Environmental and sanitary conditions of guanabara bay, Rio de Janeiro

Guanabara Bay is the second largest bay in the coast of Brazil, with an area of 384 km2. In its surroundings live circa 16 million inhabitants, out of which 6 million live in Rio de Janeiro city, one of the largest cities of the country, and the host of the 2016 Olympic Games. Anthropogenic interference in Guanabara Bay area started early in the XVI century, but environmental impacts escalated from 1930, when this region underwent an industrialization process. Herein we present an overview of the current environmental and sanitary conditions of Guanabara Bay, a consequence of all these decades of impacts. We will focus on microbial communities, how they may affect higher trophic levels of the aquatic community and also human health. The anthropogenic impacts in the bay are flagged by heavy eutrophication and by the emergence of pathogenic microorganisms that are either carried by domestic and/or hospital waste (e.g., virus, KPC-producing bacteria, and fecal coliforms), or that proliferate in such conditions (e.g., vibrios). Antibiotic resistance genes are commonly found in metagenomes of Guanabara Bay planktonic microorganisms. Furthermore, eutrophication results in recurrent algal blooms, with signs of a shift toward flagellated, mixotrophic groups, including several potentially harmful species. A recent large-scale fish kill episode, and a long trend decrease in fish stocks also reflects the bay’s degraded water quality. Although pollution of Guanabara Bay is not a recent problem, the hosting of the 2016 Olympic Games propelled the government to launch a series of plans to restore the bay’s water quality. If all plans are fully implemented, the restoration of Guanabara Bay and its shores may be one of the best legacies of the Olympic Games in Rio de Janeiro

Pit lakes from Southern Sweden: natural radioactivity and elementary characterization

Natural radioactivity in the environment is a field gaining more attention in last decades. This work is focused on the study of natural radioactivity complemented with elementary characterization at former non‑uraniferous mining areas in Sweden. This aim is addressed through the study of mining lakes, called pit lakes, which are water bodies generated after opencast mining. Environmental matrices (water, sediments and rocks) from 32 Swedish pit lakes, commonly used for recreational purposes were radiometrically characterized via alpha (238U, 234U, 232Th, 230Th, 210Po isotopes) and gamma spectrometry (238U and 232Th series radionuclides). Additionally, ambient dose rate equivalent in the immediate surrounding of each pit lake was quantified. Physico‑chemical parameters (pH, specific conductivity, dissolved oxygen, oxidation–reduction potential) and elemental composition (major and trace elements by ICP‑MS) were analysed in water samples and elementary composition of sediments/rocks was measured by XRF and SEM–EDX in some specific cases. A non‑negligible number of pit lakes (26%) with enhanced U levels in water was found. At some sites, rocks contained up to 4% of U in areas with high degree of interaction with local population. Concerning the elementary perspective, another popular site (due to its turquoise water) was found to have elevated dissolved heavy metal levels. Results obtained in this work prove that measurement of natural radioactivity is another component that should be included in routine analysis of characterization in mining areas, especially if restauration of post‑mining sites is intended for human recreational.Work supported by the Swedish Radiation Safety Authority (SSM2014-3485). The authors thank Dr. Ana Calleja at Radioisotopes Laboratory (ICP-MS measurements) and the X-Ray Laboratory staff (XRF measurements), both from CITIUS facilities at the University of Seville. Furthermore, the Applied Nuclear Physics Group at the University of Seville, is also acknowledged for its continuous technical support during the different stages of this project. Open access funding provided by University of Gothenbur

Partition of Rare Earth Elements Between Sulfate Salts Formed by the Evaporation of Acid Mine Drainage

Acid mine drainage (AMD) contains rare earth element (REE) concentrations several orders of magnitude higher than those of the rest of natural waters and could be a secondary source of REEs. In arid to semiarid climates with a long dry season, the precipitation of efflorescent sulfates constitutes a transient storage of REEs. The REE partition among the Al–Fe–Mg–Ca sulfates formed by the evaporation to dryness of six different AMDs was investigated by statistical methods and by selective dissolution. The chemical composition of the evaporitic salts showed that only three principal components (PCs) could explain more than 80% of the variability in the six samples analyzed. PC1 was associated with Ca and light REEs and interpreted as gypsum, whereas PC2 was associated with Y and heavy REEs, which were not clearly associated with a major sulfate. Finally, PC3 included Mg, Fe and several transition metals (Cu, Ni, Co, Mn and Zn) and was interpreted as Fe(II)-Mg sulfates. Selective dissolution of the salt mixtures with solutions saturated in the major sulfates revealed that the REEs were only retained in gypsum and were practically absent from the rest of the sulfates. The incorporation of REEs into gypsum decreased from Pr-Nd to La and Lu and was strictly ruled by the differences in their atomic radii and that of Ca in eight-fold coordination. However, gypsum concentrated less than 20% of the REE inventory (< 1% for Sc); the rest probably formed one or more unidentified trace minerals. This indicates that gypsum may not be an efficient way to concentrate REEs from AMD.This work was funded by the European EIT-Raw Materials MORECOVERY and the Spanish SCYRE (CGL2016-78783-C2-R) projects. F. Macías was funded by the R&D FEDER Andalucía 2014-2020 programme through the project RENOVAME (FEDER; UHU-1255729). The authors thank M. Cabañas, R. Bartrolí, and N. Moreno (IDAEA-CSIC) for their analytical assistance, and two anonymous reviewers for their constructive comments.Peer reviewe

Eco-sustainable passive treatment for mine waters: Full-scale and long-term demonstration

This paper tries to analyse the technical and economic performance of a full-scale passive Disperse Alkaline Substrate (DAS) treatment plant steadily operating for 28 months (840 days) to treat extremely acidic and metal rich mine waters in the Iberian Pyrite Belt (SW Spain). For the first time, an economic evaluation of this technology and its comparison with other passive treatments is reported. During this period, around 56,000 m3 of mine waters have been treated, without significant clogging or exhaustion of the alkaline substrate. The efficiency of the system is demonstrated by a significant decrease in the average net acidity (from 2005 to -43 mg/L as CaCO3 equivalent) and the total elimination of Al, Cu, REY, Zn, As, Cr, Mo, V, Cd, Pb, Co and other trace metals. Water quality of the treated output discharge meets the threshold values for irrigation and drinking standards, except for Fe, Mn and sulphate. The accumulation of elements of economic interest in the waste (e.g., 32 t of Fe, 6.1 t of Al, 0.8 t of Cu, 0.8 t of Zn, 39.4 kg of REE, 20 kg of Co or 1 kg of Sc), easily extractable with diluted acids, may turn a hazardous waste into a valuable resource. The benefits associated with the revalorization of this metal-rich waste could reach a total of 27478 USD, but is more reliably estimated to be around 8243 USD due to technologic limitations. This benefit would help to defray the maintenance costs (8428 €) and make DAS an economically self-sustainable treatment. The annual treatment cost for DAS was 0.27 €/m3, being the lowest value found among other reported conventional passive schemes, and from 8 to 12 times lower compared to active technologies. The results obtained prove that the DAS technology is the most technically and economically sustainable way to decontaminate acid and metal-rich mine waters in abandoned mines.This work has been funded by the European EIT-Raw Materials ‘Morecovery’ and the Spanish SCYRE (CGL 2016-78783-C2-1-R) and RENOVAME (FEDER, UHU-1255729) projects. The authors thank to Dr. Chuxia Lin (Associate Editor) and three anonymous reviewers for their helpful comments that notably improved the quality of the original manuscript.Peer reviewe

Mine waters as a secondary source of rare earth elements worldwide: The case of the Iberian Pyrite Belt

Acid Mine Drainage (AMD) generates a great concern worldwide due to its severe impact to water resources during hundreds and even thousands of years after the cessation of mining activity if control measures are not implemented. AMD treatment is an environmental necessity, but also constitute a tremendous opportunity for the valorization of potential secondary sources of elements of economic interest. The knowledge of the hydrogeochemistry of REE in AMDs and their distribution using normalized patterns would help discrimination of the most potentially marketable AMD sources. To achieve this goal and to estimate the total economic potential of a severely AMD-affected region, chemistry and flow data were determined in spatially and temporally-distributed samples of numerous AMD sources collected throughout the Iberian Pyrite Belt (IPB). Due to high anual metal loads of elements such as Al (6600 ton), Zn (1600 ton), Cu (600 ton), Co (26 ton), Ni (10 ton), LREE (10.7 ton/yr), MREE (2.1 ton/yr), HREE (1 ton/yr), Y (3.7 ton) or Sc (0.7 ton), AMDs of the IPB would have an economic potential of 24.1 M$/yr (being REE 22.6$/yr. The magnitude of this economic potential cannot be compared with active mines, however the longevity of the AMD generation processes and the need to achieve an environmental improvement make valorization of these leachates an interesting option to recover metals, which would help to treatment plants costs, improving notably the quality of water bodies in abandoned mining sites.This work was supported by the Spanish Ministry of Economy and Competitiveness through the research projects SCYRE (CGL2016-78783-C2-1-R) and CAPOTE (CGL2017-86050-R); and the MORECOVERY (H2020-EIT-PN 18190) project of the European Institute of Technology Raw Materials programme. F. Macías was funded by the R&D FEDER Andalucía 2014–2020 call through the project RENOVAME (FEDER; UHU-1255729). We would also like to thank Dr. Stefano Albanese (Editor-in-Chief), Dr. Annika Parviainen (Guest Editor) and two anonymous reviewers for the support and suggestions that significantly improved the quality of the original paper.Peer reviewe

Management strategies and valorization for waste sludge from active treatment of extremely metal-polluted acid mine drainage: A contribution for sustainable mining

This study assesses the environmental impact and the potential valorization of metal-sludge waste generated by the active neutralization of extremely metal-polluted acid mine drainage (AMD). To this end, two regulated leaching tests (EN 12457-2 and 1311 USEPA TCLP), a standardized sequential extraction protocol (BCR sequential extraction) and single leaching tests were performed using dilute common industrial acids. The results of the two standardized leaching tests showed a complete discrepancy, classifying the waste as both inert (according to the TCLP) and not suitable for disposal at landfills for hazardous waste (according to EN 12457-2). In this regard, the environmental characterization of the waste using the BCR sequential extraction lined up with interpretations made by the EN 12457-2 leaching test, reinforcing the hazardousness of this type of residue. This waste requires careful management, as evidenced by the release of high concentrations of metals (e.g., Cd, Zn, Al) when interaction with rainfall and organic acids take place, exceeding the risk threshold values for aquatic life. The easy extraction of base, industrial- and tech-metals that is possible with dilute acids encourages the consideration of this type of sludge as an interesting alternative metal source with great economic potential. The joint application of remediation treatments and metal recovery schemes could contribute to the goal of zero waste production in mining activities, which would help to develop sustainable mining practices worldwide

Release of technology critical metals during sulfide oxidation processes: The case of the Poderosa sulfide mine (south-west Spain)

Extensive extraction of technology critical elements (TCEs) from the lithosphere and their use results in a growing dispersion and remobilisation of these elements within the environmental compartments. We investigated the concentration and mobility of different TCEs (rare earth elements (REEs), Sc, Y, Ga and Tl) in acid mine drainage (AMD) outflows from a massive sulfide underground mine in south-west Spain for around 2 years. High levels of TCEs were observed; average concentrations of 8.2 mg L-1 of REEs, 1.5 mg L-1 of Y, 80 g L-1 of Ga, 53 g L-1 of Sc and 42 g L-1 of Tl were reported, several orders of magnitude higher than those observed in natural waters. The TCEs source in the study site is primarily accessory minerals in the host rocks, although the contribution of Ga and Tl by sulfides cannot be discarded. A seasonal variability in TCEs is observed in AMD waters, although their maximum concentrations do not coincide with those of sulfide-related elements. TCEs seem not to be controlled by the precipitation of secondary minerals, but by the intensity of chemical weathering inside the mined zone. A positive correlation between REEs and the Si/Na+K ratio seems to indicate that these elements are linked to resistant minerals to weathering. © 2019 CSIRO.This work was funded by the H2020 EIT Raw Materials program through the project MORECOVERY “Modular recovery services for hydrometallurgy and water treatment (H2020-EIT-PN 18190)” and by the Spanish Ministry of Science, Innovation and Universities through the SCYRE project (CGL2016-78783-C2-R). C.R. Cánovas was funded by the Talent Consolidation Program of the University of Huelva. MD Basallote also thanks the Spanish Ministry of Science, Innovation and Universities for the Postdoctoral Fellowship granted under application reference FJCI-2015-24765.Peer reviewe