resumo
Two-dimensional (2D) correlation spectroscopy, applied to one-dimensional solid-state cross polarization magic angle spinning (CP-MAS) C-13 nuclear magnetic resonance (NMR), Fourier transform infrared coupled to attenuated total reflectance (FTIR-ATR), and the combination of CP-MAS C-13 NMR and FTIR-ATR data, has been used to glean new structural information on the most hydrophobic water-soluble organic matter (WSOM) from fine urban air particles collected during different seasons. CP-MAS C-13 NMR analysis confirmed that unsubstituted saturated aliphatics, aromatics, oxygenated aliphatics, and carboxylic acids accounted for most (84-92%) of the characterized carbon functional groups. Applying 2D correlation spectroscopy to CP-MAS C-13 NMR and FTIR-ATR spectra indicates an increase in the contribution of hydroxyl and carboxylic groups to the aliphatic component with increasing air temperature, suggesting the photo-chemical origin of these WSOM structures. Urban samples from colder periods are clearly impacted by biomass combustion sources, although the presence of aged and processed organic aerosols cannot be ruled out. Using 20 FTIR-C-13 NMR hetero-spectral correlation spectroscopy, it has been demonstrated that the studied WSOM samples consists of at least two different classes of compounds: (i) an aliphatic component rich in both carboxylic and hydroxyl functional groups, and (ii) lignin-derived structures. (C) 2015 Elsevier Ltd. All rights reserved.
palavras-chave
MAGNETIC-RESONANCE-SPECTROSCOPY; ATMOSPHERIC AEROSOLS; UNITED-STATES; CHEMICAL-COMPOSITION; MASS-SPECTROMETRY; HUMIC-LIKE; MATTER; CARBON; SUBSTANCES; PARTICLES
categoria
Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences
autores
Duarte, RMBO; Freire, SMSC; Duarte, AC
nossos autores
Regina Duarte
Bolseiro de pós-DoutoramentoGrupos
agradecimentos
The Portuguese Institute for Development (IPAD) is acknowledged for financial support through a PhD grant attributed to Sandra M.S. Freire. This work was also funded by FEDER under the Operational Program for Competitiveness Factors - COMPETE and by National funds via the Portuguese Science and Technology Foundation (FCT) within the framework of research projects ORGANOSOL (PTDC/CTE-ATM/118551/2010) and CN-linkAIR (PTDC/AAG-MAA/2584/2012). This work was also supported by Centre for Environmental and Marine Studies (UID/AMB/50017/2013, University of Aveiro) and FCT, through the European Social Fund (ESF) and