Made available in DSpace on 2014-10-09T12:54:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:22Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2016-08-12T18:48:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-28. Added 1 bitstream(s) on 2016-08-12T18:51:02Z : No. of bitstreams: 1 000857374_20170828.pdf: 379492 bytes, checksum: 5aa1b5a8aea51344d394f7da2fb3f7be (MD5) Bitstreams deleted on 2017-09-01T13:14:05Z: 000857374_20170828.pdf,. Added 1 bitstream(s) on 2017-09-01T13:15:02Z : No. of bitstreams: 1 000857374.pdf: 2961329 bytes, checksum: c24b79805ac4ddeae7a32c878082f19d (MD5) / Neste trabalho foram desenvolvidos métodos sensíveis, seletivos, de custo reduzido com potencial para serem utilizados em aplicações ambientais e tecnológicas. Os princípios utilizados para determinação destes de diferentes analitos são baseados em reações de soluções aquosas, que produzem espécies coloridas, utilizadas como base de métodos óticos, envolvendo a aquisição e o processamento de imagens digitais. Os experimentos mostraram a viabilidade da utilização de sensores ópticos de aquisição de imagens digitais em sensores CMOS e CCD. Como resultados preliminares foram comparados sinais analíticos obtidos por espectrofotômetro e imagens digitais para determinação de nitrito, fosfato inorgânico e ozônio residual em água. As diferentes determinações mostraram que os resultados não diferem entre si com índice de confiança de 95%. Os resultados obtidos nos procedimentos experimentais que resultaram em dados confiáveis foram base para que fossem estabelecidos novos métodos para aplicações ambientais, como a determinação de SO2 e NO2 atmosférico Para a determinação de NO2 em ar foi utilizada a reação Griess-Saltzman (GS) com formação de corante róseo com absorção em 540 nm. As amostragens de ar foram feitas utilizado um cartucho C18 impregnado com TEA (trietanolamina) com vazão de 0,5 L min-1 e tempo de 60 min. O analito foi solubilizado com solução alcoólica de metanol/ água e recolhido em balão de 10,0 mL contendo 4,0 mL do reagente GS. Uma alíquota de 4,0ml foi colocada em uma superfície de acrílico e a imagens da solução foi digitalizada com um scanner. O processamento das imagens obtidas resultou em sinais analíticos proporcionais ao NO2. O limite de detecção foi de 12 ppb, com um erro relativo de 7,0 % e coeficiente de variação de 3,2 %. Para melhorar o limite de detecção o volume de solução foi otimizado (300 μL) e novo... / This work describes the development of sensitive, selective, and inexpensive methods with potential for use in environmental and technological applications. The techniques are based on reactions in aqueous solution that produce colored species that can be measured optically by means of the acquisition and processing of digital images. The experiments demonstrated the viability of using CMOS and CCD sensors to acquire digital images. In preliminary tests, comparison was made of analytical signals obtained using the digital image method and spectrophotometry, for measurements of nitrite, inorganic phosphate, and residual ozone in water. No statistically significant differences were observed between the two techniques, at a confidence level of 95%. The reliability of the results obtained using the new method then enabled new methods to be developed for environmental applications such as the determination of atmospheric SO2 and NO2. The determination of NO2 in air employed the Griess-Saltzman (GS) reaction, in which a rosecolored product is formed that absorbs at a wavelength of 540 nm. Air sampling was performed using C18 cartridges impregnated with triethanolamine (TEA), at a flow rate of 0.5 L min-1 for 60 min. The analyte was solubilized using an alcoholic solution of methanol/water, and then transferred to a 10.0 mL volumetric flask containing 4.0 mL of the GS reagent. A 4.0 mL aliquot was placed on an acrylic surface and digital images of the solution were acquired using a scanner. Processing of the images then resulted in analytical signals that were proportional to the NO2 concentration. The detection limit was 12 ppb, the relative error was 7.0 %, and the coefficient of variation was 3.2 %. In order to improve the detection limit, the solution volume was optimized (300 μL) and a new procedure for acquisition and treatment of the digital images was implemented, resulting in a reduction...

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Made available in DSpace on 2014-10-09T12:54:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:22Z (GMT). No. of bitstreams: 0 / O ozônio (O3) representa o principal poluente atmosférico para a Região Metropolitana de São Paulo (RMSP), sendo freqüentes os dias em que sua concentração excede os padrões nacionais de qualidade do ar. Por se tratar de um poluente secundário, resultante principalmente, da interação entre os óxidos de nitrogênio (NOx) e compostos orgânicos voláteis (COVs) na presença de luz solar, torna-se muito difícil a elaboração de estratégias eficazes para a redução deste poluente. A utilização de simulação computacional se mostra como uma interessante alternativa para avaliar os muitos fatores que afetam a formação de O3, para o desenvolvimento de escalas de reatividade para COVs e para definição de possíveis estratégias que visem a redução dos níveis de O3. Neste trabalho foi utilizado o modelo de trajetórias OZIPR (Ozone Isopleth Package for Research) em conjunto com o modelo químico SAPRC (Statewide Air Pollution Research Center) para se determinar a escala de reatividade incremental para COVs para a cidade de São Paulo e para a simulação de diversas situações de redução das emissões de NOx e COVs. Para alimentar os modelos foram utilizadas medidas de COVs de duas campanhas: uma realizada pelo Laboratório de Química Atmosférica (LQA-IPEN) em conjunto com a CETESB na estação Cerqueira César, no período de agosto e setembro de 2006 e outra realizada somente pelo LQA durante todo o ano de 2006 com amostragens na Cidade Universitária. Dados de CO, NOx e parâmetros meteorológicos foram obtidos através dos monitores automáticos da mesma estação e da estação Pinheiros. Foram criados cinco casos base: um com os dados de COVs da estação Cerqueira César e quatro com os dados da Cidade Universitária, sendo estes, um para cada estação do ano. Após o ajuste dos casos base, cada COV presente na mistura teve sua concentração aumentada e diminuída em 0,2% dos COVs totais para se verificar a variação no máximo de ozônio e assim se determinar o potencial de formação de ozônio de cada COV. Estes resultados forneceram uma escala de reatividade para ozônio para cada caso base criado. Foram também realizadas simulações, onde as emissões horárias de NOx e COVs foram reduzidas em 5, 10, 20 e 30% independente e simultaneamente afim de se verificar as variações na formação de O3. Com os dados de saída do simulador foram construídos gráficos de isopletas de ozônio para a cidade de São Paulo. A análise dos resultados obtidos mostrou que os compostos encontrados com mais freqüência entre os dez principais precursores de ozônio na cidade de São Paulo nas escalas de reatividade criadas a partir dos cinco casos base são: formaldeído, acetaldeído, propeno, isopreno, cis e trans 2-buteno, sendo o formaldeído sempre o principal composto formador de ozônio. As simulações mostraram também que uma estratégia eficaz para se reduzir os níveis de O3 na cidade de São Paulo é diminuir as emissões totais de COVs. O mesmo não foi observado para os NOx, já que a redução destes poluentes faria aumentar as concentrações de O3. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Atmospheric aerosols affect climate directly by scattering and absorbing solar radiation, and indirectly by affecting the albedo and lifetime of clouds through their role as cloud condensation nuclei. Aerosol sources, and the processes that govern their evolution in the atmosphere are not well understood, making the aerosol effects a significant source of uncertainty in future climate predictions. The tropics experience a large solar flux meaning that any radiative forcing in this region is particularly important. Despite this, there is a paucity of data from the tropics, with the majority of previous studies performed in the northern mid-latitudes. The few in-situ studies of aerosol composition that have been performed are all in the continental settings of Amazonia or Africa. Until now the 'maritime continent' region of South East Asia has remained unstudied. Presented here are Aerosol Mass Spectrometer composition measurements from the Oxidant and Particulate Processes Above a South East Asian Rainforest project, performed from ground and airborne measurement platforms in and around the rainforest of Borneo, South-East Asia. Unlike the previous tropical studies, this allows for the characterisation of a region of mixed terrestrial and marine biogenic emissions. The region is also undergoing rapid land use change, with forest being converted for agriculture, particularly the cultivation of oil palms. This study also allows for the characterisation of a region that is beginning to undergo land use change, providing insight into emissions from different land use types, and providing a benchmark to measure the effects of land use change against in the future.Total sub-micron aerosol loadings were found to be lower than studies in the northern mid-latitudes, similar to previous tropical studies. However, aerosol composition was different to that observed in Amazonia, with much greater sulphate loadings in Borneo. A regional background of sulphate and highly oxidised organic aerosol was identified, with organic aerosol that is less oxidised originating inland. Aerosol confined to a shallow marine boundary layer upwind of Borneo is lofted higher into the troposphere as it advects across the island, with regional aerosol being removed and biogenic terrestrial aerosol added. The lofting of this aerosol is expected to extend its atmospheric lifetime and change its role in the Earth's radiative budget. A novel organic aerosol signal was identified which correlated with gas phase isoprene oxidation products, strongly suggesting that it was significant of isoprene SOA. Aerosol associated with this signal made up a substantial fraction of the organic aerosol loading. This opens up the opportunity for future studies to make isoprene SOA measurements using the Aerosol Mass Spectrometer in other studies. A substantial amount of the organic aerosol in Borneo was attributed to isoprene oxidation.

Given the rapid rise in global mean temperature as a direct consequence of increasing levels of greenhouse gases (GHGs) emissions, various climate geoengineering techniques, for example, solar radiation management (SRM), have been suggested. Often criticized as a distraction from global efforts of removing and reducing GHGs, most notably carbon dioxide (CO2), SRM involves both marine cloud brightening (MCB) and stratospheric aerosol injection (SAI), both of which are based on increasing the Earth’s albedo by seeding aerosols in the marine boundary layer and in the lower stratosphere, respectively. SAI has been explored more extensively in various modeling studies following observations of major volcanic eruptions. A significant loading of sulfate particles, a byproduct of the eruptions, were monitored to cool the Earth’s surface temperature temporarily, albeit with some significant consequences including increasing stratospheric ozone (O₃) depletion and reducing precipitation. For our studies, we solely focused on the application of SAI by studying relevant heterogeneous chemistry of alternative aerosols to sulfate, specifically, calcite (CaCO₃) aerosols, to better understand the aerosols’ unintended impact on stratospheric O3 level. CaCO₃ aerosols, often serve as an idealized proxy for calcium-rich mineral dust, have been modeled to have minimal negative impact on both stratospheric O₃ level, through heterogeneous chemistry, and stratospheric temperature. However, only a few laboratory studies have been done on the heterogeneous chemistry of CaCO₃ aerosols with relevant stratospheric trace gases, such as HNO3 and HCl. These gases play a significant role in O₃ catalytic loss cycles in the stratosphere. Since HNO₃ is a common oxidation product of nitrogen oxides which contribute significantly to urban air pollution, a handful of ambient laboratory studies of CaCO₃ heterogeneous reaction with HNO₃ have been conducted. However, very little is known about CaCO₃ heterogeneous chemistry with HCl. Thus, the modeled impact of CaCO₃ aerosols on stratospheric O₃ so far may not be reliable given the lack of experimentally measured kinetics data. Here we report the results of an experimental study of the uptake of HNO₃ and HCl onto submicron CaCO₃ particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO₃ onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO₃ termination layer was detected in the form of a HCO₃¯ peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO₃ with Ca(OH)(HCO₃) to produce Ca(NO₃)2, water, and CO₂. HCl reacted with Ca(OH)(HCO₃) to produce CaCl₂ and also water and CO₂. The depletion of the Ca(OH)(HCO₃)/Ca(CO₃) signal due to reaction with HNO3₃ or HCl followed pseudo-first order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO₃ was determined to be in the range of 0.013 ≤γ_(HNO₃) ≤0.14, and that for HCl was 0.0011 ≤γ_HCl ≤0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO₃ aerosols was also studied in an aerosol flow tube (AFT) coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γ_HCl was determined to be 0.013  0.001. However, the heterogeneous chemistry of CaCO₃ aerosols at stratospheric conditions is still underexamined. We studied the kinetics of HCl uptake on airborne CaCO₃ aerosols at stratospheric temperature, 207 ± 3 K, by performing experiments under dry conditions. Using the same aerosol generation and characterization method, we coupled a low-temperature flow tube with the CIMS for HCl detection. The reactive uptake coefficient for HCl was measured to be 0.076 ± 0.009. This exceeds the reactive uptake coefficient of 0.013 ± 0.001 that we previously reported for this system at 296 K, consistent with the expected negative temperature dependence of gas uptake on solid surfaces. This finding suggests an initial strong reactive uptake of HCl gas on CaCO₃ aerosol surfaces in the stratosphere. Following the most recent modeling studies, our initial kinetic results suggest that the reactions of HCl and HNO₃ with CaCO₃ in the stratosphere could lead to a O₃ column change between -5% and +25%. This wide range of O₃ impact highlights the high uncertainties in estimating the true atmospheric impact of CaCO₃ aerosols, the most well-studied proposed SAI aerosols after sulfate, upon its release into the stratosphere. Nevertheless, our kinetic study establishes a good experimental standard for studying airborne aerosol heterogeneous chemistry under stratospheric conditions as a necessary step to evaluate SAI as a realistic method to battle global warming.

Orientador: Arnaldo Alves Cardoso / Banca: Orlando Fatibello Filho / Banca: Paulo Clairmont Feitosa de Lima Gomes / Banca: Boaventura Freire dos Reis / Banca: Fabíola Manhas Verbi Pereira / Resumo: Neste trabalho foram desenvolvidos métodos sensíveis, seletivos, de custo reduzido com potencial para serem utilizados em aplicações ambientais e tecnológicas. Os princípios utilizados para determinação destes de diferentes analitos são baseados em reações de soluções aquosas, que produzem espécies coloridas, utilizadas como base de métodos óticos, envolvendo a aquisição e o processamento de imagens digitais. Os experimentos mostraram a viabilidade da utilização de sensores ópticos de aquisição de imagens digitais em sensores CMOS e CCD. Como resultados preliminares foram comparados sinais analíticos obtidos por espectrofotômetro e imagens digitais para determinação de nitrito, fosfato inorgânico e ozônio residual em água. As diferentes determinações mostraram que os resultados não diferem entre si com índice de confiança de 95%. Os resultados obtidos nos procedimentos experimentais que resultaram em dados confiáveis foram base para que fossem estabelecidos novos métodos para aplicações ambientais, como a determinação de SO2 e NO2 atmosférico Para a determinação de NO2 em ar foi utilizada a reação Griess-Saltzman (GS) com formação de corante róseo com absorção em 540 nm. As amostragens de ar foram feitas utilizado um cartucho C18 impregnado com TEA (trietanolamina) com vazão de 0,5 L min-1 e tempo de 60 min. O analito foi solubilizado com solução alcoólica de metanol/ água e recolhido em balão de 10,0 mL contendo 4,0 mL do reagente GS. Uma alíquota de 4,0ml foi colocada em uma superfície de acrílico e a imagens da solução foi digitalizada com um scanner. O processamento das imagens obtidas resultou em sinais analíticos proporcionais ao NO2. O limite de detecção foi de 12 ppb, com um erro relativo de 7,0 % e coeficiente de variação de 3,2 %. Para melhorar o limite de detecção o volume de solução foi otimizado (300 μL) e novo... / Abstract: This work describes the development of sensitive, selective, and inexpensive methods with potential for use in environmental and technological applications. The techniques are based on reactions in aqueous solution that produce colored species that can be measured optically by means of the acquisition and processing of digital images. The experiments demonstrated the viability of using CMOS and CCD sensors to acquire digital images. In preliminary tests, comparison was made of analytical signals obtained using the digital image method and spectrophotometry, for measurements of nitrite, inorganic phosphate, and residual ozone in water. No statistically significant differences were observed between the two techniques, at a confidence level of 95%. The reliability of the results obtained using the new method then enabled new methods to be developed for environmental applications such as the determination of atmospheric SO2 and NO2. The determination of NO2 in air employed the Griess-Saltzman (GS) reaction, in which a rosecolored product is formed that absorbs at a wavelength of 540 nm. Air sampling was performed using C18 cartridges impregnated with triethanolamine (TEA), at a flow rate of 0.5 L min-1 for 60 min. The analyte was solubilized using an alcoholic solution of methanol/water, and then transferred to a 10.0 mL volumetric flask containing 4.0 mL of the GS reagent. A 4.0 mL aliquot was placed on an acrylic surface and digital images of the solution were acquired using a scanner. Processing of the images then resulted in analytical signals that were proportional to the NO2 concentration. The detection limit was 12 ppb, the relative error was 7.0 %, and the coefficient of variation was 3.2 %. In order to improve the detection limit, the solution volume was optimized (300 μL) and a new procedure for acquisition and treatment of the digital images was implemented, resulting in a reduction... / Doutor

Aerosols are known to have a large, uncertain effect on air quality and climate. Chemical processing of organic material in aqueous aerosols is known to form secondary organic aerosols (SOA), which make up a significant portion of particulate mass in the atmosphere. However, lack of clarity surrounding the importance of each source of SOA to total aerosol mass contributes to the uncertainties in their environmental impact. Disagreements between chemical models and field measurements suggest that some processes are misrepresented or are missing in current models. This work considers three pathways of SOA formation using Gas-Aerosol Model for Mechanism Analysis (GAMMA), a photochemical box model developed by the McNeill group featuring coupled gas phase and detailed aqueous phase aerosol chemistry. Imidazole-2-carboxaldehyde (IC), a light-absorbing organic species, has been observed to contribute to SOA formation as a photosensitizer. Currently, the extent of photosensitized reactions in ambient aerosols remains poorly constrained. Reactive uptake coefficients were determined from experimental studies of IC-containing aerosols and scaled for ambient simulations in GAMMA. Results of remote ambient simulations show that IC is unlikely to be a significant source of SOA largely due to its lack of abundance in atmospheric aerosols. Humic-like substances (HULIS) have also been experimentally shown to catalyze SOA formation through photosensitizer chemistry. We use GAMMA to quantify the uptake kinetics of limonene in these photosensitizer experiments. Ambient GAMMA simulations of this SOA formation pathway show that limonene-HULIS photosensitizer chemistry can contribute up to 65% of total aqueous SOA at pH 4. Further laboratory studies are recommended for this SOA source to assess the need for its inclusion in aerosol models. Chemical processing of organic material in cloudwater is another known source of SOA. We use GAMMA to consider the impact of the coupled effect of processing in both aqueous aerosol and cloudwater on isoprene epoxydiol (IEPOX) SOA. Simulations show that cloudwater at pH 3 – 4 can also be a potentially significant source of IEPOX SOA, largely due to higher water content in cloudwater than in aerosols. Thus, cloud processing may be a significant contributor to IEPOX SOA formation and could account for differences between predicted SOA mass and ambient measurements where mass transfer limitations in aerosol particles can be expected. This work concludes with recommendations for future work in GAMMA. Parameterization of glyoxal reactive uptake could allow for more accurate predictions of glyoxal oxidation product distributions. The inclusion of online thermodynamic calculations of inorganic species in GAMMA can better constrain several multiphase chemical processes, such as the highly pH-dependent uptake of IEPOX and sulfate formation. Updated detailed mechanisms of transition metal ion chemistry would also improve predictions of sulfate formation.

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