Abstract
This study examined sediment phosphorus (P) geochemistry in the Feitsui Reservoir, Taiwan, during a period when groundwater outbursts carrying Ca exports occurred during tunnel construction at the catchments. In order to evaluate the impact of such events on P release from reservoir sediments, chemical fractionations of P along with the concerned metals, Al, Fe, Mn, and Ca in sediments, catchment top soils, and tunnel drilling debris were performed. The chemical composition of porewater (mixed 10-cm sediment layer) was analyzed on soluble P, soluble metals (Fe, Mn, Al, Ca), sulfide, and fluoride. A diagenesis simulation was conducted. It was concluded that oversaturation of porewater P and the formation of Fe, Mn, and Ca bound P minerals accumulated in sediments, which were originally dominated by Al bound P. This suggests that the Ca exports had impacted P geochemistry, resulting in suppressed P mobility.
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