A chemometric survey of three sites in Muggia Bay (Northern Adriatic Sea): meteorological effects on heavy metal patterns in surface coastal waters

Within research on the quality of the waters of the Gulf of Trieste, this study on patterns of trace metal contents in the inner part of the gulf (Muggia Bay) discusses data of Cu, Pb, Cd and Zn, determined voltammetrically (DPASV), and collected in three sites with a 10-day frequency over the period of one year. Two of the sites lie inside the dam system which protects the harbour of Trieste, while the third one is situated outside for comparison purposes. Principal component analysis pointed out different metal patterns inside and outside the dam system; PC scores were related to meteorological information: rain plays a major role in conditioning the estuarine inner site: wind stirring action was detectable for the outer site. Both univariate graphics and canonical correlation analysis suggest a diffuse source for Pb, probably atmospheric deposition. Received: 1 August 1997 / Revised: 20 November 1997 / Accepted: 23 November 1997     

Toxic elements content in PM<Subscript>10</Subscript> samples from a coastal area of the Northern Adriatic Sea

PM₁₀ samples were collected during winter and summer seasons at two different sites in the area of Trieste (Italy). The content of As, Cd, Cr, Mn, Ni, Pb and V in the PM₁₀ samples was determined by inductively coupled plasma-mass spectrometry, with the purpose of evaluating the relevance of PM₁₀ inhalation as a route of human exposure to these elements. The results showed that the ambient air concentration of the aforementioned elements were below the limits or target values for both sites and season. Site and season-specific correlation analysis was conducted for the identification of metals with similar origin: very good correlation for the couple Ni-V was found in both sites and seasons, showing the influence of combustion of heavy oils in PM₁₀ composition. The inter-site and seasonal variability of both PM₁₀ and metal concentrations were examined. A stronger impact by the vehicular traffic on the PM₁₀ and metal concentrations was found for the urban site in both seasons. Because of the great importance of the “Bora” wind on the local climate, variability of PM₁₀ and toxic elements concentration with wind were analysed, allowing determination of the effect of wind on dilution of the pollutants for the urban site during both seasons.      

When do molecular bowls encapsulate metal cations?

Curved carbon π surfaces have chemical and physical properties suitable for exploitation for chemical microencapsulation and the self-assembly of nanoscale materials. Advances will greatly benefit from more understanding of their host-guest interactions with guests such as metal cations. Here, quantitative predictions are made for the binding of metal cations to three prototypical surfaces using density functional theory calculations: the buckybowls C(20)H(10), C(30)H(10), and C(40)H(10). The focus was on finding the most favorable binding sites, assessing whether binding is more favorable inside or outside the bowl, and exploring factors influencing the binding site preference. Classes of cations studied included small and large monocations and cations with multiple charges: Na(+), Cs(+), NH(4)(+), Ba(+), Ba(2+), and La(3+). Factors found to favor inside binding were large ion size and high ion charge, suggesting that polarization interactions as well as short-range interactions are important in determining the preferred binding sites inside and outside these buckybowls. Unlike monocations, which at best have only a weak tendency toward encapsulation, the multiply charged cations Ba(2+) and La(3+) were found to have a strong driving force toward containment inside the bowls. Coulomb potentials were found to favor cation binding on the outside surface of the bowls, but cation microsolvation through polarization interactions presents a compensating factor that can tip the balance in favor of encapsulation. Knowledge of these factors will be a valuable tool in the design of nanocontainers and the diverse architecture possible with these structural elements.     

Heterogeneity and liability of Pb(II) complexation by humic substances: practical interpretation tools

The complexation of Pb(II) by natural organic matter (NOM) is better described by taking into account the dependence of the strength of binding on metal loading conditions. The utility of a linear differential equilibrium function for interpretation of metal ion binding data is demonstrated. This approach considers the binding intensity (log K*) as a function of metal ion loading (theta = bound metal/binding site concentration). Three methods for calculating this function are presented: -direct calculation from metal titration curves, -direct calculation from polarograms, and -compilation of data derived from interpretation of complexation in terms of one- or two- binding sites (e.g. Scatchard analysis), i.e. Cc (complexation capacity = effective site concentration)-K pairs. Heterogeneity also impacts on the apparent lability of complexes; complexes formed at the lowest metal loadings are the least labile.     

Renewable Molecular Flasks with NADH Models: Combination of Light‐Driven Proton Reduction and Biomimetic Hydrogenation of Benzoxazinones

Using small molecules with defined pockets to catalyze chemical transformations resulted in attractive catalytic syntheses that echo the remarkable properties of enzymes. By modulating the active site of a nicotinamide adenine dinucleotide (NADH) model in a redox‐active molecular flask, we combined biomimetic hydrogenation with in situ regeneration of the active site in a one‐pot transformation using light as a clean energy source. This molecular flask facilitates the encapsulation of benzoxazinones for biomimetic hydrogenation of the substrates within the inner space of the flask using the active sites of the NADH models. The redox‐active metal centers provide an active hydrogen source by light‐driven proton reduction outside the pocket, allowing the in situ regeneration of the NADH models under irradiation. This new synthetic platform, which offers control over the location of the redox events, provides a regenerating system that exhibits high selectivity and efficiency and is extendable to benzoxazinone and quinoxalinone systems.     

Trace elements in surface sediments from Kongsfjorden,Svalbard: occurrence,sources and bioavailability

Concentration levels, potential sources and bioavailability of trace elements in marine sediments from Kongsfjorden (Svalbard Islands, Norwegian Arctic) were assessed and discussed. Surface sediments were collected by a Ponar grab and characterised in terms of mineralogical composition, grain-size distribution, total organic carbon and nitrogen percentage contents, and major and trace elements concentrations. Anthropogenic and natural sources of trace elements were inferred from lead isotope ratios, while the potential metal bioavailability was evaluated by size-fractionation and solid-phase speciation studies and by the analysis of acid-volatile sulphides (AVS) and simultaneously extracted metals (SEM). Concentrations of metals, their enrichment factors and solid speciation patterns collectively indicated that the anthropogenic impact of trace elements in the fjord is generally low, with a minor enrichment with respect to crustal values (by a factor of 2–11) for As, Cr, Ni and V. The lead isotope ratios (²⁰⁸Pb/²⁰⁷Pb: 2.474–2.498 and ²⁰⁶Pb/²⁰⁷Pb: 1.206–1.212) were close to the natural signature except in the outer fjord, due to the influence of the Atlantic marine circulation. Many elements of toxicological concern (e.g. Pb, V, Zn) were enriched in the finest sediment fraction, which was by far the preponderant one, especially in the inner fjord. However, less than 15% of most trace elements (exceptions Cd and Mn) in the finest fraction was actually associated with easily leachable sediment phases. Finally, the high SEM/AVS ratios determined on samples from sites close to the glacier fronts (11–15), due to low AVS content, highlighted that the sediment in that zone cannot remove additional inputs of heavy metals by sulphide precipitation.     

Sediment metal contamination in a creek flowing from a pristine to an industrial area of Trieste Province (Italy)

The following metals: Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined by inductively coupled plasma - atomic emission spectroscopy (ICP-AES) in fluvial sediments of Rosandra Creek, using two different, strong and mild sediment decomposition methods. The purpose was to obtain information about the contamination by metals and distribution paths of pollutants in the area crossed by Rosandra Creek: this little river is the unique epigeous watercourse in the Italian Karst and very few data can be found in literature. In this area, we can find a natural park, but also agricultural activities and an industrial district that was recently defined as "polluted site of national interest". By comparing the results of the strong and mild extraction we have obtained the percentage of extraction and enrichment factors for each metal in the different sediments of the sites R2 and R3 exposed to pollution, while the site R1 was considered as a pristine one because situated in the natural park. The computed enrichment factors are generally not very high, but copper, lead and zinc have factors that require attention. The principal component analysis (PCA) shows that the typically anthropogenic metals (as Cr, Pb, Cu and Zn) constitute the first factor, while the lithogenic metals, as Fe and Ni, constitute the second one; moreover the score plots permit to classify and distinguish the 3 sites: site R3, possibly the more exposed to contamination, has high scores both for anthropogenic and lithogenic metals.     

Renewable Molecular Flasks with NADH Models: Combination of Light-Driven Proton Reduction and Biomimetic Hydrogenation of Benzoxazinones

Using small molecules with defined pockets to catalyze chemical transformations resulted in attractive catalytic syntheses that echo the remarkable properties of enzymes. By modulating the active site of a nicotinamide adenine dinucleotide (NADH) model in a redox-active molecular flask, we combined biomimetic hydrogenation with in situ regeneration of the active site in a one-pot transformation using light as a clean energy source. This molecular flask facilitates the encapsulation of benzoxazinones for biomimetic hydrogenation of the substrates within the inner space of the flask using the active sites of the NADH models. The redox-active metal centers provide an active hydrogen source by light-driven proton reduction outside the pocket, allowing the in situ regeneration of the NADH models under irradiation. This new synthetic platform, which offers control over the location of the redox events, provides a regenerating system that exhibits high selectivity and efficiency and is extendable to benzoxazinone and quinoxalinone systems.     

Heterogeneity and lability of Pb(II) complexation by humic substances: practical interpretation tools

The complexation of Pb(II) by natural organic matter (NOM) is better described by taking into account the dependence of the strength of binding on metal loading conditions. The utility of a linear differential equilibrium function for interpretation of metal ion binding data is demonstrated. This approach considers the binding intensity (log K*) as a function of metal ion loading (ı = bound metal/binding site concentration). Three methods for calculating this function are presented: – direct calculation from metal titration curves, – direct calculation from polarograms, and – compilation of data derived from interpretation of complexation in terms of one- or two- binding sites (e.g. Scatchard analysis), i.e. Cc (complexation capacity = effective site concentration)–K pairs. Heterogeneity also impacts on the apparent lability of complexes; complexes formed at the lowest metal loadings are the least labile. Received: 28 December 2000 / Revised: 23 February 2001 / Accepted: 28 February 2001     

The Microstructure of Selective Palladium Hydrogenation Catalysts Supported on Calcium Carbonate and Modified by Lead (Lindlar Catalysts), Studied by Photoelectron Spectroscopy,Thermogravimetry, X-Ray Diffraction,and Electron Microscopy

A detailed analysis of the system Pd + Pb on CaCO₃ is presented. This system known as Lindlar catalyst is used for selective hydrogenations of C?C bonds to C?C bonds. It was found to consist of seven distinct chemical phases. Essential ingredients are solid solutions of hydrogen and oxygen in Pd. The latter phase enables the metal particles to be attached to the support via an orientational relationship calcite (113)∥Pd + O (111). The addition of Pb neither changes the micromorphology of the disk-shaped Pd particles nor does it modify the electronic structure of Pd as studied by chemisorption experiments. The addition of Pb seems to block certain active sites and, thus, to enhance the selectivity. The support was found to be a multi-domain mixture of calcite and aragonite with domain sites of several hundred Å. The free surface of the pore-free solid is covered by a calcium-hydroxide carbonate. This phase as well as several other Pb phases seem to represent only spectator materials. Verification of this as well as finding the correlation between structure and function of the various components requires a kinetic analysis which is outside the scope of this paper. It is demonstrated that a variety of analytical techniques is required to unravel the complex nature of such a ‘simple' catalyst’ as it is Pd on CaCO₃.     

Lead post-mortem intake in human bones of ancient populations by (109)Cd-based X-ray fluorescence and EDXRF

In this work we measured the lead concentration in human bones of Middle Age by means of a portable X-ray fluorescence system based on ¹⁰⁹Cd radioactive source. The detection system consists on a Ge hyperpure detector. This system, conceived for in vivo Pb analysis in bone, is portable, non-destructive and is based on lead K lines detection.

The analysed bones are part of two collections of bones both from the end of Middle Age and submitted for some years to a lead polluted burial environment. The bones of one collection were buried initially on the soil in a convent, in Lisbon (Portugal) and further on, kept in a lead coffin for around 100 years. The second collection contains bones buried permanently on the soil around an old church on the south of Portugal. This place became a parking car for around 20 years.

In this work we studied the distribution of Pb in cortical bone, and trabecular regions from the outside surface to the inner part of the bone and the results are compared with the obtained ones by energy dispersive X-ray fluorescence (EDXRF).

The obtained values present a strong contamination of Pb in spongy bones kept in the lead coffin with concentrations ranging from 250 to 350 μg Pb/g bone mineral, and 4 to 7 μg Pb/g bone mineral for bones buried in the soil. Good agreement was observed between the results obtained by the two techniques.     

Analysis of heavy metals in road-deposited sediments

Road-deposited sediments were analysed for heavy metal concentrations at three different landuses (residential, industrial, commercial) in Queensland State, Australia. The sediments were collected using a domestic vacuum cleaner which was proven to be highly efficient in collecting sub-micron particles. Five particle sizes were analysed separately for eight heavy metal elements (Zn, Fe, Pb, Cd, Cu, Cr, Al and Mn). At all sites, the maximum concentration of the heavy metals occurred in the 0.45-75 μm particle size range, which conventional street cleaning services do not remove efficiently. Multicriteria decision making methods (MCDM), PROMETHEE and GAIA, were employed in the data analysis. PROMETHEE, a non-parametric ranking analysis procedure, was used to rank the metal contents of the sediments sampled at each site. The most polluted site and particle size range were the industrial site and the 0.45-75 μm range, respectively. Although the industrial site displayed the highest metal concentrations, the highest heavy metal loading coincided with the highest sediment load, which occurred at the commercial site. GAIA, a special form of principal component analysis, was applied to determine correlations between the heavy metals and particle size ranges and also to assess possible correlation with total organic carbon (TOC). The GAIA-planes revealed that irrespective of the site, most of the heavy metals are adsorbed to sediments below 150 μm. A weak correlation was found between Zn, Mn and TOC at the commercial site. This could lead to higher bioavailability of these metals through complexation reactions with the organic species in the sediments.     

Use of Particle-Induced X-Ray Emission for Evaluation of Competitive Metal Binding on Algae

Elemental concentrations of a unicellular alga,Chlorella vulgaris,were evaluated by particle-induced X-ray emission (PIXE). The probed algal cells generated a significant amount of phosphorus and sulfur X-ray emission. Phosphorus- and sulfur-containing compounds can provide potential binding sites for metal ions. Competitive binding of six metal ions, Ag, Ba, Cd, Cu, Hg, and Pb, to the algae was studied. It was found that Ag, Ba, Cd, Cu, and Pb are attached to a similar binding site with a binding efficiency varying in the sequence Pb > Cu > Ag > Cd > Ba. The binding of Hg to algae involves a different binding site. Silver was found to increase the binding of mercuric chloride to the algae.     

Major and trace elements in sediments of the upper course of Lerma river

Summary The Lerma is one of the most important rivers of Mexico, where it drains highly populated and industrialized regions. The concentration of six major and trace elements: titanium, manganese, iron, zinc, copper and lead in the surface sediments of the upper course of Lerma river was investigated, in order to identify its distribution along the river and to recognize the principal sites of pollution. The surface sediment samples were collected at 8 sites distributed following the stream flow direction of the river. Major and trace elements concentrations were determined by energy dispersive X-ray spectrometry. The results show that the metal concentrations in the sediments decrease in the sequence: Fe > Ti > Mn > Zn > Cu > Pb. Concentration of Fe, Mn and Ti were significantly higher than the other metals in site 8,200 meters downstream the Alzate Dam. The high concentrations and spatial variations of Zn, Cu and Pb in the middle sites of the upper course of the Lerma River indicate that the river pollution is probably associated with urban and industrial discharges.     

Distribution of trace elements in flowing surface waters: Effect of seasons and anthropogenic practices in India

This study reports the distribution of Cr, Ni, Cu and Pb in waters, sediments, macrophytes and fish of the Yamuna River’s patch in Delhi (India). This is one of the most polluted stretches of rivers in the world. Water from this river is used fosr irrigation, industrial and domestic purposes, including drinking water. The effects of season and anthropogenic practices were identified. Almost zero dissolved oxygen and high levels of lead and phosphate indicate the polluted state of the aquatic system. The enrichment factors in sediments (with respect to reference site) vary in the range of 0.60–82.9% (Cr), 1.40–90.5% (Ni), 1.00–85.3% (Cu) and 3.80–86.6% (Pb). The toxic effects due to Ni and Pb could frequently be visible in aquatic life as their values fall above the probable effect level (36 mg Kg^?1 for Ni and 91.3 mg Kg^?1 for Pb). The metal contents in the macrophyte (Eichhornia crassipes) and the fish (Oreochromis niloticus) generally increase in the summer season. Cu and Pb accumulate preferentially in E. crassipes. The fish from these waters is unsuitable for human consumption as the levels of Cr, Cu and Pb are above the recommended limits. Significant spatial variations in parameters of water and sediments were confirmed via one-way analysis of variance. The Pearson’s correlation analysis suggests a common source of some of the metals. Principal component analysis highlighted domestic, and industrial waste and coal-fired thermal power plants as the metal sources. This study might act as a benchmark for other investigations focused on similarly affected surface aquatic systems due to agricultural and industrial activities.     

Wall-selective chemical alteration of silicon nanotube molecular carriers

Recently, there has been significant interest in the synthesis and potential applications of semiconductor nanotubes (NTs). In this context, many efforts have been invested in developing new routes to control and engineer their surface chemistry. We report herein on a simple route to differentially and selectively functionalize the inner and outer surfaces of silicon nanotubes (SiNTs) with organic molecular layers containing different functional groups and hydrophobicity/hydrophilicity chemical nature, via covalent binding, to give nanotubular structures with dual chemical properties. Significantly, our unique synthetic approach can be further extended to directly form hollow crystalline nanotubular structures with their inner/outer surfaces independently and selectively altered chemically. Additionally, SiNTs inner and/or outer walls can be selectively decorated with metal nanoparticles. Both inner and outer walls can be individually and separately modified with the same metal nanoparticles, with different metal NPs in the inside and outside walls or with a combination of metal NPs decoration and molecular layers, if so required. Furthermore, the dually modified nanotubes were then exploited as phase extraction nanocarriers to demonstrate their potential in future chemical and biological separation, extraction, and filtering applications.     

Tuning of redox properties of iron and iron oxides via encapsulation within carbon nanotubes

We report the tuning of the redox properties of iron and iron oxide nanoparticles by encapsulation within carbon nanotubes (CNTs) with varying inner diameters. Raman spectroscopy was employed to investigate the interaction of the encapsulated nanoparticles with the CNTs. A red shift of the Fe-O mode is observed in the nanoparticles deposited on the outer CNT surfaces with respect to bulk Fe2O3. However, this mode is found to be stepwise blue-shifted with decreasing inner diameter in the CNT-encapsulated Fe2O3 nanoparticles, suggesting an enhanced interaction of Fe2O3 with the inner CNT surface as its curvature increases. The autoreduction of the encapsulated Fe2O3 is significantly facilitated inside CNTs with respect to the outside nanoparticles. Interestingly, it becomes more facile with decreasing CNT channel diameter as evidenced by temperature programmed reaction, in situ XRD, and Raman spectroscopy. The oxidation of encapsulated metallic Fe nanoparticles on the other hand is retarded in comparison to that of the outside Fe particles as shown by in situ XRD and gravimetrical measurements with an online microbalance. We attribute this tunable redox behavior of transition metal nanoparticles inside CNTs to a particular electronic interaction of the encapsulates with the interior CNT surface, which stabilizes the metallic state of Fe.     

Determination of Heavy Metals in Bio-Collectors as Indicator of Environmental Pollution

The heavy metal levels in bio-collector ( Fabaceae Rabinia Pseudoacacia L. sprouts) samples collected from seven sites, which had the characteristic properties of the Sivas city, Turkey, in year 2000, have been determined by atomic absorption spectrometry (AAS), after the bio-collector sprouts were prepared for analysis by bio-collector-ultrasonic leaching method (BC-ULM). The results of the analyses were used to determine major sources and magnitude of heavy metal pollution. The mean concentration levels of Pb, Cu, Ni, Zn and Cd were found to be 6.8, 5.5, 6.7, 12.4 and 0.20 µg/g fresh bio-collector, respectively, for September 2000. The highest levels of the heavy metals at the sites affected by industrial emissions and heavy traffic were noted. The heavy metal levels in urban bio-collectors were several times higher than the background levels. After heavy metal pollution factors of each site were determined, their possible major pollutant sources were discussed.     

Complexation of lead(II) by chlorogenic acid: experimental and theoretical study

Density functional theory (DFT) structure calculations and time-dependent DFT electronic excitation calculations have been performed on chlorogenic acid (H(3)CGA), a polyphenolic compound, used as a model molecule of humic substances. The different deprotonated forms of H(3)CGA have also been investigated. H(3)CGA is a multisite ligand that presents several metal complexing sites in competition, notably the carboxylic and catechol moieties. In low acidic aqueous medium, the complexation of Pb(II) has been followed by electronic absorption spectrometry. The formation of two complexes of stoichiometry metal:ligand 1:1 (log beta(1:1) = 3.39) and 2:1 (log beta(2:1) = 7.12) has been highlighted with use of chemometric methods. The theoretical spectrum of the 1:1 complex obtained by TD-DFT methodology shows the formation of a chelate [Pb(H(2)CGA)(H(2)O)(3)](+) with the metal fixation at the level of the carboxylate function. The second complexing site, the catechol moiety, is rapidly involved in the formation of the 2:1 complex from molar ratios [metal]/[ligand] higher than 0.1. The electronic transitions calculated for both free ligand and complexes involved the same molecular orbitals, and no ligand-metal or metal-ligand charge transfer is observed.