Modelos de funcionamiento hidrogeoquímico de embalses afectados por AMD en base a indicadores biológicos. Interés y relevancia de las diatomeas en el caso de la Faja Pirítica Ibérica

Zusammenfassung

The construction of dams in regions subject to arid climates is a technique commonly used to store water for later urban, agricultural and industrial use. In the study scenario, southwest of Spain, the average annual rainfall is around 600 mm and the ETP around 900 mm, which causes a negative water balance that justifies the need for construction, quality control and maintenance of these reservoirs. The quality of these waters depends on the physical-chemical and biological characteristics of each dam, in turn dependent on the sources of pollution present in each catchment basin and on climatic variables that also influence the biota present in water ecosystems and on the physical-chemical of the water itself. In this sense, the Water Framework Directive, 2000/60/EC defines limits and proposes the use of diatoms as bioindicators of surface waters ecological status as it’s said there, “they are the most effective indicators”. In the SW of the peninsula, where this Doctoral Thesis was realized, there are more than 80 sulfide exploitations, most of them abandoned and without prevention or correction measures because they began exploitation prior to the entry into force of the environmental regulations that currently impose "zero discharge" for the sulphide mines. These mines, abandoned and closed hundreds or thousands of years ago, continue to be polluting sources nowadays, due to lack of preventive measures. This fact forms an unique hydric scenario where the Acid Mine Drainage caused by the oxidation of sulphides into sulphates releases hydrogen ions (H+) causing the appearance of waters of extreme acidity that are capable of dissolving the metals present in the environment. The end result is a leachate of very low pH and very high concentrations of sulphates and heavy metals dissolved in their waters, that make it unsuitable for any other use than mining. Based on the above, this work addresses the physical-chemical and biological characteristics of the waters from 23 reservoirs, affected to a greater or lesser extent within the Iberian Pyrite Belt in order to identify the diatoms present in their waters, the variables that define their physical-chemical characteristics and the climate, in turn modeling the interrelationships between these groups of variables. To achieve the objectives described, the sampling and analysis of water representative of the river network, from a total of 23 dams, crossing the Iberian Pyrite Belt, was done. The diatom species present at each dam were identified and these data was integrated, together with the climatic ones, in compatibles matrices done with different software. The application of fuzzy logic tools allowed the classification of dams accordingly to the pollution degree based on bioindicators, the interdependence relationships between richness, diversity of species, pH and dissolved metals, the contrast with proposals of other authors for similar scenarios first, through the implementation of graphical treatment, followed by traditional statistic and finally through fuzzy logic with the use of the Pre-Fur-Ge tool, the fundamental role of pH as a pre-indicator of biota specific tolerance with a precise indication of existence/coexistence ranges of diatom species. In addition, this work highlights the fact that is the first work in the scientific literature, describing the dams of an entire metallogenetic province in an all country. Different works emerged from this doctoral thesis, published in indexed journals. We highlight the followings: Valente et al., 2013; Valente et al., 2014; Valente et al., 2015; Valente et al., 2016; Rivera et al., 2019; Rivera et al., 2020.