Transformation Kinetics of Burnt Lime in Freshwater and Sea Water.

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it "slaked" as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

Induction and activity of oxidative stress-related proteins during waterborne Cd/Zn-exposure in brown trout (Salmo trutta).

We studied how transcript levels of metallothionein (MT), Cu/Zn-superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GR) as well as functional protein levels of MT, SOD and CAT in brown trout tissues changed during a 15-days waterborne exposure to Cd and Zn. Trout from a river with low levels of metals (the Stribekken River) was transferred to a river with high levels of Cd and Zn (the Naustebekken River) and exposed up to 15 days. The aim of this transfer experiment was to investigate how exposure to Cd and Zn induced transcription and activities of central antioxidant enzymes and proteins in an environmental setting. Significant uptake of both Cd and Zn was observed in gills during the 15 days exposure, and Cd levels was found to correlate significantly with transcript levels of MT-A, SOD, GPx and GR. Gill concentrations of Zn did not correlate significantly with the transcript levels of the stress genes studied, but Zn might have triggered transcription of proteins which dealt with subsequent accumulation of Cd. SOD and CAT activities increased in gills after transfer, but MT protein levels decreased. In liver, SOD activity and MT protein levels increased, while in kidney only MT protein concentrations were elevated after transfer. There was a general lack of consistency between mRNA transcription and enzyme activities, indicating that these proteins and enzymes are not solely under transcriptional control.

Dynamic aspects of DGT as demonstrated by experiments with lanthanide complexes of a multidentate ligand.

Sampling of metals with the technique of diffusive gradients in thin-films (DGT) depends on the rates of diffusion and on the kinetics of interconversion of the species present. In this study the discrimination between metal complexes with different dissociation kinetics is investigated. Samplers with differentthicknesses of diffusive and resin gels were deployed in solutions containing 10 microg/L of each metal in the lanthanide (Ln) series (except Pm) and 2.0 x 10(-6) M of the ligand quin2 at an ionic strength of 0.1 M (KNO3) and pH 7.0. Diffusion coefficients of Ln3+ ions and Ln-quin2 complexes were determined in a diffusion cell experiment. The equilibrium speciation of the metals was calculated from available stability constants. The sampling rate (mass/time) was highly dependent on the dissociation-rate constant of the complexes. For complexes with dissociation kinetics that appreciably limited the uptake, the sampling rate decreased significantly with increasing deployment times (12, 24, and 76 h) and was virtually independent of the thickness of the diffusive gel. Placing a layer of diffusive gel behind the resin did not influence the accumulation of Lns in the resin gel, but doubling the thickness of the layer containing resin increased the uptake, and more so for the Lns forming less labile complexes. The Lns forming more labile complexes were enriched in the outer layer of the resin, and there was a trend toward even distribution between the outer and deeper parts of the resin layer for the Lns forming less labile complexes. The measured DGT sampling rates (mass/ time) were reasonably well predicted by a dynamic model that used independently determined kinetic constants. This new knowledge of how metal complexes behave in the sampling process paves the way for using DGT to obtain in situ kinetic information in natural waters.

Diffusive gradients in thin films sampler predicts stress in brown trout (Salmo trutta L.) exposed to aluminum in acid fresh waters.

Increased levels of aluminum ions released from nutrient-poor soils affected by acid rain have been the primary cause of fish deaths in the acidified watersheds of southern Norway. The complex aluminum chemistry in water requires speciation methods to measure the gill-reactive species imposing toxic effects toward fish. Previously, aluminum speciation has mainly followed the fractionation principles outlined by Barnes/Driscoll, and several analogues of these fractionation principles have been used both in situ and in the laboratory. Due to rapid transformation processes, aluminum speciation in water samples may change even during short storage times. Thus, results obtained by laboratory fractionation methods might be misleading for the assessment of potentially toxic aluminum species in the water. Until now, all in situ field fractionation methods have been time and labor consuming. The DGT technique (diffusive gradients in thin films) is a new in situ sampler collecting a fraction of dissolved metal weighted according to the rate of diffusion and dissociation kinetics. In a field experiment with acid surface water we studied the DGT sampler as a new prediction tool for the gill accumulation of aluminum in trout (Salmo trutta L.) and the induced physiological stress responses measured as changes in blood glucose and plasma chloride. Aluminum determined with DGT (DGT-AI) was higher than labile monomeric aluminum (Ali) determined with a laboratory aluminum fractionation procedure (PCV--a pyrocatechol violet analogue of Barnes/Driscoll), a difference due to collection of a fraction of organically complexed aluminum by DGT and a reduction of the Ali fraction during sample storage. DGT-AI predicted the gill uptake and the aluminum-induced physiological stress responses (increased blood glucose and decreased plasma chloride, r2 from 0.6 to 0.9). The results indicate that DGT-AI is a better predictor for the stress response than laboratory-determined Ali, because the DGT sampler collects a more correct fraction of the gill-reactive aluminum species that induces the stress.

Performance study of diffusive gradients in thin films for 55 elements.

The technique of diffusive gradients in thin films (DGT) is a fairly new and useful tool for in situ measurements of labile metal ions in water. The applicability of DGTs was investigated by comparing independently determined or estimated diffusion coefficients with DGT effective diffusion coefficients (D(DGT)) for 55 elements. The DGTs were exposed at a controlled fluid velocity of 0.1 m s(-1) and a concentration of 1 ng mL(-1) at four pH levels between 4.7 and 6.0, and the D(DGT) values were determined from the uptake by the sampler. The measured D(DGT) values for the elements Co, Ni, Cu, Zn, Cd, Pb, Al, Mn, and Ga were close to previously published values with some deviations for Pb and Zn. The uptake of V, Cr, Fe, U, Mo, Ti, Ba, and Sr varied with pH, and there were some experimental problems that require further investigations. A novel set of D(DGT) values for the lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, Yb, Lu, Y) was established. The D(DGT) values for these were about 10-15% lower than for free ions in water and indicate that diffusion coefficients of metal ions in the agarose polyacrylamide diffusive hydrogel are 10-15% lower than in water. The high consistency of the data for the lanthanides establishes these elements as new performance test metals for the DGT sampler. The accumulation of the elements Li, Na, K, Rb, Mg, Ca, B, Tl, P, S, As, Bi, Se, Si, Sn, Sb, Te, Zr, Nb, Hf, Ta, W, Th, and Ag was low (D(DGT) lower than 10% of theoretical values). A more efficient elution procedure using concentrated nitric acid for the absorbent gel was established, with elution efficiencies between 95 and 100% for most metals. For deployment times of 24 h, detection limits from 0.001 to 1 ng mL(-1) were achieved with moderate precautions to prevent contamination.