Three-dimensional DC Resistivity Modeling using Galerkin Finite Element Method Composed by Tetrahedral Elements

Successful interpretation of DC resistivity data depends on the availability of a proper forward modeling scheme. In this study, a three-dimensional DC resistivity forward modeling scheme was developed using the finite element method. The finite element equations were obtained using a weakened form of the weighted-residual method called the Galerkin method. Discretization of the modeling domain was carried out by dividing it into smaller three-dimensional blocks and subdividing each block into five tetrahedral elements. A linear interpolation function was employed and elemental linear equations were set up, followed by formation of global matrix systems of equation and incorporation of proper boundary conditions. The conjugate gradient method was applied to solve the global system of equations, which in this study was proven to be more efficient than a direct solver, contributing to a 67% time reduction. Using a Wenner array configuration, comparison with theoretical calculation of the electric potential for a homogeneous model yielded a relative error of 3.66%. To confirm the applicability of this forward modeling scheme, apparent resistivity profiles for several basic three-dimensional subsurface resistivity models were compared with the analytical profiles, yielding an acceptable level of fitting

Magnetic Signatures on River Sediments and Agricultural Soils as Proxy Indicators of Anthropogenic-derived Pollution (Case Study: Cikijing River, Rancaekek, West Java)

A number of activities occur around the Cikijing River in Rancaekek area, West Java, such as industrial and domestic activities. The various activities could decrease the quality of the river and surrounding environment due to anthropogenic pollutants that might be produced. Since the Cikijing River is also used as the source of irrigation, paddy fields around the river could be also be affected. The presence of pollutants in river sediments and agricultural soils over a long period could change their magnetic properties. Magnetic susceptibility of Cikijing River sediments and soils of the paddy fields in the surrounding have been examined considering that magnetic properties could represent environmental conditions. The results show that river sediments have magnetic susceptibility (cLF) in range of 356.2-456.3 (×10-8) m3kg-1, whereas soils samples have cLF varying from 94.1 to 347.1 (×10-8) m3kg-1, suggesting domination of ferrimagnetic minerals. The cFD (%) is <4% indicating the anthropogenic origin of magnetic minerals.  Electron microscopy images show the imperfect octahedral and spherules shapes of magnetic grains that supports magnetic susceptibility analysis about the source of magnetic minerals. Elemental composition analysis reveals Fe and O’s content as main elements, including minor elements of Ca, Mg, Al. Si, Ti and C

IDENTIFIKACIJA ANTROPOGENIH MATERIJALA U SEDIMENTIMA JEZERA CIBURUY KORIŠTENJEM FIZIČKO-KEMIJSKIH SVOJSTAVA I INDEKSA ONEČIŠĆENJA

Lake Ciburuy area is highly impacted by a wide range of human activities, including residential areas, rice fields, animal husbandry, plantations, dense vehicular traffic, and various industries, leading to the accumulation of pollutants. Particulates generated by the anthropogenic activities will be carried away and settle with the eroded soil to become sediment in the lake. This could cause serious problems in the aquatic environment if there is no monitoring study. Therefore, this study aimed to identify the anthropogenic material produced by human activities using physical and chemical properties analyses and pollution index calculations. The analysis of physical properties showed that Electrical Conductivity (EC), Total Dissolved Solid (TDS), and magnetic susceptibility were within the range of 30 – 790 µS/cm, 29 – 555 mg/L, 7.310 – 3431.956 ×10-8 m3/kg, respectively. The X-ray diffraction (XRD) and the hysteresis parameter indicated that the samples contain ferrimagnetic materials, particularly magnetite with a mixture of Pseudo-Single Domain (PSD) and Multi-Domain (MD). The Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) identified the morphology of the magnetic mineral with different shapes, such as octahedral and spherule. Furthermore, the spherule shape indicated the presence of anthropogenic materials in the sample. In terms of chemical properties, this study measured the pH and Potential Toxic Elements (PTEs) in the sediments. The pH ranged from 7.2-8.9, while the PTEs showed moderate to very severe levels of contamination by Mn, Pb, Zn, Cd, and Cu, which exceeded the sediment quality standard. The PCA reveals the interconnection between physical and chemical properties, which can identify pollutants derived from anthropogenic materials, as well as indicate low, medium, and high levels of pollution in the lake area.Područje jezera Ciburuy pod velikim je utjecajem širokoga spektra ljudskih aktivnosti, uključujući stambena područja, rižina polja, stočarstvo, plantaže, gust promet vozila i razne industrije, što dovodi do nakupljanja zagađivača. Čestice nastale antropogenim aktivnostima odnijet će se i taložiti s erodiranim tlom i postati sediment u jezeru. To bi moglo stvoriti ozbiljne probleme u vodenome okolišu ako ne postoji studija praćenja. Stoga je cilj ove studije bio identificirati antropogeni materijal proizveden ljudskim aktivnostima korištenjem analize fizičkih i kemijskih svojstava i izračuna indeksa onečišćenja. Analiza fizičkih svojstava pokazala je da su električna vodljivost (EC), ukupna otopljena krutina (TDS) i magnetska osjetljivost po redu unutar raspona 30 – 790 μS/cm, 29 – 555 mg/L, 7,310 – 3431,956 ×10-8 m3/kg. Difrakcija rendgenskih zraka (XRD) i parametar histereze pokazali su da uzorci sadržavaju ferimagnetske materijale, posebno magnetit s pseudojednodomenskom (PSD) i višedomenskom (MD) mješavinom. Skenirajući elektronski mikroskop (SEM) i energetska disperzivna spektroskopija (EDS) identificirali su morfologiju magnetskoga minerala s različitim oblicima, kao što su oktaedar i sferula. Nadalje, oblik sferule upućuje na prisutnost antropogenih materijala u uzorku. Što se tiče kemijskih svojstava, ova studija mjeri pH i potencijalno toksične elemente (PTE) u sedimentima. pH je bio u rasponu 7,2 – 8,9, dok su PTE pokazivali umjerenu do vrlo jaku razinu kontaminacije Mn, Pb, Zn, Cd i Cu, što je premašilo standard kvalitete sedimenta. PCA otkriva međusobnu vezu između fizičkih i kemijskih svojstava, koja mogu identificirati zagađivače koji potječu od antropogenih materijala, kao i uputiti na niske, srednje i visoke razine onečišćenja u području jezera

IDENTIFIKACIJA ANTROPOGENIH MATERIJALA U SEDIMENTIMA JEZERA CIBURUY KORIŠTENJEM FIZIČKO-KEMIJSKIH SVOJSTAVA I INDEKSA ONEČIŠĆENJA

Lake Ciburuy area is highly impacted by a wide range of human activities, including residential areas, rice fields, animal husbandry, plantations, dense vehicular traffic, and various industries, leading to the accumulation of pollutants. Particulates generated by the anthropogenic activities will be carried away and settle with the eroded soil to become sediment in the lake. This could cause serious problems in the aquatic environment if there is no monitoring study. Therefore, this study aimed to identify the anthropogenic material produced by human activities using physical and chemical properties analyses and pollution index calculations. The analysis of physical properties showed that Electrical Conductivity (EC), Total Dissolved Solid (TDS), and magnetic susceptibility were within the range of 30 – 790 µS/cm, 29 – 555 mg/L, 7.310 – 3431.956 ×10-8 m3/kg, respectively. The X-ray diffraction (XRD) and the hysteresis parameter indicated that the samples contain ferrimagnetic materials, particularly magnetite with a mixture of Pseudo-Single Domain (PSD) and Multi-Domain (MD). The Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) identified the morphology of the magnetic mineral with different shapes, such as octahedral and spherule. Furthermore, the spherule shape indicated the presence of anthropogenic materials in the sample. In terms of chemical properties, this study measured the pH and Potential Toxic Elements (PTEs) in the sediments. The pH ranged from 7.2-8.9, while the PTEs showed moderate to very severe levels of contamination by Mn, Pb, Zn, Cd, and Cu, which exceeded the sediment quality standard. The PCA reveals the interconnection between physical and chemical properties, which can identify pollutants derived from anthropogenic materials, as well as indicate low, medium, and high levels of pollution in the lake area.Područje jezera Ciburuy pod velikim je utjecajem širokoga spektra ljudskih aktivnosti, uključujući stambena područja, rižina polja, stočarstvo, plantaže, gust promet vozila i razne industrije, što dovodi do nakupljanja zagađivača. Čestice nastale antropogenim aktivnostima odnijet će se i taložiti s erodiranim tlom i postati sediment u jezeru. To bi moglo stvoriti ozbiljne probleme u vodenome okolišu ako ne postoji studija praćenja. Stoga je cilj ove studije bio identificirati antropogeni materijal proizveden ljudskim aktivnostima korištenjem analize fizičkih i kemijskih svojstava i izračuna indeksa onečišćenja. Analiza fizičkih svojstava pokazala je da su električna vodljivost (EC), ukupna otopljena krutina (TDS) i magnetska osjetljivost po redu unutar raspona 30 – 790 μS/cm, 29 – 555 mg/L, 7,310 – 3431,956 ×10-8 m3/kg. Difrakcija rendgenskih zraka (XRD) i parametar histereze pokazali su da uzorci sadržavaju ferimagnetske materijale, posebno magnetit s pseudojednodomenskom (PSD) i višedomenskom (MD) mješavinom. Skenirajući elektronski mikroskop (SEM) i energetska disperzivna spektroskopija (EDS) identificirali su morfologiju magnetskoga minerala s različitim oblicima, kao što su oktaedar i sferula. Nadalje, oblik sferule upućuje na prisutnost antropogenih materijala u uzorku. Što se tiče kemijskih svojstava, ova studija mjeri pH i potencijalno toksične elemente (PTE) u sedimentima. pH je bio u rasponu 7,2 – 8,9, dok su PTE pokazivali umjerenu do vrlo jaku razinu kontaminacije Mn, Pb, Zn, Cd i Cu, što je premašilo standard kvalitete sedimenta. PCA otkriva međusobnu vezu između fizičkih i kemijskih svojstava, koja mogu identificirati zagađivače koji potječu od antropogenih materijala, kao i uputiti na niske, srednje i visoke razine onečišćenja u području jezera

Struktur Resistivitas Dangkal Sebagai Upaya Mitigasi Bencana Pergerakan Tanah

Cisempur village is located at the slope of Mount Geulis, having a very variated morphology from gentle slopes to very steep ones. Due to the high demand for settlements the land use change can not be avoided.  The steepness of the slope, the decrease of the number of vegetations, and the increase of load from buildings may induced land slide occurrence.  This problem motivate us to perform measurement at the area, in order to uncover the information about the level of stability and the land carrying capacity, through the study of the subsurface rock layering condition. In this work, we present the shallow resistivity by means of Electrical Resistivity Tomography (ERT) method in two measurement lines. The obtained data is processed using 2D inversion method, in order to obtain the layering structure cross-section. The interpretation of the results suggest the existence of sandstone, which is normally associated with the location of aquifer and tuffaceous clay. The tuffaceous may function as the slide plane in the land slide event. The interpretation also shows that the carrying capacity decrease very extremely at the settlement site, which is indicated by the land displacement. This information has to be socialized and transferred to the inhabitant, in order to build awareness, and the land slide disaster mitigation can be carried out

LITHOLOGY AND RESERVOIR IDENTIFICATION IN THE “EL” WELL, EAST JAVA USING SEISMIC INVERSION

The acoustic impedance inversion seismic method, carried out at the "EL" well in East Java,provides a description of the physical properties of subsurface rocks. This method involves identifying rocklayers, lithology types, porosity values, the presence of hydrocarbons, and fluids in the target zone usingboth well data and integrated seismic data. The data processing included the cross-plotting of acousticimpedance (AI) with gamma ray logs, porosity logs, and resistivity logs. We integrated seismic and welldata, picked horizons, and created AI inversion models. The based model inversion technique was used tocompare the synthetic model with the seismic data, aiming to obtain an AI value that closely represents theactual model. AI seismic inversion effectively separates lithological boundaries vertically and laterally,based on the selected picking horizon and created model. To enhance understanding of the lithology andhydrocarbon prospect zone in the study area, a cross-plot analysis was used to correlate the seismic inversionmodel. The results reveal that the study area represents a hydrocarbon prospect zone, with reservoir rocksconsist of coral and foram at a depth range of 2320 - 2430 ft

Identification of Sediment Formation Based on Magnetic Content and Element Composition of Mud Volcano in Sangiran Sediment using VSM and X-Ray Fluorescence

Based on trace geological history and several studies, the Sangiran mud volcano provides insight into the geology and hydrology of the region, aquifer system in the basin, groundwater flow patterns and characteristics, rock lithology, hydrogeology condition, and saltwater trap mapping. Related to these conditions, studies were conducted on the magnetic content and composition of the major oxide compounds in the Sangiran sediments. Sample analysis was based on geochemical methods. The methods consist of frequency dependent magnetic susceptibility and vibrating sample magnetometer (VSM) analysis. Geochemical analyses using x-ray fluorescence (XRF) analysis have been conducted and various elemental grades have been determined. VSM results confirm that the magnetic content of Sangiran sediments is partly dominated by Fe (17.66 percent) contained in hematite (Fe2O3). At the same time, the samples of Sangiran sediment were enriched by Si, Fe, Al, Ca, Cl, Ti, and K according to XRF measurements. The samples exhibited the highest Si and Fe concentrations in samples T1 (Si is 29.48 percent and Fe is 13.66 percent) and T7 (Si is 24.95 percent and Fe is 12.01 percent). Meanwhile, in the T4 sample, the highest concentrations were Si and Ca, 23.45 percent and 13.45 percent, respectively. Retrieved from the magnetic susceptibility measurement, this paper confirm that Fe content is one of the components of volcanic ash in the Sangiran sediment.DOI: 10.17977/um024v8i12023p00