X‑ray Spectroscopic Quantification of Phosphorus Transformation in Saharan Dust during Trans-Atlantic Dust Transport

Saharan dust is an important phosphorus (P) supply to remote and oligotrophic parts of the oceans and American lowland tropical rainforests. Phosphorus speciation in aeolian dust ultimately controls the release and bioavailability of P after dust deposition, but the speciation in Saharan dust and it...

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Bibliographic Details
Published in:Environmental science & technology 2021-09, Vol.55 (18), p.12694-12703
Main Authors: Dam, Than T. N, Angert, Alon, Krom, Michael D, Bigio, Laura, Hu, Yongfeng, Beyer, Kevin A, Mayol-Bracero, Olga L, Santos-Figueroa, Gilmarie, Pio, Casimiro, Zhu, Mengqiang
Format: Article
Language:English
Subjects:
Acidification
Aluminum
Apatite
Bioavailability
Biogeochemical Cycling
Control stability
Dust
ENVIRONMENTAL SCIENCES
Eolian dust
Oceans
Particle sorting
Phosphorus
Rainforests
Saharan dust
Solubility
Speciation
Spectroscopy
Trans-Atlantic dust transport
X ray absorption
XANES spectroscopy
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Summary:Saharan dust is an important phosphorus (P) supply to remote and oligotrophic parts of the oceans and American lowland tropical rainforests. Phosphorus speciation in aeolian dust ultimately controls the release and bioavailability of P after dust deposition, but the speciation in Saharan dust and its change during the trans-Atlantic transport remains unclear. Using P K-edge X-ray absorption near edge structure (XANES) spectroscopy, we showed that with increasing dust traveling distance from the Sahara Desert to Cape Verde and to Puerto Rico, about 570 and 4000 km, respectively, the proportion of Ca-bound P (Ca-P), including both apatite and non-apatite forms, decreased from 68–73% to 50–71% and to 21–37%. The changes were accompanied by increased iron/aluminum-bound P proportion from 14–25% to 23–46% and to 44–73%, correspondingly. Laboratory simulation experiments suggest that the changes in P speciation can be ascribed to increasing degrees of particle sorting and atmospheric acidification during dust transport. The presence of relatively soluble non-apatite Ca-P in the Cape Verde dust but not in the Puerto Rico dust is consistent with the higher P water solubility of the former than the latter. Our findings provide insights into the controls of atmospheric processes on P speciation, solubility, and stability in Saharan dust.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.1c01573