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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Analýza časoprostorové variability koncentrací ozonu v Jizerských horách / Temporal and spatial analysis of ozone in the Jizerske hory Mts.

Stoklasová, Petra January 2012 (has links)
The aim of this thesis is to analyze and evaluate temporal and spatial patterns of concentrations of ambient ozone in the CHKO Jizerské hory. The Jizerské hory Mts. are an area where one of the highest concentrations of ambient ozone are measured every year and, therefore, our attention was focused on this area. The measurements were carried out between 2006 and 2010 at 13 sites (714-1000 m n. m.) in the CHKO Jizerské hory. From the input data, which were fortnightly average nitrate concentrations created on the filters of Ogawa passive samplers, fortnightly average concentrations of ambient ozone were computed using the empirical flow. Ambient ozone concentrations ranged from 13,8 ppb (year 2007) to 72,1 ppb (year 2006). From the five-year period under study defy the year 2006, when the highest concentrations of ambient ozone were measured. The lowest concentrations occurred in 2009. In all years, the concentrations of ambient ozone increased with increasing elevation and this gradient ranged from 2,7 to 4,6 ppb on 100 meters altitude. The accuracy and precision of measurement was very good (accuracy: R2 = 82 %; precision: R2 = 98 %). By multiple linear regression it was found, that ambient ozone concentration are influenced, in addition to the altitude, by ozone concentrations from previous...
2

Trends in Ozone Concentration and Its Relationship with Meteorological Parameters in Kao-Ping Area, Taiwan

Ni, Kuo-Tun 29 June 2004 (has links)
PM10 (suspended particles with diameter below 10 £gm) and O3 (ozone) are the dominant air pollutants in Kao-Ping airshed, in which ozone is a secondary pollutant produced from its precursors of NOx (= NO + NO2) and HC (hydrocarbons) via complex photochemical reactions in sunlight. This study first statistically summarized the trends of ozone concentrations using box plots over recent five to six years from four and three air-quality monitoring stations in Kaohsiung City and Ping-Tung County, respectively. Then, the long-term variations of ozone concentrations were analyzed using trend formula proposed by Holland et al. (1999). Finally, multi-variable factor analysis was applied to study the relationships among the ozone concentrations with other air pollutants and meteorological parameters. Results reveal that the highest peak of ozone concentration appears in October and the second peak appears in March, while the lowest one appears in summer. Except being moderate relationships in Tzyo-Yin station, trend results show strong relationships in all other stations. Results also show that the percentage annual increase in ozone concentration in Kaohsiung City is higher than those in Kaohsiung and Ping-Tung Counties. The factor analyses reveal that the concentration of ozone is positively correlated with air temperature, wind speed and period of sunshine, while negatively correlated with concentrations of NO2, CO, NO, and NOx in the seasons of spring, autumn and winter; but negatively correlated with relative humidity in autumn. Notably, the percentage increases of ozone events in recent years should be also related to the rises of air temperature and period of sunshine, which should be watched continuously.
3

Ambient Ozone and Cadmium as Risk Factors For Congenital Diaphragmatic Hernia

Ramakrishnan, Rema 16 November 2017 (has links)
Congenital diaphragmatic hernia (CDH) results from a defect in the diaphragm through which abdominal contents enter the thorax displacing the heart and the lungs. This causes lung hypoplasia and varying degrees of pulmonary hypertension resulting in high rates of morbidity and mortality. Though CDH has a prevalence rate of 2.61 per 10,000 live births it is an expensive birth defect with an estimated annual cost of nearly $250 million for all CDH survivors. Maternal exposure to air pollutants have not been studied as risk factors for CDH in humans. Ambient ozone has been found to be risk factors for certain birth defects including congenital heart defects, chromosomal anomalies, and limb reduction defects. Cadmium, however, has been found to be a risk factor for diaphragmatic hernia, cleft palate, renal defects, anopthalmia, microphthalmia, anal atresia, undescended testes, and dysplastic ears in animal studies only. The objectives of this study were to: 1) examine the prevalence, temporal trends, and correlates of CDH among live-born infants during 1998–2012; 2) investigate the association between sociodemographic and perinatal characteristics and neonatal and one-year survival among infants with CDH and its subtypes, isolated and complex; 3) examine the role of ambient ozone as a risk factor for CDH; and 4) determine the association between maternal exposure to ambient cadmium in air and CDH and assess if maternal smoking during pregnancy is an effect modifier of the cadmium-CDH association. To answer these questions we used a population-based, retrospective cohort study using data from the 1998–2012 Florida Birth Defects Registry. We classified CDH cases into isolated and complex. A case that was associated with other anomalies listed on the National Birth Defects Prevention Network list of major structural reportable defects was classified as complex CDH. We used Poisson and joinpoint regression models to compute prevalence ratios and assess temporal trends, respectively. Kaplan-Meier survival curves and Cox proportional hazards regression were used to describe neonatal and one-year survival and estimate hazard ratios of neonatal and one-year mortality. We then used multilevel Poisson regression models to examine the association between maternal exposure to ambient ozone and CDH as well as cadmium and CDH. We conducted stratified analyses to test for effect measure modification by maternal smoking status. The study population to answer the first two questions consisted of 3,209,775 live-born infants (including 1,025 cases). To answer the third and fourth questions, the study population consisted of 3,039,685 and 2,591,395 live-born infants (including 981 and 840 cases), respectively. We found a 4% increase in the annual prevalence of CDH among complex cases, but no trend for isolated cases. We observed higher prevalence of CDH among infants born to mothers with high school or less maternal education and for multiple births. Female sex and maternal obesity were found to be associated with decreased risk for CDH. The most important predictor of neonatal and one-year mortality was gestational age
4

Výpočet expozičního indexu AOT40 z výsledků měření koncentrací přízemního ozonu pasivními dosimetry / Estimation of exposure index for surface ozone AOT40 from diffusive sampler measurements

Pavlíková, Monika January 2010 (has links)
The study summerizes methods of ozone AOT40 index estimation from time intergarated passive sampler measurements in forests. Ground-level ozone is a highly phytotoxic atmospheric pollutant. In recent years negative impacts of elevated concentrations of ground-level ozone on vegetation and ecosystems have been studied and atmospheric levels of ozone have been measured. There is a noticeable negative impact of elevated concentrations of ground-level ozone on forests in the Czech Republic, mainly in rural areas that are far away from the emission sources. The AOT40F exposure index is a tool to assess the geographical areas with vegetation potentially at risk due to elevated ground-level ozone concentrations. The AOT40 index is the accumulated hourly exposure during daytime hours above cut-off concentration of 40 ppb, during the growing season. Passive samplers are used for measuring ground-level ozone in high spatial resolution. Passive samplers are easy to use. However this metod provides time intergrated values of pollutant concentrations (1-2 weeks). It is not possible to estimate AOT40 index by using just data of mean ozone concentrations over the sampling period. Three methods were used to estimate the exposure index AOT40F for forests by mean ozone concentrations measured in the Jizerské Hory...
5

Meteorologically adjusted trends of ozone and dispersion of air pollutants in the Hsuehshan Tunnel

Li, Han-chieh 22 June 2010 (has links)
This study separated two parts: PART ¢¹ Meteorologically adjusted trends of ozone Since meteorological changes strongly affect ambient ozone concentrations, trends in concentrations of ozone upon the adjustment of meteorological variations are important of evaluating emission reduction efforts. This work is to study meteorological effects on the long-term trends of ozone concentration using a multi-variable additive model in Kaohsiung. The long-term trends of ozone concentration were analyzed using the Holland model (without meteorological-adjusted) and the robust MM Regression model (with meteorological-adjusted) based on the data of eight EPA air quality stations from 1997 to 2006 in Kaohsiung area. According to the result of the simulation, the simulated value of the robust MM-Regression model present more valid than the Holland model.The simulated results show that the long-term ozone concentration increases at 13.84% (or 13.06%) monthly (or annually) after meteorological adjustments, less than at 26.10% (or 23.80%) without meteorological adjustments in Kaohsiung county. The simulated results show that the long-term ozone concentration increases at 9.01% (or 6.88%) monthly (or annually) after meteorological adjustments, less than at 22.01% (or 19.67%) without meteorological adjustments in Kaohsiung city. Wind speed, duration of sunshine and pressure are the three dominant factors that influence the ground-level ozone levels in Kaohsiung area. PART ¢º Dispersion of air pollutants in the Hsuehshan Tunnel Concentrations of carbon monoxide (CO) and nitrogen oxides (NOx) were measured from November 14 ¡V 17 2008 in a cross-mountain Hsuehshan traffic tunnel stretching 12.9 km and containing eastward and westward channels. Air pollutants of CO (carbon monoxide) and NOx (nitrogen oxides) will be monitored at the inlet, outlet and vertical shafts of the tunnel. Meanwhile, numerical simulation of three-dimensional turbulent flow will be performed using STAR-CD software. Traffic and pollutant concentrations during the weekends exceeded those during the weekdays. Measured concentrations of CO at the two tunnel outlets (14.5 ¡V 22.8 ppm) were approximately three times higher than those at the two tunnel inlets (3.2 ¡V 7.3 ppm), while concentrations of NOx at the two tunnel outlets (1.9 ¡V 2.9 ppm) were approximately four to five times higher than those at the two tunnel inlets (0.3 ¡V 0.8 ppm). The outlet of vertical draft 2 had the highest pollutant concentrations (CO = 12.3 ppm; NOx = 1.9 ppm), followed by vertical drafts 1 and 3. Three-dimensional turbulence modeling results indicate that airflow in the tunnel was primarily driven by the combined effects of axial fans and vehicles. Results of this study demonstrate that simulated pollutant concentrations increase downstream and are vertically stratified, due to tailpipe exhausts close to tunnel floor. Simulations agreed fairly well with measurements.

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