Atmospheric P deposition to the subtropical North Atlantic: Sources, properties, and relationship to N deposition

L. M. Zamora, J. M. Prospero, Dennis A Hansell, J. M. Trapp

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing ∼880 ppm total phosphorus and ∼70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28%-44% of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2-10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 μmol m -2 d-1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21-30 and 127-132 μmol m-2 d-1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition. Key PointsDust supplies most atmospheric P but pollution is an increasingly large sourceOrganic P supplies 28-44% of soluble P in rainWe estimate historical deposition rates and variability of P, excess Redfield N

Original languageEnglish (US)
Pages (from-to)1546-1562
Number of pages17
JournalJournal of Geophysical Research C: Oceans
Volume118
Issue number3
DOIs
StatePublished - Feb 16 2013

Fingerprint

Phosphorus
phosphorus
Barbados
organic phosphorus
Nitrogen
nitrogen
Aerosols
wet deposition
aerosol
aerosols
pollution
Deposition rates
Dust
dust
Redfield ratio
Pollution
inorganic nitrogen
organic nitrogen
atmospheric deposition
seasonality

Keywords

  • aerosol
  • deposition
  • dust
  • nitrogen
  • organic
  • phosphorus

ASJC Scopus subject areas

  • Atmospheric Science
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Atmospheric P deposition to the subtropical North Atlantic : Sources, properties, and relationship to N deposition. / Zamora, L. M.; Prospero, J. M.; Hansell, Dennis A; Trapp, J. M.

In: Journal of Geophysical Research C: Oceans, Vol. 118, No. 3, 16.02.2013, p. 1546-1562.

Research output: Contribution to journalArticle

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abstract = "Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing ∼880 ppm total phosphorus and ∼70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28{\%}-44{\%} of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2-10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 μmol m -2 d-1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21-30 and 127-132 μmol m-2 d-1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition. Key PointsDust supplies most atmospheric P but pollution is an increasingly large sourceOrganic P supplies 28-44{\%} of soluble P in rainWe estimate historical deposition rates and variability of P, excess Redfield N",
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