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Plutonium isotopes and 241Am were studied in seawater and sediment from the East China Sea, the Yellow Sea, the East Sea/Sea of Japan, the Sea of Okhotsk, and the northwest Pacific Ocean, collected between 1993 and 1996 with the aim to contribute to better understanding the behaviour of plutonium and americium in the marine environment. 239,240Pu concentrations in surface water varied from 2.3 to 13 μBq l−1 in the East China Sea and from 3.5 to 9.4 μBq l−1 in the East Sea. The 239,240Pu vertical profiles in water showed a broad subsurface maximum between 500 and 1000 m with a range of 30–40 μBq l−1, and gradually decreased from 1000 m depth down to the seafloor. 241Am concentrations in surface water showed values from 1.1 to 2.2 μBq l−1 in the East Sea, from 1.0 to 3.1 μBq l−1 in the Sea of Okhotsk, and from 0.68 to 12.0 μBq l−1 in the northwest Pacific Ocean. The activity ratios of 241Am/239,240Pu in seawater showed values similar to the global fallout ratio, which suggests that the source of these radionuclides in the northwest Pacific Ocean is global fallout. However, the 241Am/239,240Pu activity ratios in sediment were found to be much higher (1.0–1.9) than the global fallout ratio (0.37), confirming that 241Am is scavenged from the water column more rapidly than 239,240Pu. The 239,240Pu inventories in the water column of the East Sea were from 0.98 to 93 Bq m−2 depending on water depth and sedimentation rates. The 241Am inventory in the water column east of Kamchatka was 6.3±1.0 Bq m−2 and the sediment inventory in the Sea of Okhotsk was 16±2 Bq m−2. 239,240Pu concentrations in sinking particles in the southwest Japan Basin were from 3.7 to 5.2 Bq kg−1 (dry weight) with fluxes of 0.19–4.50 mBq m−2 d−1 and at the Ulleung Basin from 2.4 to 3.7 Bq kg−1 (dry weight) with fluxes of 0.77–1.10 mBq m−2 d−1. The mean residence time of 239,240Pu in the water column of the East Sea derived from sediment trap data was 140±20 years, 2–3 times less than in the Atlantic and Pacific oceans. [Copyright &y& Elsevier]

Two sampling expeditions were carried out in the Caspian Sea in 1995 and 1996. The aim was to investigate oceanographic conditions, water dynamics of the Sea and to measure radionuclide concentrations using 90Sr, 137Cs and 239,240Pu as tracers in the water column. Of the three basins comprising the Caspian Sea, the two deep basins (the central and southern basins) appear to be rapidly ventilated on a time scale of about 30 years, as shown by the penetration of radionuclides to bottom waters. The main source of radionuclides in the Sea has been global fallout and subsequent river run-off from catchment areas. At the stations visited, there were no signs of radioactive waste dumping, although the 90Sr levels found were higher than expected from global fallout, which may be due to remobilization of 90Sr from soil and its transport by rivers to the Sea. Radionuclide concentrations in fish and caviar are within the expected ranges and are not of radiological importance for consumption of fish and caviar from the Caspian Sea. [Copyright &y& Elsevier]

Results of the analyses of 3H, 90Sr, 137Cs, 239,240Pu and 241Am in surface-water samples collected during the 1998 Indian Ocean Transect cruise from New Zealand to Italy are reported and discussed. Latitudinal variations in the concentrations of these radionuclides still can be seen over 40 yr after the main input, but the observed distribution no longer corresponds to the atmospheric deposition in the study area. Low levels of conservative radionuclides characterise the Tasman Sea and the South Australian Basin. At about 30°S the concentrations increase and remain very similar until about 10°N. A slight decrease is observed in the Gulf of Aden and in the Red Sea. The distribution of transuranic elements shows marked differences with respect to that of conservative radionuclides, particularly in the Tasman Sea and in the south-eastern Indian Ocean. The observed latitudinal trend is mainly dependent on the surface oceanic circulation for conservative radionuclides, while for the non-conservative transuranic elements it is also related to primary productivity and enhanced scavenging.For all investigated radionuclides, the Mediterranean is the area with the highest concentrations. The observed radionuclide concentrations in addition to 137Cs/3H, 90Sr/3H, 137Cs/90Sr, and 241Am/239,240Pu activity ratios confirm the global origin of the radionuclides studied in surface waters, except for the area below 30°S, where the average 238Pu/239,240Pu ratios (0.20±0.04) suggest the possible influence of the SNAP Satellite that burned-up over the Indian Ocean in 1964. [Copyright &y& Elsevier]

To analyze plutonium (Pu) in open ocean waters can be challenging due to the low seawater concentrations. In this study we compared two techniques for Pu determination, one in-situ MnO 2 cartridge system and the more commonly used MnO 2 precipitation technique. During the pre-pilot GEOTRACES cruise ANT XXX-1 (2005) we tested MnO 2 cartridges for the pre-concentration of Pu from seawater at 19 sampling stations on a transect in the southeastern Atlantic Ocean between Vigo (Spain) and Cape Town (South Africa). Our in-situ sampling setup consisted of one particle cartridge followed by three MnO 2 cartridges in a series. Through the system we pumped between 956 and 2700 l of surface seawater with a flow rate between 1.6 and 5.2 l/min. We found that the adsorption efficiency of a single MnO 2 cartridge to adsorb Pu was rather constant and on average a 58 ± 7%. The adsorption efficiency was also found to be independent of seawater: temperature in the range of 18.3–29.2 °C, salinity range 34.2–37.1‰, and conductivity in the range of 46.8–58.4 mS/cm. In parallel with the in-situ sampling, discrete surface water samples between 259 and 281 l were taken and Pu was pre-concentrated using the MnO 2 precipitation method. We find a good agreement between the Pu concentrations determined with the two different techniques. The in-situ pre-concentration technique requires more radiochemical work in the laboratory but has the advantage that large seawater volumes can be sampled without the necessity for radiochemical processing on-board the ship. The much larger volumes sampled with the in-situ technique compared with the precipitation technique, enables accurate determination of Pu-isotopic ratios with a low relative standard deviation. We have shown in this study that in-situ MnO 2 cartridge technique can be used in a reliable way for the determination of dissolved Pu seawater concentration in open ocean waters. • Plutonium pre-concentration technique comparison: MnO 2 precipitation vs. in-situ MnO 2 cartridge. • Sea water parameters potentially affecting the in-situ MnO 2 cartridge Pu absorption efficiency are discussed. • The in-situ MnO 2 cartridge technique is robust for Pu determination and suitable for large sea water samples. [ABSTRACT FROM AUTHOR]

Abstract: Coastal ecosystems are subject to many anthropogenic pressures, including pollution and the enhancement of sedimentation due to human activities. The lower reach of the Coatzacoalcos River is considered to be the most polluted coastal area of Mexico due to the presence of major petrochemical production centers in its watershed. In order to show the impact of land use change and industrial activities on the adjacent coastal environment of the Coatzacoalcos River, we reconstructed the historical changes of sediment transport and trace metals contamination based on the study of a 210Pb dated sediment core. Several geochemical indicators, such as clay mineral content, the concentrations of reference elements (Al, Ca, Sr, Rb) and the carbon isotope ratio (δ13C) revealed a change of sediment and contamination sources since the early 80s, in coincidence with the large industrial and urban development in the area. We conclude that the increased contaminant loads were related to terrestrial sources, likely contaminated and eroded soils from the catchment, due to extensive land use changes. Although the contaminant enrichment since the early 80s was low, As, Hg and Ni concentrations show potentially dangerous levels and exceed the USEPA-ERL concentration benchmarks, thus constituting a potential threat to marine aquatic life and humans through seafood consumption. [Copyright &y& Elsevier]

An international sampling cruise, the IAEA’97 NW Pacific Expedition, was carried out in 1997 with the primary objective of contributing to better understanding of the present distributions of radionuclides in the open ocean and of the processes affecting their distributions in the water column, to study the sources which have introduced radionuclides to the Pacific Ocean, and to compare present results with historical data sets obtained from the previous expeditions (e.g., the Geochemical Ocean Sections Programme, GEOSECS). The observed temperature, salinity, dissolved oxygen, and silicate levels in water samples collected showed differences in the upper 1000 m layer in all studied profiles. Transuranics water profiles showed typical sub-surface maxima, with concentrations less by about a factor of 4 than the GEOSECS results, at depths greater by about a factor of 2 and a decrease in the water column inventory by about 20% over 24 years, which were less a function of particle-driven vertical processes and more in response to water mass circulation in the region. Increases in concentrations were observed in deep water near the sea floor. Transuranics inventories in the water column substantially exceeded those expected from global fallout. 90Sr and 137Cs data confirm that the observed changes in concentration profiles have resulted from physical circulation of the regional water masses and transport of radionuclides to deep waters. The IAEA’97 results present the most comprehensive recent study on the distribution of 239,240Pu, 90Sr and 137Cs in the NW Pacific Ocean with a description of the behaviour of these radionuclides in the water column and the effects of the physical forcing of water mass circulation over the last 24 years. [Copyright &y& Elsevier]