Ni In Seawater Research Articles

Determination of Cr and Ni in Seawater by High-Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry

Determination of Cr and Ni in Seawater by High-Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry

Improvement of Advanced Sample Preparation Systems for the Determination of Trace Ni in Seawater by Electro-Membranes.

Due to its important environmental role, the analysis of trace metals in natural waters is attracting increasing attention; consequently, faster and more accurate analytical methods are now needed to reach even lower limits of detection. In this work, we propose the use of electro-membrane extraction (EME) to improve analytical methods based on hollow fiber liquid phase micro-extraction (HFLPME). Specifically, an EME-based method for the determination of trace Ni in seawater has been developed, using an HFLPME system with di-2-ethylhexyl phosphoric acid (DEHPA) in kerosene as a chemical carrier, followed by instrumental determination by graphite furnace atomic absorption spectroscopy (GFAAS). Under optimum conditions, Ni was pre-concentrated 180 ± 17 times after 15 min, using sample pH = 5.5, the concentration of DEHPA 0.9 M in the liquid membranes, and 1.9 M HNO3 in the acceptor solution, as well as an electric potential of 25 V with the sample being stirred at 500 rpm. When compared with other HFLPME systems for pre-concentration of trace Ni in seawater in the absence of electric potential, the enrichment factor was improved 2.2 times, while the time of extraction was reduced an 89%. The limit of detection of the new method was 23.3 ng L-1, and both its applicability and accuracy were successfully evaluated by analyzing Ni concentration in a seawater-certified reference material (BCR-403), showing the reliability of EME for sample preparation in the determination of trace metals in marine water samples.

Complexation reduces nickel toxicity to purple sea urchin embryos (Strongylocentrotus purpuratus), a test of biotic ligand principles in seawater

The potential for Ni toxicity in seawater is of concern because of mining and processing activities in coastal regions. Determining Ni speciation is vital to understanding and predicting Ni toxicity and for bioavailability-based nickel risk assessment. The goal of this study was to characterize the complexation of Ni in relation to toxicity using embryological development of purple sea urchin (S. purpuratus). It was predicted that free ion [Ni2+] would be a better predictor of toxicity than total dissolved Ni concentrations (NiD). Synthetic ligands with known logKf values (Ethylenediaminetetraacetic acid (EDTA), Nitrilotriacetic acid (NTA), tryptophan (TRP), glutamic acid (GA), histidine (HD), and citric acid (CA)) were used to test the assumptions of the biotic ligand model (BLM) for Ni in seawater. [NiD] was measured by graphite furnace atomic absorption spectroscopy (GFAAS) and Ni2+ was first quantified using the ion-exchange technique (IET) and then concentrations were measured by GFAAS; [Ni2+] was also estimated using aquatic geochemistry modelling software (Visual Minteq). The mean EC50 values for [NiD] in unmodified artificial seawater control was 3.6 µM (95% CI 3.0–4.5) [211 µg/L 95% CI 176–264] and the addition of ligands provided protection, up to 6.5-fold higher [NiD] EC50 for EDTA. Compared to the control, measured EC50 values based on total dissolved nickel were higher in the presence of ligands. As predicted by BLM theory, [Ni2+] was a better predictor of Ni toxicity with 17% variability in EDTA and CA media while there was 72% variability in the prediction of Ni toxicity with total dissolved Ni. The results of this research provide support for the application of BLM- based prediction models for estimating Ni impacts in seawater.

Active methanogenesis during the melting of Marinoan snowball Earth

Geological evidence indicates that the deglaciation of Marinoan snowball Earth ice age (~635 Myr ago) was associated with intense continental weathering, recovery of primary productivity, transient marine euxinia, and potentially extensive CH4 emission. It is proposed that the deglacial CH4 emissions may have provided positive feedbacks for ice melting and global warming. However, the origin of CH4 remains unclear. Here we report Ni isotopes (δ60Ni) and Yttrium-rare earth element (YREE) compositions of syndepositional pyrites from the upper most Nantuo Formation (equivalent deposits of the Marinoan glaciation), South China. The Nantuo pyrite displays anti-correlations between Ni concentration and δ60Ni, and between Ni concentration and Sm/Yb ratio, suggesting mixing between Ni in seawater and Ni from methanogens. Our study indicates active methanogenesis during the termination of Marinoan snowball Earth. This suggests that methanogenesis was fueled by methyl sulfides produced in sulfidic seawater during the deglacial recovery of marine primary productivity.

Sources of particulate Ni and Cu in the water column of the northern South China Sea: Evidence from elemental and isotope ratios in aerosols and sinking particles

We present isotope ratios of Ni (δ60Ni) and Cu (δ65Cu) in sinking particles, aerosols, and seawater collected from the northern South China Sea to identify sources and transformation processes of the two metals. In aerosols, δ60Ni values are in the range +0.05‰ to +0.56‰, and δ65Cu values are in the range −0.33‰ to +0.83‰. The isotope ratios are different from those of lithogenic materials, indicating that the aerosols are anthropogenic in origin. In sinking particles collected at depths of 2000 and 3500 m, δ60Ni values are in the range +0.01‰ to +0.54‰ at 2000 m and −0.18‰ to +0.54‰ at 3500 m, and the values exhibit similar temporal variation pattern between 2000 and 3500 m. Based on the significant correlation between δ60Ni and the ratio of P/Ni or organic-C/Ni, we hypothesize that the main sources of Ni in the sinking particles originate from both resuspended marine sediments off southwest Taiwan, and biogenic organic particles. The δ60Ni in biogenic particles is estimated to be +0.6‰ to +1.0‰, which is 0.3–0.7‰ lighter than that of dissolved Ni in seawater. The isotope ratios of Cu in sinking particles are fairly constant (+0.13‰ to +0.36‰), and the range is between those of marine sediments and labile fractions of marine particles. Thus, Cu in sinking particles is likely to be from marine sediments and biogenic organic particles. Compared with Ni, the correlation between Cu and P or organic-C is weaker, suggesting that the Cu/P and Cu/organic-C ratios are not constant in organic matter or there are additional sources of particulate Cu, such as Fe-Mn oxides and anthropogenic aerosols.

Trace elements in the seagrass Posidonia oceanica: Compartmentation and relationships with seawater and sediment concentrations

Seagrasses are employed to assess trace element levels in seawater and sediments; however, their capacity as bioindicators of trace elements in seawater has been recently questioned, due to the scarcity of a significant seagrass-seawater relationship. In the aim to provide an insight into trace element accumulation in the seagrass Posidonia oceanica, Cd, Co, Cr, Cu, Ni and Pb concentrations in seawater, sediments, and several seagrass compartments (adult leaf blades, intermediate leaf blades, adult leaf sheaths, juvenile leaves, orthotropic rhizomes, plagiotropic rhizomes, and roots of plagiotropic rhizomes) from the coasts of Thrace, Greece were determined. Uni- and multivariate data analyses were applied. A comparison with reported element concentrations revealed that this coastal area can be generally classified as an area of no marked Cd, Co, Cr, Cu, Ni and Pb anthropogenic enrichment. Trace elements showed a non-uniform distribution among seagrass compartments; adult leaf blades displayed the highest mean Cd and Ni concentrations, adult leaf blades, plagiotropic rhizomes and roots the highest mean Co concentrations, juvenile leaves the highest mean Cu concentration, and plagiotropic rhizomes the highest mean Cr and Pb concentrations, indicating that the accumulation varies with element, compartment and compartment age. Cd, Cr and Ni in adult leaf blades reached mean tissue-seawater accumulation factors of 103, while Co of 104, implying that this seagrass is a strong accumulator of these elements from solution. Cd, Co, Cr, and Ni concentrations in leaf compartments, particularly adult leaf blades, positively correlated with their concentrations in seawater, and Pb concentrations in plagiotropic rhizomes and roots with sediment Pb concentration. Thereby, P. oceanica could be regarded as a biondicator for Cd, Co, Cr and Ni in seawater, and for Pb in sediments. The results presented provide an insight on trace element accumulation in P. oceanica, and can be utilized for the design of biomonitoring programs.

Weathering and vegetation controls on nickel isotope fractionation in surface ultramafic environments (Albania)

The dissolved nickel (Ni) isotopic composition of rivers and oceans presents an apparent paradox. Even though rivers represent a major source of Ni in the oceans, seawater is more enriched in the heavier isotopes than river-water. Additional sources or processes must therefore be invoked to account for the isotopic budget of dissolved Ni in seawater. Weathering of continental rocks is thought to play a major role in determining the magnitude and sign of isotopic fractionation of metals between a rock and the dissolved product. We present a study of Ni isotopes in the rock–soil–plant systems of several ultramafic environments. The results reveal key insights into the magnitude and the control of isotopic fractionation during the weathering of continental ultramafic rocks. This study introduces new constraints on the influence of vegetation during the weathering process, which should be taken into account in interpretations of the variability of Ni isotopes in rivers.The study area is located in a temperate climate zone within the ophiolitic belt area of Albania. The serpentinized peridotites sampled present a narrow range of heavy Ni isotopic compositions (δNi60=0.25±0.16‰, 2SD n=2). At two locations, horizons within two soil profiles affected by different degrees of weathering all presented light isotopic compositions compared to the parent rock (Δ60Nisoil–rock up to −0.63‰). This suggests that the soil pool takes up the light isotopes, while the heavier isotopes remain in the dissolved phase. By combining elemental and mineralogical analyses with the isotope compositions determined for the soils, the extent of fractionation was found to be controlled by the secondary minerals formed in the soil.The types of vegetation growing on ultramafic-derived soils are highly adapted and include both Ni-hyperaccumulating species, which can accumulate several percent per weight of Ni, and non-accumulating species. Whole-plant isotopic compositions were found to be isotopically heavier than the soil (Δ60Niwhole plant-soil up to 0.40‰). Fractions of Ni extracted by DTPA (diethylenetriaminepentaacetic acid) presented isotopically heavy compositions compared to the soil (Δ60NiDTPA-soil up to 0.89‰), supporting the hypothesis that the dissolved Ni fraction controlled by weathering has a heavy isotope signature. The non-hyperaccumulators (n=2) were inclined to take up and translocate light Ni isotopes with a large degree of fractionation (Δ60Nileaves-roots up to −0.60‰). For Ni-hyperaccumulators (n=7), significant isotopic fractionation was observed in the plants in their early growth stages, while no fractionation occurred during later growth stages, when plants are fully loaded with Ni. This suggests that (i) the high-efficiency translocation process involved in hyperaccumulators does not fractionate Ni isotopes, and (ii) the root uptake process mainly controls the isotopic composition of the plant. In ultramafic contexts, vegetation composed of hyperaccumulators can significantly influence isotopic compositions through its remobilization in the upper soil horizon, thereby influencing the isotopic balance of Ni exported to rivers.

Solvent bar micro-extraction: Improving hollow fiber liquid phase micro-extraction applicability in the determination of Ni in seawater samples

During the last decade, hollow fiber liquid phase micro-extraction (HF-LPME) has become an attractive alternative in sample treatment for the analysis of trace metals in seawater. If compared with other similar methodologies, its main advantages are associated to a higher stability of the organic solution contained into the pores of the fiber, which acts as a lipophilic membrane during the extraction process. However there are some remaining problems that makes its use difficult, mostly related to the need of increasing the rate of analysis and improving portability.In this paper a novel three phase solvent bar micro-extraction (3PSBME) for the fiber device has been proposed. Its main advantage is that the 3PSBME device can be left free in the sample. This way the system is portable, and no special support is needed leading to the possibility of simultaneous extraction of several samples.In this work, multivariate central composite design of experiment has been carried out to optimize Ni pre-concentration using di-2-ethylhexyl phosphoric acid (DEHPA) as extractant and HNO3 as acceptor agent. Factors influencing extraction have been the pH in the sample and the fiber length. For seawater samples, Ni can be pre-concentrated 11 times in 140min. The method presents RSD 9.42% and limit of detection 44ngL−1, using GFAAS for instrumental determination. It has been applied for determination of Ni in seawater, including a reference material CRM-403 proving its applicability.

Ni isotope fractionation during sorption to ferrihydrite: Implications for Ni in banded iron formations

A major decline in marine methanogen populations during the Late Archaean Eon has been proposed as a driver for the Great Oxidation Event (GOE) at ~2.4Ga. Konhauser et al. (2009, Nature 458, 750–753) recently hypothesized that a dramatic decrease between 2.7 and 2.4Ga in the concentration of dissolved Ni, an essential nutrient for methanogens, may have been responsible for the decline. To test that hypothesis, Ni stable isotopes, a novel proxy for methanogen Ni limitation, will be applied to the Late Archaean–Paleoproterozoic rock record in the future, possibly through analysis of banded iron formations (BIFs). In order to facilitate interpretation of those data, we investigated the fractionation of Ni stable isotopes during sorption to synthetic ferrihydrite, which was likely the primary precipitating phase during BIF deposition, via bench-top experiments. The observed fractionations for adsorption and coprecipitation experiments were indistinguishable and averaged Δ60/58Nidissolved-sorbed=+0.35±0.10‰ (1 sd; light Ni sorbed). Parallel, linear trends in isotope compositions of dissolved and sorbed Ni as a function of fraction of Ni sorbed indicate an equilibrium isotope effect with rapid and continuous exchange between dissolved and sorbed Ni. Additionally, we observed fractionation of Δ60/58Nidissolved–sorbed=+0.23±0.07‰ (1 sd) in experiments in which ferrihydrite had been aged for up to 30days and had partially transformed to goethite and hematite; thus the fractionations in all of our experiments are the same within uncertainties. Although our simple system differs from Archaean seawater, our results suggest that ferrihydrite precipitating to form BIFs may always have been offset by a constant fractionation from coexisting dissolved Ni in seawater.

Analisis Logam Ni, Mn dan Cr pada Air dan Sedimen di Perairan Pantai Pulau Singkep Kepulauan Riau

Analysis of Ni, Mn and Cr concentrations in seawater and sediment in Singkepisland coastal waters has been conducted in March 2014. All water quality parametersmeasured were still within the tolerable limits for the survival of the aquatic organisms.Samples of sea water and sediment were taken from five stations with three replicates at eachstation. Heavy metals concentrations were analyzed in the Marine Chemistry LaboratoryFaculty of Fisheries and Marine Sciences, University of Riau by using Atomic Absorption3110 Perkin Elmer spectrophotometer. The results showed that the average concentration ofheavy metals in Singkep waters are 0.1820; 0.1084 and 0.4133 μg/L for Ni, Mn and Cr inwater, whilst in sediment are 13.2615, 13.7261 and 81.4578 μg/g for Ni, Mn and Cr. Simplelinear regression analysis indicates positive correlation between Ni in sea water and insediment with y = 10,42 + 22,19x, r = 0,138 and negative correlation with y = 15,09 -13,44xr = 0,226 for Mn and y = 104,8 - 50,76x, r = 0.354 for Cr.

Interrelated influence of light and Ni on Trichodesmium growth

Our previous laboratory study revealed that insufficient Ni supply can limit nitrogen fixation in Trichodesmium, a primary diazotrophic phytoplankton in the tropical and subtropical oceans. Here we show that light intensity and Ni availability interrelate to influence Trichodesmium growth. Trichodesmium growth is severely inhibited under high light (670 μE m–2 s–1) and insufficient Ni condition. On the contrary, the sufficient supply of Ni in seawater can sustain the growth of Trichodesmium under either high or low light conditions. We also observed elevated intracellular Ni uptake in Trichodesmium grown under relatively high light condition, supporting that the Ni requirement is used for removing superoxide generated through photosynthetic electron transport. This study shows that light saturation condition for Trichodesmium growth is Ni concentration dependent. This finding may exhibit implications for interpreting temporal and spatial distributions and activities of Trichodesmium in both modern and ancient oceans when light intensity and Ni concentrations have significantly varied.

KANDUNGAN LOGAM BERAT Pb, Cd, Cu, Zn DAN Ni DALAM AIR LAUT DAN SEDIMEN DI MUARA SUNGAI MEMBRAMO, PAPUA DALAM KAITANNYA DENGAN KEPENTINGAN BUDIDAYA PERIKANAN

Heavy Metals Content Pb, Cd, Cu, Zn And Ni In Sea Water And Sediment In Membramo Estuary And Its Relationship With Fishery Cultivation. Obervation on heavy metals Pb, Cd, Cu, Zn and Ni content in Jakarta Bay were carried out in August 2003. The results showed that the Pb, Cd, Cu, Zn, and Ni content still in line with threshold value stated by for fisheries. By the all, in sea water Zn content is higher compared to the others, while in sediment Ni is higher. This data showed the result show that on waters of Membramo River Zn and Ni waste than others elements. Keywords: Membramo, heavy metals, fisheries.

Development of a Field Preconcentration/Elution Unit for Routine Determination of Dissolved Metal Concentrations by ICP‐OES in Marine Waters: Application for Monitoring of the New Caledonia Lagoon

An iminodiacetate chelating resin was optimised for the rapid determination of Co, Cu, Fe, Mn and Ni in seawater. Using inexpensive, high‐capacity, reusable cartridges allowed high flow rates of up to 25 ml min−1. High preconcentration factors, of up to 500, were obtained in order to analyse samples using an ICP‐OES. The requirement for a buffer was eliminated due to the high tolerance of the ICP‐OES to interfering matrix elements, thereby further reducing the potential for contamination. Quantification limits in seawater were: Co = 6 ng l−1, Cu = 8 ng l−1, Fe = 6 ng l−1, Mn = 5 ng l−1 and Ni = 6 ng l−1. The method was verified by the analysis of near shore seawater (CASS‐4) and open ocean seawater (NASS‐5) reference materials. In order to satisfy the high sampling demands using the iminodiacetate cartridges, a portable off‐line preconcentration unit was developed for routine analysis. The multi‐channel preconcentration unit, was capable of treating up to eight samples simultaneously with concentrating times as little as 30 minutes. The technique was also used to determine dissolved metals in fresh and interstitial waters. The technique has been successfully used in a number of environmental studies and impact assessments to evaluate the effects of mining on the New Caledonian lagoon.

Crystal-chemistry of Ni in marine ferromanganese crusts and nodules

Marine ferromanganese crusts and nodules are highly enriched in transition metals such as Ni and Co, yet the crystal chemistry and mode of incorporation of these metals is poorly known. We characterized the crystal chemistry of Ni in two hydrogenetic Pacific ocean ferromanganese crust samples and a hydrogenetic nodule from the Madeira abyssal plain. Energy dispersive spectrometry shows that Ni is associated with the manganese oxide phases, in agreement with previous work. X-ray diffraction patterns show that the dominant Mn3+/4+ oxide is a phyllomanganate similar to hexagonal birnessite or δ-MnO2. Extended X-ray absorption fine-structure spectroscopy shows that the coordination environment of Ni results from structural incorporation into the phyllomanganate phase by replacement of Mn3+/4+. In contrast, Ni initially sorbs to freshly prepared synthetic birnessite by surface complexation over vacancy sites in the MnO2 layer. We propose that the transformation of Ni sorption from surface complexation to structural incorporation provides a potentially irreversible sink for Ni in seawater.

Sorption of Ni by birnessite: Equilibrium controls on Ni in seawater

Synthetic hexagonal birnessite (Hx-birnessite) is a close analogue to natural poorly crystalline phyllomanganate phases found in soils and marine ferromanganese deposits. These phases are often highly enriched in trace metals such as Ni and Co. We measured the sorption of Ni(II) onto synthetic hexagonal birnessite (Hx-birnessite) from pH 1 to 7. EXAFS spectra show that, at pH 3.7, Ni is adsorbed to the Hx-birnessite surface above vacancy sites on {001} as a tridentate corner-sharing complex. We developed a surface complexation model for Ni adsorption based on the equilibria 3(≡Mn 2O − 2/3 ) + Ni + 2 = (≡Mn 2O) 3Ni 0 3(≡Mn 2O − 2/3 ) + Ni + 2 + H 2O = (≡Mn 2O) 3Ni(OH) − + H + Using this surface complexation model, we predict the concentration of Ni in seawater in equilibrium with Ni-bearing birnessite found in hydrogenetic FeMn crusts and nodules. Our predicted results are in good agreement with observed Ni concentrations in seawater and suggest that the concentration of dissolved Ni in seawater is buffered by sorption to birnessite or a related MnO 2 phase. However, in addition to the surface complex, Ni also sorbs by structural incorporation into the vacancy site. In our synthetic samples at pH 7, EXAFS shows ∼ 10% of Ni is structurally incorporated into Hx-birnessite. In natural birnessites found in marine ferromanganese crusts and nodules, EXAFS shows that all of the sorbed Ni is structurally incorporated. Structural incorporation suggests that Ni sorption may be irreversible.

Application of iminodiacetate chelating resin muromac A-1 in on-line preconcentration and inductively coupled plasma optical emission spectroscopy determination of trace elements in natural waters

On-line system incorporating a microcolumn of Muromac A-1 resin was used for the developing of method for preconcentration of trace elements followed by inductively coupled plasma (ICP) atomic emission spectrometry determination. A chelating type ion exchange resin has been characterized regarding the sorption and subsequent elution of 24 elements, aiming to their preconcentration from water samples of different origins. The effect of column conditioning, pH and flow rate during the preconcentration step, and the nature of the acid medium employed for desorption of the retained elements were investigated. A sample (pH 5) is pumped through the column at 3 ml min −1 and sequentially eluted directly to the ICP with 3 M HNO 3/HCl mixtures. In order to remove residual matrix elements from the column after sample loading a short buffer wash was found to be necessary. The effectiveness of the matrix separation process was illustrated. The procedure was validated by analyzing several simple matrices, Standard River water sample as well as artificial seawater. Proposed method can be applied for simultaneous determination of In, Tl, Ti, Y, Cd, Co, Cu and Ni in seawater and for multielement trace analysis of river water. Recovery at 1 μg l −1 level for the determination of investigated 24 elements in pure water ranged from 93.1 to 96% except for Pd (82.2%) and Pb (88.1%). For the same concentration level for seawater analysis recovery was between 81.9 and 95.6% except for Hg (38.2%).

Evaluation of the impacts of land-based contaminants on the benthic faunas of Jakarta Bay, Indonesia

To evaluate the impact of land-based contaminants on benthic faunas, as part of the Land-Ocean Contamination Study (LOCS), a study transect was established in Jakarta Bay, Indonesia during the 1996 southeasterly monsoon. The transect extended 72 km between the city's main port, Tanjung Priok, and the Pilau Seribu Island chain in the Java Sea. The dissolved concentrations of Pb, Cu, Zn, Cr and Ni in seawater, in suspended particulate matter (SPM) and surficial sea bed sediments were measured along the transect at nine sites. In addition, metal concentrations were measured in tissues of the corals Goniopora lobata and Lobophyllia hemprichii at five sites, and of the green mussel, Perna viridis at six sites. An assessment of the impact of contaminants on the faunas was made using a biomarker approach, employing coral community analysis and lysosomal stability with Perna viridis. The results of the study showed two main trends. The distributions of metals dissolved in seawater, in SPM, and in the coral and mussel tissues were similar, and failed to show a consistent graded response from inshore to offshore sites. This suggests that the concentration of metals in waters is the primary route for metal uptake by the coral and mussel tissues. By way of contrast, a clear offshore increase in coral generic diversity, coral cover, coral colony numbers and neutral-red retention time (lysosomal stability) was observed, suggesting increasing nearshore stress. Whilst the coral community stucture may reflect the seasonally-averaged metal distributions in the bay (shown by the metal content of sea bed sediments which increase shorewards), it is more likely that the coral community structure and lysosomal biomarker are responding principally to other nearshore stresses, such as sediment and nutrient loading of water (sewage) or, more likely, organic contaminants such as oils and other hydrocarbons.

Determination of ultra-trace amounts of cadmium, cobalt and nickel in sea-water by electrothermal atomic absorption spectrometry with on-line preconcentration

A miniature column packed with Muromac A-1 chelating resin and a laboratory-built automatic on-line preconcentration system for electrothermal atomic absorption spectrometry were used to determine Cd, Co and Ni in sea-water. The preconcentration system was modified from a Perkin-Elmer AS-40 autosampler by mounting a Muromac A-1 microcolumn near the tip of the autosampler capillary, and we replaced the pull-and-push pump of the autosampler with a peristaltic pump. Retention of the metal ions as a complex on the microcolumn was achieved by using Muromac A-1 as the chelating resin; 20% HNO3 was then used for elution. The procedures of preconcentration were performed by using a four-way distribution valve and a programmable controller. Detection limits (and sample volumes) were 1.2 × 10–4 µg l–1 for Cd (400 µl), 0.007 µg l–1 for Co (1800 µl) and 0.033 µg l–1 for Ni (800 µl). Relative standard deviations for the determination of Cd, Co and Ni in sea-water (CASS-3) were 2.9, 5.6 and 4.1%, respectively. The accuracy of the method was confirmed by the analysis of certified reference saline waters (NASS-4, CASS-3 and SLEW-1).

Dissolved and particulate trace metals in a Scottish sea loch: an example of a pristine environment?

In the near pristine environment of a silled fjord on the west coast of Scotland samples were taken for the determination of dissolved and particulate trace metals (Fe, Mn, Cu, Ni, Cd, Zn and Pb), together with nutrient and hydrographic data, during 19 surveys carried out over a year. An indication of the pristine nature of the environment are the low concentrations of dissolved silicon, phosphate and nitrate which are considerably lower than those of coastal waters which are subject to larger anthropogenic burdens. Distributions of dissolved Cu, Ni and Cd were found to broadly reflect conservative mixing of freshwater and seawater with both end members having similar concentrations. The concentration of dissolved Cu and Ni in seawater entering upper Loch Linnhe (Cu 0.28 μg l −1; Ni 0.26 μg l −1) was consistent with the 1:1 conservative mix of Irish Sea water and North Atlantic surface water predicted from radio-caesium tracer experiments (Mackay & Baxter, 1985). Atmospheric input of trace metals to upper Loch Linnhe appeared to be a relatively minor term in the mass balance relative to fluvial inputs. Values of distribution coefficients Kd were similar to those previously reported for the coastal environment. Iron showed the strongest affinity for the suspended sediments; with particulate percentages of the total load usually greater than 80%. Lead and Mn showed a similar strong affinity to the particle phase. For Cu, Ni and Zn the mass of the element in the dissolved phase was generally greater than that in the particulate fraction. Cadmium, was least associated with the particles, with typically greater than 90% existing in the dissolved phase.

Evaluation of an Osmonics® spiral-wound cross-flow filtration system for sub-μm sampling of Cd, Cu and Ni in seawater

Abstract A 1-kDa (1 kDa = 1000 daltons) Osmonics spiral-wound cross-flow filtration (CFF) membrane has been evaluated for sampling Cd, Cu and Ni in 1-kDa fractions of prefiltered seawater. Size-fractionated samples were collected as part of a CFF intercomparison experiment (Buesseler et al., 1996-this issue) and in the Gulf of Maine. Mass-balance results averaged 93 ± 6% (Cd), 81 ± 19% (Cu), and 99 ± 18% (Ni) for the intercomparison experiment and 56 ± 17% (Cd), 119 ± 38% (Cu), and 91 ± 6% (Ni) for the Gulf of Maine samples. Differences in mass balance between these studies may be related, in part, to removal of sub-μm particles and associated trace metals during prefiltration. An Amicon CFF system showed higher (2–12 ×) colloidal concentrations for Cu and Ni compared to Filtron and Osmonics systems; all CFF systems showed similar Cd, Cu and Ni mass-balance results. A model based on particle impaction with a filter shows the potential for adsorption of sub-μm particles by a 1-kDa Osmonics CFF membrane and conventional (Nuclepore) filters.