Search

Underground mine drainages are extremely difficult to study due to the lack of information about the flow path and source proximity in relation to the outflow adit. Geochemical processes controlling metals and acidity fluxes in a complex anthropogenic mine aquifer in SW Spain during the dry and rainy season were investigated by geochemical and statistical tools. High concentrations of acidity, sulfate, metals and metalloids (e.g. Fe, Cu, Zn, As, Cd, Ni, Co) were observed due to intense sulfide oxidation processes. The high residence time inside the anthropogenic aquifer, around 40 days, caused the release of significant quantities of metals linked to host rocks (e.g. Al, Ca, Ge, Li, Mg, REE). The most outstanding characteristic of the acid mine drainage (AMD) outflows is the existence of higher Fe/SO 4 molar ratios than those theoretical of pyrite (0.50) during most of the monitored period, due to a fire which occurred in 1949 and remained active for decades. Permanent and temporal retention mechanisms of acidity and metals were observed in the galleries. Once released from sulfide oxidation, Pb and As are sorbed on Fe oxyhydroxysulfate or precipitated as low solubility minerals (i.e. anglesite) inside the galleries. The precipitation of evaporitic sulfate salts during the dry season and the subsequent re-dissolution after rainfall control the fluxes of acidity and main metals (i.e. Fe, Mg, Al) from this anthropogenic aquifer. Some elements, such as Cd, Cu, Ni, REE and Zn, are retained in highly soluble sulfate salts while other elements, such as Ge, Pb and Sc, have a lower response to washout processes due to its incorporation in less soluble sulfate salts. In this way, metal concentration during the washout processes would be controlled by the proportion and solubility of each type of evaporitic sulfate salt stored during the dry season. The recovery of metals of economic interest contained in the AMD could help to self-finance the remediation of these waters in derelict mines worldwide. [ABSTRACT FROM AUTHOR]

Abstract: A 2month long column study was conducted to evaluate the mobility of heavy metals eluting from Technosols constituted from sewage sludges (aerobic or anaerobic) (as controls) or a mixture of different types of sewage sludges with green foundry sand (FS) or/and Linz–Donowitz slag (LD). The organic and inorganic wastes were mixed at a ratio of 56:44 (w/w). The mixtures and the controls were moistened to field capacity before adding them to the polypropylene columns (4.5cm wide and 14cm long). During the 8-week experimental period, the columns were watered, twice a week, with 100mL of deionised water. The concentrations of heavy metals (Cu, Zn, Ni, Pb, Cd, and Cr) in the leachates were determined periodically. The concentrations of all the heavy metals were generally higher in the leachates from the Technosols containing anaerobic sewage sludge as a component. The concentration of Cu was strongly dependent on pH and was significantly higher (P <0.05) in the most alkaline leachates (pH>10) than in the other leachates. More Zn was mobilized in the most acidic leachates (pH<6) than in other leachates. The concentration of Ni in 80% of the leachates exceeded the EU drinking water limit for Ni (0.02mgL−1). The concentrations of Pb were lower in the Technosols containing FS. The concentrations of Cd in the leachates from Technosols containing the conditioners were relatively high, while concentrations of Cr were higher in the controls. As far as the potential toxicity of heavy metals is concerned, the combination of aerobic sludge, inorganic conditioners able to buffer the pH to around neutrality, and reactive aluminosilicates, can be regarded as suitable choice for formulating Technosols from wastes. [Copyright &y& Elsevier]

The preparation of tailor-made Technosols from wastes may be a novel and prospective option for the re-use of wastes and restoration of degraded areas. A two-month study with pilot columns was conducted to evaluate the influence of the acid buffering capacity of different Technosols on the chemistry of their leachates. The Technosols were made from mixtures of organic and inorganic wastes at a ratio of 56:44 (w/w). The organic components used were an anaerobic (AN) and an aerobic (AE) sewage sludge. The inorganic wastes used – referred to as “conditioners” – were Linz-Donowitz slag (LD) and foundry sand (FS). A mixture of the two conditioners at a ratio of 50:50 (w/w) was made to provide a third type of conditioner (LD+FS). Controls consisted of columns filled with organic waste only (either AN or AE sludges). Changes in pH, electrical conductivity, concentrations of major ions and dissolved organic carbon in the leachates were evaluated periodically. The main processes determining the pH of the systems were nitrification and leaching, but organic matter decomposition and carbonation may also have had an influence. Nitrification was strongly retarded in the AN sludge (attributed to the probable absence of nitrifiers in this waste after the AN wastewater treatment) and was impeded in those mixtures in which LD was used as a component (due to the liming effect). Final pH values ranged from 5.0 and 5.4 (in AE and AE+FS, respectively) to 11.1 (in AN+LD). The pH of the other mixtures finally ranged between 7 and 8. In formulating mixtures of wastes, their acid buffering capacity should be taken into account in addition to the nutrient contents and the limits of contaminants established by local regulations. [Copyright &y& Elsevier]

This paper explores the possibility of using wastes (i.e. solid phosphogypsum (PG), process waters and edge outflows) generated by a fertilizer plant in SW Spain as a source of elements of economic interest, estimating the available metal reserves and discussing the technological and economic pros and cons of this potential source of raw materials. In general, elements of economic interest are found in these wastes below of the grades commonly reported in conventional deposits. However, the huge tonnage of wastes stockpiled constitutes a significant secondary source of elements. Around 30,400 t of B, 28,000 t of rare earth elements (REE), 1800 t of U, 1400 t of Cr, 1300 t of V and lesser amounts of other elements of economic interest (e.g. Cu, Ni, Sc and Ga) are enclosed in the solid PG while lower amounts are found in process waters (e.g. 1360 t of Zn, 760 t of V, 630 t of U and Cr, 225 t of Cu, 160 t of Ni, 190 t of REE). Considering the market metal prices, the reserves contained in the Huelva PG stack have a potential value of around 8937 million USD, which mainly correspond to PG (97% of total value). The recovery of these elements is technically feasible, although intense research in refining processes is needed in order to increase the purity of the final product. The results of this study could be of interest in other PG stacks worldwide to provide more sustainable and cost-effective management of these wastes. [ABSTRACT FROM AUTHOR]

Abstract: Persistent organic pollutants (POPs) are within the most dangerous pollutants released into the environment by human activities. Due to their resistance to degradation (chemical, biological or photolytic), it is critical to assess the fate and environmental hazards of the exchange of POPs between different environmental media. System Dynamics enables to represent complex systems and analyze their dynamic behavior. It provides a highly visual representation of the structure of the system and the existing relationships between the several parameters and variables, facilitating the understanding of the behavior of the system. In the present study the fate of γ-hexachlorocyclohexane (lindane) in a contaminated soil was modeled using the Vensim® simulation software. Results show a gradual decrease in the lindane content in the soil during a simulation period of 10years. The most important route affecting the concentrations of the contaminant was the biochemical degradation, followed by infiltration and hydrodynamic dispersion. The model appeared to be highly sensitive to the half-life of the pollutant, which value depends on environmental conditions and directly affects the biochemical degradation. [Copyright &y& Elsevier]

Abstract: The aim of the present study was to select candidate plant species for phytoremediation of soils contaminated with hexachlorocyclohexane (HCH). For this purpose, an experiment was carried out under controlled conditions of germination and growth, with nine plant species of economic and/or agricultural interest, in a soil contaminated with a heterogeneous mixture (at eight different levels of contamination) of the main HCH isomers (α-, β-, γ- and δ-HCH). The results revealed differences in the plant responses to the control soil and the soils containing HCH. Germination was not as strongly affected as other parameters such as the rate of germination and seedling vigour. In general, all of the species displayed signs of stress in response to the presence of HCH, although to different degrees. Some of the species used in the experiment (Hordeum vulgare L., Brassica sp., Phaseoulus vulgaris L.) were capable of mitigating the negative effects of HCH, and displayed a certain degree of resistance, as their biomass production was not greatly affected by the contaminant. These (tolerant) plants therefore appear to be ideal for phytoremediation purposes. [Copyright &y& Elsevier]

Objectives: Good syndrome is a rare condition in which a thymoma is associated with hypogammaglobulinemia. It is also characterized by low or absent B-cells, CD4+ T-cell lymphopenia, inverted CD4/CD8+ T-cell relation, and repeated bacterial, viral, and fungal infections, as well as with various autoimmune disorders. Case report: We report the case of a 62-year-old female patient who after resection of a thymoma developed constipation and recurrent lower respiratory and urinary tract infections. She underwent left hemicolectomy as well as symptomatic and antibiotic treatment. Two years later the patient develops refractory anemia; a bone marrow biopsy shows hypo-cellularity and no red cell precursors with negative CD 71 staining. The diagnosis of pure red cell precursor aplasia (PRCA) is made. Recurrent bacterial infections of the respiratory and urinary tracts continue, and therefore treatment with G and A immunoglobulins starts. Finally, the absence of B lymphocytes and inversion of CD4/CD8 relation confirms the diagnosis of Good syndrome associated with PRCA. Discussion: The discovery of Good Syndrome and PRCA after the resection of a thymoma, as seen in the current case, is very unusual. This case illustrates both the rareness presentation of Good syndrome with PRCA and the persistent infections seen in these patients. Early recognition of these entities results in lower mortality and morbidity. [ABSTRACT FROM AUTHOR]

Abstract: Although there are many studies on the characterization of C in biochar and its C sequestration potential, there is little knowledge on the mineral fraction in biochar and its weathering. The latter, however, can have powerful implications on nutrient availability. In the present study, a modified Soxhlet reactor was used to simulate the long-term geochemical weathering of an ash-rich biochar produced from sewage sludge of a non-industrial area in New Zealand. The weathering process took place during a period of 300h, with and without the addition of humic acid (1.00g added to 20.00g of biochar), and the treatments were referred to as treatment BC-HA and BC-B, respectively. Both the leaching kinetics and the transformations within the solid phase were studied. The results revealed that substantial amounts of K (8.5–10.2%) and S (20.2–28.3%) were recovered in the weathering solutions. Noticeable Ca (17.9–20.7%) and P (15.4%) in the solid were released but only a few were recovered in the weathering solutions because of the precipitation. The presence of humic acids increased this dissolution and thus the availability of K, S, Ca, Mg and P, but induced N immobilization. Nitrogen availability was already very low (<1.0% of the total N) due to the probable recalcitrant heterocyclic N structure. The pH of the biochar samples dropped from 8.4 to 7.5; this was mainly attributed to loss of base cations through leaching and probable carbonation of the system. The XPS spectra evidenced the oxidation of C in biochar during the weathering process with the formation of carbonyl and carboxylic functional groups. The results obtained in this study showed some promise for the positive use of modified Soxhlet extractor in simulating the geochemical weathering in ash-rich biochars and providing a better understanding on the kinetics of nutrient release. This will be key information in assessing the added value of biochars as soil amendments. [ABSTRACT FROM AUTHOR]