ABSTRACT: Rare earth elements (REE) were analyzed in surface sediments from the Guadiana Estuary (SW Iberian Pyrite Belt). NASC (North American Shale Composite) normalized REE patterns show clearly convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE, indicating acid-mixing processes between fluvial waters affected by acid mine drainage (AMD) and seawater. However, REE distributions in the mouth (closer to the coastal area) show slightly LREE-enriched and flat patterns, indicating saline-mixing processes typical of the coastal zone. NASC-normalized ratios (La/Gd and La/Yb) do not discriminate between both mixing processes in the estuary. Instead, a new parameter (E(MREE)) has been applied to measure the curvature in the MREE segment. The values of E(MREE)>0 are indicative of acid signatures and their spatial distribution reveal the existence of two decantation zones from flocculation processes related to drought periods and flood events. Studying REE fractionation through the E(MREE) may serve as a good proxy for AMD-pollution in estuarine environments in relation to the traditional methods.
Marine pollution bulletin 06/2012; 64(9):1799-808. · 2.63 Impact Factor
ABSTRACT: The Odiel River is located in southwestern Spain; the greater portion of its basin is composed of materials from the Iberian
Pyrite Belt (IBP), an area with numerous massive sulfide deposits that have been highly exploited since the third millennium
BC. As sulfides come into contact with the atmosphere due to mining activity, oxidation occurs, generating a highly toxic
acidic leachate with large concentrations of sulfates and metals, a process which is known as acid mine drainage (AMD). As
a result, the Odiel River and most of its tributaries are severely contaminated. The construction of two large dams in the
Odiel River basin is planned. The most advanced project is that of the Alcolea reservoir, with a storage capacity of 274hm3, whose construction has already begun, with a total budget of around €164 million. There are reasonable doubts about the
final quality of the reservoir water, as this dam will regulate a river with a mean pH close to 3.5 and large concentrations
of toxic elements. This paper analyzes the data of water quality in the Alcolea reservoir. The results show that the reservoir
water will be acidic and not useful at all, although more specific studies are necessary to obtain the exact estimation of
its hydrochemical characteristics. It seems unwise to start building the dam, which requires a large economic investment and
will have a vast environmental impact, without first conducting these studies. This proves that water management in Spain
is still based on political motivation rather than on technical criteria and good management of natural and economic resources.
KeywordsOdiel-Alcolea reservoir-Acid mine drainage-Water quality-Water management
Water Resources Management 04/2012; 25(1):201-215. · 2.05 Impact Factor
ABSTRACT: In 1998, the Agrio and Guadiamar rivers underwent an enormous environmental disaster caused by the rupture of the Aznalcóllar tailings dam and the release of 6 hm(3) of pyrite sludge and acidic water. Both rivers run over recent alluvial materials which form a small-sized aquifer which is however important because underground water feeds the flow of the rivers. This work analyzes the state of groundwater 10 years after the spill. Before the dam failure, this aquifer was already contaminated in the zone nearest to the mine, to which the impact of the spill was added. Contamination levels in the alluvial aquifer of the Agrio River have decreased remarkably. However, they are still important, with acidic pH values and high concentrations of toxic elements (maximum values of 16 mg/L of Zn and 15 mg/L of Al). There are also important levels of contamination in the Guadiamar alluvial area closest to the mine, as well as in specific zones located further south. The concentration of toxic elements is mainly controlled by pH. The evolution of contaminant levels show a sharp decrease after the first years following the spill, followed by a subsequent stabilization. It is necessary to take measures for the recovery of the aquifer because, otherwise, groundwater will continue contributing contaminants into the Agrio and Guadiamar rivers.
Environmental Monitoring and Assessment 07/2011; 184(6):3629-41. · 1.40 Impact Factor