Carlo Papucci

The physical environment of Kongsfjorden–Krossfjorden, an Arctic fjord system in Svalbard

Kongsfjorden-Krossfjorden and the adjacent West Spitsbergen Shelf meet at the common mouth of the two fjord arms. This paper presents our most up-to-date information about the physical environment of this fjord system and identifies important gaps in knowledge. Particular attention is given to the steep physical gradients along the main fjord axis, as well as to seasonal environmental changes. Physical processes on different scales control the large-scale circulation and small-scale (irreversible) mixing of water and its constituents. It is shown that, in addition to the tide, run-off (glacier ablation, snowmelt, summer rainfall and ice calving) and local winds are the main driving forces acting on the upper water masses in the fjord system. The tide is dominated by the semi-diurnal component and the freshwater supply shows a marked seasonal variation pattern and also varies interannually. The wind conditions are characterized by prevailing katabatic winds, which at times are strengthened by the geostrophic wind field over Svalbard. Rotational dynamics have a considerable influence on the circulation patterns within the fjord system and give rise to a strong interaction between the fjord arms. Such dynamics are also the main reason why variations in the shelf water density field, caused by remote forces (tide and coastal winds), propagate as a Kelvin wave into the fjord system. This exchange affects mainly the intermediate and deep water, which is also affected by vertical convection processes driven by cooling of the surface and brine release during ice formation in the inner reaches of the fjord arms. Further aspects covered by this paper include the geological and geomorphological characteristics of the Kongsfjorden area, climate and meteorology, the influence of glaciers, freshwater supply, sea ice conditions, sedimentation processes as well as underwater radiation conditions. The fjord system is assumed to be vulnerable to possible climate changes, and thus is very suitable as a site for the demonstration and investigation of phenomena related to climate change.

Vertical and horizontal fluxes of plutonium and americium in the western mediterranean and the Strait of Gibraltar

New data on the vertical distributions of plutonium and americium in the waters of the western Mediterranean and the Strait of Gibraltar are examined in terms of the processes governing their delivery to, transport in and removal from the water column within the basin. Residence times for plutonium and americium in surface waters of approximately 15 and approximately 3 years, respectively, are deduced, and it is shown that by the mid 1990s only approximately 35% of the 239,240Pu and approximately 5% of the 241Am deposited as weapons fallout still resided in the water column. Present 239,240Pu inventories in the water column and the underlying sediments are estimated to be approximately 25 TBq and approximately 40 TBq, respectively, which reconcile well with the time-integrated fallout deposition in this zone, taken to be approximately 69 TBq. The data show that there are significant net outward fluxes of plutonium and americium from the basin through the Strait of Gibraltar at the present time. These appear to be compensated by net inward fluxes of similar magnitude through the Strait of Sicily. Thus, the time-integrated fallout deposition in the western basin can be accounted for satisfactorily in terms of present water column and sediment inventories. Enhanced scavenging on the continental shelves, as evidenced by the appreciably higher transuranic concentrations in shelf sediments, supports this contention.

Mosses as indicators of radioactivity deposition around a coal-fired power station

The concentration of 210Pbex has been measured in mosses (Hypnum cupressiforme) collected over a wide area around a coal-fired power station located in La Spezia, Central Italy, in order to evaluate the possible increase of natural radioactivity levels due to the operation of the plant. The concentration of 210Pbex varies between 258±39 and 1898±385 Bq m−2. The 210Pbex distribution pattern has been analysed in relation to the structure of the moss carpet (thickness, density) and compared to that of 137Cs. The close correlation between the distribution of 210Pb and 137Cs indicates that the patchiness of the observed distribution is mainly related to the general meteorological conditions and to the health and structure of the organisms. The operation of the power plant did not result in preferential deposition of 210Pbex at particular sites in the study area.

137Caesium distribution in the eastern Mediterranean Sea: recent changes and future trends.

A series of sampling campaigns were carried out in the eastern Mediterranean in the period 1995-1997, to examine the relationship between the distribution of 137Cs in the water column and water mass circulation. 137Cs concentration in the surface water ranges between 3.3 and 4.0 mBq/l all over the area, indicating that the input due to the Chernobyl accident has been transferred to deep water layers by convection processes. In fact, in the vertical profiles, relative maxima are observed in the intermediate (4 mBq/l) and deep waters (approximately 2.5 mBq/l) formed after the Chernobyl accident. A clear Chernobyl signal also traces the new deep waters formed in the Aegean Sea that, exiting from the Cretan Arc Straits, since 1991 are spreading in the bottom layer of the eastern Mediterranean. The changes in 137Cs vertical profiles related to the new thermohaline circulation of the intermediate and deep waters of the eastern Mediterranean are being monitored at a deep station in the western Ionian Sea. The 1997 profile shows a decrease in 137Cs concentration both in the Levantine intermediate water and in the eastern Mediterranean deep water with respect to 1996. The decrease in Levantine intermediate water is likely due to seasonal/interannual variability, while the changes in the deep layer are related to the spreading westward into the Ionian of the new Aegean dense water. Along the path towards the western Mediterranean, 137Cs content in the Levantine intermediate water decreases from approximately 4 mBq/l in the W-Ionian Sea to approximately 2 mBq/l at the western sill of the Sicily Straits, due to mixing with underlying water, with lower caesium content, near the Malta Sill. Time-series measurements at the western sill of the Sicily Straits show that, while 137Cs concentration in the surface water entering the eastern Mediterranean remained constant (approximately 3.5 mBq/l) in the period 1993-1997, its level in the Levantine intermediate water leaving the basin decreased from 3.5 to 2.0 mBq/l.

Plutonium concentration in sediment cores collected in the Mediterranean Sea

As is well known, the determination of plutonium isotopes in the marine environment is of great importance to calculate the contamination due to the nuclear industry and to better understand sedimentation processes. In the last 20 years sea sediment cores have been collected in different areas of the Mediterranean Sea by four Italian research teams. The sampling depth ranged from 50 to 2800 m and the core lengths were 10–30 cm. The radioanalytical procedures were based on plutonium separation by anion exchange resins or by extraction chromatography with Microthene-TOPO; plutonium electroplating was performed before α-spectrometry. The final chemical yields were determined by spiking with 236Pu or 242Pu. In some cases 238Pu could be detected. As far as the vertical profiles are concerned, no significant subsurface maxima resulted for the cores collected at greatest depth; on the contrary interesting peaks were found for cores collected at 50–100 m depth.

The role of the rivers in Chernobyl radiocesium delivery, distribution and accumulation in coastal sediments of the Northern Adriatic Sea

Abstract The fate of radiocesium transported by rivers to the Adriatic Sea and accumulated in sediments was investigated in the Northern Adriatic coastal area. Concentrations and inventories obtained for the areas of influence of the most important rivers (Tagliamento, Isonzo, Piave, Adige and Po) were compared. Radiocesium preferentially accumulates in the prodelta areas. In 1987 137 Cs maximum concentrations and inventories in these zones ranged between 200 and 300 Bq kg −1 and between 12 and 64 kBq m −2 , respectively. The temporal dynamics in selected zones was studied by sampling at the same site in different years. Temporal differences in the radionuclide inventories show that some areas are unstable on the time scale of one year due to sediment resuspension processes.

Gas Exchange at the Air-Sea Interface: A Technique for Radon Measurements in Seawater

The rate of exchange of various gas species, such as O2, CO2 etc. across the air-water interface can be evaluated from the 222Rn vertical profiles in the water column.

Vertical Distribution and Inventories of 239,240Pu in Deep Sea Sediments of the Mediterranean Sea (Algerian Basin, Ionian Sea)

Abstract Deep-sea sediments collected in two areas of the Mediterranean Sea having different sedimentological characteristics have been analyzed to determine present concentrations and inventories of 239,240Pu and to study the main mechanisms controlling them. Plutonium distribution in the deepest part of a submarine canyon (Taranto Valley, Ionian Sea) is compared to that obtained in an abyssal plain (north Algerian Plain). in the latter case, sedimentation is mainly due to the sinking of biogenic particles, while in the former lateral transport of terrigenous material along the slope of the canyon can significantly contribute to sediment accumulation on the bottom. 239,240Pu surface concentration in the canyon ranged from 0.2 to 1 Bq kg−1 (dry weight) and this was lower in the abyssal plain. in this area, plutonium was detectable only in the first 4 cm, while in the canyon it was present down to 11–15 cm. 239,240Pu inventories are 3 Bq m−2 in the plain and 45–60 Bq m−2 in the canyon, indicating considera...