Geophysical surveys for saltwater intrusion assessment using electrical resistivity tomography and electromagnetic induction methods

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین شناسی، گروه محیط زیست، دانشکده علوم، دانشگاه گنت،شهر گنت ، بلژیک

2 زمین شناسی مهندسی، زمین شناسی، فردوسی مشهد، ایران

3 گروه اکتشاف نفت ، دانشکده مهندسی معدن، دانشگاه صنعتی سهند، تبریز ، ایران

4 مهندسی اکتشاف نفت، مهندسی معدن، دانشگاه صنعتی سهند، تبریز، ایران

چکیده

Saltwater intrusion is as an environmental hazard in coastal lines if not appropriately managed. The over-exploitation, over-population, and climate change have invited and pushed the saltwater landwards and polluted the freshwater aquifers. This research is studies the results of the implemented project at the coast of Saint Andre' located in Koksijde, Belgium, to study this phenomenon through near-surface geophysics. Two geophysical methods, including Electrical Resistivity Tomography (ERT) and Electromagnetic Induction (EMI), were used to identify the saltwater intrusion. The present study aimed to investigate the possibility of saltwater intrusion, its extension and assess the government reclamation attempts to push back the saltwater. In the inversions, the Depth of Investigation Index (DOI) and the topography effect were evaluated. The subsurface conductivity of both methods was compared. The reliability of both methods to identify the saltwater intrusion has been established; however, the ERT survey provided a more comprehensive visualization than the EMI. The saltwater intrusion was found in the first 80 meters of the coastal line with resistivity values of 1.74 to 5 Ohm.m; however, the infiltration of freshwater and the reclamation operation has stopped the further progress salinity into the dunes. Local possibilities of brackish water or clay lenses were identified with 6.25 to 25 Ohm.m resistivity values. The freshwater body was observed at distances between 120 and 220 meters of the ERT line with values between 46 and 136 Ohm.m. The results were correlated with other studies, proving the reliability of the models.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Geophysical surveys for saltwater intrusion assessment using electrical resistivity tomography and electromagnetic induction methods

نویسندگان [English]

  • Danial Mansourian 1
  • Asieh Hamidi 2
  • Esmael Makarian 3
  • Pedram Namazifard 4
  • Maryam Mirhashemi 4
1 Departments of Geology and Environment , Gent University, Gent, Belgium
2 Engineering Geology, Department of Geology, Ferdowsi University of Mashhad, Iran
3 Department of Mining Engineering, Sahand University of Technology, Tabriz, Iran
4 Petroleum Exploration, Faculty of Mining Engineering, Sahand University of Technology, Tabriz, Iran
چکیده [English]

Saltwater intrusion is as an environmental hazard in coastal lines if not appropriately managed. The over-exploitation, over-population, and climate change have invited and pushed the saltwater landwards and polluted the freshwater aquifers. This research is studies the results of the implemented project at the coast of Saint Andre' located in Koksijde, Belgium, to study this phenomenon through near-surface geophysics. Two geophysical methods, including Electrical Resistivity Tomography (ERT) and Electromagnetic Induction (EMI), were used to identify the saltwater intrusion. The present study aimed to investigate the possibility of saltwater intrusion, its extension and assess the government reclamation attempts to push back the saltwater. In the inversions, the Depth of Investigation Index (DOI) and the topography effect were evaluated. The subsurface conductivity of both methods was compared. The reliability of both methods to identify the saltwater intrusion has been established; however, the ERT survey provided a more comprehensive visualization than the EMI. The saltwater intrusion was found in the first 80 meters of the coastal line with resistivity values of 1.74 to 5 Ohm.m; however, the infiltration of freshwater and the reclamation operation has stopped the further progress salinity into the dunes. Local possibilities of brackish water or clay lenses were identified with 6.25 to 25 Ohm.m resistivity values. The freshwater body was observed at distances between 120 and 220 meters of the ERT line with values between 46 and 136 Ohm.m. The results were correlated with other studies, proving the reliability of the models.

کلیدواژه‌ها [English]

  • electrical resistivity tomography
  • electromagnetic induction
  • reclamation
  • depth of investigation index
  • brackish water