HR: 17:35h
AN: GP24A-06 INVITED     [Abstracts]
TI: Pollution Studies on Soils and Stream Sediments From Argentina Using Magnetic Techniques
AU: * Sinito, A M
EM: asinito@exa.unicen.edu.ar
AF: Universidad Nacional del Centro -CONICET, Pinto 399, Tandil, 7000, Argentina
AB: The number of studies of contamination and magnetic proxies for environmental pollution in developed countries increased gradually since the 80s. In South American countries pollution studies are reduced in number; particularly in Argentina, studies on magnetic proxies are scarce and have been carried out since few years ago by the author and collaborators. This review deals with studies of magnetic proxies for pollution conducted in soils, lagoon and stream sediments from three districts (La Plata, Chascomús and Tandil) of the most densely populated province, Buenos Aires. Stream and lagoon sediments were studied in La Plata and Chascomús. In La Plata a higher concentration of magnetic minerals and a clear trend to finer grain size is observed in the top of the sequence of the most polluted streams. These results suggest an extra contribution of anthropogenic materials, possibly related to significant contribution of pollutants. The heavy metals concentration and some magnetic parameters show a good correlation. Longitudinal and vertical behaviour of the most polluted stream sediments was studied. According to the magnetic parameters and the content of heavy metals two distinctive groups are identified. The vertical distribution of sediments reveals a recent anthropogenic influence, possibly corresponding to the last 20-40 years. The magnetic parameters dependent on magnetic size grain and characteristics are more significant than those dependent on magnetic concentration for description of longitudinal and vertical distribution of present heavy metals. In Chascomús lagoon sediments, magnetic parameters and chemical determinations were correlated; the best results were obtained for parameters depending on magnetic characteristics, which show distinctive points and wide areas affected by pollution. This magnetic inference is supported by high contents of heavy metals, especially lead and zinc. Influence of pollution was investigated in Tandil and La Plata soils, revealing magnetic enhancement and presence of pollutants only in Tandil, where the main magnetic carriers are SD/PSD ferrimagnetic oxides in industrial areas (concentration about 0.1%) and SD magnetite with contribution of SP grains in natural areas (concentration about 0.01%). On the other hand, a magnetic and chemical distinction between unpolluted and polluted soils was not obtained in La Plata. PSD magnetite is the main magnetic carrier according to the analyses of different magnetic parameters. The low values of concentration-related magnetic parameters suggest lack of pollution in these soils, despite some neighboring streams are contaminated. Probably it is so, because the main pollution input is via liquid effluents or the distances to the sources are too far for atmospheric contamination.
DE: 1512 Environmental magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly