Dissertationen: „Atmospheric Chemistry|Environmental Sciences“

1

Green, Sarah A. „Applications of fluorescence spectroscopy to environmental chemistry“. Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13167.

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2

Davidson, Nicholas Mark. „Atmospheric processing of aerosols“. Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8298/.

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The chemistry of aerosol particles is critical to the influence said particles have over human health, air quality and the distribution of nutrients across the world. Current models estimate that windborne dust represents the movement of thousands of teragrams of solid material of varying composition and solubility across continents and into the world’s oceans. Understanding the composition and surface reactivity of anthropogenic particles from industry, agriculture and vehicle emissions is vital to understanding their potential impact on the world, and the structure and behaviour of inhalable pharmaceuticals is a strong determinant of their efficacy. The following work examines a broad selection of natural and anthropogenic particulate samples with synchrotron-based techniques, including analysis of ship emissions collected directly from stacks for the first time. The effect of simulated atmospheric acid processing on the solubility of iron on coal fly ash is evaluated, and optical trapping is used in conjunction with analytical techniques to observe the influence of relative humidity on the properties of pharmaceutical aerosols and aqueous droplets containing fluorescent protein solutions.

3

Malamakal, Tom M. „Characterizing Emissions from Prescribed Fires and Assessing Impacts to Air Quality in the Lake Tahoe Basin Using Dispersion Modeling“. Thesis, University of Nevada, Reno, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1540197.

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A PM_2.5 monitoring network was established around Lake Tahoe during fall 2011, which, in conjunction with measurements at prescribed burns and smoke dispersion modeling based on the Fire Emission Production Simulator and the Hybrid Single Particle Lagrangian Integrated Trajectory (FEPS-HYSPLIT) Model, served to evaluate the prescribed burning impacts on air quality. Emissions from pile and understory prescribed burns were characterized using a mobile air monitoring system. In field PM_2.5 emission factors showed ranges consistent with laboratory combustion of wet and dry fuels. Measurements in the smoke plume showed progression from flaming to smoldering phase consistent with FEPS and PM_2.5 emission factors generally increased with decreasing combustion efficiency. Model predicted smoke contributions are consistent with elevated ambient PM_2.5 concentrations in three case studies, and high meteorological model resolution (2km × 2 km) seems to produce accurate smoke arriving times. In other cases, the model performance is difficult to evaluate due to low predicted smoke contributions relative to the typical ambient PM_2.5 level. Synergistic assessment of modeling and measurement can be used to determine basin air quality impact. The findings from this study will help land management agencies better understand the implications of managing fire at the wildland-urban interface.

4

Hall, Tavenner Marie. „Evaluating changes in strontium chemistry of stream water in response to environmental stress“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/54408.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.
Includes bibliographical references (leaves 47-49).
by Tavenner Marie Hall.
M.S.

5

Raff, Jonathan Daniel. „Transport of organic pollutants and their atmospheric fates“. [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3292440.

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Thesis (Ph. D.)--Indiana University, School of Public and Environmental Affairs, 2007.
Title from dissertation home page (viewed May 28, 2008). Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7189. Adviser: Ronald A. Hites.

6

Diao, Minghui. „Ice supersaturation and cirrus cloud formation from global in-situ observations“. Thesis, Princeton University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3597474.

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Water vapor, clouds and aerosols are three major components in the atmosphere that largely influence the Earth's climate and weather systems. However, there is still a lack of understanding on the distribution and interaction of these components. Large uncertainties still remain in estimating the magnitude and direction of the aerosol indirect effect on cloud radiative forcing, which potentially can either double or cancel out all anthropogenic greenhouse gas effect. In particular, a small variation in water vapor mixing ratio and cloud distribution in the upper troposphere and lower stratosphere (UT/LS) can generate large impacts on the Earth's surface temperature. Yet the understanding of water vapor and clouds in the UT/LS is still limited due to difficulties in observations. To improve our understanding of these components, observations are needed from the microscale (~100 m) to the global scale. The first part of my PhD work is to provide quality-controlled, high resolution (~200 m), in situ water vapor observations using an open-path, aircraft-based laser hygrometer. The laboratory calibrations of the laser hygrometer were conducted using complementary experimental systems. The second part is to compare the NASA AIRS/AMSU-A water vapor and temperature retrievals with aircraft-based observations from the surface to the UT/LS at 87°N-67°S in order to understand the accuracy and uncertainties in remote sensing measurements. The third part of my research analyzes the spatial characteristics and formation condition of ice supersaturation (ISS), the birthplace of cirrus clouds, and shows that water vapor horizontal heterogeneities play a key role in determining the spatial distribution of ISS. The fourth part is to understand the formation and evolution of ice crystal regions (ICRs) in a quasi-Lagrangian view. Finally, to help estimate the hemispheric differences in ice nucleation, the ISS distribution and ICR evolution are compared between the two hemispheres. Overall, these analyses provided a microphysical scale yet global perspective of the formation of ISS and cirrus clouds. Ultimately, these efforts will help to improve the understanding of human activities' influences on clouds, water vapor and relative humidity in the UT/LS and provide more accurate representations of these components in future climate prediction.

7

Tamada, Mayumi. „Kinetics of free-radical reactions with monoterpenes in the aqueous phase mimicing atmospheric aerosol chemistry“. California State University, Long Beach, 2013.

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8

Gallo, Lino J. „Atmospheric input of polycyclic aromatic hydrocarbons to the sea surface microlayer“. W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539616655.

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Atmospheric input of polycyclic aromatic hydrocarbons (PAH) to water was studied and the effects of sea surface microlayer (SSM) determined. The York River system and the Perrin River areas were monitored with a drum skimmer and a high volume air sampler. Experiments were conducted in the laboratory under controlled conditions. The SSM extracted vapor phase PAH of low molecular weight from the air, and there, aromatic compounds went from dissolved into particulate phase very rapidly. Water covered with a natural SSM received much less atmospheric input of PAH than water without SSM in a given period of time. Henry's law constant did not apply when SSM was present. The high uptake capacity of this type of film makes it impossible to approach equilibrium conditions in the marine atmospheric environment.

9

Orndorff, William. „Development of an Atmospheric Fluidized Bed Combustor (AFBC)“. TopSCHOLAR®, 1997. http://digitalcommons.wku.edu/theses/349.

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The relatively recent interest in the U.S. in the development of atmospheric fluidized bed combustion (AFBC) has been preceded by two main factors. First of these is the ever present problem of acid rain and growing public support for cleaner burning fossil fuels. Second is the increasing demand on public landfills and subsequent need for burning of municipal solid waste. From these factors and their corresponding influences, Western Kentucky University has the impetus and has received the financial assistance necessary to build and develop a laboratory scale AFBC system. A brief history of the events leading to this development, as well as selected results from the last 12 months of this project are discussed.

10

Liljegren, Jennifer A. „Experimental and theoretical studies of the kinetics of the hydroxyl radical (OH)-initiated oxidation of volatile organic compounds“. Thesis, Indiana University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3602969.

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This research investigates the kinetics of the hydroxyl radical (OH)-initiated oxidation of several volatile organic compounds (VOCs) including ethanol, 3-methylfuran, and methyl ethyl ketone (2-butanone). Oxidation by OH is the dominant loss process for many biogenic and anthropogenic VOCs, making ambient concentrations of OH and the rate constants of OH + VOC reactions useful for determining the lifetime of various VOCs in the atmosphere. The rate constants of OH + VOC reactions are important for improving the accuracy of input parameters used in urban and regional air quality models which can be used to inform the development of air quality control strategies. The absolute rate constants for the reaction of OH with ethanol, 3- methylfuran, and methyl ethyl ketone (2-butanone) and, in some cases, their deuterated isotopomers have been measured as a function of pressure and temperature using discharge-flow techniques coupled with laser-induced fluorescence detection of OH. Theoretical studies of the potential energy surface for the various pathways in the OH + ethanol and OH + methyl ethyl ketone (2-butanone) reactions indicate a mechanism involving hydrogen-abstraction through a hydrogen-bonded pre-reactive complex. The experimental measurements of the rate constants and the kinetic isotope effect have been used in conjunction with the results of the theoretical studies to improve our understanding of the kinetics of these reactions.

11

Gustafson, Kurt E. „Molecular Diffusion Coefficients for Polycyclic Aromatic Hydrocarbons in Air and Water“. W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617664.

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12

Revenaz, Bertrand. „Impact of the ozonolysis of alkenes on the aqueous oxidation of sulfur : a modeling study“. Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33024.

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Atmospheric sulfate has impacts ranging from health concerns to climate change. Traditional photolytic oxidant production channels are not sufficient to account for the observed atmospheric sulfate load. It has been suggested that sulfur oxidation is oxidant dependent, especially in urban areas and during the wintertime. The ozonolysis of alkenes, a dark reaction, could potentially produce additional oxidants (HO• and H₂O₂). This study used MOCCA (Model of Chemistry Considering Aerosols), a zeroth dimension chemical box model to study the potential impact of the ozonolysis of alkenes on the aqueous phase chemistry of sulfur. The study was conducted at mid-latitudes using both winter and summer, urban and remote settings. It was found that during the winter time, the ozonolysis of alkenes can enhance the aqueous oxidation of sulfur by approximately a factor of 20. The impact of ozonolysis was found to be independent of direct HO• yield but linearly dependent with H₂O₂ yield. While preliminary, results suggest that the impact of the ozonolysis of alkenes can still be felt 4 days after an air parcel has left the polluted urban environment with elevated acidity and aqueous S(VI) levels. During the summer runs, the lack of a growth mechanism in the aerosol component of the model lead to an overestimation of the aerosol acidity. While this led to an underestimation of the impact of ozonolysis, we still calculated a approximately 7 fold increase in the aqueous sulfur oxidation rate.

13

Viswanathan, Balakrishnan. „Theoretical investigation of mercury reactions with halogen species in the Arctic troposphere“. Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33038.

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Mercury is one of the most toxic elements present in the geosphere, present in many chemical and physical forms. Nearly uniform mixing ratios are observed within a hemisphere, the concentration being higher in the northern than in the Southern Hemisphere. Lack of kinetic data regarding mercury reactions prevents an explanation of the behaviour and deposition pathways of mercury from the atmosphere. Theoretical calculations have been carried out using DFT theory to investigate the thermodynamics and kinetics of the reactions of Hg0 with Cl, Br, ClO, and BrO radicals and with Cl 2 and Br2. The results from these calculations were used to evaluate the kinetic rate constants at 298.15 K and 238.15 K for the reactions involving gaseous mercury. In this paper, the results of this study are presented and relevance to the chemistry of the Arctic is discussed.

14

Omidvarborna, Hamid. „Combustion Chemistry of Biodiesel for the Use in Urban Transport Buses: Experiment and Modeling“. University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1464863574.

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15

Wecht, Kevin James. „Quantifying Methane Emissions Using Satellite Observations“. Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11252.

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Methane is the second most influential anthropogenic greenhouse gas. There are large uncertainties in the magnitudes and trends of methane emissions from different source types and source regions. Satellite observations of methane offer dense spatial coverage unachievable by suborbital observations. This thesis evaluates the capabilities of using satellite observations of atmospheric methane to provide high-resolution constraints on continental scale methane emissions. In doing so, I seek to evaluate the supporting role of suborbital observations, to inform the emission inventories on which policy decisions are based, and to enable inverse modeling of the next generation of satellite observations.
Earth and Planetary Sciences

16

Sargent, Maryann Racine. „The Response of Stratospheric Water Vapor to a Changing Climate: Insights from In Situ Water Vapor Measurements“. Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10623.

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Stratospheric water vapor plays an important role in the Earth system, both through its role in stratospheric ozone destruction and as a greenhouse gas contributing to radiative forcing of the climate. Highly accurate water vapor measurements are critical to understanding how stratospheric water vapor concentrations will respond to a changing climate. However, the past disagreement among water vapor instruments on the order of 1 – 2 ppmv hinders understanding of the mechanisms which control stratospheric humidity, and the reliable detection of water vapor trends. In response to these issues, we present a new dual axis water vapor instrument that combines the heritage Harvard Lyman-$\alpha$ hygrometer with the newly developed Harvard Herriott Hygrometer (HHH). The Lyman-$\alpha$ instrument utilizes ultraviolet photo-fragment fluorescence detection, and its accuracy has been demonstrated though rigorous laboratory calibrations and in situ diagnostic procedures. HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell; it demonstrated in-flight precision of 0.1 ppmv (1-sec) with accuracy of 5%±0.5 ppmv. We describe these two measurement techniques in detail along with our methodology for calibration and details of the measurement uncertainties. We also examine the recent flight comparison of the two instruments with several other in situ hygrometers during the 2011 MACPEX campaign, in which five independent instruments agreed to within 0.7 ppmv, a significant improvement over past comparisons. Water vapor measurements in combination with simultaneous in situ measurements of $O_3$, CO, $CO_2$, HDO, and HCl are also used to investigate transport in the Tropical Tropopause Layer (TTL). Data from the winter 2006 CR-AVE campaign and the summer 2007 TC4 campaign are analyzed in a one-dimensional mixing model to explore the seasonal importance of transport within the TTL via slow upward ascent, convective injection, and isentropic transport from the midlatitude stratosphere. The model shows transport from midlatitudes to be significant in summer and winter, affecting ozone concentrations and therefore the radiative balance of the TTL. It also shows significant convective influence up to 420 K potential temperature in both seasons, which appreciably increases the amount of water vapor above the tropopause.
Engineering and Applied Sciences

17

Tai, Pui Kuen Amos P. K. „Impact of Climate Change on Fine Particulate Matter $(PM_{2.5})$ Air Quality“. Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10576.

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This dissertation investigates the impact of 2000-2050 climate change on fine particulate matter $(PM_{2.5})$ air quality. We first applied a multiple linear regression model to study the correlations of total $PM_{2.5}$ and its components with meteorological variables using the past decadal $PM_{2.5}$ observations over the contiguous US. We find that daily variation in meteorology can explain up to 50% of $PM_{2.5}$ variability. Temperature is positively correlated with sulfate and organic carbon (OC) almost everywhere. The correlation of nitrate with temperature is negative in the Southeast but positive in California and the Great Plains. Relative humidity (RH) is positively correlated with sulfate and nitrate, but negatively with OC. Precipitation is strongly negatively correlated with all $PM_{2.5}$ components. We then compared the observed correlations of $PM_{2.5}$ with meteorological variables with results from the GEOS-Chem chemical transport model. The results indicate that most of the correlations of $PM_{2.5}$ with temperature and RH do not arise from direct dependence but from covariation with synoptic transport. We applied principal component analysis and regression to identify the dominant meteorological modes controlling $PM_{2.5}$ variability, and showed that 20-40% of the observed $PM_{2.5}$ daily variability can be explained by a single dominant meteorological mode: cold frontal passages in the eastern US and maritime inflow in the West. From 1999-2010 observations we further showed that interannual variability of annual mean $PM_{2.5}$ in most of the US is strongly correlated with the synoptic period T of the dominant meteorological mode as diagnosed from a spectral-autoregressive analysis. We then used the observed local $PM_{2.5}$-to-period sensitivity to project $PM_{2.5}$ changes from the 2000-2050 changes in T simulated by fifteen IPCC AR4 GCMs following the SRES A1B scenario. We project a likely increase of $\sim 0.1 \mu g m^{-3}$ in annual mean $PM_{2.5}$ in the eastern US arising from less frequent frontal ventilation, and a likely decrease of $\sim 0.3 \mu g m^{-3}$ in the northwestern US due to more frequent maritime inflows. These circulation-driven changes are relatively small, representing only a minor climate penalty or benefit for $PM_{2.5}$ regulatory purpose.
Engineering and Applied Sciences

18

Thomason, Krista A. „Trends Analysis and a Yearly Comparison of Point Sources of Atmospheric Mercury Using HYSPLIT Back Trajectories Focused in Athens, Ohio“. Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1557161272706908.

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19

Shandilya, Kaushik K. „Characterization, Speciation, and Source Apportionment of Particles inside and from the Exhaust of Public Transit Buses Fueled With Alternative Fuels“. University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1341594452.

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20

Dotse, Charles Kafui. „Assessing Commercial Organic and Conventionally Grown Vegetables by Monitoring Selected Heavy Metals Found in Them“. Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etd/1715.

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Commercially available organic and conventionally grown vegetables were studied by quantitative determination of selected metals in them and to determine if any differences found are statistically significant. These findings can help the consumers to determine if the vegetable products are within the recommended maximum limits as proposed by the joint FAO/WHO Expert committee on organic foods designation. Eight edible vegetables were purchased from local stores in both the organic and conventionally grown categories. Samples were digested with concentrated nitric acid and the metals monitored were zinc, copper, lead, iron, cadmium, and nickel using flame atomic absorption. The concentration range for the heavy metals found are as follows: Zn, 2.04-69.4; Cu, 0.35-15.1; Pb, 0.00-3.99; Cd, 0.00-0.74; Fe, 2.52-319; and Ni, 39.9-53.8 μg/g. It was found that in general, conventional vegetables contain higher amounts of most of the heavy metals studied as compared to their organic counterparts. The study also showed that all vegetables products contain below the permissible limits for Zn, Cu, Ni, and Fe. For Pb all vegetables exceeded the safe limit except organic cucumber and conventional cabbage. For Cd, organic lettuce and green pepper, and conventional leafy green, green pepper, and spinach all exceeded the limit recommended by FAO/WHO.

21

Bain, Emily C. „Clean Air in South Texas: An Estimation of Biogenic Tropospheric Ozone Precursors Using Various Models“. Ohio : Ohio University, 2002. http://www.ohiolink.edu/etd/view.cgi?ohiou1033659160.

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22

Black, Julia. „Quantifying Carbonyl Sulfide and Other Sulfur-Containing Compounds Over the Santa Barbara Channel“. Scholarship @ Claremont, 2017. http://scholarship.claremont.edu/scripps_theses/998.

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Carbonyl sulfide (OCS) is emitted to the atmosphere through the outgassing of ocean surface waters. OCS is also the primary source of sulfur-containing compounds in the stratosphere and contributes to the formation of the stratospheric sulfate layer, an essential controller of the radiative balance of the atmosphere. During the 2016 Student Airborne Research Program (SARP), 15 whole air samples were collected on the NASA DC-8 aircraft over the Santa Barbara Channel. Five additional surface samples were taken at various locations along the Santa Barbara Channel. The samples were analyzed using gas chromatography in the Rowland-Blake lab at UC Irvine, and compounds associated with ocean emissions including OCS, dimethyl sulfide (DMS), carbon disulfide (CS2), bromoform (CHBr3), and methyl iodide (CH3I) were examined. Excluding OCS, the vertical distribution of marine tracers that were analyzed showed dilution with increasing altitude. For OCS, the surface samples all exhibited elevated concentrations of OCS in comparison to samples taken from the aircraft, with an average of 666 ± 26 pptv, whereas the average concentration of OCS in the aircraft samples was 581 ± 9 pptv. 2016 Surface samples were compared to surface samples from SARP campaigns between 2009-2015 taken near or within the 2016 study region. The 2009-2015 samples exhibited an average OCS concentration of 526 ± 8 pptv. It is evident that the 2016 surface samples measured higher concentrations of OCS than ever recorded during previous SARP campaigns and in comparison to global averages: 525 ± 17 pptv in the Northern hemisphere and 482 ± 13 pptv in the Southern hemisphere (Sturges et al., 2001). OCS emissions should be measured using surface samples if emission estimates from the ocean are to be evaluated since measurements from the aircraft (500 ft) are not sufficiently capturing surface concentrations. Additionally, OCS enhancements seen in 2016 had never before been detected by surface samples, revealing a potential phenomenon at work causing the elevation during this year’s campaign.

23

Marks, Marguerite Colasurdo. „Incorporating Chemical Activity and Relative Humidity Effects in Regional Air Quality Modeling of Organic Aerosol Formation“. PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1511.

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Atmospheric particulate matter is known to have significant effects on human health, visibility, and global climate. The magnitudes of these effects, however, depend in complex ways on chemical composition, relative humidity, temperature, phase state, and other parameters. Current regional air quality models such as CMAQ (Community Multiscale Air Quality model) ignore many of these considerations, and consider that the formation of secondary organic aerosol (SOA) can be calculated by assuming thermodynamic ideality in the organic particulate matter (OPM) phase as well as negligible uptake of water into the OPM phase. Theoretical predictions and model simulations considering non-ideality and water uptake show that the standard model assumptions can lead to large errors in predicted SOA mass, and that the magnitude of these errors is sensitive to the composition of the OPM phase. The SOA module in CMAQ v4.7.1 has been revised in this work to allow consideration of the effects of both non-ideality and water uptake. First, a reasonable specific surrogate structure was assigned to each of the lumped products assumed to be produced by reaction of the different precursor hydrocarbons considered in CMAQ (e.g., isoprene, benzene, and toluene). Second, the CMAQ code was modified to allow iterative calculation (at each point in space and time) of the gas/particle partitioning coefficient for each of the SOA-forming products and for water. Third, model simulations were performed for the Eastern US at a resolution of 36-km x 36-km for late summer 2006, under a range of relative humidity conditions. When compared with an appropriate base case, the modified code produced increases in SOA ranging from 0.17 to 0.51 micrograms per cubic meter. The average change was 0.30 micrograms per cubic meter, corresponding to a 37% increase in SOA formation. Incorporation of phase separation effects would likely lead to further increases in predicted SOA levels.

24

Cilwa, Katherine E. „Surface Plasmons Polaritons and Single Dust Particles“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1304532704.

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25

Smith, Erin. „Heavy Metal Accumulation in Seagrasses in Southeastern Florida“. Thesis, NSUWorks, 2018. https://nsuworks.nova.edu/occ_stuetd/474.

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Seagrass beds are among the most ecologically important systems in the marine environment. They provide the primary production to nearby coral reef and mangrove communities, and seagrasses comprise a large component of the diets of many marine organisms including fishes, small invertebrate species, and many protected species such as manatees and sea turtles. This consumption provides a pathway for many contaminants to enter the marine food web via the seagrasses. The coastal location of seagrass beds causes them to be especially susceptible to anthropogenic pollution, including accumulation of heavy metals, which has been shown to have many adverse health effects in the seagrasses and marine organisms that feed on them. This study assessed the heavy metal concentrations of seagrasses in three regional locations in South Florida: Port of Miami, Card Sound Aquatic Preserve, and Florida Bay. Three species of seagrasses, Thalassia testudinum, Halodule wrightii, and Syringodium filiforme, which comprise the majority of South Florida seagrass beds, were collected monthly for a period of one year and analyzed for ten heavy metals: (arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), selenium (Se), zinc (Zn)). Concentrations were compared across locations, season, species, and plant part (leaves, shoots, roots, and rhizomes). Concentration ranges, in µg/g (ppm), found in seagrass tissues for all included locations, species, and plant parts were: As (0.02-2.95), Cd (0.09-10.72), Cu (0.38-33.68), Fe (1.52-1877.43), Pb (0.78-156.20), Mn (0.79-300.15), Hg (0.03-16.46), Ni (0.67-87.74), Se (0.01-4.79), Zn (1.48-669.44). Statistical analysis showed significant difference in concentrations among locations, season, species, and plant morphology.

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Ventura, Robert E. „Wetlands and Greenhouse Gas Fluxes: Causes and Effects of Climate Change – A Meta-Analysis“. Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/pomona_theses/107.

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Climate change is one of the largest problems facing this generation. Anthropogenically caused increases of greenhouse gas emissions is a significant culprit to this problem. Although the obvious problems such as cars, industry, and urbanism garnish a significant amount of the criticism, natural sources such as wetlands are also beginning to contribute to this issue. This is becoming increasingly significant as wetlands shift from being sinks of greenhouse gases to becoming sources as various anthropogenic impacts, including global warming itself, begin to affect the health of the wetlands. The aim of this project is to look at four common types of wetlands, being tropical mangroves, temperate coastal marshes, inland meadows, and subarctic peatlands, all located in different climactic areas of the world, and by doing a meta-analysis of available data of greenhouse gas production for each wetland type, observe how differences in their greenhouse gas production may contribute or be affected by climate change and global warming. Results of the meta-analysis revealed that the most significant production of the potent greenhouse gas nitrous oxide occurs in coastal wetlands such as tropical mangroves and coastal marshes, while the greenhouse gas methane is seen to be produced most in subarctic peatlands. These contributions of wetlands to global greenhouse gas production are not as significant as other anthropogenic contributions. However, subarctic wetlands contribute to more than half of the global methane emissions, and the most important aspect of wetland greenhouse gas production is that they are producing more greenhouse gases than they would normally be sequestering, contributing more than the basic greenhouse gas production data can display. Global climate changes such as temperature increase and sea level rise could also make these levels of greenhouse gas production become worse, although measures to decrease the effects of this such as regulations on anthropogenic nitrogen input, macrophyte presence, and prevention of peat burning.

27

Netzloff, Heather Marie. „Drama in Dynamics Boom, Splash, and Speed“. Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835377-gqvCD8/webviewable/.

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19 Dec 2004.
Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1930" Heather Marie Netzloff. 12/19/2004. Report is also available in paper and microfiche from NTIS.

28

Bright, Vivien Bianca. „Street canyon atmospheric composition : coupling dynamics and chemistry“. Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4414/.

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A new model for the simulation of street canyon atmospheric chemical processing has been developed, by integrating an existing Large-Eddy Simulation (LES) dynamical model of canyon atmospheric motion with a detailed chemical reaction mechanism, the Reduced Chemical Scheme (RCS), comprising 51 chemical species and 136 reactions, based upon a subset of the Master Chemical Mechanism (MCM). The combined LES-RCS model is used to investigate both the effects of mixing and chemical processing upon air quality within an idealised street canyon. The effect of the combination of dynamical (segregation) and chemical effects is determined by comparing the outputs of the full LES-RCS canyon model with those obtained when representing the canyon as a zero-dimensional box model (i.e. assuming mixing is complete and instantaneous). The LES-RCS approach predicts lower (canyon-averaged) levels of NOX, OH and HO2, but higher levels of O3, compared with the box model run under identical chemical and emission conditions. Chemical processing of emissions within the canyon leads to a significant increase in the Ox flux from the canyon into the overlying boundary layer, relative to primary emissions, for the idealised case and a number of pollution scenarios considered. These results demonstrate that within-canyon atmospheric chemical processing can substantially alter the concentrations of pollutants injected into the urban canopy layer, compared with the raw emission rates within the street canyon and that such variations have a considerable effect on average within canyon concentrations and the flux of pollutants out of the canyon into the urban background environment.

29

Scherr, Frank. „Sorption, degradation and transport of estrogens and estrogen sulphates in agricultural soils“. Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1017.

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The fate and behaviour of estrogens in the environment are of concern due to the compounds’ endocrine disruption potential. Estrogens, namely 17β-estradiol (E2), estrone (E1), and estrogen sulphates, i.e. 17β-estradiol-3-sulphate (E2-3S) and estrone-3-sulphate (E1-3S) excreted by livestock constitute a potential source for estrogen contamination in the environment. A method was developed to separate and quantify the hormones by high-performance-liquid-chromatography (HPLC) and ultraviolet detection (UV). A combination of dichloromethane (DCM) and dicyclohexylamine hydrochloride (DCH·HCl) gave recoveries from 97.3 to 107% for E1-3S extraction from aqueous solutions. The recoveries from soil samples ranged from 80.9 to 95.2% (E2-3S), and from 86.3 to 91.7% (E1-3S), respectively. Results of batch sorption studies showed that Freundlich isotherms were nonlinear (N ≠ 1) with Kf values ranging from 34.2 to 57.2, and from 3.42 to 4.18 mg¹-N LN kg⁻¹ for E1, and E1-3S, respectively, indicating the sorption affinity of E1-3S was about an order of magnitude lower than that of E1. The hydrophilic sulphate group of E1-3S possibly shielded the compound from hydrophobic interactions with the soil organic matter and allophanic clay minerals that were proposed as sorbents for E1. Contraction of clay minerals, “salting out” and competitive sorption of artificial urine constituents were likely to have been responsible for observed changes in Freundlich parameters when artificial urine was used as mediator matrix. Plotting the effective distribution coefficient as a function of hypothetical exposure concentrations facilitated the comparison of the sorption behaviour of both compounds as influenced by the mediator solution. The results emphasized that using the CaCl₂ matrix might result in false inferences for the sorption behaviour of these compounds in a dairying environment. The four hormones rapidly degraded in the agricultural soils under aerobic conditions, and the majority of the compounds degraded > 50% within the first 24 hrs. Soil arylsulphatase activities were directly correlated with degradation rate constants of the estrogen sulphates. Estrone was identified as a metabolite of E2 and E1-3S, and these three compounds were observed as metabolites of E2-3S. Single-first order (SFO) and double first-order in parallel (DFOP) kinetics were used to model the degradation and metabolite formation data. The results showed that the DFOP model was in most cases better able to predict the parent compound degradation than the SFO model, and also enabled to estimate accurate degradation endpoints. ER-CALUX® analysis revealed the formation of estrogenicity during E2-3S degradation, which could partly be explained by the formation of the metabolites E2 and E1. Transport studies with E1-3S and E1 showed that the transport and retention of both compounds were significantly influenced by the mediator matrix. While no breakthrough curves (BTCs) were recorded during hormone application in CaCl₂ (10 mM) both hormones were detected in the leachate when applied in artificial urine. Rate-limited sorption processes were proposed for the delayed arrival of the hormone BTCs compared with a conservative bromide tracer. Intense colouration of the leachate during the artificial urine experiments suggested the hormones were likely to be moved by colloid-facilitated transport. Furthermore, the detection of residue hormone and metabolite concentrations implied that degradation of E1-3S and E1 was hampered by urine constituents such as glycine and urea.

30

Lauzon, Louise. „Evaluation of a three dimensional cloud chemistry model“. Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56995.

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To evaluate the precision of a three dimensional cloud chemistry model, the ion concentrations of simulated clouds are compared with the chemical analysis of cloud water samples collected in the Muskoka, Ontario area. Five summer case studies are presented.
In general, the simulated concentrations of NO$ sbsp{3}{-},$ NH$ sbsp{4}{+},$H$ sp+$, H$ sb2O sb2$ and the concentrations of SO$ sbsp{4}{2-}$ calculated with the perfect nucleation condition concur with the observed concentrations. For the four polluted cases, more than 80% of the cloud water SO$ sbsp{4}{2-}$ comes from nucleation, whereas for the clean case, it is mostly created by SO$ sb2$ oxidation. The relative importance of $ rm H sb2O sb2$ and O$ sb3$ in SO$ sb2$ oxidation, as well as the relative importance of nucleation and NH$ sb3$ absorption on the cloud water NH$ sbsp{4}{+}$ budget vary according to the chemical state of the atmosphere.

31

Singh, Ajit. „Quantifying the effect of atmospheric pollution and meteorology on visibility and tropospheric chemistry“. Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7828/.

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There are two distinct research foci within this thesis; the role of aerosol particle and trace gases on (i) visibility and (ii) tropospheric chemistry. This work investigates short and long term visibility, by exploring the combined influence of atmospheric aerosol and meteorology. Observations were fitted to a newly developed light extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties, explaining long term visibility trends and their dependence on meteorological conditions. This model incorporates parameterizations of aerosol hygroscopicity, gas absorption and particle concentration, scattering, and absorption. Historical visibility data can therefore be used to assess trends in aerosol particle properties for time periods when observational data are scarce or non-existent. Short term visibility variations caused by particulate matter from firework and bonfire emissions is presented. It is shown that a reduction in the atmospheric visibility nationwide is -25%; which is a consequence of increased loading of atmospheric PM, and is found to be dependent upon relative humidity. Within tropospheric chemistry, HONO is an important source of OH radicals, and daytime HONO sources are poorly constrained. This work explores the abundance of HONO during a solar eclipse as a natural short-term perturbation to atmospheric photochemistry. A chemical kinetic model is employed to predict the concentrations of HONO using different source scenarios. The study provides insights into the variation of HONO with meteorology, traffic emission and other source.

32

Moreno, Anjelica Victoria Peralez. „Modeling Atmospheric Transport of Perfluorinated Alkyl Substances from Chemours Facilities Using CALPUFF View“. The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555004834088189.

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33

Hoh, Eunha. „Investigation of organochlorine and organobromine contaminants in the atmosphere“. [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3204532.

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Thesis (Ph. D.)--Indiana University, School of Public and Environmental Affairs, 2006.
Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0156. Adviser: Ronald A. Hites. "Title from dissertation home page (viewed Feb. 22, 2007)."

34

Lee, Hwan. „Development and Field-Deployment of an Absorption Spectrometer to Measure Atmospheric HONO and NO2“. Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10420.

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Field observations show daytime HONO levels in urban, rural and remote environments are greater than those expected at photostationary state, that is, balance between production by $NO+OH$ reaction and loss by UV-photolysis and OH-oxidation. Studies have interpreted measurements of $[HONO]_{Obs} > [HONO]_{PSS}$ - or equivalently, the rate of HONO loss exceeding that of production - as evidence of a missing, sunlight-driven HONO source. Formation rate inferred from assuming photostationarity indicate a significant source of HONO, which photolyzes to yield OH. Moreover, depending on the mechanism, it may represent a pathway by which deposited nitrogen oxides are repartitioned back into the atmosphere in reactive form. The accumulation of HONO beneath the nocturnal boundary layer initiates photochemistry in the early morning prior to other $HO_x$ precursors. Previous studies have estimated nighttime HONO production rate by attributing the increase in $HONO:NO_x$ solely to heterogeneous HONO formation, while treating $NO_x$ as an invariant. Moreover, because ambient $HONO:NO_x$ exceed what is observed in automobile exhaust, combustion sources are discounted. In May of 2009, we observed HONO and $NO_2$ mixing ratios in Houston, Texas during the SHARP campaign. We demonstrate – using a chemical box model – that photostationary state during daytime is not fully established. The reaction/transport time since emission from automobiles is short relative to the lifetime of HONO. The result of assuming PSS is a drastic over-estimation of the magnitude of the so-called missing HONO source. At night, we show that $NO_x$ oxidation and emission are significant, thus, $NO_x$ cannot be treated as a conservative tracer to infer secondary HONO production. Nearly-continuous observations of HONO and $NO_2$ at Harvard Forest from December 2010 to December 2011 reveal daytime HONO levels that are comparable to what is expected from just known chemistry and much lower than has been reported in similar environments by different measurement techniques. Moreover, HONO fluxes are always below detection limit, indicating daytime HONO production contributes negligibly to the $HO_x$ and $NO_x$ budgets of the overlying atmosphere at Harvard Forest. Nighttime HONO enhancement is observed, but high night-to-night variability in $HONO:NO_2$ that is not reasonably explained by the trends in HONO and $NO_2$ fluxes, suggest a non-$NO_2$, non-ground/canopy-surface related HONO source.
Engineering and Applied Sciences

35

Scharko, Nicole K. „Nitrous acid sources on atmospherically relevant surfaces“. Thesis, Indiana University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10196158.

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Nitrous acid (HONO) is a photochemical source of hydroxyl radical that plays an important role in initiating radical reactions leading to photochemical air pollution and aerosol formation in the lower atmosphere. Field studies suggest nocturnal and daytime HONO sources that stem from heterogeneous reactions on environmental surfaces. However, the mechanisms are not well-understood and atmospheric models under-predict daytime HONO levels by 30–50%. The main aim of this research is to examine proposed nocturnal and daytime sources with a focus on elucidating the mechanisms of HONO formation and understanding the variables controlling this important process. Results from four projects are presented. The first project focuses on aqueous nitrate (₃^–) photolysis and the role that nitrogen dioxide (NO₂) hydrolysis plays in the formation process. The second involves linking the flux of HONO from agricultural and urban soil samples to ammonia oxidizing bacteria and archaea. The third project elucidates the mechanism of NO₂ reduction on surfaces containing humic acids (HA), specifically focusing on quinone and hydroquinone redox chemistry. The fourth project seeks to explain how nitrate photolysis on HA or iron surfaces can be an important daytime source of HONO. We suggest that NO₃^– photolysis in the presence of chromophoric compounds and OH radical scavengers, which are naturally present on the environment surfaces, help explain the higher than expected daytime HONO levels observed during recent field studies.

36

Hua, Wei. „Interfacial Water Organization and Ion Distributions Investigated with Vibrational Sum Frequency Spectroscopy: Answering Fundamental Questions for Environmental Chemistry“. The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385593745.

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37

Casillas-Ituarte, Nadia Ninel. „Spectroscopic Studies of Atmospheric Relevant Air-Aqueous and Air-Silica Interfaces“. The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268155570.

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38

O'Meara, Simon. „Estimating the volatility of aerosol components and diffusion through the particle-phase“. Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/estimating-the-volatility-of-aerosol-components-and-diffusion-through-the-particlephase(4b002229-b459-4f56-a51e-62a949519a44).html.

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Accurate models of aerosol transformation including partitioning between the gas- and particle-phase are needed for estimating their effects on climate and air quality. In this thesis, the process of partitioning between phases and its determining factors are introduced and investigated. Three studies assess: the accuracy of estimation methods for aerosol component volatility and its effect on particulate concentration and composition; the consistency of different solutions to models of particle-phase diffusion; and, a method to analytically solve particle-phase diffusion. These studies contribute to the ongoing effort of improving aerosol models, such that their wide-ranging effects can be accurately estimated.

39

Keyte, Ian James. „The concentrations, behaviour and fate of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in the urban atmosphere“. Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5869/.

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Polycyclic aromatic hydrocarbons (PAHs) play an important role in urban air quality due to the toxic and carcinogenic hazard they present. A class of pollutants receiving increasing interest from researchers are oxygenated (OPAH) and nitrated (NPAH) derivative compounds. There is a need for an improved understanding of the sources, concentrations, behaviour and fate of these pollutants as they can pose a similar public health risk as PAHs and can enter the environment both from primary combustion emissions and secondary formation from atmospheric reactions. This study investigates the airborne concentrations of PAH, OPAH and NPAH compounds in U.K. atmosphere at heavily trafficked and urban background sites. Sampling campaigns were conducted to assess the spatial and temporal trends, primary and/or secondary sources, gas-particle phase partitioning and atmospheric degradation of PAHs, NPAHs and OPAHs. Differences in atmospheric concentrations between trafficked sites and the urban background site indicate a variable influence of road traffic emissions between different PAH, OPAH and NPAH compounds. Seasonal, diurnal and temporal patterns as well as positive matrix factorisation (PMF) source apportionment provide evidence of the key influencing factors governing the concentrations of PAHs, OPAHs and NPAHs in the urban atmosphere, in addition to the strength of road traffic emissions.

40

Kenny, William T. „The Development and Application of the Hi-Resolution VOC Atmospheric Chemistry in Canopies Model“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439131044.

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41

Jang, Eun-Hwa. „Source identification and reactivity study on atmosphere polycyclic aromatic hydrocarbons“. Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5648/.

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Polycyclic aromatic hydrocarbons (PAH) are ubiquitous compounds produced through incomplete combustion processes from various sources in different proportions. They are of concern because of their recognized mutagenic and carcinogenic properties. There are a number of receptor modelling (RM) studies that identify sources of urban atmospheric PAH, despite concerns over the application of RM to the relatively reactive PAH. This thesis utilizes Positive Matrix Factorization (PMF) with extensive PAH datasets, and compares the results with local and national emission inventories. An atmospheric chemical reactivity study for PAH is also investigated; highlighting the importance of taking reactivity into consideration when applying source apportionment models. The results demonstrate that traffic sources are significantly responsible for the PAH mass (∑PAH) at UK urban sites throughout the year. A substantial fraction of benzo[a]pyrene emissions was apportioned to solid fossil fuel combustion sources, showing significant seasonal variations. A conceptual simulation of PAH ratios has been investigated using urban and rural data. Results were in good agreement between simulated ratios and empirically obtained values. The results provide a better understanding of PAH reactivity and their atmospheric fate, indicating the potential for long-range transport of high molecular weight PAH.

42

Geng, Dawei. „Gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry methods for the determination of environmental contaminants“. Doctoral thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-51727.

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The recent developments and improvements of instrumental methods for the analyses of the environmental contaminants, especially the persistent organic pollutants (POPs), have made it possible to detect and quantify these at very low concentrations in environmental and biotic matrices. The main objective of this thesis is to demonstrate the capability of the atmospheric pressure chemical ionization technique (APCI), using gas chromatography coupled to tandem mass spectrometry for the determination of a wide range of environmental contaminants, including the POPs regulated by Stockholm Convention, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), but also the derivates of PBDEs and novel brominated flame retardants (NBFRs). The APCI was operated in charge transfer condition, preferably producing molecular ions. Multiple reaction monitoring (MRM) experiments were optimized by adjusting cone voltage, collision energy and dwell time. Optimization of source parameters, such as gas flows and temperatures was also performed. Low concentration standards were analyzed, achieving a visible chromatographic peak for 2 fg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) demonstrating the excellent sensitivity of the system. Adequate linearity and repeatability were observed for all the studied compounds. The performance of APCI methods was validated against the conventional methods using gas chromatography coupled to high resolution mass spectrometry for chlorinated compounds in a wide range of matrices including environmental, air, human and food matrices. The GC-APCI-MS/MS method was successfully applied to a set of 75 human serum samples to study the circulating levels of POPs in epidemiologic studies. Moreover the method was utilized to establish temporal trends of POPs in osprey eggs samples collected during the past five decades.

43

Chabrillat, Simon H. „Modélisation du changement global dans l'atmosphère moyenne“. Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211595.

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Les abondances atmosphériques du dioxyde de carbone et du méthane augmentent progressivement, modifiant probablement le climat global de l'atmosphère. Bien que ces effets soient très étudiés dans la troposphère, ils le sont peu dans l'atmosphère moyenne (20 - 120 km) où ils pourraient avoir un impact plus facilement détectable. Nous nous intéressons en particulier à la mésosphère/basse thermosphère (MLT), où apparaissent de plus en plus souvent des nuages mésosphériques polaires (PMC). La MLT est sensible au niveau d'activité solaire, qui varie selon un cycle de onze ans.

Nous évaluons les impacts de ces deux changements anthropiques et de ce cycle naturel sur la température et la chimie de la MLT. Pour ce faire, nous participons au développement d'un modèle bidimensionnel de l'atmosphère :SOCRATES. Ce modèle calcule interactivement les moyennes zonales des vents, de la température et de la composition chimique de l'atmosphère en fonction de la latitude (85°S-85°N) et de l'altitude (0-120 km). Avant de nous intéresser au changement global, nous avons dû améliorer SOCRATES pour qu'il reproduise au mieux la situation chimique, dynamique et thermique actuellement observée.

Nous avons ainsi modifié la résolution du système chimique; développé une nouvelle paramétrisation de l'absorption par O2 du rayonnement solaire ultraviolet à Lyman-&61537; (121.6 nm) [Chabrillat et Kockarts, 1997] ;créé une approximation des sources thermosphériques de NO; paramétrisé le forçage dynamique par déferlement des ondes de gravité pour reproduire de manière très réaliste les observations actuelles de température dans la MLT ;et développé un algorithme pour prendre en compte non seulement la diffusion turbulente mais aussi la diffusion moléculaire. Tous ces développements sont décrits en détail, et leurs effets sur la physico-chimie de la. MLT sont analysés. Les concentrations chimiques calculées par le modèle sont comparées avec succès à des observations - en particulier de l'ozone et du radical hydroxyle.

Nous étudions ensuite en détail l'impact du cycle solaire de onze ans sur la MLT. Une analyse complète du budget thermique nous permet d'établir, par exemple, que la raie Lyman-&61537; est responsable de la moitié du réchauffement entre SOLMIN et SOLMAX. Nous évaluons alors la sensibilité de la MLT à un doublement (théorique) de l'abondance de C02. Nous trouvons qu'aux hautes latitudes et en été, zone d'apparition des PMC, cet effet est très faible. Puis nous réalisons une simulation où le méthane est ramené à son niveau préindustriel. L'accroissement de CH4 depuis cette époque est responsable, non seulement de l'augmentation de la vapeur d'eau dans l'atmosphère moyenne, mais aussi d'un léger refroidissement dans la MLT. Cet effet est maximal dans les régions polaires et en été, là où les deux autres sont minimaux.

Nous concluons par une grande simulation intégrée de l'évolution du climat et de la chimie de l'atmosphère moyenne au cours du XXIe siècle. Nous trouvons qu'au niveau d'apparition des PMC, la tendance au refroidissement est plus faible que partout ailleurs. Par contre, la vapeur d'eau augmente plus rapidement en été qu'en hiver. Ces calculs fournissent des indices pour réconcilier les observations plus fréquentes des PMC avec une synthèse des températures mesurées dans l'été arctique, selon laquelle les températures n'auraient pas varié depuis quarante ans.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

44

Inumula, Vamshi. „Characterization and quantitative determination of aromatics, nitrogen, sulfur and trace metals in fuel and hydrocarbon samples“. Youngstown State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1377188620.

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45

Malone, Marvin Jr. „Plasmonic Sensing And Spectroscopy of Subwavelength Particles with an Infrared Microscope“. The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354561034.

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46

Matta, Anand. „Laser Spectroscopy Sensor for Measurements of Trace Gaseous Sulfur Dioxide (SO₂)“. Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1229541167.

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47

Peebles, Brian Christopher. „Pulmonary Toxicity of Manufactured Nanoparticles“. The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274902471.

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48

Cosme, Emmanuel. „Cycle du soufre des moyennes et hautes latitudes Sud dans un modèle de circulation générale atmosphérique“. Phd thesis, Université Joseph Fourier (Grenoble), 2002. http://tel.archives-ouvertes.fr/tel-00705168.

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L'objectif de ce travail est de contribuer à la compréhension du cycle atmosphérique du soufre en Antarctique par l'utilisation d'un Modèle de Circulation Générale Atmosphérique (MCGA). Les versions "Antarctique" et "soufre" du MCGA LMD-ZT ("Laboratoire de Météorologie Dynamique- Zoom Traceurs") ont été fusionnées pour l'étude à haute résolution Antarctique du cycle du soufre dans les moyennes et hautes latitudes Sud. Une méthode de forçage "latéral" de la circulation atmosphérique antarctique par des analyses du Centre Européen de Prévision Météorologique à Moyen Terme (CEPMMT) a été spécifiquement développée et appliquée. Le modèle a d'abord été évalué. Il représente correctement le cycle saisonnier des espéces soufrées aux sites d'observation en Antarctique. Plusieurs défauts ont cependant été identifiés , discutés, et certains ont été étudiés par des expériences numériques spécifiques. Ceci nous a permis, dans la suite de ce travail, de décrire de manière critique le cycle du soufre en Antarctique à partir des résultats du modèle. Le modèle a été utilisé pour trois applications. La première a été une mise en oeuvre directe du modèle, tel qu'il a été évalué, dans le but d'estimer les distributions spatiales, le cycle saisonnier dans les régions centrales, et le bilan annuel des espèces soufrées en Antarctique. La deuxième se présente sous forme d'études de sensibilité à la formulation des émissions de sulfure de diméthyle (DMS) océanique, que la phase d'évaluation a révélé comme déterminante pour la modélisation du cycle du soufre. Pour la troisième, l'adjoint du modèle de transport (qui, en première approximation, permet de remonter le temps), complété par l'adjoint du module chimique spécifiquement développé pour ce travail, a été mis en oeuvre pour une recherche quantitative de l'origine géographlque et de l'âge des espèces soufrées en Antarctique.

49

Losno, Rémi. „Chimie d'éléments minéraux en traces dans les pluies méditerranéennes“. Phd thesis, Université Paris-Diderot - Paris VII, 1989. http://tel.archives-ouvertes.fr/tel-00814327.

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L'objet de ce travail est de déterminer les causes de la partition de certains éléments-trace entre les phases aqueuse et insoluble . Ces éléments ont été choisis, d'une part pour leur importance dans les cycles biogéochimiques de la terre, et d'autre part pour leur intérêt dans la compréhension de la chimie de la pluie. Il s'agit des éléments Na, Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Cu, Zn et Pb. Pour mener à bien ces recherches, nous avons mis au point des méthodes de travail dans des conditions ultra propres, en insistant particulièrement sur le protocole de lavage du matériel utilisé. Nous décrivons ensuite les méthodes de prélèvement des pluies, de séparation des phases aqueuse et insoluble , et d'analyse des éléments étudiés. Ce développement a été rendu nécessaire pour pouvoir obtenir des données fiables sur les métaux traces. Afin de pouvoir exploiter au mieux les résultats obtenus, nous essayons de déterminer les mécanismes par lesquels la matière s'incorpore dans une goutte de pluie. Puis, en liaison avec les études conjointes sur l'aérosol, nous discutons de l'origine de cette matière et nous en concluons à la prédominance des apports sahariens pour Al, Si, Mn et Fe, et à l'importance des sources de pollution pour Cu, Zn, Pb, le phosphore montrant une origine mixte crustale et de pollution bien partagée. Les sources crustales et de pollution sont toutes suffisamment éloignées du point de prélèvement pour que la matière recueillie ait subi un transport à longue distance. Seule la source mari n e est présente localement. L'étude trajectographique des masses d'air associées à chacune des pluies, confirme à chaque fois la possibilité d'un tel transport, tout en indiquant le caractère presque systématiquement frontal des situations rencontrées. Ainsi, le mélange des polluants en provenance de l'Europe avec les produits de l'érosion éolienne des sols africains se trouve très favorisé dans la zone de front où prend naissance la précipitation. L'étude des balances ioniques et du pH montre alors de manière nette cette incorporation simultanée, dans les gouttes d'eau de pluie, des acides provenant des zones polluées et des composés crustaux (en particulier la calcite) neutralisant cette acidité. Enfin, la partie la plus importante de ce travail concerne la partition entre les phases soluble et insolubl e des éléments choisis. Nous avons pu montrer que certains éléments, comme le phosph o re et le mang a nèse , présentent une fraction d'origine de pollution entièrement soluble se séparant de la fraction crustale très peu soluble, voire insoluble. A l'opposée, l'al u minium e t le fer , d'origine uniquement crustale, sont en équilibre de solubilité avec l e ur hydroxyde situé à la surface des particules solides en suspension, pourvu qu'il ne soit pas entièrement dissous; pour le fer, cet hydroxyde représente en moyenne 15% de sa masse. D'une même f a çon, le c uivre , le zinc et le plomb sont en équilibre d'adsorption-désorption entre la phase aqueuse et des oxydes hydratés de fer, de manganèse ou d'aluminium présents à la surface des particules solides en suspension dans la goutte d'eau de pluie. Ainsi, le devenir des éléments en équilibre dans la goutte de pluie dépendra fortement du milieu récepteur qui, en fixant de nouvelles conditions physico-chimiques, déplacera les équilibres de ces éléments entre les phases solubles et insolubles.

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„Characterization of Atmospheric Organic Matter and its Processing by Fogs and Clouds“. Doctoral diss., 2014. http://hdl.handle.net/2286/R.I.27527.

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abstract: The atmosphere contains a substantial amount of water soluble organic material, yet despite years of efforts, little is known on the structure, composition and properties of this organic matter. Aqueous phase processing by fogs and clouds of the gas and particulate organic material is poorly understood despite the importance for air pollution and climate. On one hand, gas phase species can be processed by fog/cloud droplets to form lower volatility species, which upon droplet evaporation lead to new aerosol mass, while on the other hand larger nonvolatile material can be degraded by in cloud oxidation to smaller molecular weight compounds and eventually CO2. In this work High Performance Size Exclusion Chromatography coupled with inline organic carbon detection (SEC-DOC), Diffusion-Ordered Nuclear Magnetic Resonance spectroscopy (DOSY-NMR) and Fluorescence Excitation-Emission Matrices (EEM) were used to characterize molecular weight distribution, functionality and optical properties of atmospheric organic matter. Fogs, aerosols and clouds were studied in a variety of environments including Central Valley of California (Fresno, Davis), Pennsylvania (Selinsgrove), British Columbia (Whistler) and three locations in Norway. The molecular weight distributions using SEC-DOC showed smaller molecular sizes for atmospheric organic matter compared to surface waters and a smaller material in fogs and clouds compared to aerosol particles, which is consistent with a substantial fraction of small volatile gases that partition into the aqueous phase. Both, cloud and aerosol samples presented a significant fraction (up to 21% of DOC) of biogenic nanoscale material. The results obtained by SEC-DOC were consistent with DOSY-NMR observations. Cloud processing of organic matter has also been investigated by combining field observations (sample time series) with laboratory experiments under controlled conditions. Observations revealed no significant effect of aqueous phase chemistry on molecular weight distributions overall although during cloud events, substantial differences were apparent between organic material activated into clouds compared to interstitial material. Optical properties on the other hand showed significant changes including photobleaching and an increased humidification of atmospheric material by photochemical aging. Overall any changes to atmospheric organic matter during cloud processing were small in terms of bulk carbon properties, consistent with recent reports suggesting fogs and clouds are too dilute to substantially impact composition.
Dissertation/Thesis
Doctoral Dissertation Chemistry 2014

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