Assessment Of The Protective Capacity Of Vadoze Zone Over Aquifer Systems Using Secondary Geoelectrical Parameters: A Case Study Of Kaltungo Area North East, Nigeria

An assessment of the protective capacity of the vadose zone overlying the aquifer systems in the Kaltungo area was carried out to determine its influence on groundwater quality. Applying the schlumberger array with a maximum electrode spread AB/2 = 100m through VES, thirty water well points were surveyed using Omega terrameter (PIOSO1) resistivity meter. The field data was first subjected to manual interpretation through curve marching and then digitized modeled curves using computer software. The interpreted data revealed that the area is characterized by eleven different curve types representing three to five geo electrical layers. In order to assess the protective capacity of the vadoze zone over the aquifer systems, the longitudinal conductance (S) and transverse resistance (T) (secondary geoelectric parameters) were computed from the primary data using the Dar Zarouk formula. The values of S obtained range from 0.0018 to 0.4056 ohms with a mean value of 0.0135 ohms while the values of T range from 0.55 ohms to 1195.68 ohms with a mean value of 39.84 ohms. The values of S and T obtained reveal that 90% of probed points has poor protective capacity, 10 % has moderate protective capacity and 83 % has high transmissivity, 17 % has intermediate transmissivity. The T and S values are skewed towards poorly protective capacity thus making groundwater in the area highly vulnerable to contamination from the surface. To achieve good groundwater quality in the area, proper completion of newly constructed wells should install protective casing through the entire vadose zone.

Analisis Tingkat Kerentanan Airtanah Pada Rencana Pertambangan Batubara Di Barito Timur, Kalimantan Tengah

Undang-Undang Nomor 32 Tahun 2009 mewajibkan setiap perusahaan pertambangan di Indonesia untuk melakukan kegiatan perlindungan dan pengelolaan pada lingkungan hidup. Salah satunya adalah kegiatan perlindungan dan pengelolaan terhadap pencemaran airtanah akibat aktivitas pertambangan. Analisis tingkat kerentanan airtanah bertujuan untuk mengetahui zonasi batas atau tingkat ketahanan airtanah terhadap suatu pencemaran di lokasi rencana kegiatan pertambangan. Tingkat kerentanan air tanah tersebut digunakan sebagai acuan untuk menentukan lokasi sarana dan prasarana pertambangan. Metode yang digunakan dalam penelitian ini adalah metode DRASTIC. Parameter kerentanan yang digunakan dalam metode tersebut adalah kedalamanan airtanah dari permukaan (Depth to groundwater), curah hujan (Recharge), media akifer (Aquifer media), jenis tanah (Soil), Topografi, pengaruh media pada zona tak jenuh air (Impact of vadoze zone) dan konduktifitas hidrolik (Conductivity). Metode DRASTIC membagi masing-masing parameter menjadi beberapa kelas menurut rating, dan membobotkan tiap parameter tersebut berdasarkan pengaruhnya terhadap kerentanan airtanah. Hasil akhir dari penelitian ini adalah peta kerentanan airtanah dengan nilai indeks berkisar antara 82 (rendah) sampai 165 (tinggi). Dari peta tersebut dapat disimpulkan bahwa daerah yang paling rentan terletak disebelah utara lokasi penelitian, sehingga kegiatan perlindungan dan pengelolaan dapat difokuskan didaerah tersebut.

Matrix suction and diffusive transport in centrifuge models

Centrifuge modelling of the lateral spread of a conservative solute in a partly saturated fine sand has been accomplished in a 3 m radius centrifuge at simulated gravitational accelerations of 25 and 50 g. The distributions of the contaminant after 2 months, 6 months, and 1 year of prototype time were found experimentally by dissection of models. The results support the contention that centrifuge modelling does correctly recreate prototype transport phenomena, including transport due to matrix suction, in partly saturated fine sand. For the conditions modelled, it was found that all of the contaminant introduced at the soil surface became immobilized, for at least 1 year, inthe upper 2–3 m of the 6 m deep soil profile. Key words : centrifuge modelling, contaminant fate, vadoze zone, matrix suction, diffusion.