INVESTIGADORES
OSELLA Ana Maria
artículos
Título:
Joint inversión of Wenner and dipole-dipole data to study a gasoline contaminated zone
Autor/es:
DE LA VEGA, MATIAS; OSELLA, ANA; LASCANO, EUGENIA
Revista:
JOURNAL OF APPLIED GEOPHYSICS
Editorial:
Elsevier
Referencias:
Año: 2003 vol. 54 p. 97 - 109
ISSN:
0926-9851
Resumen:
The goal of this work was to study a contaminated soil due to a gasoline
spill produced by fissures in a concrete purge chamber located along a gas
transmission line. A monitoring well
drilled 16 m from the chamber in the direction of the descendent topographic
slope reveled the presence of a gasoline layer of 0.5 m thick at 1.5 m depth,
floating over the water table. A second well, drilled 30 m apart from the
other, in the same direction, did not present evidences of contaminants. To
face this problem, we performed a geoelectrical prospecting, combining
dipole-dipole and Wenner arrays. First, four dipole-dipole profiles in a
direction perpendicular to the longitudinal axis were carried out. The
electrical tomographies obtained from the 2D inversion of the data shown that
the contaminant region extent is laterally about 6-8 m, and was located at a
depth between 1 to 2 m. The longitudinal extension was less than 20 m, since
the last profile located 30 m farther of chamber do not present this kind of
anomaly. To better determine the longitudinal extension, we performed a
dipole-dipole line along this direction. The inverse model confirmed that the
extension of the contaminated section was about 16 m. To complete the study of
the deeper layer, we carried out Wenner soundings. The results of the inversion
process indicated that at least up to 20 m the soil was very conductive,
associated with the presence of clays as main constituents and confining the
contaminant within this impermeable surrounding. To improve the inverse model,
we performed a joint inversion of dipole-dipole and Wenner data. Analysis of the depth of penetration showed
that it increased to 25 m and comparing the resulting model with the ones
obtained from each array separately, we concluded that the joint inversion
improves the depth reached by the prospection, maintaining the shallow lateral
resolution.