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| Titel |
Sources, transport and deposition of iron in the global atmosphere |
| VerfasserIn |
R. Wang, Y. Balkanski, O. Boucher, L. Bopp, A. Chappell, P. Ciais, D. Hauglustaine, J. Peñuelas, S. Tao |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 11 ; Nr. 15, no. 11 (2015-06-08), S.6247-6270 |
| Datensatznummer |
250119796
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| Publikation (Nr.) |
 copernicus.org/acp-15-6247-2015.pdf |
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| Zusammenfassung |
| Atmospheric deposition of iron (Fe) plays an important role in controlling
oceanic primary productivity. However, the sources of Fe in the atmosphere
are not well understood. In particular, the combustion sources of Fe and the
subsequent deposition to the oceans have been accounted for in only few
ocean biogeochemical models of the carbon cycle. Here we used a mass-balance
method to estimate the emissions of Fe from the combustion of fossil fuels
and biomass by accounting for the Fe contents in fuel and the partitioning
of Fe during combustion. The emissions of Fe attached to aerosols from
combustion sources were estimated by particle size, and their uncertainties
were quantified by a Monte Carlo simulation. The emissions of Fe from
mineral sources were estimated using the latest soil mineralogical database
to date. As a result, the total Fe emissions from combustion averaged for
1960–2007 were estimated to be 5.3 Tg yr−1 (90% confidence of 2.3 to
12.1). Of these emissions, 1, 27 and 72% were emitted in particles
< 1 μm (PM1), 1–10 μm (PM1-10), and
> 10 μm (PM> 10), respectively, compared to a total Fe emission from
mineral dust of 41.0 Tg yr−1 in a log-normal distribution with a mass
median diameter of 2.5 μm and a geometric standard deviation of 2. For
combustion sources, different temporal trends were found in fine and
medium-to-coarse particles, with a notable increase in Fe emissions in
PM1 since 2000 due to an increase in Fe emission from motor vehicles
(from 0.008 to 0.0103 Tg yr−1 in 2000 and 2007, respectively). These
emissions have been introduced in a global 3-D transport model run at a
spatial resolution of 0.94° latitude by 1.28°
longitude to evaluate our estimation of Fe emissions. The modelled Fe
concentrations as monthly means were compared with the monthly (57 sites) or
daily (768 sites) measured concentrations at a total of 825 sampling
stations. The deviation between modelled and observed Fe concentrations
attached to aerosols at the surface was within a factor of 2 at most
sampling stations, and the deviation was within a factor of 1.5 at sampling
stations dominated by combustion sources. We analysed the relative
contribution of combustion sources to total Fe concentrations over different
regions of the world. The new mineralogical database led to a modest
improvement in the simulation relative to station data even in dust-dominated regions, but could provide useful information on the chemical
forms of Fe in dust for coupling with ocean biota models. We estimated a
total Fe deposition sink of 8.4 Tg yr−1 over global oceans, 7% of
which originated from the combustion sources. Our central estimates of Fe
emissions from fossil fuel combustion (mainly from coal) are generally
higher than those in previous studies, although they are within the
uncertainty range of our estimates. In particular, the higher than
previously estimated Fe emission from coal combustion implies a larger
atmospheric anthropogenic input of soluble Fe to the northern Atlantic and
northern Pacific Oceans, which is expected to enhance the biological carbon
pump in those regions. |
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