PNNL

Abstract

The Amazon and equatorial North Atlantic Ocean (NAO) are nutrient-depleted ecosystems that rely on the deposition of long-range transported aerosols from Africa to maintain primary productivity. Using single-particle methods, we characterized the physiochemical properties of iron-containing supermicron and super-coarse mode African aerosol transported to the northeastern Amazon in boreal spring. We detected four sources of nutrient-containing particles including African dust, freshwater diatoms (FDs) from African paleolakes, primary biological aerosol particles, and biomass burning. To our knowledge, this represents the first observation of long-rang transported FDs in the Amazon. Physicochemical characterization found that FDs contained iron (Fe)-containing dust inclusions on their surfaces likely important for biogeochemical cycles. We propose that FDs, which contain 4% Fe by weight, are important vectors for increased nutrient transport to the Amazon and NAO because FDs are efficiently kept aloft due to their light density, high surface area-to-volume ratio, and large aspect ratios