AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Significant Impact of Transported African Biomass Burning on Phosphorus Deposition and Biogeochemical Cycles in the Amazon and Tropical Atlantic Ocean
Anne Barkley, Joseph M. Prospero, Natalie Mahowald, Douglas Hamilton, Kimberly Popendorf, Amanda Oehlert, Ali Pourmand, Alexandre Gatineau, Kathy Panechou-Pulcherie, Patricia Blackwelder, CASSANDRA GASTON, University of Miami
Abstract Number: 267 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Phosphorus (P) deposition from aerosols is important for bolstering primary productivity in nutrient-depleted ecosystems, leading to sequestration of atmospheric carbon dioxide. Transported Saharan dust is thought to relieve P limitation in Amazonian soil and the surface layer of the Tropical Atlantic Ocean (TAO) in boreal Spring, when Saharan dust transport is at an annual maximum. Alleviating these P limitations depends critically on the aerosol source and the P solubility, which determines how accessible P is for metabolic processes that stimulate primary production, particularly in the oceans. An important source of soluble P that is also transported to both the TAO and the Amazon Basin is biomass burning (BB) aerosol from Africa; however, this source is assumed to not be as important for relieving P limitations as African dust. We measured total and soluble P in long-range transported aerosols collected in Cayenne, French Guiana at a coastal site near the TAO and Amazon. Our measurements confirm that Saharan dust supplies P during boreal Spring, but the P solubility is only 5%. In boreal Fall when dust transport to South America is low, we measured unexpectedly high concentrations of total and soluble P, which we show are associated with transported BB from southern Africa. By extrapolating our results using a transport model, we show that African BB supplies up to half of P deposited to the Amazon. This is the first observational study to link P-rich BB from southern Africa to increased P deposition in the Amazon. Further, we show that African BB is a more important source of soluble P than dust to the TAO and may be more important for marine productivity in the TAO and oceans in the southern hemisphere, particularly in Summer and Fall.