Atmos. Chem. Phys. Discuss., 12, 25181-25236, 2012
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Biological aerosol particle concentrations and size distributions measured in pristine tropical rainforest air during AMAZE-08
J. A. Huffman1,2, B. Sinha3,4, R. M. Garland2,*, A. Snee-Pollmann3,**, S. S. Gunthe2,***, P. Artaxo5, S. T. Martin6, M. O. Andreae2, and U. Pöschl2
1University of Denver, Department of Chemistry and Biochemistry, Denver, CO, USA
2Max Planck Institute for Chemistry, Biogeochemistry Department, Mainz, Germany
3Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany
4IISER Mohali, Department of Earth Sciences, S. A. S. Nagar, Manauli PO, India
5Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, Brazil
6Harvard University, School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Cambridge, MA, USA
*now at: Council for Scientific and Industrial Research (CSIR), Natural Resources and the Environment, Pretoria, South Africa
**now at: Roche Diagnostics GmbH, Pharma Research and Early Development, Penzberg, Germany
***now at: Indian Institute for Technology Madras, Department of Civil Engineering and EWRE Division, Chennai-36, India

Abstract. As a part of the AMAZE-08 campaign during the wet season in the rainforest of Central Amazonia, an ultraviolet aerodynamic particle sizer (UV-APS) was operated for continuous measurements of fluorescent biological aerosol particles (FBAP). In the coarse particle size range (> 1 μm) the campaign median and quartiles of FBAP number and mass concentration were 7.3 × 104 m−3 (4.0–13.2 × 104 m−3) and 0.72 μg m−3 (0.42–1.19 μg mm−3), respectively, accounting for 24% (11–41%) of total particle number and 47% (25–65%) of total particle mass. During the five-week campaign in February–March 2008 the concentration of coarse-mode Saharan dust particles was highly variable. In contrast, FBAP concentrations remained fairly constant over the course of weeks and had a consistent daily pattern, peaking several hours before sunrise, suggesting observed FBAP was dominated by nocturnal spore emission. This conclusion was supported by the consistent FBAP number size distribution peaking at 2.3 μm, also attributed to fungal spores and mixed biological particles by scanning electron microscopy (SEM), light microscopy and biochemical staining. A second primary biological aerosol particle (PBAP) mode between 0.5 and 1.0 μm was also observed by SEM, but exhibited little fluorescence and no fungal staining. This mode consisted of single bacterial cells, brochosomes and various fragments of biological material. Particles liquid-coated with mixed organic-inorganic material constituted a large fraction of observations, and these coatings contained salts likely from primary biological origin. We provide key support for the suggestion that real-time laser-induce fluorescence (LIF) techniques provide size-resolved concentrations of FBAP as a lower limit for the atmospheric abundance of biological particles. We also show that primary biological particles, fungal spores in particular, are key fractions of supermicron aerosol in the Amazon and that, especially when coated by mixed inorganic material, could contribute significantly to hydrological cycling in such regions of the globe.

Citation: Huffman, J. A., Sinha, B., Garland, R. M., Snee-Pollmann, A., Gunthe, S. S., Artaxo, P., Martin, S. T., Andreae, M. O., and Pöschl, U.: Biological aerosol particle concentrations and size distributions measured in pristine tropical rainforest air during AMAZE-08, Atmos. Chem. Phys. Discuss., 12, 25181-25236, doi:10.5194/acpd-12-25181-2012, 2012.
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