Abstrak. Inverse Distance Weighting (IDW) adalah salah satu metode interpolasi untuk menaksir suatu nilai pada lokasi yang tidak tersampel berdasarkan data disekitarnya. Metode ini sering digunakan dalam kegiatan eksplorasi karena dalam proses perhitungannya lebih sederhana dan mudah difahami. Penelitian ini bertujuan untuk memetakan sebaran bijih limonit secara lateral dan potensi sumberdaya nikel, dengan menggunakan metode IDW untuk menaksir kadar Ni dan ketebalan zona mineralisasi. Penelitian ini dilakukan berdasarkan data hasil pengebeboran prospeksi sebanyak 60 titik bor. Parameter power yang digunakan dalam proses interpolasi adalah 1, 2, 3, 4 dan 5. Untuk memilih nilai power yang terbaik digunakan parameter Root Mean Square Error (RMSE) yang diperoleh dari prosedur cross validation. Berdasarkan nilai RMSE terkecil diperoleh bahwa metode IDW dengan power 1 adalah yang terbaik. Dengan asumsi nilai cut-off grade adalah 1,2% Ni dan densitas limonit 1,6 ton/m³, hasil estimasi sumberdaya pada zona limonit adalah 151,7 juta ton bijih dengan kadar rata-rata 1,45% Ni atau setara dengan ± 2,2 juta ton logam nikel. Peta sebaran bijih menunjukkan bahwa potensi tambahan sumberdaya masih terbuka kearah selatan dan barat laut dari daerah penelitian.
The purpose of this study was to determine the Erosion hazard, to look for conservation of bio - mechanical techniques are appropriate . Research methods with overlies topographic maps, soil maps, land use maps, to obtain a Land Unit Map. Determined soil physical properties (texture, structure, permeability) and chemical properties of soil (soil organic matter), slope, slope length, broad of land unit, crops factor and value conservation factors that have been there for Land Unit. Each land unit is determined the amount of land erosion and erosion hazard level. Erosion hazard level is determined based on soil erosion, and soil depth. Erosion hazzard level is used to determine the bio-mechanical conservation, according Hardjowigeno and Sukmana (1995). The results showed that the highest erosion hazard level with an area of 12.947 ha is classified weight (Land unit 15A), and the classification of an area of 14.665 ha is clssified moderately (Land unit 6A). Soil conservation is done in areas with highest erosion hazard level by making individual terraces and “kerandang” planted as a cover crops.
Clay mineral is known as a good adsorbent on metal ions. This study aimed to determine Bontang clay adsorption capacity on Cu(II) and Mn[II] heavy metal ions contained in acid mine drainage. In this study, Bontang clay was calcined at 600-700 ºC and characterized by Fourier Transform Infrared Analyzer (FTIR), X-Ray Diffraction (XRD), and Surface Area Analyzer (SAA). FTIR characterization shows the presence of active groups of silanol (Si-OH) and aluminol (Al-OH) act as heavy metal adsorbent. XRD characterization demonstrated the presence of montmorillonite, kaolinite, illite and quartz. SAA characterization revealed that after activation was greater than before activation, in amount of 34.793 m2/g for pre-activation and 49.859 m2/g for post activation. Calcination of Bontang clay improved the adsorptive capability of Cu[II] and Mn[II]. Maximum adsorption percentage of Cu[II] on raw and calcined Bontang clay were 96,53% and 94.67% at initial concentration of 10 mg/dm3 and they were 74.91% and 32.82 % for Mn[II. They decreased to 7.2% and 8.3% for raw and calcined Cu[II] and 4.3% and 6.8% for Mn[II] at initial concentration of 5,000 mg/dm3. The higher adsorption percentage is for lower concentrations for both Cu[II and Mn[II].
Cobalt is a metallic element that can be found in laterite deposits with varying concentration in each lithology zone. Objective of this study was to compare the performance of the ordinary cokriging (OCK) and inverse distance weighting (IDW) in mapping the cobalt content of laterite deposits. Cross variogram analysis used the covariable Ni and Fe, and the selection of the variogram model used the residual sum of square parameter. The IDW interpolation process uses power 1 and 2. The determination of the best method is based on the mean error parameter, and the root mean square error. Meanwhile, to determine the accuracy of the OCK estimation results, the root mean square standardized prediction error is used. The study indicates that the performance of the OCK interpolation is better than IDW, with overestimated predictions. The results of OCK interpolation showed that the distribution of 0.1-0.18% cobalt spread in the northern part and narrowed in the southern part of the study area.
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