Hydrochemical heterogeneity in karst tributaries on siliciclastic boundaries ? Corrente River, Bahia ? Brazil

SILVA-FILHO EV; LECOMTE K.L.; BICALHO CC

Advances in Karst Science

Springer

Año: 2017; p. 345 - 350

The karst aquifers in the San Franciscan depression belong to the sandstone aquiferand subjected to intense fresh water pumping. The Corrente River provides nearly30 % of the São Francisco River?s water flow. The main objective of the presentpaper was to define sources and distribution of dissolved elements and to describethe geochemical processes that govern their mobility within the Urucuia Aquifer.Water samples are classified into three groups, depending on the dominant weatheringprocess. When carbonate dissolution dominates waters are of bicarbonate?calcium-type, whereas, when the atmospheric precipitation signal is present, thesamples in siliciclastic terrain are mostly of Cl−?Na+ type. Ground waters reflectbicarbonate?mixed-type, with the highest dissolved concentrations. In contrast tomajor elements, trace elements, including rare earth elements (REEs), show seasonalbehavior: their concentrations increase in the beginning of the wet season, due tore-mobilization and release into the solution of adsorbed elements from the systemand the atmospheric dust. The total dissolved REE concentration (800?7500 ng L−1)is one order of magnitude more concentrated in karst than in siliciclastic rocks.