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The development of antifouling coating for sensor is desirable because the biofilm can shorten sensor’s life and cause inaccurate reading. In this study, a facile one-pot reaction was used to synthesized ZnO–graphene oxide (GO) (ZnO–GO) nanocomposites. Different amount of ZnO–GO was incorporated in the polydimethylsiloxane (PDMS) matrix respectively though a simple solution mixing method, in order to create PDMS/ZnO–GO nanocomposite (PZGO). The coating was obtained directly by spin coating of PZGO/tetrahydrofuran suspension. The hydrophobicity, surface roughness (Ra), surface free-energy (SFE) and nanoscale structure were investigated as antifouling factors. Antifouling tests were performed using two marine microorganisms, the cyanobacterium Synechococcus sp. Strain PCC 7002 and the diatom Phaeodactylum tricornutum. PZGO0.2 (mass ratio of ZnO–GO to PDMS: 0.2 wt%) displayed excellent antifouling property with 8.5% of Synechococcus sp. Strain PCC 7002 biofilm coverage, while PZGO0.1 (mass ratio of ZnO–GO to PDMS: 0.1 wt%) showed 2.4% P. tricornutum biofilm coverage. The antifouling property of the synthesized PZGO nanocomposite can be attributed to its high Ra and hydrophobicity which was caused by the good dispersion of ZnO–GO in PDMS matrix. This study suggests a potential of PZGO nanocomposite for sensor’s antifouling coating, which could contribute to improve sensor’s durability relating to biofouling in future. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

These days, sensors are widely used in a variety of underwater sites like marine monitoring, fish-farming and water quality monitoring. However, to achieve reliable sensor data from long-term monitoring in aqueous solution, several challenges still need to be solved. Biofilm formation both on sensor housings and membranes is among one of the most serious challenges, which strongly influences the sensor responds and the validity of the results. To prevent biofilm growth, a series of graphene oxide (GO)/silver nanoparticles (Ag NPs) nanocomposites (GOA) have been developed and coated on sensor housing materials, e.g. polypropylene. The antifouling property of the GOA nanocomposite has been demonstrated by antifouling tests using Halomonas. Pacifica (Baumann et al.) Dobson and Franzmann (ATCC® 27122) (H. Pacifica) and a mixture of marine algae. The antifouling property of GOA composites has been proved to be closely related to the dispersibility of Ag NP. The overall work might provide valuable insight into developing antifouling materials for sensors in general.

Experiments examining mercury (Hg) toxicity in Daphnia are usually conducted in highly standardized conditions that prevent the formation of biofilm. Although such standardization has many advantages, extrapolation of results to natural conditions and inference of ecological effects is challenging. This is especially true since biofilms can accumulate metals/metalloids and play a key role in their transfer to higher trophic level organisms. In this study, we experimentally tested the effects of spontaneously appearing biofilm in Daphnia cultures on accumulation of Hg and its natural antagonist selenium (Se) in Daphnia magna. We added Hg (in the form of mercury (II) chloride) at two concentrations (0.2 µg/L and 2 µg/L) to experimental microcosms and measured the uptake of Hg and Se by D. magna in the presence and absence of biofilm. To test for consistent and replicable results, we ran two identical experimental sets one week apart. Biofilm presence significantly reduced the accumulation of Hg, while increasing the tissue Se content in D. magna, and these findings were reproducible across experimental sets. These findings indicate that highly standardized tests may not be adequate to predict the bioaccumulation and potential toxicity of metals/metalloids under natural conditions.

In land-based recirculating aquaculture systems (RAS), the accumulation of dissolved organic matter (DOM) can have detrimental effects on water quality impacting the system performance, microbial community, and consequently fish health and welfare. Ozone is used in the RAS water treatment process to improve water quality and remove DOM. However, little is known about the molecular composition of DOM in RAS and its transformation when exposed to ozone. In this study, we performed a detailed molecular characterization of DOM in RAS and explored its transformation induced by ozonation of RAS waters. Ultra-high resolution (UHR) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) was used to characterize the DOM matrix of RAS waters (pump-sump and tanks) and to evaluate its transformation by ozonation. The analysis of DOM extracted from makeup water and feed samples allowed for the determination of DOM sources in RAS prior to ozonation. The CHO and unsaturated group of compounds were the most abundant class found in water samples. On the contrary, the DOM from feed samples was unique and consisted mainly of CHO, CHON and unsaturated group of compounds. After the ozonation of RAS waters, humic-like and unsaturated compounds [positive oxygen subtracted double bond equivalent per carbon (DBE–O)/C)] were decomposed, particularly the CHO-DOM that contained fewer -CH2- features. Fulvic-like compounds and several hundred saturated compounds [negative (DBE–O)/C)] were formed post ozonation, particularly the CHON and CHONS group of compounds that were associated with fish diets, makeup waters and transformation products from the ozonation of the RAS waters. This study showed that the high accuracy of the ultra-high resolution FTICR MS can be applied to characterize and monitor the changes of DOM at a molecular level in RAS waters. To our knowledge, this is the first study where FTICR MS was incorporated for the characterization of DOM and its sources in RAS.

Maintaining a steady sample temperature when analyzing real-time samples in the field is crucial for Membrane Introduction Mass Spectrometry (MIMS). Diffusion through the membrane interface is temperature dependent, and sample temperature might vary depending on the sample source. In order to reduce this source of inaccuracy, an in-field and online continuous monitoring system based on (MIMS) coupled with a heat exchanger and in-line standard addition was developed for monitoring volatile organic compounds (VOC) in actual field samples. Parametric studies of the heat exchanger have been conducted in the laboratory. In order to maintain control on instrumental signal drift during continuous, long-term analysis periods, the system used continuous infusion of internal standard (tuloene-d8) into the sample stream and also provided the possibility to infuse, in the same way, an analyte for standard addition calibration. This set-up has been utilized in the field for analyzing both natural water sources and heavily polluted process water. The system was demonstrated to offer a rapid method for quantifying volatile hazardous pollutants in aqueous matrices with good time-resolution. This work was supported in part by funding from Statoil ASA (Grand No 4502457485). This is an electronic copy of an article originally published as: Martinsen, M.R., Davey, N.G., Bell, R.J., Krogh, E.T., Gill, C.G., Mikkelsen, Ø., & Schmid, R. (2020). A field portable membrane introduction mass spectrometer with in-line standard infusion and sample heat exchanger for real-time monitoring of volatile organic compounds in aqueous samples. Environmental Chemistry and Ecotoxicology, 2, 168-174. https://doi.org/10.1016/j.enceco.2020.09.003 https://viurrspace.ca/bitstream/handle/10613/23379/KroghGillECE2020.pdf?sequence=3

Nitrifying biofilms developed in brackish water are reported to be more robust to salinity changes than freshwater biofilms. This makes them a promising strategy for water treatment systems with variable salinity, such as recirculating aquaculture systems for Atlantic salmon. However, little is known about the time required for nitrification start-up in brackish water or the microbial community dynamics. To investigate the development of nitrifying biofilms at intermediate salinity, we compared the startup of moving bed biofilm reactors with virgin carriers in brackish- (12‰ salinity) and freshwater. After 60 days, the brackish water biofilm had half the nitrification capacity of the freshwater biofilm, with a less diverse microbial community, lower proportion of nitrifiers, and a significantly different nitrifying community composition. Nitrosomonas and Nitrosospira-like bacteria were the main ammonia oxidizers in the brackish water biofilms, whereas Nitrosomonas was dominant in freshwater biofilms. Nitrotoga was the dominant nitrite oxidizer in both treatments. Despite the lower nitrification capacity in the brackish water treatment, the low ammonia and nitrite concentration with rapidly increasing nitrate concentration indicated that complete nitrification was established in both reactors within 60 days. The results suggest that biofilms develop nitrification in brackish water in comparable time as in freshwater, and brackish start-up can be a strategy for bioreactors with varying salinity. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

While aquaculture is growing rapidly all over the world and generating many economic benefits, so have the environmental concerns about the externalities posed by the fish-farming industry. The distribution profiles of organic compounds and inorganic elements were explored in marine surface sediments collected in proximity of two active Norwegian fish farms, Hestøya and Nørholmen (200-1100 m from the perimeter edge of the installations). Overall, the sediment organic matter (SOM) content was 7.3 ± 4.9%, with 7.9 ± 5.1% and 4.0 ± 0.5% for Hestøya and Nørholmen, respectively. A non-targeted analysis was performed for screening organic compounds in marine sediments, and the presence of 60 compounds was detected. Among suspect compounds were alkanes, alkenes, aromatics, aldehydes, ketones, esters, alcohols, diols, polycyclic aromatic hydrocarbons (PAHs), terpenes and terpenoids. Heptanal, benzaldehyde, 4-oxoisophorone, 1,7-dimethylnaphthalene and 3-bromophenol were the most abundant compounds in marine sediments. In total, concentrations of 47 elements were measured, concentrations of As, Cd, Cr, Cu, Hg, Mo, Ni, Sn and Zn were strongly influenced by anthropogenic inputs, while concentrations of Ce, Co, Al, Fe and Ti were related to the geology of the local bedrock. The chemical composition of marine sediments was different at Hestøya and Nørholmen, indicating different anthropogenic inputs in these areas. In general, concentrations of toxic elements were below the proposed guidelines for Norwegian marine sediment quality and can be characterised as background pollution. Overall, fish-farming activities had only a minor or negligible influence on marine sediments and are unlikely to cause any harm to local aquatic life in the studied area.

With increasing freshwater scarcity and greater use of seawater, fluctuating salinities are becoming common in water treatment systems. This can be challenging for salinity-sensitive processes like nitrification, especially in recirculating aquaculture systems (RAS), where maintaining nitrification efficiency is crucial for fish health. This study was undertaken to determine if prior exposure to seawater (priming) could improve nitrification in moving bed biofilm reactors (MBBR) under salinity increase from freshwater to seawater. The results showed that seawater-primed freshwater MBBRs had less than 10% reduction in nitrification activity and twice the ammonia oxidation capacity of the unprimed bioreactors after seawater transfer. The primed biofilms had different microbial community composition but the same nitrifying taxa, suggesting that priming promoted physiological adaptation of the nitrifiers. Priming may also have strengthened the extrapolymeric matrix protecting the nitrifiers. In MBBRs started up in brackish water (12‰ salinity), seawater priming had no significant impact on the nitrification activity and the microbial community composition. These bioreactors were inherently robust to salinity increase, likely because they were already primed to osmotic stress by virtue of their native salinity of 12‰. The results show that osmotic stress priming is an effective strategy for improving salinity acclimation in nitrifying biofilms and can be applied to water treatment systems where salinity variations are expected.

Recirculating aquaculture systems (RAS) are a new alternative to traditional aquaculture approaches, allowing full control over the fish production conditions, while reducing the water demand. The reduction of water exchange leads to an accumulation of dissolved organic matter (DOM) that can have potential effects on water quality, fish welfare and system performance. Despite the growing awareness of DOM in aquaculture, scarce scientific information exists for understanding the composition and transformation of DOM in RAS. In this study, a non-targeted approach using ultra-performance liquid chromatography coupled to a hybrid quadrupole-time of flight mass spectrometer (UPLC-QTOF-MS) was used to characterize compositional changes of low molecular weight (LMW) DOM in RAS, when operated under two different feed types. A total of 1823 chemicals were identified and the majority of those contained a CHON chemical group in their structure. Changes in the composition of LMW-DOM in RAS waters were observed when the standard feed was switched to RAS feed. The DOM with the use of standard feed, consisted mainly of lignin/CRAM-like, CHO and CHOS chemical groups, while the DOM that used RAS feed, was mainly composed by unsaturated hydrocarbon, CHNO and CHNOS chemical groups. The Bray-Curtis dissimilarity cluster demonstrated differences in the composition of DOM from RAS and was associated to the type of feed used. When the RAS feed was used, the Kendrick mass defect plots of –CH2- homologous units in the pump-sump (after the water treatment) showed a high removal capacity for CHNO, CHNOS and halogenated chemicals with high Kendrick mass defect, KMD > 0.7. To our knowledge, this is the first report of LMW-DOM characterization of RAS by high-resolution mass spectrometry (HRMS). This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Despite being a remote location, the Arctic is a major receptor for anthropogenic pollution transported from the mid-latitudes. Vegetation and underlying organic soils in the Norwegian Arctic, Svalbard were used to study the occurrences of polychlorinated biphenyls (PCBs) and trace elements. In this study, current concentrations of PCBs and trace elements, namely, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, S, Sb, U and Zn in the terrestrial compartments of Svalbard are presented. Samples were collected from Adventdalen near Longyearbyen and from areas in proximity to Ny-Ålesund. There was significant variability in soil organic matter (SOM) among the soils analysed (5.0%–72.1%), with the highest values detected in Ny-Ålesund. The concentrations of Al, As, Cr Cu, Fe, Pb and Ni were associated with the geology of the local bedrock. The concentrations of all elements, except for Cd, Hg and Zn, were higher in soils than those in the overlying vegetation layers. Mean concentrations of ∑PCBs were significantly higher in vegetation (6.90 ± 0.81 ng g−1 dw) than the underlying organic soils (3.70 ± 0.36 ng g−1 dw). An inverse correlation of PCBs with the elements originating from the local bedrock indicated that their concentrations were potentially impacted by atmospheric deposition. PCBs and Cd were strongly associated, proposing a potential concomitant source of origin in Svalbard. Concentrations of PCBs and trace elements measured herein were below the proposed guidelines for Norwegian soil quality. Trace elements and polychlorinated biphenyls (PCBs) in terrestrial compartments of Svalbard, Norwegian Arctic © 2019 The Authors. Published by Elsevier B.V. Open Access CC BY-NC-ND 4.0

Ramming paste is a particular type of carbon paste which is used as lining for electric smelting furnaces and Hall-Heroult cells for the production of aluminium. The purpose of this lining is to form an impenetrable barrier, keeping the liquid within the furnace. If the lining has cracks or holes, then liquid can escape, which can lead to safety risks and financial losses, so the integrity of the lining is of great importance. In the present study, we develop a first principles mathematical model for the heat and mass transfer processes occurring during the baking of carbon paste. We then obtain numerical simulations using this model and compare the simulation results to experimental data, demonstrating that the model solutions do indeed describe and predict realistic behaviours of the carbon paste baking process. The simulations indicate a strong pressure buildup during the evaporation of water from fresh paste during the baking process, which is likely to lead to cracking of the paste as it hardens. Furthermore, we are able to show that more gradual heating during the baking process can lower the maximal pressures predicted by the model, which in turn may reduce the prevalence of cracks within the hardened paste.

Svalbard is an important study area for investigating the long-range transport of mercury (Hg) and other trace elements to the Arctic. Few studies have focused on their concentrations in Arctic soils. With ongoing climate change leading to thawing permafrost ground the soil compartment is of increasing importance in the Arctic. In this study, elemental composition and soil organic matter (SOM) content of surface and mineral soils in Svalbard are presented. The aim is to provide new data on soils in the Arctic and to gain more knowledge about the role of the soil in the biogeochemical cycle of mercury (Hg). Concentrations are reported for Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, S and Zn. Samples were taken in Adventdalen and in the area near Ny-Alesund. We obtained a mean Hg concentration of 0.111 ± 0.036 μg/g in surface soils (range 0.041–0.254 μg/g). Hg levels in mineral soils (mean: 0.025 ± 0.013 μg/g; range: 0.004–0.060 μg/g) were substantially lower than in the corresponding surface soils. Hg strongly accumulates in the surface soil layer (upper 3 cm) and is associated with SOM (surface soil: 59 ± 14%). Hg concentrations in the surface soil were slightly lower than those in the humus layer in mainland Norway and were comparable to levels in soils elsewhere in the Arctic. An inverse association of Hg was found with elements attributed to the mineral soil, indicating that Hg is predominantly derived from atmospheric deposition.

The objective of the present work was to assess depth-related variations in the (bio)geochemical processes involved in anoxic sediments from the Deule river, and to examine particularly their impacts on the distribution of anthropogenically sourced metals. Anoxic sediment samples were sliced and analyzed to determine total concentrations vs. depth of elements and corresponding pore waters were analyzed to determine concentration profiles with depth of pH, Eh, alkalinity, O2, dissolved organic carbon (DOC), and main inorganic anions and cations present in the medium. It was shown that rapid depletions of O2, NO 3 - and SO 4 2 - , accompanied with HCO 3 - generation and a sharp decrease in the redox potential occurred within the first centimeters of the surface sediment as a consequence of early diagenesis. Bacterial reductive dissolution of Mn(III and IV) and Fe(III) oxides/hydroxides to Mn(II) and Fe(II) accompanied by microbial degradation of organic matter took place as well, and resulted in trace metal increases in the pore water at levels that raised the possibility of mineral generation. Thermodynamic calculations predicted removal of metals from interstitial waters through combinations with carbonates and/or sulfides. These took place either by direct precipitation to form pure crystals, or by coprecipitation/sorption with/into calcite and with pyritic compounds. Chemical sequential extraction data were useful in this work to support, at least partially, some thermodynamic predictions concerning the existence of interactions between trace metals and carbonate and sulfide ions to generate (co)precipitates. Electron paramagnetic resonance (EPR) studies on Deule sediments revealed the presence of Mn(II) adsorbed onto sedimentary calcite surfaces. X-ray diffractograms of heavy minerals from Deule sediments extracted with CHBr3 by density separation exhibited peaks ascribed to galena, sphalerite and pyrite. In addition to these compounds, using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), micro-analyses of sedimentary heavy minerals confirmed successfully the existence of other thermodynamically predicted associations: covellite; chalcopyrite, greenockite and/or amorphous CdS.

Nafion coated silver amalgam electrode for determination of trace metals by anodic stripping voltammetry

Detection of Mn(II) using differential pulse anodic stripping voltammetry (DPASV) on solid silver amalgam electrode is introduced. A well-defined peak for the oxidation of Mn(0) to Mn(II) was observed around −1.45 V in NH4Cl (0.05 M) solution. Concentrations down to 1 μg/L were measured in NH4Cl (0.05 M) with 900 s deposition time at −1.70 V, and good linearity was observed (r=0.993) for standard additions in different concentration ranges (1–3 μg/L, 10 μg/L–60 μg/L, and 50 μg/L–250 μg/L). For all measurements relative standard deviation was within 5% (n=9). Interactions between Mn and Cd, Ni, Cu, Pb and Zn were examined, and it was found that lead and nickel significantly interfere, while zinc, cadmium, copper, and mercury did not interfere within reasonable concentration ranges. The method was demonstrated for online detection of manganese in a contaminated river where the Mn(II) concentration varied between 3 and 15 μg/L. The relation between the Mn(II) concentration in the river water and the vessel traffic was observed due to the presence of high concentrations of Mn(II) in anoxic pore waters.

Electrochemical properties for mixed gold-bismuth electrodes have been evaluated. Increased overpotential towards the hydrogen evolution reaction (HER) was found as a function of increased bismuth content in the gold-bismuth mixture. Compared to a bare gold electrode, the overvoltage was increased by 80 mV for gold with 2% bismuth added (AuBi2), 170 mV for 6% bismuth added (AuBi6), and 580 mV for 25% bismuth added (AuBi25). Cyclic voltammetry (CV) in a NaOH solution was also carried out to study the formation of different oxide products on the surface. The practical use of such electrodes was demonstrated by differential pulse anodic stripping voltammetry (DPASV) for the detection of copper and mercury, and good linearity was found even for concentrations down to 0.25 μg/L. In addition to stability tests in NH4Cl, the analytical use and stability over time were evaluated in purified scrubbing water and polluted river water.

Voltammetry is one of a few analytical methods, suitable for on-line monitoring of trace metals and is sufficiently sensitive in the low μg/L range for this purpose. The advantages of in-situ use of voltammetry are low cost and no or minimal sample change, since the sample is taken automatically and analysis is performed immediately without a need to collect a sample manually risking contamination and metal loss. Automatic monitoring is essential to record the natural variations of metal concentration in natural or industrial water and registration of accident due to natural or anthropogenic reasons. Remote monitoring of trace metals is of special importance due to their biological role. For that reason extensive research has been carried out internationally to develop suitable monitoring methods. The introduction of the innovative solid silver amalgam and other solid metal electrodes made the use of voltammetry suitable for remote monitoring without the use of toxic electrode materials. An automatic trace metal system (ATMS) in combination with solid silver amalgam electrode has been applied for long time monitoring of zinc and iron in waste water. The system worked automatically with manual maintenance every five days. Sample taking, addition of electrolyte solution, stirring, chemical analysis, electrode cleaning and cell draining were carried out automatically, while electrode polishing, filter changing and calibration were carried out manually every five days. For comparison, verification and to provide a better insight into the complex waste water matrix manual samples have been taken regularly and analyzed with ICP-MS. From data obtained from those two analytical methods a speciation study was performed. The automatic voltammetric system for continuous monitoring of trace metals has been applied in three different locations for monitoring of trace metals in different water samples. River water and drainage water has been used as complex natural water matrixes. A solid silver amalgam electrode has been used as a working electrode. The systems have been fully automated to measure the labile concentration of trace metals for a long time monitoring and store the collected data. Manual maintenance has been performed to calibrate the systems and to clean the working electrodes. Additionally, random samples have been collected manually and analyzed by ICP-MS for the total dissolved metal concentration for data verification and getting better insight into sample matrix. Development of the ATMS has provided an opportunity to monitor earthquake precursor in ground water. A monitoring station has been installed in Husavik, Northern Iceland, for monitoring of trace metals in a ground water. The monitored concentration of metals clearly indicated changes in the ground water prior to the earthquake. The results revealed increased electrolabile concentrations of zinc, iron and copper 7-8 days before the earthquake. The increased concentrations lasted until the occurrence of the earthquake and were possible to monitor by the ATMS. The characterization and application of a Nafion coated solid silver amalgam electrode has been tested for the determination of trace metals by differential pulse anodic stripping voltammetry (DPASV). Effect of model surfactants, commonly presented in natural water sources has also been investigated. It has been found that Nafion coated electrode is useful in surfactant containing samples. The performance of the Nafion coated silver amalgam electrode has been investigated and compared to uncoated silver amalgam electrodes. The modification of the electrode yields higher sensitivity. Moreover, the long time use of Nafion film and practical application has been tested by the use of DPASV in polluted river water sample and has shown to work optimal for 2 weeks. New electrodes made of silver germanium and silver antimony have been tested and found to be suitable for determination of metals by DPASV with very good linearity. This type of electrodes extends potential window to both positive and negative direction. Additionally, very good sensitivity for cadmium has been observed. The practical application has been tested for applying the electrodes in monitoring station to monitor zinc concentration in polluted river water. Moreover, Nafion coating has been applied and has been found to be advantageous considering electrode stability. The aim of this work has been to test silver amalgam and other solid metal electrodes for application in natural and environmental water samples for use in long time online monitoring in field. The papers included in this thesis prove successful applications of these electrodes in different environmental matrixes. The results provide positive evidence about the ability of voltammetry in combination with solid metal electrodes (bare and modified with Nafion) as a working electrodes to be employed in automatic monitoring of trace metals in polluted water with minimal sample pretreatment and minimal maintenance of the system. The use of solid metal electrodes avoids the use of liquid mercury in voltammetric analyses, and offers an environmental friendly alternative suitable for use in field. Due to ease to use, nontoxic fabrication materials, wide cathodic potential window, long time stability, and good sensitivity these electrodes can be applied for continuous online monitoring in various environmental and industrial solutions. They are also easy to modify and this extends the application even further. Several experimental projects at different locations and in different water samples (river-, sea-, ground-, drainage- and waste water) have shown sufficiently long time stability without the need for physical presence for maintenance. These results strongly indicate that further developed and improved method may in future be used as a commercial warning system for environmental pollution accidents.

Voltammetry is one of a few analytical methods, suitable for on-line monitoring of trace metals and is sufficiently sensitive in the low μg/L range for this purpose. The advantages of in-situ use of voltammetry are low cost and no or minimal sample change, since the sample is taken automatically and analysis is performed immediately without a need to collect a sample manually risking contamination and metal loss. Automatic monitoring is essential to record the natural variations of metal concentration in natural or industrial water and registration of accident due to natural or anthropogenic reasons. Remote monitoring of trace metals is of special importance due to their biological role. For that reason extensive research has been carried out internationally to develop suitable monitoring methods. The introduction of the innovative solid silver amalgam and other solid metal electrodes made the use of voltammetry suitable for remote monitoring without the use of toxic electrode materials. An automatic trace metal system (ATMS) in combination with solid silver amalgam electrode has been applied for long time monitoring of zinc and iron in waste water. The system worked automatically with manual maintenance every five days. Sample taking, addition of electrolyte solution, stirring, chemical analysis, electrode cleaning and cell draining were carried out automatically, while electrode polishing, filter changing and calibration were carried out manually every five days. For comparison, verification and to provide a better insight into the complex waste water matrix manual samples have been taken regularly and analyzed with ICP-MS. From data obtained from those two analytical methods a speciation study was performed. The automatic voltammetric system for continuous monitoring of trace metals has been applied in three different locations for monitoring of trace metals in different water samples. River water and drainage water has been used as complex natural water matrixes. A solid silver amalgam electrode has been used as a working electrode. The systems have been fully automated to measure the labile concentration of trace metals for a long time monitoring and store the collected data. Manual maintenance has been performed to calibrate the systems and to clean the working electrodes. Additionally, random samples have been collected manually and analyzed by ICP-MS for the total dissolved metal concentration for data verification and getting better insight into sample matrix. Development of the ATMS has provided an opportunity to monitor earthquake precursor in ground water. A monitoring station has been installed in Husavik, Northern Iceland, for monitoring of trace metals in a ground water. The monitored concentration of metals clearly indicated changes in the ground water prior to the earthquake. The results revealed increased electrolabile concentrations of zinc, iron and copper 7-8 days before the earthquake. The increased concentrations lasted until the occurrence of the earthquake and were possible to monitor by the ATMS. The characterization and application of a Nafion coated solid silver amalgam electrode has been tested for the determination of trace metals by differential pulse anodic stripping voltammetry (DPASV). Effect of model surfactants, commonly presented in natural water sources has also been investigated. It has been found that Nafion coated electrode is useful in surfactant containing samples. The performance of the Nafion coated silver amalgam electrode has been investigated and compared to uncoated silver amalgam electrodes. The modification of the electrode yields higher sensitivity. Moreover, the long time use of Nafion film and practical application has been tested by the use of DPASV in polluted river water sample and has shown to work optimal for 2 weeks. New electrodes made of silver germanium and silver antimony have been tested and found to be suitable for determination of metals by DPASV with very good linearity. This type of electrodes extends potential window to both positive and negative direction. Additionally, very good sensitivity for cadmium has been observed. The practical application has been tested for applying the electrodes in monitoring station to monitor zinc concentration in polluted river water. Moreover, Nafion coating has been applied and has been found to be advantageous considering electrode stability. The aim of this work has been to test silver amalgam and other solid metal electrodes for application in natural and environmental water samples for use in long time online monitoring in field. The papers included in this thesis prove successful applications of these electrodes in different environmental matrixes. The results provide positive evidence about the ability of voltammetry in combination with solid metal electrodes (bare and modified with Nafion) as a working electrodes to be employed in automatic monitoring of trace metals in polluted water with minimal sample pretreatment and minimal maintenance of the system. The use of solid metal electrodes avoids the use of liquid mercury in voltammetric analyses, and offers an environmental friendly alternative suitable for use in field. Due to ease to use, nontoxic fabrication materials, wide cathodic potential window, long time stability, and good sensitivity these electrodes can be applied for continuous online monitoring in various environmental and industrial solutions. They are also easy to modify and this extends the application even further. Several experimental projects at different locations and in different water samples (river-, sea-, ground-, drainage- and waste water) have shown sufficiently long time stability without the need for physical presence for maintenance. These results strongly indicate that further developed and improved method may in future be used as a commercial warning system for environmental pollution accidents.

A fast and simple differential pulse polarographic method was developed for analysis of nicotine in various pharmaceutical formulations (chewing gum, tablets (drops) and patches). This method requires a simple liquid-liquid extraction procedure for chewing gum and patches, or a direct dilution in supporting electrolyte for tablets before polarographic analysis. The polarographic analysis was done in a Britton-Robinson buffer (pH 6.2) as supporting electrolyte. The multimode electrode from Metrohm was used as working electrode (dropping mercury electrode). This method was applied to the determination of the nicotine content in chewing gum, tablets and patches by using the standard addition method. The results are in good agreement with the content declared by the manufacturer. The method is fast, simple and reliable, and it is a complementary method to the chromatographic method being used today for quantitative analysis of nicotine in pharmaceutical formulations. The limit of quantification is assumed to be far below 0.1 mg/l in the polarographic vessel. The method uses simple dilution and/or extraction procedures for sample preparation before polarographic analysis. It is also shown that it is possible to use a glassy carbon electrode with a mercury film (MTFE electrode) for the determination of nicotine in antismoking pharmaceutical products.

A new method is presented for the determination of electrochemically labile iron in estuarine and coastal seawater. The method is based on differential pulse anodic stripping voltammetry (DPASV) at a rotating silver-alloy disk electrode. The voltammetric parameters include a plating potential of −1.5 V and an activation potential of −5 V for 10s; the seawater is at the original sample pH. The main finding is the presence of a peak for low nmol L−1 levels of iron at −0.55 V ascribed to elemental iron deposited on the bare silver alloy electrode. The peak increased linearly with the iron concentration between

Electrochemical properties of silver electrodes with 2, 4, 6, 10 and 15% bismuth have systematically been investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Increased overpotential towards hydrogen evolution reaction (HER) was found as a result of increasing amount of added bismuth. This was also demonstrated in acid solution where zinc was successfully detected on mixed electrodes, but failed on pure silver electrodes. Formation and decomposition of oxide products formed on the different electrode surfaces were studied by cyclic voltammetry, and in addition to known species found on sliver, also peaks attributed to bismuth were achieved and examined. Zinc, cadmium, and lead were measured in the low μg/L range on the mixed electrodes, and good linearity (r2=0.998) was found for 2 to 10 μg/L. Lead was measured down to 0.1 μg/L. Further it was found in DPASV that the zinc peak significantly shifted towards a more negative value with increasing amount of bismuth in the silver electrodes. The same was also observed for cadmium and lead, but in a less extent. Finally a silver electrode containing 15% bismuth was used for continuous analyses in a polluted river for 6 weeks.

An automated voltammetric system using solid electrodes was investigated for continuous and on-line remote monitoring of heavy metals in natural waters. Both a polluted river impacted by a copper mine, and costal seawater were monitored automatically every 30 minutes for six months. The huge difference in these two locations demonstrates the wide application range for this system. Results have been automatically monitored every thirty minutes for six months, and can be correlated against a range of parameters, e.g., season, flow of water, temperature, pH etc.

A simple method for detection of zinc and lead in wine by use of potentiometric stripping analyses (PSA) on the dental amalgam electrode is introduced and demonstrated for 10 different wines, both red and white. The combination of PSA and the novel nontoxic electrode offers a fast and easy‐to‐use technique without matrix effects seen in, e.g., voltammetry. Concentrations of zinc in the range of approximately 2.1 × 10−6 M to 11.7 × 10−6 M (3.5% std. dev.) and lead in the range of 9.7 × 10−8 M to 2.4 × 10−7 M (3.5% std. dev.) were found in the actual wine samples. PSA measurements were verified against atomic adsorption spectroscopy analyses (AAS), and a good correlation factor was found (r 2 = 0.96). A simple speciation study was performed by measuring the amount of zinc and lead before and after the addition of acid, giving an approximate ratio between free and total amount of the metals. Estimated detection limits for zinc and lead were calculated to, respectively, 3.0 × 10−7 M and 1.5 × 10−8 M ...

X-ray absorption spectroscopy (X-ray absorption near-edge structure including pre-edge features and extended X-ray absorption fine structure studies) and cyclic voltammetry analyses were used to study copper substituted manganese oxide octahedral molecular sieve (Cu-OMS) microporous materials. The results from the X-ray absorption spectroscopy study have been interpreted in terms of possible locations of Cu2+ ions in the microporous zeotypic OMS-2 structure. According to the synthetic route, the Cu2+ ions are expected to interact with the surface atoms, and do not replace any of the framework atoms. The results are consistent with copper interacting with lattice oxygen and manganese atoms, and are therefore, also consistent with copper being sited within the channels of OMS-2. Qualitative pre-edge studies on manganese in copper doped OMS-2 show octahedral Mn4+. The latter confirmed by cyclic voltammetric analyses giving similar voltammograms as for the manganese dioxide and non-mobility for Mn2+ in the OMS-2 material.

A striking example of plasticity in life span is seen in social insects such as ants and bees, where different castes may display distinct ageing patterns. In particular, the honeybee offers an intriguing illustration of environmental control on ageing rate. Honeybee workers display a temporal division of labour where young bees (or 'hive bees') perform tasks within the brood nest, and older bees forage for nectar, pollen propolis and water. When bees switch from the hive bee to the forager stage, their cellular defence machinery is down-regulated by a dramatic reduction in the number of functioning haemocytes (immunocytes). This study documents that the yolk precursor vitellogenin is likely to be involved in a regulatory pathway that controls the observed decline in somatic maintenance function of honeybee foragers. An association between the glyco-lipoprotein vitellogenin and immune function has not previously been reported for any organism. Honeybee workers are functionally sterile, and via the expression of juvenile hormone, a key gonotrophic hormone in adult insects, their vitellogenin levels are influenced by social interactions with other bees. Our results therefore suggest that in terms of maintenance of the cellular immune system, senescence of the honeybee worker is under social control.

Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni-Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at -375 mV, and a linear response was found in the range 0.2-1.2 mg L(-1) (r(2)=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low microg L(-1) range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver-bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r(2)=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the microg L(-1) range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H(2)SO(4) to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed.

Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising.

An automatic trace metal monitoring station (ATMS) have been implemented in the river bank of the Deule canal in the city of Auby (northern France), in the vicinity of metallurgical industries that have heavily polluted sediments, in Cd, Pb and Zn. Additionally, the fluvial traffic in this river is intense and surface sediments are resuspended several times per day. This paper is the following part of that published recently (Superville et al., 2014) in this journal. The main purpose of this paper is to present new information on diel and seasonal variations of trace metals in the Deule River and highlight the potential role of sediments in the contamination of the water column. To this end, Cd, Zn and Pb were monitored at a high frequency (~ 1 h − 1 ) by voltammetry, distinguishing an electrolabile and an acid-leachable fraction. Our measurements revealed that (i) acid-leachable Cd is mainly bound to light particles such as clays and carbonates and its daily behaviour does not really depend on the intensity of sediment remobilisation process; (ii) acid-leachable Pb and Zn exhibit some seasonal variations which are explained here, suggesting they should at least partly depend on the ageing of hydrous ferric oxides in the sediments; (iii) in spring, the electrolability of Zn increases in agreement with the biological activity that may break some strong association between Zn and ligands and/or particles (e.g., organic matter, hydrous ferric oxides, etc.). This trend is observed for electrolabile Pb later in summer, but on a smaller scale since this metal is generally more strongly scavenged and less labile than Zn; and (iv) electrolabile Mn concentrations increase during the day due to desorption process of resuspended sediment particles in the water.

We have introduced a non-toxic electrode material similar to dental amalgam for use in voltammetry. Its electrochemical properties are like a silver electrode. However, it possesses a higher overvoltage towards hydrogen than silver, and therefore enables detection of metals like zinc, nickel and cobalt. As such solid electrodes are found to give stable results over several weeks, without any maintenance, and because this method greatly facilitates monitoring of heavy metals, attempts to apply such methods to various samples have been are carried out. The present paper deals with the determination of zinc and lead at nanogram per milliliter levels in wines and spirits with only minor treatment of the samples. The procedure may easily be adapted to continuous monitoring. We have previously found that audible sound may greatly increase the voltammetric signal using liquid mercury as well as silver as electrode material. This is also applied to the actual systems. Finally, model determinations of thallium in brandy with the dental amalgam electrode are compared with atomic absorption spectrometric (AAS) measurements. It was found that the electrode could be used repeatedly, without fouling, and with results close to those found by the AAS method.

Issues concerning the use of mercury electrode in environmental analyses has led to considerable research effort aimed at finding alternative tools with acceptable performance. A renewing silver working electrode is investigated. This system has shown a good response to lead and cadmium. Concentrations as low as 10 µg L−1 have been detected for both ions in 0.1 M HCl solutions. The system shows also little interference from copper. A detection limit of 0.5 µg L−1 is estimated for these systems. The electrode system may be used repeatedly without maintenance over a considerable period of time as a new silver film is formed prior to each scan. The silver electrode has been excited, oscillated with both triangular and sinusoidal audio frequency waves. The results indicate that the reproducibility of the response is increased when the electrode is oscillated sinusoidally. A study of the oscillating frequency has also been carried out. The result shows that the detection sensitivity improved considerably when low frequencies typically in the range 40 to 80 Hz are used. Good detection sensitivity, along with the simplicity of use and maintenance renders this system potentially attractive for use in online and field instruments.

Liquid mercury and liquid mercury amalgams are superior electrode materials in voltammetry for analytical purposes. This is mainly due to the high overvoltage to hydrogen, which enables the detection of heavy metals with high negative half-wave potentials. Because of the toxicity of mercury and liquid mercury compounds, their use is increasingly restricted, and cannot be included in voltammetric devices for field and on-line applications. Authors have studied properties of dental amalgam as an electrode material in voltammetry. The results show that dental amalgam acts similarly to a silver electrode. Also, it has a high hydrogen overvoltage, allowing it to be used, e.g., for detection of zinc. In addition, due to special properties of dental amalgam compared with mercury itself, it is not toxic. New in this paper is the determination of nickel and cobalt on the dental amalgam electrode using adsorptive cathodic stripping voltammetry (AdCSV). Also, some new data on detection of zinc, cadmium, lead and thallium are presented. The results show that this electrode can be used over a long period of time without any maintenance, which is important for on-line analyses of pollutants in soil and groundwater.

Improvement of the sensitivity in trace analyses of about 300% without any increase in the noise level by use of low frequency sound in stripping voltammetry has been successfully carried out and reported in earlier articles. One problem in the former investigations was that the sound source was placed inside the analytical cell. This is inconvenient and gives a risk for contamination. In this article the sound source has been successfully moved out of the analytical cell. This has been made possible by mounting a loud speaker directly under the analytical cell made of inert plastic material that effectively allows the sound waves to be transferred into the analytic solution. This greatly improves the practical application, and the risk for cell contamination is reduced. The three-electrode system used in the experiments consist of a silver/silver chloride/saturated silver chloride/saturated potassium chloride reference electrode, a platinum wire counter electrode, and a mercury or glassy carbon working electrode. The aim of the present work was to investigate how the sound intensity effected the current signal. It was found that a logarithmic increase of the sound intensity resulted in an exponential increase in the current signal. The use of sound exposure to a glassy carbon electrode is also investigated, and results reported show a 60% increase in the current compared to analyses using magnetic stirrer. The standard deviation was found to be 3% for the sound exposed analyses. The enhancement in sensitivity together with the simplicity of using low frequency sound makes this method potentially attractive for use in on-line instruments.

Liquid mercury and liquid diluted mercury amalgams have been superior as electrode material for the use of voltammetry for analytical purposes. This is mainly due to the high overvoltage to hydrogen, which enables one to use a wide potential range for the measurements. Due to the toxicity of mercury and liquid diluted mercury compounds, the use of such compounds are increasingly restricted, and cannot be included in voltammetric devices for field and online applications. The present authors have studied the properties of dental amalgam and related solid amalgams as electrode material in voltammetry. Due to the special properties of dental amalgam compared with mercury itself it is not toxic. It has been found that dental amalgam and related solid amalgams have a very high overpotential to hydrogen, allowing one to carry out trace analyses at potentials sufficiently negative to allow determination of e.g. zinc, cobalt, nickel and iron at trace levels. This have previously been difficult except whe...

Improving the sensitivity of voltammetric analysis containing low metal concentrations has been attempted by exposure to low frequency sound. It was found that audible sound in the low frequency range, around 100 Hz was very effective for this purpose, with an increase of the analytical signal up to about 300%, without any significant increase in the corresponding noise level. Ordinary stirring has to be avoided during the voltammetric scanning due to the low reproducibility when stirring takes place. Sound exposure, however, can be performed during the entire measurement, and this explains the increased sensitivity. Further it is concluded that sound exposure close to the resonant frequency, has improvement effects at least comparable to stirring, and thus all mechanical stirring can be avoided. Differential pulse anodic stripping voltammetry with a three-electrode cell system was used with a static mercury drop electrode exposed by low frequency sound, a Pt counter-electrode and a silver/silver chloride/saturated silver chloride/saturated potassium chloride reference electrode. However, it is presumed that other modes of voltammetry than DPASV would show similar behavior when exposed to audible sound. Low frequency sound is assumed to influence the physical conditions in the vicinity of the electrode by diffusion layer thinning, to increase the surface concentration. Moreover, the simplicity of using audible sound, with high reproducibility of the measurements, makes this analytical method potentially attractive.

Tema/problemstilling Vi har sett på innføring av vaktpostlymfeknuteprosedyre (SLNB) hos pasienter med malignt melanom ved Oslo Universitetssykehus. Bakgrunnen for valget av oppgave var Helsedirektoratets handlingsprogram for malignt melanom fra 2011, der man anbefalte innføring av SLNB ved ekstremitetsmelanomer stadium IIA, i første omgang ved Universitetssykehusene. Flere sykehus har allerede implementert praksisen, men OUS er ikke et av disse. Dette til tross for at flere av forskerne involvert I utarbeidelsen av de nye retningslinjene har ledende stillinger i OUS. Kunnskapsgrunnlag I tillegg til å gjennomgå dokumentasjonen som ligger til grunn for Helsedirektoratets handlingsprogram, utformet vi et PICO-spørsmål og søkte I McMaster PLUS. Vi fant internasjonale retningslinjer i UpToDate, samt en meta-analyse og to primærstudier sitert i handlingsprogrammet. Vi har i tillegg vært i kontakt med flere professorer involvert i både Norsk Melanomgruppe og i helsedirektoratets arbeidsgruppe. Tiltak/kvalitetsindikator Vårt tiltak er å implementere de retningslinjene Helsedirektoratet allerede har gitt. Ut fra kunnskapsgrunnlaget mener vi dette vil gi pasientene økt residivfritt intervall, og hos dem som får påvist metastaser vil SLNB føre til tidligere lymfeknutetoalett som igjen er assosiert med høyere 5-års overlevelse. Da det er snakk om innføring av retningslinjer bruker vi en prosessindikator som kvalitetsindikator, nærmere bestemt andelen pasienter med ekstremitetsmelanom I stadium IIA som får utført en SLNB ved OUS. Ledelse/organisering Prosjektet gjennomføres ved Oslo Universitetssykehus. Til å lede prosjektet nedsettes en implementeringsgruppe bestående av avdelingsoverlege, LIS-lege, sykepleier, anestesilege, pasientkoordinator, radiolog og patolog. Grundig informasjon må gis til alle involverte parter, både gjennom møter og synlige oppslag. Vi ønsker å følge PDSA-sirkelen som mal for fremgangen i prosjektet, med John Kotters endringsstrategi i bunn. Vi har illustrert mulige utfordringer og motstand underveis i fiskebeinsdiagrammet, og skissert mulig håndtering av dette. Konklusjon Etter å ha satt oss inn i internasjonale retningslinjer og litteratur er det vår mening at det vil være til pasientenes beste å implementere Helsedirektoratets anbefaling om SLNB hos pasienter med ekstremitetsmelanomer I stadium IIA. I tillegg til gevinsten hos den enkelte pasient vil det muliggjøre forskning på området som kan gagne pasiengruppen på sikt. Også for sykehusets del mener vi økt ressursbruk her og nå oppveies av mindre sykdom og færre liggedøgn på sikt, og vi anbefaler at SLNB innføres ved Oslo Universitetssykehus hos den aktuelle pasientgruppen.

Study Design Literature review Objective The aim of this thesis is to compare the main classification systems available for classifying acute subaxial cervical spinal injury and compare their relative strengths and weaknesses, especially in their ability to guide treatment and predict prognosis. Methods A PICO question was formulated and used to select search terms. The search terms were used to search the online database Pubmed/Medline for English language review articles less than 10 years old. These were evaluated based on their abstracts and articles relevant to the PICO question were selected. The final 9 articles were studied and their bibliographies were searched for relevant secondary articles. Results Five main classification systems for acute subaxial cervical trauma were found (Holdsworth's classification, Allen's classification, Harris' classification, the subaxial cervical spine injury classification system (SLIC) and the cervical spine injury severity score (CSISS)). Conclusion By comparing the classification systems, it is evident that older classification systems (Holdsworth, Allen et al and Harris et al) have focused on the mechanisms of injury while newer classification systems (Vaccaro et al, Moore et al) have discarded this in favour of radiological findings and, in the case of Vaccaro et al, neurologic status. Comparisons of the classification systems show that there are clear advantages to the system presented by Vaccaro et al (SLIC scale) compared to previous systems because it may be used to guide treatment, however it has lower reliability and validity compared to the Allen and Harris systems. The CSISS has a higher interrater and intrarater reliability than the SLIC scale but is not suitable for guiding treatment for injuries with scores

An automatic trace metal monitoring station (ATMS) system was implemented to study seasonal and short time changes in selected metal concentrations in two river courses influenced by mine drainage. High frequency monitoring over periods of months revealed daily variations of zinc, iron and copper, and also proved the use of ATMS as an early warning system in such polluted environments. Complementary measurements with ICP-MS (inductively coupled plasma-mass spectrometry), ionic chromatography, and thermodynamic equilibrium calculations also gave some new insights into the geochemical behaviour of the metals in these two rivers.

Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare gold-disk microelectrodes of 25- and 125-μ m diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury-coated electrodes, with Zn always displaying 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at − 1.1 V, without stirring, the 25-μ m gold-disk microelectrode has a linear response for Cd, Cu, Mn, Pb and Zn from 0.2 μ g L− 1 (1 μ g L− 1 for Mn) to 20 μ g L− 1 (30 μ g L− 1 for Zn, Pb and 80 μ g L− 1 for Mn). Under the same analytical conditions, the 125-μ m gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 μ g L− 1 (5 μ g L− 1 for Cd) to 100 μ g L− 1 (200 μ g L− 1 for Pb). The sensitivity of the 25-μ m electrode varied for different analytes from 0.23 (&plusmn ; ; 0.5%, Mn) to 4.83 (&plusmn ; ; 0.9%, Pb) nA L μ mol− 1, and sensitivity of the 125-μ m electrode varied from 1.48 (&plusmn ; ; 0.7%, Zn) to 58.53 (&plusmn ; ; 1.1%, Pb nA L μ mol− 1. These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the De&ucirc ; ; le River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments

International audience; Microelectrodes of silver–copper alloys have been evaluated for use in voltammetric analyses. Increased overpotential towards the hydrogen overvoltage reaction (HER) was found as a function of increased copper content in the silver. A study of oxidizing products by cyclic voltammetry (CV) in NaOH solution showed ten anodic and eight cathodic peaks which are described in the present paper. The behaviour of these alloy electrodes is some-where between pure silver and pure copper electrodes. Differential pulse anodic stripping voltammetry (DPASV) was used to measure zinc, cadmium and lead in ultrapure water only (18 MΩcm), and good linearity was found for all metals (r 2 =0.998) in the range of 0.5 to 5 ppb with a 600-to 1,200-s plating time. It was additionally found that cadmium and lead were better separated on the alloy electrodes compared to pure silver electrodes. Measure-ments of nickel were carried out on alloy electrodes by use of adsorptive differential pulse cathodic stripping voltam-metry (Ad-DPCSV), and good linearity (r 2 =1.000) was found in the range from 0.5 to 5 ppb with an adsorption time of 120 s. The alloy electrodes were also found to be sensitive to nitrate, and good linearity (r 2 =0.997) was found in the range from 1 mg L −1 to 100 mg L −1 using differential pulse voltammetry (DPV) scanning from −450 mV to −1,500 mV. Addition of nitrate in ultrapure water afforded two different peaks related to the successive reductions of nitrate and nitrite. In ammonium buffer solution (pH 8.6) only one peak resulting from reduction of nitrate was observed. Furthermore, the use of alloy electrodes containing 17% Cu was tested in real samples, by installing it in a voltammetric system for monitoring of zinc and lead in a polluted river, the river Deûle, near the town of Douai in northern France. Results were found to be in agreement with parallel measurements carried out by ICP-MS.

The monitoring of dissolved zinc in the Deûle river was undertaken at three different periods of the years 2008 and 2009. Electrolabile concentrations of Zn were estimated every 2 hours for several weeks by using an ATMS (Automatic Trace metal Monitoring System) based on voltammetric measurements using a solid Ag-Hg rotating disc working electrode. Complementary measurements were carried out with DGT (Diffusive Gradient in Thin films) pistons deployed directly in the river for 24 hours. Water samples filtrated at 0.45 μm were also analysed by HR-ICP-MS to estimate the total dissolved concentrations of zinc and other trace metals. High frequency monitoring of zinc over several weeks in the Deûle river indicated that the concentration could change significantly over short time periods. Resuspension of polluted sediment and biological activities are two main factors that control the behaviour of zinc in the Deûle river. Furthermore, in May 2009, daily cycles of the electrolabile zinc fraction have been observed at relatively constant total dissolved concentration. It is assumed that this particular behaviour of zinc is based on an exchange between colloids and/or nonelectrolabile forms and free cation and inorganic complexes at a daily time scale.

Studier indikerer at klima endringer og høyere temperaturer stimulerer transporten, oppdelingen og volatiliteten til polyklorerte bifenyler (PCBer). PCBer er vedvarende organiske forurensninger, som er giftige for miljøet. Det blir frigjort i miljøet, gjennom gammel elektrisk utstyr, maling og andre menneskeskapte kilder, og vil bli transportert via luften, havet og bioakkumulering i levende organismer. Long-range atmospheric transportation (LRAT) er hovedtransporteringsmetoden og den raskeste transporteringen, og er stimulert av økning i temperatur fra klimaendringene. LRAT er også påvirket av værsystemene og høyere vindhastigheter. Økningen i havtemperaturen og PCB eksponering, påvirker næringsnettet og opptaket av PCBer innenfor bioakkumuleringen. Økning i temperatur øker også mengden av den atmosfæriske vanndampen, som produserer mer OH radikaler. OH radikalene reagerer med PCBer og er hovedgrunnen til stoffets degradering i atmosfæren. En mulig økning av den totale mengden PCB i sirkulasjon i miljøet, vil også lede an til flere reaksjoner med ozon, som potensielt kan føre til skade på ozonlaget. Studies indicate that climate change and higher temperature stimulates the transportation, partitioning and volatility of polychlorinated biphenyls (PCBs). PCBs are a persistent organic pollutant, which is toxic for the environment. It gets released into the environment, through old electrical equipment, paint and other anthropogenic sources, and will then be transported via the air, ocean or bioaccumulation through living organisms. Long-range atmospheric transportation (LRAT) is the main source of transport and the fastest, and is stimulated by the increase in temperature due to the climate change. The LRAT is also affected by the weather systems and higher wind speeds. The increase in ocean temperature and PCB exposure, affects the food web and uptake of PCBs in bioaccumulation. Increase in temperature also increases the atmospheric water vapor, which produces more OH radicals. The OH radicals react with the PCBs, and are the main source to its degradation in the atmosphere. A possible increase in the total amount of PCBs in circulation in the environment, will also lead to more reactions with ozone, which could potentially damage the ozone layer.