Clara Turetta

Changes in natural lead, copper, zinc and cadmium concentrations in central Greenland ice from 8250 to 149,100 years ago: their association with climatic changes and resultant variations of dominant source contributions

Abstract We present here the first reliable time series of Pb, Cu, Zn and Cd in Greenland ice for the last climatic cycle. They were obtained by analysing various sections of the 3028.8 m GRIP deep ice core drilled at Summit, central Greenland. Our results show that climatic changes have led to large variations in the concentrations of natural Pb, Cu, Zn and Cd in the high-latitude troposphere of the Northern Hemisphere. Between the interglacial and glacial periods, concentrations have varied by factors of ∼ 320 for Pb, 100 for Cu, 36 for Zn and 13 for Cd. Based on a good correlation between each heavy metal and Al, Pb and Cu are found to have mainly originated from soil and rock dust for both glacial and interglacial periods. On the other hand, continental biogenic emissions were the main source of Cd and to a lesser extent Zn in the Arctic troposphere during the warm Eemian and the Pre-Boreal to Holocene transition, whereas wind-blown dust was the predominant source for these two metals during the cold glacial climatic stages. This characteristic change of relative Cd and Zn contributions from different sources in contrast to that for Pb and Cu is well documented in the ice from the last deglaciation period (15,000 to 8250 yrs ago). After the Younger Dryas event ended, a remarkable increase of Cd Al and Zn Al ratios occurred from 13,000 to 9300 yrs ago, which is consistent with the progressive expansion of vegetation following the retreat of the North American and North Eurasian ice sheets. The subsequent decrease of these ratios to Holocene values can be explained by the stabilization of atmospheric circulation in the northern high-latitude regions, which became similar to that for the Holocene due to further reduction of the Laurentide ice sheet. Finally, the observed variations of the metal/Al ratios suggest changes in the soil and rock dust source regions in parallel with climatic changes which have altered the mean composition of the crustal particles transported to the Arctic.

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.

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.

Speciation analysis of selenoproteins in human serum by solid-phase extraction and affinity HPLC hyphenated to ICP-quadrupole MS

Anion exchange-solid-phase extraction carried out prior to double column affinity-high performance liquid chromatography (AF-HPLC) coupled on-line with conventional inductively coupled plasma-(quadrupole) mass spectrometry is proposed for simultaneous speciation analysis of selenoprotein P (SelP), glutathione peroxidase (GPx) and selenoalbumin (SeAlb) in human serum. Efficient interference-free AF-HPLC separation of GPx, SelP and SeAlb is obtained within a total chromatographic run time less than 15 min. The repeatability in terms of relative standard deviation (R.S.D., %, n = 10) is 7% for GPx and SelP and 4% for SeAlb. The detection limits are 0.1 ng mL−1 for GPx, 1.0 ng mL−1 for SelP and 1.3 ng mL−1 for SeAlb. The method was validated by the analysis of two human serum reference materials certified for total Se content.

Cadmium, Lead and Copper Complexation in Antarctic Coastal Seawater. Evolution during the Austral Summer

Abstract The evolution of cadmium, lead and copper complexation by organic ligands was studied along the water column during the 1990/91 summer in the Gerlache Inlet (Antarctica). The complexation was estimated by determination of the total dissolved concentration of metals, the labile concentration, the ligand concentrations and the relative conditional stability constants. The mean value of the total dissolved cadmium concentration was 0.83 nM until mid-December; the concentration was gradually depleted initially in the subsurface layer then down to the bottom. The mean concentration along the water column in February was 0.15 nM. The labile fraction represented 90% of the total until December, and it was reduced to about 20% in the upper 50 m by February. The cadmium was complexed by one class of ligands detectable after mid-December. Initially it was present only in the surface layers and later was extended to the bottom. The ligand concentration reached a maximum (2.2 nM) during the phytoplankton blo...

Evolution of cadmium and lead contents in Antarctic coastal seawater during the austral summer.

Abstract The seasonal evolution of the cadmium and lead distribution in the water column of the Gerlache Inlet (Ross Sea) was studied during the 1990–91 austral summer. Measurements were carried out by Anodic Stripping Voltammetry in Antarctica immediately after the collection and filtration of samples. The concentrations of both metals were homogeneous before the phytoplankton bloom with mean values of 0.71 (SD 0.10) and 0.116 (SD 0.014) nmol/1 for cadmium and lead respectively. A subsequent depletion in metal concentration was observed in the shallow waters. The surface concentration of cadmium decreased to about 0.1 nmol/1 at the end of the season. The vertical distribution of lead was less affected by the seasonal evolution and the mean surface concentration decreased to 0.044 nmol/1 in the same period. The results are evaluated with respect to physical and biological processes in the area examined and compared with those obtained on previous expeditions in the same area.

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.

Glacial-interglacial changes in the occurrence of Pb, Cd, Cu and Zn in Vostok Antarctic ice from 240 000 to 410 000 years BP.

Lead (Pb), cadmium (Cd), copper (Cu) and zinc (Zn) have been measured by electrothermal atomic absorption spectrometry in various sections of the 3623 m deep ice core drilled at Vostok, in central East Antarctica. The sections were dated from 240 to 410 kyear BP (Marine Isotopic Stages (MIS) 7.5 to 11.3), which corresponds to the 3rd and 4th glacial-interglacial cycles before present. Concentrations are found to have varied greatly during this 170 kyear time period, with high concentration values during the coldest climatic stages such as MIS 8.4 and 10.2 and much lower concentration values during warmer periods, such as the interglacials MIS 7.5, 9.3 and 11.3. Rock and soil dust were the dominant sources for Pb, whatever the period, and for Zn and Cu and possibly Cd during cold climatic stages. The contribution from volcanic emissions was important for Cd during all periods and might have been significant for Cu and Zn during warm periods.

Response to metal stress of Nicotiana langsdorffii plants wild-type and transgenic for the rat glucocorticoid receptor gene

Recently our findings have shown that the integration of the gene coding for the rat gluco-corticoid receptor (GR receptor) in Nicotiana langsdorffii plants induced morphophysiological effects in transgenic plants through the modification of their hormonal pattern. Phytohormones play a key role in plant responses to many different biotic and abiotic stresses since a modified hormonal profile up-regulates the activation of secondary metabolites involved in the response to stress. In this work transgenic GR plants and isogenic wild type genotypes were exposed to metal stress by treating them with 30ppm cadmium(II) or 50ppm chromium(VI). Hormonal patterns along with changes in key response related metabolites were then monitored and compared. Heavy metal up-take was found to be lower in the GR plants. The transgenic plants exhibited higher values of S-abscisic acid (S-ABA) and 3-indole acetic acid (IAA), salicylic acid and total polyphenols, chlorogenic acid and antiradical activity, compared to the untransformed wild type plants. Both Cd and Cr treatments led to an increase in hormone concentrations and secondary metabolites only in wild type plants. Analysis of the results suggests that the stress responses due to changes in the plants hormonal system may derive from the interaction between the GR receptor and phytosteroids, which are known to play a key role in plant physiology and development.

Analytical quality control : Sampling procedures to detect trace metals in environmental matrices

The problem of contamination during the collection of samples of environmental interest to detect trace metal is discussed. Attention is focused on the leaching of metals from sampling devices used to collect surface and deep seawater. A procedure to test metal release is applied to emphasize the importance of conditioning samplers before use. The procedure for checking the contamination extent and decontamination of firn and ice cores to detect ultratrace elements (particularly Cd and Pb) is presented and applied to some firn cores collected in Antarctica during the 1990–1991 Italian expedition.