Constant M. G. van den Berg

• PhD
• Professor at University of Liverpool

We determined the concentration of iron- and copper-binding humic substances (Fe-HS and Cu-HS) in estuarine waters along with the concentrations of iron- and copper-complexing ligands (LFe and LCu). Suwannee River humic acid (SRHA) was used as a humic standard. The complex stability of Fe with salicylaldoxime (SA) was calibrated for salinities betw...

Copper-binding humic substances (Cu–HS) in seawater were determined using a novel method based on cathodic stripping voltammetry (CSV). Cu–HS adsorb on the mercury (Hg) surface and are quantified on the basis of the reduction current for complexed Cu. Humic acid reference material (Suwannee River humic acid, HA) was used to calibrate the voltammetr...

The chemical speciation of iron in seawater is typically determined by cathodic stripping voltammetry (CSV) making use of ligand competition between an electroactive ligand added to obtain the CSV signal and the natural ligand to determine the complex stability of the natural species. Different procedures differ in the added ligand that is selected...

A new method, based on the direct detection of iron-humic substance (HS) species by cathodic stripping voltammetry (CSV), is used to determine the iron binding capacity and complex stability of fulvic acid (FA), humic acid (HA), and the natural HS in the seawater. The FA binds 16.7 ± 2.0 nmol iron (Fe) (mg FA)-1, whereas the HA and the marine HS bi...

Copper (Cu) in seawater can be determined by anodic stripping voltammetry using a vibrating gold microwire electrode (VGME) with a much lower limit of detection than using a mercury electrode, enabling detection of labile Cu at trace level. The possibility of pseudopolarography of Cu using the VGME is investigated here and is calibrated against kno...

The solubility of iron (Fe) in seawater is greatly enhanced by complexation with organic ligands, predominantly occurring as humic substances (HS) in coastal areas. Mining exploitation is believed to change the natural biogeochemical cycle of Fe in coastal waters, even though its impacts on the physical and chemical speciation of the Fe fractions a...

In situ effects of ocean acidification are increasingly studied at submarine CO2 vents. Here we present a preliminary investigation into the water chemistry and biology of cool temperate CO2 vents near Whakaari–White Island, New Zealand. Water samples were collected inside three vent shafts, within vents at a distance of 2 m from the shaft and at c...

Copper distribution and speciation were determined at stations P4 and P26 along Line P as part of a GEOTRACES Process Study in the Northeast Pacific, at depths between 10 and 1400 m. Two ligand classes (L1 and L2) were detected at both stations: the stronger L1 ligand pool with log K'Cu2+L1 15.0–16.5 and the weaker L2 ligand pool with log K'Cu2+L2...

The concentrations of dissolved copper (Cud), copper-binding ligands, thiourea-type thiols, and humic substances (HSCu) were measured in estuarine waters adjacent to Sapelo Island, Georgia, USA, on a monthly basis from April to December 2014. Here we present the seasonal cycle of copper speciation within the estuary and compare it to the developmen...

Iodide in natural waters is an important nutrient to aquatic organisms and its determination is of relevance to marine aquaculture. For this reason it is of interest to have a simple analytical method for determination of iodide in water samples. Iodide in seawater can be determined electrochemically by cathodic stripping voltammetry (CSV) with a m...

We investigated biogeochemical cycling of dissolved copper (dCu) along the Line P transect, spanning from the coastal waters of British Columbia, Canada, to the High Nutrient, Low Chlorophyll (HNLC) open Ocean Station Papa (OSP or P26), in the subarctic Northeast Pacific. DCu concentrations ranged from 1.4–3.7 nmol kg− 1 throughout the water column...

Iron-binding ligands are paramount to understanding iron biogeochemistry and its potential to set the productivity and the magnitude of the biological pump in >30% of the ocean. However, the nature of these ligands is largely uncharacterized and little is known about their sources, sensitivity to photochemistry and biological transformation, or sca...

We elaborate the need for a quality-controlled chemical speciation model for seawater and related natural waters, work which forms the major focus of SCOR Working Group 145. Model development is based on Pitzer equations for the seawater electrolyte and trace components. These equations can be used to calculate activities of dissolved ions and mole...

Here we use cathodic stripping voltammetry with competitive ligand exchange (CLE-CSV) to determine the speciation of Fe in samples from the Mersey River estuary and Liverpool Bay in the presence of salicylaldoxime (SA). Multiple analytical windows (MAWs) were obtained by varying the concentration of SA. Data fittings from individual titrations were...

We determined the concentration of iron- and copper-binding humic substances (Fe-HS and Cu-HS) in estuarine waters along with the concentrations of iron- and copper-complexing ligands (LFe and LCu). Suwannee River humic acid (SRHA) was used as a humic standard. The complex stability of Fe with salicylaldoxime (SA) was calibrated for salinities betw...

Environmental context Identifying the source and stimuli responsible for organic ligands in seawater is crucial to understanding trace metal availability. Voltammetric techniques were employed to characterise the water chemistry of seaweed cultures exposed to low levels of Cu or Zn over 7 days. The results suggest that seaweeds are a potential sour...

A novel electrode based on a vibrating silver amalgam microwire was used for pseudopolarography of lead (Pb) in seawater. Pseudopolarography is a method to study the stability of metal species by examination of their reduction potential. The reduction potential of kinetically irreversible species is related to the thermo- dynamic complex stability...

Silver amalgamated electrodes are a good substrate to determine lead (Pb) and cadmium (Cd) in seawater because they have properties similar to mercury but without the free mercury (Hg). Here a silver amalgamated microwire (SAM) electrode is optimised for the determination of Pb and Cd in coastal waters and uncontaminated ocean waters. The SAM was v...

Chromium (Cr(VI)) in water can be determined by adsorptive catalytic cathodic stripping voltammetry in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate on the hanging mercury drop electrode (HMDE). Predominately Cr(VI) is detected and the water is UV-digested to convert all Cr to Cr(VI) prior to analysis. We develop here an alt...

Carbon, gold and silver microwires are revisited under vibrated conditions for detection of trace lead and cadmium in seawater. The Pb and Cd peaks fully overlapped on the bare gold and carbon electrodes and partially on the silver electrode. The sensitivity of all three was insufficient for detection in uncontaminated waters. Peak separation was o...

The chemical speciation of iron was determined in the Southern Ocean along a transect from 48 to 70°S at 20°E. Dissolved iron concentrations were low at 0.1–0.6 nM, with average concentrations of 0.25±0.13 nM. Organic iron complexing ligands were found to occur in excess of the dissolved iron concentration at 0.72±0.23 nM (equivalent to an excess o...

The oxidation potentials of As(0)/As(III) and Sb(0)/Sb(III) on the gold electrode are very close to each other due to their similar chemistry. Arsenic concentration in seawater is low (10-20nM), Sb occurring at ∼0.1 time that of As. Methods are shown here for the electroanalytical speciation of inorganic arsenic and inorganic antimony in seawater u...

Whilst there is increasing evidence for the presence of stabilized Fe(II) associated with organic matter in aquatic environments, the absence of a reliable method for determining Fe(II) speciation in solution has inhibited the study of this aspect of Fe biogeochemistry. A technique is described here for the determination of Fe(II) organic complexat...

Apparatus is designed and tested to determine metals in situ in seawater. Voltammetry with a vibrating gold microwire electrode (VGME) is combined with a battery powered potentiostat and a processor board and is tested for in situ monitoring of copper (Cu) in coastal waters. The VGME was combined with solid state reference and counter electrodes to...

The potential release of metals from anoxic sediments exposed to oxygen was investigated by using a synthetic preparation of metal sulphides dominated by solid phase FeS. The technique of DGT (diffusive gradients in thin-films) was used to measure sulphide and Fe, Mn and Ni in the anoxic metal-sulphide slurry, which had a pH of 6.4. Speciation calc...

Direct electrochemical determination of arsenate (As(V)) in neutral pH waters is considered impossible due to electro-inactivity of As(V). As(III) on the other hand is readily plated as As(0) on a gold electrode and quantified by anodic stripping voltammetry (ASV). We found that the reduction of As(V) to As(III) was mediated by elemental Mn on the...

Chromium (Cr VI) in water can be determined by adsorptive catalytic cathodic stripping voltammetry in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate on the hanging mercury drop electrode (HMDE). Predominately Cr VI is detected and the water is UV-digested to convert all Cr to Cr VI prior to analysis. We develop here an altern...

Humic substances (HS), the main hydrophobic component of dissolved organic matter, are present in all natural waters and are known to interact strongly with trace metals by complexation and co-precipitation. Traditionally, the role assigned to HS in iron cycling was as scavengers via flocculation in brackish waters. Their iron binding properties ha...

In this work, a simple, rapid, reliable and low cost method for simultaneous electrochemical determination of As, Cu, Hg and Pb ions, on a vibrating gold microwire electrode combined with stripping voltammetry, is described for the first time. The multi-element detection was performed in the presence of oxygen by differential pulse anodic stripping...

Stripping voltammetry is limited in acidic conditions to relatively high deposition potentials because of the interfering effects of the hydrogen produced at the working electrode. We report here a simple procedure to perform reliable and sensitive trace metal analysis in such conditions. Measurements are made at a gold microwire electrode. After a...

Environmental context Metals in the marine environment play a role in biological processes but can also be toxic. An electrochemical method with a simple microwire electrode is presented that facilitates detection of zinc and manganese in coastal waters. The method is very sensitive and will likely lead to the development of an in-situ monitoring a...

A solid, bismuth (Bi), disk, electrode is used to determine lead (Pb) in natural waters including seawater. The diffusion layer thickness was lowered from 93 to 29 µm by stirring, and to 18 µm by using the vibrated version of the Bi electrode. The Bi electrode does not require removal of dissolved oxygen, which facilitates in situ detection. The el...

Contamination of groundwater with arsenic (As) is a major health risk through contamination of drinking and irrigation water supplies. In geochemically reducing conditions As is mostly present as As(III), its most toxic species. Various methods exist to determine As in water but these are not suitable for monitoring arsenic speciation at its origin...

We determined the complex stability of copper, zinc, cobalt and aluminum with humic acid (HA) and fulvic acid (FA) in pH 8 seawater. The method is based on metal competition against iron, for which the complex stability with humic substances (HS) in seawater had been calibrated previously against EDTA. The conditional stability constants, log K'(Mn...

Recent developments and results in the field of remote monitoring of trace metals in polluted river water are reviewed in combination with previous reported research in this field. Some years ago an automatic trace metal system (ATMS) using different modes of voltammetry in combination with innovative solid alloy electrodes was invented. The ATMS d...

The chemical speciation of copper in the estuarine waters of the Vigo Ria was determined by titrations with salicylaldoxime (reverse copper titrations) and with copper (forward titrations). The forward titrations quantified the concentrations of ligands present in excess whereas the reverse titrations demonstrated the presence of low concentrations...

Benthic fluxes of copper, copper complexing ligands and thiol compounds in the shallow waters of Venice Lagoon (Italy) were determined using benthic chambers and compared to porewater concentrations to confirm their origin. Benthic copper fluxes were small due to small concentration differences between the porewaters and the overlying water, and th...

The speciation trend of dissolved copper (DCu) was studied for the first time in a Galician Ria across the estuarine zone of the Vigo Ria during the wet season and related to the copper levels in suspended particulate matter (PCu) and sediments. In the riverine and ocean end-members DCu concentrations can be defined as pristine (<4 nM in Oitaven Ri...

Continental inputs of copper via rivers and sewage into the Vigo Ria were evaluated. The main fluvial input is not contaminated and the most degraded discharges occur on the southern margin of the middle ria. Continental inputs of copper and ligands to the ria are dominated by sewage treatment plants (136 mol Cu day(-1), 124 mol L day(-1)) supporte...

IntroductionAnalysis by atomic absorption spectrometryAnalysis by electrochemical methodsAnalysis by total-reflection X-ray fluorescence spectrometry (TXRF)Analysis by spectrophotometryAnalysis of marine particles

Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced u...

A new voltammetric method is presented for the measurement of humic substances (HS) in natural waters. The method is based on catalytic cathodic stripping voltammetry (CSV) and makes use of adsorptive properties of iron-HS complexes on the mercury drop electrode at natural pH. A fulvic acid standard (IHSS) was used to confirm the voltammetric respo...

This work proposes a vibrating microwire electrode as working electrode in stripping voltammetry. The vibration was found to maintain a constant and thin (1–2 μm) diffusion layer during the deposition step. The electrode vibration eliminated the need for external stirring of the solution, thus facilitating in situ detection in the environment. The...

Chemiluminescence measurements of the photochemical reduction of iron in cold, high-latitude waters (79 degrees N) show that a significant fraction (20%) of the dissolved iron is reduced when exposed to sunlight. The reduction is immediately initiated and the transition to a steady-state concentration of approximately 200 pM photochemical Fe(II) is...

In nearly a dozen open-ocean fertilization experiments conducted by more than 100 researchers from nearly 20 countries, adding iron at the sea surface has led to distinct increases in photosynthesis rates and biomass. These experiments confirmed the hypothesis proposed by the late John Martin that dissolved iron concentration is a key variable that...

The determination of arsenic in sea and freshwater by anodic stripping voltammetry (ASV) was revisited because of problems related to unstable peaks and inconveniently strong acidic conditions used by existing methods. Contrary to previous work it was found, that As(III) can be determined by ASV using a gold microwire electrode at any pH including...

The possible photolysis of organic copper complexing ligands in marine waters is investigated here by irradiation of estuarine waters with natural sunlight and with the simulated UV component of sunlight at wavelengths of 300-350 nm, typical for intermediate latitudes, in an incubator. Copper complexing ligands and thiol compounds were determined b...

A procedure is presented by which mercury and copper are determined simultaneously in seawater and dilute acid (0.01 M HCl) by anodic stripping voltammetry using gold microwire electrodes. It was found that anion (halide) adsorption is the cause for a gradual decrease in the height and potential of the mercury peak. The effect is eliminated by incl...

A mercury coated, gold, micro-wire electrode is used here for the determination of iron in seawater by catalytic cathodic stripping voltammetry (CSV) with a limit of detection of 0.1 nM Fe at a 60s adsorption time. It was found that the electrode surface is stable for extended periods of analyses (at least five days) and that it is reactivated by b...

Solid phase and pore water chemical data collected in a sediment of the Haringvliet Lake are interpreted using a multi-component reactive transport model. This freshwater lake, which was formed as the result of a river impoundment along the southwestern coast of the Netherlands, is currently targeted for restoration of estuarine conditions. The mod...

The distribution of dissolved iron and its chemical speciation (organic complexation and redox speciation) were studied in the northeastern Atlantic Ocean along 23°W between 37 and 42°N at depths between 0 and 2000 m, and in the upper-water column (upper 200 m) at two stations further east at 45°N10°W and 40°N17°W in the early spring of 1998. The i...

The insolubility of metal sulphides is believed to limit the bioavailability of trace metals in sulphidic sediments. However, if non-equilibrium conditions are important, metals may be more available than simple thermodynamic calculations suggest. To investigate the possible dynamic supply of Cu, Ni and Zn in a sulphidic freshwater sediment, they w...

The chemical speciation of iron in seawater is determined by cathodic stripping voltammetry using 2,3-dihydroxynaphthalene (DHN) as adsorptive and competing ligand. The optimized conditions include a DHN concentration of 0.5-1 microM, seawater at its original pH of 8, and equilibration overnight. The alpha-coefficient for DHN (=[FeDHN]/[Fe']) was c...

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; t...

We determined the chemical speciation of lead and copper in remote mountain and high-latitude lakes at different times of the year, providing background data for regions in Europe least affected by anthropogenic effects. The lakes are characterized by low ionic strength, clear waters, and oligotrophic conditions; are fed predominantly by atmospheri...

A 2-mL microbenthic chamber was fitted with a microelectrode for the in-situ determination of benthic fluxes of S(-II), I-, O2, Mn(II), and Fe(I). Detection was by voltammetry using a battery operated potentiostat and a gold microelectrode. The chamber was fitted on a Perspex plate to be placed on sediments. Because of the small chamber volume, ben...

The voltammetric determination of trace metals in seawater suffers from the interference of dissolved oxygen and engine vibrations onboard ship. It is here attempted to overcome these interferences using a high-frequency (1 to 20 kHz) staircase modulation during the voltammetric scan (high-performance adsorptive cathodic stripping voltammetry, HPAC...

This article describes the determination of Eu by adsorptive cathodic stripping voltammetry after complexation with N-nitroso-N-phenylhydroxylamine (cupferron). The accumulation of the complex at the HMDE was performed at 0.0 V and the subsequent potential scan was made in the square wave mode. The analyte signal occurred at −0.88 V. The detection...

A sensitive procedure to determine trace levels of iron in, seawater is proposed which utilizes adsorptive deposition of the complex of Fe(III) with 1-nitroso-2-naphthol (1-N-2-N) on the mercury drop electrode. Optimized conditions include a solution concentration of 20 μM 1-N-2-N and a pH of 6.9; an adsorption potential of −0.25 V is applied, and...

The sensitivity of the determination of iron in natural waters, including seawater, using cathodic stripping voltammetry (CSV) with adsorptive collection of complexes with 1-nitroso-2-naphthol is greatly enhanced by catalytic reoxidation in the presence of hydrogen peroxide. The limit of detection is lowered to 0.16 nM Fe (using an adsorption time...

A new method is proposed to determine metal speciation by varying the concentration of a competing ligand at a constant metal concentration, with detection by cathodic stripping voltammetry. The free metal ion concentration is gradually lowered from its natural level while the method probes progressively deeper into the already complexed metal frac...

It is demonstrated here that it is possible to determine mercury in chloride containing media like seawater by anodic stripping voltammetry using a modified electrode. A gold microwire electrode is modified using mercaptoacetic acid (MAA) to eliminate the problem of calomel formation, allowing the mercury to become fully removed from the electrode...

There is compelling evidence to demonstrate that phytoplankton in major regions of the world’s oceans are limited by the availability of certain trace elements, notably iron. Cobalt concentrations in open-ocean waters generally range between 10 and 120 pmol L⁻¹ but such levels were not thought to limit phytoplankton growth. Herein, we present data...

Environmental Context. The theoretical basis on which Town and van Leeuwen (Environ. Chem. 2005, 2, 80) dispute current ideas on the speciation of iron in seawater is valid only for the simplified condition of the binding of ionic Fe³⁺ with an ionic organic ligand. The possibilities of different pathways for complex formation and dissociation invol...

Micro-wire electrodes were made from gold and silver wires (diameter: 25 μm; length: 3–21 mm) and sealed in a polyethylene holder; micro-disk electrodes were made from the same wires and polished. The gold electrodes were electrochemically coated with mercury before use; the silver wires were used without coating. Comparative measurements demonstra...

The technique of DGT (Diffusive Gradients in Thin Films) was further developed to allow simultaneous measurement of sulfide and trace metals at the same location in sediment. The new combined DGT probe consisted of a layer of gel impregnated with AgI, overlain by (1) a layer of gel containing Chelex, (2) a layer of gel and (3) a filter membrane. Di...

A method was developed to determine the biocide pyrithione in natural waters. The method is based on cathodic stripping voltammetry (CSV) in the presence of Triton-X-100, which is used to separate the peak from interfering thiol compounds. Optimised conditions include a Triton-X-100 concentration of 4 ppm and a pH adjusted to 9 using ammonia buffer...

The chemical speciation of copper in stream waters from Rutor Glacier was determined by cathodic stripping voltammetry with ligand competition against salicylaldoxime. The complexation of salicylaldoxime was calibrated at various calcium concentrations, the major competing cation in these waters. Copper concentrations (3–7 nM) were approximately te...

This paper discusses the distribution of dissolved Cu and Co in coastal surface waters of the western North Sea. High resolution data (more than 5500 (Cu) and 12000 (Co) data points), obtained using on-line flow-analysis techniques, clearly showed enhanced trace metal levels near the coast and estuarine outflows. In an offshore direction, the high...

The stability of copper complexes with thiol substances in estuarine waters was determined for the first time using a new procedure based on cathodic stripping voltammetry (CSV). The free thiol concentration was monitored during titrations with copper in the presence of a competing ligand salicylaldoxime (SA); concentrations of copper-complexing li...

A transect across the eastern North Atlantic from 42°N, 23°W towards the European continental shelf and English Channel shows a gradient of increasing concentrations of dissolved iron (0.7–1.9 nM), iron-binding ligands and iron(II) across the continental rise. Other data, notably aluminium and manganese, indicate that the increases are part of a fr...

Ferro-manganese nodules of the western Baltic Sea reveal enhanced heavy metal concentrations since the end of the 19th century and are therefore potentially useful for retrospective monitoring of the heavy metal pollution history. However, only Zn shows a significant rise, even though Cu is also introduced to the western Baltic Sea by natural and a...

Marine phytoplankton are known to release metal complexing ligands but little is known about the effect of exudates on the biological behaviour of the different microorganisms, including their toxicity and influence on trace metal availability. In this study, cultures of Emiliania huxleyi grown in filtered seawater, enriched with nitrate and phosph...

The concentration of folic acid (FA), an important constituent of the vitamin B group, was determined over a period of 2 years in the water column of a small meromictic saline lake on the eastern Adriatic coast (Rogoznica Lake), as well as in the western part of the northern Adriatic Sea. The FA concentration was over the range of 0.1–13.5 nM in th...

Carbonic anhydrase (CA) is inactive unless associated with zinc, with possible substitution by cobalt. In this work, the complexation of zinc by CA was determined in sea-water using cathodic stripping voltammetry (CSV) with ligand competition. The zinc was found to be released from the CA over a period of 3 h when equilibrated with a competing comp...

A new procedure for the direct determination of picomolar levels of iron in seawater is presented. Cathodic stripping voltammetry (CSV) is preceded by adsorptive accumulation of the iron(III)-2,3-dihydroxynaphthalene (DHN) complex from seawater, containing 20 microM DHN at pH 8.0, onto a static mercury drop electrode, followed by reduction of the a...

Mobilisation of contaminants is an important issue in environmental risk assessment of dredging projects. This study has aimed at identifying the effects of dredging on mobilisation of trace metals (Zn, Cu, Cd and Pb). The intensities and time scales of trace metal mobilisation were investigated during an experimental dredging project conducted und...

A method was developed to determine the extent of cobalt complexation with organic ligands in seawater, and applied to samples from the North Eastern Atlantic Ocean. The cobalt speciation was determined using catalytic cathodic stripping voltammetry with ligand competition against the adsorptive ligand (nioxime). Optimised conditions include a niox...

Thiols were determined in coastal waters of the western North Sea and English Channel. Detection was carried out on-board ship on-line by flow-analysis with detection by cathodic stripping voltammetry and calibration with thiourea. The thiol concentrations ranged from 0.70 to 3.60 nM (thiourea equivalents) and were found to vary over a relatively s...

A procedure is presented to determine lead complexing ligands in lake water by cathodic stripping voltammetry (CSV) with ligand competition using Calcein-blue (CB) (8-[N,N- bis(carboxyl-methyl)aminomethyl]-4-methylumbelliferone). The optimised conditions to determine dissolved lead in lake water by CSV using CB entails a CB concentration of 500 nM,...

The redox speciation of iron was determined by voltammetry in two lakes (Blelham Tarn, a lowland lake, and Gossenköllesee (GKS), a mountain lake). The reactive iron (FeR) concentration was ~40 nM in the epilimnion of Blelham Tarn, and up to 37% of this occurred as iron(II). In contrast, the FeR concentration in GKS was much lower at ~1 nM, similar...

A procedure is described for the determination of selenium in natural waters using cathodic stripping voltammetry in the presence of rhodium. Advantage is taken from a catalytic effect on the electrochemical reduction of protons in the presence of a mixed complex of selenide with rhodium and chloride, containing Cl–Rh–SeH species. The catalysis cau...

The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only with nitrate and phosphate (N and P) without chelating agents to control metal speciation. Growth was slow in a “low-iron” culture containing 1.3 nM iron and was found to be iron-limited, growth-accelerating when a 1-nM iron addition was made. The growth r...

Intense decalcification of fine-grained organic-rich soils subject to periodic oxidation and reduction takes place in the Biesbosch, a freshwater, tidally influenced wetland area in the Rhine–Meuse delta in The Netherlands. Soil chemical (sulphide concentration and pore-water characteristics) and hydrological variables (drainage) were measured in t...

Measurements of zinc and zinc complexation by natural organic ligands in the northeastern part of the Atlantic Ocean were made using cathodic stripping voltammetry with ligand competition. Total zinc concentrations ranged from 0.3 nM in surface waters to 2 nM at 2000 m for open-ocean waters, whilst nearer the English coast, zinc concentrations reac...

Pore-water concentrations of inorganic solutes were measured at four locations in a recent sedimentation area of the river Meuse in The Netherlands. The pore-water concentration profiles were interpreted using the steady state one-dimensional reaction/transport model STEADYSED1. This model explicitly accounts for the organic matter degradation path...

Metals dissolve in water by ionisation, and their solubility is usually restricted by their solubility product with one of the major anions in sea water, such as with hydroxide, carbonate or phosphate. Their solubility is increased by the formation of soluble complexes with the major anions. The concentrations of the vast majority of the metals in...

Cathodic stripping voltammetry (CSV) is subject to interference by engine vibrations when used on-board ship. Scanning wave- forms utilizing high-frequency potential modulations can to some extent overcome this problem, but these cannot be used for catalytic CSV without major loss of sensitivity. To minimize the effects of vibrations an antivibrati...

Marine microalgae (Emiliania huxleyi) were grown in seawater enriched only with nitrogen and phosphorus, without control of free metal concentrations using synthetic chelators. Complexing ligands and thiol compounds were determined by cathodic stripping volt-ammetry. Copper was added to these cultures, and ligands were produced in response to the c...