Pedosphere 26(4): 549--560, 2016
ISSN 1002-0160/CN 32-1315/P
©2016 Soil Science Society of China
Published by Elsevier B.V. and Science Press
In-situ differentiation of acidic and non-acidic tundra via portable X-ray fluorescence (PXRF) spectrometry
S. CHAKRABORTY1, D. C. WEINDORF2, G. J. MICHAELSON3, C. L. PING3, A. CHOUDHURY1, T. KANDAKJI2, A. ACREE4, A. SHARMA2 and WANG Dan-Dan5
1Uttar BangaKrishiViswavidyalaya, Cooch Behar 736165 (India)
2Department of Plant and Soil Science, Texas Tech University, Lubbock TX 79409 (USA)
3University of Alaska Fairbanks, Palmer Research Center, Palmer AK 99645 (USA)
4Louisiana State University Agricultural Center, Baton Rouge LA 70803 (USA)
5College of Geography and Remote Sensing, Nanjing University of Information Science and Technology, Nanjing 210044 (China)
ABSTRACT
      Frozen soils or those with permafrost cover large areas of the earth’s surface and support unique vegetative ecosystems. Plantsgrowing in such harsh conditions have adapted to small niches, which allow them to survive. In northern Alaska, USA, both moistacidic and non-acidic tundra occur, yet determination of frozen soil pHs currently requires thawing of the soil so that electrometric pHmethods can be utilized. Contrariwise, a portable X-ray fluorescence (PXRF) spectrometer was used in this study to assess elementalabundances and relate those characteristics to soil pH through predictive multiple linear regressions. Two operational modes, SoilMode and Geochem Mode, were utilized to scan frozen soils in-situ and under laboratory conditions, respectively, after soil sampleswere dried and ground. Results showed that lab scanning produced optimal results with adjusted coefficient of determination (R2) of0.88 and 0.33 and root mean squared errors (RMSEs) of 0.87 and 0.34 between elemental data and lab-determined pH for Soil Modeand Geochem Mode, respectively. Even though the presence of ice attenuated fluoresced radiation under field conditions, adjusted R2 and RMSEs between the datasets still provided reasonable model generalization (e.g., 0.73 and 0.49 for field Geochem Mode). Principalcomponent analysis qualitatively separated multiple sampling sites based on elemental data provided by PXRF, reflecting differences inthe chemical composition of the soils studied. Summarily, PXRF can be used for in-situ determination of soil pH in arctic environments without the need for sample modification and thawing. Furthermore, use of PXRF for determination of soil pH may provide highersample throughput than traditional eletrometric-based methods, while generating elemental data useful for the prediction of multiplesoil parameters.
Key Words:  frozen soil, Gelisols, Geochem Mode, proximal sensing, Soil Mode, soil pH determination
Citation: Chakraborty, S., Weindorf, D. C., Michaelson, G. J., Ping, C. L., Choudhury, A., Kandakji, T., Acree, A., Sharma, A. and Wang, D. D. 2016. In-situ differentiation of acidic and non-acidic tundra via portable X-ray fluorescence (PXRF) spectrometry. Pedosphere. 26(4): 549-560.
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