Magnetic Parameters as Pollution Indicators of Lagoon and Stream Sediments from Chascomús 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 International Association of Geomagnetism and Aeronomy-IAGA; 2005

IAGA

Magnetic parameters as pollution indicators of lagoonand stream sediments from Chascomús area(Argentina)A. Sinito (1), M. Chaparro (1), C. Gogorza (1), J. Lirio (2), H. Nuñez (2)(1) CONICET and IFAS, Universidad Nacional del Centro, Argentina, (2) Instituto AntárticoArgentino (asinito@exa.unicen.edu.ar / Fax: +54 2293-444433 / Phone: +54 2293-444432)Magnetic properties of lagoon and stream sediments from Chascomús area (situatedon 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 studiedin the present work.Different magnetic measurements were carried out, studies of magnetic susceptibility,anhysteric remanent magnetisation (ARM), isothermal remanent magnetisationof acquisition (IRM) and demagnetisation by alternating field. The following magneticparameters were calculated: volumetric and specific susceptibility (, ), FD %frequency-dependence, ARM, anhysteric susceptibility (ARM), ARM/-ratio, SaturationIRM (SIRM), S-ratio, remanent coercivity, and several related curves.The different magnetic parameters and chemical measurements were correlated in orderto investigate the goodness of magnetic parameters as pollution indicators, obtainingthe best results for feature-dependent magnetic parameters. Coercivity of remanencecorrelates very well with chemical variables, showing correlations at high levelof significance up to 0.9094, and the ARM/-ratio also shows very good correlations(up to 0.8376).Some results and advantages of using a new experimental method in order to discriminatehard and soft magnetic phases are shown. This method uses alternately backfieldisothermal remanent magnetisation and demagnetisation by alternating field. From theexperimental separation, the presence of hard magnetic phases in some samples wasconfirmed. Furthermore, it is possible to estimate the SIRM for each phase, its contributionto 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 remanentcoercivities of individual phases.1