Preliminary Results of Magnetic Measurements on Stream-Sediments from Buenos Aires province, Argentina

CHAPARRO, M.A.E.; BIDEGAIN, J.C.; SINITO, A.M.; GOGORZA, C.S.G.; JURADO, S.S.

Studia Geophysica et Geodaectia

Kluwer

Lugar: Praga (Rep. Checa); Año: 2003 vol. 47 p. 121 - 145

0039-3169

A wide urban area in the Northeast of Buenos Aires Province (Argentina) is exposed to anthropogenic influence, mainly due to industrial and urban activity. In this area two streams were chosen, Del Gato and El Pescado streams. They have similar characteristics, although the first one runs through the built-up area and the other one through a rural area; consequently, Del Gato stream has a higher input of pollutants (fluvial effluents, fly ashes, solid wastes, etc.) than El Pescado stream. Magnetic measurements and geochemical studies were carried out on five sediment cores taken out from both streams with the aim of establishing a link between concentration of ferrimagnetic materials and contents of heavy metals. In order to investigate concentration of magnetic carriers and its intrinsic features (present magnetic minerals and grain size distribution) several magnetic parameters were measured and relations between them were analyzed. The magnetic characteristics for both sites indicate the presence of magnetically soft minerals in both streams, predominantly in Del Gato stream and with the additional presence of relatively hard minerals in El Pescado stream. Besides, a higher concentration of secondary ferrimagnetic minerals was found in Del Gato stream than in El Pescado stream. Chemical studies show (in some cases) a high concentration of some heavy metals (lead, copper, zinc, nickel and iron) on the upper 22-cm. Magnetic parameters, especially anhysteric remanent magnetization and contents of some heavy metals, showed a very good correlation.