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Brit Salbu

Publications and source records attributed to Brit Salbu.

11 recordsLinked to original sources
PubMed2006

Mobilization of river transported colloidal aluminium upon mixing with seawater and subsequent deposition in fish gills.

During flooding events, increased concentrations of gill-reactive aluminium (Al) have been identified in estuarine water causing high Al accumulation in fish gills. By in situ filtering and ultrafiltering river water (pH 5.5-6.4, 3-5 mg L(-1) DOC) and continually mixing the size fractioned river water with seawater (30 in salinity), Al mobilization was studied in flow-through tank systems (6 in salinity) during a six-week field experiment in Western Norway. Atlantic salmon (Salmo salar L.) kept in tanks were continuously exposed to the mixtures. Based on in situ Al fractionation of the experimental waters and sampling of gills from exposed fish, results showed that Al associated with river transported colloids, probably organic material ( 8 kDa) was mobilized to low molecular mass cationic Al-species (LMM Al(i)) upon contact with seawater. Mobilized Al(i)-species deposited immediately on fish gills. During high flow conditions with increased amounts of colloidal material, the concentration of mobilized LMM Al(i) and the Al accumulation in gills of fish exposed to river water-seawater mixtures increased by a factor of 5 and 10, respectively, compared to the input river water. The concentration of mobilized LMM Al(i) and the Al accumulation in fish gills decreased with time after mixing (from 1 to 30 min) and as high runoff subsided.

Aluminum↗
PubMed2005

Sodium silicate as alternative to liming-reduced aluminium toxicity for Atlantic salmon (Salmo salar L.) in unstable mixing zones.

When acid aluminium (Al) rich water is limed, unstable mixing zones are formed until equilibrium is reached. In such mixing zones transient high molecular mass positively charged Al-species (HMM Al(i)) being extremely gill reactive are produced, causing toxic effects in fish. The transient HMM Al(i)-species are formed due to hydrolysis and polymerization of low molecular positively charged Al-species (LMM Al(i)), e.g. initiated by liming and the subsequent increase in pH. To counteract the toxicity of transient Al polymers in such mixing zones, sodium silicate, forming non-toxic hydroxyaluminosilicate (HAS) complexes, can be used as alternative to liming. In the present work the effect of sodium silicate on polymerization of LMM Al(i) in unstable mixing zones and subsequent gill reactivity and mortality of fish was compared to results obtained from liming. Diluted sodium silicate (<1.5 g l(-1)) and lime slurry (Ca(OH)(2)), respectively, were continually added to acidified Al-rich water in six different channel-tank systems, to obtain mixing zones with pH 5.9, 6.0 and 6.4, respectively. Utilising in situ size and charge fractionation techniques and following the exposure of Atlantic presmolt (Salmo salar L.) kept in cages at defined stations along the channel-tank systems, changes of Al-species in the mixing zones, the gill reactivity of Al-species and thus Al toxicity could be followed downstream the confluences (time of reaction after mixing: 1-100 min). By increasing the pH of the acid water to 6.0 or 6.4 by sodium silicate, the detoxification of Al was faster than using lime. Using sodium silicate, the transformation of LMM Al(i), the formation of HMM Al(i), the Al deposition in fish gills and fish mortality were lower than using lime. The formation of neutral LMM Al-species (Al(o)) was, however, higher and the formation of colloidal Al-species (Al(c)) lower in the presence of silicate compared to lime. Furthermore, the Al deposition in fish gills and fish mortality decreased by increasing concentration of sodium silicate dosed. Thus, sodium silicate is a good alternative to liming, and under certain circumstances when aging of water may represent a problem (e.g. aquaculture) sodium silicate should be the preferred agent.

Aluminum↗
PubMed2005

Fish mortality during sea salt episodes--catchment liming as a countermeasure.

Aluminium (Al) toxicity is usually associated with acid rain and acidified freshwater systems. The present work demonstrates that acute fish mortality (50%) also occurs in moderate acidified salmon rivers during sea salt episodes. Furthermore, catchment liming was proved to be an efficient measure to counteract the fish toxicity. The impact of sea salt episodes on river water qualities and on Atlantic Salmon (Salmo salar L.) was studied in two rivers situated at the west coast of Norway. During February-May 2002, fish were kept in tanks and continually exposed to the changing water qualities. Changes in Al-species were followed using in situ fractionation techniques. During storm events and high sea salt deposition, the sea salt concentration increased (190 to 580 microM Cl), pH decreased (pH 5.3 to 4.6) and the concentration of low molecular mass (LMM) cationic Al-species (Al(i)) increased (0.7 to 3.0 microM) in the river. Subsequently, Al accumulated in fish gills (6 to 19 micromol g(-1) dw) causing ionoregulatory and respiratory failures as well as mortality. In water the concentration of LMM Al(i) stayed enhanced during four weeks, while the physiological stress responses in surviving fish remained high for a longer time (>eight weeks). To counteract Al toxicity, one of the tributary catchments had been limed four years earlier. Due to catchment liming (1000 kg ha(-1)) the water concentration of LMM Al(i)(<0.7 microM) and the Al accumulation in gills remained relatively low (<7 micromol g(-1) dw) during the storm and no fish mortality occurred.

Aluminum↗
PubMed2005

Gill reactivity of aluminium-species following liming.

In acidified aluminium (Al) rich freshwater positively charged Al-species (Al(i)) are the key toxic components due to the accumulation in fish gills. As a countermeasure, liming is used to increase the pH and reduce the concentration of Al(i)-species; in particular low molecular mass (LMM) Al(i)-species by hydrolyses. However, very toxic high molecular mass (HMM) Al polymers can form in the unstable mixing zone immediately after liming. In the present work gill reactivity of LMM and HMM Al-species was studied under controlled conditions in eight channel-tank mixing zone systems in the field where Atlantic salmon (Salmo salar L.) kept in cages were exposed to defined mixing zone water. Mixing zones were created by continually liming acid river water (pH 5.0-5.7) high in LMM Al(i) to pH 6.0 and 6.4, respectively. Transformation processes affecting the Al-speciation as a function of time after liming were documented by in situ hollow fibre ultrafiltration interfaced with ion chromatography, while the Al accumulation in fish gills was used as bioindicator. For fish exposed to mixing zone water immediately after liming (1 min) the Al accumulation in gills (mug Al g(-1)) was higher (factor of 2) than for fish exposed to acid water prior to liming, due to the formation of gill reactive HMM Al(i)-species. The Al accumulation in gills followed a first order kinetic expression reaching steady-state conditions after 24-h exposures. The deposition rate of Al in gills (mug Al g(-1) h(-1)) correlated with the water concentrations of HMM Al(i) (R(2)=0.80) in the mixing zones, and for LMM Al(i) in the acid water (R(2)=0.92). Due to the transient nature of HMM Al(i) the deposition rate of Al decreased from the point of liming with a factor of 10 downstream the channel-tank system (i.e. 100 min after liming). The concentration of gill accumulated Al was higher (factor of 3) immediately after high level liming (pH 6.4) than following low level liming (pH 6.0). However, high level liming was more efficient in detoxifying Al in downstream waters. Furthermore, the bioavailability of a given LMM Al(i) concentration as well as bioreactivity following liming was dependent on the TOC and silicon concentration in the acid water. Increased concentration of TOC (1.5 to 4.3 mg l(-1)) and silicon (0.3 to 1.0 mg l(-1)) reduced the gill reactivity of Al(i) by approximately 50%.

Aluminum↗
PubMed2005

Plutonium contamination in soils and sediments at Mayak PA, Russia.

The Mayak Production Association (Mayak PA) was established in the late 1940's to produce plutonium for the Soviet Nuclear Weapons Programme. In total, seven reactors and two reprocessing plants have been in operation. Today, the area comprises both military and civilian reactors as well as reprocessing and metallurgical plants. Authorized and accidental releases of radioactive waste have caused severe contamination to the surrounding areas. In the present study, [alpha]-spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS) have been used to determine plutonium activities and isotope ratios in soil and sediment samples collected from reservoirs of the Techa River at the Mayak area and downstream Techa River. The objective of the study was to determine the total inventory of plutonium in the reservoirs and to identify the different sources contributing to the plutonium contamination. Results based on [alpha]-spectrometry and ICP-MS measurements show the presence of different sources and confirmed recent reports of civilian reprocessing at Mayak. Determination of activity levels and isotope ratios in soil and sediment samples from the Techa River support the hypothesis that most of the plutonium, like other radionuclides in the Techa River, originated from the very early waste discharges to the Techa River between 1949 and 1951. Analysis of reservoir sediment samples suggest that about 75% of the plutonium isotopes could have been released to Reservoir 10 during the early weapons production operation of the plant, and that the majority of plutonium in Reservoir 10 originates from discharges from power production or reprocessing. Enhanced 240Pu/239Pu atom ratios in river sediment upper layers (0-2 cm) between 50 and 250 km downstream from the plant indicate a contribution from other, non-fallout sources.

Environmental Monitoring↗
PubMed2004

Transformation of positively charged aluminium-species in unstable mixing zones following liming.

Liming is widely used to counteract chronic toxicity of positively charged monomeric aluminium species (Ali). Immediately after liming, unstable mixing zones are formed due to the sudden increase in pH. Transformation of monomeric Ali species takes place instantaneously and transient positively charged Al polymers, being acute toxic to fish, are formed in the mixing zones. Using in situ hollow fibre ultrafiltration interfaced with ion chromatography in unstable mixing zone field experiments performed in two river systems situated south and southwest of Norway, information on time-dependent transformations of low molecular mass (LMM) and high molecular mass (HMM) positively charged Ali-species has been followed. The formation of HMM Ali species from LMM Ali occurred rapidly following liming. HMM Ali species have a certain lifetime and are transformed to high molecular mass neutral Al-species (HMM Alo) and then to non-reactive colloidal Al species (HMM Alc). Concentration levels of transient Al-species formed in the mixing zone and the rate of transformation depend on the concentrations of LMM Ali species, Al complexing ligands (DOC and Si) in the input water and on pH in the mixing zone after liming. A dynamic model describing transformation processes influencing the Al speciation in mixing zones following a sudden increase in pH is suggested. Based on the experimental results, associated rate constants and half-lives for transient Al-species were estimated.

Journal Article↗
PubMed2004

Mobilization of aluminium and deposition on fish gills during sea salt episodes--catchment liming as countermeasure.

Episodic events may be critical with respect to aluminium (Al) toxicity in moderately acidified salmon rivers. The present work demonstrates that sea salt episodes enhance the toxicity of Al in acidic rivers. The documented sea salt episode (300 [micro sign]M Cl) mobilized positively charged Al species (0.4 to 1.1 [micro sign]M Al(i)), enhanced the Al accumulation on fish gills (0.9 to 10 [micro sign]mol g(-1) dw) and caused increased stress responses (6 to15 mM blood glucose) in fish. Accumulated Al on gills remained high several days after the episode. The presented results are based on a six-week field study in two tributary rivers on the west coast of Norway. Changes in the river water qualities and Al speciation were followed using in situ fractionation techniques. Al accumulation on gills and stress responses were followed for Atlantic salmon (Salmo salar) kept in tanks continually exposed to the changing water quality. The potential mobilization of Al from the two catchments was studied by extracting soils with diluted seawater (salinity of 3). To counteract Al toxicity, one of the tributary catchments has been limed. The potential mobility of Al by sea salt was lower in limed soils compared to acid soils, and the Al deposition on fish gills (<3.5 [micro sign]mol g(-1) dw) and associated stress responses stayed low during the sea salt episode in the river draining the limed catchment. Thus, for acid river systems in coastal areas, catchment liming should be considered as a useful countermeasure for Al toxicity.

Aluminum↗
PubMed2002

Potential remobilization of 137Cs, 60Co, 90Tc, and 90Sr from contaminated Mayak sediments in river and estuary environments.

Following 50 years of nuclear production at Mayak PA, sediments in storage reservoirs are significantly contaminated. Dam failure or flooding could potentially transport large amounts of sediments, via rivers, to the Ob estuary and Kara Sea. The objectives of this work were to investigate fresh and seawater remobilization of 137Cs, 50Co, 99Tc, and 90Sr from contaminated Reservoir 10 sediments. Sediments were extracted sequentially using synthetic Techa freshwater, seawater, and chemical reagents with increasing dissolution powers. 137Cs and 90Sr freshwater distribution coefficients (apparent Kd) agreed quite well with published values; values for 99Tc were higher and values for 60Co were lower than expected. In seawater, mean apparent Kd values decreased by 94, 77, 48, and 73% (137Cs, 60Co, 99Tc, and 90Sr, respectively), indicating increased radionuclide mobility. Remobilization in seawater was 5, 15, 1, and 23% of total activities (i.e., releases of 165, 11, 0.3, and 170 kBq kg(-1) d.w.) for 137Cs, 60Co, 99Tc, and 90Sr, respectively. 137Cs and 99Tc were strongly bound to sediments (60% and 80%, respectively). 60Co and 90Sr were more mobile (70% reversibly bound). In conclusion, Mayak Reservoir sediments could potentially contaminate the Ob estuary due to remobilization of sediment-held radionuclides upon contact with seawater.

Environmental Monitoring↗
PubMed2002

Fixation of Cs to marine sediments estimated by a stochastic modelling approach.

Dumping of nuclear waste in the Kara Sea represents a potential source of radioactive contamination to the Arctic Seas in the future. The mobility of 137Cs ions leached from the waste will depend on the interactions with sediment particles. Whether sediments will act as a continuous permanent sink for released 137Cs, or contaminated sediments will serve as a diffuse source of 137Cs in the future, depends on the interaction kinetics and binding mechanisms involved. The main purpose of this paper is to study the performance of different stochastic models using kinetic information to estimate the time needed for Cs ions to become irreversibly fixed within the sediments. The kinetic information was obtained from 134Cs tracer sorption and desorption (sequential extractions) experiments, conducted over time, using sediments from the Stepovogo Fjord waste dumping site, on the east coast of Novaya Zemlya. Results show that 134Cs ions interact rapidly with the surfaces of the Stepovogo sediment, with an estimated distribution coefficient Kd(eq) of 300 ml/g (or 13m2/g), and the 134Cs ions are increasingly irreversibly fixed to the sediment over time. For the first time, stochastic theory has been utilised for sediment-seawater systems to estimate the mean residence times (MRTs) of Cs ions in operationally defined sediment phases described by compartment models. In the present work, two different stochastic models (i) a Markov process model (MP) being analogous to deterministic compartment models, and (ii) a semi-Markov process model (SMP) which should be physically more relevant for inhomogeneous systems, have been compared. As similar results were obtained using the two models, the less complicated MP model was utilised to predict the time needed for an average Cs ion to become irreversibly fixed in the Stepovogo sediments. According the model, approximately 1100 days of contact time between Cs ions and sediments is needed before 50% of the 134Cs ion becomes fixed in the irreversible sediment phase. while about 12.5 years are needed before 99.7% of the Cs ions are fixed. Thus, according to the model estimates the contact time between 137Cs ions leached from dumped waste and the Stepovogo Fjord sediment should be about 3 years before the sediment will act as an efficient permanent sink. Until then a significant fraction of 137Cs should be considered mobile. The stochastic modelling approach provides useful tools when assessing sediment-seawater interactions over time, and should be easily applicable to all sediment-seawater systems including a sink term.

Cesium↗
PubMedDate not supplied

Accelerator mass spectrometry measurement of 240Pu/239Pu isotope ratios in Novaya Zemlya and Kara Sea sediments.

Generally low levels of plutonium in environmental samples, often combined with limited sample sizes, necessitate reliable low-level techniques for determination of Pu isotopes. Accelerator mass spectrometry (AMS) has proved to be a powerful method for measuring low-level Pu activity concentrations and Pu isotope ratios. Based on procedural blanks, detection limits for AMS were below 1 fg Pu (equivalent to ca. 2 microBq 139Pu), which can compete with both TIMS, high sensitivity ICP-MS, and certainly alpha-spectrometry, while showing less interference, memory and matrix effects as compared to routine ICP-MS techniques. In addition to low detection limits, the technique offers the advantage of giving information on Pu isotope ratios. Measurements of sediments collected from dumping sites at Novaya Zemlya showed deviation from global fallout 240Pu/239Pu ratios.

Environmental Monitoring↗