Roberto Frache

Temporal distribution of trace metals in Antarctic coastal waters

Abstract In the framework of the Italian Research Programme in Antarctica, a nearshore station positioned inside the Gerlache Inlet (Terra Nova Bay, Western Ross Sea) was regularly sampled during the Austral Spring 1997/1998, from November to February. In order to evaluate the physical, chemical and biological variations along the water column, measurements of a large number of parameters were performed at a suitable frequency: temperature, salinity, fluorescence, suspended particulate matter, concentration of dissolved and particulate Fe, Cu and Mn, concentration of nutrients and phytoplankton pigments. Samples of pack ice and marine microlayer were also collected and analysed. Elaboration of data with regards to temporal and vertical components provided a good description of temporal distribution of trace metals in the coastal waters of Terra Nova Bay, in relation to the physical and biological processes. Concerning the surface layer, it was found that concentrations are mainly affected by the dynamic of the pack ice melting and phytoplankton activity. The first process influences both the input of metals from meltwaters and the covering of the seawater surface, allowing atmospheric dust input only when all ice has been melted or removed. Direct release from ice of particulate Fe and Cu were clearly shown by surface concentration peaks and by the high concentrations of suspended particulate matter and particulate metals detected in the ice core section interfaced with the seawater. Moreover, a quite complex dynamic dissolved/particulate partitioning was found, which can account for the temporal uncoupling between the maximum values of particulate and dissolved metals. In absence of pack ice, there is evidence of a further input of Fe and Mn due to atmospheric dust brought into the water column through the marine microlayer. This picture is complicated by phytoplankton activity, which removes micronutrients like Fe and Cu from water, incorporating them into organic particulate matter. The dynamic of metal uptake follows that of primary production which, in the studied area, shows a specific trend characterised by two distinct blooms: the first in the second half of December and the second in late summer. In intermediate and deep waters, the vertical distribution of Fe and Mn was characterised by a substantial constant profile until January; then, an increase of particulate metal concentration with depth was observed along with a corresponding decrease of the dissolved concentrations. This trend is typical of these scavenging-type elements which are removed by particulate matter during the sinking process, in the absence of well-defined water column stratification.

Trace metals distributions in coastal sea ice of Terra Nova Bay, Ross Sea, Antarctica

In an attempt to clarify the release of trace elements from the seasonal coastal sea ice, samples were periodically collected in a nearshore station inside the Gerlache Inlet (Terra Nova Bay, Western Ross Sea), during the summer 2000/01 and analysed for dissolved and particulate cadmium, copper, iron, manganese and lead, as well as salinity, suspended particulate matter, nutrients and phytoplankton pigments. In order to provide insight on the metal association with the particles included in the sea ice, the metal solid speciation was also investigated. Both vertical distributions within the ice cores and temporal variations at the seawater interface were studied, in an effort to fully characterize the system and correlation among the considered parameters. Concentrations and speciation patterns clearly indicate metal incorporation within the annual sea ice due to resuspension of sediments, followed by release of particulate metals during melting as a primary process affecting trace metal availability in the Antarctic coastal waters.

Determination of organotin compounds in marine mussel samples by using high-performance liquid chromatography–hydride generation inductively coupled plasma atomic emission spectrometry

HPLC–hydride generation-ICP-AES for the determination of organotin compounds is described. A detection limit of 7 ng for tin was obtained and the organotin species were completely separated within 7 min. The system has been used for the determination of organometallic compounds in marine mussel samples. Preliminary results obtained in laboratory experiments are presented.

Trace metals in sediments from the Ligurian Coast, Italy☆

Abstract The content of trace metals (Fe, Cd, Cu, Ni, Pb and Cr) in the Ligurian Coastal Area were acid leached and analysed by the atomic absorption method. In the stations in front of Genoa, with the maximum organic carbon content, Cr, Cu and Pb show a significant correlation between the leachable fraction with cold reagents and the organic carbon content of the sediment. Significant linear correlations of metals to total Fe were obtained for unpolluted sediments.

Determination of sub-nanomolar levels of iron in sea-water using reaction cell inductively coupled plasma mass spectrometry after Mg(OH)2 coprecipitation

A new procedure for the determination of iron in sea-water at sub-nanomolar concentration levels was developed. The method applied the low-blank magnesium hydroxide co-precipitation procedure in combination with quadrupole ICP-MS and used the dynamic reaction cell technique to resolve the polyatomic interferences arising from the residual matrix and the solvent. Although the interference-free determination at m/z = 56 could be obtained by using methane as the reaction gas, the best signal-to-background ratio was achieved by using ammonia and performing the measurements at m/z = 54. Accurate quantification of low levels of iron at m/z = 54 also required the mathematical correction for the isobaric interference due to the occurrence of chromium. The main analytical figures of the optimized method were evaluated, with special attention to the determination of the procedural, reagent and field blanks. A detection limit as low as 0.09 nM was achieved, using a pre-concentration ratio of 10. The accuracy of the analytical procedure was evaluated by the analysis of the sea-water reference materials CASS-4, NASS-5, SAFe D2 and SAFe S1, having certified concentration values ranging from 12.8 nM to about 0.1 nM. The analytical precision for replicated analyses of the CRMs ranged from 1.3% to 14% (n = 7). Finally, the developed procedure was applied to a number of open-ocean sea-water samples from the Ross Sea (Southern Ocean, Antarctica)

Determination of trace amounts of lanthanides in rocks and minerals by high-performance liquid chromatography

Abstract Rare-earth elements have been determined by a high-performance liquid Chromatographie procedure. The hydrochloric acid solution containing the rare-earth elements coming from the main separation of the whole group, contained in a rock sample and separated by a classical ion-exchange procedure, was eluted through a stainless-steel column packed with microparticulate silica, with bonded cation-exchange groups. Complete separation of individual lanthanides was achieved. A variable-wavelength detector was used following post-column complex formation with pyridylazoresorcinol. Results obtained on test solutions and on internal rock reference samples show good reproducibility and precision.

Effects of Ice Melting on Cu, Cd and Pb Profiles in Ross Sea Waters (Antarctica)

Abstract In the framework of the Italian Research Programme in Antarctica, evolution of dissolved and particulate Cu, Cd and Pb profiles in the coastal waters of Gerlache Inlet (Terra Nova Bay, Western Ross Sea) was studied during the Austral Summer 1997/98. In order to relate the distributions of trace metals with the physical and biological processes, a series of temperature and salinity measures were made, and water samples were collected to determine nutrients and chlorophyll. Samples of pack ice and marine microlayer (50–150 μm) were also collected and analysed. Concerning the surface layer, it was found that metal concentrations are mainly affected by the dynamic of the pack ice melting and phytoplankton activity. The first process influences both the input of metals from meltwaters and the covering of the seawater surface, allowing atmospheric dust input only when all ice has been melt or removed. Direct release of particulate Cu from ice was clearly shown by surface maxima and by the high concentrations of suspended particulate matter and particulate metals found in the ice core section interfaced with the seawater. Differently, the high amount of Cd in the particulate included in the pack ice seems not to affect the concentration in surface particulate; on the contrary, the corresponding increase of dissolved Cd indicates that it isreleased in dissolved form when the pack ice melts. Surface distribution is further complicated by the effect of phytoplankton activity, which removes Cu and Cd from water, incorporating them into organic particulate. Finally, in absence of pack ice, there is evidence of inputs of Pb and Cu due to atmospheric dust brought into the column water through marine microlayer. In intermediate and deep waters, the vertical distribution of Pb and Cd was characterised by substantially constant profiles, while Cu shown, during the end of the summer and in absence of a well-defined water column stratification, a “scavenging-type” distribution which overlaps its “nutrient-type” behaviour.

Ion-exchange separation and atomic-absorption determination of fifteen major, minor and trace elements in silicates.

A scheme of ion-exchange separation of fifteen elements (major, minor and trace) determined mainly by atomic-absorption spectrophotometry (Ti by colorimetry) is applied to rock, mineral and ceramic analysis. Mn, Cu, Co, Fe and Zn are separated on an anion-exchanger and Li, Na, K, Mg, Ca, Sr, Ti, Al, Ni and Ba on a cation-exchanger. The method has been tested by analysis of a synthetic mixture of the fifteen ions in the ratios in common rock samples, and of various international standards (100-mg samples).

Determination of Trace Metals in Antarctic Sediments from Terra Nova Bay - Ross Sea

Abstract Trace metals (Cu, Pb, Zn, Cd, Cr, Ni, Co, Mn) and iron concentration were determined in several sediments collected in the Antarctica (Terra Nova Bay—Ross Sea). Samples were analyzed by inductively coupled plasma (ICP-AES) after selective and total extraction. The results are in good agreement with the data previously collected in the same area.

Heavy Metals Distribution in Suspended Particulate Matter and Sediment Collected from Vlora Bay (Albania): A Methodological Approach for Metal Pollution Evaluation

Abstract Heavy metals (Al, Fe, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) content was evaluated in suspended particulate matter and sediment samples collected from Vlora Bay (Albania) in the framework of Centro Internazionale di Scienze del Mare (CISM) Project activities. The trend of the metals (in general, overlapping that showed by the suspended particulate matter distribution), together with the linear correlation values found between metals, suggested the pivotal role of the Vjosa River and of the inner circulation scheme of Vlora Bay on their distribution. The geoaccumulation index, Igeo, was calculated as a criterion to assess if a metal concentration found in the sediment represents contamination level or can be considered as background level. The results show that metals concentrations in sediments can be considered near the background levels found in the Mediterranean Sea, even if some accumulation was found in several stations. The data were compared to Sediment Quality Guidelines considering the ERL (effects range low) and ERM (effects range medium) values, to evaluate the potential effects of sediment-associated metals on aquatic organisms. The Ni value for all samples was above the ERM value, while Cr and As values were in between ERL and ERM. Metal speciation was also evaluated in some sediment samples. Generally, the metals found were associated with the refractory phases, which constitute up to 80% of the total concentration. Moreover, the sampling strategies and the adopted analytical methods were compared to those recommended by national and international regulations.