nM For Zn Research Articles

Early Diagenetic Processes in the Sediments of the Krka River Estuary

To study the processes that govern the post-depositional mobility of metals in the estuarine sediment, five sediment cores were sampled in the Krka River estuary (Croatia). The obtained concentration ranges in the pore water were 0.057–49.7 μM for Fe, 0.310–100 μM for Mn, 0.068–26.8 nM for Co, 0.126–153 nM for Cu, 11.5–2793 nM for Zn, 0.222–31.3 nM for Pb, 4.09–59.4 nM for U, 38.8–2228 nM for Mo, and 0.065–2.29 nM for As. The vertical distribution of metals in the dissolved and solid fraction of the sediment, coupled with other diagenetic tracers (e.g., dissolved sulphide), demonstrate the importance of early diagenetic reactions, in particular Fe and Mn oxyhydroxide and sulphate reduction, for the cycling of metals in the sediment. The redox zonation in the sediment was compressed, and the suboxic zone occurs immediately below the sediment–water interface. The estimated benthic fluxes in the estuary were 5220 kg y−1 for Fe, 27,100 kg y−1 for Mn, 6.00 kg y−1 for Co, 20.5 kg y−1 for Cu, 5.16 kg y−1 for Pb, 111 kg y−1 for Mo, and 87.3 kg y−1 for As. The riverine input was more important than the benthic flux, except in the case of Mn and Fe.

Spatial distribution of paddy field’s heavy metals diversity contamination in Samarinda using remote sensing imagery

Abstract. Palupi NP, Hardi EH, Fahrunsyah, Rahayu DE, Nugroho RA, Darma S, Idris SD. 2023. Spatial distribution of paddy field’s heavy metals diversity contamination in Samarinda using remote sensing imagery. Biodiversitas 24: 6743-6752. The adverse effects of heavy metal contamination on rice fields posing a significant threat to food safety. This study, conducted from May to July 2023 in Samarinda East Kalimantan, Indonesia, aims to determine the distribution of active rice fields and heavy metal contamination through Kriging's interpolation method. Aerial photographic interpretations, facilitated by ArcGIS 10.4, were performed with 144 sample points within 4 Districts. The content of heavy metals was assessed by Atomic Absorption Spectroscopy at specific wavelengths: 248.3 nm for Fe, 228.8 nm for Pb, 283.3 nm for Cd, 357.9 nm for Cr, 279.5 nm for Mn, 213.9 nm for Zn, and 324.7 nm for Cu, following guidelines of SNI 8910:2021. The research showed that existing rice fields were concentrated in North Samarinda District (380,416 ha), Loa Janan Ilir District (210,133 ha), Sambutan District (404,682 ha), and Palaran District (188,617 ha) with Fe content ranged from 4.976,45 ppm to 16.800,485 ppm, exceeding the critical Fe limit in soil of 500 ppm set by SNI. Mn content ranged from 22.65 ppm to 564.88 ppm, surpassing the critical soil threshold of 0.15 ppm for Mn according to SNI. Cu content varied from 3.32 ppm to 121.75 ppm, exceeding critical Cu limit of 0.04 ppm. Zn content ranged from 8.61 ppm to 223.12 ppm, surpassing the critical limit of Zn's pollution in the soil (0.06 ppm). Pb content ranged from 10.72 ppm to 32,84 ppm, categorized as intermediate compared to the threshold of 0.07 ppm for Pb in soil. Cd content ranged from 0.04 ppm to 0.739 ppm, exceeding the critical limit of 0.01 ppm set by SNI. Cr content was detected to be less than 0.032 ppm, falling into a very low category, with the critical limit for Cr content in soil set at 0.5 ppm according to SNI.

Prediction of soil nutrients through PLSR and SVMR models by VIs-NIR reflectance spectroscopy

Though soil nutrients play important roles in maintaining soil fertility and crop growth, their estimation requires direct soil sampling followed by laboratory analysis incurring huge cost and time. In this research work, soil nutrients were predicted using VIs-NIR reflectance spectroscopy (range 350–2500 nm) with Partial Least Squares Regression (PLSR) and Support Vector Machine Regression Model (SVMR) model through principal component analysis. Two hundred soil samples were collected from Tarekswar, Hooghly, West Bengal, India to predict eight selected soil nutrients, such as soil organic carbon (OC), pH, available nitrogen (N), available phosphorus (P), available potassium(K), electric conductivity (EC), zinc (Zn) and soil texture (sand, silt, and clay) levels. The OC content was predicted with sound accuracy (R2: 0.82, RPD: 2.28, RMSE: 0.13, RPIQ: 4.15 FD-SG), followed by P (R2: 0.71, RPD: 1.83, RMSE: 4575, RPIQ: 3.44 1st derivative). The soil parameters sensitive to the particular band of visible spectrum were also identified viz. wavelengths of 409, 444, 591 and 592 nm for OC, 430 and 505 nm for P, 464 nm for K; 580 nm for Zn, 492,511,596 and 698 nm for N; 493, 569 and 665 nm for EC; 492,567 and 652 nm for pH; 457 nm for sand and 515 nm for clay.The soil nutrient levels were predicted by PLSR and SVMR models through PCA and Sentinel 2 imagery and soil suitability map were also generated for seven soil parameters such as OC, pH, EC, N, P, K and clay content. Through map query tool in ArcGIS software environment the PLSR and SVMR model successfully identify the suitability class with level of accuracy of 87.2% and 88.9%, respectively, against the direct soil analysis based suitability mapping.The machine learning technique based soil nutrient and soil suitability prediction can be easily adopted in different regions. This will reduce the cost of laboratory soil analysis and optimize the total time requirement.

Fe3O4 nanochips loaded MXenes/g-C3N4 nanocomposite for ultrasensitive electrochemical detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions

The present work demonstrates a highly sensitive and efficient nanosensor for the simultaneous detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions using Ti3C2/Fe3O4/g-C3N4 nanocomposite. The Ti3C2/Fe3O4/g-C3N4 nanocomposite was prepared using co-prcepitation method followed by ultrasonication treatment containing Ti3AlC2, ferrous sulfate, ferric chloride and melamine as precursors. The as-prepared nanocomposites were successfully examined using XRD, FTIR, SEM and cyclic voltammetric techniques. Differential pulse anodic stripping voltammetry (DPASV) technique was applied for the simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The electrochemical variables including pH of the solution, amount of Ti3C2/Fe3O4/g-C3N4 on the GCE surface, supporting electrolyte and deposition time were optimized to get maximum sensitivity. Under optimal conditions, Ti3C2(HF)/Fe3O4/g-C3N4 sensor exhibited excellent performance for Zn (II), Cu (II), Cd (II), Pb (II) and Hg (II) in a range from 0.5 to 0.005 μM with detection limits 0.26 nM for Zn (II), 0.21 nM for Cd (II), 0.10 nM for Pb (II), 0.11 nM for Cu (II) and 0.12 nM for Hg (II) which are lower than the permissible limit recommended by the WHO guidelines. The sensor also shown outstanding selectivity in the presence of various foreign species (Ca2+, Mg2+, Na1+, Cl1-, NO31-, and 4-nitrophenol) and high resolution for simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The good electroanalytical performance and excellent selectivity and sensitivity of developed nanosensor can be attributed to the heterostructure and the coordination provided by MXene and Fe3O4/g-C3N4, resulting in enhanced interfacial charge transfer and number of adsorption sites. In addition, the developed sensor was applied for the detection of metal ions in tap water samples and satisfactory results were obtained. This study highlights a facile approach for designing MXene-supported magnetic NPs/ N containing carbon materials as sensing platform for the detection of other toxic heavy metal ions.

Highly fluorescent metal doped carbon quantum dots prepared from hen feather demonstrating pH-dependent dual sensing of 4-nitrophenol and Hg2+ ion

Mg/Zn modified carbon quantum dots (CQD) were synthesized from hen feather for the fluorescence-based pH dependent optical sensing of mercury (Hg2+)and p-Nitrophenol (4-NP). TEMimaging confirmed the size of QDs as ∼ 3.4 nm for Mg doped CQDs (MgCQD) and ∼ 4.09 nm for Zn doped CQDs (ZnCQD). ZnCQD showed the lowest band gap, and highest fluorescence quantum yield (QY) compared to native CQD and MgCQD. MgCQD and ZnCQD demonstrated 70% and 52% fluorescence quenching, respectively, in the presence of 20 ppm of Hg2+at pH 7. For0–20 ppm Hg2+concentration range, two linear detection regions were observed by both the QDs. Further, the prepared QDs also showed high selectivity towards 4-NP at pH 2. The detection of 4-NP was highly linear for both MgCQD and ZnCQD. The fluorescence of MgCQD and ZnCQD was found quenched more than 90% in the presence of 20 ppm 4-NP in acidic pH. Therefore, our synthesized metal-doped QDs prepared fromhen feather wastedemonstrated efficient pH-responsive dual sensing of Hg2+and 4-NP and are alsovery cheap, rapid, and can be used for multifunctional pollutant detection in the aquatic environment.

Synthesis and study of zinc oxide nanoparticles and their nanocomposites

Zinc oxide nanoparticles (ZnO NPs) was synthesized via chemical route using sodium hydroxide and zinc chloride (ZnCl2) as a precursor. Zinc oxide nanoparticles/Nanographite-oxide nanocomposite (ZnO/NGO) were synthesized by solution method. The calcination temperature of zinc oxide nanoparticles was 600 °C. The crystal structure of ZnO NPs with average size 32.99 nm was measured by XRD. FT-IR spectrum was used to confirm the presence of functional groups in ZnO and Zn(OH)2 NPs. The dynamic light scattering (DLS) gave a wider nanoparticle size distribution in two peaks with average 725 nm, also the BET and BJH analysis indicated that ZnO NPs / NGO nanocomposite have a well surface area with good nanoparticles diffusion compering as ZnO NPs. The morphology analysis by FESEM technique was given different sizes and shapes nanoparticles (oval, sheet and cubic) with average diameters extended 228.065 and 134.784 nm , 39.63 and 127 nm for Zn(OH)2 and ZnO NPs , NGO sheet and ZnO/NGO nanocomposite respectively.

The recovery of metals as high value powders and nanopowders from industrial wastewaters using potential-controlled electrolysis

The objective of the presented study was the recovery of Zn, Cr, Cu and Co in the form of powders and nanopowders from various types of industrial wastewaters. Powders and nanopowders as products of high added value find a wide applications in nanotechnology and material science and engineering. The metallic powders were obtained using potentiostatic electroreduction (potential-controlled electrolysis). The chosen method offers better control of the purity and structure of the products. The structure and size of crystallites depend on the value of electrolysis potentials and time, cathode material, concentrations of metal ions. In this investigation, the powders of different sizes ranging from 90 to 230 nm for Cr, 100–4000 nm for Zn, 25–100 nm for Co and 40–660 nm for Cu were deposited. The compositions, purity and size of the cathode deposits were confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Presented metal recovery method is a promising technique for industrial application, given its simplicity, economic viability and environmental sustainability. It can be used on a wide range of solutions and help in reducing the problem of the growing amounts of industrial wastewater.

Dissolved Trace Metals and Organic Matter Distribution in the Northern Adriatic, an Increasingly Oligotrophic Shallow Sea

We report a monthly distribution of Zn, Cd, Pb, Cu, Ni and Co, biologically relevant trace metals (TMs), within one year, in the productive surface layer at two stations with different trophic characters in the northern Adriatic (NA). The TM data was accompanied by a multivariable dataset, including dissolved organic carbon (DOC), surface-active organic substances (SAS), nitrogen-containing polymeric organic material (N-POM), nutrients, pH, dissolved O2, chlorophyll a (Chl a), seawater temperature, and the Po River discharge rate. At the eu- to mesotrophic station 108, the concentrations of dissolved TMs were 5–116 nM for Zn, 0.04–0.18 nM for Cd, 0.05–0.63 nM for Pb, 3–17 nM for Cu, 4–11 nM for Ni, and 0.2–1.2 nM for Co, while at the oligotrophic station 107, they were 6–224 nM for Zn, 0.03–0.16 nM for Cd, 0.05–1.25 nM for Pb, 3–17 nM for Cu, 4–19 nM for Ni, and 0.1–0.7 nM for Co. The characterization of organic matter (OM) in conjunction with the analysis of correlations with TMs indicated that the OM–TMs interactions differed between the two stations; namely, the freshly produced OM detected at station 108 was probably involved in the complexation of Cu, Co, Cd, and Ni, whereas at station 107, such complexation processes were not present. Accumulation of DOC was observed during the summer months at both stations. Our results present a significant contribution to biogeochemical studies in the NA by focusing on the complexity of TM–OM interactions, which is a prerequisite for interpretation of their responses to local and global changes.

Corrosion Resistance and Cytocompatibility of Magnesium-Calcium Alloys Modified with Zinc- or Gallium-Doped Calcium Phosphate Coatings.

In orthopedic surgery, metals are preferred to support or treat damaged bones due to their high mechanical strength. However, the necessity for a second surgery for implant removal after healing creates problems. Therefore, biodegradable metals, especially magnesium (Mg), gained importance, although their extreme susceptibility to galvanic corrosion limits their applications. The focus of this study was to control the corrosion of Mg and enhance its biocompatibility. For this purpose, surfaces of magnesium-calcium (MgCa1) alloys were modified with calcium phosphate (CaP) or CaP doped with zinc (Zn) or gallium (Ga) via microarc oxidation. The effects of surface modifications on physical, chemical, and mechanical properties and corrosion resistance of the alloys were studied using surface profilometry, goniometry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), nanoindentation, and electrochemical impedance spectroscopy (EIS). The coating thickness was about 5-8 μm, with grain sizes of 43.1 nm for CaP coating and 28.2 and 58.1 nm for Zn- and Ga-doped coatings, respectively. According to EIS measurements, the capacitive response (Yc) decreased from 11.29 to 8.72 and 0.15 Ω-1 cm-2 sn upon doping with Zn and Ga, respectively. The Ecorr value, which was -1933 mV for CaP-coated samples, was found significantly electropositive at -275 mV for Ga-doped ones. All samples were cytocompatible according to indirect tests. In vitro culture with Saos-2 cells led to changes in the surface compositions of the alloys. The numbers of cells attached to the Zn-doped (2.6 × 104 cells/cm2) and Ga-doped (6.3 × 104 cells/cm2) coatings were higher than that on the surface of the undoped coating (1.0 × 103 cells/cm2). Decreased corrosivity and enhanced cell affinity of the modified MgCa alloys (CaP coated and Zn and Ga doped, with Ga-doped ones having the greatest positive effect) make them novel and promising candidates as biodegradable metallic implant materials for the treatment of bone damages and other orthopedic applications.

Dynamics and diagenesis of trace metals in sediments of the Changjiang Estuary

The seasonal dynamics and diagenesis of trace metals at two contrasting coastal sites were studied to determine the mechanism that drove the diffusive release of trace metals from sediments in the Changjiang Estuary. Porewater trace metal concentrations were 53.4–4829 nM for Zn, 11.0–344 nM for Cu, 7.75–221 nM for Cr, 2.71–61.1 nM for Co, 0.822–42.7 nM for Pb and 0.037–4.22 nM for Cd. The concentrations and profiles of trace metals in the porewater and solid phase displayed obvious regional and seasonal variations. This variation was mainly reflected in the surface layer and the depth of the suboxic and anoxic layers. Regionally, surface porewater trace metal concentrations in the seasonal hypoxic region were higher than those in the aerobic region due to changes in the redox conditions being beneficial to the release of trace metals. Seasonally, surface porewater trace metal concentrations decreased in summer compared to spring due to their removal by forming metal sulfides in summer. Solid profiles of the trace metals supported their dynamic variations in the porewater. The partition coefficient suggested that the formation of Fe/Mn (hydr)oxides was effective for the removal of trace metal in oxidizing condition, while the formation of sulfides was conducive to the removal of trace metals in reducing condition. The combination of porewater with solid phase data suggested that the dynamics of Cu, Zn, Cr and Co were mainly controlled by Fe and Mn diagenesis, the dynamics of Cd were affected by S cycling, and the dynamics of Pb were disturbed by anthropogenic inputs and benthic organism activities. Estimation of benthic fluxes indicated that sediments were an important source of trace metals in the water column. The contributions of trace metals by sediments to the water column of the Changjiang Estuary were only one order of magnitude lower than those by riverine fluxes.

Effect of Temperature and Magnetic Dopants on Particle size and Electrical Properties of ZnO Ceramic Varistor

We report here structural and electrical properties of Zn0.95 M0.05O ceramic, M = Zn, Co and Mn. It is found that addition of magnetic doping did not influence the hexagonal wurtzite structure of ZnO. Furthermore, the lattice parameters ratio c/a for hexagonal distortion and the length of the bond parallel u to the c axis were nearly unaffected. The average crystalline diameters, deduced from XRD analysis are 83.75, 72.86 and 70.97 nm for Zn, Mn and Co, which are 15 times lower than those obtained from FESEM micrographs (1570, 1380 and 1150 nm). The breakdown field EB was decreased as the temperature increased, in the following order: Mn> Zn > Co. The nonlinear region was observed for all samples as the temperature increased up to 400 K and completely disappeared with further increase of temperature up to 500 K. The values of nonlinear coefficient, α were between 1.65 and 56 for all samples, in the following order: Mn> Zn > Co. Moreover, the electrical conductivity σ was gradually increased as the temperature increased up to 500 K, in the following order: Co > Zn > Mn. On the other hand, the activation energies were 0.194, 0.155 eV and 0.231 eV for all samples, in the following order Mn, Zn and Co. These results have been discussed in terms of valence states, magnetic moment and thermo-ionic emission which were produced by the doping, and controlling the potential barrier of ZnO.

Chelation-enhanced fluorescence of phosphorus doped carbon nanodots for multi-ion detection

The present paper reports on a chelation enhanced fluorescence (CHEF) effect that is observed on addition of certain metal ions to phosphorus doped carbon nanodots (P-CNDs). The effect is accompanied by a large shortwave shift of the emission peak. Highly passivated P-CNDs with sizes of around 3 nm were prepared from lactose and phosphoric acid, using a one-pot low temperature solvothermal method. The nanoparticles were purified according to polarity and size. The extent of blue shift and strength of enhancement depend on metal ions and actual pH value. For instance, the P-CND complex with Al(III) has a fluorescence that is shifted to shorter wavelengths, and the fluorescence quantum yield is enhanced from 12% (for the free P-CNDs) to almost 62% at 490 nm. The fluorescence is also enhanced and shifted by the ions Zn(II) and Cd(II). It is quenched by the ions Fe(II), Fe(III), Hg(II), Cu(II) and Sn(II), among others. The enhancement is attributed to the chelation of metal ions with the passivated surface functional groups of P-CNDs, mainly those of phosphorus. Phosphorous free CNDs (prepared via HCl instead of H3PO4) and low-passivated P-CNDs (prepared for longer period of time; typically 8 h) show no enhancement. The metal ion induced enhancement led to the design of a fluorometric assay for the detection of these ions. The detection limits are 4 nM for Al(III) and 100 nM for Zn(II). The two ions were quantified in spiked pharmaceutical formulations. Recoveries typically are 102% (for n = 7).

Thermal Conductivity and Viscosity of Vegetable Oil–Based Cu, Zn, and Cu–Zn Hybrid Nanofluids

Abstract Sustainable manufacturing can be considered as one of the most important issues, which use the processes that play down negative environmental impacts in pursuing the bigger picture of sustainable development. An eco-friendly cutting fluid will go along with machining to achieve relative sustainability. To achieve relative sustainability level in machining, eco-friendly nanofluids are developed in this paper. Nanofluid is a stable colloidal suspension of ultrafine solid particles in a nanometric dimension dispersed in conventional and lubrication fluids. A two-step approach of synthesis of Zn, Cu, and Cu–Zn nanoparticles by mechanical alloying, followed by dispersing them in a base fluid (vegetable oil) to prepare nanofluids has been adopted. Powder particles were characterized by x-ray diffraction (XRD) and a particle-size analyzer. It is found from the XRD results that the crystallite size was around 26 nm for Cu powders, 59 nm for Zn powders, and 25 nm for Cu–Zn alloy after 60 h of milling. The particles size reduced to 60 nm for Zn, 60 nm for Cu, and 70 nm for Cu–Zn alloy after 60 h of milling. The enhanced thermal conductivity for Zn, Cu, and Cu–Zn nanofluids were 36 %, 42 %, and 48 %, respectively, with a volume concentration of 0.5 %, compared to base fluid (vegetable oil). The enhancement in viscosity for Zn, Cu, and Cu–Zn nanofluids are 47 %, 53 %, and 61 %, respectively, with a volume fraction of 0.5 % were reported.

Ca(II) Binding Regulates and Dominates the Reactivity of a Transition-Metal-Ion-Dependent Diesterase from Mycobacterium tuberculosis.

The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal-ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn(II) to about 600 nm for Zn(II) . In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal-ion binding and enzymatic reactivity. Ca(II) also binds tightly to Rv0805 (Kd ≈40 nm), but kinetic, calorimetric, and spectroscopic data indicate that two Ca(II) ions bind at a site different from the dinuclear transition-metal-ion binding site. Ca(II) acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition-metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.

Protein expression from zooplankton communities in a metal contaminated NW mediterranean coastal ecosystem

Bidimensional and monodimensional polyacrylamide gel electrophoresis were used to study protein expression from zooplankton collected in thirteen stations of Toulon Bay (NW Mediterranean). In this ecosystem, Little Bay showed higher trace metal concentrations (13.5–23.8 nM for Cu, 0.73–1.24 nM for Pb, 27.8–58.7 nM for Zn) than Large Bay (Cu 2.2–15.6 nM; Pb 0.19–0.78 nM; Zn 9.0–38.8 nM). Trace metals positively correlated (p < 0.05) with expression of four zooplankton proteins (MW in kDa/pI: 25.0/5.6; 48.8/4.1; 38.2/4.4; 38.3/5.8) and with biomass of Oithona nana, predominant copepod in Little Bay. Sequencing by LC–MS/MS putatively provided zooplankton identity of these proteins: they were cytoskeleton actin, except one protein that was the chaperone calreticulin. We suggest that actin and calreticulin could be regarded as zooplankton markers of metal stress and be involved in a possible tolerance of O. nana to contamination, contributing to its development in a marine perturbed ecosystem.

The relevance of defining trace metal baselines in coastal waters at a regional scale: The case of the Portuguese coast (SW Europe)

The Water Framework Directives aims a reduction in concentration of hazardous substances in the marine environment. Consequently, there is a need to distinguish between anthropogenically influenced metal concentrations from natural background levels. To better achieve this goal in the Portuguese coast, dissolved and particulate trace metal (TM) concentrations along the Portuguese coast were determined in 46 sites distance 1–3 km from the shoreline. Dissolved values ranged within the following intervals: 0.01–0.89 nM for Cd, 0.01–3.37 nM for Co, 0.90–45.4 nM for Cu, 3.30–140 pM for Hg, 1.88–15.1 nM for Ni, 0.01–0.15 nM for Pb and 1.40–62.0 nM for Zn. Whereas Cd, Co, Cu, Ni and Zn were enhanced in the southern coast, while Pb values were higher in the central part of the western coast. Mercury concentrations showed punctual increases all along the coast. Values of trace metals in suspended particulate matter varied in a broad range: 36–2902 μmol g−1 for Al, 0.10–15.1 nmol g−1 for Cd, 1.50–165 nmol g−1 for Co, 50.0–990 nmol g−1 for Cu, 2.80–76.4 nmol g−1 for Hg, 22–1471 nmol g−1 for Ni, 10.0–347 nmol g−1 for Pb and 416–10,981 nmol g−1 for Zn. Higher values for Al, Ni and Co were found in the central part of the western coast. However, Cd, Cu, Pb and Zn increased their levels from the north coast towards the central and south areas. The variability of both dissolved and particulate metals appears to be mainly associated with oceanographic conditions and continental inputs at North and central areas of the coast, and in the south coast to geological features rather than to anthropogenic pressures. On the basis of these results, regional baseline concentrations are proposed for the three typologies in Portuguese coastal waters defined under the Water Framework Directive.

Polymorph‐Dependent Solid‐State Fluorescence and Selective Metal‐Ion‐Sensor Properties of 2‐(2‐Hydroxyphenyl)‐4(3H)‐quinazolinone

2-(2-Hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), an organic fluorescent material that exhibits fluorescence by the excited-state intramolecular proton-transfer (ESIPT) mechanism, forms two different polymorphs in tetrahydrofuran. The conformational twist between the phenyl and quinazolinone rings of HPQ leads to different molecular packing in the solid state, giving structures that show solid-state fluorescence at 497 and 511 nm. HPQ also shows intense fluorescence in dimethyl formamide (DMF) solution and selectively detects Zn(2+) and Cd(2+) ions at micromolar concentrations in DMF. Importantly, HPQ not only detects Zn(2+) and Cd(2+) ions selectively, but it also distinguishes between the metal ions with a fluorescence λ(max) that is blue-shifted from 497 to 420 and 426 nm for Zn(2+) and Cd(2+) ions, respectively. Hence, tunable solid-state fluorescence and selective metal-ion-sensor properties were demonstrated in a single organic material.

On the lability of dissolved Cu, Pb and Zn in freshwater: Optimization and application to the Deûle (France)

A procedure to determine lead and zinc by anodic stripping voltammetry and copper by cathodic stripping voltammetry in natural river samples was developed and validated. Cu determination involves the adsorption of Cu complexes with 8-hydroxyquinoline (oxine) onto a hanging mercury drop electrode. All samples were studied at natural pH and following optimal conditions were found: an accumulation step at −1.3V (all potential values in the paper are given versus the Ag/AgCl, [KCl]=3M reference electrode) during 30s for determination of Zn contents and at −0.7V during 60s for determination of Pb contents. Concerning Cu analysis, the optimal oxine concentration was found to be 10−5M with a deposition potential of −1.1V during 30s followed by an adsorption step at −0.25V during 15s. This procedure was afterwards validated by using certified reference freshwater and performing an intercalibration exercise. Finally the method was successfully applied in the Deûle River, highly contaminated by dissolved Zn and to a lesser extent by Pb and Cu, due to past and present activities of metallurgical plants. Under these optimal conditions, metal concentrations measured by our voltammetric procedures in the Deûle River were found in the range 12.4–23.2nM for Zn, 1.7–3.2nM for Pb and 4.9–7.6nM for Cu.

Estuary-ria exchange of cadmium, lead and zinc in the coastal system of the Ria of Vigo (NW Iberian Peninsula)

Little research has been done on the land-sea exchange of trace elements, which is particularly applicable to ria coasts. In particular, trace metal enrichment in the inner part of the Ria of Vigo (the San Simon Inlet) has been observed from sediment studies but there is no information about Cd, Pb and Zn fluxes through the Rande Strait, which is the natural boundary of the estuary-ria water exchange. In order to assess metal exchanges in a ria-type system, six sampling cruises on board the R/V Mytilus (IIM-CSIC) were carried out. Water column profiles of salinity, temperature and tidal currents were obtained every 30 min. The water column for dissolved and particulate metals was sampled every two hours over a complete tidal cycle. Dissolved metal concentrations were 0.01–0.18 nM for Cd, 0.5-1.9 nM for Pb and 4-44 nM for Zn. Compared with Zn (16±12%) and especially with Cd (5.4±5.0%), particulate metal represented a significant fraction of the total concentration for Pb (41±21%). Net fluxes of dissolved Cd and Zn are higher than in the particulate phase, whereas for Pb an inverse situation was observed. The net metal exchange in the Vigo estuary-ria environment was not seasonally controlled. Dissolved Cd and Pb were driven by tidal ranges and particulate Pb by the Oitaven River flow. On the other hand, Zn did not show a defined trend. The budgets obtained for the Ria of Vigo, with the exception of Pb, were one or two orders of magnitude lower than those measured in other large European estuaries.

Synthesis and electrochemical properties of bis(dipyrrinato)zinc complex derivatives

Naphthalene group with 1- or 2-link position was substituted into 5-position of dipyrrinato zinc complex and bis[5-(1-naphthalenyl)-dipyrrinato]zinc complex (Zn(1-NaPN) 2) and bis[5-(2-naphthalenyl)-dipyrrinato]zinc complex (Zn(2-NaPN) 2), which are the derivatives of bis(dipyrrinato)zinc complex, were successfully synthesized. The optical properties of the synthesized compounds were measured through UV-visible and PL spectrum. UV-visible maximum values in solution state, 485 and 486 nm for Zn(1-NaPN) 2 and Zn(2-NaPN) 2 have similar absorption maximum value and PL spectrum maximum values are 516 and 518 nm, respectively. In the film state, UV-visible maximum values, about 517 nm for both compounds, also indicated absorption of similar wavelengths. PL spectrum was shown to be about 550 nm which is also red-shifted about 33 nm from the solution state, moving toward yellowish green color. Zn(1-NaPN) 2 and Zn(2-NaPN) 2, the synthesized compounds, were measured on electrochemical kinetic properties through cyclic voltammogram (CV), and both materials showed similar oxidation voltage of about 0.7 V (vs. Ag/AgNO 3). The exponent of scan rate and x-value of Zn(1-NaPN) 2 and Zn(2-NaPN) 2 were 0.52 and 0.33, so the kinetics of Zn(1-NaPN) 2 is mainly controlled by diffusion process.