Abstract

BRAVO COVARRUBIAS, América; TORRES, Ester; AYORA, Carlos  and  RAMOS ARROYO, Yann René. ARSENIC MOBILITY IN THE SEDIMENTS OF A DAM THAT RECEIVES RUNOFFS FROM EPITHERMAL MINES. Rev. Int. Contam. Ambient [online]. 2020, vol.36, n.4, pp.797-811.  Epub Sep 13, 2021. ISSN 0188-4999.  https://doi.org/10.20937/rica.53318.

The objective of this work was to quantify As, Pb, Fe and Mn in the mineral phases of recent sediments in a dam that receives runoffs from abandoned mines and to propose scenarios of retention and release of As in and from the reservoir. The Santana dam (SD) is located at the exit of a basin with three reservoirs in cascade in the municipality of Guanajuato. The four samples analyzed were collected at a depth of 0.1 m along a topographic-geochemical transect inside the SD. A protocol of sequential extractions of seven steps was applied considering the reactivity and mobility, in order to know the elemental contents in the different mineral phases and the potential translocations between them. The extracts of each fraction as well as an acid digestion of each sample were analyzed by inductively coupled plasma mass spectroscopy and inductively coupled plasma atomic emission. Images were generated by scanning electron microscopy of a sample collected in the curtain. The total elemental content in sediments yielded the following values (in mg kg-1): As, 25.11 to 28.80; Pb, 0.64 to 2.83; Mn, 562.3 to 862.3; Fe, 51 276.3 to 79 820.5. From the entrance and towards the curtain, As decreases in the fraction of crystalline oxides; in contrast, it increases in the exchangeable fraction of amorphous oxides and sulphides. The concentration of iron increases in the exchangeable fraction of amorphous oxides and sulphides. Manganese accumulates near the curtain, mainly in the fractions of amorphous and crystalline oxides.

Keywords : supply; sequential extraction; geochemical transect; reservoir.

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