994 resultados para Air Pollutants
Resumo:
Exposure to nitrogen oxides (NOx) emitted by burning fossil fuels has been associated with respiratory diseases. We aimed to estimate the effects of NOx exposure on mortality owing to respiratory diseases in residents of Taubat, So Paulo, Brazil, of all ages and both sexes. This time-series ecological study from August 1, 2011 to July 31, 2012 used information on deaths caused by respiratory diseases obtained from the Health Department of Taubat. Estimated daily levels of pollutants (NOx, particulate matter, ozone, carbon monoxide) were obtained from the Centro de Previso de Tempo e Estudos Climticos Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System. These environmental variables were used to adjust the multipollutant model for apparent temperature. To estimate association between hospitalizations owing to asthma and air pollutants, generalized additive Poisson regression models were developed, with lags as much as 5 days. There were 385 deaths with a daily mean (SD) of 1.051.03 (range: 0-5). Exposure to NOx was significantly associated with mortality owing to respiratory diseases: relative risk (RR)=1.035 (95% confidence interval [CI]: 1.008-1.063) for lag 2, RR=1.064 (95%CI: 1.017-1.112) lag 3, RR=1.055 (95%CI: 1.025-1.085) lag 4, and RR=1.042 (95%CI: 1.010-1.076) lag 5. A 3 g/m3 reduction in NOx concentration resulted in a decrease of 10-18 percentage points in risk of death caused by respiratory diseases. Even at NOx concentrations below the acceptable standard, there is association with deaths caused by respiratory diseases.
Resumo:
Lobjectif de cette tude est de dterminer certains paramtres respiratoires et cardiovasculaires chez des sujets de tous ges pour utilisation, titre dintrants physiologiques, en modlisation toxicocintique et en analyse du risque toxique. La base de donnes utilise est tire de la littrature. Il sagit de mesures portant sur la dpense dnergie quotidienne de base et la dpense dnergie quotidienne de totale obtenues, lune par calorimtrie indirecte, lautre par double marquage isotopique des molcules deau. Selon le type dunit retenu, les valeurs les plus leves au 99e centile des taux quotidiens dinhalation sont obtenues chez des adolescentes et des femmes ges de 11 55 ans souffrant dembonpoint ou dobsit, durant leur 36e semaine de grossesse (47,31 m/jour), ainsi que chez des garons de poids corporel normal gs de 2,6 moins de 6 mois (1,138 m/kg-jour) et de 10 moins de 16,5 ans (22,29 m/m-jour). Chez les enfants et les adolescents de poids corporel normal gs de 5 moins de 16.5 ans, les valeurs pour lcart entre le 2,5e au 99e centile sont gnralement plus leves que celles obtenues chez les sujets plus gs : taux de ventilation minute, 0,132 0,774 L/kg-min ou 4,42 21,69 L/m-min versus 0,076 0,461 L/kg-min ou 2,80 16,99 L/m-min; taux de ventilation alvolaire, 0,093 0,553 L/kg-min ou 3,09 15,53 L/m-min versus 0,047 0,312 L/kg-min ou 1,73 11,63 L/m-min; dbit cardiaque, 0,065 0,330 L/kg-min ou 2,17 9,46 L/m-min versus 0,045 0,201 L/kg-min ou 1,63 7,24 L/m-min; ratio de ventilation-perfusion, 1,12 2,16 versus 0,78 2,40. Il faut conclure que les apports inhals en polluants, exprims en ug/kg-min ou ug/m-min sont plus levs chez les enfants que chez les sujets plus gs pour des concentrations dexposition comparables. Dautres donnes montrent quil en est de mme pour les apports inhals par unit de poids corporel chez les femmes enceintes et les femmes qui allaitent par rapport des sujets males dge comparable. Lensemble des rsultats obtenus suggre notamment que les valeurs des NOAELH de Sant Canada pourraient tre abaisses par un facteur de 2,6 par utilisation du 99e centile le plus lev des taux quotidiens dinhalation chez les enfants; le taux de ventilation minute de 20,83 L/min approxim pour une journe de travail de 8 heures peut tre considr comme tant conservateur ; par contre, lutilisation du taux quotidien dinhalation de 0,286 m/kg-jour (c.--d. 20 m/jour pour un adulte de poids corporel de 70 kg) est inapproprie en analyse et gestion du risque lorsquapplique lensemble de la population.
Resumo:
Lexposition quotidienne aux polluants atmosphriques tels que le dioxyde de soufre, les particules fines (PM2.5) et lozone en milieu urbain sont associs des effets nfastes sur la sant respiratoire des enfants. Des tudes pidmiologiques transversales rapportent des associations entre la pollution atmosphrique et des problmes de sant respiratoires chez les enfants en milieu industriel telles que la prvalence de lasthme et de l'hyperractivit bronchique. Ces tudes pidmiologiques transversales ne permettent pas dvaluer les effets sur la sant dune exposition de courte dure. Peu dtudes ont valu les effets respiratoires des expositions aigus chez les enfants la pollution atmosphrique dmissions industrielles. Dans ce mmoire, nous avons analys lassociation entre lexposition journalire aux missions dune aluminerie et lhospitalisation pour problmes respiratoires (asthme, bronchiolite) chez les enfants de Shawinigan. Pour tudier ces effets des expositions aigus, nous avons utilis le devis pidmiologique de type case-crossover qui compare lexposition lors des jours cas (jour dhospitalisation) avec lexposition lors des jours contrle (exposition du mme individu, les mmes jours de la semaine, durant le mme mois). Les variables dexposition suivantes ont t calcules pour les enfants vivants dans un rayon de 7.5 km de lindustrie et pour ceux habitant moins de 2.5 km de la station de mesure de polluants prs de lindustrie : i) le nombre dheures par jour durant lesquelles la rsidence de chaque enfant recevait le panache de fume de lindustrie. ii) les concentrations journalires de PM2.5 et de SO2 (moyenne et maximales) de la station de mesure des polluants localise prs de lindustrie. Des rgressions logistiques conditionnelles ont t utilises pour estimer les rapports de cotes (OR) et leurs intervalles de confiance 95% (IC95%). Au total, 429 hospitalisations denfants pour asthme et bronchiolite ont t recenses pendant la priode dtude allant de 1999 2008. Le risque dhospitalisations pour asthme et bronchiolite a augment avec laugmentation du nombre dheures dexposition aux fumes de lindustrie, chez les enfants de moins de 5 ans. Pour les enfants de 2-4 ans, cette association tait : OR : 1.27, pour un interquartile de 4.8 heures/jour; intervalle de confiance 95%: 1.03-1.56. Des tendances moins prononces sont notes avec les niveaux de SO2 et de PM2.5. Cette tude suggre que lexposition journalire aux missions industrielles identifies par lexposition horaire des vents venant de lusine pourrait tre associe une exacerbation des problmes respiratoires chez les jeunes enfants. De plus, leffet plus prononc avec la variable dexposition base sur les vents suggre un effet dcoulant des polluants autres que ceux mesurs (SO2 et PM2.5), possiblement comme les hydrocarbures aromatiques polycycliques (HAP).
Resumo:
La majorit des tudes qui ont examin les effets respiratoires dune exposition de courte dure la pollution de lair ont t ralises en milieu urbain. En milieu pollu par des sources industrielles, la nature de lexposition diffre de celle en milieu urbain. Le premier objectif de ce mmoire visait une recension des tudes traitant de lassociation entre les effets respiratoires chez lenfant et lexposition aux missions de polluants industriels. La majorit des tudes suggrent que lexposition aux missions de polluants mis par des industries est associe un accroissement des problmes respiratoires. Dans ces tudes, leffet de lexposition de courte dure a rarement t tudi. Lautre objectif du mmoire tait dvaluer lassociation entre une exposition journalire aux missions de pollution atmosphrique dun complexe industriel (deux fonderies et une usine de raffinage de lalumine) du Saguenay, Qubec, et les hospitalisations pour problmes respiratoires des enfants de 0 4 ans vivant prs de celles-ci (<7.5 km), laide dune tude pidmiologique de type cas-crois. Le pourcentage dheures o le domicile de lenfant tait sous les vents provenant de la direction du complexe industriel et les maxima et moyennes journalires des concentrations de dioxyde de soufre (SO2) et de particules fines (PM2.5) ont t recueillis du 1er janvier 2001 au 31 dcembre 2010 afin destimer lexposition. Des rgressions logistiques conditionnelles ont t employes pour estimer les rapports de cotes (OR) et les intervalles de confiance 95%. Les hospitalisations pour asthme et bronchiolite chez les jeunes enfants taient associes laugmentation de lexposition journalire aux missions, estime par le pourcentage dheures sous les vents. Les rsultats de ce mmoire suggrent que lexposition aux missions industrielles de polluants de lair est associe des effets respiratoires chez les enfants.
Resumo:
Les impacts des changements climatiques sur la population sont nombreux et ont t relativement bien documents, ce qui nest pas le cas de ces impacts sur la sant et la scurit des travailleurs. Lobjectif de cette thse est de documenter les effets ngatifs des changements climatiques sur la sant et la scurit des travailleurs dans une rgion dun pays industrialis climat tempr, comme le Qubec. Pour y arriver, deux approches ont t utilises : a) les dangers et les effets sanitaires ont t identifis par une revue de la littrature valide par des experts nationaux et internationaux, et des priorits de recherche ont t tablies laide dune mthode de consultation itrative, b) des modles statistiques, utiles lestimation des impacts sanitaires des changements climatiques, ont t dvelopps pour apprcier les associations entre la survenue de lsions professionnelles et lexposition des travailleurs aux chaleurs estivales et lozone troposphrique, deux problmatiques proccupantes pour le Qubec. Le bilan des connaissances a mis en vidence cinq catgories de dangers pouvant affecter directement ou indirectement la sant et la scurit des travailleurs au Qubec (vagues de chaleur, polluants de lair, rayonnements ultraviolets, vnements mtorologiques extrmes, maladies vectorielles transmissibles et zoonoses) et cinq conditions pouvant entraner des modifications dans lenvironnement de travail et pouvant ultimement affecter ngativement la sant et la scurit des travailleurs (changements dans les mthodes agricoles et dlevage, altrations dans lindustrie de la pche, perturbations de lcosystme forestier, dgradation de lenvironnement bti et mergence de nouvelles industries vertes). Quant aux modlisations, elles suggrent que les indemnisations quotidiennes pour des maladies lies la chaleur et pour des accidents de travail augmentent avec les tempratures estivales, et que ces associations varient selon lge des travailleurs, le secteur industriel et la catgorie professionnelle (manuelle vs autre). Des associations positives statistiquement non significatives entre les indemnisations pour des atteintes respiratoires aigus et les concentrations dozone troposphrique ont aussi t observes. Dans lensemble, cette thse a permis de dgager douze pistes de recherche prioritaires pour le Qubec se rapportant lacquisition de connaissances, la surveillance pidmiologique et au dveloppement de mthodes dadaptation. Selon les rsultats de cette recherche, les intervenants en sant au travail et les dcideurs devraient dployer des efforts pour protger la sant et la scurit des travailleurs et mettre en place des actions prventives en vue des changements climatiques.
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The problem of using information available from one variable X to make inferenceabout another Y is classical in many physical and social sciences. In statistics this isoften done via regression analysis where mean response is used to model the data. Onestipulates the model Y = (X) +. Here (X) is the mean response at the predictor variable value X = x, and = Y - (X) is the error. In classical regression analysis, both (X; Y ) are observable and one then proceeds to make inference about the mean response function (X). In practice there are numerous examples where X is not available, but a variable Z is observed which provides an estimate of X. As an example, consider the herbicidestudy of Rudemo, et al. [3] in which a nominal measured amount Z of herbicide was applied to a plant but the actual amount absorbed by the plant X is unobservable. As another example, from Wang [5], an epidemiologist studies the severity of a lung disease, Y , among the residents in a city in relation to the amount of certain air pollutants. The amount of the air pollutants Z can be measured at certain observation stations in the city, but the actual exposure of the residents to the pollutants, X, is unobservable and may vary randomly from the Z-values. In both cases X = Z+error: This is the so called Berkson measurement error model.In more classical measurement error model one observes an unbiased estimator W of X and stipulates the relation W = X + error: An example of this model occurs when assessing effect of nutrition X on a disease. Measuring nutrition intake precisely within 24 hours is almost impossible. There are many similar examples in agricultural or medical studies, see e.g., Carroll, Ruppert and Stefanski [1] and Fuller [2], , among others. In this talk we shall address the question of fitting a parametric model to the re-gression function (X) in the Berkson measurement error model: Y = (X) + ; X = Z + ; where and are random errors with E() = 0, X and are d-dimensional, and Z is the observable d-dimensional r.v.
Resumo:
Time series regression models are especially suitable in epidemiology for evaluating short-term effects of time-varying exposures on health. The problem is that potential for confounding in time series regression is very high. Thus, it is important that trend and seasonality are properly accounted for. Our paper reviews the statistical models commonly used in time-series regression methods, specially allowing for serial correlation, make them potentially useful for selected epidemiological purposes. In particular, we discuss the use of time-series regression for counts using a wide range Generalised Linear Models as well as Generalised Additive Models. In addition, recently critical points in using statistical software for GAM were stressed, and reanalyses of time series data on air pollution and health were performed in order to update already published. Applications are offered through an example on the relationship between asthma emergency admissions and photochemical air pollutants
Resumo:
Introduccin: la contaminacin atmosfrica no solo tiene efectos sobre el sistema respiratorio sino tambin sobre el cardiovascular. El objetivo de este estudio es generar evidencia que permita establecer una asociacin entre el infarto agudo del miocardio y la concentracin de PM10 en el ambiente como un estudio preliminar para un grupo de pacientes en Bogot. Metodologa: la asociacin entre la concentracin del material particulado (en este caso PM10 medido en la estacin ms cercana del lugar reportado por el paciente) y el infarto agudo del miocardio se estableci utilizando el diseo case crossover. Se utiliz informacin de las historias clnicas de los pacientes con infarto agudo del miocardio que ingresaron al Servicio de Urgencias de la FSFB, y las concentraciones de PM10 medido en la estacin ms cercana al lugar de inicio de los sntomas de sndrome coronario agudo, reportado por el paciente. Resultados: se encontr que la asociacin entre la concentracin de PM10 y el diagnstico de infarto agudo del miocardio es estadsticamente significativa teniendo en cuenta tres momentos de control: 2 horas antes del evento, 24 horas antes del evento y 48 horas antes del evento. Discusin: este estudio sugiere que las altas concentraciones de material particulado en el ambiente son un factor de riesgo para el desarrollo de infarto agudo del miocardio especialmente en personas con enfermedad coronaria subyacente. Con esta investigacin se demuestra la importancia de generar acciones que disminuyan la contaminacin de la ciudad y de esta forma proteger la salud de las personas.
Resumo:
Un problema de salud ambiental relevante es la contaminacin del aire generado por diferentes factores, uno de ellos es la carga microbiana. El estudio evidencia la presencia de estos contaminantes del aire como son los bioaerosoles cultivables y contables en las reas de los edificios administrativos estudiados la cual podra afectar la calidad del aire interior. Se realiz un estudio observacional de corte transversal que permiti conocer y establecer las caractersticas de la carga microbiana presente relacionada con bioaerosoles cultivables y contables en los sistemas de ventilacin mecnica en tres edificios administrativos de la ciudad de Bogot en el periodo 2012 a 2013 y, la asociacin o no entre variables de inters. Los bioaerosoles cultivables y contables encontrados con mayores porcentajes en las muestras tomadas fueron comunes a los tres edificios as: Aspergillus sp. se encontr en el 77,2% (61) de las muestras para el edifico uno, mientras que para el dos fue de 91% (30) de las muestras y para el edificio tres 100% (19) de las muestras tomadas; seguido por el gnero Penicillium sp. del cual se encontr 60,8% (48) de las muestras para el edificio uno, para el edificio dos 87,9% (29) de las muestras y para el edificio tres 94,7% (18) de las muestras. Otro gnero encontrado en porcentajes altos en los tres edificios fue el Cladosporium sp. , en el edificio uno 41,8% (33) de las muestras, mientras que para el edificio dos correspondi al 100% (33) de las muestra y finalmente para el edificio tres 84,2% (16) de las muestras analizadas. Los hallazgos se correlacionan con lo reportado por la literatura.
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The North Atlantic Oscillation (NAO) is an important large-scale atmospheric circulation that influences the European countries climate. This study evaluated NAO impact in air quality in Porto Metropolitan Area (PMA), Portugal, for the period 2002-2006. NAO, air pollutants and meteorological data were statistically analyzed. All data were obtained from PMA Weather Station, PMA Air Quality Stations and NOAA analysis. Two statistical methods were applied in different time scale : principal component and correlation coefficient. Annual time scale, using multivariate analysis (PCA, principal component analysis), were applied in order to identified positive and significant association between air pollutants such as PM10, PM2.5, CO, NO and NO2, with NAO. On the other hand, the correlation coefficient using seasonal time scale were also applied to the same data. The results of PCA analysis present a general negative significant association between the total precipitation and NAO, in Factor 1 and 2 (explaining around 70% of the variance), presented in the years of 2002, 2004 and 2005. During the same years, some air pollutants (such as PM10, PM2.5, SO2, NOx and CO) present also a positive association with NAO. The O3 shows as well a positive association with NAP during 2002 and 2004, at 2nd Factor, explaining 30% of the variance. From the seasonal analysis using correlation coefficient, it was found significant correlation between PM10 (0.72., p<0.05, in 2002), PM2.5 (0 74, p<0.05, in 2004), and SO2 (0.78, p<0.01, in 2002) with NAO during March-December (no winter period) period. Significant associations between air pollutants and NAO were also verified in the winter period (December to April) mainly with ozone (2005, r=-0.55, p.<0.01). Once that human health and hospital morbidities may be affected by air pollution, the results suggest that NAO forecast can be an important tool to prevent them, in the Iberian Peninsula and specially Portugal.
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The evaluation of life cycle greenhouse gas emissions from power generation with carbon capture and storage (CCS) is a critical factor in energy and policy analysis. The current paper examines life cycle emissions from three types of fossil-fuel-based power plants, namely supercritical pulverized coal (super-PC), natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC), with and without CCS. Results show that, for a 90% CO2 capture efficiency, life cycle GHG emissions are reduced by 75-84% depending on what technology is used. With GHG emissions less than 170 g/kWh, IGCC technology is found to be favorable to NGCC with CCS. Sensitivity analysis reveals that, for coal power plants, varying the CO2 capture efficiency and the coal transport distance has a more pronounced effect on life cycle GHG emissions than changing the length of CO2 transport pipeline. Finally, it is concluded from the current study that while the global warming potential is reduced when MEA-based CO2 capture is employed, the increase in other air pollutants such as NOx and NH3 leads to higher eutrophication and acidification potentials.
Resumo:
SCIENTIFIC SUMMARY Globally averaged total column ozone has declined over recent decades due to the release of ozone-depleting substances (ODSs) into the atmosphere. Now, as a result of the Montreal Protocol, ozone is expected to recover from the effects of ODSs as ODS abundances decline in the coming decades. However, a number of factors in addition to ODSs have led to and will continue to lead to changes in ozone. Discriminating between the causes of past and projected ozone changes is necessary, not only to identify the progress in ozone recovery from ODSs, but also to evaluate the effectiveness of climate and ozone protection policy options. Factors Affecting Future Ozone and Surface Ultraviolet Radiation At least for the next few decades, the decline of ODSs is expected to be the major factor affecting the anticipated increase in global total column ozone. However, several factors other than ODS will affect the future evolution of ozone in the stratosphere. These include changes in (i) stratospheric circulation and temperature due to changes in long-lived greenhouse gas (GHG) abundances, (ii) stratospheric aerosol loading, and (iii) source gases of highly reactive stratospheric hydrogen and nitrogen compounds. Factors that amplify the effects of ODSs on ozone (e.g., stratospheric aerosols) will likely decline in importance as ODSs are gradually eliminated from the atmosphere. Increases in GHG emissions can both positively and negatively affect ozone. Carbon dioxide (CO2)-induced stratospheric cooling elevates middle and upper stratospheric ozone and decreases the time taken for ozone to return to 1980 levels, while projected GHG-induced increases in tropical upwelling decrease ozone in the tropical lower stratosphere and increase ozone in the extratropics. Increases in nitrous oxide (N2O) and methane (CH4) concentrations also directly impact ozone chemistry but the effects are different in different regions. The Brewer-Dobson circulation (BDC) is projected to strengthen over the 21st century and thereby affect ozone amounts. Climate models consistently predict an acceleration of the BDC or, more specifically, of the upwelling mass flux in the tropical lower stratosphere of around 2% per decade as a consequence of GHG abundance increases. A stronger BDC would decrease the abundance of tropical lower stratospheric ozone, increase poleward transport of ozone, and could reduce the atmospheric lifetimes of long-lived ODSs and other trace gases. While simulations showing faster ascent in the tropical lower stratosphere to date are a robust feature of chemistry-climate models (CCMs), this has not been confirmed by observations and the responsible mechanisms remain unclear. Substantial ozone losses could occur if stratospheric aerosol loading were to increase in the next few decades, while halogen levels are high. Stratospheric aerosol increases may be caused by sulfur contained in volcanic plumes entering the stratosphere or from human activities. The latter might include attempts to geoengineer the climate system by enhancing the stratospheric aerosol layer. The ozone losses mostly result from enhanced heterogeneous chemistry on stratospheric aerosols. Enhanced aerosol heating within the stratosphere also leads to changes in temperature and circulation that affect ozone. Surface ultraviolet (UV) levels will not be affected solely by ozone changes but also by the effects of climate change and by air quality change in the troposphere. These tropospheric effects include changes in clouds, tropospheric aerosols, surface reflectivity, and tropospheric sulfur dioxide (SO2) and nitrogen dioxide (NO2). The uncertainties in projections of these factors are large. Projected increases in tropospheric ozone are more certain and may lead to reductions in surface erythemal (sunburning) irradiance of up to 10% by 2100. Changes in clouds may lead to decreases or increases in surface erythemal irradiance of up to 15% depending on latitude. Expected Future Changes in Ozone Full ozone recovery from the effects of ODSs and return of ozone to historical levels are not synonymous. In this chapter a key target date is chosen to be 1980, in part to retain the connection to previous Ozone Assessments. Noting, however, that decreases in ozone may have occurred in some regions of the atmosphere prior to 1980, 1960 return dates are also reported. The projections reported on in this chapter are taken from a recent compilation of CCM simulations. The ozone projections, which also form the basis for the UV projections, are limited in their representativeness of possible futures since they mostly come from CCM simulations based on a single GHG emissions scenario (scenario A1B of Emissions Scenarios. A Special Report of Working Group III of the Intergovernmental Panel on Climate Change, Cambridge University Press, 2000) and a single ODS emissions scenario (adjusted A1 of the previous (2006) Ozone Assessment). Throughout this century, the vertical, latitudinal, and seasonal structure of the ozone distribution will be different from what it was in 1980. For this reason, ozone changes in different regions of the atmosphere are considered separately. The projections of changes in ozone and surface clear-sky UV are broadly consistent with those reported on in the 2006 Assessment. The capability of making projections and attribution of future ozone changes has been improved since the 2006 Assessment. Use of CCM simulations from an increased number of models extending through the entire period of ozone depletion and recovery from ODSs (19602100) as well as sensitivity simulations have allowed more robust projections of long-term changes in the stratosphere and of the relative contributions of ODSs and GHGs to those changes. Global annually averaged total column ozone is projected to return to 1980 levels before the middle of the century and earlier than when stratospheric halogen loading returns to 1980 levels. CCM projections suggest that this early return is primarily a result of GHG-induced cooling of the upper stratosphere because the effects of circulation changes on tropical and extratropical ozone largely cancel. Global (90S90N) annually averaged total column ozone will likely return to 1980 levels between 2025 and 2040, well before the return of stratospheric halogens to 1980 levels between 2045 and 2060. Simulated changes in tropical total column ozone from 1960 to 2100 are generally small. The evolution of tropical total column ozone in models depends on the balance between upper stratospheric increases and lower stratospheric decreases. The upper stratospheric increases result from declining ODSs and a slowing of ozone destruction resulting from GHG-induced cooling. Ozone decreases in the lower stratosphere mainly result from an increase in tropical upwelling. From 1960 until around 2000, a general decline is simulated, followed by a gradual increase to values typical of 1980 by midcentury. Thereafter, although total column ozone amounts decline slightly again toward the end of the century, by 2080 they are no longer expected to be affected by ODSs. Confidence in tropical ozone projections is compromised by the fact that simulated decreases in column ozone to date are not supported by observations, suggesting that significant uncertainties remain. Midlatitude total column ozone is simulated to evolve differently in the two hemispheres. Over northern midlatitudes, annually averaged total column ozone is projected to return to 1980 values between 2015 and 2030, while for southern midlatitudes the return to 1980 values is projected to occur between 2030 and 2040. The more rapid return to 1980 values in northern midlatitudes is linked to a more pronounced strengthening of the poleward transport of ozone due to the effects of increased GHG levels, and effects of Antarctic ozone depletion on southern midlatitudes. By 2100, midlatitude total column ozone is projected to be above 1980 values in both hemispheres. October-mean Antarctic total column ozone is projected to return to 1980 levels after midcentury, later than in any other region, and yet earlier than when stratospheric halogen loading is projected to return to 1980 levels. The slightly earlier return of ozone to 1980 levels (20452060) results primarily from upper stratospheric cooling and resultant increases in ozone. The return of polar halogen loading to 1980 levels (20502070) in CCMs is earlier than in empirical models that exclude the effects of GHG-induced changes in circulation. Our confidence in the drivers of changes in Antarctic ozone is higher than for other regions because (i) ODSs exert a strong influence on Antarctic ozone, (ii) the effects of changes in GHG abundances are comparatively small, and (iii) projections of ODS emissions are more certain than those for GHGs. Small Antarctic ozone holes (areas of ozone <220 Dobson units, DU) could persist to the end of the 21st century. March-mean Arctic total column ozone is projected to return to 1980 levels two to three decades before polar halogen loading returns to 1980 levels, and to exceed 1980 levels thereafter. While CCM simulations project a return to 1980 levels between 2020 and 2035, most models tend not to capture observed low temperatures and thus underestimate present-day Arctic ozone loss such that it is possible that this return date is biased early. Since the strengthening of the Brewer-Dobson circulation through the 21st century leads to increases in springtime Arctic column ozone, by 2100 Arctic ozone is projected to lie well above 1960 levels. Uncertainties in Projections Conclusions dependent on future GHG levels are less certain than those dependent on future ODS levels since ODS emissions are controlled by the Montreal Protocol. For the six GHG scenarios considered by a few CCMs, the simulated differences in stratospheric column ozone over the second half of the 21st century are largest in the northern midlatitudes and the Arctic, with maximum differences of 2040 DU between the six scenarios in 2100. There remain sources of uncertainty in the CCM simulations. These include the use of prescribed ODS mixing ratios instead of emission fluxes as lower boundary conditions, the range of sea surface temperatures and sea ice concentrations, missing tropospheric chemistry, model parameterizations, and model climate sensitivity. Geoengineering schemes for mitigating climate change by continuous injections of sulfur-containing compounds into the stratosphere, if implemented, would substantially affect stratospheric ozone, particularly in polar regions. Ozone losses observed following large volcanic eruptions support this prediction. However, sporadic volcanic eruptions provide limited analogs to the effects of continuous sulfur emissions. Preliminary model simulations reveal large uncertainties in assessing the effects of continuous sulfur injections. Expected Future Changes in Surface UV. While a number of factors, in addition to ozone, affect surface UV irradiance, the focus in this chapter is on the effects of changes in stratospheric ozone on surface UV. For this reason, clear-sky surface UV irradiance is calculated from ozone projections from CCMs. Projected increases in midlatitude ozone abundances during the 21st century, in the absence of changes in other factors, in particular clouds, tropospheric aerosols, and air pollutants, will result in decreases in surface UV irradiance. Clear-sky erythemal irradiance is projected to return to 1980 levels on average in 2025 for the northern midlatitudes, and in 2035 for the southern midlatitudes, and to fall well below 1980 values by the second half of the century. However, actual changes in surface UV will be affected by a number of factors other than ozone. In the absence of changes in other factors, changes in tropical surface UV will be small because changes in tropical total column ozone are projected to be small. By the middle of the 21st century, the model projections suggest surface UV to be slightly higher than in the 1960s, very close to values in 1980, and slightly lower than in 2000. The projected decrease in tropical total column ozone through the latter half of the century will likely result in clear-sky surface UV remaining above 1960 levels. Average UV irradiance is already high in the tropics due to naturally occurring low total ozone columns and high solar elevations. The magnitude of UV changes in the polar regions is larger than elsewhere because ozone changes in polar regions are larger. For the next decades, surface clear-sky UV irradiance, particularly in the Antarctic, will continue to be higher than in 1980. Future increases in ozone and decreases in clear-sky UV will occur at slower rates than those associated with the ozone decreases and UV increases that occurred before 2000. In Antarctica, surface clear-sky UV is projected to return to 1980 levels between 2040 and 2060, while in the Arctic this is projected to occur between 2020 and 2030. By 2100, October surface clear-sky erythemal irradiance in Antarctica is likely to be between 5% below to 25% above 1960 levels, with considerable uncertainty. This is consistent with multi-model-mean October Antarctic total column ozone not returning to 1960 levels by 2100. In contrast, by 2100, surface clear-sky UV in the Arctic is projected to be 010% below 1960 levels.
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The DAPPLE (Dispersion of Air Pollutants and their Penetration into the Local Environment) project seeks to characterise near-field urban atmospheric dispersion using a multidisciplinary approach. In this paper we report on the first tracer dispersion experiment carried out in May 2003. Results of concurrent meteorological measurements are presented. Variations of receptor tracer concentration with time are presented. Meteorological observations suggest that in-street channelling and flow-switching at intersections take place. A comparison between roof top and surface measurements suggest that rapid vertical mixing occurs, and a comparison between a simple dispersion model and maximum concentrations observed are presented
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This paper reports the results of a parametric CFD study on idealized city models to investigate the potential of slope flow in ventilating a city located in a mountainous region when the background synoptic wind is absent. Examples of such a city include Tokyo in Japan, Los Angeles and Phoenix in the US, and Hong Kong. Two types of buoyancy-driven flow are considered, i.e., slope flow from the mountain slope (katabatic wind at night and anabatic wind in the daytime), and wall flow due to heated/cooled urban surfaces. The combined buoyancy-driven flow system can serve the purpose of dispersing the accumulated urban air pollutants when the background wind is weak or absent. The microscopic picture of ventilation performance within the urban structures was evaluated in terms of air change rate (ACH) and age of air. The simulation results reveal that the slope flow plays an important role in ventilating the urban area, especially in calm conditions. Katabatic flow at night is conducive to mitigating the nocturnal urban heat island. In the present parametric study, the mountain slope angle and mountain height are assumed to be constant, and the changing variables are heating/cooling intensity and building height. For a typical mountain of 500 m inclined at an angle of 20 to the horizontal level, the interactive structure is very much dependent on the ratio of heating/cooling intensity as well as building height. When the building is lower than 60 m, the slope wind dominates. When the building is as high as 100 m, the contribution from the urban wall flow cannot be ignored. It is found that katabatic wind can be very beneficial to the thermal environment as well as air quality at the pedestrian level. The air change rate for the pedestrian volume can be as high as 300 ACH.
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NDIR is proposed for monitoring of air pollutants emitted by ship engines. Careful optical filtering overcomes the challenge of optical detection of NO2 in humid exhaust gas, despite spectroscopic overlap with the water vapour band.
