Abstract
Submicron atmospheric particles in the Amazon Basin were characterized by a high‐resolution aerosol mass spectrometer during the wet season of 2008. Patterns in the mass spectra closely resembled those of secondary‐organic‐aerosol (SOA) particles formed in environmental chambers from biogenic precursor gases. In contrast, mass spectral indicators of primary biological aerosol particles (PBAPs) were insignificant, suggesting that PBAPs contributed negligibly to the submicron fraction of particles during the period of study. For 40% of the measurement periods, the mass spectra indicate that in‐Basin biogenic SOA production was the dominant source of the submicron mass fraction, contrasted to other periods (30%) during which out‐of‐Basin organic‐carbon sources were significant on top of the baseline in‐Basin processes. The in‐Basin periods had an average organic‐particle loading of 0.6 μg m−3 and an average elemental oxygen‐to‐carbon (O:C) ratio of 0.42, compared to 0.9 μg m−3 and 0.49, respectively, during periods of out‐of‐Basin influence. On the basis of the data, we conclude that most of the organic material composing submicron particles over the Basin derived from biogenic SOA production, a finding that is consistent with microscopy observations made in a concurrent study. This source was augmented during some periods by aged organic material delivered by long‐range transport.
Highlights
[2] Organic material (OM) typically constitutes 70 to 90% of the fine mass fraction in the Amazon Basin [Fuzzi et al, 2007]
The campaign-average sulfate loading measured by the aerosol mass spectrometer (AMS) (0.15 ± 0.03 mg mÀ3;
Measurement periods that were influenced by changes in local winds that could have caused the exhaust of the on-site power generator or regional anthropogenic outflow from Manaus to arrive at the tower were excluded
Summary
[2] Organic material (OM) typically constitutes 70 to 90% of the fine mass fraction in the Amazon Basin [Fuzzi et al, 2007]. In-Basin biogenic SOA production can be concluded as the dominant source of submicron material during class I periods. The mass spectra (Figure 2a) have similar major peaks as those of laboratory SOA particles formed from the oxidation of individual biogenic precursors [Bahreini et al, 2005; Shilling et al, 2009].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
