“…Bristow et al (2010) analyzed aerosol samples collected from the Bodélé Depression, Chad, and suggested that the amounts of Fe in some samples likely indicate the presence of ferromagnesian minerals and also reflect the presence of Fe oxides such as goethite and hematite, or Fe sulfate salts that have been detected in Saharan dust. Abouchami et al (2013), studying the geochemical characteristics of the Bodélé Depression dust source and the relation to transatlantic dust transport to the Amazon Basin, found lower Na, K, Fe, and Ca concentrations in Amazon Basin soil samples than in the Bodélé samples, suggesting that this difference is a reflection of remobilization and loss of these elements by chemical weathering under the hot, wet climate conditions in the Amazon Basin.…”
Section: Composition Of Aerosol Soluble Fractionmentioning
confidence: 99%
“…Therefore, the presence of iron-rich aerosols deposited onto the canopy is likely to at least partially counter the effects of deficiency of this micronutrient. The majority of soluble mineral nutrients in the Amazon Basin soil originated from the gradual weathering of bedrock (Abouchami et al, 2013). Thus, the full extent of the influence of Saharan dust is yet to be determined.…”
Section: Iron Availabilitymentioning
confidence: 99%
“…There have been suggestions that Saharan dust transport across the Atlantic may act as a valuable fertilizer of the Amazon rainforest, providing fundamental nutrients to the Amazon forest (Swap et al, 1992;Koren et al, 2006;Ben-Ami et al, 2010;Abouchami et al, 2013). However, little is known about the nutrient amounts reaching the Amazon, their bioavailability, and their potential effect on rainforest ecology.…”
Section: Introductionmentioning
confidence: 99%
“…Amazon lowland rainforest soils are shallow and have almost no soluble minerals; added to this, heavy rains readily leach soluble nutrients from the ground, which had been added from litter decomposition and weathered rocks (Koren et al, 2006). There are indications that Saharan desert aerosol can compensate for the poor soils of the Amazon (Gross et al, 2015) with phosphorus (P) contributing as a fertilizer to the forest (Swap et al, 1992;Okin et al, 2004;Koren, 2006;Bristow et al, 2010;Abouchami et al, 2013;Yu et al, 2015).…”
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
“…Bristow et al (2010) analyzed aerosol samples collected from the Bodélé Depression, Chad, and suggested that the amounts of Fe in some samples likely indicate the presence of ferromagnesian minerals and also reflect the presence of Fe oxides such as goethite and hematite, or Fe sulfate salts that have been detected in Saharan dust. Abouchami et al (2013), studying the geochemical characteristics of the Bodélé Depression dust source and the relation to transatlantic dust transport to the Amazon Basin, found lower Na, K, Fe, and Ca concentrations in Amazon Basin soil samples than in the Bodélé samples, suggesting that this difference is a reflection of remobilization and loss of these elements by chemical weathering under the hot, wet climate conditions in the Amazon Basin.…”
Section: Composition Of Aerosol Soluble Fractionmentioning
confidence: 99%
“…Therefore, the presence of iron-rich aerosols deposited onto the canopy is likely to at least partially counter the effects of deficiency of this micronutrient. The majority of soluble mineral nutrients in the Amazon Basin soil originated from the gradual weathering of bedrock (Abouchami et al, 2013). Thus, the full extent of the influence of Saharan dust is yet to be determined.…”
Section: Iron Availabilitymentioning
confidence: 99%
“…There have been suggestions that Saharan dust transport across the Atlantic may act as a valuable fertilizer of the Amazon rainforest, providing fundamental nutrients to the Amazon forest (Swap et al, 1992;Koren et al, 2006;Ben-Ami et al, 2010;Abouchami et al, 2013). However, little is known about the nutrient amounts reaching the Amazon, their bioavailability, and their potential effect on rainforest ecology.…”
Section: Introductionmentioning
confidence: 99%
“…Amazon lowland rainforest soils are shallow and have almost no soluble minerals; added to this, heavy rains readily leach soluble nutrients from the ground, which had been added from litter decomposition and weathered rocks (Koren et al, 2006). There are indications that Saharan desert aerosol can compensate for the poor soils of the Amazon (Gross et al, 2015) with phosphorus (P) contributing as a fertilizer to the forest (Swap et al, 1992;Okin et al, 2004;Koren, 2006;Bristow et al, 2010;Abouchami et al, 2013;Yu et al, 2015).…”
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
“…However, the regionally and biogenically dominated background state of the atmosphere is frequently perturbed by the episodic advection of 5 long-range transport (LRT) aerosols from Africa in air masses that bypass the major rain fields and, therefore, 'survive' the intense scavenging (Moran-Zuloaga et al, 2017). The frequent intrusion of LRT aerosols is a characteristic feature during the Amazonian wet season and represents a strong and important impact on the Amazonian ecosystem (e.g., Chen et al, 2009;Bristow et al, 2010;Baars et al, 2011;Abouchami et al, 2013;Yu et al, 2015;Rizzolo et al, 2016). These LRT plumes mostly comprise a complex mixture of Saharan dust, African 10 biomass burning smoke, and marine aerosols from the transatlantic air passage (e.g., Talbot et al, 1990;Swap et al, 1992;Glaser et al, 2015).…”
Section: Aerosol and Ccn Time Series For Representative Wet Season Comentioning
Size-resolved measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a full seasonal cycle (Mar 2014 -Feb 2015. In a companion part 1 paper, we presented an in-depth CCN characterization based on annually as well as seasonally averaged time intervals and discuss different para-5 metrization strategies to represent the Amazonian CCN cycling in modelling studies (M. Pöhlker et. al. 2016b).The present part 2 study analyzes the aerosol and CCN variability in original time resolution and, thus, resolves aerosol advection and transformation for the following case studies, which represent the most characteristic states of the Amazonian atmosphere: ), a mostly organic particle composition, and relatively low hygroscopicity levels (κAit = 0.12 vs. κacc = 0.18). The NP CCN efficiency spectrum shows that the CCN population is sensitive to changes in supersaturation (S) over a wide S range. Atmos. Chem. Phys. Discuss., https://doi
Decades of aerosol measurements on Barbados have yielded a detailed picture of African mineral dust transport to the Caribbean Basin that shows a strong seasonal cycle with a maximum in boreal summer and a minimum in winter. Satellite aerosol products suggest that in spring, there is a comparable transport to northeastern South America. Here we characterize the complete annual cycle of dust transport to the western Atlantic by linking the Barbados record to multiyear records of airborne particulate matter less than 10 μm diameter (PM 10 ) measured in air quality programs at Cayenne (French Guiana) and Guadeloupe. Comparisons of PM 10 at these sites with concurrent dust measurements at Barbados demonstrate that high PM 10 levels are almost entirely due to dust. Cayenne PM 10 peaks in spring in a cycle which is consistent with satellite aerosol optical depth and suggests that the Sahel is the dominant source. The persistent transport of dust during much of the year could impact a wide range of environmental processes over a broad region that extends from the southern United States to the Amazon Basin. Finally, the average 24 h PM 10 concentrations at Cayenne and Guadeloupe frequently exceed the World Health Organization air quality guideline. Thus soil dust PM 10 could be a significant, but generally unrecognized, health factor at western Atlantic sites and also in other relatively remote regions affected by long-range dust from Africa. Because dust emissions and transport are highly sensitive to climate variability, climate change in coming decades could greatly affect a wide range of biogeochemical processes and human health in this region.
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