ALBERT

Description: Cryptogamic organisms such as bryophytes and lichens cover most surfaces within tropical forests, yet their impact on the emission of biogenic volatile organic compounds is unknown. These compounds can strongly influence atmospheric oxidant levels as well as secondary organic aerosol concentrations, and forest canopy leaves have been considered the dominant source of these emissions. Here we present cuvette flux measurements, made in the Amazon rainforest between 2016–2018, and show that common bryophytes emit large quantities of highly reactive sesquiterpenoids and that widespread lichens strongly uptake atmospheric oxidation products. A spatial upscaling approach revealed that cryptogamic organisms emit sesquiterpenoids in quantities comparable to current canopy attributed estimates, and take up atmospheric oxidation products at rates comparable to hydroxyl radical chemistry. We conclude that cryptogamic organisms play an important and hitherto overlooked role in atmospheric chemistry above and within tropical rainforests.

Description: Cryptogamic organisms such as bryophytes and lichens contribute substantially to emissions of secondary organic aerosol precursors as well as to the uptake of atmospheric oxidation products over the Amazon rainforest, suggest measurements at a remote Amazon rainforest site.

Description: Bundesministerium für Bildung und Forschung (Federal Ministry of Education and Research) https://doi.org/10.13039/501100002347

Description: https://doi.org/10.17871/atto.232.15.860

Description: The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m−3), Fe(II) (16 ng m−3), Na (470 ng m−3), Ca (194 ng m−3), K (65 ng m−3), and Mg (89 ng m−3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the main source of soluble mineral nutrients.

Description: In this study, aerosol samples collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil, were investigated on a single-particle basis using a quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA). A total of 23 aerosol samples were collected in four size ranges (0.25–0.5, 0.5–1.0, 1.0–2.0, and 2.0–4.0 µm) during the wet season in 2012 at two Amazon basin sites: 10 samples in Manaus, an urban area; and 13 samples at an 80 m high tower, located at the Amazon Tall Tower Observatory (ATTO) site in the middle of the rainforest, 150 km northeast of Manaus. The aerosol particles were classified into nine particle types based on the morphology on the secondary electron images (SEIs) together with the elemental concentrations of 3162 individual particles: (i) secondary organic aerosols (SOA); (ii) ammonium sulfate (AS); (iii) SOA and AS mixtures; (iv) aged mineral dust; (v) reacted sea salts; (vi) primary biological aerosol (PBA); (vii) carbon-rich or elemental carbon (EC) particles, such as soot, tarball, and char; (viii) fly ash; and (ix) heavy metal (HM, such as Fe, Zn, Ni, and Ti)-containing particles. In submicron aerosols collected at the ATTO site, SOA and AS mixture particles were predominant (50 %–94 % in relative abundance) with SOA and ammonium sulfate comprising 73 %–100 %. In supermicron aerosols at the ATTO site, aged mineral dust and sea salts (37 %–70 %) as well as SOA and ammonium sulfate (28 %–58 %) were abundant. PBAs were observed abundantly in the PM2−4 fraction (46 %), and EC and fly ash particles were absent in all size fractions. The analysis of a bulk PM0.25−0.5 aerosol sample from the ATTO site using Raman microspectrometry and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) showed that ammonium sulfate, organics, and minerals are the major chemical species, which is consistent with the ED-EPMA results. In the submicron aerosols collected in Manaus, either SOA and ammonium sulfate (17 %–80 %) or EC particles (6 %–78 %) were dominant depending on the samples. In contrast, aged mineral dust, reacted sea salt, PBA, SOA, ammonium sulfate, and EC particles comprised most of the supermicron aerosols collected in Manaus. The SOA, ammonium sulfate, and PBAs were mostly of a biogenic origin from the rainforest, whereas the EC and HM-containing particles were of an anthropogenic origin. Based on the different contents of SOA, ammonium sulfate, and EC particles among the samples collected in Manaus, a considerable influence of the rainforest over the city was observed. Aged mineral dust and reacted sea-salt particles, including mineral dust mixed with sea salts probably during long-range transatlantic transport, were abundant in the supermicron fractions at both sites. Among the aged mineral dust and reacted sea-salt particles, sulfate-containing ones outnumbered those containing nitrates and sulfate + nitrate in the ATTO samples. In contrast, particles containing sulfate + nitrate were comparable in number to particles containing sulfate only in the Manaus samples, indicating the different sources and formation mechanisms of secondary aerosols, i.e., the predominant presence of sulfate at the ATTO site from mostly biogenic emissions and the elevated influences of nitrates from anthropogenic activities at the Manaus site.

Description: Bioaerosols are considered to play a relevant role in atmospheric processes, but their sources, properties, and spatiotemporal distribution in the atmosphere are not yet well characterized. In the Amazon Basin, primary biological aerosol particles (PBAPs) account for a large fraction of coarse particulate matter, and fungal spores are among the most abundant PBAPs in this area as well as in other vegetated continental regions. Furthermore, PBAPs could also be important ice nuclei in Amazonia. Measurement data on the release of fungal spores under natural conditions, however, are sparse. Here we present an experimental approach to analyze and quantify the spore release from fungi and other spore-producing organisms under natural and laboratory conditions. For measurements under natural conditions, the samples were kept in their natural environment and a setup was developed to estimate the spore release numbers and sizes as well as the microclimatic factors temperature and air humidity in parallel to the mesoclimatic parameters net radiation, rain, and fog occurrence. For experiments in the laboratory, we developed a cuvette to assess the particle size and number of newly released fungal spores under controlled conditions, simultaneously measuring temperature and relative humidity inside the cuvette. Both approaches were combined with bioaerosol sampling techniques to characterize the released particles using microscopic methods. For fruiting bodies of the basidiomycetous species, Rigidoporus microporus, the model species for which these techniques were tested, the highest frequency of spore release occurred in the range from 62 % to 96 % relative humidity. The results obtained for this model species reveal characteristic spore release patterns linked to environmental or experimental conditions, indicating that the moisture status of the sample may be a regulating factor, whereas temperature and light seem to play a minor role for this species. The presented approach enables systematic studies aimed at the quantification and validation of spore emission rates and inventories, which can be applied to a regional mapping of cryptogamic organisms under given environmental conditions.

Description: The intercontinental transport of aerosols from the Sahara is likely to play a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and the Amazon rainforest is iron-limited. The main aim of this study was to assess the input and potential impact of iron bioavailability from Saharan dust, namely, the soluble fraction Fe(II)/Fe(III). Seven other soluble elements that are also essential for plants were measured. Dust particles entrained in the air were collected and analyzed, but not dust deposited in rainfall as atmospheric washout. The sampling campaign was carried out at the ATTO site (Amazon Tall Tower Observatory), from March to April 2015, and samplers were placed both above and below the canopy. Mineral dust aerosol at ATTO showed peak concentrations for Fe(III) (47.6 ng m−3), Fe(II) (16.2 ng m−3), Na (470 ng m−3), Ca (194 ng m−3), K (64.7 ng m−3), and Mg (88.8 ng m−3) during the presence of dust transported from the Sahara, as determined by remote ground-based and satellite sensing data and backward trajectories. Atmospheric transport of weathered Saharan dust, followed by surface deposition, results in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust rich in soluble iron and other minerals is likely to affect both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent epiphytes, such as lichens. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence on the ecology of the forest canopy and topsoil would likely be different from that of nutrients from the weathered Amazon bedrock, which provides the main source of soluble mineral nutrients.

Description: Bioaerosols are considered to play a relevant role in atmospheric processes, but their sources, properties and spatio-temporal distribution in the atmosphere are not yet well characterized. In the Amazon Basin, primary biological aerosol particles (PBAP) account for a large fraction of coarse particulate matter, and fungal spores are among the most abundant PBAP there as well as in other vegetated continental regions. Furthermore, PBAP could also be important ice nuclei in Amazonia. Measurement data on the release of fungal spores under natural conditions are, however, sparse. Here we present an experimental approach to analyze and quantify the spore release from fungi and other spore producing organisms under natural and laboratory conditions. For measurements under natural conditions, the samples were kept in their natural environment and a setup was developed to estimate the spore release numbers and sizes together with the microclimatic factors temperature and air humidity, as well as the mesoclimatic parameters, net radiation, rain, and fog occurrence. For experiments in the laboratory, we developed a cuvette to assess the particle size and number of newly released fungal spores under controlled conditions, simultaneously measuring temperature and relative humidity inside the cuvette. Both approaches were combined with bioaerosol sampling techniques to characterize the released particles by microscopic methods. For fruiting bodies of the basidiomycetous species, Rigidoporus microporus, the model species for which these techniques were tested, the highest frequency of spore release occurred in the range of 62 and 96 % relative humidity. The results obtained for this model species reveal characteristic spore release patterns linked to environmental or experimental conditions, indicating that the moisture status of the sample may be a regulating factor, while temperature and light seem to play a minor role, at least for this species. The presented approach enables systematic studies aimed at the quantification and validation of spore emission rates and inventories, which can be applied to a regional mapping of cryptogamic organisms under given environmental conditions.

Description: In this study, aerosol samples collected at a remote site in the Amazonian rainforest and an urban site in Manaus, Brazil, were investigated on a single particle basis using a quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA). Twenty-three aerosol samples were collected in four size ranges (0.25–0.5, 0.5–1.0, 1.0–2.0, and 2.0–4.0µm) during the wet season in 2012 at two Amazon basin sites: 10 samples in Manaus, an urban area; and 13 samples at an 80-m high tower, located at the Amazon Tall Tower Observatory (ATTO) site in the middle of the rainforest, 150km northeast of Manaus. The aerosol particles were classified into nine particle types based on the morphology on the secondary electron images (SEIs) together with the elemental concentrations of 3,162 individual particles: (i) secondary organic aerosols (SOA), (ii) ammonium sulfate (AS), (iii) SOA and AS mixtures, (iv) aged mineral dust, (v) reacted sea-salts, (vi) primary biological aerosol (PBA), (vii) carbon-rich or elemental carbon (EC) particles, such as soot, tar ball, and char, (viii) fly ash, and (ix) heavy metal (HM, such as Fe, Zn, Ni, and Ti)-containing particles. In submicron aerosols collected at the ATTO site, SOA and AS mixture particles were predominant (50–94% in relative abundance) with SOA and ammonium sulfate comprising 73–100%. In supermicron aerosols at the ATTO site, aged mineral dust and sea-salts (37–70%) as well as SOA and ammonium sulfate (28–58%) were abundant. PBAs were observed abundantly in the PM2–4 fraction (46%), and EC and fly ash particles were absent in all size fractions. The analysis of a bulk PM0.25–0.5 aerosol sample from the ATTO site using Raman microspectrometry and attenuated total reflection Fourier transform infrared spectroscopy showed that ammonium sulfate, organics, and minerals are the major chemical species, which is consistent with the ED-EPMA results. In the submicron aerosols collected in Manaus, either SOA and ammonium sulfate (17–80%) or EC particles (6–78%) were dominant depending on the samples. In contrast, aged mineral dust, reacted sea-salt, PBA, SOA, ammonium sulfate, and EC particles comprised most of the supermicron aerosols collected in Manaus. The SOA, ammonium sulfate, and PBAs were mostly of a biogenic origin from the rainforest, whereas the EC and HM-containing particles were of an anthropogenic origin. Aged mineral dust and reacted sea-salt particles, including mineral dust mixed with sea-salts probably during long-range transatlantic transport, were abundant in the supermicron fractions at both sites. Among the aged mineral dust and reacted sea-salt particles, sulfate-containing ones outnumbered those containing nitrates and sulfate+nitrate in the ATTO samples. In contrast, particles containing sulfate+nitrate were comparable in number to particles containing sulfate only in the Manaus samples, indicating the different sources and formation mechanisms of secondary aerosols, i.e., the predominant presence of sulfate at the ATTO site from mostly biogenic emissions and the elevated influences of nitrates from anthropogenic activities at the Manaus site.

Description: In the Amazonian rain forest, major parts of trees and shrubs are covered by epiphytic cryptogams of great taxonomic variety, but their relevance in biosphere-atmosphere exchange, climate processes, and nutrient cycling are largely unknown. As cryptogams are poikilohydric organisms, they are physiologically active only under moist conditions. Thus, information on their water content, as well as temperature and light conditions experienced by them are essential to analyzing their impact on local, regional, and even global biogeochemical processes. In this study, we present data on the microclimatic and ecophysiological conditions of epiphytic bryo-phytes along a vertical gradient and combine these with mesoclimate data collected at the Amazon Tall Tower Observatory (ATTO) in the Amazonian rain forest between October 2014 and December 2016. While the monthly average mesoclimatic ambient light intensities above the canopy revealed only minor variations, the light intensities incident on the bryophytes showed different patterns at different heights, probably depending on individual shading by vegetation. At 1.5 m height, monthly average light intensities were similar throughout the year and individual values were extremely low, exceeding 5 µmol m−2 s−1 pho-tosynthetic photon flux density only during 8 % of the time. Temperatures showed only minor variations throughout the year with higher values and larger height-dependent differences during the dry season. Water contents of bryophytes varied depending on precipitation and air humidity. Whereas bryophytes at higher levels were affected by frequent wetting and drying events, those close to the forest floor remained wet over longer time spans during the wet seasons. Based on estimates of the potential duration of net pho-tosynthesis and dark respiration, our data suggest that water contents are decisive for overall physiological activity, and light intensities determine whether net photosynthesis or dark respiration occurs, whereas temperature variations are only of minor relevance in this environment. In general, bryophytes growing close to the forest floor are limited by light availability, while those growing in the canopy must withstand larger variations in microclimatic conditions, especially in the dry season. Measurements of CO2 gas ex-change are essential to elucidate their physiological activity patterns in greater detail.

Description: The Amazon Basin plays key role in atmospheric chemistry, biodiversity and climate change. In this study we applied nanoelectrospray (nanoESI) ultra-high-resolution mass spectrometry (UHRMS) for the analysis of the organic fraction of PM2.5 aerosol samples collected during dry and wet seasons at a site in central Amazonia receiving background air masses, biomass burning and urban pollution. Comprehensive mass spectral data evaluation methods (e.g. Kendrick mass defect, Van Krevelen diagrams, carbon oxidation state and aromaticity equivalent) were used to identify compound classes and mass distributions of the detected species. Nitrogen- and/or sulfur-containing organic species contributed up to 60 % of the total identified number of formulae. A large number of molecular formulae in organic aerosol (OA) were attributed to later-generation nitrogen- and sulfur-containing oxidation products, suggesting that OA composition is affected by biomass burning and other, potentially anthropogenic, sources. Isoprene-derived organosulfate (IEPOX-OS) was found to be the most dominant ion in most of the analysed samples and strongly followed the concentration trends of the gas-phase anthropogenic tracers confirming its mixed anthropogenic–biogenic origin. The presence of oxidised aromatic and nitro-aromatic compounds in the samples suggested a strong influence from biomass burning especially during the dry period. Aerosol samples from the dry period and under enhanced biomass burning conditions contained a large number of molecules with high carbon oxidation state and an increased number of aromatic compounds compared to that from the wet period. The results of this work demonstrate that the studied site is influenced not only by biogenic emissions from the forest but also by biomass burning and potentially other anthropogenic emissions from the neighbouring urban environments.

Description: In the Amazonian rain forest, major parts of trees and shrubs are covered by epiphytic cryptogams of great taxonomic variety, but their relevance in biosphere–atmosphere exchange, climate processes, and nutrient cycling is largely unknown. As cryptogams are poikilohydric organisms, they are physiologically active only under moist conditions. Thus, information on their water content (WC) as well as temperature and light conditions experienced by them are essential to analyze their impact on local, regional, and even global biogeochemical processes. In this study, we present data on the microclimatic conditions, including water content, temperature, and light conditions experienced by epiphytic bryophytes along a vertical gradient, and combine these with above-canopy climate data collected at the Amazon Tall Tower Observatory (ATTO) in the Amazonian rain forest between October 2014 and December 2016. While the monthly average of above-canopy light intensities revealed only minor fluctuations over the course of the year, the light intensities experienced by the bryophytes varied depending on the location within the canopy, probably caused by individual shading by vegetation. In the understory (1.5 m), monthly average light intensities were similar throughout the year, and individual values were extremely low, remaining below 3 µmol m−2 s−1 photosynthetic photon flux density more than 84 % of the time. Temperatures showed only minor variations throughout the year, with higher values and larger height-dependent differences during the dry season. The indirectly assessed water content of bryophytes varied depending on precipitation, air humidity, dew condensation, and bryophyte type. Whereas bryophytes in the canopy were affected by diel fluctuations of the relative humidity and condensation, those close to the forest floor mainly responded to rainfall patterns. In general, bryophytes growing close to the forest floor were limited by light availability, while those growing in the canopy had to withstand larger variations in microclimatic conditions, especially during the dry season. For further research in this field, these data may be combined with CO2 gas exchange measurements to investigate the role of bryophytes in various biosphere–atmosphere exchange processes, and could be a tool to understand the functioning of the epiphytic community in greater detail.