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Sediments contaminated with hazardous metals pose risks to humans and wildlife, yet viable management options are scarce. In a series of laboratory experiments, we characterized Polonite® – an activated calcium-silicate – as a novel sorbent for thin-layer capping of metal-contaminated sediments. We tested a fine-grained by-product from the Polonite production as a cheap and sustainable sorbent. First, Polonite was reacted with solutions of Cu, Pb, and Zn, and the surface chemistry of the Polonite was examined using, e.g., scanning electron microscopy to investigate metal sorption mechanisms. Batch experiments were conducted by adding Polonite to industrially contaminated harbor sediment to determine sorption kinetics and isotherms. Importantly, we measured if the Polonite could reduce metal bioavailability to sediment fauna by performing digestive fluid extraction (DFE). Finally, a cap placement technique was studied by applying a Polonite slurry in sedimentation columns. The results showed rapid metal sorption to Polonite via several mechanisms, including hydroxide and carbonate precipitation, and complexation with metal oxides on the Polonite surface. Isotherm data revealed that the sediment uptake capacity (Kf) for Cu, Pb, and Zn increased by a factor of 25, 21, and 14, respectively, after addition of 5% Polonite. The bioavailability of Cu, Pb, and Zn was reduced by 70%, 65%, and 54%, respectively, after a 25% Polonite addition. In conclusion, we propose that sediment treatment with low doses of the Polonite by-product can be a cheap, sustainable, and effective remediation method compared to other more intrusive methods such as dredging or conventional isolation capping.

The role of water chemistry in the adsorption of flotation reagents on various minerals is outlined as well as the effect of dissolved species on the electrokinetic properties of oxide and sulphide minerals. Dissolved Ca and Mg affect the properties of francolite and dolomite whereas Fe, Cu and Ni species affect the surface properties of chalcopyrite, pentlandite, millerite, pyrrhotite and covellite in certain pH ranges, as species adsorption can lead to activation or depression of reagents, surface precipitation and complexation of species. The effects of interactions between dissolved mineral ions and various surfactant species on the flotation behaviour of salt-type minerals must also be considered., The role of water chemistry in the adsorption of flotation reagents on various minerals is outlined as well as the effect of dissolved species on the electrokinetic properties of oxide and sulphide minerals. Dissolved Ca and Mg affect the properties of francolite and dolomite whereas Fe, Cu and Ni species affect the surface properties of chalcopyrite, pentlandite, millerite, pyrrhotite and covellite in certain pH ranges, as species adsorption can lead to activation or depression of reagents, surface precipitation and complexation of species. The effects of interactions between dissolved mineral ions and various surfactant species on the flotation behaviour of salt-type minerals must also be considered.

Phytostabilization is a non-invasive remediation technique that combines the utilization of amendments and plants to enhance natural attenuation mechanisms (adsorption, precipitation and complexation) that immobilize trace elements in soil (Adriano et al., 2004). In addition, phytostabilization might reduce soil erosion and run-off transport of contaminated particles. While this low-cost technique has potential for in situ treatment of extensive areas moderately contaminated, it has been argued that repetitive amendment additions are necessary to prevent reversability of treatments associated with changes in soil pH or organic matter mineralization (Azevedo-Silveira et al., 2003). However, there is insufficient information concerning the longevity and stability of treatments in field experiments, particularly in semiarid areas, characterised by low vegetation density and low organic matter content (usually less than 1-2%). In the present study, we evaluate the mid-term effects of repetitive vs single amendment applications on wild vegetation growing in a soil with residual As, Cd, Cu, Pb and Zn contamination, formerly affected by the Aznalcóllar mine accident

Dissolved Fe, Cu, and Ni species are found to affect the properties of chalcopyrite, pentlandite, millerite, pyrrhotite and covellite in certain pH ranges. These effects are interpreted in terms of species adsorption, leading to activation or depression of reagents, surface precipitation and complexation of species., Dissolved Fe, Cu, and Ni species are found to affect the properties of chalcopyrite, pentlandite, millerite, pyrrhotite and covellite in certain pH ranges. These effects are interpreted in terms of species adsorption, leading to activation or depression of reagents, surface precipitation and complexation of species.

1. Autumn circulation in lakes is currently conceived to occur very rapidly, being controlled mainly by wind-power dynamics, decreasing irradiance and heat flux. In addition, autumn mixing is usually related to nutrient redistribution in the vertical column, resulting in its overall increase. To test these assumptions, mixing and nutrient dynamics in a Spanish small, wind-sheltered, mesotrophic, seepage lake were studied daily during autumn circulation., 2. The seasonal erosion of the pycnocline in Las Madres Lake was the outcome of vertical and horizontal exchanges of heat and matter. The overall mixing of the water column lasted 3 months, which was an unexpected period for a rather shallow lake. Two periods of mixing could be envisaged until full circulation was attained. First, a slightly faster period of pycnocline deepening than that predicted by the heat flux and wind stress model of Fisher et al. (1979) occurred for 41 days, mixing most of the water column down to within two meters of the bottom. Then a much slower process took place promoting frequent instability of the bottom layer and resulting in entire mixing in a further 52 days., 3. Vertically, the whole mixing process was a response to weak surface cooling, resulting from the mild air temperatures of the semiarid climate of the area, and weak wind stress, because of low wind fetch and high shelter. Horizontally, a gravity current transporting cold, denser water from western shallower areas of the lake and materials produced by the decomposition of organic matter of littoral origin may produce a bottom layer of increased density, thus impinging on vertical stability. Seepage inputs of water of roughly constant temperature might also have increased bottom density. Bottom density enhancement resulted in a double diffusion process., 4. Only in-lake nitrogen content increased until full circulation was attained, whereas carbon showed no trend and phosphorus declined. External processes, such as seepage exchange and atmospheric deposition, coupled to internal processes, such as nitrification, oxidised phosphorus precipitation and complexation with organic carbon, might have been responsible for the areal nutrient patterns observed., 5. Our study demonstrates that current models of water column mixing and nutrient redistribution in lakes during autumn circulation must be improved to encompass the effects of external inputs, including horizontal heat and matter exchange.

Eight water insoluble complexes of tetramethylsulfonated calix[4]resorcinarenes 1 and 2 (-CH3 and -C5H 11) with phenothiazine derivative, 3, were obtained under substoichiometric conditions by mixing aqueous solutions of the initial reagents. It was found that complexation of cationic 3 by macrocycles was provided by both Coulomb interaction with the negative sulfonato-groups on the upper rim and by cation-π interactions with the aromatic cavity. The complexes precipitated and, therefore, were studied in organic solvents-DMSO, CD3OD, and CDCl3 using IR-, UV-, and NMR- spectroscopy. Formation of the complexes accompanied by gradual dehydratation of the host-estimated quantity of water in the complexes decreased with increase of the initial concentration of 3. Driving forces of precipitation and complexation, the role of water coordinated by the hosts, and distribution of phenothiazine derivative between two kinds of binding sites are discussed. © 2007 Springer Science+Business Media, Inc.

Eight water insoluble complexes of tetramethylsulfonated calix[4]resorcinarenes 1 and 2 (-CH3 and -C5H 11) with phenothiazine derivative, 3, were obtained under substoichiometric conditions by mixing aqueous solutions of the initial reagents. It was found that complexation of cationic 3 by macrocycles was provided by both Coulomb interaction with the negative sulfonato-groups on the upper rim and by cation-π interactions with the aromatic cavity. The complexes precipitated and, therefore, were studied in organic solvents-DMSO, CD3OD, and CDCl3 using IR-, UV-, and NMR- spectroscopy. Formation of the complexes accompanied by gradual dehydratation of the host-estimated quantity of water in the complexes decreased with increase of the initial concentration of 3. Driving forces of precipitation and complexation, the role of water coordinated by the hosts, and distribution of phenothiazine derivative between two kinds of binding sites are discussed. © 2007 Springer Science+Business Media, Inc.