On <Superscript>137</Superscript>Cs migration in water systems of Eastern Fennoscandia

The rate of natural removal of ¹³⁷Cs from water bodies in Eastern Fennoscandia is evaluated. The half-time T of water purification from global ¹³⁷Cs in lake–river systems was ~6.5 years and that for river systems was 6.5–10 years. For the 15- and 20-year exposure of ¹³⁷Cs in watershed soils, its annual input in rivers was 0.021–0.120 and 0.017–0.070% of its reserve. The period of May–December 1986 showed maximal export of ¹³⁷Cs, i.e., 1.1% of its reserve. ¹³⁷Cs export into rivers decreased in the region from north to south because of changes in landscape and climate conditions that affect ¹³⁷Cs migration on watersheds.     

Radionuclide ratios in wet and dry deposition samples from June 1976 through December 1977

²³⁸Pu,²³⁹Pu and¹³⁷Cs in rain and dry fallout and⁹⁰Sr in rain samples were measured at Woods Hole, Massachusetts, from June 1976 through December 1977. The dry fallout was estimated to be about 7.8% of the total deposition of²³⁹Pu and¹³⁷Cs.²³⁹Pu/¹³⁷Cs ratios, almost constant at about 0.011 in rain or dry fallout, February through December 1977, suggested that fractionation between the refractory and volatile radionuclides is insignificant in stratospheric fallout. This supports the idea of regional homogeneity of radionuclide ratios in fallout.     

<Superscript>137</Superscript>Cs in deep-water lakes: Analysis of the peculiarities of water contamination and purification

The assessment of ¹³⁷Cs concentration in water based on the model of radionuclide absorption by the bottom sediment of a closed water body is applicable to deep-water lakes with slower water circulation (the time of water exchange exceeding 10 years). The low river runoff from such lakes does not determine their water purification from ¹³⁷Cs because of the predominance of the process of ¹³⁷Cs sorption by suspension and bottom sediment. The contamination of a deep-water arctic lake with global ¹³⁷Cs is reconstructed.     

Anthropogenic Radionuclides in the Caspian Sea

Analysis and interpretation of the distribution of anthropogenic radionuclides ⁹⁰Sr, ¹³⁷Cs, and ^239,240Pu in the Caspian Sea water are presented. These radionuclides are shown to be of environmental importance and to be useful for studying water mass dynamics.     

Concentrations of 137Cs, 90Sr, 108m Ag, 239+240 Pu and atom ratio of 240Pu/239Pu in tanner crabs, Chionoecetes japonicus and Chionoecetes opilio collected around Japan

The anthropogenic radionuclides, ¹³⁷Cs, ⁹⁰Sr, ^108mAg, ^239+240Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996–2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of ²⁴⁰Pu/²³⁹Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet.     

Plutonium,radiocesium and radiocobalt in sediments of the Hudson River estuary

Anthropogenic radionuclides have reached the Hudson estuary as global fallout from nuclear weapons testing and through local releases from commercial nuclear reactors. Significant activities of²³⁸Pu and^239,240Pu (fallout-derived),¹³⁴Cs and⁶⁰Co (reactor-released), and¹³⁷Cs (derived from both sources), have accumulated in the sediments throughout the estuary, with the primary zone of accumulation near the downstream end of the system in New York harbor. The estuary appears to have trapped nearly all of the^239,240Pu delivered as fallout, and consequently, ocean dumping of dredged harbor sediment is currently the primary means for the net transport of these nuclides to coastal waters. In contrast, only 10–30% of the¹³⁷Cs,¹³⁴Cs and⁶⁰Co delivered to the estuary have been retained on the fine particles which accumulate at a rapid rate in the harbor.The primary factors which have governed the distribution of anthropogenic radionuclides in Hudson sediments are: (1) spread of fine particles labeled with both fallout and reactor nuclides throughout the axis of the estuary, (2) differences in timing of the peak fallout years (1962–1964) and years of maximum reactor releases (1971–1972), (3) large variations in sediment accumulation rates, ranging from a few millimeters per year or less to many tens of centimeters per year, (4) appreciable desorption of¹³⁷Cs and¹³⁴Cs from particles at higher salinities, and (5) possible enhanced desorption of⁶⁰Co at higher salinities (relative to¹³⁴Cs and¹³⁷Cs) which may be associated with the release of reduced manganese from the harbor sediments.     

Distribution and content of different artifical radio nuclides in the water of the North Sea during the years 1977 to 1981 (complemented with some results from 1982 to 1984)

Summary The measured concentrations of¹³⁷Cs in the water of the North Sea gained during the years 1977 to 1982 largely confirm the results found in the preceding years (Fig. 1). After a distinct maximum in 1978 — brought about by a particularly strong influx during 1977 — the total quantity of¹³⁷Cs present in the North Sea has reced, to around half of these peak values by the year 1982 (Table 1).On the way from the Sellafield Works near the Irish Sea as far as into the North Sea, a strong shift of the¹³⁷Cs:⁹⁰Sr ratio in favour of the⁹⁰Sr can be observed.By following the temporal course of that ratio at different measurement points, a transport time can be deduced of around 3 years between the Sellafield Works and the Pentland Firth; a further year would be needed to reach into the southeastern North Sea.The ratio Cs:Sr furthermore permits, in the southeastern North Sea, a good distinction between the watermasses comming from the north into the North Sea with respect to those that come through the Channel from the South. These masses practically flow side by side until about the entrance to the Skagerrak.The vertical distribution of the¹³⁷Cs shows, as is to be expected, seasonally conditioned differences. However, effects also occur, which — on the basis of the data available to date — do not yet permit a clear explanation.The⁹⁰Sr, as well as the^239+240Pu, present in the North Sea show an analogous distribution scheme compared with that of the¹³⁷Cs. Their concentrations lie far below that of the¹³⁷Cs (⁹⁰Sr 17.5%;^239+240Pu 0.03%).Tritium, on the other hand — with essentially higher concentrations — shows a completely different distribution, because it is principly introduced via the freshwater flowing in from the land.

---

Verteilung und Gehalt verschiedener künstlicher Radionuklide im Wasser der Nordsee in den Jahren 1977 bis 1981 (ergänzt durch einige Ergebnisse von 1982 bis 1984)

Zusammenfassung Die in den Jahren 1977 bis 1982 gewonnenen Meßdaten der Aktivitätskonzentrationen von¹³⁷Cs im Wasser der Nordsee bestätigen weitgehend die in den vorhergehenden Jahren gefundenen Ergebnisse (Fig. 1) Nach einem deutlichen Maximum im Jahre 1978 — hervorgerufen durch eine besonders starke Zufuhr im Jahre 1977 —ist die in der Nordsee insgesamt vorhandene Menge an¹³⁷Cs bis zum Jahre 1982 wieder auf rund die Hälfte zurückgegangen (Tab. 1).Auf dem Weg von den Sellafield Works an der Irischen See bis in die Nordsee ist eine starke Verschiebung des¹³⁷Cs:⁹⁰Sr Verhältnisses zugunsten des⁹⁰Sr zu beobachten.Aus dem zeitlichen Verlauf dieses Verhältnisses an verschiedenen Meßpunkten ergeben sich Transportzeiten zwischen den Sellafield Works und dem Pentland Firth von rund 3 Jahren; bis in die südöstliche Nordsee wird ein weiteres Jahr benötigt.Das Verhältnis Cs:Sr erlaubt außerdem in der südöstlichen Nordsee eine gute Unterscheidung der aus der Nordsee bzw. durch den Kanal von Süden kommenden Wassermassen, die praktisch nebeneinander her bis etwa zum Beginn des Skagerraks fließen.Die Vertikalverteilung des¹³⁷Cs zeigt, wie zu erwarten ist, jahreszeitlich bedingte Unterschiede. Es treten aber auch Effekte auf, die sich anhand der bisher vorliegenden Daten noch nicht eindeutig erklären lassen.Das in der Nordsee vorhandene⁹⁰Sr sowie das^239+240Pu zeigen ein analoges Verteilungsschema verglichen mit dem des¹³⁷Cs. Ihre Konzentrationen liegen weit unter der des¹³⁷Cs (⁹⁰Sr 17,5%,^239+240Pu 0,03%).Das Tritium zeigt bei wesentlich höheren Konzentrationen dagegen eine völlig andere Verteilung, da seine Hauptzufuhr im wesentlichen über das von Land her zufließende Süßwasser erfolgt.

---

Distribution et teneur de differents radionucleides artificiels, dans les eaux de la Mer du Nord entre les années 1977 et 1981 (completes par quelques résultats de 1982 à 1984)

Résumé Les mesures de concentration du Césium 137 dans les eaux de la Mer du Nord, acquises entre les années 1977 et 1982, confirment largement les résultats obtenus au cours des années précédentes. Après un net maximum en 1978 — occassionné par un apport particulièrement fort en 1977 — la quantité totale de Césium 137 présent en Mer du Nord a régressé,jusqu'en 1982, aux alentours de la moitié de ces valeurs maximales.Il a pu être observé une modification importante du rapport Césium 137/Strontium 90, en faveur du Strontium 90, sur le trajet de Sellafield Works prés de la Mer d'Irlande jusqu'à la Mer du Nord.En suivant l'évolution temporelle de la valuer de ce rapport en différents points de mesure, on peut en déduire une durée de transport d'environ 3 ans entre Sellafield Works et Pentland Firth; une année supplémentaire est ensuite nécessaire pour pénétrer en Mer du Nord Sud-orientale.En Mer du Nord Sud-orientale, le rapport Césium/Strontium permet en outre d'effectuer une nette distinction entre les masses d'eau pénétrant respectivement par le Nord dans la Mer du Nord et celles pénétrant par le Sud et venant de la Manche. Ces masses d'eau s'écoulent pratiquement côte à côte jusqu'à l'entrée du Skagerrak.Comme l'on pouvait s'y attendre, la distribution verticale du Césium est différente suivant les saisons. Cependant il apparaît également des effects qui, sur la base des données disponibles à ce jour, ne s'expliquent pas encore clairement.Le Strontium 90 aussi bien que le Plutonium 239+240 présent dans la Mer du Nord, montrent une distribution comparable, analogue à celle du Césium 137. Leurs concentrations sont bien inférieures à celle du Césium 137 (Strontium 90 17,5%; Plutonium 239+240 0,03%).Le tritium d'autre part, — avec des concentrations significativement plus fortes —montre une distribution complètement différente, due principalement au fait qu'il est introduit par l'intermédiaire de l'écoulement d'eau douce provenant de la terre.

     

Fallout radionuclides in the Pacific Ocean: Vertical and horizontal distributions,largely from GEOSECS stations

From GEOSECS stations, largely, the 1974 distributions of Pu and of¹³⁷Cs are described in the Pacific Ocean north of about 20°S latitude. Changes in some of these distributions are described from 1978 cruises by the authors.The Pacific exhibited, everywhere, a shallow subsurface layer of Pu-rich water with its concentration maximum at about 465 m in 1974; over a large portion of the central North Pacific a second layer of Pu-labelled water, less concentrated than the shallow layer, lay just above the bottom. Similar features were not observed in the case of¹³⁷Cs.The inventories of both Pu and¹³⁷Cs in the water column at most 1974 stations are substantially greater than those to be expected from world-wide fallout alone; these inventory excesses appear to be attributable to close-in fallout, but only if the ratio Pu/¹³⁷Cs in this source was much higher than in world-wide fallout. The North Pacific mean ratio of the inventories is 2.2 times that observed in world-wide fallout.Resolubilization of Pu both from sinking particles and from sediments explains peculiarities of its depth distributions.There is little evidence for tracer movement by sliding downward along density surfaces;¹³⁷Cs appears to have moved to depth by downmixing at the edge of the Kuroshio, and then moved horizontally and upward alongσ_t contours. The shallow Pu-rich layer shows no coordination with density, salinity or O₂ isopleths. The deep Pu-rich layer is restricted to a narrow range of O₂ concentrations that confirm its origin in the Aleutian Trench and rapid spread southward and laterally. Near-bottom circulation processes have been much more active than here-to-fore described.     

Sediment characteristics and wind-induced sediment dynamics in shallow Lake Markermeer, the Netherlands

In 2007/08, a study was undertaken on the sediment dynamics in shallow Lake Markermeer (the Netherlands). Firstly, sediment characteristics were determined at 49 sites in the lake. Parameters such as median grain size and loss on ignition showed a spatial as well as water depth related pattern, indicating wind-induced sediment transport. Highly significant correlations were found between all sediment parameters. Lake Markermeer sediment dynamics were investigated in a sediment trap field survey at two permanent stations in the lake. Sediment yields, virtually all coming from sediment resuspension, were significantly correlated with average wind speeds, though periods of extreme winds also played a role. Sediment resuspension rates for Lake Markermeer were high, viz. on average ca. 1,000 g m⁻² day⁻¹. The highly dynamic nature of Lake Markermeer sediments must be due to the overall shallowness of the lake, together with its large surface area (dynamic ratio = [√(area)]/[average depth] = 7.5); wind-induced waves and currents will impact most of the lake’s sediment bed. Indeed, near-bed currents can easily reach values >10 cm/s. Measurements of the thickness of the settled “mud” layer, as well as ¹³⁷Cs dating, showed that long-term deposition only takes place in the deeper SE area of the lake. Finally, lake sediment dynamics were investigated in preliminary laboratory experiments in a small “micro-flume”, applying increasing water currents onto five Lake Markermeer sediments. Sediment resuspension started off at 0.5–0.7 cm/s and showed a strongly exponential behaviour with respect to these currents.     

A Rb/Sr record of catchment weathering response to Holocene climate change in Inner Mongolia

Variation in the rubidium to strontium (Rb/Sr) ratio of the loess–palaeosol sequences has been proposed to reflect the degree of pedogenesis and weathering in the northwestern region of China. To characterize the Rb/Sr ratio of the dissolved loads of a single catchment, we analysed a 12·08 m sediment core from Daihai Lake in Inner Mongolia, north China. Dating control was provided by ²¹⁰Pb, ¹³⁷Cs and AMS‐¹⁴C. Sequential extraction experiments were conducted to investigate the concentrations of Rb and Sr on various chemical fractions in the lake sediments. Down‐core variation in the Rb/Sr ratios provides a record of Holocene weathering history. From 9 to 3·5 ka bp , accelerated chemical weathering was experienced throughout the Daihai catchment under mainly warm and humid conditions, and this reached a maximum at c. 5 ka bp . However, weathering was reduced between c. 8·25 and 7·90 ka bp , which may reflect the global 8·2 ka cooling event. After c. 2·5 ka bp , increased Rb/Sr ratios with higher frequency of fluctuations indicate reduced weathering within the Daihai catchment. The highest Rb/Sr ratios in the Little Ice Age lake sediments indicate the weakest phase of Holocene chemical weathering, resulting from a marked reduction in Sr flux into the basin. The Rb/Sr record also shows an enhancement of chemical weathering under today's climate, but its intensity is less than that of the Medieval Warm Period. Increased Rb/Sr in lake sediment corresponding to reduced catchment weathering is in striking contrast to Rb/Sr decrease in the glacial loess layers in the loess–palaeosol sequence. Copyright © 2005 John Wiley & Sons, Ltd.     

Rating Water Quality in Sevastopol Bay by the Fluxes of Pollutant Deposition in Bottom Sediments

Sevastopol Bay is used as an example for the development of criteria for rating anthropogenic impact by elimination fluxes from the water area of post-Chernobyl (⁹⁰Sr, ¹³⁷Cs, ^239,240Pu) and natural (²¹⁰Pо) radionuclides, as well as mercury and organochlorine compounds. The differentiation of the bay water area into zones with different biogeochemical conditions and the balance approach to interpreting field observation data were used to assess the conditioning capacity of Sevastopol Bay ecosystem for conservative radioactive and chemical substances by elimination fluxes of pollutants into aqueous depot, which is the open part of the Black Sea and into the geological depot, i.e., its bottom sediment stratum.     

Elevated sedimentation in lake records linked to agricultural activities in the Ishikari River floodplain,northern Japan

The purpose of this study was to examine the historical change in sedimentation rates in lakes that have been impacted by river regulation and agricultural activities in the Ishikari River floodplain. We dated sediment cores using caesium‐137 (¹³⁷Cs) dating and tephrochronology, and we estimated sediment sources from ¹³⁷Cs concentrations in the topsoil of representative land covers. We found that, between 1739 and 1963, the distance between the lake and the main river channel and whether or not the lake was connected to the river affected the sedimentation rates. After 1963, agricultural drainage systems were established in the Ishikari River floodplain. The average sedimentation rate before and after the construction of drainage ditches varied between 1–66 and 87–301 mg cm^–2 a^–1, respectively. The increase in the sedimentation rate after 1963 was caused by the construction of a number of drainage networks, as well as extensive cultivation activity and/or fragmentation of the swamp buffers surrounding the lakes. The ¹³⁷Cs activities at the surfaces of the lake as well as the catchment‐derived ¹³⁷Cs contributions and ¹³⁷Cs inventory in the lake profiles were used to examine the sediment influx from the various drainage areas after the establishment of the drainage system. Our results indicate that the majority of the lake sediments were derived from cultivated areas, and therefore the catchment‐derived ¹³⁷Cs contribution in the lakes was strongly correlated with the sedimentation rate. The ¹³⁷Cs inventory across all of the lake profiles was also significantly greater than the atmospheric fallout. We identified a negative correlation between the ¹³⁷Cs lake profile inventory and the sedimentation rate. This is because the sediment originating from the drainage areas contained low ¹³⁷Cs concentrations, which diluted the overall concentration of ¹³⁷Cs in the lake sediment. Copyright © 2009 John Wiley & Sons, Ltd.     

Depositional history of artificial radionuclides in the Ross Ice Shelf,Antarctica

The annual fluxes of artificial radionuclides (²³⁸Pu,^239+240Pu,²⁴¹Am,¹³⁷Cs,⁹⁰Sr and³H) from the atmosphere to the Ross Ice Shelf in Antarctica were determined from measurements in strata dated by²¹⁰Pb. Recognizable sources include the U.S. tests (Mike-Ivy and Castle Hill) in the early 1950s, the U.S.S.R. tests of the early 1960s, the SNAP-9A burnup of 1964 and the French and Chinese tests in the late 1960s and 1970s. There are several problems still awaiting resolution: the differences in atmospheric chemistries of fission products and of transuranics produced in weapons tests and the anomalous fluxes of²³⁸Pu to the ice shelf which do not appear to reflect a one-year stratospheric residence. There is no evidence for a smearing of the fallout record as a consequence of diffusion of these radionuclides in the glacial column.     

Bomb‐fallout 137Cs as a marker of geomorphic stability in dune sands and soils,Pinery Provincial Park,Ontario, Canada

The anthropogenic radionuclide ¹³⁷Cs has been extensively utilized as a tracer of geomorphic processes in the northern hemisphere since its deposition during atmospheric testing of nuclear devices in the 1950s and 1960s. The distribution of bomb‐fallout ¹³⁷Cs was measured on a sequence of coastal dune sands and soils at Pinery Provincial Park, on the coast of Lake Huron in southern Ontario, Canada. The depth distribution within the stabilized, developed soils inland reflected the relationship between clay content and the adsorption and immobilization of the radionuclide. However, the influence of soil organic matter, silt‐sized particles and vegetation cycling on the profile distribution could not be discounted. Within the geomorphically dynamic dune sands near the coast, there was a significant activity of ¹³⁷Cs even though the sands were lacking in clay‐sized particles. Within a buried soil on the inland side of a large active dune blowout, the distribution of ¹³⁷Cs with depth was useful as a stratigraphic marker of the rates of accumulation of sands at that position. Therefore ¹³⁷Cs may be a useful alternative to erosion pins, sequential air photos and sediment traps in the monitoring of dune destabilization in coastal environments. Copyright © 2001 John Wiley & Sons, Ltd.     

Pu and137Cs in coastal sediments

Analyses are presented of¹³⁷Cs,²³⁸Pu, and^239,240Pu, in relation to depth in sediment, in 21 gravity cores. These cores span the ranges of times 1964–1975, and of water depths 12–2000 m; they come from three distinct sedimentation areas off the northeast coast of the United States. Although the ranges of total sediment inventories of^239,240Pu and of¹³⁷Cs from the various areas hardly overlap, the range of ratios of the inventories of these two nuclides is probably the same in all the areas. In the shallow-water cores the^239,240Pu/¹³⁷Cs ratio regularly diminishes with depth in the core, and a tendency is seen for curves of this function to have similar slopes in each area; ratios of²³⁸Pu/^239,240Pu show no change with depth in these shallow-water cores. In the deeper-water cores, the^239,240Pu/¹³⁷Cs ratio shows no systematic change with depth, but sometimes the²³⁸Pu/^239,240Pu ratio shows a minimum at the sediment surface, and is much higher deeper in the cores. We believe that these phenomena can be explained in terms of a complicated bioturbational process moving the nuclides, together, down into the sediments, of chemical resolubilization, at depth, of plutonium only, and of its subsequent upward translocation in the interstitial solution. Some re-immobilization of plutonium near the sediment surface is implied, and a mechanism is suggested for this, based on displacement of plutonium from organic complexes by the increasing concentrations, in upper layers of the sediment, of re-oxidized dissolved iron.     

Sedimentation in arctic proglacial lakes: Mittivakkat Glacier,south‐east Greenland

Several sediment cores were collected from two proglacial lakes in the vicinity of Mittivakkat Glacier, south‐east Greenland, in order to determine sedimentation rates, estimate sediment yields and identify the dominant sources of the lacustrine sediment. The presence of varves in the ice‐dammed Icefall Lake enabled sedimentation rates to be estimated using a combination of X‐ray photography and down‐core variations in ¹³⁷Cs activity. Sedimentation rates for individual cores ranged between 0·52 and 1·06 g cm⁻² year⁻¹, and the average sedimentation rate was estimated to be 0·79 g cm⁻² year⁻¹. Despite considerable down‐core variability in annual sedimentation rates, there is no significant trend over the period 1970 to 1994. After correcting for autochthonous organic matter content and trap efficiency, the mean fine‐grained minerogenic sediment yield from the 3·8 km² basin contributing to the lake was estimated to be 327 t km⁻² year⁻¹. Cores were also collected from the topset beds of two small deltas in Icefall Lake. The deposition of coarse‐grained sediment on the delta surface was estimated to total in excess of 15 cm over the last c. 40 years. In the larger Lake Kuutuaq, which is located about 5 km from the glacier front and for which the glacier represents a smaller proportion of the contributing catchment, sedimentation rates determined for six cores collected from the centre of the lake, based on their ¹³⁷Cs depth profiles, were estimated to range between 0·05 and 0·11 g cm⁻² year⁻¹, and the average was 0·08 g cm⁻² year⁻¹. The longer‐term (c. 100–150 years) average sedimentation rate for one of the cores, estimated from its unsupported ²¹⁰Pb profile, was 0·10–0·13 g cm⁻² year⁻¹, suggesting that sedimentation rates in this lake have been essentially constant over the last c. 100–150 years. The average fine‐grained sediment yield from the 32·4 km² catchment contributing to the lake was estimated to be 13 t km⁻² year⁻¹. The ¹³⁷Cs depth profiles for cores collected from the topset beds of the delta of Lake Kuutuaq indicate that in excess of 27 cm of coarse‐grained sediment had accumulated on the delta surface over the last approximately 40 years. Caesium‐137 concentrations associated with the most recently deposited (uppermost) fine‐grained sediment in both Icefall Lake and Lake Kuutuaq were similar to those measured in fine‐grained sediment collected from steep slopes in the immediate proglacial zone, suggesting that this material, rather than contemporary glacial debris, is the most likely source of the sediment deposited in the lakes. This finding is confirmed by the ¹³⁷Cs concentrations associated with suspended sediment collected from the Mittivakkat stream, which are very similar to those for proglacial material. Copyright © 2000 John Wiley & Sons, Ltd.     

Weathering,Sr fluxes,and controls on water chemistry in the Lake Qinghai catchment,NE Tibetan Plateau

Strontium (Sr) concentrations and isotopic ratios have been measured in a series of water and rock samples from most of the major tributaries of the Lake Qinghai basin on the north‐eastern Tibetan Plateau. Dissolved Sr and ⁸⁷Sr/⁸⁶Sr show ranges of 488–12 240 nmol/l and 0·710497–0·716977, respectively. These data, together with measurements of major cations and anions in rivers and their tributaries and various lithologies of the catchment, were used to determine the contributions of Sr and its isotopic expense to rivers and lakes. Our results demonstrate that the chemical components and ⁸⁷Sr/⁸⁶Sr ratios of the alkaline waters are derived from mixing of carbonate and silicate sources, with the former contributing 72 ± 18% dissolved Sr to rivers. The difference in tributary compositions stems from the lithology of different river systems and low weathering intensity under a semi‐arid condition. Variation in ⁸⁷Sr/⁸⁶Sr ratios places constraint on the Sr‐isotopic compositions of the main tributaries surrounding Lake Qinghai. The water chemistry of the Buha River, the largest river within the catchment underlain by the late Paleozoic marine limestone and sandstones, dominates Sr isotopic composition of the lake water, being buffered by the waters from the other rivers and probably by groundwater. However, the characteristic chemical composition of the lake itself differs remarkably from the rivers, which can be attributed to precipitation of authigenic carbonates (low‐magnesium calcite, aragonite, and dolomite), though this does not impact the Sr isotope signature, which may remain a faithful indicator in paleo‐records. Regarding the potential role of groundwater input within the Lake Qinghai systems in the water budget and water chemistry, we have also determined the Sr concentration and ⁸⁷Sr/^S6Sr ratio of groundwater from diverse environments. This has allowed us to further constrain the Sr isotope systematic of this source. A steady‐state calculation gives an estimate for the groundwater flux of 0·19 ± 0·03 × 10⁸ m³/yr, accounting for about 8% of contemporary lake Sr budget. Copyright © 2010 John Wiley & Sons, Ltd.     

137Cs湖泊沉积年代学方法应用的局限——以Crawford湖为例

＾１３７Ｃｓ湖泊沉积年代学方法是测定现代湖泊沉积物沉积年代和沉积速率的重要同位素年代学方法之一。对加拿大Ｃｒａｗｆｏｒｄ湖采集的沉积孔柱内＾１３７Ｃｓ垂直分布的研究发现,该方法给出时的标有明显偏差。比较＾２１０Ｐｂ和纹层等年代方法的结果,其１９６３年时标蓄积峰值所在位置明显移向表层,而作为１９５４年时标的该核素出现蓄积的层位则远早于该年沉积物蓄积层位。研究还表明,孔柱中较高的间隙水含量、缺少足以吸     

Effect of mining and related activities on the sediment trace element geochemistry of Lake Coeur D'Alene,Idaho, USA part II: Subsurface sediments

During the summer of 1990, 12 gravity cores were collected in Lake Coeur d'Alene, Idaho at various depths and in a variety of depositional environments. All core subsamples were analysed to determine the bulk sediment chemistry; selected subsamples were analysed for trace element partitioning and ¹³⁷Cs activity. The purpose of these analyses was to determine the trace element concentrations and distributions in the sediment column and to try to establish a trace element geochemical history of the lake in relation to mining and mining-related discharge operations in the area. Substantial portions of the near-surface sediments in Lake Coeur d'Alene are markedly enriched in Ag, As, Cd, Hg, Pb, Sb and Zn, and slightly enriched in Cu, Fe and Mn. Variations in the thickness of the trace element-rich sediments, which range from more than 119 cm to as little as 17 cm, indicate that the source of much of this material is the Coeur d'Alene River. An estimated 75 million tonnes of trace element-rich sediments have been deposited on or in the lake bed. Estimated trace element masses in excess of those considered representative of background conditions range from a high of 468 000 tonnes of Pb to a low of 260 tonnes of Hg. The similarity between the trace element-rich surface and subsurface sediments with respect to their location, their bulk chemistry, their interelement relations and their trace element partitioning indicate that the sources and/or concentrating mechanisms causing the trace element enrichment in the lake sediments have probably been the same through-out their depositional history. Based on a Mt St Helens'ash layer from the 1980 eruption, ages estimated from ¹³⁷Cs activity and the presence of 80 discernible and presumably annual layers in a core collected near the Coeur d'Alene River delta indicate that deposition rates for the trace element-rich sediments have ranges from 2.1 to 1.3 cm/year. These data also indicate that the deposition of trace element-rich sediments began, at least in the Coeur d'Alene River delta, some time between 1895 and 1910, dates consistent with the onset of mining and ore processing activities that began in the area in the 1880s.     

Spatial variability in sedimentation rates and artificial radionuclide storage in alluvial banks of the lower Rh?ne River

This paper analyzes the relationship between bank sediment storage and radionuclide content in six alluvial sites located in different geomorphic contexts along the lower Rh?ne River. The ¹³⁷Cs, ²³⁸Pu, ^239+240Pu, ²⁴¹Am and ²¹⁰Pb profiles show different patterns, which indicates a differential storage of contaminated sediment in the banks. Three sites record historical nuclear releases in the river and give evidence for long-term retention of particle-reactive long-lived radionuclides. Two sites record only atmospheric global fallout. Only one site, connected to the river groundwater, provides some evidence for desorption of particle-bound contaminants, with a low and constant ¹³⁷Cs activity profile. The history of the releases from the Marcoule spent-fuel reprocessing plant—the main source of artificial radioactivity—provides a reliable chronology of the last 50?years. Sediment grain size and bank topography are important factors in determining where artificial radionuclides are stored, but these two parameters cannot be used alone to determine variations in high concentrations of radionuclides. The chronology of fluvial geomorphic “metamorphosis” during the twentieth Century, especially after 1960, is also a critical factor affecting the spatial variability in sedimentation rates and artificial radionuclide storage; the timing of channel deepening and bank sedimentary accretion interfere with the chronology of major floods and the short period of low discharge during the height of contamination from nuclear liquid effluents. The reach-scale adjustment described in this paper can contribute to determining what the local history may have been. This result has important implications for river management decisions.