Determination of Primary Mineral Content and Calcium Sources in Forest Soils using Electron Probe Microanalysis Mapping and Cluster Analysis
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Soil Science Society of America Journal
Although mineral dissolution is a fundamental soil forming process, primary mineral content of soils is rarely inventoried or quantified. Concerns about maintenance of forest soil nutrient stocks require better mineralogic data. In particular, to understand recovery from Ca losses induced by acid deposition and sustainability of intensive forest harvest, better inventory of primary Ca minerals is needed. We developed a method based on electron probe micro-analysis to quantify primary mineral concentrations in soil. Samples analyzed from three sites in the glaciated northeastern United States spanned a bulk Ca concentration of 0.03 to 0.94%. Plagioclase was the dominant Ca-bearing mineral at two sites while apatite was the only Ca-bearing mineral found in all three samples and was the dominant calcium source at one site. A variety of other Ca silicate minerals were found in trace amounts. Electron probe microanalysis (EPMA) proved more sensitive in detecting minor and trace Ca bearing minerals than standard XRD procedures. The Ca-bearing minerals detected by EPMA matched those expected based on the lithologic composition of the glacial till and were consistent with measured bulk soil Ca content by lithium-borate fusion. Taking into account the Ca concentration in each mineral and each mineral's abundance in the sample, this inventory provided a complete accounting of Ca sources.
Bailey, Scott W.; Ross, Donald S.; Perdrial, Nico; Jercinovic, Michael; Webber, Jeffrey; Bourgault, Rebecca. 2019. Determination of Primary Mineral Content and Calcium Sources in Forest Soils using Electron Probe Microanalysis Mapping and Cluster Analysis. Soil Science Society of America Journal. 83(6): 1830-1841. https://doi.org/10.2136/sssaj2019.07.0231.