Sains  Malaysiana 37(2): 161-168(2008)

Penyiasatan Infiltrasi Bahan Larut Resap Di Sekitar Tapak Pelupusan Sampah Ampar Tenang Dengkil Dengan Kaedah Geofizik jenis keberintangan elektrik menegak

(Vertical Electrical Sounding Geophysical Technique in the Investigation of

Leachate Infiltration Around Ampar Tenang Dengkil Waste Disposal Site)

Umar Hamzah & Chia See Chieh

Program Geologi, Pusat Sains Sekitaran & Sumber Alam

Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, Malaysia

Diserahkan:  15 Jun 2007 / Diterima: 7 Ogos 2007

ABSTRAK

Satu survei jenis keberintangan elektrik menegak (VES) untuk menyiasat pergerakan bahan larut resap telah dijalankan di kawasan tapak pelupusan sampah Dengkil Selangor. Tapak pelupusan ini mempunyai keluasan sekitar 4.05 hektar. Kaedah VES yang digunakan adalah merupakan salah satu teknik survei geofizik untuk menyiasat sifat keberintangan bahan dengan kedalaman subpermukaan. Kaedah ini juga merupakan kaedah geofizik yang sering kali digunakan dalam pencarigalian air bawah tanah. Tujuan kajian ini ialah untuk menyiasat sejauh manakah air larut resap dari himpunan sampah berhampiran masuk ke dalam tanah di kawasan sekitar. Dalam teknik ini, jarak antara elektrod arus dan elektrod keupayaan ditambah secara progresif, di mana aliran arus yang melintasi elektrod keupayaan membawa sebahagian arus kembali ke permukaan selepas mencapai aras-aras yang lebih dalam. Dalam kajian ini, elektrod disusun mengikut susunatur Schlumberger dan alat ABEM SAS 300C digunakan untuk menghitung keberintangan di sekeliling tapak perlupusan sampah Dengkil. Jarak elektrod arus bermula dari 2.0 m dan dibesarkan hingga 62.3 m manakala jarak elektrod keupayaan dibesarkan dari 0.3 m hingga 3.0 m. Kawasan kajian terdiri daripada batuan lodak, lempung dan rijang dari Formasi Bukit Kenny. Dalam kajian ini, keadaan bawah permukaan telah dicirikan dan penafsiran dibuat berdasarkan maklumat litologi dari lubang gerudi yang berhampiran. Dengan menggunakan perisian RESIX, data lapangan telah ditafsirkan dan dimodelkan. Berdasarkan kajian makmal oleh pengkaji terdahulu, tanah yang dicemari oleh bahan larut resap sebanyak 20% akan memberikan bacaan keberintangan sebesar 30 Ωm manakala tanah yang tidak dicemari akan menunjukkan keberintangan sebesar lebih dari 60 Ωm. Bahan larut resap telah dikesan menjerap ke dalam bumi sehingga 10 m. Didapati bahan larut resap telah mengalir jauh daripada 120 m ke timur dan 180 m jauh ke utara dari tapak pelupusan sampah.

Kata kunci: Tapak pembuangan sampah; bahan larut lesap; survei geofizik; teknik keberintangan elektrik

ABSTRACT

A geophysical survey using vertical electrical sounding (VES) technique was carried out to investigate the extend of leachate movement into the surrounding area of the waste disposal site at Dengkil Selangor. The size of the landfill is about 4.05 hectare and it is still in active used as an open dumping area. Vertical Electrical Sounding (VES) is one of the geophysical survey techniques that can be used to investigate the changes in the electrical resistivity properties of subsurface materials. This technique is often being used in the groundwater exploration. The purpose of this survey is to study the extend of leachate infiltration into the surrounding ground of the waste disposal dumping site. In this technique, the current and the potential electrodes were increased progressively and this will increase the depth penetration of the electrical current. The Schlumberger electrode configuration was used for the data collection in the field and the ABEM SAS 300C resistivity meter was used for the resistance measurement at this landfill. The spacing of current electrodes used in this study was from 2.0 m to 62.3 m and the potential  electrodes spacing was from 0.3 m to 3.0 m. Geologically, the study area consists of siltstone, clay and chert of Kenny Hill Formation. In this study, the extend of contamination of the subsurface soil was characterized and interpreted based on resistivity and litological information from the nearest borehole. The field data was plotted and modeled by using RESIX software. Based on data analysis and laboratory results of previous researcher, areas with electrical resistivity less than 30 Ωm will be considered as leachate-contaminated zone. Zone with resistivity greater than 60 Ωm will be interpreted as leachate-free region. In this study, the leachate material was detected at 10 m depth. The leachate also has moved laterally to about 120 m towards the east and 180 m towards the north from the disposal area.

Keywords : Waste disposal site; leachate; geophysical survey; resistivity technique

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