Lago Verde is a fresh-water maar found on the lower slopes of San Martin volcano, at the Sierra de Los Tuxtlas, Mexico, currently the northernmost remnant of the tropical rain forest in America. 210Pb and 137Cs analyzed in a sediment core were used to reconstruct the historical fluxes of Ag, Cd, Cu, Pb, Hg and Zn to the site during the last ∼ 150 yr. The 210Pbxs-derived sediment accumulation rates, the magnetic susceptibility, C/N ratios and δ13C data evidenced background conditions at the lake until 1960s, when enhanced erosion related to the clearing of large forested areas at Los Tuxtlas promoted higher accumulation rates of a heavier and more magnetic sedimentary material. Recent sediments from Lago Verde were found enriched by Pb (26-fold natural concentration level [NCLs]) and moderately enriched by Cd>Cu>Zn and Hg (6-, 5-, 4- and 4-fold corresponding NCLs, respectively). The fluxes of Cu, Hg, Pb and Zn have significantly increased since 1940s, with peak ratios of total modern to pre-industrial fluxes of 11, 11, 19 and 49, respectively. The lake occupies a relatively pristine, non-industrialized basin, and therefore the increased metal fluxes might be related to long-distance aeolian transport of trace metals.

Taiwan is a young and seismically active mountain belt, where a series of strong earthquakes (M>7) have occurred over the past hundred years. Identifying historical earthquakes around Taiwan is a key to better constrain the geodynamic of this active region. Sedimentological and geochemical analyses of surface sediments from one station offshore east Taiwan revealed the presence of coarse-grained layers interpreted as turbidites. The age of these layers have been determined by 210Pb, 137Cs, and 241Am chronology. Dating of the three most recent turbidites provides ages of AD 2001±3, AD 1950±5, and AD 1928±10. The results show striking temporal correspondence of turbidite layers to large (M≥6.8) earthquakes recorded in the region since the 20th century. The chronologies of sediment layers lead us to believe that turbidites resulted from the 2003 Taitung earthquake (M 6.8), the 1951 Chengkong earthquake (M 7.1), and the 1935 Lutao earthquake (M 7.0), respectively. Such a good correlation between turbidites and high-magnitude (M≥6.8) historical and instrumental seismic events suggests that turbidite paleoseismology constitutes a valuable tool for earthquake assessment in the eastern Taiwan margin. Moreover, the modern reservoir radiocarbon age and the regional marine reservoir correction (ΔR) of the Kuroshio Current off Taiwan were estimated by comparing accelerator mass spectrometry (AMS) 14C ages with ages derived from corrected 210Pb profiles and historical accounts of identifiable seismic events. Such a determination is important to calibrate the 14C ages of marine materials for accurate comparison of marine and continental geological records. Our calculated mean ΔR value of 232±54 14C yr (n=2) is higher than its modern value of 86±40 14C yr. This high value can be explained by the presence of local upwelling cells and turbulence in the Kuroshio Current, north of Green Island. These upwelling cells bring 14C-depleted water to the surface, resulting in an increase of the modern ΔR value in this portion of the Kuroshio Current.

In order to study the vertical migration of anthropogenic 137Cs, soil inventories ofthis radionuclide were measured in two regions selected on the basisof a previous comprehensive survey in the northern Iranian provinceof Guilan located in the South Caspian region. Ten sampling stations were randomly chosen in these regions and split-level samplingwas carried out to a depth of 30 cm. Sample analysis was performedusing a HPGe detector system. In situ gamma measurementsin both regions were als o carried out with the aid of a portable germanium spectrometer.The experimental data were then compared with the solution of theconvection-dispersion equation (CDE) with the proper initial and boundary conditions to evaluate initialdeposition as well as transport parameter values. The solution,including the effects of both considered sources, i.e. global falloutand Chernobyl releases, fits the measured data well. The effectiveconvection velocity and dispersion coefficients of 137Cslie in the range of 0-0.25 cm·y-1 and 0.32-0.75 cm2·y-1, respectively, indicating a very slow migration rate in the area. Most of the deposited 137Cs still remainedin the top 10-cm layer. Moreover, the fitted depth profiles werethen employed to correct the surface activities of 137Csestimated by in situ measurements.

Reservoir sedimentation provides a valuable source of data on sediment flux. This paper assesses the record of sedimentation in the Baldernock Mill dam, a small mill dam in western Scotland. That record is based on the volume of sediment in the dam, and the detailed analysis of a continuously sampled stratigraphic section through the impounded sediment, with a chronology for mill dam construction and subsequent breaching based on historical maps and the impounded sediment’s content of 137Cs and lead isotopes. The mill dam was constructed in c. 1820, was initially partially breached in the late nineteenth or early twentieth century and then fully breached by about the mid 1920s. The dam trapped relatively low volumes of sediment and the correspondingly low rate of sediment flux indicated by the volume of impounded sediment reflects the dam’s very low trap efficiency. The basal Unit 1 in the impounded sediments was deposited between dam construction and the initial breaching of the wall. The unit consists of repeated ‘triplets’ of a basal sand (flood deposit) grading upwards into a mud deposit (post-flood deposition), which is in turn overlain by an organic-rich layer of leaves and twigs (the subsequent autumn leaf fall). Unit 2 is similar to Unit 1 but lacks the organic layer, indicating the lack of ongoing standing water to trap the autumn leaf fall, and Unit 3 was deposited after full breaching of the wall. Mill dams in Scotland generally impound small steep bedrock channels – the latter reflecting a strong glacial legacy in Scotland – and are only small structures designed to ensure water for mills during dry periods in a climate of otherwise generally moderate to high and reliable rainfall. The small sizes of these dams and their low wall heights mean that they trap relatively low volumes of sediment that have minimal to minor downstream impacts if the dams fail.

Les longues séries temporelles d'observation de la radioactivité dans l'atmosphère (au niveau du sol) permettent d'étudier l'évolution de ce réservoir après les injections des expérimentations nucléaires militaires, de l'activité industrielle, ou suite aux accidents tel que celui de Tchernobyl (1986). Conjointement à l'observation des radionucléides d'origine artificielle, les radionucléides formés par l'interaction du rayonnement cosmique dans la haute atmosphère, comme 7Be, sont quantifiés. La corrélation entre les composantes naturelles et artificielles permet de mieux comprendre l'évolution globale de la radioactivité dans l'atmosphère. L'observatoire de la radioactivité dans l'atmosphère de l'Institut de radioprotection et de sûreté nucléaire (IRSN) a débuté en 1959. Actuellement les aérosols sont prélevés dans 6 stations localisées en Métropole et dans 2 stations en Outre-mer (hémisphère sud). Les concentrations de 137Cs dans les aérosols en 2002 sont de l'ordre de 0,4 μBq m-3 en métropole et 10 fois moins à Tahiti. Les activités du 7Be, de l'ordre de 3 200 μBq m-3, sont similaires en métropole et à Tahiti.

A radioecological survey around Terra Nova Bay showed that 239 + 240Pu, 238Pu, 241Am, 90Sr and 137Cs activities were detectable in nearly all the samples. The 239 + 240Pu and 241Am concentrations in seawater were slightly lower than those in the northern Pacific Ocean. The activity level of 239 + 240Pu, 241Am and 137Cs in Antarctic sediments (Ross Sea) was c. 5–20 times lower than in northern Adriatic sediments (Mediterranean Sea), but the 238Pu activities were relatively high. The 90Sr concentrations in all the sediment samples from both the Ross and Adriatic seas tended to be low which might be due to an easier exchange of 90Sr in seawater. On the other hand, high concentrations were detected in Antarctic mosses, lichens and algae and their activity levels are comparable to those in central Italy. The radionuclide ratio analyses show that the major part of 239 + 240Pu, 241Am, 90Sr and 137Cs is the result of nuclear weapon tests. A higher 241Am/239 + 240Pu ratio might be due to the fallout of earlier atmospheric nuclear tests. The 238Pu239 + 240Pu ratio in the Antarctic matrices is about seven times higher than in the Northern Hemisphere and this could suggest that the major part of 238Pu originated from the SNAP-9A satellite accident.

17 ans après l'accident de Tchernobyl, cette étude propose une reconstitution des dépôts de 137Cs dus à cet accident sur l'ensemble du territoire français métropolitain. Cette reconstitution est basée sur la relation entre les dépôts de 137Cs et les pluies de la première semaine de mai 1986, validée sur le tiers-est du pays, et sur une modélisation de l'appauvrissement d'est en ouest des masses d'air contaminées. La carte proposée, établie suivant la même méthode géostatistique que celle utilisée par la Commission européenne, est cohérente avec les estimations des dépôts de 137Cs dans les pays d'Europe voisins.

Avec des dépôts de 137Cs dépassant quelquefois 20 000 Bq m-2, certains coteaux de la vallée du Rhône ont été assez fortement touchés par les retombées de l'accident de Tchernobyl. C'est le cas à Cornas (Ardèche) près de Valence et à Vinsobres (Vaucluse) au nord de Vaison-la-Romaine. La vigne occupe dans ces régions l'essentiel des surfaces agricoles, pour la production d'un vin réputé. Cette étude montre que les conséquences des retombées de l'accident de Tchernobyl pour les vins de la vallée du Rhône ont été visibles mais très faibles. L'activité en 137Cs du vin produit en 1986 n'a pas atteint 1 Bq/l. Ces conséquences très limitées sont dues à la date des dépôts qui sont intervenus début mai 1986, alors que les vignes développaient à peine leurs premières feuilles. Depuis 1986, l'activité en 137Cs du vin a fortement décru jusqu'à revenir en 2000 à un niveau proche de celle d'avant l'accident : quelques millibecquerels par litre. Le césium ajouté aux sols, dans des proportions pourtant importantes, se trouve essentiellement dans les 20 premiers centimètres et est peu disponible pour les racines de la vigne.

At the end of July 1998, three 137Cs sources (between 0.17 and 150 GBq) were found in the vicinity of the village of Matkhoji, located at 300 km to the west of Tbilissi. This site was a former Russian military base, abandoned since 1992 and used now as pasture and a playground for the children. The Georgian Environment Ministry requested assistance from IAEA which sent a mission to the site. This established that a predominantly chronic exposure of part of the population of the village has occurred. The IAEA requested technical assistance from IPSN. A mission, made up of 4 people from IPSN and a representative of the IAEA went to the site from 12 to 17 October 1998. This mission collected information on the circumstances of the exposure and selected a potentially explored cohort of 112 people, in three groups: children of more than five years and adults of less than 50 years attending the site and members of a family who had a source in their cattle shed. An analysis of hematologic parameters was performed on these people and 85 blood samples were taken for biological dosimetry. The hematologic analysis carried out on the spot did not show any particular anomaly. The biological dosimetry by scoring of unstable chromosome aberrations (dicentric, rings centric, fragments) in blood peripheral lymphocytes was performed on blood samples after air transportation to the specialised laboratory (LDBM) of the IPSN Two successive procedures were initiated. The first was a quick phase of triage not very precise but intended to check if some of these people presented obvious signs of irradiation. Only 50 cells per subject were scored. Seven days were needed to complete this phase. Dicentrics were found in three people only indicating a whole-body dose not exceeding 0.5 Gy on average. This triage was followed of a more complete but longer examination, where chromosome aberrations were scored in 250 cells. Six weeks were necessary to score 22 000 cells from the 85 people. In total, 30 dicentrics were scored among only 17 Georgian patients. The highest dose to the whole body estimated from a reference calibration curve was 0.3 Gy The majority of these dicentrics was found in the children having played on several occasions in the former military camp. Unfortunately, the information provided by the population was too fragmentary to permit an effective reconstruction of the individual doses.