Detection of tris(2,3-dibromopropyl) phosphate and other organophosphorous compounds in Arctic rivers.

The flame-retardant tris(2,3-dibromopropyl) phosphate (TDBrPP) was in the 1970s banned for uses in textiles that may be in contact with the skin, owing to strong suspicions that the substance was a human carcinogen. The substance is looked for but rarely detected in samples from the built and natural environments, but there are indications that TDBrPP is still in use. Here, we report the measurement of a polymer-water partition coefficient (Kpw) for two types of silicone rubber (SR), allowing quantitative estimation of freely dissolved concentrations of TDBrPP by passive sampling in water. We found levels of 100 to 200 pg/L in two Arctic rivers that were sampled during a 2014-2015 survey of contamination using passive samplers in Norwegian and Russian rivers draining into the Barents Sea. We also report the widespread presence of other organophosphorus flame retardants in this survey of eight rivers that drain into the Barents Sea.

Metal and proton toxicity to lake zooplankton: a chemical speciation based modelling approach.

The WHAM-FTOX model quantifies the combined toxic effects of protons and metal cations towards aquatic organisms through the toxicity function (FTOX), a linear combination of the products of organism-bound cation and a toxic potency coefficient for each cation. We describe the application of the model to predict an observable ecological field variable, species richness of pelagic lake crustacean zooplankton, studied with respect to either acidification or the impacts of metals from smelters. The fitted results give toxic potencies increasing in the order H(+) < Al < Cu < Zn < Ni. In general, observed species richness is lower than predicted, but in some instances agreement is close, and is rarely higher than predictions. The model predicts recovery in agreement with observations for three regions, namely Sudbury (Canada), Bohemian Forest (Czech Republic) and a subset of lakes across Norway, but fails to predict observed recovery from acidification in Adirondack lakes (USA).

Interactions of trace metals with hydrogels and filter membranes used in DET and DGT techniques.

Equilibrium partitioning of trace metals between bulk solution and hydrogels/filter was studied. Under some conditions, trace metal concentrations were higher in the hydrogels or filter membranes compared to bulk solution (enrichment). In synthetic soft water, enrichment of cationic trace metals in polyacrylamide hydrogels decreased with increasing trace metal concentration. Enrichment was little affected by Ca and Mg in the concentration range typically encountered in natural freshwaters, indicating high affinity but low capacity binding of trace metals to solid structure in polyacrylamide gels. The apparent binding strength decreased in the sequence: Cu > Pb > Ni approximately to Cd approximately to Co and a low concentration of cationic Cu eliminated enrichment of weakly binding trace metal cations. The polyacrylamide gels also had an affinity for fulvic acid and/or its trace metal complexes. Enrichment of cationic Cd in agarose gel and hydrophilic polyethersulfone filter was independent of concentration (10 nM to 5 microM) but decreased with increasing Ca/ Mg concentration and ionic strength, suggesting that it is mainly due to electrostatic interactions. However, Cu and Pb were enriched even after equilibration in seawater, indicating that these metals additionally bind to sites within the agarose gel and filter. Compared to the polyacrylamide gels, agarose gel had a lower affinity for metal-fulvic complexes. Potential biases in measurements made with the diffusive equilibration in thin-films (DET) technique, identified by this work, are discussed.

Transformation of iron species in mixing zones and accumulation on fish gills.

The speciation of iron (Fe) strongly influences the deposition and accumulation on gills causing toxicitytoward fish. The impacts of ferric (Fe(III)) and ferrous (Fe(II)) species on gill accumulation were studied in parallel flow-through channel experiments where Atlantic salmon (Salmo salar L.) was kept in cages. Downstream of the pH 6.3 mixing point, where Fe(III) ions or Fe(ll) ions were added continuously to lake water, the molecular mass of Fe(III) increased within 0.5 min after mixing due to hydrolysis and polymerization, while the Fe(II) species remained as low molecular mass (LMM) species 20 min after mixing. For fish exposed to the Fe(lll) enriched water (0.5 mg L(-1)) the Fe accumulation on gills was high and decreased downstream, while low when Fe(II) was added to water. By adjusting the Fe(II) enriched water to pH 6.7, the oxidation of Fe(II) forming Fe(III) accelerated, the Fe accumulation on fish gills increased by a factor of 3, and high mortality (33%) was observed. Thus, input of Fe(ll) ions, oxidation of Fe(ll) at rates higher than 1.5 microg L(-1) min(-1), and continuous formation of LMM Fe(III) species accumulating on gills can induce toxicity toward fish present in circumneutral freshwaters a long distance downstream from the entry points.

Effects of binding of metals to the hydrogel and filter membrane on the accuracy of the diffusive gradients in thin films technique.

The effect of metal binding to the diffusion layer of diffusive gradients in thin films (DGT) on measurements of time-integrated concentrations (CDGT) was studied experimentally and using a numerical model. Cationic divalent Cu and Cu-fulvic complexes bind to sites in the filter membrane and polyacrylamide (APA) gel, together comprising the diffusion layer of DGT. Less Cu was found in Chelex gels retrieved immediately after DGT deployment than in Chelex gels retrieved after storage of deployed DGTs. The difference was attributed to postdeployment transport of Cu from the diffusion layer to the Chelex gel. Binding of Cu in the diffusion layer delays the formation of a steady concentration gradient between solution and Chelex gel and can, depending on diffusion layer thickness, speciation, and concentration of metal, significantly bias the measurement of CDGT for short deployment times. However, C(DGT) will converge with the concentration in solution provided that the deployment time is sufficiently long (for a 1.0 mm diffusion layer, a diffusion coefficient of 5.5 x 10(-6) cm2 s(-1) and a concentration of Cu in solution of 0.1 nM, the difference is less than 11% and 5% for deployment times longer than 32 and 64 h, respectively). Minimal bias is encountered when measuring Cu contaminated waters (> or = 100 nM) using DGTs with thinner (< or = 0.5 mm) diffusion layer thicknesses. Diffusion layer binding of cationic Cd in the presence of cationic Cu was insignificant, and C(DGT) of Cd was found to converge with the concentration in solution after deployment times of 4 h and less. These findings have implications for the maximum temporal resolution that can be achieved with DGT.

Gill metal binding and stress gene transcription in brown trout (Salmo trutta) exposed to metal environments: the effect of pre-exposure in natural populations.

Brown trout (Salmo trutta) from two native populations from the Røros area in Central Norway, acclimated in mining-affected habitats to different levels of Cd/Zn and Cu, together with trout from a nearby unaffected river (reference) were transferred to a nearby lake with higher levels of Cu, Cd, and Zn than those in their respective native rivers. This experiment was conducted to gain information about the underlying resistance mechanisms developed in fish exposed to metal environments. The focus was on gill metal accumulation and transcription of the metal-responsive stress genes metallothionein-A (MT-A), Cu/Zn-superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and heat shock protein 70 (HSP-70). The only shared response shown between the three groups after transfer were Cu accumulation and MT-A induction. The Cu-acclimated trout produced mucus to reduce the uptake of Cu into the gills. The MT-A levels were highest in the Cd/Zn-acclimated trout both before and after transfer. Before transfer, antioxidant transcription (SOD and GPx) was higher in gills of Cu-acclimated compared to the Cd/Zn-acclimated trout, but increased transcription of antioxidant stress genes was observed after transfer in both metal-acclimated groups. The metal-acclimated trout groups also showed an increase in the transcription of HSP-70. Compared to the reference population not previously exposed to metals, stress gene transcription increased faster in the metal-acclimated populations. The exception was induction of CAT, which appeared to be depressed after transfer in Cd/Zn-acclimated trout. The data indicate that acclimation to chronic metal exposure involves different strategies to cope with different metals and that these strategies involve both physiological mechanisms (mucus production) as well as metal-related stress gene transcription.