Sains Malaysiana 38(3): 305-311(2009)

Geoelectrical Resistivity and Ground Penetrating Radar Techniques

in the Study of Hydrocarbon-Contaminated Soil

(Teknik Keberintangan Geoelektrik dan Radar Penusukan Tanih dalam

Kajian Tanih Tercemar Hidrokarbon)

Umar Hamzah*& Abdul Rahim Samsudin

Program Geologi, Pusat Pengajian Sains Sekitaran dan Sumber Alam

Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor

Mohd Azmi Ismail

Agensi Angkasa Negara (MOSTI), Kementerian Sains Teknologi

Aras 5, Blok 2, Menara PjH, Presint 2

62100 Putrajaya, Malaysia

Received: 7 August 2008 / Accepted: 13 October 2008

ABSTRACT

Geophysical surveys in particular Ground Penetrating rRdar (GPR), geolectrical Resistivity Tomography (ERT) and Vertical Resistivity Probe (VRP) were used in mapping the subsurface geological structures and groundwater contaminants at Sungai Kandis, Klang to identify the approximate boundaries of contaminant plumes and to provide stratigraphic information at this site. The study area was formerly an illegal dumping site of hydrocarbon and toxic waste. A good correlation exists between GPR signatures, ERT layers, vertical resistivity probe and the contaminated soil. The presence of contaminant plumes as well as the water table are also observed in the GPR and ERT sections at depths approximately of 0.5 to 1m. In this study, a total of 16 GPR traverses and 10 ERT lines with lengths from 30 to 100m were established. VRP measurements were conducted in 14 shallow boreholes with a maximum depth of about 1m. The VRP results show high apparent resistivity values ranging from 200 to 10000 Ωm associated with an oil contaminated layer. The presence of this layer was also detected in the 2D resistivity sections as a thin band of high resistivity values ranging from 60 to 200 Ωm. In the GPR section, the oil contaminated layer exhibits discontinuous, subparallel and chaotic high amplitude reflection patterns.

Keywords: Contamination; groundwater; radar; resistivity; soil

ABSTRAK

Survei geofizik khususnya radar penusukan tanih (RPT), tomografi keberintangan geoelektrik (TKE) dan prob keberintangan menegak (PKM) telah digunakan dalam pemetaan struktur geologi subpermukaan dan pencemaran air tanah di Sungai Kandis,, Klang untuk mengenalpasti sempadan anggaran plum tercemar dan juga untuk menyediakan maklumat stratigrafi di tapak kajian ini. Kawasan kajian adalah merupakan bekas tapak pembuangan sisa hidrokarbon dan toksik secara haram. Satu korelasi yang baik telah diperolehi mengaitkan maklumat RPT, TKE, PKM dengan tanih yang tercemar. Kehadiran plum tercemar dan juga aras air tanah dapat dicerap dalam keratan rentas RPT dan TKE pada kedalaman sekitar 0.5 hingga 1.0m. Pengukuran telah dilakukan pada 16 garis rentasan RPT dan 10 garis rentasan TKE  dengan panjang garis rentasan adalah 30m hingga 100m. Pengukuran PKM telah dijalankan dalam 14 lubang gerudi cetek pada kedalaman maksimum 1m. Hasil PKM menunjukkan nilai keberintangan ketara yang besar berjulat 200 hingga 1000 Ωm berasosiasi dengan lapisan tercemar. Lapisan tersebut juga dapat dikesan dalam keratan rentas keberintangan 2D sebagai satu jalur keberintangan tinggi yang nipis bernilai 60 hingga 200 Ωm. Dalam keratan rentas RPT, lapisan tercemar dengan minyak mempunyai ciri-ciri pantulan berpola terputus-putus, subselari, bercelaru dan beramplitud tinggi.

Kata kunci: Air tanah; keberintangan, pencemaran; radar; tanih

REFERENCES

Atekwana, E.A., Sauck, W.A. & Werkema Jr, D.D. 2000. Investigations of geoelectrical signatures at a hydrocarbon contaminated site. Journal of Applied Geophysics 44:167-180.

Barker, R.D. 1999. Surface and borehole geophysics. In Water resource of the hard rock aquifer in Arid and Semi-arid Zone. Edited by Lloyd. Studies and reports in hydrogeology 58, Paris UNESCO.

Benson, A.K. & Mustoe, N.B. 1996. DC resistivity, GPR and soil-water quality data combined to asses hydrocarbon contamination: A case study. Environmental Geosciences 3:165-175.

Daniels, J.J., Roberts, R.L. & Vendl, M.A. 1995. GPR for the detection of liquid contamination. Journal of Applied Geophysics 32: 195-207.

Griffith , D.H., Turnbull, J. &  Olayinka, A.I. 1990. Two-dimensional resistivity mapping with a computer controlled array. First Break 8:121-129.

Kim C., Daniels, J.J., Guy, E.D., Radzevicius, S.J. & Holt, J. 2000. Residual hydrocarbons in a water-saturated medium: A detection strategy using ground penetrating radar. Environmental Geosciences 7(4): 169-174.

Koefoed, O. 1979. Geosounding principles 1: Resistivity Sounding measurements. Amsterdam: Elsevier Science Publishing Co.

Loke, M.H. & Barker, R.D. 1996. Rapid least-squares inversion of apparent resistivity pseudosection by a quasi – Newton method. Geophysical prospecting 44: 131-152.

Mazac, O., Benes, L., Landa, I. & Maskova, A. 1990. Determination of the extent of oil contamination in groundwater by geoelectrical method. In Geotechnical and Environmental Geophysics Vol. II. 107-216, edited by Ward, S.H.

Olhoeft, G.R. 1992. Geophysical detection of hydrocarbon and organic chemical contamination. Proc. of SAGEEP. 587-595.

Sauck, W.A. 2000. A model for the resistivity structure of LNAPL plumes and their environs in sandy sediments. Journal of Applied Geophysics 44:151-165.

*Corresponding author; email: umar@ukm.my