Geostatistics Application On Uranium Resources Classification: Case Study of Rabau Hulu Sector, Kalan, West Kalimantan

ABSTRACT In resources estimation, geostatistics methods have been widely used with the benefit of additional attribute tools to classify resources category. However, inverse distance weighting (IDW) is the only method used previously for estimating the uranium resources in Indonesia. The IDW method provides no additional attribute that could be used to classify the resources category. The objective of research is to find the best practice on geostatistics application in uranium resource estimation adjusted with geological information and determination of acceptable geostatistics estimation attribute for resources categorization. Geostatistics analysis in Rabau Hulu Sector was started with correlation of the orebody between boreholes. The orebodies in Rabau Hulu Sectors are separated individual domain which further considered has the hard domain. The orebody-15 was selected for further geostatistics analysis due to its wide distribution and penetrated most by borehole. Stages in geostatistics analysis cover downhole composites, basic statistics analysis, outliers determination, variogram analysis, and calculation on the anisotropy ellipsoid. Geostatistics analysis shows the availability of the application for two resources estimation attributes, which are kriging efficiency and kriging variance. Based on technical judgment of the orebody continuity versus the borehole intensity, the kriging efficiency is considered compatible with geological information and could be used as parameter for determination of the resources category. ABSTRAK Pada estimasi sumber daya, metode geostatistik telah banyak digunakan dengan kelebihan adanya alat atribut tambahan untuk mengklasifikasikan kategori sumber daya. Namun demikian, pembobotan inverse distance (IDW) adalah satu-satunya metode yang sebelumnya digunakan untuk mengestimasi sumber daya uranium di Indonesia. Metode IDW tidak memberikan tambahan atribut yang dapat digunakan dalam mengklasifikasikan kategori sumber daya. Tujuan dari penelitian adalah mendapatkan praktek terbaik untuk aplikasi geostatistik pada estimasi sumber daya disesuaikan dengan informasi geologi dan penentuan atribut geostatistik yang dapat digunakan untuk kategorisasi sumber daya. Analisis geostatistik di Sektor Rabau Hulu diawali dengan korelasi tubuh bijih antara lubang bor. Tubuh-tubuh bijih di Sektor Rabau Hulu merupakan domain individual yang selanjutnya dipertimbangkan memiliki domain tegas. Tubuh bijih-15 dipilih untuk digunakan pada analisis geostatistik selanjutnya karena distribusinya yang luas dan paling banyak dipenetrasi bor. Tahapan dalam analisis geostatistik mencakup komposit downhole, analisis statistik dasar, determinasi outliers, analisis variogram, dan perhitungan ellipsoid anisotropi. Analisis geostatistik menghasilkan kemungkinan aplikasi dua atribut estimasi sumber daya, yaitu kriging efisiensi dan kriging varians. Berdasarkan penilaian teknis kemenerusan tubuh bijih terhadap intensitas lubang bor, kriging efisiensi dipertimbangkan sesuai dengan informasi geologi dan dapat digunakan sebagai parameter untuk penentuan kategori sumber daya.

THE USE OF GEOGRAPHIC INFORMATION SYSTEMS IN THE DETERMINATION OF AREAS AT RISK OF DENGUE IN THE SÃO PAULO STATE

The Dengue Virus is a Flavivirus transmitted to humans by Aedes mosquitoes. This arbovirus is responsible for one of the main problems of global public health, because it is estimated that over 80 million people are infected by it every year. In Brazil there are reports that dengue fever epidemics have been present from the beginning of the twentieth century. However, the first dengue fever outbreak documented in the country occurred in 1982. From that point on, the Brazilian territory has been plagued by several of these epidemics. Among the various attempts to elucidate the factors that influence the dynamics of the transmission of dengue fever, the Brazilian Ministry of Health reorganized, in 2002, the National Plan to Combat Dengue Fever and instituted a normative procedure by which the areas affected by this epidemic should be mapped. The use of geographical information systems is a powerful tool for the spatial analysis of risk; by this means the spatial distribution of the event can be described and associations between an event and its determinants can be observed. Based on these assumptions this study aims to determine the geospatial patterns of dengue fever outbreaks in S„o Paulo State, Brazil. This region has been seriously affected by successive epidemics during the last 15 years. We have used conventional and spatial analytical tools (geostatistics analysis) to discern the patterns of the epidemic scenarios. Results showed that dengue fever outbreaks have affected two principal areas of risk: one located in the northwest and the other in the central-south portion of the S„o Paulo State

VARIABILIDADE ESPACIAL DE ATRIBUTOS QUÍMICOS EM UM LATOSSOLO VERMELHO AMARELO SOB CULTIVO COM GOIABA (Psidium guajava L.)

O objetivo do trabalho foi avaliar a variabilidade espacial de atributos químicos do solo sob cultivo com goiaba por meio da análise de geoestatística nas profundidades de 0,0-0,10 m e 0,10-0,20 m. Foi realizado amostragem regionalizada utilizando malha regular com dimensão de 50 m x 50 m, totalizando 36 pontos georreferenciado equidistantes 10 m. A análise geoestatística foi utilizada para a determinação de modelos teóricos de variogramas e para a interpolação por krigagem dos dados que foram gerados, a fim de analisar a variabilidade espacial dos atributos dos solos. O pH apresentou variabilidade espacial baixa nas duas profundidades e o Al na profundidade de 0,10-0,20 m com moderada variabilidade espacial na profundidade de 0,0-0,10 m. O Ca e Mg apresentaram moderada variabilidade espacial nas duas profundidades. O modelo esférico de semivariograma foi ajustado para todos atributos nas duas profundidades, com alcances variando entre 12,5 m e 24,1 m para os atributos pH e Al, respectivamente.PALAVRAS-CHAVE: Geoestatística, manejo do solo, dependência espacial, krigagem. SPATIAL VARIABILITY OF THE CHEMICAL ATTRIBUTES IN A RED-YELLOW LATOSOL UNDER CULTIVATION CONTINUOUSABSTRACT: The objective of the work was to evaluate the spatial variability of soil chemical attributes under cultivation with guava through geostatistics analysis in the depths of 0.0-0.10 m and 0.10-0.20 m. Sampling was performed regionalized using regular grid with dimension of 50 m x 50 m, totaling 36 georeferenced points equidistant 10 m. The geostatistical analysis was applied to determine theoretical models of variograms and interpolation kriging of the data that have been generated in order to analyze the spatial variability of the soil attributes. The pH presented low spatial variability on both depths and Al on depth 0.10-0.20 m with moderate spatial variability on the depth 0.0-0.10 m. Ca and Mg showed moderate spatial variability in both depths. The spherical semivariogram model was adjusted for all attributes in both depths, close to 12.5 m and 24.1 m for pH and Al, respectively.KEYWORDS: Geostatistics; soil management; spatial dependence, kriging.