『Abstract
The results of several recent studies challenge the reigning
paradigm that continental soil dust provides the only significant
atmospheric source of dissolved iron to the surface ocean. This
evidence includes correlations between the operational solubility
of aerosol iron and atmospheric loadings of black carbon and aluminum-normalized
vanadium and nickel, each of which are associated with emissions
from the combustion of fossil fuel oil. These observations suggest
that the relative solubility of aerosol iron, hence the eolian
flux of soluble iron to the surface ocean, may be significantly
impacted by anthropogenic oil combustion products. Using recent
field data from the Bermuda region, we have developed an empirical
method to estimate the solubility of aerosol iron using bulk aerosol
concentrations of Fe, V and Al. We apply this method to a large
body of published data from the AEROCE program for North Atlantic
island sites on Tenerife, Barbados, Bermuda and Ireland, where
the relative proportions of anthropogenic aerosols range from
minor to major, respectively. Our aerosol iron solubility estimates
suggest that anthropogenic emissions contribute approximately
70% and 85% of the annual dry deposition of soluble iron to the
surface ocean near Bermuda and Ireland, respectively, implying
that human activities have profoundly affected the iron budget
of the North Atlantic region. The annual mean dry deposition of
soluble iron at Barbados and Izana is dominated by soil dust.
The anthropogenic contribution at these two sites ranges from
12% to 30% and is highly dependent on the soil dust solubility
of Fe employed in the model. The low end (〜12%) estimate appears
to be more representative of these high-dust sites.』
1. Introduction
2. Data sources
3. Background
3.1. Fractional solubility of aerosol iron: definitions and
protocols
3.2. Fractional solubility of aerosol iron over the Sargasso
Sea
3.3. Association of soluble aerosol iron with oil combustion
emissions: evidence from vanadium and nickel
3.4. Empirical relationship between %FeS
and V/Al
3.5. Application to the wider North Atlantic region: assumptions
and limitations
4. Results
4.1. Background: the time-series samples and data
4.2. AEROCE sites: times-series of aerosol Fe, V/Al and estimated
aerosol Fe solubility
4.3. AEROCE sites: estimated dry deposition fluxes of total and
soluble Fe
5. Discussion and implications
5.1. Apportionment of soluble Fe deposition between soil
dust and anthropogenic aerosols
5.2. Comparison of estimated and measured values of aerosol iron
solubility
6. Conclusions
Acknowledgments
References