Gabriele Capodaglio

Lead speciation in surface waters of the eastern North Pacific

Abstract Titrations using differential pulse anodic stripping voltammetry (DPASV) to detect electroactive lead were carried out on fresh seawater samples and on samples stored acidified to determine the extent of lead complexation in the eastern North Pacific. Results of these analyses on surface water samples indicate total dissolved lead concentrations between 17 and 49 pM. The inorganic or DPASV labile fraction is 30–50%. Titration with lead yielded data consistent with one class of organic ligand(s), present at low concentration (between 0.2 and 0.5 nM) with a mean value for a conditional stability constant with respect to inorganic lead of log K ′ cond =9.7. The presence of this ligand, together with the various inorganic ligands in seawater, gives rise to a concentration of free ionic lead of ∼ 0.4 pM.

Sampling sea surfaces with SESAMO: an autonomous craft for the study of sea-air interactions

This paper presents the system design, sea trials and Antartic exploitation of the SESAMO platform. The SESAMO (sea surface autonomous modular unit) prototype robot was especially designed to collect data and samples for the study of the sea-air interface. At sea, operations showed that a relatively simple robot could satisfactorily work in a natural, outdoor environment, dramatically facilitating the job of the human operator. To achieve high quality sampling of the surface microlayer, however, requires a large amount of time, leading to significant demands on logistics resources, mainly in terms of operating time of the support vessel.

Determination of Rh, Pd, and Pt in polar and Alpine snow and ice by double-focusing ICPMS with microconcentric nebulization

The performance of a double-focusing inductively coupled plasma mass spectrometer equipped with a microconcentric nebulizer was investigated for the direct simultaneous determination of Rh, Pd, and Pt in less than 1 mL of melted snow and ice samples originating from remote sites. Ultraclean procedures were adopted in the laboratories and during the pretreatment steps, to avoid possible contamination problems. Spectroscopic and nonspectroscopic interferences affecting the determination of Rh, Pd, and Pt were carefully considered. Detection limits of 0.02, 0.08, and 0.008 pg g(-)(1) for Rh, Pd, and Pt, respectively, were obtained using the following isotopes:  (103)Rh, (106)Pd, and (195)Pt. Repeatability of measurements, as RSD, was 27, 28, and 29%, for Rh, Pd, and Pt, respectively. The new method was applied to the analysis of samples coming from Greenland, Antarctica, and the Alps in order to assess the past natural background concentrations and to determine the present level of these polluting substances. The extremely low detection limits allowed the direct analysis of all samples except for two Greenland ice core sections dating from 7260 and 7760 years ago for which a preconcentration step was necessary. Concentration ranges for all snow samples were (in pg g(-)(1)) as follows:  Rh (0.0005-0.39), Pd (0.01-16.9), and Pt (0.008-2.7). The lowest concentrations were measured in the enriched Greenland ancient ice samples.

Trace element determination in alpine snow and ice by double focusing inductively coupled plasma mass spectrometry with microconcentric nebulization

Double focusing inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the direct, simultaneous determination of Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, Ag, Cd, Sb, Ba, Au, Pb, Bi and U in recent Alpine snow and old ice at the ng g –1 and pg g –1 level. Small amounts of sample (about 1 ml) were analysed using a microconcentric nebulizer. To avoid possible spectral interferences, measurements were carried out both in medium (m/Δm≈3400) and low (m/Δm≈300) resolution modes. Clean procedures were adopted both in the field and in the laboratory in order to reduce the possibility of sample contamination to a minimum. Concentration ranges of Alpine surface snow were (in pg g –1 ): Ti (8-106×10 3 ), V (3-4601), Cr (3-2985), Mn (1-173×10 3 ), Fe (67-1058×10 3 ), Co (2-973), Cu (8-29.1×10 3 ), Zn (2-6311), Mo (11-721), Ag (0.5-107), Cd (16-218), Sb (1.7-6173), Ba (9-36.5×10 3 ), Pb (23-33.7×10 3 ), Bi (0.1-116) and U (0.1-265). Much lower concentrations were detected in high altitude sites in the Alps. Measurement repeatability, in terms of RSD, ranged between 9 and 34%, depending on the element. The reliability of the analytical method was confirmed by analysis of a certified reference material (SLRS-3, riverine water) and by determination of Cd, Pb, Cu and Zn by ETAAS. For some of the elements investigated these results constitute the first available for recent Alpine snow and old ice.

Atmospheric iron fluxes over the last deglaciation : Climatic implications

A decrease in the micronutrient iron supply to the Southern Ocean is widely believed to be involved in the atmospheric CO2 increase during the last deglaciation. Here we report the first record of atmospheric iron fluxes as determined in 166 samples of the Dome C ice core and covering the last glacial-interglacial transition (22–9 kyr B.P.). It reveals a decrease in fallout flux from 24 × 10−2 mg Fe m−2 yr−1 during the Last Glacial Maximum to 0.7 × 10−2 mg Fe m−2 yr−1 at the onset of the Holocene. The acid leachable fraction of iron determined in our samples was the 60% of the total iron mass in glacial samples, about twice the value found for Holocene samples. This emerging difference in iron solubility over different climatic stages provides a new insight for evaluating the iron hypothesis over glacial/interglacial periods.

Speciation analysis of mercury in seawater from the lagoon of Venice by on-line pre-concentration HPLC-ICP-MS

A method based on the coupling of HPLC with ICP-MS with an on-line pre-concentration micro-column has been developed for the analysis of inorganic and methyl mercury in the dissolved phase of natural waters. This method allows the rapid pre-concentration and matrix removal of interferences in complex matrices such as seawater with minimal sampling handling. Detection limits of 0.07 ng L(-1) for inorganic mercury and 0.02 ng L(-1) for methyl mercury have been achieved allowing the determination of inorganic mercury and methyl mercury in filtered seawater from the Venice lagoon. Good accuracy and reproducibility was demonstrated by the repeat analysis of the certified reference material BCR-579 coastal seawater. The developed HPLC separation was shown to be also suitable for the determination of methyl mercury in extracts of the particulate phase.

Speciation of trace metals in seawater by anodic stripping voltammetry : critical analytical steps

The speciation of trace metals in seawater based on the voltammetric (DPASV) titration of ligands by metal addition is considered. The method allows the determination of the total metal amount, the “labile” fraction, the ligand concentration and the related conditional stability constant. Analytical problems related to sample contaminations during sampling, filtration and storage, displacement of complexing equilibria in freeze storage, the kinetics of the reaction of complexation and the potential kinetic lability of organic complexes are discussed and possible solutions presented. Data on quality control tests carried out to verify the accuracy of the laboratory procedure for trace metal determination in seawater are reported.

A TWO HUNDRED YEARS RECORD OF ATMOSPHERIC CADMIUM, COPPER, AND ZINC CONCENTRATIONS IN HIGH ALTITUDE SNOW AND ICE FROM THE FRENCH-ITALIAN ALPS

Cd, Cu and Zn have been measured using ultraclean procedures in snow and ice deposited at a high altitude location in the French/Italian Alps during the past two centuries. These data provide the first time series of changes in the occurrence of heavy metals in ice and snow from temperate regions since the Industrial Revolution. Concentrations are constant until the end of the nineteenth century. Then they increase by 10, 15 and 30 fold for Cu, Cd and Zn, respectively till the 1970s. During the following two decades Cd and Zn concentrations then decrease whilst Cu continues to increase. These temporal changes are compared with changes in emissions in Western Europe.

Recent decrease in the lead concentration of Antarctic snow

Differential Pulse Anodic Stripping Voltammetry (DPASV) was applied to determine the lead concentration in recent snow at two sites in the Victoria Land region, East Antarctica. Snow samples were collected during the 6th Italian Scientific Expedition to Antarctica (austral Summer 1990-91) along the wall of 2.5 m-deep hand-dug pits and by coring to a depth of about 1 m. The measurements revealed that lead content in Antarctic snow increased continuously from 1965 (about 3 pg/ g) to the early 1980s (maximum about 8 pg/g), after which a marked, rapid decrease took place during the second half of 1980s, down to 2-4 pg/g in 1991. Estimates of the lead contributions from rocks and soils, volcanoes and the marine environment, together with analysis of statistical data on non-ferrous metal production and gasoline consumption, and the corresponding lead emissions into the atmosphere of the Southern Hemisphere, show that a net anthropogenic component is present and support the hypothesis that the trend observed in Antarctic snow may be related to lead consumption in gasoline, which firstly was on the rise, then declined owing to the increased use of unleaded gasoline.

Determination of antimony in seawater by cathodic stripping voltammetry

Abstract The method proposes to determine subnanomolar levels of antimony in freshwater and seawater by cathodic stripping voltammetry preceded by adsorptive deposition of complexes with catechol. Dc-polarographic and cyclic voltammetric experiments indicated that the complex of catechol with Sb(III) is adsorbed prior to the scan, and is reduced to Sb(0) in a single reduction step. The optimized analytical conditions include a catechol concentration of 0.002 M and pH 6. The deposition potential is selected at -1.0 V. rather than at a more positive potential, in order to eliminate interference by uranium in seawater by including an amalgamation step in the preconcentration procedure. This is followed by a re-oxidation period of 20 s at −0.2 V to allow amalgamated Sb to become re-oxidized and form an adsorbed layer of Sb(III)-catechol complexes. The scan is then initiated in a negative direction using a linear sweep of 50 mV/s. The limit of detection lies near 0.2 n M Sb with a deposition time of 3 min, whereas the sensitivity can be increased by extending the deposition time. Interference by copper, lead and cadmium is eliminated by adding EDTA to the solution. Both Sb(III) and Sb(V) can be determined with identical sensitivity.