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Chemically resolved particle fluxes over tropical and temperate forests

Farmer, Delphine K.; Chen, Qi; Kimmel, Joel R.; Docherty, Kenneth S.; Nemitz, Eiko; Artaxo, Paulo A.; Cappa , Christopher D.; Martin, Scot T.; Jimenez, Jose L.. 2013 Chemically resolved particle fluxes over tropical and temperate forests. Aerosol Science and Technology, 47 (7). 818-830. 10.1080/02786826.2013.791022

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Abstract/Summary

Chemically resolved submicron (PM1) particlemass fluxes were measured by eddy covariance with a high resolution time-of-flight aerosol mass spectrometer over temperate and tropical forests during the BEARPEX-07 and AMAZE-08 campaigns. Fluxes during AMAZE-08 were small and close to the detection limit (<1 ng m−2 s−1) due to low particle mass concentrations (<1 μg m−3). During BEARPEX-07, concentrations were five times larger, with mean mid-day deposition fluxes of −4.8 ng m−2 s−1 for total nonrefractory PM1 (Vex,PM1 = −1 mm s−1) and emission fluxes of +2.6 ng m−2 s−1 for organic PM1 (Vex,org = +1 mm s−1). Biosphere–atmosphere fluxes of different chemical components are affected by in-canopy chemistry, vertical gradients in gas-particle partitioning due to canopy temperature gradients, emission of primary biological aerosol particles, and wet and dry deposition. As a result of these competing processes, individual chemical components had fluxes of varying magnitude and direction during both campaigns. Oxygenated organic components representing regionally aged aerosol deposited, while components of fresh secondary organic aerosol (SOA) emitted. During BEARPEX-07, rapid incanopy oxidation caused rapid SOA growth on the timescale of biosphere-atmosphere exchange. In-canopy SOA mass yields were 0.5–4%. During AMAZE-08, the net organic aerosol flux was influenced by deposition, in-canopy SOA formation, and thermal shifts in gas-particle partitioning. Wet deposition was estimated to be an order of magnitude larger than dry deposition during AMAZE-08. Small shifts in organic aerosol concentrations from anthropogenic sources such as urban pollution or biomass burning alters the balance between flux terms. The semivolatile nature of the Amazonian organic aerosol suggests a feedback in which warmer temperatures will partition SOA to the gas-phase, reducing their light scattering and thus potential to cool the region.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1080/02786826.2013.791022
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.4 - Develop innovative, effective methods for monitoring fluxes, exposure and effects
CEH Sections: Billett (to November 2013)
ISSN: 0278-6826
NORA Subject Terms: Ecology and Environment
Atmospheric Sciences
Date made live: 14 Aug 2013 13:15 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/502812

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