Atmospheric aerosols may be emitted directly as particles (primary) or formed from gaseous precursors (secondary) from different natural and anthropogenic sources. The highly populated South and East Asia regions are currently in a phase of rapid economic growth to which high emissions of carbonaceous aerosols are coupled. This leads to generally poor air quality and a substantial impact of anthropogenic aerosols on the regional climate. However, the emissions of different carbon aerosol components are still poorly constrained. Water-soluble organic carbon (WSOC) is a large (20-80%) component of carbonaceous aerosols that can absorb solar light and enhance cloud formation, influencing both the direct and indirect climate effects of the aerosols. A novel method for carbon isotope-based studies, including source apportionment, of the WSOC component of ambient aerosols was developed and tested for recovery efficiency and the risk of contamination using both synthetic test substances and ambient aerosols (paper I). The application of this method for the source apportionment of aerosols in South and East Asia shows that fossil fuel input to WSOC is significant in both South Asia (about 17-23%) highly impacted by biomass combustion practices and in East Asia (up to 50%) dominated by fossil energy sources (papers II, III, IV). Fossil fraction in WSOC in the outflow from northern China is considerably larger than what has been measured in South Asia, Europe and USA (paper IV). A trend of enrichment in heavy stable carbon isotopes in WSOC with distance the particles have been transported from the source is observed in the South Asian region (papers II, III). Dual-isotope (Δ14C and δ13C) analysis demonstrates that WSOC is highly influenced by atmospheric aging processes. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Submitted.</p>

abstract: Atmospheric particulate matter has a substantial impact on global climate due to its ability to absorb/scatter solar radiation and act as cloud condensation nuclei (CCN). Yet, little is known about marine aerosol, in particular, the carbonaceous fraction. In the present work, particulate matter was collected, using High Volume (HiVol) samplers, onto quartz fiber substrates during a series of research cruises on the Atlantic Ocean. Samples were collected on board the R/V Endeavor on West&ndash;East (March&ndash;April, 2006) and East&ndash;West (June&ndash;July, 2006) transects in the North Atlantic, as well as on the R/V Polarstern during a North&ndash;South (October&ndash;November, 2005) transect along the western coast of Europe and Africa. The aerosol total carbon (TC) concentrations for the West&ndash;East (Narragansett, RI, USA to Nice, France) and East&ndash;West (Heraklion, Crete, Greece to Narragansett, RI, USA) transects were generally low over the open ocean (0.36&plusmn;0.14 &mu;g C/m3) and increased as the ship approached coastal areas (2.18&plusmn;1.37 &mu;g C/m3), due to increased terrestrial/anthropogenic aerosol inputs. The TC for the North&ndash;South transect samples decreased in the southern hemisphere with the exception of samples collected near the 15th parallel where calculations indicate the air mass back trajectories originated from the continent. Seasonal variation in organic carbon (OC) was seen in the northern hemisphere open ocean samples with average values of 0.45 &mu;g/m3 and 0.26 &mu;g/m3 for spring and summer, respectively. These low summer time values are consistent with SeaWiFS satellite images that show decreasing chlorophyll a concentration (a proxy for phytoplankton biomass) in the summer. There is also a statistically significant (p<0.05) decline in surface water fluorescence in the summer. Moreover, examination of water&ndash;soluble organic carbon (WSOC) shows that the summer aerosol samples appear to have a higher fraction of the lower molecular weight material, indicating that the samples may be more oxidized (aged). The seasonal variation in aerosol content seen during the two 2006 cruises is evidence that a primary biological marine source is a significant contributor to the carbonaceous particulate in the marine atmosphere and is consistent with previous studies of clean marine air masses. / Dissertation/Thesis / M.S. Chemistry 2011

No description available.

Different aspects of natural organic matter composition and cycling have been studied using solid-state 13C and 31P Nuclear Magnetic Resonance (NMR) spectroscopy. Depending on the specific study, complementary analytical techniques such as elemental, isotopic and molecular analyses have also been applied. Samples from a variety of environments were examined including ocean waters, marine sediments and atmospheric aerosols. Studies from all these environments illustrate differences in natural organic matter composition resulting from various factors such as sources, cycling mechanisms and redox conditions. In the marine water column, organic matter of two different size fractions (dissolved and particulate) is found to have distinctly different bulk chemical and isotopic compositions. Overall, this indicates that particulate organic matter does not form from the simple physical aggregation of dissolved organic matter, and dissolved organic matter is not the primary source for particulate organic matter. Comparison of carbon and phosphorus compositional changes with depth in the ocean within the dissolved and particulate fractions reveals differences in cycling mechanisms. In the marine water column, selective mineralization of specific carbon compounds such as carbohydrates and amino acids occurs relative other species such as lipids. Whereas for phosphorus, the relative proportion of the different functional groups are unvarying with depth. In marine sediments, NMR spectroscopy reveals P cycling for specific phases such as polyphosphates is a function of sediment redox conditions. In atmospheric aerosols 13C NMR spectroscopy shows differences in water-soluble organic carbon composition from urban versus biomass burning sources. Urban aerosols have higher aliphatic and lower aromatic compound contents relative to samples derived from biomass burning. The results of these studies provide new insights into carbon and phosphorus cycling in the environment and demonstrate the capabilities of solid-state NMR as a tool for investigating natural organic matter composition.

[pt] O objetivo deste estudo foi determinar a concentração de metais, compostos orgânicos e inorgânicos por suspensão aquosa e análise dos metais por abertura ácida presentes nas amostras de PM10 coletadas em áreas urbanas, industrial e rural da Região Metropolitana do Rio de Janeiro. A concentração de PM10 foi determinada por análise gravimétrica. Espécies inorgânicas e orgânicas presentes nos extratos aquosos foram determinadas por cromatografia de íons e carbono orgânico total (TOC). Os extratos ácidos, e também os aquosos, foram analisados por ICP-MS (espectrometria de massa com plasma indutivamente acoplado) e por ICP OES (espectrometria de emissão óptica com plasma indutivamente acoplado) para determinar a concentração de metais. As correlações entre as concentrações de PM10 e de metais foram avaliadas, considerando os dados meteorológicos para cada ponto de coleta e origem das massas de ar. Os resultados mostraram que as concentrações médias de PM10 foram de 36 micrograma m-3 na área rural, 50 micrograma m-3 na área urbana e 74 micrograma m-3 na área industrial. A concentração de PM10 medida na área industrial ultrapassou, em geral, o limite estabelecido pela resolução CONAMA, de 50 micrograma m-3. O teor de metais apresentou maior concentração na área industrial, sendo predominantes ferro, zinco, alumínio, titânio, manganês, cromo, níquel, cádmio e chumbo. Na área de maior tráfego, foi detectada a maior concentração de cobre e vanádio. As espécies iônicas foram maiores na área urbana, devido à proximidade do oceano. Na área rural, menores concentrações de espécies antropogênicas, como sulfato, nitrato e alguns metais (Pb, Cr, V e Ni) foram medidas. Assim, as concentrações das espécies estudadas são influenciadas pelas características locais. Porém, também foi observado a influencia do transporte de poluentes de longa distância, como queimadas e poeiras dos desertos do continente africano. Os percentuais dos extratos ácido/aquoso demonstraram que os metais extraídos de forma mais eficiente foram V e Ni (maior que 45 porcento), enquanto que os menos extraídos foram Al e Fe (menor que 3 porcento), conforme o esperado. A fração aquosa é importante para avaliar a biodisponibilidade de metais associados a danos à saúde. / [en] The scope of this study was to measure the concentration of metals and organic and inorganic anions in aqueous and acid extracts of PM10 samples collected in urban, industrial and rural zones of Rio de Janeiro. PM10 concentration was determined by gravimetric analysis and the organic and inorganic species in the aqueous extracts were determined by ion chromatography and total organic carbon (TOC). The aqueous and acid extracts were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and by ICP OES (inductively coupled plasma optical emission spectrometry), in order to determine metal content. Correlations between PM10 and metal concentrations were evaluated, considering meteorological data for each site. Results showed that the average PM10 concentrations were 36 microgram m-3; 50 microgram m-3 and 74 microgram m-3 at the rural, downtown and industrial sites, respectively. The measured PM10 concentration in the industrial site exceeded the limit allowed by the Brazilian law, which is 50 microgram m-3. While industrial area had the highest concentrations of metals, such as Fe, Zn, Al, Ti, Mn, Cr, Ni, Cd and Pb, the highest concentrations of Cu and V were found in areas with higher traffic densities. Ionic species had higher concentrations in the urban site due to the proximity to the ocean. The lowest concentrations of species from anthropogenic sources, such as sulfate, nitrate and some metals (Pb, Cr, V and Ni) were measured in the rural area. Hence, studied species concentrations are influenced by site locations, but the influence by the transportation of long distance pollutants, such as biomass burning and dust from African deserts was also observed. The acid/aqueous percentiles showed that the most efficiently extracted metals in the aqueous phase were V and Ni (greater than 45 percent) while the less efficiently extracted were Al and Fe (less than 3 percent), as expected. The aqueous fraction is important to evaluate the bioavailability of metals that are associated to damage to the human health.