As scientists work to investigate the mechanisms underlying the depletion of carbon from terrestrial ecosystems, there has been an urgent call for the development of test methods that offer reduced analysis times for soil organic carbon (SOC) determinations. Traditional laboratory techniques can be time-consuming and costly, making high-volume sample analyses problematic. Portable x-ray fluorescence spectroscopy (PXRF) provides quantitative, multi-elemental data for soil samples in as little as 60 seconds; and, unlike other spectroscopic methods, differences in elemental concentrations between field-moist and oven-dry samples are considered to be negligible when soil moisture contents are less than 20%, by weight. This study aims to evaluate the performance of various SOC prediction models, constructed from PXRF elemental data from 300 soil samples collected from alluvium and loess parent materials found in Louisiana, USA. Elemental data, in addition to pH and depth measurements, were used in the construction of prediction models using multiple linear regression (MLR) analysis and principal components analysis (PCA) statistical techniques. Previous research indicates that the use of a stability index may enhance SOC prediction modeling capabilities. Therefore, models utilized relative elemental abundances on the basis on Zr and Ti concentrations, and performances were compared to those resulting from models developed from Raw PXRF data. Results show that models constructed using field-moist PXRF elemental data provide excellent SOC prediction capabilities (R > 0.90) for both alluvium and loess datasets. Optimal performances resulted from the use of Ti as a stability index for field-moist datasets, producing accurate SOC predictions for both wet and dry validation sub-datasets. Findings indicate that PXRF elemental analysis, conducted under field conditions, provide for accurate SOC content determinations via MLR modeling of Louisiana alluvium and loess soil types examined in this study.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-08312013-110314 |
| Date | 12 September 2013 |
| Creators | Nuss, Sara Kathryn |
| Contributors | Weindorf, David, Gaston, Lewis, Gambrell, Robert |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-08312013-110314/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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