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Paper No. 240-4
Presentation Time: 2:20 PM
A GEOCHEMICAL ANALYSIS OF COLUMBIA RIVER BASIN VINEYARD SOILS
Soils of the Columbia Basin are predominantly developed on ice-age flood sediments, loess, and basalt. This study seeks to evaluate the relative influence of these components on the mineralogy and geochemistry of Columbia Basin vineyard soils, and the variation of that influence with depth. Samples were collected at 10 cm increments down to 50 cm below ground level from vineyards within the Walla Walla Valley American Viticultural Area (AVA). Soil chemistry and mineralogy were analyzed using scanning electron microscopy, x-ray diffraction, and x-ray fluorescence spectroscopy. Soil organic content, carbonate content, pH, and conductivity were also measured. Samples from other Columbia Basin sub-AVAs were also obtained and analyzed for comparison. Samples were found to be enriched relative to granite and basalt end members in K, Sr, Fe, and Mn, while most vineyards were depleted in Rb. A distinct layer in each soil was found to be enriched in Ca, as well as concentrations of V and Zn to increase and decrease with depth, respectively. The high concentrations of elements associated with mafic end members led to the conclusion that the soil chemistry is closely related to the region’s basaltic bedrock, while the mineralogy demonstrates the presence of felsic components in the soils. The lack of clear examples of mafic minerals, paired with the high concentrations of Fe and Mn, points to the presence of these elements in weathered forms. Further study is needed to completely understand the discordance between the geochemistry and the mineralogy in this study.