Iron and other transition metals in Patagonian riverborne and windborne materials:

D. M. GAIERO,1,2,* J.-L. PROBST,2,3,† P. J. DEPETRIS,1 S. M. BIDART,4 AND L. LELEYTER2,5,‡

GEOCHIMICA ET COSMOCHIMICA ACTA

Elsevier

Lugar: Amsterdam; Año: 2003 p. 3603 - 3623

0016-7037

The bulk of particulate transition metals transported by Patagonian rivers shows a dominant upper crustal composition. The partitioning control of Fe by DOC appears as a key mechanism determining the phases transporting trace metals in Patagonian rivers. In opposition, trace elements found in the aeolian path have a combined crustal and anthropogenic origin. The aeolian material depicts Fe, Mn, and Al contents similar to that found in regional topsoils. However, seasonal concentrations of some metals (e.g., Pb, Cu, Zn) are much higher than expected from normal crustal weathering suggesting that pollutants occurring in Patagonia are scavenged by wind-transported soil-derived debris. Patagonian sediments (not considering cliff erosion) are supplied to the South Atlantic Ocean mainly through the atmosphere. When compared with aeolian fluxes, the low trace metal riverine fluxes are linked to the low suspended particulate load of Patagonian rivers, inasmuch most of it are thought to be retained in lakes as well as in reservoirs. Based on our estimation at the Patagonian coastline and on others evidences, the sub Antarctic South Atlantic (a high nutrient-low chlorophyll area-HNLC) could receive yearly between 2.0–4.0 mg m-2 of labile Fe. Furthermore, we estimate that about 250 mg m-2 y-1 of leachable Fe can eventually reach the nearby South Atlantic Ocean where 90% is supplied via the atmospheric pathway. The past and present volcanic activity in the southern Andes must be highlighted as another important source of Fe to the South Atlantic Ocean throughout the atmosphere. In this region, each volcanic event can contribute with labile Fe to the ocean several thousands fold the mass introduced by annual Patagonian dust fall-out.