Effects of quarry mining and of other environmental impacts in the mountainous Chicam-Toctina drainage basin (Córdoba, Argentina)

D.M. GAIERO1, H.E. PESCI2 AND P.J. DEPETRIS1

ENVIRONMENTAL GEOLOGY

Springer-Verlag

Año: 1998 p. 159 - 166

0943-0105

The environmental conditions prevailing in the Chicam-Toctina drainage system (approx. 138 Km2 in Córdoba, Argentina) are considered representative of a number of catchments in Argentina's Sierras Pampeanas range. Two groups of ions reflect the  sources of dissolved species in the catchment: a)  a group (Cl-, SO- and Na+) which recognizes natural and anthropogenic sources, and which exhibits significant correlations with NO and NO, and b) another group of components (Ca2+, Mg2+, and HCO) which is clearly controlled by carbonate rocks and their waste rock products. In the headwaters, stock-piled marble quarry mining wastes determine a more open system to CO2 gaseous exchange than the outcropping rocks, thus promoting the increase of carbonate dissolution (up to 4.88 g Km-2 s-1 during the rainy season). This specific yield was 20% higher than the amount estimated for an area with fewer extended mining activities. The dissolved load delivered by the upper stretches is subjected in the lower drainage area to various processes, mainly controlled by the presence of Alta Gracia city (approx. 40,000 inhabitants). In the dry season, due to nutrients input supplied by the city, photosynthetic activity plays a major role controlling stream pH. Hence, the high values of calcite saturation indexes and the increase of CaCO3 concentration in bed sediments would be explained by calcite precipitation. Such process could be accompanied by the co-precipitation on calcium carbonate of low solubility heavy metal carbonates. Key words: quarry mining, waste rocks, marble, domestic pollution