The Geochemistry and Impacts of Chemical Weathering on the Central Namib Desert Gravel Plains Soils
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Date
2020-05
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The Ohio State University
Abstract
The Namib Desert is one of the most arid deserts in the world. Surficial soil samples were collected along a transect at 20 km intervals from Walvis Bay, on the Atlantic Coast, to 200 km inland where the transect ends. The focus of this study was to evaluate the accumulation of salts in the soils and to determine the extent of chemical weathering along the transect. The soils were leached with water for 5 days and the leachates were analyzed for concentrations of their major cations and anions. In addition, the solids were analyzed for their total major element concentrations. From 20 km to 90 km inland, the soils have higher concentrations of weatherable Ca and Na than do the samples inland. From 100 km to 200 km inland, these concentrations decrease. The chemical index of alteration (CIA) was determined using the results from the solid soil analysis. From 20 km to 140 km inland, the soils showed little to no weathering. From 160 km to 200 km inland, the soils were much more altered with the loss of major cations, Ca, Na, K. When combined, all these data clearly demonstrate the influence of precipitation on the geochemistry of the soils. The soils that are closer to the shore have a higher salt accumulation, whereas further away from the coastline there is a lower amount of salt accumulation indicating chemical weathering is occurring. These data support the general notion that there is a greater accumulation near the coast because there is less precipitation and causing the soils to have little to no weathering.
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Keywords
Chemical Weathering, Soil, Geochemistry, Central Namib Desert, Gravel Plains