Saharan dust in the Amazon Basin

Abstract

Saharan dust is shown to enter the Central Amazon Basin (CAB) in bursts which accompany major wet season rain systems. Low‐level horizontal convergence feeding these rain systems draws dust from plumes which have crossed the tropical Atlantic under the large‐scale circulation fields. Mass exchange of air between the surface and 4 km over the eastern Amazon basin is calculated using rawinsonde data collected during storm events. Mean concentrations of dust observed by aircraft over the western tropical Atlantic are used to calculate the amount of dust injected into the Basin. Individual storm events inject some 480,000 tons of dust into the north‐eastern Amazon Basin. Storm and dust climatology suggest that the annual importation of dust is in the order of 13 Mtons. In the north‐eastern basin, this may amount to as much as 190 kg ha−1 yr−1. Deposition of trace species, such as phosphate, associated with this dust ranges from 1‐4 kg ha−1 yr−1. Uncertainties in these estimates are not believed to be greater than ± 50% and may be as low as ± 20%. The deposition fluxes from Saharan dust are essentially identical to the CAB wet deposition fluxes from precipitation in the wet season; a result that implies that the major ionic composition of rain water in the CAB wet season may be strongly influenced by inputs of material originating on the African continent nearly 5000 km away. The total amount of Saharan dust calculated to enter the Amazon basin is 1/2 to 1/3 of that estimated to cross 60°W longitude between 10° and 25°N latitude. We conclude that part of the productivity of the Amazon rain forest is dependent upon critical trace elements contained in the soil dust originating in the Sahara/Sahel. This dependence should be reflected by expansions and contractions of the Amazon rain forest in direct relationship to expansions and contractions of the Sahara/Sahel. Turnover rates for nutrient species deposited with Saharan dust in the Amazon Basin suggest a time scale of 500 to 20,000 years. We believe the dependence of one large ecosystem upon another separated by an ocean and coupled by the atmosphere to be fundamentally important to any view of how the global system functions. Any strategy designed to preserve the Amazonian rain forest or any part thereof should equally concern itself with the inter‐relationship between the rain forest, global climate and arid zones well removed from Amazonia.

Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 2: Variability and characteristic differences under near-pristine, biomass burning, and long-range transport conditions

“…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).…”

“…The African continent is of significant importance for the Amazonian atmospheric composition as it represents a major source of desert dust and pollution aerosols (e.g., Swap et al, 1992;Andreae et al, 1994;Yu et al, 2015;Rizzolo et al, 2016). A systematic overview of the properties and relevance of LRT plume arrival in the ATTO region during the Amazonian wet season can be found in Moran-Zuloaga et al (2017).…”

Effect of various soil salinity level on the antioxidant and physiological properties of corn plant (Zea mays)

“…Furthermore Dadkhah & Griffiths (2005) reported a significant effect of such atmospheric suspended dust particle on the growth of wheat plant. Similarly, Swap et al (1992) and Koren et al (2006) reported a significant effect of desert soil on the fresh & dry weight and height of plants. Productivity of Amazon basin and efficiency of its rainforests is owing to transport, 40 million tons of dust every year (Emdad & Fardad, 2000).…”

Relationships between horizontal transport flux and vertical deposition flux during dry deposition of atmospheric dust particles

“…[2] Deposition of atmospheric dust, usually defined in the aeolian literature as a suspension of solid particles in the atmosphere with a grain size inferior to about 100 mm [Pye, 1987], has been identified as an important environmental process [Swap et al, 1992;Shinn et al, 2000]. Various theoretical and practical techniques to calculate or measure the dry aeolian deposition of dust on a surface have been proposed (for reviews, see Seinfeld and Pandis [1998], Etyemezian et al [2003], and Goossens [2005]).…”