Phosphorus removal from eutrophic waters with an aluminium hybrid nanocomposite

An excess of phosphorus (P) is the most common cause of eutrophication of freshwater bodies. Thus, it is imperative to reduce the concentration of P to prevent harmful algal blooms. Moreover, recovery of P has been gaining importance because its natural source will be exhausted in the near future. Therefore, the present work investigated the removal and recovery of phosphate from water using a newly developed hybrid nanocomposite containing aluminium nanoparticles (HPN). The HPN-Pr removes 0.80 ± 0.01 mg P/g in a pH interval between 2.0 and 6.5. The adsorption mechanism was described by a Freundlich adsorption model. The material presented good selectivity for phosphate and can be regenerated using an HCl dilute solution. The factors that contribute most to the attractiveness of HPN-Pr as a phosphate sorbent are its moderate removal capacity, feasible production at industrial scale, reuse after regeneration and recovery of phosphate.The authors acknowledge the Foundation for Science and Technology (FCT) Project SFRH/BD/39085/2007 for the financial support

Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity mechanisms of these metals and their interaction with rising temperature

Metabolism-dependent bioaccumulation of uranium by Rhodosporidium toruloides isolated from the flooding water of a former uranium mine

Remediation of former uranium mining sites represents one of the biggest challenges worldwide that have to be solved in this century. During the last years, the search of alternative strategies involving environmentally sustainable treatments has started. Bioremediation, the use of microorganisms to clean up polluted sites in the environment, is considered one the best alternative. By means of culture-dependent methods, we isolated an indigenous yeast strain, KS5 (Rhodosporidium toruloides), directly from the flooding water of a former uranium mining site and investigated its interactions with uranium. Our results highlight distinct adaptive mechanisms towards high uranium concentrations on the one hand, and complex interaction mechanisms on the other. The cells of the strain KS5 exhibit high a uranium tolerance, being able to grow at 6 mM, and also a high ability to accumulate this radionuclide (350 mg uranium/g dry biomass, 48 h). The removal of uranium by KS5 displays a temperature- and cell viability-dependent process, indicating that metabolic activity could be involved. By STEM (scanning transmission electron microscopy) investigations, we observed that uranium was removed by two mechanisms, active bioaccumulation and inactive biosorption. This study highlights the potential of KS5 as a representative of indigenous species within the flooding water of a former uranium mine, which may play a key role in bioremediation of uranium contaminated sites.This work was supported by the Bundesministerium für Bildung und Forschung grand nº 02NUK030F (TransAqua). Further support took place by the ERDF-co-financed Grants CGL2012-36505 and 315 CGL2014-59616R, Ministerio de Ciencia e Innovación, Spain

The Finniss River: a natural laboratory of mining impact- past present and future.

The Rum Jungle uranium-copper mine in tropical northern Australia has been a source of acid rock drainage contaminants since the 1950s which have had adverse impacts on the receiving waters of the Finniss River. Mine site remediation began in 1982 followed by long-term monitoring of water quality and flow based on daily measurements within the Finniss River system. A decade or more after the initiation of these remedial activities a set of investigations have been completed that have measured the post-remedial ecological status of the Finniss River system relative to this environmental benchmark. These studies have also been complemented by studies on various other ecological endpoints. Moreover the Finniss River system has provided unique opportunities for broader scientific goals to be pursued. Because it has been so well-monitored it can be viewed as a natural laboratory to investigate the impacts of acid rock drainage on tropical freshwater biodiversity. The scientific papers presented at this symposium address a broad spectrum of issues that are directly related to environmental sustainability and mining. The topics range across future contaminant scenarios and their predicted ecological impacts the various metrics used to assess ecological detriment to biodiversity the abilities of laminated biological structures to act as archives of pollution history and also spin-off applications in environmental and wildlife management. Furthermore the participation of many stakeholders in open discussion during the symposium provided an important set of views and opinions on the needs for future studies in the Finniss River system

Thermochemical data for environmentally-relevant elements.

This study provides an extensive stability constant (log K) database suitable for calculating the speciation of selected environmentally-relevant elements (H Na K Ca Mg Fe Mn U Al Pb Zn Cu and Cd) in an aqueous system where a model fulvic acid (comprising aspartic citric malonic salicylic and tricarballylic acids) is used to simulate metal binding by dissolved organic material Stability constants for inorganic metal complexes and minerals were selected primarily from critical literature complications and/or reviews. In contrast few critically evaluated data were available for metal complexes with aspartic citric, malonic, salicylic and tricarballylic acids. Consequently, data from original research articles were carefully evaluated and compiled as part of the study, following defined selection criteria. To meet the objective of compiling a comprehensive and reliable database of stability constants, all relevant equilibria and species, ranging from simple binary metal complexes to more complex ternary, and even quaternary, metal complexes were included where possible. In addition to the selection of stability constants from empirical sources, estimates of stability constants were performed when this could be done reliably, based on the unified theory of metal ion complexation and/or linear free energy relationships. The stability constants are given as common logarithms (log10) in the form required by the HARPHRQ geochemical code and refer to the standard state, i.e. 298.15 k (25—C), 106 Pa (1 atm) and, for all species, infinite dilution (ionic strength = 0 moI L-1). In addition to the compilation of stability constant data, an overview is given of geochemical speciation modeling in aqueous systems and available conceptual models of metal binding by humic substances

Absorption of divalent trace metals as analogues of calcium by Australian freshwater bivalves: an explanation of how water hardness reduces metal toxicity

A competitive inhibition experimental design, incorporating radiotracer labelling of metals and the geochemical simulation of their speciation at two varying Ca water concentrations, was employed to conclusively demonstrate that the divalent trace metals Pb, Mn, Cd and Co, were absorbed from the aquatic medium as metabolic analogues of Ca by two species of Australian freshwater bivalves (Hyridella depressa and Velesunio ambiguus). Several important implications stem from this mechanistic interpretation of metal uptake by aquatic organisms. Because of the general positive empirical relationship established between metal uptake/accumulation and acute/sub-chronic toxicity, the ameliorative effect of an increased water hardness on metal toxicity most likely results from the competitive binding of Ca (>Mg) at the Ca channels of the cell membrane. This conclusion is consistent with empirical studies and also with the basic chemical properties of Ca and Mg, that are relevant to their behaviour at the Ca channel. It follows that Ca water concentration, rather than total water hardness, should be utilised in water quality guidelines as the variable that governs the maximum permissible concentration of certain trace metals that can be sustained by freshwater life

Accumulation of metals by toadfish from sediment and infauna: Are fish what they eat?

Metals may have direct and indirect effects on aquatic biota at different trophic levels. This study examined the metal concentrations and nutritional value (protein and lipid content) of sediment infauna consumed by the estuarine smooth toadfish (Tetractenos glaber) at sites with varying metal contamination in the Parramatta River (Sydney Harbour), southeastern Australia, and the resulting influence on toadfish size and their tissue metal concentrations. Metal concentrations in sediments showed positive linear relationships (r2 = 0.29–0.87; P < 0.001, n = 12) with metal concentrations in sediment infauna. Metal concentrations in toadfish tissues were also linearly and positively related to metal concentrations in both sediments (r2 = 0.32–0.73; P < 0.001, n = 55) and infauna (r2 = 0.27–0.72; P < 0.001, n = 55), indicating that sediment and infauna are an important metal exposure pathway for toadfish. Of the key toadfish prey items (sediment infauna), polychaetes (Marphysa sanguinea) generally had the highest metal concentrations and nutritional value followed by semaphore crabs (Heloecius cordiformis) and black mussels (Xenostrobus securis). Polychaetes from the most contaminated site generally had higher metal concentrations and higher nutritional value than those from the least contaminated site. Toadfish from the most contaminated site generally had the highest metal concentrations, and were 15% larger and 41% heavier than similarly-aged toadfish from the least contaminated site, suggesting that toadfish may be benefiting in size due to ingestion of sediment infauna of higher nutritional value

Patterns of metal accumulation in osteoderms of the Australian freshwater crocodile, Crocodylus johnstoni.

The concentrations of 15 metals were measured in the osteoderms (dermal bones) of 30 freshwater crocodiles (Crocodylus johnstoni) from a single population in the Lynd River, northeastern Australia (17 degrees 50'S, 144 degrees 20'E), that were well characterised with respect to site fidelity, reproductive status and age. Multiple linear regression analyses were used to determine the effects of crocodile size (snout-vent length, 25-128 cm), age (0.7-62.7 years), gender (male or female) and reproductive status (sexually mature or immature) on osteoderm metal concentrations. Gender and reproductive status were not significant (P > 0.05) co-predictors of the osteoderm concentration of any metal. In contrast, size, age and osteoderm calcium concentration were highly significant (P < 0.001) systematic predictors of the osteoderm concentrations of all metals, except Na and K. Osteoderm metal concentrations were inversely related (P < 0.001) to both size (r(2) = 0.52-0.92) and age (r(2) = 0.52-0.84), but positively related (P < 0.001) to osteoderm calcium concentration (r(2) = 0.67-0.92). Relative to calcium concentration, the rates of metal accumulation in the osteoderms of C. johnstoni were inversely related to the solubility constant (log K(sp)) of the metal as a phosphate; however this relationship was not linear. This finding is consistent with that previously established for the flesh of freshwater bivalves, which like the crocodilian osteoderm, have a calcium phosphate repository in the form of extracellular granules. The constancy of this relationship between rate of metal accumulation and relative solubility for calcium phosphate deposits, despite contrasting Ca accumulation regimes and taxonomic dissimilarity, points to a potential underlying principle that warrants investigation in a greater range of biota. The implications for using the osteoderms of C. johnstoni as an indicator of metal levels in freshwater ecosystems are also discussed

Catchment-specific element signatures in estuarine crocodiles (Crocodylus porosus) from the Alligator Rivers Region, northern Australia.

The concentrations of Na, K, Ca, Mg, Ba, Sr, Fe, Al, Mn, Zn, Pb, Cu, Ni, Cr, Co, Se, U and Ti were determined in the osteoderms and/or flesh of estuarine crocodiles (Crocodylus porosus) captured in three adjacent catchments within the Alligator Rivers Region (ARR) of northern Australia. Results from multivariate analysis of variance showed that when all metals were considered simultaneously, catchment effects were significant (P < or = 0.05). Despite considerable within-catchment variability, linear discriminant analysis (LDA) showed that differences in elemental signatures in the osteoderms and/or flesh of C. porosus amongst the catchments were sufficient to classify individuals accurately to their catchment of occurrence. Using cross-validation, the accuracy of classifying a crocodile to its catchment of occurrence was 76% for osteoderms and 60% for flesh. These data suggest that osteoderms provide better predictive accuracy than flesh for discriminating crocodiles amongst catchments. There was no advantage in combining the osteoderm and flesh results to increase the accuracy of classification (i.e. 67%). Based on the discriminant function coefficients for the osteoderm data, Ca, Co, Mg and U were the most important elements for discriminating amongst the three catchments. For flesh data, Ca, K, Mg, Na, Ni and Pb were the most important metals for discriminating amongst the catchments. Reasons for differences in the elemental signatures of crocodiles between catchments are generally not interpretable, due to limited data on surface water and sediment chemistry o