Elemental ratios in sediments as indicators of ecological processes in Spanish reservoirs

Abstract

Reservoir sediments are important archives of biogeochemical data, reflecting ecological processes that occur at the watershed system. In this paper, a preliminary study of the limnological significance of major element composition and element ratios in sediments of Spanish reservoirs is presented, by analysing two data-sets from different limnological regions. Reservoirs from Eastern and Western Spain present significant differences in the chemical composition of their sediments: higher average values for calcium and magnesium appear in the Eastern reservoirs, while, in Western Spain, higher mean values are found for alumino-silicate elements (i.e. silicon, aluminium, and potassium), iron and phosphorus. Meaningful ratios are Si/Al and Si/K, that are closely related to energy transport in sedimentary catchments, whereas in siliceous catchments Si/Al is an indicator of chemical weathering. Ca/Al ratio appears related to water mineralization, and, in the Eastern Region, the slope of the regression line between Ca/Al and conductivity reflects catchment mineralogy. In superficial sediments from both Eastern and Western regions, Fe/Al is linked to the authigenic precipitation of iron oxides and appears closely related to sedimentary phosphorus accumulation above background levels. © Asociación Española de Limnología.