Magnetic Parameters as Pollution Indicators of Lagoon and Stream Sediments from Chascomus Area (Argentina)

SINITO, A.M.; CHAPARRO, M.A.E.; GOGORZA, C.S.G.; LIRIO, J.M.; NUÑEZ, H.

Toulouse (Francia)

Congreso; 10th. Scientific Assembly of the International Association of Geomagnetism and Aeronomy-IAGA 2005; 2005

International Association of Geomagnetism and Aeronomy

Magnetic properties of lagoon and stream sediments from Chascomus area (situated on continental lands from the Quaternary period in the NE of Buenos Aires Province) and the relevance of various magnetic parameters as giving pollution status are studied in the present work. Different magnetic measurements were carried out, studies of magnetic susceptibility, anhysteric remanent magnetisation (ARM), isothermal remanent magnetisation of acquisition (IRM) and demagnetisation by alternating field. The following magnetic parameters were calculated: volumetric and specific susceptibility (k, x, kFD % frequency-dependence, ARM, anhysteric susceptibility (kARM), kARM/k-ratio, Saturation IRM (SIRM), S-ratio, remanent coercivity, and several related curves. The different magnetic parameters and chemical measurements were correlated in order to investigate the goodness of magnetic parameters as pollution indicators, obtaining the best results for feature-dependent magnetic parameters. Coercivity of remanence correlates very well with chemical variables, showing correlations at high level of significance up to 0.9094, and the kARM/k-ratio also shows very good correlations (up to 0.8376). Some results and advantages of using a new experimental method in order to discriminate hard and soft magnetic phases are shown. This method uses alternately backfield isothermal remanent magnetisation and demagnetisation by alternating field. From the experimental separation, the presence of hard magnetic phases in some samples was confirmed. Furthermore, it is possible to estimate the SIRM for each phase, its contribution to the total SIRM, its corresponding remanent coercivity and S-ratio. Therefore, it could be possible to explain how the total remanent coercivity is biased by remanent coercivities of individual phases.