Major and trace element partitioning between dissolved and particulate phases in Antarctic surface snow.

In order to provide a new insight into the Antarctic snow chemistry, partitioning of major and trace elements between dissolved and particulate (i.e. insoluble particles, >0.45 µm) phases have been investigated in a number of coastal and inland snow samples, along with their total and acid-dissolvable (0.5% nitric acid) concentrations. Alkaline and alkaline-earth elements (Na, K, Ca, Mg, Sr) were mainly present in the dissolved phase, while Fe and Al were predominantly associated with the particulate matter, without any significant difference between inland and coastal samples. On the other hand, partitioning of trace elements depended on the sampling site position, showing a general decrease of the particulate fraction by moving from the coast to the plateau. Cd, Cu, Pb and Zn were for the most part in the dissolved phase, while Cr was mainly associated with the particulate fraction. Co, Mn and V were equally distributed between dissolved and particulate phases in the samples collected from the plateau and preferentially associated with the particulate in the coastal samples. The correlation between the elements and the inter-sample variability of their concentration significantly decreased for the plateau samples compared to the coastal ones, according to a change in the relative contribution of the metal sources and in good agreement with the estimated marine and crustal enrichment factors. In addition, samples from the plateau were characterised by higher enrichment factors of anthropogenic elements (Cd, Cr, Cu, Pb and Zn), compared to the coastal area. Finally, it was observed that the acid-dissolvable metal concentrations were generally lower than the total concentration values, showing that the acid treatment can dissolve only a given fraction of the metal associated with the particulate (<20% for iron and aluminium).

Summer distribution of trace metals in the western sector of the Ross Sea, Antarctica.

The more important water masses generated by the interaction of Circumpolar Deep Water and the shelf waters in the western sector of the Ross Sea are characterized for trace element contents. The distribution of cadmium, lead, copper, zinc, iron, manganese and chromium during the austral summer is analysed and discussed according to the physical, chemical and biological processes which affect the composition of the water masses. The Cd concentration is found to have a relative high variability that can be related to biological activity and the water mass age, MCDW presents a mean dissolved concentration (SD) of 0.77 (0.07) nmol kg(-1), while the HSSW and AASW have a mean concentration of 0.63 (0.06) and 0.61 (0.16) nmol kg(-1), respectively. Lead features the typical distribution of a scavenged element with a surface maximum ranging between 22 and 130 pmol kg(-1) decreasing to 11 pmol kg(-1) in deep waters. However, the vertical distribution in the shelf area features a maximum concentration in intermediate/deep waters and we can hypothesize that the distribution may be influenced by more than one source. The surface dissolved concentration of zinc and copper were un-homogeneously distributed, the mean (SD) values were 5.25 (2.92) and 1.99 (1.49) nmol kg(-1) for zinc and copper, respectively and increased with depth for both the elements. We may therefore hypothesize enrichment in the dissolved phase deriving from recycling in deep waters. 95% of the chromium was in dissolved form and showed a superficial depletion; the mean concentrations were 1.6 +/- 0.2 and 2.6 +/- 0.8 nmol kg(-1) for surface and deep waters respectively. The vertical distribution of dissolved manganese was quite homogeneous with a mean concentration 0.96 +/- 0.7 nmol kg(-1). The particulate iron and manganese concentration trends are similar and feature a significant bottom increase implying a significant input from resuspension; the mean concentration of particulate ranged between 1.4 and 7.4 nmol kg(-1) for iron and ranged between 0.072 and 0.29 nmol kg(-1) for manganese.

Trace metals speciation in coastal particulate matter for marine environmental studies in Antarctica.

Solid speciation of some trace metals (Pb, Cd, Fe, Mn, Cu) having environmental relevance was studied in coastal particulate sampled during the Austral Spring 2000/2001. A nearshore station situated in the Gerlache Inlet of Terra Nova Bay (Ross Sea, Antarctica) was sampled from November to February. Samples were collected using the in situ filtration system FIS500, equipped with polycarbonate membrane filters having different pore sizes (10 microm, 2 microm and 0.4 microm) for the size fraction analysis of particles. The total concentration of metals was determined both in dissolved and particulate fractions, while speciation was determined on particulate by applying a sequential extraction procedure. Concerning the surface and sub-surface layers, it has been observed that concentration of elements is mainly affected by the dynamic of the pack ice melting and by phytoplankton activity. The solid speciation in November and December is similar for all the studied elements, while some differences can be noted in February, when the pack has completely melted and phytoplankton bloom occurs. With the exception of iron, during this sampling period the quantity of metal associated to the labile fraction increases.

The utilization of the Antarctic environmental specimen bank (BCAA) in monitoring Cd and Hg in an Antarctic coastal area in Terra Nova Bay (Ross Sea--Northern Victoria Land).

The first projects relating to levels of Cd and Hg on marine biota and sediments from Terra Nova Bay (Ross Sea--Antarctica) and their bioaccumulation and biomagnification in this trophic web have been carried out by research programmes pertaining to the Italian Antarctic Research Program (PNRA) since 1989. Making use of this data, and checking the same metals after 10 years thanks to the samples stored in the BCAA, we have looked for the levels of Cd and Hg in a coastal marine ecosystem of Terra Nova Bay, and have proposed using some organisms to monitor the levels of these two heavy metals in this environment where the Italian Base is located, using the data determinate in this work as background levels. In our work, the amount of Hg and Cd concentrations have been determined in biota from the inner shelf of Terra Nova Bay (Adamussium colbecki, Laternula elliptica, Odontaster validus, Sterechinus neumayeri, Trematomus bernacchii, Iridaea cordata, Phyllophora antarctica, Parborlasia corrugatus), and in two different size fractions of sieved marine sediments (<2000 microm and <63 microm). To widen the distribution of Cd and Hg in this ecosystem we have also investigated the fraction of these metals bound to the labile phase of the marine sediments, and their presence in the particulate matter found in pack-ice cores, recent snow, water column and sea microlayer.

Benthic fluxes of cadmium, lead, copper and nitrogen species in the northern Adriatic Sea in front of the River Po outflow, Italy.

Trace heavy metal (Cd, Pb and Cu) and nitrogen species (N-NO3, N-NO2 and N-NH4) fluxes between sediment and water were examined for approximately 4 days, in a coastal marine station located in the northern Adriatic Sea in front of the River Po outflow. An in situ benthic chamber, equipped with electronic devices for monitoring and adjustment of oxygen and pH and with a temperature detector, was used. The benthic chamber experiment enabled study of the temporal trend of metals and nutrients when oxygen concentration varied in a controlled environment. Although particular care was devoted to chamber deposition and parameter control, sediment resuspension occurred at the beginning of the experiment and O2 fluctuations were observed during the course of the experiment. Pb concentration was affected by both resuspension and oxic conditions in bottom water, which prevented determination of any reasonable Pb flux value. Cd and Cu, not influenced by oxygen fluctuations, reached an equilibrium phase in a short period with initial positive fluxes from sediment of 0.68 (S.D. = 0.07) and 6.9 (S.D. = 5.6) pmol cm(-2) h(-1), respectively. With regard to nitrogen species, the highest positive flux was that of N-NH4 (10.5, S.D. = 2.4, nmol cm(-2) h(-1)) whose concentration increased in the chamber, while nitrate concentration (initial flux of -5.7, S.D. = 1.5, nmol cm(-2) h(-1)) immediately decreased after the beginning of the experiment. Nitrite concentration was almost constant throughout the experiment and its flux was generally low (initial flux 0.1, S.D. = 0.9, nmol cm(-2) h(-1)).