Fuzzy Logic Tools Application to the Characterization of Stress-Strain Processes in Waste Construction Dam Geopolymers: A New Circular Mining.

The ceramics industry dedicated to the manufacture of building materials is a very significant cause of environmental pollution, and various research projects are being carried out to reduce the associated environmental impact. One of the most important research lines is the generation and development of new materials, from waste, through more sustainable production processes. All of this is framed in circular mining. In this research study, geopolymers were developed with biomass bottom ashes and brick dust in order to replace the traditional ceramics used to construct bricks. For this, different families of test tubes were formed with different percentages of both residues, and their physical and mechanical properties were studied. In this way, the properties of geopolymers could be compared with traditional ceramics. In addition, in order to determine the cause-effect relationships between physical properties and compressive strength, data were processed using fuzzy logic and data mining techniques. The results showed the feasibility of geopolymers generation with biomass bottom ashes and brick dust with acceptable properties to replace conventional ceramics. In addition, the fuzzy logic analysis allowed for establishing clear and objective relationships between the physical properties and the compressive strength of the geopolymers, with the aim of developing the highest quality geopolymer.

Acid Mine Drainage Effects in the Hydrobiology of Freshwater Streams from Three Mining Areas (SW Portugal): A Statistical Approach.

Aljustrel, Lousal and S. Domingos mines are located in the Iberian Pyrite Belt (IPB), one of the greatest massive sulfide ore deposits worldwide. These mines' surrounding streams are affected by Acid Mine Drainage (AMD). The main purpose of this study was to understand AMD influence in the water quality and diatom behavior. Thus, waters and diatoms were sampled in 6 sites from the 3 selected mines on winter and summer of 2016. The highest concentrations were found in acidic sites: A3 (Aljustrel-Al, Cd, Cu, Fe and Zn (and lowest pH)) and L1 (Lousal-As, Mn, Ca, Mg, SO42- and conductivity). The most abundant diatom species was Pinnularia aljustrelica with 100% of dominance in A3 and S1 acidic sites, which puts in evidence this species adaptation to AMD harsh conditions. Multivariate cluster analysis allowed us to reinforce results from previous studies, where spatial differences were more relevant than seasonal ones. In 12 years (2004-2016), and with many transformations undertaken (re-opening and rehabilitation), there is a conservative behavior in the biological species (diatoms) and physicochemical concentrations (metals, pH and sulfates) from these three mining sites. This type of biogeochemical diagnosis is necessary for the sustainable use of these waters and the prevention of the polluting process, aimed to protect the water ecosystem and its biodiversity.

Biogeochemical indicators (waters/diatoms) of acid mine drainage pollution in the Odiel river (Iberian Pyritic Belt, SW Spain).

Odiel river basin is located in the Iberian Pyritic Belt (IPB) and mostly of its tributaries are severely affected by acid mine drainage (AMD). It is originated when pyritic minerals from abandoned mines, especially mineral residues from waste rock dams, get in contact with air and water. Fifteen sampling points were chosen to analyze interactions between diatom communities and water hydrogeochemistry. Considering physicochemical characteristics, sampling points were assigned as highly, moderately, and unpolluted by AMD. No correlation was observed between ecological diversity indexes and physico-chemical parameters. However, a dependency relationship between diatom species distribution and specific pH, conductivity, redox potential, sulfate, and metal concentrations was observed. Cluster analysis based on Pearson correlation and rs values of the non-parametric Spearman correlation allowed to identify Pinnularia acidophila, Pinnularia subcapitata var. elongata, and Eunotia exigua as the main bioindicators of AMD-polluted Odiel streams. Finally, a principal component analysis led to associate the most abundant diatoms species to specific physico-chemical parameters.

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.

Extremely Acidic Eukaryotic (Micro) Organisms: Life in Acid Mine Drainage Polluted Environments-Mini-Review.

Acid Mine Drainage (AMD) results from sulfide oxidation, which incorporates hydrogen ions, sulfate, and metals/metalloids into the aquatic environment, allowing fixation, bioaccumulation and biomagnification of pollutants in the aquatic food chain. Acidic leachates from waste rock dams from pyritic and (to a lesser extent) coal mining are the main foci of Acid Mine Drainage (AMD) production. When AMD is incorporated into rivers, notable changes in water hydro-geochemistry and biota are observed. There is a high interest in the biodiversity of this type of extreme environments for several reasons. Studies indicate that extreme acid environments may reflect early Earth conditions, and are thus, suitable for astrobiological experiments as acidophilic microorganisms survive on the sulfates and iron oxides in AMD-contaminated waters/sediments, an analogous environment to Mars; other reasons are related to the biotechnological potential of extremophiles. In addition, AMD is responsible for decreasing the diversity and abundance of different taxa, as well as for selecting the most well-adapted species to these toxic conditions. Acidophilic and acidotolerant eukaryotic microorganisms are mostly composed by algae (diatoms and unicellular and filamentous algae), protozoa, fungi and fungi-like protists, and unsegmented pseudocoelomata animals such as Rotifera and micro-macroinvertebrates. In this work, a literature review summarizing the most recent studies on eukaryotic organisms and micro-organisms in Acid Mine Drainage-affected environments is elaborated.

Acid Mine Drainage as Energizing Microbial Niches for the Formation of Iron Stromatolites: The Tintillo River in Southwest Spain.

The Iberian Pyrite Belt in southwest Spain hosts some of the largest and diverse extreme acidic environments with textural variation across rapidly changing biogeochemical gradients at multiple scales. After almost three decades of studies, mostly focused on molecular evolution and metagenomics, there is an increasing awareness of the multidisciplinary potential of these types of settings, especially for astrobiology. Since modern automatized exploration on extraterrestrial surfaces is essentially based on the morphological recognition of biosignatures, a macroscopic characterization of such sedimentary extreme environments and how they look is crucial to identify life properties, but it is a perspective that most molecular approaches frequently miss. Although acid mine drainage (AMD) systems are toxic and contaminated, they offer at the same time the bioengineering tools for natural remediation strategies. This work presents a biosedimentological characterization of the clastic iron stromatolites in the Tintillo river. They occur as laminated terraced iron formations that are the most distinctive sedimentary facies at the Tintillo river, which is polluted by AMD. Iron stromatolites originate from fluvial abiotic factors that interact with biological zonation. The authigenic precipitation of schwertmannite and jarosite results from microbial-mineral interactions between mineral and organic matrices. The Tintillo iron stromatolites are composed of bacterial filaments and diatoms as Nitzschia aurariae, Pinnularia aljustrelica, Stauroneis kriegeri, and Fragilaria sp. Furthermore, the active biosorption and bioleaching of sulfur are suggested by the black and white coloration of microbial filaments inside stromatolites. AMD systems are hazardous due to physical, chemical, and biological agents, but they also provide biogeochemical sources with which to infer past geochemical conditions on Earth and inform exploration efforts on extraterrestrial surfaces in the future.

Physico-Chemical Influence of Surface Water Contaminated by Acid Mine Drainage on the Populations of Diatoms in Dams (Iberian Pyrite Belt, SW Spain).

Twenty-three water dams located in the Iberian Pyrite Belt were studied during March 2012 (early spring) in order to carry out an environmental assessment based on diatom communities and to define the relationships between these biological communities and the physico-chemical characteristics of the dam surface water. This is the first time that a diatom inventory has been done for dams affected by acid mine drainage (AMD) in the Spanish part of the Iberian Pyrite Belt (IPB). It was found that the pH was the main factor influencing the behaviour of the diatom communities. Then, using a dbRDA approach it was possible to organize the aggrupation of diatoms into four groups in response to the physico-chemical conditions of the ecosystem, especially pH: (1) Maris, Aac, Gos, Cmora (pH 2-3); (2) Andc, San, And, Dpin (pH 3-4.5); (3) Gran, Pleon, Oliv, Lagu, Chan, SilI, SilII, Joya, Gar, Agrio, Camp, Corum (pH 4.5-6); (4) Herr, Diq I, Diq II (pH 6-7). The obtained results confirmed the response of benthic diatom communities to changes in the physico-chemical characteristics of surface water, and helped to understand the role of diatoms as indicators of the degree of AMD contamination in those 23 dams. Special attention was given to those that have an acidophilic or acid-tolerant profile (pH 2-3 and pH 3-4.5) such as Pinnularia aljustrelica, Pinnularia acidophila, Pinnularia acoricola and Eunotia exigua, which are the two groups found in the most AMD contaminated dams.

Extremely acidic environment: Biogeochemical effects on algal biofilms.

The biological responses of acidobiontic species to extremely acidic waters, as those related with Acid Mine Drainage (AMD) processes, are relevant not only to understand the toxicological degree of the waters as well as the mechanisms responsible for the survival and adaptation of such organisms. Therefore, the objective of this study was to evaluate the effect of acidic pH and metals in biofilms collected in two sites a lentic permanent acid pond (AP) and a temporary acid stream (AS) affected by Acid Mine Drainage (AMD), and taking as control (C), an uncontaminated site with circumneutral pH. The results showed typical conditions of AMD-contaminated waters in sites AS and AP (pH < 3 and high concentrations of Al, Cu, Fe, Mn, Pb and Zn), which are responsible for a substantial decrease in biomass and biodiversity of biofilms (with a dominance of acidobiontic species, such as Pinnularia aljustrelica and Eunotia exigua, comparing to the control site. Also expressed by low values of photosynthetic pigments and reduced amount of proteins. In addition, such extreme acidic conditions also induced biofilms' stress, increasing antioxidant [catalase (CAT), superoxide dismutase (SOD) and biotransformation glutathione S-transferases (GSTs)] enzymes activity and also membrane damage (peroxidized lipids). However, despite the quite similar physico-chemical conditions of both AMD-contaminated sites, differences in the toxicity status between them were indirectly detected through some of the biochemical parameters [GSTs, SOD and CAT], indicating site AS has the most toxic, which fact was attributed to the higher concentrations of Pb2+ in this water. This element is recognized to be highly toxic for biota, and in such acidic conditions remains in solution, easily available to the aquatic organisms. Since pH is similar in the acid sites, the different concentrations of heavy metals in the waters might be responsible for the observed changes in the biological community at these two sites. This fact was translated in a higher capacity of this site's biofilm to cope with the negative effects of the toxicants, evidenced in a higher positive correlation with GSTs, CAT and SOD when compared to biofilms of sites AP and C.

Integrating geochemical (surface waters, stream sediments) and biological (diatoms) approaches to assess AMD environmental impact in a pyritic mining area: Aljustrel (Alentejo, Portugal).

Aljustrel mines were classified as having high environmental hazard due to their large tailings volume and high metal concentrations in waters and sediments. To assess acid mine drainage impacted systems whose environmental conditions change quickly, the use of biological indicators with short generation time such as diatoms is advantageous. This study combined geochemical and diatom data, whose results were highlighted in 3 groups: Group 1, with low pH (1.9-5.1) and high metal/metalloid (Al, As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn; 0.65-1032 mg/L) and SO4 (405-39124 mg/L) concentrations. An acidophilic species, Pinnularia aljustrelica, was perfectly adapted to the adverse conditions; in contrast, teratological forms of Eunotia exigua were found, showing that metal toxicity affected this species. The low availability of metals/metalloids in sediments of this group indicates that metals/metalloids of the exchangeable fractions had been solubilized, which in fact enables metal/metalloid diatom uptake and consequently the occurrence of teratologies; Group 2, with sites of near neutral pH (5.0-6.8) and intermediate metal/metalloid (0.002-6 mg/L) and SO4 (302-2179 mg/L) concentrations; this enabled the existence of typical species of uncontaminated streams (Brachysira neglectissima, Achnanthidium minutissimum); Group 3, with samples from unimpacted sites, showing low metal/metalloid (0-0.8 mg/L) and SO4 (10-315 mg/L) concentrations, high pH (7.0-8.4) and Cl contents (10-2119 mg/L) and the presence of brackish to marine species (Entomoneis paludosa). For similar conditions of acidity, differences in diversity, abundance and teratologies of diatoms can be explained by the levels of metals/metalloids.

Experimental evaluation of the contribution of acidic pH and Fe concentration to the structure, function and tolerance to metals (Cu and Zn) exposure in fluvial biofilms.

An indoor channel system was colonised with fluvial biofilms to study the chronic effects of high Fe and SO4(2-) concentrations and acidic pH, the water chemistry in the surrounding streams of Aljustrel mining area (Alentejo, Portugal), and their contribution to community (in)tolerance to metal toxicity by short-term experiments with Cu and Zn. Biofilms were subjected to four different treatments during 8 weeks: high Fe and SO4(2-) concentrations (1 mg Fe l(-1)+ 700 mg SO4(2-) l(-1)) and acidic pH, high Fe and SO4(2-) at alkaline pH; lower Fe and SO4(2-) at acidic pH: and lower Fe and SO4(2-) concentrations at alkaline pH as negative control. During chronic exposure, acidic pH affected growth negatively, based on low values of algal biomass and the autotrophic index, high values of the antioxidant enzyme activities and low diversity diatom communities, dominated by acidophilic species (Pinnularia aljustrelica) in acidic treatments, being the effects more marked with high Fe and SO4(2-). Co-tolerance to metals (Cu and Zn) was also shown in biofilms from the acidic treatments, contrasting with the higher sensitivity observed in the alkaline treatments. We can conclude that the Aljustrel mining area acidic environment limits algal growth and exerts a strong selection pressure on the community composition which is in turn, more tolerant to metal exposure.

Environmental impact of mining activities in the Lousal area (Portugal): chemical and diatom characterization of metal-contaminated stream sediments and surface water of Corona stream.

Lousal mine is a typical "abandoned mine" with all sorts of problems as consequence of the cessation of the mining activity and lack of infrastructure maintenance. The mine is closed at present, but the heavy metal enriched tailings remain at the surface in oxidizing conditions. Surface water and stream sediments revealed much higher concentrations than the local geochemical background values, which the "Contaminated Sediment Standing Team" classifies as very toxic. High concentrations of Cu, Pb, Zn, As, Cd and Hg occurred within the stream sediments downstream of the tailings sites (up to: 817 mg kg(-1) As, 6.7 mg kg(-1) Cd, 1568 mg kg(-1) Cu, 1059 mg kg(-1) Pb, 82.4 mg kg(-1) Sb, 4373 mg kg(-1) Zn). The AMD waters showed values of pH ranging from 1.9 to 2.9 and concentrations of 9249 to 20,700 mg L(-1) SO(4)(-2), 959 to 4830 mg L(-1) Fe and 136 to 624 mg L(-1) Al. Meanwhile, the acid effluents and mixed stream waters also carried high contents of SO(4)(2-,) Fe, Al, Cu, Pb, Zn, Cd, and As, generally exceeding the Fresh Water Aquatic Life Acute Criteria. Negative impacts in the diatom communities growing at different sites along a strong metal pollution gradient were shown through Canonical Correspondence Analysis: in the sites influenced by Acid Mine Drainage (AMD), the dominant taxon was Achnanthidium minutissimum. However, Pinnularia acoricola was the dominant species when the environmental conditions were extremely adverse: very low pH and high metal concentrations (sites 2 and 3). Teratological forms of Achnanthidium minutissimum (Kützing) Czarnecki, Brachysira vitrea (Grunow) Ross in Hartley, Fragilaria rumpens (Kützing) G. W. F. Carlson and Nitzschia hantzschiana Rabenhorst were found. A morphometric study of B. vitrea showed that a decrease in size was evident at the most contaminated sites. These results are evidence of metal and acidic pollution.