| Abstract |
This study investigates the role of atmospheric deposition of iron (Fe) and watersoluble
organic nitrogen (WSON) in the Eastern Mediterranean. Of particular interest
are the inputs of elements such as N, P and trace elements such as Fe, which are
essential for the biological growth of oceanic biota.
Iron speciation was studied in rainwater and dry deposition samples, while watersoluble
organic nitrogen was studied only in rainwater samples collected at two
locations in the E. Mediterranean, Heraklion and Finokalia, a remote and an urban
area respectively on the island of Crete – Greece during 03/2007 to 11/2013.
Fe(II)(aq) and Fe(III)(aq) concentration were determined using a modification of the
ferrozine colorimetric method, while Particulate Fe was determined using ICP-MS.
Fe(II) and Fe(III) concentrations range from 0.02 to 1.90 μΜ (average 0.16 μΜ and
VWM 0.11 μΜ) and from 0.001 to 0.45 μΜ (average 0.07 μΜ and VWM 0.06 μΜ)
respectively, while Total Fe range from 0.13 to 498.14 μΜ (average 21.20 μΜ and
VWM 9.02 μΜ). Of particulate interest is the iron solubility which range from 33.1%
for pH between 4 and 5 (polluted rainwater) to 0.3% for pH close to 8 (Sahara dust
episodes), indicating that Fe solubility, and therefore Fe bioavailability to ecosystems,
is enhanced in the presence of acid species.
WSON determined indirectly, using the analyzer of Total Organic Carbon (TOC-VCSH
Analayzer) which is coupling with a measurement unit of Total Nitrogen (ΤΝΜ-
1). WSON concendration for Heraklion and Finokalia, range from 0 to 198.6 μΜ
(average 33.9 μΜ and VWM 23.70 μΜ) and from 0 to 156.5 μΜ (average 25.0 μΜ
and VWM 17.31 μΜ) respectively. The average contribution of WSON to total watersoluble
nitrogen was 37.3% for Heraklion and 27.4% for Finokalia.
Both Fe and organic nitrogen show significant seasonal variation, with higher
values being observed during spring and autumm, when the dust events from Africa
are extremely vigorous. This is because dust events are the main source of Fe (mainly
soil origin) and materials of natural origin such as micro-organisms and other
nitrogenous organic compounds are associated with dust (mainly biogenic origin).
|
Ειδοχαρακτηρισμός σιδήρου και αζώτου στην υγρή και ξηρή εναπόθεση στην ανατολική Μεσόγειο
