INVESTIGADORES
OSELLA Ana Maria
artículos
Título:
Distortion pattern recognition in electric and electromagnetic responses of hydrocarbon contaminated soils
Autor/es:
MARTINELLI, PATRICIA; ROBLEDO, FABIANA; OSELLA, A.,; DE LA VEGA, MATIAS
Revista:
JOURNAL OF APPLIED GEOPHYSICS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2012 vol. 77 p. 21 - 29
ISSN:
0926-9851
Resumen:
Abstract  Here,  we  present  the  results  of  a  geophysical  survey  performed  to  characterize  a hydrocarbon contamination plume, arising from  a puncture in a master crude oil pipe in Argentina. This pipe was buried in an inhabited suburban yard with flat topography. At  the  moment  of  the  event  a  stretch  of  the  duct  was  uncovered  and  the  leaked  oil flooded  the  terrain  up  to  several  meters  around  the  puncture.  The  contamination  was produced by infiltration from the surface and also by flowing through the inner layers. The  first  steps  in  the  treatment  of  the  spill  were  to  pump  the  oil,  excavate  the  sector nearby  the  puncture  and  repair  the  pipe.  Around  one  year  later,  we  preformed  the geophysical  prospecting,  which  goal  was  to  determine  the  extent  of  the  contaminant plume, required for selecting adequate remediation strategies. We combined dual-coil, frequency  domain  electromagnetic  induction  surveys  and  2D  dipole-dipole geoelectrical  profiling.  Besides,  we  performed  Wenner  soundings  at  several  positions on the walls of the excavation, where contaminated and clean sediments were exposed. From  the  1D  inversion  of  the  electromagnetic  data  and  2D  inversions  of  the  dipole-dipole  and  Wenner  data,  we  found  that,  in  general,  the  contamination  decreased  the resistivity  of  the  affected  subsoil  volumes.  However,  three  of  the  geoelectrical  profiles exhibited  localized,  very  resistive  anomalies,  which  origin  was  not  clear. They  did  not seem to be associated to the presence of high concentrations of poorly or non-degraded hydrocarbon,  since  two  of  these  profiles  crossed  the  more  contaminated  area,  but  the other  was  located  quite  further  away.  As  an  attempt  to  identify  the  cause  of  these anomalies, we carried out a 3D numerical simulation of the effects of the pipe and the excavation  on  the  2D  dipole-dipole  images.  From  this  study,  we  could  effectively determine that they were mainly distortions generated by those structures. This allowed for providing a proper interpretation of the images of the three profiles, consistent with the  other  results.  Thus,  we  could  finally  delimit  the  impacted  zone  and  ascertain  the main features of the contaminant plume.