Bioaerosols in the Amazon rain forest: Temporal variations and vertical profiles of Eukarya, Bacteria and Archaea

Abstract. The Amazon rain forest plays a major role in global hydrological cycling and biogenic aerosols are likely to influence the formation of clouds and precipitation. Information about the sources and altitude profiles of primary biological aerosol particles, however, is sparse. We used fluorescence in situ hybridization (FISH), a molecular biological staining technique largely unexplored in aerosol research, to investigate the sources and spatiotemporal distribution of Amazonian bioaerosols on domain level. We found wet season bioaerosol number concentrations in the range of 1–5 · 105 m−3 accounting for > 70 % of the coarse mode aerosol. Eukaryotic and bacterial particles predominated, with fractions of ~56 % and ~26 % of the intact airborne cells. Archaea occurred at very low concentrations. Vertical profiles exhibit a steep decrease of bioaerosol numbers from the understory to 325 m height on the Amazon Tall Tower Observatory, with a stronger decrease of Eukarya compared to Bacteria. Considering earlier investigations, our results can be regarded as representative for near-pristine Amazonian wet season conditions. The observed concentrations and profiles provide unprecedented insights into the sources and dispersion of different types of Amazonian bioaerosols as a solid basis for model studies on biosphere-atmosphere interactions such as bioprecipitation cycling.

Download Full-text

Bioaerosols in the Amazon rain forest: temporal variations and vertical profiles of Eukarya, Bacteria, and Archaea

Biogeosciences ◽

10.5194/bg-18-4873-2021 ◽

2021 ◽

Vol 18 (17) ◽

pp. 4873-4887

Author(s):

Maria Prass ◽

Meinrat O. Andreae ◽

Alessandro C. de Araùjo ◽

Paulo Artaxo ◽

Florian Ditas ◽

...

Keyword(s):

Rain Forest ◽

Staining Technique ◽

Temporal Variations ◽

Vertical Profiles ◽

Wet Season ◽

Model Studies ◽

Amazon Rain Forest ◽

Low Concentrations ◽

Steep Decrease ◽

Biogenic Aerosols

Abstract. The Amazon rain forest plays a major role in global hydrological cycling, and biogenic aerosols are likely to influence the formation of clouds and precipitation. Information about the sources and altitude profiles of primary biological aerosol particles, however, is sparse. We used fluorescence in situ hybridization (FISH), a molecular biological staining technique largely unexplored in aerosol research, to investigate the sources and spatiotemporal distribution of Amazonian bioaerosols on the domain level. We found wet season bioaerosol number concentrations in the range of 1–5 × 105 m−3 accounting for > 70 % of the coarse mode aerosol. Eukaryotic and bacterial particles predominated, with fractions of ∼ 56 % and ∼ 26 % of the intact airborne cells. Archaea occurred at very low concentrations. Vertical profiles exhibit a steep decrease in bioaerosol numbers from the understory to 325 m height on the Amazon Tall Tower Observatory (ATTO), with a stronger decrease in Eukarya compared to Bacteria. Considering earlier investigations, our results can be regarded as representative for near-pristine Amazonian wet season conditions. The observed concentrations and profiles provide new insights into the sources and dispersion of different types of Amazonian bioaerosols as a solid basis for model studies on biosphere–atmosphere interactions such as bioprecipitation cycling.

Download Full-text

Supplementary material to "Bioaerosols in the Amazon rain forest: Temporal variations and vertical profiles of Eukarya, Bacteria and Archaea"

10.5194/bg-2020-469-supplement ◽

2021 ◽

Author(s):

Maria Prass ◽

Meinrat O. Andreae ◽

Alessandro C. de Araùjo ◽

Paulo Artaxo ◽

Florian Ditas ◽

...

Keyword(s):

Rain Forest ◽

Temporal Variations ◽

Vertical Profiles ◽

Amazon Rain Forest ◽

Supplementary Material

Download Full-text

Aerosol number fluxes over the Amazon rain forest during the wet season

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-9381-2009 ◽

2009 ◽

Vol 9 (24) ◽

pp. 9381-9400 ◽

Cited By ~ 28

Author(s):

L. Ahlm ◽

E. D. Nilsson ◽

R. Krejci ◽

E. M. M&aring;rtensson ◽

M. Vogt ◽

...

Keyword(s):

Rain Forest ◽

Large Scale ◽

Friction Velocity ◽

Aerosol Particles ◽

Deposition Flux ◽

Wet Season ◽

Transfer Velocity ◽

Aerosol Emission ◽

Amazon Rain Forest ◽

Particle Fluxes

Abstract. Number fluxes of particles with diameter larger than 10 nm were measured with the eddy covariance method over the Amazon rain forest during the wet season as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) campaign 2008. The primary goal was to investigate whether sources or sinks dominate the aerosol number flux in the tropical rain forest-atmosphere system. During the measurement campaign, from 12 March to 18 May, 60% of the particle fluxes pointed downward, which is a similar fraction to what has been observed over boreal forests. The net deposition flux prevailed even in the absolute cleanest atmospheric conditions during the campaign and therefore cannot be explained only by deposition of anthropogenic particles. The particle transfer velocity vt increased with increasing friction velocity and the relation is described by the equation vt = 2.4×10−3×u* where u* is the friction velocity. Upward particle fluxes often appeared in the morning hours and seem to a large extent to be an effect of entrainment fluxes into a growing mixed layer rather than primary aerosol emission. In general, the number source of primary aerosol particles within the footprint area of the measurements was small, possibly because the measured particle number fluxes reflect mostly particles less than approximately 200 nm. This is an indication that the contribution of primary biogenic aerosol particles to the aerosol population in the Amazon boundary layer may be low in terms of number concentrations. However, the possibility of horizontal variations in primary aerosol emission over the Amazon rain forest cannot be ruled out.

Download Full-text

A comparison of dry and wet season aerosol number fluxes over the Amazon rain forest

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-26881-2009 ◽

2009 ◽

Vol 9 (6) ◽

pp. 26881-26924

Author(s):

L. Ahlm ◽

E. D. Nilsson ◽

R. Krejci ◽

E. M. M&aring;rtensson ◽

M. Vogt ◽

...

Keyword(s):

Dry Deposition ◽

Rain Forest ◽

Particle Deposition ◽

Particle Flux ◽

Friction Velocity ◽

Deposition Velocity ◽

Dry Season ◽

Wet Season ◽

Deposition Velocities ◽

Amazon Rain Forest

Abstract. Vertical number fluxes of aerosol particles and vertical fluxes of CO2 were measured with the eddy covariance method at the top of a 53 m high tower in the Amazon rain forest as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment. The observed aerosol number fluxes included particles with sizes down to 10 nm in diameter. The measurements were carried out during the wet and dry season in 2008. In this study focus is on the dry season aerosol fluxes, with significant influence from biomass burning, and these are compared with aerosol fluxes measured during the wet season. The primary goal is to quantify the dry deposition sink and to investigate whether particle deposition velocities change when going from the clean wet season into the more polluted dry season. Furthermore, it is tested whether the rain forest is always a net sink of particles in terms of number concentrations, or if particle emission from the surface under certain circumstances may dominate over the dry deposition sink. The particle deposition velocity vd increased linearly with increasing friction velocity in both seasons and the relations are described by vdd=(2.7 u* −0.2)×10−3 (dry season) and vdw=2.5 u*×10−3 (wet season), where u* is the friction velocity. The fact that the two relations are very similar to each other indicates that the seasonal change in aerosol number size distribution is not enough for causing any significant change in deposition velocity. In general, particle deposition velocities in this study are low compared to studies over boreal forests. The reason is probably domination of accumulation mode particles in the Amazon boundary layer, both in the dry and wet season, and low wind speeds in the tropics compared to the midlatitudes. Net particle deposition fluxes prevailed in daytime in both seasons and the deposition flux was considerably larger in the dry season due to the much higher dry season particle concentration. In the dry season, nocturnal particle fluxes behaved very similar to the nocturnal CO2 fluxes. Throughout the night, the measured particle flux at the top of the tower was close to zero, but early in the morning there was an upward particle flux peak that is not likely a result of entrainment or local pollution. It is possible that these morning upward particle fluxes are associated with emission of natural biogenic particles from the rain forest. Emitted particles may be stored within the canopy during stable conditions at nighttime, similarly to CO2, and being released from the canopy when conditions become more turbulent in the morning.

Download Full-text

The Seasonal Cycle of the Radiation Budget and Cloud Radiative Effect in the Amazon Rain Forest of Brazil

Journal of Climate ◽

10.1175/jcli-d-16-0089.1 ◽

2016 ◽

Vol 29 (21) ◽

pp. 7703-7722 ◽

Cited By ~ 10

Author(s):

Allison B. Marquardt Collow ◽

Mark A. Miller

Keyword(s):

Water Vapor ◽

Rain Forest ◽

Radiant Energy ◽

River System ◽

Energy System ◽

Radiation Budget ◽

Impact Factors ◽

Flux Divergence ◽

Wet Season ◽

Amazon Rain Forest

Abstract Changes in the climate system of the Amazon rain forest of Brazil can impact factors that influence the radiation budget such as clouds, atmospheric moisture, and the surface albedo. This study examines the relationships between clouds and radiation in this region using surface observations from the first year of the deployment of the Atmospheric Radiation Measurement (ARM) Program’s Mobile Facility 1 (AMF1) in Manacapuru, Brazil, and satellite measurements from the Clouds and the Earth’s Radiant Energy System (CERES). The seasonal cycles of the radiation budget and cloud radiative effects (CREs) are evaluated at the top of the atmosphere (TOA), at the surface, and within the atmospheric column using these observations and are placed into a regional context using the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). Water vapor and clouds are abundant throughout the year, even though slight decreases are observed in the dry season. The column water vapor load is large enough that the longwave radiative flux divergence is nearly constant throughout the year. Clouds produce a significant shortwave CRE at the surface and TOA, exceeding 200 W m−2 during the wet season. Discrepancies, especially in column shortwave radiative absorption, between the observations and MERRA-2 are demonstrated that warrant additional analysis of the microphysical and macrophysical cloud properties in MERRA-2. More trustworthy fields in the MERRA-2 product suggest that the expansive nearby river system impacts the regional radiation budget and thereby renders AMF1 observations potentially biased relative to regions farther removed from rivers within the Amazon rain forest.

Download Full-text

Submicrometer aerosol particle size distribution and hygroscopic growth measured in the Amazon rain forest during the wet season

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jd000203 ◽

2002 ◽

Vol 107 (D20) ◽

Cited By ~ 90

Author(s):

Jingchuan Zhou

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Aerosol Particle ◽

Rain Forest ◽

Hygroscopic Growth ◽

Wet Season ◽

Amazon Rain Forest ◽

Aerosol Particle Size

Download Full-text

Aerosol number fluxes over the Amazon rain forest during the wet season

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-17335-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 17335-17383 ◽

Cited By ~ 1

Author(s):

L. Ahlm ◽

E. D. Nilsson ◽

R. Krejci ◽

E. M. M&aring;rtensson ◽

M. Vogt ◽

...

Keyword(s):

Rain Forest ◽

Friction Velocity ◽

Aerosol Particles ◽

Anthropogenic Sources ◽

Deposition Flux ◽

Wet Season ◽

Secondary Aerosol ◽

Aerosol Emission ◽

Amazon Rain Forest ◽

Particle Fluxes

Abstract. Number fluxes of particles with diameter larger than 10 nm were measured with the eddy covariance method over the Amazon rain forest during the wet season as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) campaign 2008. The primary goal was to investigate whether sources or sinks dominate the aerosol number flux in the tropical rain forest-atmosphere system. During the measurement campaign, from 12 March to 18 May, 60% of the particle fluxes pointed downward, which is a similar fraction to what has been observed over boreal forests. The particle transfer velocity vt increased with increasing friction velocity and the relation is described by the equation vt=2.4×10−3·u∗ where u∗ is the friction velocity. Upward particle fluxes often appeared in the morning hours and seem to a large extent to be an effect of entrainment fluxes into a growing mixed layer rather than primary aerosol emission. In general, primary aerosol emission had a limited impact on the total aerosol number population in this study, possibly because the measured particle number fluxes reflect mostly particles less than approximately 200 nm. The net deposition flux prevailed even in the absolute cleanest atmospheric conditions during the campaign and therefore cannot be explained only by deposition of anthropogenic particles. It seems that a significant contribution of secondary aerosol particles to the aerosol population is the most reasonable explanation for the net downward flux. This is an indication that secondary aerosol particles may dominate the aerosol number population in the Amazon boundary layer and that the contribution of primary aerosol particles may be low in terms of numbers. However, aerosol flux measurements should be repeated in a more remote area of the Amazon with less influence from anthropogenic sources before any final conclusions may be drawn.

Download Full-text

A comparison of dry and wet season aerosol number fluxes over the Amazon rain forest

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-3063-2010 ◽

2010 ◽

Vol 10 (6) ◽

pp. 3063-3079 ◽

Cited By ~ 16

Author(s):

L. Ahlm ◽

E. D. Nilsson ◽

R. Krejci ◽

E. M. M&aring;rtensson ◽

M. Vogt ◽

...

Keyword(s):

Rain Forest ◽

Particle Flux ◽

Dry Season ◽

Deposition Flux ◽

Wet Season ◽

Transfer Velocity ◽

Particle Transfer ◽

Amazon Rain Forest ◽

Stable Conditions ◽

Particle Fluxes

Abstract. Vertical number fluxes of aerosol particles and vertical fluxes of CO2 were measured with the eddy covariance method at the top of a 53 m high tower in the Amazon rain forest as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment. The observed aerosol number fluxes included particles with sizes down to 10 nm in diameter. The measurements were carried out during the wet and dry season in 2008. In this study focus is on the dry season aerosol fluxes, with significant influence from biomass burning, and these are compared with aerosol fluxes measured during the wet season. Net particle deposition fluxes dominated in daytime in both seasons and the deposition flux was considerably larger in the dry season due to the much higher dry season particle concentration. The particle transfer velocity increased linearly with increasing friction velocity in both seasons. The difference in transfer velocity between the two seasons was small, indicating that the seasonal change in aerosol number size distribution is not enough for causing any significant change in deposition velocity. In general, particle transfer velocities in this study are low compared to studies over boreal forests. The reasons are probably the high percentage of accumulation mode particles and the low percentage of nucleation mode particles in the Amazon boundary layer, both in the dry and wet season, and low wind speeds in the tropics compared to the midlatitudes. In the dry season, nocturnal particle fluxes behaved very similar to the nocturnal CO2 fluxes. Throughout the night, the measured particle flux at the top of the tower was close to zero, but early in the morning there was an upward particle flux peak that is not likely a result of entrainment or local pollution. It is possible that these morning upward particle fluxes are associated with emission of primary biogenic particles from the rain forest. Emitted particles may be stored within the canopy during stable conditions at nighttime, similarly to CO2, and being released from the canopy when conditions become more turbulent in the morning.

Download Full-text