Odiel River (SW Spain), a Singular Scenario Affected by Acid Mine Drainage (AMD): Graphical and Statistical Models to Assess Diatoms and Water Hydrogeochemistry Interactions

The Odiel River (SW Spain) is one of the most cited rivers in the scientific literature due to its high pollution degree, generated by more than 80 sulphide mines’ (mostly unrestored) contamination in the Iberian Pyritic Belt (IPB), that have been exploited for more than 5000 years. Along the river and its tributaries, the physico-chemical parameters and diatoms, from 15 sampling points, were analyzed in the laboratory. Physico-chemical parameters, water chemical analysis, together with richness and Shannon–Wiener indexes were integrated in a matrix. An initial graphical treatment allowed the definition and proposal of a functioning system model, as well as the establishment of cause–effect relationships between pollution and its effects on biota. Then, the proposed model was statistically validated by factor analysis. For acidic pH waters, high values of Eh, TDS, sulphate, ∑REE and ∑Ficklin were found, while diatomologic indicators took low values. Thus, factor analysis was a very effective tool for graphical treatment validation as well as for pollution–biota interaction models’ formulation, governed by two factors: AMD processes and water balance suffered by the studied river. As a novelty, the cause–effect relationships between high barium concentration and low diversity and richness were demonstrated in the IPB, for the first time.

Application of a Fuzzy Logic Based Methodology to Validate the Hydrochemical Characterization and Determining Seasonal Influence of a Watershed Affected by Acid Mine Drainage

The Odiel River Basin, located in the Iberian Pyrite Belt (IPB), is heavily affected by acid mine drainage (AMD), which occurs when pyritic minerals from sulfide mining areas are exposed to atmospheric, hydrological or biological weathering. This paper presents a hydrochemical characterization of parameters in the Odiel River Basin by means of Fuzzy Logic and data mining methodologies to determine the seasonal influence of AMD in polluted waters that have not been used before for a basin in this environmental area. This technique was proven to be effective, providing results that could not be achieved by using classic statistics, because it allows us to characterize the different parameters separately and also their relationships in waters affected by AMD in a qualitative manner based on the antecedents and according to the conditions (rules) imposed by the consequents (in this case, the Fe(II) and accumulated rainfall over 30 days). Thus, it was possible to confirm that hydrochemistry is greatly affected by seasonal changes, with a higher pH in the wet season (up to 8.59) compared to 2.12, the minimum pH value reached in the dry season. Accordingly, higher concentrations of most of the metals were observed in the dry season (e.g., up to 4000 mg/L of Fe (II)), with the exception of the values found after the first rains that occur in the early fall. With the use of the Fuzzy Logic technique, it was observed that, during the wet season, lixiviates with a higher Fe content have higher metal concentrations, and in the dry season, the behavior is the opposite.

Trees as sentinels of metallic pollution induced by mining along the Odiel River (Southern Iberian Peninsula)

Mining activity is often responsible for the drainage of acid or metal-enriched waters to fluvial systems. The release of metals is especially disturbing due to the toxicity and persistence of these products and their accumulation in the biosphere. Hence, a systematic detection and delimitation of highly polluted floodplains and linkages between pollution and high-flow stages would likely assist the improvement of land management and ease the design of mitigation or rehabilitation measures. Here we test how trees growing in different geomorphic positions along a fluvial system uptake metal during floods and how these uptakes can be documented “a posteriori”. To this end, we apply dendrogeochemical analyses to twenty Pinus pinaster Ait. trees growing on the banks of Odiel River (south-western Spain) as well as to five reference trees growing outside the river channel. In the field, trees were sampled with a large-diameter (1 cm) increment borer. In the lab, tree-ring series were dendrochronologically cross dated and separated into 5-yr blocks, so that wood blocks contained the dates of major floods. Then, Inductively Coupled Plasma Mass Spectrometry (ICPM) was employed to evaluate toxic metal concentrations in trees. Results point to clear correlations between the accumulation of toxic metals and the geomorphic position of trees within the fluvial network. We show that morphological units along a river exert control on toxic metal concentrations in trees, with uptake being much higher in trees located on meander cut banks than in trees growing on point-bar structures. Besides, we detect chemical signatures in trees located farthest away from the main river channel after the largest floods, but not in the aftermath of smaller events. We conclude that tree position is the single-most important determinant for metallic pollution in an environment controlled by fluvial processes, but also find that more studies are still needed to determine linkages with individual floods and interactions of metal uptake in roots via the water table in the river corridor.

Antioxidant, Antimicrobial, and Bioactive Potential of Two New Haloarchaeal Strains Isolated from Odiel Salterns (Southwest Spain)

The need to survive in extreme environments has furnished haloarchaea with a series of components specially adapted to work in such conditions. The possible application of these molecules in the pharmaceutical and industrial fields has received increasing attention; however, many potential bioactivities of haloarchaea are still poorly explored. In this paper, we describe the isolation and identification of two new haloarchaeal strains from the saltern ponds located in the marshlands of the Odiel River, in the southwest of Spain, as well as the in vitro assessment of their antioxidant, antimicrobial, and bioactive properties. The acetone extract obtained from the new isolated Haloarcula strain exhibited the highest antioxidant activity, while the acetone extracts from both isolated strains demonstrated a strong antimicrobial activity, especially against other halophilic microorganisms. Moreover, these extracts showed a remarkable ability to inhibit the enzyme cyclooxygenase-2 and to activate the melanogenic enzyme tyrosinase, indicating their potential against chronic inflammation and skin pigmentation disorders. Finally, the aqueous protein-rich extracts obtained from both haloarchaea exhibited an important inhibitory effect on the activity of the acetylcholinesterase enzyme, involved in the hydrolysis of cholinergic neurotransmitters and related to several neurological diseases.

Trees as sensors of metallic pollution dissemination during past flood events

<p>Anthropogenic activities such as mining are responsible for acid drainage and metal-enriched waters that in turn contaminate river ecosystem downstream due to the weathering of exposed minerals or tailing dam failures. The release of heavy metals is especially disturbing because of their high toxicity and long permanence. Detecting highly polluted areas and their links with high (low) water flow stages can contribute to a better land management of affected areas. Here, we test if trees growing in different geomorphic positions along a river record heavy metal uptake during past floods. To this end, we applied dendrochemical analysis to twenty-five <em>Pinus pinaster</em> Ait. growing on the banks of Odiel River flowing into the Atlantic Ocean located at in south-western Spain. In addition, five trees disconnected from the river channel were sampled as references values. For each tree, we extracted 1 cm-sized increment cores. After dating dendrochronologically, we isolated tree-ring sequences into 5-year blocks matching with the dates of major floods in the catchments. Samples were then analyzed using an Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our results suggest coherence between tree locations and the amount of heavy metal accumulated in the tree over the last decades. Thus, we clearly show a control of river morphological units on the  heavy metal concentrations in trees, being higher in those trees located on meander cut banks than in trees on point-bar sedimentary structures. We conclude that trees could be a natural proxy to trace chemical dispersion and pollution related to flood events in highly anthropogenic catchments.</p>