Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “speciation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed2003

Validating riverine transport and speciation models using nuclear reactor-derived radiocobalt.

Risk assessment of intentional or accidental discharges of toxic substances into river systems requires combined hydraulic and chemical modeling. Periodic discharges of known volumes with low radioactivity by the Beznau nuclear reactor (Switzerland) serve as validation tracers for both river flow and chemical speciation simulation. Validation of the former has been achieved by comparison of modeled and measured arrival times of radiocobalt along a 65 km transect with a maximum reaction period of 24 hours. Modeled breakthrough curves coincide well with measurements collected during three field campaigns, in spite of the fact that sorption and sedimentation processes were not activated during simulation. This gives indirect evidence of inefficient cobalt sorption. Particle/solution distribution measurements carried out during breakthrough allow further validation of our speciation approach, which is based on Tableau setup of inorganic reactions combined with sorption and organic complexation. Modeled and measured speciation results confirm recent observations of enhanced complexation of cobalt with dissolved organic substances, which significantly reduces particle sorption. The large variability of conditional stability constants for sorption and complexation reactions, for sorption site densities, and for organic ligand concentrations explains the variability of published particle-solution distribution coefficients.

Cobalt Radioisotopes↗
PubMed2003

Electrodialytic removal of heavy metals from different fly ashes. Influence of heavy metal speciation in the ashes.

Electrodialytic remediation, an electrochemically assisted extraction method, has recently been suggested as a potential method for removal of heavy metals from fly ashes. In this work, electrodialytic remediation of three different fly ashes, i.e. two municipal solid waste incinerator (MSWI) fly ashes and one wood combustion fly ash was studied in lab scale, and the results were discussed in relation to the expected heavy metal speciation in the ashes. The pH-dependent desorption characteristics for Cr differed between the two MSWI ashes but were similar for Cd, Pb, Zn and Cu. Thus, it was expected that the speciation of Cd, Pb, Zn and Cu was similar in the two ashes. However, in succeeding electrodialytic remediation experiments significant differences in removal efficiencies were observed, especially for Pb and Zn. In analogous electrodialytic remediation experiments, 8% Pb and 73% Zn was removed from one of the MSWI ashes, but only 2.5% Pb and 24% Zn from the other. These differences are probably due to variations in pH and heavy metal speciation between the different ashes. Cd, the sole heavy metal of environmental concern in the wood ash, was found more tightly bonded in this ash than in the two MSWI ashes. Approximately 70% Cd was removed from both types of ashes during 3 weeks of electrodialytic remediation, although the total concentration was a factor of 10 lower in the wood ash. It was suggested that complex Cd-silicates are likely phases in the wood ash whereas more soluble, condensed phases are dominating in the MSWI ashes.

Electrochemistry↗
PubMed2001

Speciation of platinum compounds: a review of recent applications in studies of platinum anticancer drugs.

This is a review of investigations involving speciation studies of five important platinum-containing drugs used in cancer treatments. The information presented here is drawn from recent reports published during the period 1995-1999. The work includes detection, separations and identifications of degradation and biotransformation products. In addition, important information is reported on the number and nature of products of reactions of platinum anticancer drugs with thiol compounds. HPLC is employed effectively for separations of reaction products in speciation investigations. Information derived from speciation is very helpful in studies of pharmacokinetics as well as side effects and toxicities of the drugs as they are administered to patients.

Antineoplastic Agents↗
PubMed2003

Sympatric speciation in parasites--what is sympatry?

Parasites account for a large part of known species diversity and are considered to have a high potential for sympatric speciation. However, the frequency of sympatric divergence in these organisms will depend on the definition of sympatry that one uses. Like many of our current species concepts, the typical definition of sympatry is not widely applicable to parasites. Revisiting the historically defined conditions for sympatric speciation and considering the situations in which we might regard parasites as being sympatric leads us to question the classic prediction that parasites have a greater tendency to speciate in sympatry than do free-living organisms.

Animals↗
PubMed2002

Metal speciation in natural waters with emphasis on reduced sulfur groups as strong metal binding sites.

The proper application of biotic ligand models to predict metal toxicity depends on accurate prediction of metal binding to sites on natural organic matter (NOM) which compete with the 'biotic' ligand for available metal. A hard and soft metal classification along with associated ligand groups (carboxyl, phenolic, amino, sulfidic) are used as a basis to predict metal speciation in the presence of aqueous organic matter. Compilation of conditional metal formation constants (log K') are made for each ligand type using model ligands. Model ligands were chosen to reflect those found in NOM and bio-organic media. Total ligand concentration (L(T)) estimates for different natural settings and log K' values are then used to generate a L(T)-log K' distributions for a specific metal. A plot for Cu(II) gives a similar trend as a compilation of measured data for natural environments. A log K'-L(T) plot for Ag(I) shows a much more discrete binding pattern than for Cu(II). Estimation of speciation of a specific metal in a specific environmental setting and to design speciation and toxicological experiments requires accurate knowledge of the functional groups in NOM.

Animals↗
PubMed2000

Speciation of metallothionein-like proteins of the mussel Mytilus edulis at basal levels by chromatographic separations coupled to quadrupole and double-focusing magnetic sector ICPMS.

Characterization and partial purification of metallothionein-like proteins (MLPs) of the mussel Mytilus edulis from natural populations of three coastal regions in Spain were performed. Size exclusion chromatography (SEC) with quadrupole (Q-ICPMS) or double-focusing inductively coupled plasma mass spectrometry (DF-ICPMS) detection was used first for speciation of cadmium in such natural samples and those of mussels exposed to 500 mg x L(-1) Cd in an aquarium tank. SEC results showed always a single Cd-MLP peak (MLP fraction). The contents in Cd, Cu, and Zn of this MLP fraction, of the high molecular weight protein pool (HMW), and of the whole cytosol were then measured by DF-ICPMS. Then, a given aliquot (50 microL) of MLPs with the highest values for UV molecular absorption at 254 nm (also the maximum sulfur and Cd, Cu, or Zn contents) was used to further fractionation. Fast protein liquid chromatography "on line" with Q-ICPMS was used for the purpose. Two Cd-MLP isoforms (MLP-1, MLP-2), with retention times (tR) of 15.7 and 16.0 min, were then detected in cytosols of the mussel samples of aquarium tank and also of the industrial area and Galicia coast. Conversely, wild coast mussels did not show any Cd-MLP signals at all. Analysis of essential elements copper and zinc in such cytosols by FPLC-Q-ICPMS revealed that these two metals were associated just to MLP-1. These results tend to indicate a different role for the two MLP isoforms detected in mussels (i.e., essential metals' homeostasis role seems to be tied to the MLP-1 isoform only). They illustrate the fact that trace metal speciation of unknown species in biological materials is becoming a challenge and points to the use of several complementary analytical techniques to obtain the required speciation information.

Animals↗
PubMed2001

Microwave digestion of environmental and natural waters for selenium speciation.

A microwave preparation procedure is proposed for selenium speciation in natural and drinking waters. Different chemical reagents were tested, and the conditions for Se speciation were optimized. The effect of the different reagents on various oxidation states of selenium under microwave digestion conditions was investigated. Most of the Se(-II) was converted to selenite when digested with HNO3 and <20% to selenate. The digestion with H2O2/H2SO4 can change most Se species into Se(IV). The concentration of Se(IV) in the samples was then determined by HPLC with a fluorescence detector after derivatization with 2,3-diamino-naphthalene (DAN). The microwave preparation procedure allows Se speciation in water samples. Se(IV) was determined after concentrating the sample under nitrogen protection. The amount of Se(IV) and Se(VI) was measured by adding an equal volume of concentrated hydrochloric acid to water sample to reduce Se(VI) to Se(IV). Then the amount of Se(VI) can be calculated by subtraction. The total selenium can be determined after digestion with H2O2/H2SO4, or after digestion with HNO3 followed by reduction with concentrated hydrochloric acid. Selenium (-II, 0) was calculated by subtracting inorganic Se(IV+VI) from the total. Detection limits of 0.0066 ng and 0.0096 ng Se were obtained for HNO3 and H202/H2SO4 as digestion reagents, respectively. The total Se in the four water samples tested range from 0.20 to 0.90 microg L(-1). Among them the dominant form was Se(VI) with the exception of pond waters where Se(-II) predominated.

Chromatography, High Pressure Liquid↗
PubMed2005

Determination of metal speciation by reverse titrations.

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 fraction: it is therefore a reverse titration rather than the forward titration which is used for conventional complexing ligand titrations. The sensitivity is greatest at the lowest free metal ion concentration, where it matters most, and the method can be carried out in a single sample aliquot in the voltammetric cell. The method is applied here to copper speciation, but in principle, it can also be used for other metals. Modeling shows that this method has good sensitivity at ligand concentrations near the metal concentration (lower as well as greater). Comparative measurements of copper speciation using reverse and forward titrations of representative water samples of oceanic and coastal origin show good agreement. The data showed that these samples did not contain low levels of strong ligands in addition to the ligands detected by the forward titrations.

Journal Article↗
PubMed2001

Fate of selenium in coal combustion: volatilization and speciation in the flue gas.

In light of Title I of the Clean Air Act Amendments of 1990, selenium will most probably be considered for regulation in the electric power industry. This has generated interest for removing this element from fossil-fired flue gas. This study deals with coal combustion: selenium volatilization and its speciation in the cooled flue gas were investigated to better understand its chemical behavior to validate the thermodynamic approach to such complex systems and to begin developing emission control strategies. Se volatility is influenced by several factors such as temperature, residence time, fuel type, particle size, and Se speciation of the fuels, as well as the forms of the Se inthe spiked coal/coke. Spiked coke and coal samples were burned in a thermobalance, and atomic Se and its dioxide were identified in the cooled combustion flue gas by X-ray photoelectron spectroscopy (XPS). A thermodynamic calculation was applied to a complex system including 54 elements and 3,200 species that describes the coal combustion. Several theoretical predictions concerning Se behavior, such as its speciation in flue gas, agreed well with experiments, which supports using thermodynamics for predicting trace element chemistry in combustion systems.

Air Pollutants↗
PubMed2002

Metal speciation dynamics and bioavailability: Zn(II) and Cd(II) uptake by mussel (Mytilus edulis) and carp (Cyprinus carpio).

In the analysis of metal biouptake from complexing environments, both chemical speciation and biological uptake characteristics have to be taken into account. The commonly used free ion activity model is based on equilibrium speciation and implies that diffusion of the bioactive free metal toward the organism is not rate-limiting. In the presence of complexes, however, sufficiently labile species might contribute to the biouptake via preceding dissociation. Coupling of the ensuing diffusional mass transfer flux of metal with the biouptake flux of free metal, the supposedly bioactive species, shows under which conditions labile metal complexes can contribute to the uptake. The goal of the present paper is to apply this type of analysis to experimental data on metal uptake by mussel (Mytilus edulis) and carp (Cyprinus carpio) in complexing environments. These biosystems have fairly well-characterized uptake parameters, but the uptake fluxes cannot be fully explained by considering equilibrium speciation only. For Zn(II) uptake by mussel, evidence was found for diffusional limitation at low concentrations, whereas for Cd(III) uptake by carp, diffusion is not limiting at all. The analysis provides an example of how a more comprehensive treatment of complex systems can be applied to real experimental data.

Animals↗
PubMed2002

Effects of Fe(III) chemical speciation on dissimilatory Fe(III) reduction by Shewanella putrefaciens.

Shewanella putrefaciens, a heterotrophic member of the gamma-proteobacteria is capable of respiring anaerobically on Fe(III) as the sole terminal electron acceptor (TEA). Recent genetic and biochemical studies have indicated that anaerobic Fe(III) respiration by S. putrefaciens requires outer-membrane targeted secretion of respiration-linked Fe(III) reductases. Thus, the availability of Fe(III) to S. putrefaciens may be governed by equilibrium chemical speciation both in the solution phase and at the bacterial cell-aqueous or cell-mineral interface. In the present study, effects of Fe(III) speciation on rates of bacterial Fe(III) reduction have been systematically examined by cultivating S. putrefaciens anaerobically on a suite of Fe(III)-organic complexes as the sole TEA. The suite of Fe(III)-organic complexes spans the range of stability constants normally encountered in natural water systems and includes Fe(III) complexed to citrate, 5-sulfosalicylate, NTA, salicylate, tiron, and EDTA. Rates of bacterial Fe(III) reduction in the presence of dissolved chelating agents correlate with the thermodynamic stability constants of the Fe(III)-organic complexes, implying that chemical speciation governs Fe(III) bioavailability. Equilibrium Fe(III) sorption experiments measured the reversible coordination of Fe(III) with S. putrefaciens as a function of cell/Fe(III) concentration, time, and activity of competing chelating agents. Results show that S. putrefaciens readily sorbs dissolved Fe(III) but that adsorption is restricted by the presence of strong Fe(III)-chelating agents. Our results indicate that dissimilatory Fe(III) reduction by S. putrefaciens is controlled by equilibrium competition for Fe(III) between dissolved organic ligands and strongly sorbing functional groups on the cell surface.

Biological Availability↗
PubMed2002

Measurement of heavy metal speciation over redox gradients in natural water-sediment interfaces and implications for uptake by benthic organisms.

The sediment or fauna incubation experiment (SOFIE) is an experimental research tool that was developed to analyze concentrations and chemical speciation of heavy metals in pore waters of natural, undisturbed sediments or water-sediment interfaces over time, while simultaneously conducting exposure tests with sediment-dwelling organisms. In this way, concentrations of chemical species are directly linked to accumulation by biota. It is shown that discrete gradients of redox-sensitive metals and nutrients occur over very small intervals. These gradients differ from those of free metal ion activities. Speciation affects the uptake of metals by sediment-dwelling organisms, which, in their turn, have a significant effect on metal speciation. With reaction kinetics that differ per metal, uptake of metals by organisms from the water phase may be hindered (e.g., Cu, Zn) or promoted (e.g., Ni, As). Time-varying exposure concentrations of metals were incorporated in uptake and elimination models. Body concentrations of Cd, Cu, Ni, and Zn in the aquatic oligochaete Limnodrilus could best be described by the time-varying free ion concentration in the overlying water. Body concentrations of As and Pb were best described by sediment pore water concentrations. It is concluded that SOFIE provides the necessary experimental tool to support, in a mechanistic way, environmental risk assessments of contaminants.

Animals↗
PubMed2003

Chemical speciation of Zn, Cd, Cu, and Pb in pore waters of agricultural and contaminated soils using Donnan dialysis.

Knowledge of trace metal speciation in soil pore waters is important in addressing metal bioavailability and risk assessment of contaminated soils. Numerous analytical methods have been utilized for determining trace metal speciation in aqueous environmental matrixes; however, most of these methods suffer from significant interferences. The Donnan dialysis membrane technique minimizes these interferences and has been used in this study to determine free Zn2+, Cd2+, Cu2+, and Pb2+ activities in pore waters from 15 agricultural and 12 long-term contaminated soils. The soils vary widely in their origin, pH, organic carbon content, and total metal concentrations. Pore water pM2+ activities also covered a wide range and were controlled by soil pH and total metal concentrations. For the agricultural soils, most of the free metal activities were below detection limit, apart from Zn2+ for which the fraction of free Zn2+ in soluble Zn ranged from 2.3 to 87% (mean 43%). Five of the agricultural soils had detectable free Cd2+ with fractions of free metal ranging from 59 to 102% (mean 75%). For the contaminated soils with detectable free metal concentrations, the fraction of free metal as a percentage of soluble metal varied from 9.9 to 97% (mean 50%) for Zn2+, from 22 to 86% (mean 49%) for Cd2+, from 0.4 to 32.1% (mean 5%) for Cu2+, and from 2.9 to 48.8% (mean 20.1%) for Pb2+. For the contaminated soils, the equilibrium speciation programs GEOCHEM and WHAM Model VI provided reasonable estimates of free Zn2+ fractions in comparison to the measured fractions (R2 approximately 0.7), while estimates of free Cd2+ fractions were less agreeable (R2 approximately 0.5). The models generally predicted stronger binding of Cu2+ to DOC and hence lower fractions of free Cu2+ as compared with the observed fractions. The binding of Cu2+ and Pb2+ to DOC predicted by WHAM Model VI was much strongerthan that predicted by GEOCHEM.

Agriculture↗
PubMed2004

Understanding the effects of soil characteristics on phytotoxicity and bioavailability of nickel using speciation models.

Acidity (pH) has been realized to be the most important soil characteristic that modulates bioavailability of heavy metals by affecting both the chemical speciation of metals in soil and the metal binding to the active sites on biota. In this work, we show that besides soil pH, metal bioavailability also depends to a certain extent on the type of soil. A better understanding of the role of soil type in regulating metal availability can be achieved with the analysis of soil composition and with calculations using chemical speciation models. Results of pot experiments, in which three different soils were spiked with nickel, show that the EC50 of total nickel in decreasing the biomass production of oats varies widely (0.7-22.5 mmol kg(-1) soil, more than 30 times). pH (4.7-7.0) is the most important factor, explaining up to a factor of 14 difference of nickel bioavailability in the soils. The remaining variation is caused by other differences in soil composition (soil type). The bioavailability and toxicity of nickel in the organic matter-rich soil studied is less than half of that in the sandy and clay soil studied at a similar pH. The chemical calculations using a multi-surface speciation model show that soil organic matter binds Ni much stronger than clay silicates and iron (hydr)oxides within the acidic pH range, which supports the experimental findings. In all three soils, the EC50 of Ni expressed in terms of Ni in 0.01 M CaCl2 soil extraction is rather stable (24-58 microM), suggesting the possibility to use this extraction as an estimation of metal availability in soil.

Aluminum Silicates↗
PubMed2004

Partitioning of metal species during an enriched fuel combustion experiment. speciation in the gaseous and particulate phases.

Combustion processes are the most important source of metal in the atmosphere and need to be better understood to improve flue gas treatment and health impact studies. This combustion experiment was designed to study metal partitioning and metal speciation in the gaseous and particulate phases. A light fuel oil was enriched with 15 organometallic compounds of the following elements: Pb, Hg, As, Cu, Zn, Cd, Se, Sn, Mn, V, Tl, Ni, Co, Cr, and Sb. The resulting mixture was burnt in a pilot-scale fuel combustion boiler under controlled conditions. After filtration of the particles, the gaseous species were sampled in the stack through a heated sampling tube simultaneously by standardized washing bottles-based sampling techniques and cryogenically. The cryogenic samples were collected at -80 degrees C for further speciation analysis by LT/GC-ICPMS. Three species of selenium and two of mercury were evidenced as volatile species in the flue gas. Thermodynamic predictions and experiments suggest the following volatile metal species to be present in the flue gas: H2Se, CSSe, CSe2, SeCl2, Hg(0), and HgCl2. Quantification of volatile metal species in comparison between cryogenic techniques and the washing bottles-based sampling method is also discussed. Concerning metal partitioning, the results indicated that under these conditions, at least 60% (by weight) of the elements Pb, Sn, Cu, Co, Tl, Mn, V, Cr, Ni, Zn, Cd, and Sb mixed to the fuel were found in the particulate matter. For As and Se, 37 and 17%, respectively, were detected in the particles, and no particulate mercury was found. Direct metal speciation in particles was performed by XPS allowing the determination of the oxidation state of the following elements: Sb(V), Tl(III), Mn(IV), Cd(II), Zn(II), Cr(III), Ni(II), Co(II), V(V), and Cu(II). Water soluble species of inorganic Cr, As, and Se in particulate matter were determined by HPLC/ICP-MS and identified in the oxidation state Cr(III), As(V), and Se(IV).

Air Pollutants↗
PubMed2004

Speciation of hepatic Zn in trout exposed to elevated waterborne Zn using X-ray absorption spectroscopy.

The long-term impacts of chronic metal exposure for aquatic biota are not well understood, partly due to a lack of understanding of metal speciation within tissues. The objective of this study was to determine hepatic Zn speciation of rainbow trout (Oncorhnychus mykiss) exposed to Zn-enriched water in relation to unexposed (control) fish,through direct analysis of freeze-dried liver samples using synchrotron X-ray absorption spectroscopy (XAS). Juvenile rainbow trout (n=30) were exposed to Zn in a two-step process, 200 microg L(-1) for 14 days, followed by 370 microg L(-1) for 23 days. Thirty other trout were grown in a control treatment (10 microg Zn L(-1)). At the end of the experiment, three liver samples per treatment were collected, freeze-dried, ground, and mixed homogeneously. Although Zn concentration was higher in the Zn-exposed livers than in the control livers (22.32 vs 13.73 mg kg(-1), respectively; p < 0.05), Zn speciation was similar for both groups. Extended X-ray absorption fine structure (EXAFS) spectroscopy indicated that Zn was coordinated to 4 sulfur atoms with an average Zn-S bond distance of 2.31 +/- 0.02 A. Sulfur K-XANES analysis confirmed that S was predominantly in reduced organic form analogous to cysteine. Our results are consistent with previous evidence for Zn(II) bonding to S in metallothionein proteins. These results suggest that the mechanisms for dealing with the extra load of bioaccumulated Zn in high exposure conditions were the same as in the control group.

Absorptiometry, Photon↗
PubMed2004

Zn speciation in the organic horizon of a contaminated soil by micro-X-ray fluorescence, micro- and powder-EXAFS spectroscopy, and isotopic dilution.

Soils that have been acutely contaminated by heavy metals show distinct characteristics, such as colonization by metal-tolerant plant species and topsoil enrichment in weakly degraded plant debris, because biodegradation processes are strongly inhibited by contamination. Such an organic topsoil, located downwind of an active zinc smelter and extremely rich in Zn (approximately 2%, dry weight), was investigated by X-ray diffraction, synchrotron-based X-ray microfluorescence, and powder- and micro-extended X-ray absorption fine structure (EXAFS) spectroscopy for Zn speciation and by isotopic dilution for Zn lability. EXAFS spectra recorded on size fractions and on selected spots of thin sections were analyzed by principal component analysis and linear combination fits. Although Zn primary minerals (franklinite, sphalerite, and willemite) are still present (approximately 15% of total Zn) in the bulk soil, Zn was found to be predominantly speciated as Zn-organic matter complexes (approximately 45%), outer-sphere complexes (approximately 20%), Zn-sorbed phosphate (approximately 10%), and Zn-sorbed iron oxyhydroxides (approximately 10%). The bioaccumulated Zn fraction is likely complexed to soil organic matter after the plants' death. The proportion of labile Zn ranges from 54 to 92%, depending on the soil fraction, in agreement with the high proportion of organically bound Zn. Despite its marked lability, Zn seems to be retained in the topsoil thanks to the huge content of organic matter, which confers to this horizon a high sorption capacity. The speciation of Zn in this organic soil horizon is compared with that found in other types of soils.

Air Pollutants↗
PubMed2005

Speciation of Zn associated with diatoms using X-ray absorption spectroscopy.

The long- and short-term interactions between zinc, an essential but also toxic element, and freshwater and marine diatoms are not well understood partly because of a lack of information on Zn speciation on the surface and inside the cells. In this work, interactions of aqueous Zn2+ with marine (Skeletonema costatum) and freshwater (Achnanthidium minutissimum, Navicula minima, and Melosira varians) diatoms were studied using conventional macroscopic techniques, while the local atomic structure of metal ions adsorbed on their surface or incorporated into the cells was characterized by in-situ Zn K-edge X-ray absorption fine structure (XAFS) spectroscopy on both intact and liophylized samples. At the cell surface for all diatom species studied, Zn was tetrahedrally coordinated with oxygen at approximately 2.00 +/- 0.02 A and monodentately bonded to one or two carboxylate groups; these results are consistent with the surface speciation model developed from macroscopic adsorption experiments. The atomic environment of Zn incorporated into freshwater diatoms during long-term growth in normal nutrient media was distinctly differentfrom that of adsorbed Zn: it was dominated by O (and/or N) neighbors in a tetrahedral arrangement at 1.97 +/- 0.02 A in the first atomic shell, with the presence of 1 phosphorus and 2 carbons in the Zn second shell. Contrasting speciation of intracellular zinc was revealed for the marine species Skeletonema costatum in which Zn was coordinated to 2 O/N atoms and 2 sulfur groups in the form of cysteine-histidine complexes and/or zinc thiolate clusters. These new structural data strongly suggest: (i) the predominant > R-COO- ligand binding of Zn atthe diatom surface; (ii) the nonspecific storage of Zn in the form of carboxylate/phosphate groups inside the cell of freshwater species; and (iii) the highly specific thiol-ligand coordination of intracellular zinc for marine S. costatum species.

Diatoms↗