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| Titel |
Atmospheric input of N, P, Fe and trace metals to north Indian Ocean |
| VerfasserIn |
Manmohan Sarin, Bikkina Srinivas |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126163
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| Publikation (Nr.) |
 EGU/EGU2016-5850.pdf |
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| Zusammenfassung |
| The air-sea deposition of chemical constituents to the north Indian Ocean is influenced by
seasonal continental outflow during the late NE-monsoon (December-April). Our recent
studies have focused on deposition of mineral dust, nutrients (N, P and Fe) and toxic trace
metals to the Arabian Sea (ARS) and Bay of Bengal (BoB), two important limbs of the
north Indian Ocean. The chemical composition of PM2.5 in the continental outflow
to the marine atmospheric boundary layer reveals dominance of nss-SO42− (as
high as 25 μg m−3) and abundance of dust varies from 3 to 20 μg m−3. A striking
similarity in the temporal variability of total inorganic acidity (TIA = NO3− +
nss-SO42−) and fractional solubility of aerosol-Fe (FeTot: 60 – 1145 ng m−3)
provides evidence for chemical processing of mineral dust during atmospheric
transport. The enhanced solubility of Fe has implications to further increase in
the deposition of this micro-nutrient to ocean surface. The mass ratio of nutrients
(NInorg/NTot, Norg/NTot and PInorg/nss-Ca2+) also suggests further increase in their
air-sea deposition to the surface BoB. The dry-deposition flux of PInorgto BoB
varies by one order of magnitude (0.5 – 5.0 μmol-P m−2 d−1; Av: 0.02 Tg P yr−1).
Based on atmospheric deposition of P and Fe, C-fixation in BoB (∼1 Pg yr−1) is
dominated by anthropogenic sources and that in ARS (0.3 Pg yr−1) is limited by P and
Fe. This is attributed to poor fractional solubility (∼1%) of mineral dust over the
Arabian Sea. However, N-fixation by diazotrophs in the two oceanic regions is
somewhat similar (0.03 Pg yr−1). Our estimate of N-deposition (0.2 Tg yr−1) to the
northern Indian Ocean is significantly lower than the model results (∼800 – 1200
mg-N m−2 yr−1 ≈ 5.7 – 8.6 Tg yr−1 by Duce et al. (2008); ∼4.1 Tg yr−1 by
Okin et al. (2011); and ∼0.8 Tg yr−1 by Kanakidou et al. (2012). The increase
in aerosol toxicity is also evident from high enrichment factors of anthropogenic
trace metal (Pb, Cd, Cr, Cu and Mn). The enhanced solubility of anthropogenic
fractions of trace metals, relative to their dust derived component, is an important
issue for assessing factors that influence the marine ecosystem in the north Indian
Ocean.
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