Aeolian Input

In contrast to the fluvial transport regime the aeolian transport is highly efficient for the deposition of terrigenous matter in the deep sea. 

As iron is discussed as limiting nutrient for phytoplankton productivity of distinct oceanic regions (chapter 7.3) it is important to investigate the flux, degree of solubility and the bioavailability of the introduced iron into open ocean surface water. It has long been known that sorption onto suspended particles is highly efficient in the removal of trace metals from solution (Krauskopf 1956) resulting in a decrease of dissol- 

The reason for the dissolution of solid phase iron in the photic zone is the photochemical reduction of Fe(III), with UVB (280 - 315 mn) producing most of Fe(II), followed by UVA (315 -400 mn) and visible light (400 - 700 mn) (Rijken-berg et al. 2005). As a consequence, about 10 % of atmospheric FeT reaches the ocean as dissolved iron (Duce et al. 1991 Fig. 7.1). In surface waters of the global ocean the produced Fe is subsequently reoxidized, yet, the photoreduction 

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Most of the aeolian input of trace metals is in particulate form as weathered rocks and soil. The deposition patterns on the sea surface tend to follow those of the major winds bands, with deserts being the primary source regions (Figure 11.4a). As shown in Figure 11.4b, this results in high deposition to the surfece waters immediately downwind of the arid regions of Africa, the Arabian Peninsula, Central Asia, Australia, and... 

Most of the organic matter in seawater was created in situ by marine processes and is, hence, classified as autochthonous. Organic matter of nonmarine origin is classified as allochthonous and is primarily terrestrial detritus, transported by rivers or winds. The input of organic matter from rivers is small (0.4 Pg C/y) compared to primary productivity (40 to 50 Pg C/y). The aeolian input is unknown but thought to be significant. 

If iron is a limiting micronutrient for present-day PP, it may be an important link to explain glacial-interglacial climatic cycles of the past. Martin (1990) postulated the iron hypothesis which explains decreased atmospheric CO concentrations during glacial times with increased iron deposition by aeolian input resulting in increased PP and thus increased CO -... 

Blank, M., Leinen, M. and Prospero J.M., 1985. Major Asian aeolian inputs indicated by the mineralogy of aerosols and sediments in the western North Pacific. Nature, 314 84-86. 

There is a considerable variability in lanthanide patterns in sea water, both regionally and with depth (Elderfield and Greaves 1982, De Baar et al. 1983, 1985a). With the exception of a thin surface zone which may be dominated by aeolian input, there is a general increase of light lanthanides with depth. Total lanthanides are higher in surface waters of the Atlantic Ocean, but lower in deep waters, compared with those of the Pacific (De Baar et al. 1985a). 

For the Tyrrhenian estuaries, which belong the the practically non-tidal Mediterranean Sea, it has been shown, that the overwhelming part of the fluvial heavy metal freight is sedimentated in the estuarine zone and consequently the fluvial heavy metal input to the Mediterranean Sea by Arno, Tiber and the smaller rivers remains insignificant[45]. An example from this study is shown in Figure 7. When present studies in progress for the Rhone and Ehro[46] estuaries have been completed, a relevant basis will exist to assess the relative significance of fluvial and aeolian input of ecotoxic metals into the western Mediterranean Sea. 

A comparison of atmospheric versus fluvial loading of selected dissolved trace elements to Delaware s Inland Bays indicates that on an annual basis, aeolian input provides as much as a third of the total input for Zn and at least 5% for the other metals. On shorter time scales, the relative atmospheric and fluvial loadings can vary significantly. Approximately half of the atmospheric input is directly to the surface waters of the bays, a majority of which is derived from wet deposition. The transmission of atmospheric inputs through the watershed varies among elements and for each sub-basin. Overall, atmospheric flux appears to provide quantitatively and qualitatively important inputs for a number of trace metals of ecological concern. 

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