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A 1.2 km long effluent from La Zarza-Perrunal mine (Iberian Pyritic Belt, IPB) was
characterized and compared with Río Tinto. In La Zarza effluent microbial oxidation of ferrous iron
is responsible for the drastic increase in ferric iron, from a ratio of Fe(III)/Fe
total
of 0.11 at the origin,
up to 0.99 downstream. Prokaryotic and eukaryotic diversity throughout the effluent were
determined. Bacteria related to the sulfur cycle as well as iron-reducing bacteria were mainly
detected near the anoxic origin. Iron-oxidizing microorganisms increased along the course of the
effluent following an increase in the oxygen content in the water column. Eukaryotic diversity
varied drastically along the effluent. Rio Tinto (92 km length) is a natural extreme acidic
environment with a rather constant acidic pH (mean pH value 2.3) and a high concentration of
heavy metals. The Tinto ecosystem is under the control of iron [1]. The geomicrobiological
comparisons of both habitats were performed to unravel some basic questions of
biohydrometallurgical interest.
Río Tinto is a 92-km-long river (SW Spain) which is considered a good model system for the study
of extreme acidic environments and acid rock drainage (ARD). It has a low pH (mean pH 2.3) and
high concentrations of heavy metals in solution (up to 20 g/l of iron, 0.7 g/l of copper and 0.6 g/l of
zinc) [1, 2]. It is well established that the extreme conditions of Rio Tinto are the product of the
metabolic activity of chemolithotrophic microorganisms (mainly Acidithiobacillus ferrooxidans and
Leptospirillum ferrooxidans) thriving in the high concentration of sulfidic minerals from the IPB.
Moreover, an unexpected level of eukaryotic diversity has been described in the Tinto basin in spite
of the extreme conditions found in its waters [3]. Río Tinto geomicrobiology has been studied in
depth [1, 2]. Many studies have concentrated on the iron and sulfur oxidation, but little is known
about the reductive part of these cycles which are of extreme importance for biohydrometalurgical
processes because they reduce the efficiency of metal extraction
Although closed in the 1990s, La Zarza-Perrunal (IPB) had been mined since pre-Roman times for
the recovery of Ag and Au, and in modern times, for sulfuric acid and metal retrieval (Cu, Zn and
Pb). This acidic effluent has a fairly constant flow rate of ~2 l/s. [4]. After receiving fresh water,
this stream merges with different creeks, until its final neutralization. Previous studies reported the
geochemical evolution of this site [4], but knowledge of its correlation with microbial metabolic
activities is needed to better understand the operation of the sulfur and iron cycles in these
environments. In this work, the geomicrobiological characterization of La Zarza-Perrunal effluent is
presented and compared with that of Rio Tinto.
Advanced Materials Research Vols. 71-73 (2009) pp 113-116
online at http://www.scientific.net
© (2009) Trans Tech Publications, Switzerland
Online available since 2009/May/19
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the
publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 193.146.141.171-19/05/09,16:01:56)