A MULTIANNUAL EXPERIMENT ON TROPOSPHERIC AEROSOLS AT TERRANOVA BAY (ANTARCTICA) : ROLE OF PIXE ANALYSIS AND RELATED TECHNIQUES

In the framework of a multiannual research programme three summer sampling campaigns (1990/1991, 1993/1994, 1994/1995) were undertaken at a coastal site (lat. 72°42′43″ S, long. 164°06′58″ E) with a 12 h time resolution. Important topics of interest are associated with the roles of natural aerosols in the climatic system and biogeochemical cycles, as well as with aerosol transport, origin and interactions. Despite low concentrations, three basic techniques (a specially designed “inertial impactor for Antartica” (IIA); PIXE analysis; and multivariate statistical principal components analysis (PCA)) allowed (1990/1991 data) identification of two principal components (PCs) in the coarse fraction. “Non-sea-salt sulphur” and “sea-salt” aerosol dominated respectively the fine and coarse aerosol fractions. The 1993/1994 data are much more abundant (198 double samples) and the PIXE sensitivity was higher (systematic detection of Na and Mg). Preliminary results for the fine fraction, based on Na, Mg, Al, S, Ca and Fe, show the existence of three major PCs (interpreted as “n.s.s. sulphur”, “sea-salt” and “crustal”), each element being highly and significantly correlated to a particular PC. The addition of K does not change the main properties of the PCs and K is associated with both PC 2 and PC 3. Strong Cl depletion is observed. S, Na and Al are convenient tracers for obtaining continuous PC time distributions. A strong increase in S concentration is observed during the sampling period. Some short “episodes” are observed in all time distributions, possibly associated with aerosol transport phenomena. The 1993/1994 data and the present performance of IIA indicate that systematic work based on PIXE is now possible, despite the difficult Antarctic conditions.