Size distributions and temporal variations of biological aerosol particles in the Amazon rainforest characterized by microscopy and real-time UV-APS fluorescence techniques during AMAZE-08

Abstract

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 7.3×10 4 m −3 (4.0-13.2×10 4 m −3 ) and 0.72 µg m −3 (0.42-1.19 µg m −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 coarsemode 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 true fungal staining. This mode may have consisted of single bacterial cells, brochosomes, various fragments of biological material, and small Chromalveolata (Chromista) spores. 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 using 355 nm excitation provide size-resolved concentrations of FBAP as a lower limit for the atmospheric abundance of biological particles in a pristine environment. We also show some limitations of using the instrument for ambient monitoring of weakly fluorescent particles < 2 µm. Our measurements confirm that primary biological particles, fungal spores in particular, are an important fraction of supermicron aerosol in the Amazon and that may contribute significantly to hydrological cycling, especially when coated by mixed inorganic material.

Long-term measurements (2010–2014) of carbonaceous aerosol and carbon monoxide at the Zotino Tall Tower Observatory (ZOTTO) in central Siberia

“…In pristine air over vegetated regions, bioaerosols are likely to be an essential regulating factor in the formation of precipitation (Pöschl et al, 2010;Pummer et al, 2012Pummer et al, , 2015Steiner et al, 2015). In the atmosphere, bioparticles undergo internal and external mixing with other aerosols, including SOA, which can influence bioaerosol properties through SOA coatings (Hallquist et al, 2009;Pöschl et al, 2010;Huffman et al, 2012;Pöhlker et al, 2012).…”

Global modeling of primary biological particle concentrations with the EMAC chemistry-climate model

“…The large size of pollen grains limits their ability to be detected by the WIBS, however, and 10 so fungal spores are assumed to represent the largest fraction of biological particles detected by the FL3 WIBS channel used here. Moreover, evidence in certain campaigns suggests that these fluorescence channels correlate well with fungal spores (e.g., (Fernandez-Rodriguez et al, 2018;Healy et al, 2014;Huffman et al, 2012)). Other important technical considerations were discussed in Section 2.3.2.…”

“…The observed values from each method are reported here with the relative factor that the FBAP concentration overcounts the spore counts from the optical technique shown in parentheses: Saclay -0.048 x 10 6 m -3 (spore 25 count), 0.088 x 10 6 m -3 (WIBS-4A; x1.8) and 0.027 x 10 6 m -3 (UV-APS; x0.6); Cyprus -0.0015 x 10 6 m -3 (spore count), 0.0433 x 10 6 m -3 (WIBS-4A; x29). In several other cases, collocated measurements of FBAP and spore counts also show spore count to be lower than FBAP by a factor of ~2 (Fernandez-Rodriguez et al, 2018) to as ~10 (Healy et al, 2014;Huffman et al, 2012), again depending partially on instrumental parameters and differences in aerosols observed. Additional direct comparison of FBAP concentrations with spore count concentrations summarized in this study (Table SI1 and Fig.…”

“…This implies that both biological and instrumental factors can lead to differences in observed FBAP concentrations. (Healy et al, 2014;Huffman et al, 2012) both discuss how certain types of spores may escape detection. In 5 particular, (Fernandez-Rodriguez et al, 2018;Healy et al, 2014) discuss how the genus Cladosporium (among the most commonly observed spore type in many environments) correlated very poorly with fluorescent measurements, suggesting that dark-walled cell walls present in this type of spores may inhibit some types of real-time fluorescence detection.…”

Diverse Chemical Mixing States of Aerosol Particles in the Southeastern United States

“…5 The CCSEM-EDX data sets were analyzed using k-means clustering of the elemental composition following the method described in Ault et al (2012) using codes written in MATLAB R2013b (MathWorks, Inc.). Clusters were grouped into source-based classes by elemental composition, including mineral dust Coz et al, 2009;Creamean et al, 2016;Laskin et al, 2005;Sobanska et al, 2003), SSA (Bondy et al, 2017b;Hopkins et al, 2008;Laskin et al, 2002), SOA/sulfate (Moffet 10 et al, 2013;O'Brien et al, 2015;Sobanska et al, 2003), biomass burning aerosol Posfai et al, 2003), fly ash/metals (Ault et al, 2012;Chen et al, 2012;Shen et al, 2016), biological particles (Huffman et al, 2012), and fresh soot . Soot forms fractal aggregates of graphitic carbon (C) which contain tens to hundreds of small spherical aggregates .…”