Pedosphere 29(4): 468--482, 2019
ISSN 1002-0160/CN 32-1315/P
©2019 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Advances in Tropical Soil Characterization via Portable X-Ray Fluorescence Spectrometry
Elen A. SILVA1, David C. WEINDORF2, Sérgio H. G. SILVA1, Bruno T. RIBEIRO1, Giovana C. POGGERE1, Teotonio S. CARVALHO1, Mariana G. M. GONÇ ALVES1, Luiz R. G. GUILHERME1, Nilton CURI1
1Department of Soil Science, Federal University of Lavras, Lavras 37200-000(Brazil)
2Department of Plant and Soil Science, Texas Tech University, Texas 79409-2122(USA
      Portable X-ray fluorescence (pXRF) spectrometers can be used to determine the elemental composition easily, rapidly, and without using chemical reagents, which is very important for tropical regions due to the lack of detailed soil characterization data. Moreover, pXRF data can be used to predict the results of more expensive, time-consuming, and conventional laboratory analyses. This study sought to determine the elemental composition of various soil profiles using pXRF. Two operational modes (Trace Mode and General Mode) and two scanning time (30 and 60 s) were assessed to determine their effects on the correlation of pXRF dataset with respect to conventional inductively coupled plasma (ICP)-optical emission spectrometry analysis. This relationship has been reported in previous studies, however, few studies were performed on tropical soils, which are unique. Furthermore, such relationships establish the viability of developing prediction models directly from pXRF data. Linear regression was applied to develop calibration models for the prediction of ICP analysis results and exchangeable and available elemental contents based on pXRF data. High coefficients of determination (R2) were obtained for Ca (0.87), Cu (0.90), Fe (0.95), Mn (0.85), Cr (0.95), V (0.72), and Ni (0.90), with adequate validation. Statistically significant results were not found for Al, K, Zn, Ti, and Zr. The models predicting the exchangeable Ca based on the total Ca from pXRF reached an R2 of up to 0.85. Operational modes influenced the pXRF results. Our results illustrate that pXRF holds great promise for tropical soil characterization and the development of prediction models, justifying the need for larger-scale studies in tropical countries worldwide.
Key Words:  elemental composition,exchangeable Ca,inductively coupled plasma,operational mode,prediction models,scanning time,soil analysis,total elemental content
Citation: Silva E A, Weindorf D C, Silva S H G, Ribeiro B T, Poggere G C, Carvalho T S, Gonçalves M G M, Guilherme L R G, Curi N. 2019. Advances in tropical soil characterization via portable X-ray fluorescence spectrometry. Pedosphere. 29(4):468-482.
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