Orientadores: Bernardino Ribeiro de Figueiredo, Arnaldo Alves Cardoso / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-21T20:13:34Z (GMT). No. of bitstreams: 1 Oliveira_PatriciaLopesde_D.pdf: 2941624 bytes, checksum: ce6f291eb7ceafda09c21f15d41abef1 (MD5) Previous issue date: 2012 / Resumo: O presente estudo foi realizado na cidade de Araraquara, a qual está inserida na região agroindustrial do Estado de São Paulo. Nesta região, a sazonalidade do cultivo da cana-de-açúcar exerce uma forte influência na química da atmosfera. A composição química das águas de chuva e do material particulado atmosférico grosso, fino e ultrafino foi investigada no período de agosto-setembro de 2009 (estação seca e período de safra) e no período de janeiro-março de 2010 (estação chuvosa e período de entressafra). Subsequentemente, a composição química do particulado total em suspensão (PTS) foi ainda investigada em amostras coletadas entre julho de 2010 e junho de 2011. As análises das partículas insolúveis das águas de chuva em MEV-EDS e do material particulado via DRX revelaram uma variedade de materiais incluindo matéria biogênica e carbonácea, resultantes de queimada, bem como minerais de argila, feldspato e óxidos que retratam a geologia local. No período do estudo, entre 46% e 65% do material particulado apresentava-se nas partículas menores que 1,9 ?m que é potencialmente a mais prejudicial à saúde humana, e que houve um aumento de 72% na concentração de MP10,2 no período de safra devido à intensificação das atividades agrícolas. Elevadas concentrações de Al, Fe, K, Ca e as fases minerais presentes em MPA indicaram que a ressuspensão de poeiras do solo, é a principal fonte de elementos traço no material particulado grosso. O material particulado fino concentrou mais de 50% do K, Zn, As, Cd, Sn e Pb. Já o material particulado ultrafino apresentou baixas concentrações de elementos como Fe, Mn, Al, Ca, Na, K, Cu, Pb, Zn, As, Cd e Sn. Com respeito à coleta de PTS, observou-se que o Ca e K representaram juntos 80% da concentração total de traços, o Mg e Fe apresentaram contribuição inferior a 10% cada um e Ti, V, Cr, Mn, Co, Ni, Sr, Zn e Pb representaram juntos 2,2% da concentração total determinada. Confirmando observações dos demais estudos, o potássio, utilizado como traçador de queima de biomassa, apresentou concentração cerca de 6 vezes mais elevada no período de safra do que no período de entressafra. Os elementos Mn, Fe, Co e Sr também exibiram as maiores concentrações no período de safra. A partir dos resultados das análises químicas e mineralógicas das amostras atmosféricas, bem como da aplicação de ferramentas estatísticas aos dados químicos, foi possível sugerir que as atividades locais/regionais, como a queima da palha da cana-de-açúcar, ressuspensão de poeiras do solo e emissões veiculares são as principais fontes de emissão de elementos traço para a atmosfera na região de Araraquara / Abstract: This study was conducted in Araraquara city, located in an important agroindustrial region in São Paulo State. In that region, the seasonality of the sugar cane crops is responsible for a great influence on the chemical composition of the atmosphere. The rainwater compositions as well as the course, fine and ultrafine atmospheric particulate matter were investigated from August-September 2009 (dry and burning season) and from January-March 2010 (wet and non-burning season). Subsequently, the chemical composition of the total suspended particulate (TSP) was further studied in samples collected from July 2010 and June 2011. SEM-EDS and XRD analyses in the insoluble fraction of rainwater and particulate matter samples, respectively, revealed a number of different sort of materials such as biogenic matter and black carbon, mainly originated from sugar cane burning, as well as clay minerals, feldspars and oxides that portrait the local geology. It was possible to verify that between 46% and 65% of particulate matter consisted of particles smaller than 1.9 ?m, which are the most harmful particles to the human health and that there was an increase of 72% in MP10.2 concentration in the harvest period due to intensive agricultural activities. High concentrations of Al, Fe, K, Ca and the mineral composition in particulate matter suggested that dust re-suspension are the mainly sources of trace elements in coarse particles. Fine particles accumulated more than 50% of K, Zn, As, Cd, Sn and Pb, while ultrafine particles showed low content of elements such as Fe, Mn, Al, Ca, Na, K, Cu, Pb, Zn, As, Cd and Sn. In relation to TSP, Ca and K represented 80% of the total trace element concentration, Mg and Fe contributed with less than 10% each one, while Ti, V, Cr, Mn, Co, Ni, Sr, Zn and Pb yielded only 2.2% of total concentration. In agreement with other previous researches, the concentration of potassium, taken as a biomass burning tracer, was about 6 times higher in harvest period than in non-harvest period. Mn, Fe, Co and Sr also exhibited the highest concentrations in harvest period. According to the chemical and mineralogical analyses, as well as the application of statistic tools to the chemical data, it is suggested that local and regional activities, such as sugar cane burning, dust re-suspension and vehicular emissions are the mainly sources of trace elements to the atmosphere in the region of Araraquara / Doutorado / Geologia e Recursos Naturais / Doutora em Ciências

I advanced the understanding of particle morphology and its implications for the behavior and effects of atmospheric aerosol particles. I have developed new experimental methods for the Aerosol Optical Tweezers (AOT) system and expanded the AOT’s application into studying realistic secondary organic aerosol (SOA) particle phases. The AOT is a highly accurate system developed to study individual particles in real-time for prolonged periods of time. While previous AOT studies have focused on binary or ternary chemical systems, I have investigated complex SOA, and how they interact with other chemical phases, and the surrounding gas-phase. This work has led to new insights into liquid-liquid phase separation and the resulting particle morphology, the surface tension, solubility, and volatility of SOA, and diffusion coefficients of SOA phases. I designed a new aerosol optical tweezers chamber for delivering a uniformly mixed aerosol flow to the trapped droplet’s position. I used this chamber to determine the phase-separation morphology and resulting properties of complex mixed droplets. A series of experiments using simple compounds are presented to establish my ability to use the cavity enhanced Raman spectra to distinguish between homogenous single-phase, and phase-separated core-shell or partially-engulfed morphologies. I have developed a new algorithm for the analysis of whispering gallery modes (WGMs) present in the cavity enhanced Raman spectra retrieved from droplets trapped in the AOT. My algorithm improves the computational scaling when analyzing core-shell droplets (i.e. phase-separated or biphasic droplets) in the AOT, making it computationally practical to analyze spectra collected over many hours at a few Hz. I then demonstrate for the first time the capture and analysis of SOA on a droplet suspended in an AOT. I examined three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ~ 75% relative humidity. For each system I added α-pinene SOA – generated directly in the AOT chamber – to the trapped droplet. The resulting morphology was always observed to be a core of the initial droplet surrounded by a shell of the added SOA. By combining my AOT observations of particle morphology with results from SOA smog chamber experiments, I conclude that the α-pinene SOA shell creates no major diffusion limitations for water, glycerol, and squalane under humid conditions. My AOT experiments highlight the prominence of phase-separated core-shell morphologies for secondary organic aerosols interacting with a range of other chemical phases. The unique analytical capabilities of the aerosol optical tweezers provide a new approach for advancing the understanding of the chemical and physical evolution of complex atmospheric particulate matter, and the important environmental impacts of aerosols on atmospheric chemistry, air quality, human health, and climate change.

Atmospheric aerosols play an important role in climate by scattering and absorbing radiation and by serving as cloud condensation nuclei. An aerosol’s optical or nucleation properties are driven by its chemical composition. Chemical aging of aerosols by atmospheric oxidants, such as ozone, alters the physiochemical properties of aerosol to become more hygroscopic, light absorbing, and viscous during transport. However the mechanism of these transformations is poorly understood. While ozone is a protective and beneficial atmospheric gas in the stratosphere, it is a potent greenhouse gas in the troposphere that traps heat near the Earth’s surface. It also impacts human heath by irritating the respiratory tract and exacerbating cardiovascular diseases. Additionally, ozone can alter the ecosystem through oxidizing plant foliage which can lead to deforestation and crop losses as well. Both gases and aerosols in the troposphere can react with ozone directly and indirectly with hydroxyl radicals. While daytime aging is thought to be primarily driven by photochemical processes and hydroxyl radicals, ozone is thought to be a key player in nighttime or dark aging processes that can alter the physicochemical properties of aerosols. Measured concentrations of trace gases and aged aerosol components in the field are higher than values predicted based on laboratory studies and computer simulations. Consequently, new experimental approaches are needed to narrow the gaps between observations and mechanistic understandings. In this dissertation, a plume of microdroplets was generated by pneumatically assisted aerosolization and then exposed to a flow of ozone before entering a mass spectrometer. This surface-specific technique allowed for the real-time analysis of reaction products and intermediates at the air-water interface. This work explores the in situ oxidation of iodide, a component of sea spray aerosols, by 0.05 – 13.00 ppmv ozone to explore how heterogeneous oxidation could enhance the production of reactive iodide species. Methods to study the reaction channels and intermediates were also established to not only determine a mechanism of iodide oxidation by ozone, but to enable the study of more complex systems. The developed approach was then applied to examine the oxidation of catechol and its substituted cousins, a family of compounds selected to model biomass burning and combustion emissions, at the air-water interface. While literature suggested that the primary mechanism of catechol oxidation by ozone would be the cleavage of the C1-C2 bond, it was determined that this was only a minor pathway. An indirect oxidation channel dominated heterogeneous processes at the air-water interface, giving rise to hydroxyl and semiquinone radicals that recombine to produce polyhydroxylated aromatics and quinones. This new mechanism of aging represents an overlooked channel by which brown, light-absorbing carbon aerosols are produced in the atmosphere. In addition, the work investigates how reactions on solid particulate aerosols proceed under variable relative humidity. Thin films were developed alongside a novel flow-through reactor to study of how aerosols are transformed by ozone and hydroxyl radicals when exposed to 50 ppbv - 800 ppmv of ozone. This system was employed to probe how catechol reacts with ozone under variable relative humidity. Further work was undertaken to model the adsorption process at the air-solid interface under variable humidity, permitting the estimation of the reactive uptake of ozone by the film at concentrations (50-200 ppbv) seen in rural and urban areas. Together, these results provide an increased understanding of how heterogeneous oxidation of aerosols contributes to aerosol aging processes as well as free radical production in the troposphere.

Ce travail de thèse a eu pour objectif une meilleure caractérisation, au niveau moléculaire, de l’aérosol organique atmosphérique, en lien avec les composés polyaromatiques. Cette étude s’est articulée autour de deux approches différentes mais complémentaires. Une étude de terrain conduite à Grenoble a permis d’appréhender les niveaux de concentration, la variabilité saisonnière et la répartition gaz/particule des hydrocarbures aromatiques polycycliques (HAP), oxy-HAP (OHAP) et nitro-HAP (NHAP), pendant une année entière. Ce travail de terrain a aussi permis d’appréhender les sources primaires et secondaires des OHAP et NHAP ainsi que de proposer des molécules marqueurs de ces processus de formation. Une étude complémentaire conduite en chambre de simulation atmosphérique a, quant à elle, eu pour but l’investigation de la formation d’aérosol organique secondaire (AOS), suite à la photooxydation du naphtalène et du 2-méthylnaphtalène. L’identification de la formation de produits organosoufrés de type organosulfates et sulfonates, à partir de la photooxydation de HAP gazeux, a été mise en évidence pour la première fois lors de cette thèse, ce qui a permis de proposer ces composés comme des marqueurs de formation d’AOS à partir des HAP. La capacité de ces AOS à absorber le rayonnement UV-Visible a été appréhendée et les molécules responsables de cette absorption ont été identifiées. Une caractérisation chimique poussée de l’AOS a mis en évidence sa dépendance aux différentes conditions expérimentales (type de particules d’ensemencement, acidité et humidité relative) et a conduit à l’identification et à la proposition de nouvelles voies réactionnelles. / This PhD work deals with a better characterization, at the molecular level of the organic atmospheric aerosol in relation to polycyclic aromatic compounds (PACs), and has been structured using two different but complementary approaches. Field measurements were conducted in Grenoble (France) and concentration levels, seasonal variability and gas/particle partitioning distribution of polycyclic aromatic hydrocarbons (PAHs), oxy-PAHs (OPAHs) and nitro-PAHs (NPAHs) have been investigated for one whole year. This field study allowed to a better understanding of primary vs secondary sources of OPAHs and NPAHs and specific molecular markers related to different sources have been identified. A complementary study was carried out using an atmospheric smog chamber, in order to investigate the formation of secondary organic aerosol (SOA) from the photooxidation of naphthalene and 2-methylnaphthalene, two of the most abundant PAHs in the gas-phase. The formation of organosulfates and sulfonates, from the oxidation of gaseous PAHs, has been highlighted for the first time in this work and these compounds have been proposed as potential SOA markers of PAH photooxidation. UV-Visible absorption of SOA generated during these experiments was investigated and led to the identification of specific molecules responsible for this absorption. A wide chemical characterization of SOA was performed and emphasized its dependence on many experimental factors (nature of seed particles, relative humidity and seed acidity) and allowed to propose some new chemical reaction pathways.

Ambient exposure to fine particulate matter (PM2.5) and ground-level ozone (O3) is identified as a leading risk factor for global disease burden. A major limitation to advancing our understanding of the cause and impacts of air pollution is the lack of observations with the spatial and temporal resolution needed to observe variability in emission, chemistry and population exposure. Satellite remote sensing, which fills a spatial gap in ground-based networks, is playing an increasingly important role in atmospheric chemistry. This thesis exploits satellite remote sensing observations to: (1) estimate human exposure to PM2.5 from remotely sensed aerosol optical properties; (2) identify the chemical regimes of surface O3 formation using satellite observations of O3 precursors. In the first part, we use a forward geophysical approach to derive PM2.5 distributions from satellite AOD at 1 km2 resolution over the northeastern US by applying relationships between PM2.5 and AOD simulated from a regional air quality model (CMAQ). We use multi-platform ground, airborne and radiosonde measurements to quantify multiple sources of uncertainties in the satellite-derived PM2.5. We find that uncertainties in satellite-derived PM2.5 are largely attributed to the varying relationship between PM2.5 and AOD that depends on the aerosol vertical distribution, speciation, aerosol optical properties and ambient relative humidity. To assess the value of remote sensing to improve PM2.5 exposure estimate, we compile multiple PM2.5 products that include information from remote sensing, ground-based observations and models. Evaluating these products using independent observations, we find the inclusion of satellite remote sensing improves the representativeness of surface PM2.5 mostly in the remote areas with sparse monitors. Due to the success of emission control, PM2.5-related mortality burden over NYS decreased by 67% from 8410 (95% confidence interval (CI): 4, 570 – 12, 400) deaths in 2002 to 2750 (95% CI: 700 – 5790) deaths in 2012. We estimate a 28% uncertainty in the state-level PM2.5 mortality burden due to the choice of PM2.5 products, but such uncertainty is much smaller than the uncertainty (130%) associated with the exposure-response function. The second part of the thesis focuses on ground-level O3. O3 production over urban areas is non-linearly dependent on the availability of its precursors: nitrogen oxides (NOx) and volatile organic compounds (VOCs). A major challenge in lowering ground-level O3 in urban areas is to determine the limiting species for O3 production (NOx-limited or VOC-limited). We use satellite observations of NO2 and HCHO to infer the relative abundance of NOx versus VOCs, thus to identify the O3 chemical regime. We first use a global chemical transport model (GEOS-Chem) to evaluate the uncertainties of using satellite-based HCHO/NO2 to infer O3 sensitivity to precursor emissions. Next, we directly connect this space-based indicator, retrieved consistently from three satellite instruments, to spatiotemporal variations in O3 recorded by on-the-ground monitors from 1996 to 2016. The nationwide emission reduction has led the O3 formation over U.S. urban areas to shift from VOC-limited to NOx-limited regime. Urban O3 monitors reveal trends consistent with this regime transition. Nonetheless, it is a major challenge for these retrievals to accurately depict day-to-day variability within urban cores. TROPOspheric Monitoring Instrument (TROPOMI) which launched in 2017, offers an unprecedented view to infer O3 chemistry at fine spatial and temporal scales. As an example, we use TROPOMI HCHO/NO2 to identify short-term changes in O3 sensitivity during the California Camp Fire. We find that the emissions from wildfires lead to NOx-saturated ozone formation near the fire source but NOx -limited conditions downwind. This thesis bridges basic research in atmospheric chemistry, which advances the state-of-science related to O3 and PM2.5 pollution from urban to global scales, and applied research in air quality management and public health, by quantifying the health benefits of emission control, and informs policymakers on which emission reductions to focus so as to maximize the cost-effectiveness of pollution controls. We show how space-based measurements can complement in situ networks and model simulations by providing information on the spatial heterogeneity and temporal evolution of PM2.5 exposure and O3 chemical regimes, which will lay the scientific foundation for interpreting future products retrieved from upcoming geostationary platforms.

Les composes carbonyles et BTEX (benzène, toluène, éthylbenzène et xylène) sont deux groupes importants de composés organiques volatils (COV) présents dans l'atmosphère. Ils ont une contribution significative à la formation d'oxydants tels que l'ozone, PAN et d'autres photo-oxydants dans la troposphère. En outre, ils ont des effets néfastes sur la santé humaine. Dans ce travail, les concentrations atmosphériques de carbonyles et d’hydrocarbures aromatiques ont été mesurées et quantifiées en utilisant des techniques HPLC et GC-MS sur un site de mesure semi-urbain à Orléans (ICARE, France), de juin 2010 à août 2011. D’autres mesures ont été conduites à Pékin (CAS-RCEES, Chine) du 6 au 28 Juin 2013 en utilisant les mêmes techniques expérimentales. Les résultats obtenus dans ces deux sites sont présentés, comparés et discutés. / Carbonyls and BTEX (benzene, toluene, ethyl-benzene and xylene) are two important groups of Volatile Organic Compounds (VOCs) present in the atmosphere. They have a significant contribution to the formation of oxidants such as ozone, PAN and other photooxidants in the troposphere. In addition, they have adverse effects on human health. In this work, atmospheric concentrations of carbonyls and aromatic hydrocarbons were measured and quantified using GC-MS and HPLC techniques at a semi-urban site in Orleans (ICARE, France), from June 2010 to August 2011. Urban ambient air sampling was also performed in 6-28th June 2013 in Beijing (RCEES-CAS, China). It has been conducted in order to compare the measured concentrations of the investigated species in two different sites using the same analytical techniques. All results are presented and discussed.

The work presented here represents a number of independent studies that investigated various components of the CH4 budget, namely the sources and sinks. We used a chemical-tracer model and created unique long-term time series of atmospheric CH4, carbon monoxide (CO), molecular hydrogen (H2), and methylchloroform (CH3CCl3) measurements at marine background air to derive histories of atmospheric hydroxyl radical (OH) - the main chemical oxidant of CH4, biomass burning - an important source of CH4 in the tropics, and emissions of CH4 from rice paddies - one of the largest anthropogenic sources of CH4, over decadal scales. Globally gridded inventories of CH4 emissions from rice paddies and terrestrial vegetation were created by synthesizing greenhouse and field CH4 fluxes, satellite-derived biophysical data, and terrestrial geospatial information.

Aerosols are a major source of uncertainty in estimates of anthropogenic effects on global radiative forcing and can pose serious health concerns. While many instrumental techniques capable of analyzing aerosol samples are available, individual-particle spectromicroscopic techniques like the ones presented here are the only ones to offer morphological and compositional measurements together. Studying the composition and mixing state of aerosol populations allowed for important aspects to be uncovered, such as: aerosol source, formation mechanism, hygroscopicity, optical properties, level of aging, and inhalation dangers. Ambient aerosols from the Amazon, both biogenic and anthropogenic, were apportioned based on their individual composition. Recently discovered organic aerosols from the central United States were identified and their chemical properties were characterized. The lead fraction of mixed lead- and zinc-rich particles from Mexico City was speciated to determine the lead’s solubility and possible bioavailability. It is through the use of these powerful spectromicroscopic techniques that a better understanding of complex mixed aerosols was achieved.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第18704号 / 地環博第127号 / 新制||地環||26(附属図書館) / 31637 / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 梶井 克純, 教授 杉山 雅人, 准教授 清中 茂樹 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

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