Duangkamol, K.

Moonjun, R.

Shrestha, D. P.

English

Gamma-ray radioelements are a potential information source for soil mapping, since their abundance is related to soil geochemistry, specifically the chemical composition of parent materials and their weathering products resulting from geomorphic and pedogenic processes (IAEA 2003). Soils have been developed over sedimentation landscapes such as in alluvium and flood plain are uncertain due to the sedimentation process, which is difficult to characterize by field soil survey. Thailand has advantage of Airborne Gamma-ray Imagery (AGRI) covering whole country, for mineral survey but not yet for soil survey. Fuzzy classification method has been recommended as the potential techniue for digital soil mapping (McBratney et al. 2003).</p

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River Sedimentation – Wieprecht et al. (Eds)© 2017 Taylor & Francis Group, London, ISBN 978-1-138-02945-3Application of airborne gamma-ray imagery to assist soil survey in the upperPasak basin, ThailandR. MoonjunDepartment of Earth Systems Analysis, ITC Faculty , University of Twente, Enschede, The NetherlandsLand Development Department, Ministry of Agriculture & Cooperatives, ThailandD.P. ShresthaDepartment of Earth Systems Analysis, ITC Faculty, University of Twente, Enschede, The NetherlandsK. DuangkamolLand Development Department, Ministry of Agriculture & Cooperatives, ThailandABSTRACTGamma-ray radioelements are a potential informa-tion source for soil mapping, since their abundance isrelated to soil geochemistry, specifically the chemicalcomposition of parent materials and their weatheringproducts resulting from geomorphic and pedogenicprocesses (IAEA 2003). Soils have been developedover sedimentation landscapes such as in alluvium andflood plain are uncertain due to the sedimentation pro-cess, which is difficult to characterize by field soil sur-vey. Thailand has advantage of Airborne Gamma-rayImagery (AGRI) covering whole country, for mineralsurvey but not yet for soil survey. Fuzzy classificationmethod has been recommended as the potential tech-niue for digital soil mapping (McBratney et al. 2003).The aim of this study was to evaluate the potentialof AGRI for improving digital soil survey process intwo phases: (1) a preliminary phase, where hypothe-ses of soil-geological unit relationships where soils aredeveloped, and (2) a phase where soil map unit bound-aries are generated using AGRI and DEM covariables.The study was conducted in a well-characterizedcomplex in flood plain and river terraces soil land-scape: the 300 km2upper Pa Sak Valley in Petchaboonprovince, Thailand.The relationship between AGRI data and geologicalunits were examined by the distribution of radioele-ment response to selected soil sediment characteris-tics, based on a review of literature and supportedby observation samples. The potential of AGRI tomap sediment soils were examined by interpolate soilobservation points applying fuzzy classification overthe alluvium and flood plain. Where, soil map wasproduced from four covariables; three from gamma-ray radio element (%K, eTh and eU) and DEM usingfuzzy classification.To interpret the relation of gamma-ray radio-element with sediment geological units, the resultsshow that, the Pleistocene sediments (Qt), consistingof mixed old alluvial materials on terraces, shows threedifferent radioelement compositions. The HoloceneFigure 1. (left) Airborne Gamma-Ray Imager (AGRI), withgeologic units and (right) predicted soil map from AGRIbased on fuzzy classification with 92 observation points(black dots).sediments, indicated by Qa, area cover a relativelylarge area and they are high in all three radioelements.In the producing soil map, with a soil familylevel, the best result map was produced and foursoil mapping units were interpolated as: 1) Fine silty,mixed, Aeric Vertic Endoqualfs, 2) Fine, mixed, TypicEndoaqualfs, 3) Loamy-skeleton, kaolinitic, TypicPaleustults and 4) Loamy-skeletal over fragmental,kalionitic, Petroferric kalionitic, Petroferric Haplus-tults. The result map was assessed the accuracy using92 observation point data, the accuracy result areoverall classification accuracy = 67.85% and 2 overallKappa statistics is 0.6419.In the hypotheses-generating stage, AGRI provideduseful information in three forms (single signal, ratio,and lithology, material transport, and internal pedoge-netic processes). In the mapping stage, AGRI showeddeficiencies in the soil map production over alluviumterraces and flood plains, which provided a basis forfuture field sampling to correct these deficiencies.AGRI suggested new boundaries, differentiatingtopsoil properties and the presence of plinthite. Furtherstudy, AGRI can be recommend for mapping some topsoil properties together with other suitable covariablesaccording to soil forming factors.REFERENCESIAEA. 2003. Guidelines for radioelement mapping usinggamma ray spectrometry data In: International AtomicEnergy Agency, Vienna.McBratney et al. 2003. “On digital soil mapping.” Geoderma117(1–2): 3–52.69

Application of airborne gamma-ray imagery to assist soil survey in the upper Pasak basin, Thailand

https://ris.utwente.nl/ws/files/70065163/Moonjun_et_al._2017_Application_of_airborne_gamma_ray_imagery_to_assist_soil_survey.pdf

Application of airborne gamma-ray imagery to assist soil survey in the upper Pasak basin, Thailand

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