Ma. Armienta et A. Quere, HYDROGEOCHEMICAL BEHAVIOR OF CHROMIUM IN THE UNSATURATED ZONE AND IN THE AQUIFER OF LEON VALLEY, MEXICO, Water, air and soil pollution, 84(1-2), 1995, pp. 11-29
The ground water of Leon valley, Central Mexico, is contaminated with
chromium. A study was carried out to determine the main physico-chemic
al interactions between chromium and the aquifer solid matrix in the m
ost polluted area. Five boreholes, 30 m deep, were drilled and used as
piezometers. Unaltered solid cores were analyzed for Cr(VI), total Cr
, Fe and Mn. Cr(VI) was determined in the water from the piezometers.
We conclude that reduction of Cr(VI) by iron is important, adsorption
of Cr(VI) by sand and gravel layers is negligible, and adsorption by s
ilt and clay layers is significant in the saturated and unsaturated zo
nes. In the saturated zone hexavalent chromium distributes preferentia
lly in the water phase. oxidation of chromium by manganese was not det
ected. A correlation between chromium, manganese and iron concentratio
ns was observed for the aquifer solid matrix in this area, when the so
urce of chromium was not anthropogenic.