Abstract |
Atmospheric deposition is one of the most important sources of nutrients,
especially in oligotrophic areas, such as the Mediterranean Sea. Τhe deposition
of elements such as nitrogen (N), phosphorus (P) and iron (Fe), is of particular
interest for the environment as these elements are necessary for the development
of oceanic flora and fauna. As a result of this, it has been found that atmospheric
deposition of trace elements can be an important factor that affects the
productivity of oligotrophic seas, such as the Mediterranean Sea and especially
its Eastern basin, which has been shown to have a limited amount of P.
In order to observe the temporal variation of atmospheric soluble
phosphorus deposition, measurements of total soluble phosphorus (TDP) and
soluble inorganic phosphorus (DIP) were performed on samples of wet and dry
deposition through spectrophotometric determination. The results enabled also
the determination of the percentage contribution of soluble organic phosphorus
(DOP) to TDP, which has been shown to be of importance for the bioavailabilit y
of the element to the ecosystems and consequently for the productivity of the
Mediterranean Sea. The sampling took place at Finokalia (Prefecture of Lasithi,
Crete), a remote coastal area a nd in Heraklion (Crete), a large urban center in the
Eastern Mediterranean Basin.
It is noticeable that the analysis of the results has attributed a very large
fraction of TDP to DOP during this specific study, suggesting that the main forms
of phosphorus are organic. Therefore, unknown sources of organic phosphorus
possibly exist, as suggested in a previous study, which supports the biological
origin of the majority of phosphorus.
In the present study, the factors that can affect the monthly variation of
the concentrations and the fluxes of phosphorus in each region were discussed.
Furthermore, of particular interest was the observation that the solubility of
phosphorus increases with decreasing on rain water pH.
Finally, the mechanisms of deposition of DIP are studied and the dominant
deposition mechanism, which is dry deposition, is presented. As for the deposition
of DOP, both deposition mechanisms (wet and dry) are equally important. Also,
was presented the similar spatial variability in two sampling areas (Heraklion and
Finokalia), which is prooved by data comparison.
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