Research Articles

Study of intra-city urban heat island intensity and its influence on atmospheric chemistry and energy consumption in Delhi

Urban heat island intensity (UHII) has been determined as difference in air temperatures between two locations of Delhi namely Safdarjung (SAFD) and National Physical Laboratory (NPL) regions which represent urban and sub-urban areas respectively. High UHI has been obtained in morning time as compared to day and night times, with the highest magnitude ranging from 2.8 to 3°C in spring (MAM), autumn (SON) and winter (DJF) seasons in morning hours (0700–0900h). Monsoon season (JJA) shows less UHII values compared to other seasons. Wind speed reduced the UHII. Larger impervious area (i.e. 67.2% in SAFD as compared to 33.4% in NPL), lesser vegetated area (i.e. 32.8% in SAFD as compared to 66.6% in NPL) and low Normalized Difference Vegetation Index (NDVI) value (0.15 in SAFD as compared to 0.24 in NPL) in SAFD area supports the existence of UHI there. Ambient O3 concentrations show maximum values during April and May for both regions and remain insignificantly influenced by UHI. Intra city temperature difference of 0.2–3°C is capable of raising electricity demand by 37.87–1856 GWh over the base electricity requirement of the city with corresponding increase in CO2 emissions by 0.031–1.52 million ton.

Bromine atom production and chain propagation during springtime Arctic ozone depletion events in Barrow, Alaska

Abstract. Ozone depletion events (ODEs) in the Arctic are primarily controlled by a bromine radical-catalyzed destruction mechanism that depends on the efficient production and recycling of Br atoms. Numerous laboratory and modeling studies have suggested the importance of heterogeneous recycling of Br through HOBr reaction with bromide on saline surfaces. On the other hand, the gas-phase regeneration of bromine atoms through BrO–BrO radical reactions has been assumed to be an efficient, if not dominant, pathway for Br reformation and thus ozone destruction. Indeed, it has been estimated that the rate of ozone depletion is approximately equal to twice the rate of the BrO self-reaction. Here, we use a zero-dimensional, photochemical model, largely constrained to observations of stable atmospheric species from the 2009 Ocean–Atmosphere–Sea Ice–Snowpack (OASIS) campaign in Barrow, Alaska, to investigate gas-phase bromine radical propagation and recycling mechanisms of bromine atoms for a 7-day period during late March. This work is a continuation of that presented in Thompson et al. (2015) and utilizes the same model construct. Here, we use the gas-phase radical chain length as a metric for objectively quantifying the efficiency of gas-phase recycling of bromine atoms. The gas-phase bromine chain length is determined to be quite small, at < 1.5, and highly dependent on ambient O3 concentrations. Furthermore, we find that Br atom production from photolysis of Br2 and BrCl, which is predominately emitted from snow and/or aerosol surfaces, can account for between 30 and 90 % of total Br atom production. This analysis suggests that condensed-phase production of bromine is at least as important as, and at times greater than, gas-phase recycling for the occurrence of Arctic ODEs. Therefore, the rate of the BrO self-reaction is not a sufficient estimate for the rate of O3 depletion.

Short-term effects of ozone air pollution on hospital admissions for myocardial infarction: A time-stratified case-crossover study in Taipei

ABSTRACTThis study was undertaken to determine whether there was a correlation between ambient ozone (O3) levels and number of hospital admissions for myocardial infarction (MI) in Taipei, Taiwan. Hospital admissions for MI and ambient air pollution data for Taipei were obtained for the period from 2006 to 2010. The relative risk (RR) of hospital admissions for MI was estimated using a time-stratified case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased RR for a number of MI admissions was significantly associated with higher O3 levels both on warm days (>23°C) and on cool days (<23°C). This observation was accompanied by an interquartile range elevation correlated with a 7% (95% CI = 2%–12%) and 17% (95% CI = 11%–25%) rise in number of MI admissions, respectively. In the two-pollutant models, no significant associations between ambient O3 concentrations and number of MI admissions were observed on warm days. However, on cool days, correlation between ambient O3 after inclusion of each of the other five pollutants, particulate matter (PM10 or PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2) or carbon monoxide (CO), and number of MI admissions remained significant. This study provides evidence that higher levels of ambient O3 increase the RR of number of hospital admissions for MI.

Estimating Ambient Ozone Effect of Kansas Rangeland Burning with Receptor Modeling and Regression Analysis

Prescribed rangeland burning in April is a long-standing practice in the Flint Hills region of eastern Kansas to maintain the tallgrass prairie ecosystem. The smoke plumes originating from these fires increases ambient PM2.5 concentrations and potentially contributes to ozone (O3) exceedances in downwind communities. Source apportionment research using Unmix modeling has been utilized to estimate contributions of Kansas rangeland burning to ambient PM2.5 concentrations. The objective of this study was to investigate the potential correlations between O3 and various sources of PM2.5 that are derived from receptor modeling, and then to specifically estimate contributions of Kansas rangeland burning to ambient O3 concentrations through regression analysis. Various daily meteorological data were used as predictor variables. Multiple regression models were developed for the eight-hour daily maximum O3 as well as the daily contributions of the five PM2.5 source categories that were derived from receptor modeling. Cross correlation was analyzed among residuals of the meteorological regression models for O3 and the daily contributions of the five PM2.5 source categories in order to identify the potential hidden correlation between O3 and PM2.5. The model including effects of meteorological variables and episodic contributions from fire and industrial emissions can explain up to 78% of O3 variability. For non-rainy days in April, the daily average contribution from prescribed rangeland burning to O3 was 1.8 ppb. On 3% of the days in April, prescribed rangeland burning contributed over 12.7 ppb to O3; and on 7% of the days in April, burning contributed more than 7.2 ppb to O3. When the intensive burning activities occur in days with high O3 background due to high solar radiation or O3 carryover from the previous day, the contributions from these episodic fire emissions could result in O3 exceedances of the National Ambient Air Quality Standards (NAAQS). The regression models developed in this study demonstrated that the most valuable predictors for O3 in the Flint Hills region include the O3 level on the previous day, total solar radiation, difference between daily maximum and minimum air temperature, and levels of episodic fire and industrial emissions. The long term goal is to establish an online O3 forecasting tool that can assist regulators and land managers in smoke management during the burning season so that the intensive burning activities can be planned to avoid forecasted high O3 days and thus prevent O3 exceedance.

Different responses of transgenic Bt rice and conventional rice to elevated ozone concentration.

To assess the different sensitivity to ozone (O3) between transgenic Bt Shanyou63 (Bt-SY63) and its nontransgenic counterpart Shanyou63 (SY63), the leaf gas exchange, yield, grain elements, and antioxidant enzymes were investigated by performing a pot experiment under ambient O3 concentration (A-O3) and elevated O3 concentration (1.5×A-O3, E-O3). Under A-O3, the chlorophyll content and yield of Bt-SY63 were significantly lower than those of SY63, whereas the stomatal conductance (Gs), cellular CO2 concentration (Ci), and Fe, Zn concentration showed the opposite trends. No significant difference was detected for malondialdehyde (MDA) content between two cultivars, although the antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities in Bt-SY63 tended to be higher than those in SY63. Exposure to E-O3 resulted in significant reduction for photosynthesis (Pn), yield and all grain elements (except for N) concentration in both varieties, and the extents in Bt-SY63 were much greater than those in SY63. Meanwhile, significant increases for MDA content by 30.6 and 23.7% in Bt-SY63 and SY63, respectively, were detected under E-O3. These results demonstrated that insertion of exogenous gene could induce several unintentional changes of Bt-SY63 in physiology and growth progress, compared with SY63 under ambient O3 concentration. On the other hand, the injury of Bt-SY63 caused by elevated O3 concentration was more severe than that of SY63. This study provided valuable baseline information for the commercial release and breeding strategies of Bt-SY63 under the projected future climate.

Photosynthetic responses to ozone of upper and lower canopy leaves of Fagus crenata Blume seedlings grown under different soil nutrient conditions

We aimed to clarify the effects of ozone (O3) on photosynthetic ability of upper and lower canopy leaves of Fagus crenata Blume seedlings grown under different soil nutrient conditions. To accomplish this objective, we analyzed the response of photosynthetic parameters such as maximum carboxylation rate (Vcmax) to cumulative stomatal O3 uptake (ΣFst) and reduction rate of Vcmax per unit ΣFst as an index of detoxification capacity for O3. The seedlings of Fagus crenata were grown for two growing seasons (2014–2015) in nine treatments comprised of a combination of three levels of gas treatments (charcoal-filtered air or 1.0- or 1.5-times ambient O3 concentration) and three levels of soil nutrient treatments (non-fertilized or a supply of relatively low or high concentrations of compound fertilizer). The nutrient supply significantly increased the degree of O3-induced reduction in Vcmax in September. However, nutrient supply did not significantly increase ΣFst and reduce the detoxification capacity for O3. On the other hand, the degree of O3-induced reduction in Vcmax of upper canopy leaves was higher as compared with that of lower canopy leaves in August due to the higher ΣFst. However, the reduction rate of Vcmax per unit ΣFst in lower canopy leaves was higher than that in upper canopy leaves, indicating lower detoxification capacity for O3 in lower canopy leaves. Reduction rate of Vcmax per unit ΣFst over the threshold, which is assumed to be proportional to gross photosynthetic rate, was similar between upper and lower canopy leaves. Therefore, capacity of photosynthetic CO2 assimilation is likely to be associated with detoxification capacity for O3 in upper and lower canopy leaves of F. crenata seedlings grown under different soil nutrient conditions.

A porous glass-based ozone sensing chip impregnated with potassium iodide and α-cyclodextrin

A chemical sensing chip for gaseous ozone (O3) has been fabricated by impregnating a porous glass sheet (8mm square and 1mm thick) with potassium iodide (KI) and α-cyclodextrin. The latter suppresses volatilization of iodine formed by the reaction of KI with O3. When passively exposed to air containing a sub-ppm level of O3 at a relative humidity (RH) of 90%, this chip changes from colorless to pale yellow, with an absorption peak at 360nm. A plot of change in absorbance at this wavelength against the total O3 exposure yields a good linear relationship passing through the origin. From the slope of the plot, the detection limit is estimated to be several ppb, assuming an exposure interval of 1h. Upon exposure at lower RH values of 50–70%, the chip turns reddish brown and absorbs over the range of 420 to 550nm, although its absorption maximum remains at 360nm. Absorption in the visible region under these conditions was found to be transient and thus unsuitable for measuring O3, although this visible absorption could be readily shifted to 360nm by applying higher RH values, such as 90%. From these results, it is concluded that hourly variations of ambient O3 concentration can be measured by observing the absorbance of the chip at 360nm, in conjunction with conditioning of the chip at 90% RH following the exposure interval.

Major heat waves of 2003 and 2006 and health outcomes in Prague

We have investigated the association between heat waves and mortality and hospital admissions for Prague inhabitants for the summer heat waves of August 2003 and July 2006. The effect of heat waves was investigated using negative binomial regression in a generalized additive model. We used a linear model on a logarithmic scale, having 1-day lagged temperature differences from the long-term average, 1-day lagged ambient O3 and PM10 concentration, relative humidity, simple “heat wave” indicator, and smooth seasonal effect as explanatory variables. We found a small increase in daily mortality for the examined period. This increase can be attributed to PM10 concentrations in most cases, and in fewer instances, to air temperature and O3 concentrations. The “heat wave” indicator did not significantly increase the relative risk; the same held for the relative humidity. For the general unstratified population, the highest increase in relative risk of 1.072 (95% CI 1.001–1.147) was observed for cardiovascular mortality and was associated with an increase in temperature of 10 °C, followed by an increase in relative risk of 1.056 (95% CI 1.025–1.087) for respiratory mortality associated with an increase in O3 concentrations by 10 μg.m−3. A higher risk in most cases was found for women. A significant increase of relative risk of 1.013 (95 % CI 1.002–1.024) due to PM10 was found for hospital admissions for cardiovascular causes. This issue should be studied further in view of the anticipated increase in meteorological extremes, including heat waves, in the future, to prepare prevention plans for eliminating their negative effects as far as possible.

Moderate drought did not affect the effectiveness of ethylenediurea (EDU) in protecting Populus cathayana from ambient ozone

A field study was conducted to evaluate the effects of ambient ozone (O3) on an O3-sensitive poplar (Populus cathayana) by using ethylenediurea (EDU) as a chemical protectant under two soil water treatments (well-watered (WW) and moderate drought (MD, 50–60% of WW in volumetric soil water content). EDU was applied as foliar spray at 0, 300, 450, and 600ppm. Photosynthetic parameters, pigment contents, leaf nitrogen, antioxidant capacity, growth, and biomass were measured. The 8h (9:00–17:00) average ambient O3 concentration was 71.7ppb, and AOT40 was 29.2ppmh during the experimental period (9 June to 21 September), which was high enough to cause plant injury. MD had significantly negative effects on P. cathayana, as indicated by reduced photosynthesis, growth, and biomass, and higher MDA contents. On the other hand, EDU significantly increased photosynthesis rate, chlorophyll a fluorescence, Vcmax and Jmax, photosynthetic pigments, total antioxidant capacity, tree growth and biomass accumulation, and reduced lipid peroxidation, but there was no significant interaction between EDU and drought for most parameters, indicating that EDU can efficiently protect Populus cathayana against ambient O3 and the protection was not affected by soil water contents when soil water reached moderate drought level. Among all doses, EDU at 450ppm provided maximum protection. Comparison of EDU-treated and non-treated P. cathayana could be used as a biomarker system in risk assessment of the effects of ambient O3 on forest health.

Limited effect of ozone reductions on the 20-year photosynthesis trend at Harvard forest.

Ozone (O3 ) damage to leaves can reduce plant photosynthesis, which suggests that declines in ambient O3 concentrations ([O3 ]) in the United States may have helped increase gross primary production (GPP) in recent decades. Here, we assess the effect of long-term changes in ambient [O3 ] using 20years of observations at Harvard forest. Using artificial neural networks, we found that the effect of the inclusion of [O3 ] as a predictor was slight, and independent of O3 concentrations, which suggests limited high-frequency O3 inhibition of GPP at this site. Simulations with a terrestrial biosphere model, however, suggest an average long-term O3 inhibition of 10.4% for 1992-2011. A decline of [O3 ] over the measurement period resulted in moderate predicted GPP trends of 0.02-0.04μmolCm-2 s-1 yr-1 , which is negligible relative to the total observed GPP trend of 0.41μmolCm-2 s-1 yr-1 . A similar conclusion is achieved with the widely used AOT40 metric. Combined, our results suggest that ozone reductions at Harvard forest are unlikely to have had a large impact on the photosynthesis trend over the past 20years. Such limited effects are mainly related to the slow responses of photosynthesis to changes in [O3 ]. Furthermore, we estimate that 40% of photosynthesis happens in the shade, where stomatal conductance and thus [O3 ] deposition is lower than for sunlit leaves. This portion of GPP remains unaffected by [O3 ], thus helping to buffer the changes of total photosynthesis due to varied [O3 ]. Our analyses suggest that current ozone reductions, although significant, cannot substantially alleviate the damages to forest ecosystems.

Ozone Impacts on Carbon Dynamics in Cotton

Ozone (O3) is a secondary atmospheric pollutant that causes widespread damage to vegetation, including cotton. The high temperatures and abundant sunlight that lead to good cotton yields also lead to production of O3. The early crop loss experiments of the 1970s identified upland cotton as particularly sensitive to O3. Exposure to ambient concentrations of O3 resulted in a 10 to &gt;15% loss in economic yield. More recent experiments with modern cultivars have confirmed damage to upland and Pima cultivars but have not assessed yield loss under agronomic conditions. It is likely that selection for yield in high O3 environments has led to inadvertent selection for tolerance to O3. Ozone reduces yield and fiber quality, mediated by O3-induced changes in gross photosynthesis, respiration, and translocation of current photosynthate out of source leaves. Ozone typically reduces root development and the root-to-shoot biomass ratio, which has secondary effects on plant growth and development and on water relations. Ozone also reduces stomatal conductance as a primary defense against entry of O3 into the plant, but this also restricts entry of CO2 and therefore photosynthesis. Ozone is clearly phytotoxic and impacts cotton as well as other species. Recent research has led to understanding many aspects of the mechanism of O3 damage and could lead to targeted approaches to improving O3 tolerance, and therefore, yield in O3-impacted production areas.

Stability of polycyclic aromatic compounds in polyurethane foam-type passive air samplers upon O3 exposure

Stability of polycyclic aromatic compounds (PACs) in polyurethane foam (PUF) disks upon O3 exposure was studied in a flow tube. A wide range of PACs was evaluated by spiking PUF disks with PACs and exposing to O3 at concentrations that were equivalent to two months exposure, a typical deployment period for these passive air samplers. Ambient concentrations of O3 (∼50 ppb) at 0% and 50% relative humidity (RH) were applied. At 0% RH, 23 of 68 PACs yielded more than 50% loss after exposure. The mean percent loss was 30% with perylene and 9,10-dimethylanthracene the most reactive polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs, respectively. At 50% RH, 77% of the studied PACs was stable upon O3 exposure (PACexposed/PACunexposed > 0.7). The mean percent loss was 17% and only 7 of 68 PACs yielded greater than 50% loss. In general, the reactivity of most of the PACs decreased at higher RH, except for the reactive PAHs (acenaphthylene, 2,3-dimethylanthracene, 9,10-dimethylanthracene, dibenzothiophene, and 2-methyldibenzothiophene) which demonstrated lower RH dependence. The experimental conditions in this study represent a worst case scenario for the stability of PACs sorbed to PUF. In reality, the sampling of PACs in ambient air represents an ‘aged’ component of PACs where the most reactive species have already partially been removed. Also, PACs in ambient air will be associated with the particle phase to varying extents that will help to enhance their stability. Therefore, under regular operating conditions, over a 2-month exposure, we expect a minimal error in the measurement of total concentration of PACs in air using the PUF disk passive sampler.

Spatial and temporal trends of ozone distribution in the Jizerské hory Mountains of the Czech Republic.

We present results of the 5-year monitoring of ambient O3 concentrations in a Central European medium altitude mountain forested area. O3 levels were measured at 11 sites between 714 and 1000 m a.s.l. in 2006-2010 vegetation seasons using Ogawa diffusive samplers. Our results reveal that O3 exposure in the Jizerské hory Mts. was relatively high and comparable with polluted sites in Southern Europe and in higher altitudes. O3 concentrations differed significantly between individual sites and in individual years. O3 concentrations showed clear dependence on altitude at sites with similar aspect. Its gradient for the entire 5-year period under review equaled 3.5 ppb/100 m of altitude, ranging between nearly 5 ppb/100 m of altitude in 2006 and nearly 3 ppb/100 m of altitude in 2010. O3 concentrations at the site with northern aspect were consistently significantly lower than at the site at similar altitude with southern aspect. O3 concentrations measured at the forest edge were consistently lower than those measured at the same site but at the forest clearing. It is evident that the macro-setting of the O3 monitoring site is crucial for obtaining reliable results with high representativeness for the area.

The effects of different calibration and frequency response correction methods on eddy covariance ozone flux measured with a dry chemiluminescence analyzer

Ozone (O3) flux (Fo) was measured over a wheat field in Yucheng, China, using the eddy covariance technique. A dry chemiluminescence fast-response O3 analyzer and a UV-absorption based slow-response O3 analyzer were used for measuring fast O3 concentration fluctuations and absolute concentrations, respectively. The main objective of this study was to determine a group of suitable methods for calculating Fo based on the performance of the two O3 analyzers in the field. We evaluated the effects of three calibration methods on Fo. These calibration methods include the ratio method (RM, it assumes that the fast-response analyzer’s signal-output is directly proportional to absolute ambient O3 concentration within a 30-min interval), the ratio offset method (ROM, it is based on the ratio method with analyzer’s offset modification), and the ratio variation method (RVM, it is based on the ratio method with the fast-response analyzer’s gain factor variation within a 30-min interval). Three frequency response corrections (analytic, revised analytic, and in-situ) for the estimation of Fo were also evaluated. Our results show that: (1) Compared to the O3 flux with the commonly-used method (RM), on average, the fluxes with ROM and RVM were decreased by about 9% and 7%, respectively. (2) Based on the spectral analysis, the fast-response O3 analyzer’s noise could cause random errors, but did not result in a systematic error in Fo. Tubing attenuation in O3 concentration fluctuations can cause up to 20% loss in Fo. (3) Frequency response corrections for Fo with the original analytic method, the in-situ method, and the revised analytic method were 34.6%, 23.8% and 25.4% on average, respectively.

Non-Linear Concentration-Response Relationships between Ambient Ozone and Daily Mortality.

BackgroundAmbient ozone (O3) concentration has been reported to be significantly associated with mortality. However, linearity of the relationships and the presence of a threshold has been controversial.ObjectivesThe aim of the present study was to examine the concentration-response relationship and threshold of the association between ambient O3 concentration and non-accidental mortality in 13 Japanese and Korean cities from 2000 to 2009.MethodsWe selected Japanese and Korean cities which have population of over 1 million. We constructed Poisson regression models adjusting daily mean temperature, daily mean PM10, humidity, time trend, season, year, day of the week, holidays and yearly population. The association between O3 concentration and mortality was examined using linear, spline and linear-threshold models. The thresholds were estimated for each city, by constructing linear-threshold models. We also examined the city-combined association using a generalized additive mixed model.ResultsThe mean O3 concentration did not differ greatly between Korea and Japan, which were 26.2 ppb and 24.2 ppb, respectively. Seven out of 13 cities showed better fits for the spline model compared with the linear model, supporting a non-linear relationships between O3 concentration and mortality. All of the 7 cities showed J or U shaped associations suggesting the existence of thresholds. The range of city-specific thresholds was from 11 to 34 ppb. The city-combined analysis also showed a non-linear association with a threshold around 30-40 ppb.ConclusionWe have observed non-linear concentration-response relationship with thresholds between daily mean ambient O3 concentration and daily number of non-accidental death in Japanese and Korean cities.

Field performance evaluation of Maxxam passive samplers for regional monitoring of ambient SO2, NO2 and O3 concentrations in Alberta, Canada

A field performance evaluation of Maxxam passive samplers was carried out for ambient concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2) and ground-level ozone (O3). Monthly passive and hourly continuous air monitoring data from four regional air monitoring networks in Alberta, Canada were evaluated over a 5-year period (2006–2010). Monthly concentrations were relatively low, ranging from 0.1 to 3.9 ppb, 0.2–18.1 ppb and 10.1–56.1 ppb for SO2, NO2 and O3, respectively. From duplicate passive sampling, geometric mean precision values were 17.9%, 14.8% and 4.7% for SO2, NO2 and O3, respectively. Geometric mean of the relative error (as a measure of accuracy) was 30% (median = 33%, interquartile range, IQR 15–63%) for SO2 and 32% (median = 40%, IQR = 25–64%) for NO2. O3 measurements had a better measure of accuracy with a geometic mean relative error of 12% (median = 17%, IQR = 8–27%) and met the acceptable level recommended by United States National Institute of Safety and Health (NIOSH) and the European Union (EU) Directive (±25%). From reduced major axis (RMA) analysis, bias (systematic error) is apparent in the Maxxam passive samplers in the field resulting in overestimation of ambient SO2 and O3 concentrations and underestimation of NO2 concentrations relative to continuous analyzers. Seasonal influences were observed for accuracy of passive SO2 and O3 measurements. A poor association was found between passive versus continuous concentrations for SO2 and O3 during the winter and the summer, respectively.

Association entre pollution atmosphérique et infarctus du myocarde sur base de la méthode cas-croisé

BackgroundA large number of studies have demonstrated an association between ambient air pollutant exposures and acute myocardial infarctions (AMI). Case-crossover methods are frequently used for analyzing the acute health effects of air pollution. Nevertheless, only a few studies controlled for potential confounders like other air pollutants and temperature. MethodsThe defined geographic entity for the collection of acute myocardial infarctions was composed of 15 municipalities in Charleroi. Charleroi is a relatively highly polluted region in Wallonia, the South of Belgium. The analyses presented hereafter concern patients in the 25–74 years age range over time from 1999 to 2009. Ambient concentrations of PM10, O3, NO2, CO and temperature were available from stationary monitors during this time period. A time-stratified case-crossover approach was applied. Season stratified analysis and analysis matching for environmental confounders were also performed. ResultsA total of 3303 AMIs were analyzed during the study period. For the entire year, O3 was significantly associated with AMI, OR=1.028 (CI95%: 1.003–1.054). The highest associations (for a 10μg.m−3 rise in pollutant levels) between air pollution and myocardial infarction were observed for PM10 and O3 during the warm period, OR=1.086 (CI95%: 1.020–1.151) and 1.064 (CI95%: 1.024–1.105), respectively. Matching cases and controls for temperature produced weaker association between O3 and AMI (OR=1.003, CI9 5%: 0.974–1.032). In contrast, this matching had no effect on the association between PM10 and AMI. The adjustment for NO2 concentration decreased the association between PM10 and AMI. ConclusionsThe results of this study reinforce the evidence of the short-term effects of air pollution on acute myocardial infarction, especially during the warm season. This also suggests that the case-crossover method is a suitable tool in studying the association between acute events and air pollution. Controlling for potential environmental confounding effects is also feasible with this method.

Modeling and Prediction of Hourly Ambient Ozone (O3) and Oxides of Nitrogen (NOx) Concentrations Using Artificial Neural Network and Decision Tree Algorithms for an Urban Intersection in India

AbstractThe present study attempts to predict hourly ozone (O3) and oxides of nitrogen (NOx) concentrations near a traffic intersection in megacity Delhi, India, using artificial neural network (ANN) with the Levenberg–Maquardt (LM) algorithm and decision tree algorithms [e.g., reduced error pruning tree (REPTree) and M5 P tree model]. The hourly averages of input variables of meteorological, traffic volume, and transport emissions along with target values of monitored ambient air concentrations of O3 and oxides of nitrogen NOx were used for model development. The LM, REPTree, and M5 P algorithm models were developed by training, validation, and testing of input and target data. Statistical agreement between observed and predicted values is assessed by coefficient of correlation (CC), mean square error (MSE), root mean square error (RMSE), normalized mean square Error (NMSE), and Nash–Sutcliffe efficiency index (N-S Index). Results show that the performance of the M5 P model is superior to ANN and REPTree...

Fungi in the future: interannual variation and effects of atmospheric change on arbuscular mycorrhizal fungal communities.

Understanding the natural dynamics of arbuscular mycorrhizal (AM) fungi and their response to global environmental change is essential for the prediction of future plant growth and ecosystem functions. We investigated the long-term temporal dynamics and effect of elevated atmospheric carbon dioxide (CO2) and ozone (O3) concentrations on AM fungal communities.Molecular methods were used to characterize the AM fungal communities of soybean (Glycine max) grown under elevated and ambient atmospheric concentrations of both CO2 and O3 within a free air concentration enrichment experiment in three growing seasons over 5 yr.Elevated CO2 altered the community composition of AM fungi, increasing the ratio of Glomeraceae to Gigasporaceae. By contrast, no effect of elevated O3 on AM fungal communities was detected. However, the greatest compositional differences detected were between years, suggesting that, at least in the short term, large-scale interannual temporal dynamics are stronger mediators than atmospheric CO2 concentrations of AM fungal communities.We conclude that, although atmospheric change may significantly alter AM fungal communities, this effect may be masked by the influences of natural changes and successional patterns through time. We suggest that changes in carbon availability are important determinants of the community dynamics of AM fungi.

Addressing the ability of a land biosphere model to predict key biophysical vegetation characterisation parameters with Global Sensitivity Analysis

Sensitivity Analysis (SA) of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model has been performed in this study using a cutting edge and robust Global Sensitivity Analysis (GSA) approach, based on the use of the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) tool. The sensitivity of the following model outputs was evaluated: the ambient CO2 concentration, the rate of CO2 uptake by the plant, the ambient O3 concentration, the flux of O3 from the air to the plant/soil boundary and the flux of O3 taken up by the plant alone. The most sensitive model inputs for the majority of outputs were: The Leaf Area Index (LAI), Fractional Vegetation Cover (Fr), Cuticle Resistance (CR) and Vegetation Height (VH). The influence of the external CO2 on the leaf and O3 concentration in the air as input parameters was also significant. Our study provides an important step forward in the global efforts towards SimSphere verification given the increasing interest in its use as an independent modelling or educational tool. Results of this study are also timely given the ongoing global efforts focused on deriving, at an operational level, spatio-temporal estimates of energy fluxes and soil moisture content using SimSphere synergistically with Earth Observation (EO) data.