Abstract
Abstract. Total atmospheric deposition was collected on a weekly basis over 3.5 years (March 2008–October 2011) at a remote coastal site on the west coast of Corsica. Deposition time series of macro- and micronutrients (N, P, Si, Fe) and trace metals (As, Cr, Cu, Mn, Ni, V, Zn) are investigated in terms of variability and source apportionment (from fluxes of proxies for aerosol sources (Al, Ti, Ca, Na, Mg, S, Sr, K, Pb)). The highest fluxes are recorded for Si, P, and Fe for nutrients and Zn and Mn for trace metals. For the majority of elements, data show some weeks with high episodic fluxes, except for N, Cr, and V, which present the lowest variability. A total of 12 intense mineral dust deposition events are identified during the sampling period. The contribution of these events to the fluxes of Fe and Si represents 52 % and 57 % of their total fluxes, respectively, confirming the important role of these sporadic dust events in the inputs of these elements in the Mediterranean. For N and P, the contribution of these intense dust deposition events is lower and reaches 10 % and 15 %, respectively. Out of these most intense events, positive matrix factorization (PMF) was applied to our total deposition database in order to identify the main sources of nutrients and trace metals deposited. Results show that P deposition is mainly associated with anthropogenic biomass burning inputs. For N deposition, inputs associated with marine sources (maybe associated with the reaction of anthropogenic N on NaCl particles) and anthropogenic sources are quasi-similar. A good correlation is obtained between N and S fluxes, supporting a common origin associated with inorganic secondary aerosol, i.e., ammonium sulfate. For trace metals, their origin is very variable: with a large contribution of natural dust sources for Ni or Mn and conversely of anthropogenic sources for V and Zn.
Highlights
The Mediterranean Sea is a semi-enclosed basin situated at the interface among contrasted continental areas of three continents, namely southern Europe, northern Africa, and the Middle East, the coastal areas of which are heavily populated
Several authors showed that the atmospheric deposition of aerosols constitutes the main source of major nutrients, such as N, P, or Fe, to the surface open waters of the Mediterranean Sea in the summer–fall period when surface water stratification prevents inputs from deep water by vertical mixing
Even for background deposition, the source apportionment of Fe and Si is quasi-similar to Al. These results suggest that even if the positive matrix factorization (PMF) apportionment source distributes the fluxes from the four sources, in all the cases, the fluxes of Fe and Si are associated with mineral dust sources, most probably Saharan dust
Summary
The Mediterranean Sea is a semi-enclosed basin situated at the interface among contrasted continental areas of three continents, namely southern Europe, northern Africa, and the Middle East, the coastal areas of which are heavily populated. Several authors showed that the atmospheric deposition of aerosols constitutes the main source of major nutrients, such as N, P, or Fe, to the surface open waters of the Mediterranean Sea in the summer–fall period when surface water stratification prevents inputs from deep water by vertical mixing
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