Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

137Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

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     

The use of 137Cs as a tracer in an erosion study in south limburg (the Netherlands) and the influence of chernobyl fallout

The ¹³⁷Cs radioactivity of soils was used as a tracer of soil erosion in a catchment in the Netherlands: 143 samples were analysed to map the ¹³⁷Cs redistribution using geostatistical interpolation methods. Caesium-137 activities on grassland are significantly higher than on arable land. Also, ¹³⁷Cs activities on waning slopes are higher and activities on steep slopes are lower. The soil erosion estimates, derived from the ¹³⁷Cs data, are used to validate the USLE erosion model. The recent Chernobyl nuclear accident also contributed to the ¹³⁷Cs activity. However, the Chernobyl input of ¹³⁷Cs, with a constant ratio of 1.765:1 to ¹³⁴Cs, cannot be used as a tracer of soil erosion. Because of the rapid decay of ¹³⁴Cs, we will not be possible to separate the sources of ¹³⁷Cs in the near future in areas significantly influenced by Chernobyl fallout and in these areas ¹³⁷Cs can no longer be used as a soil erosion tracer.     

Sediment and trace element depositional history from the Ajkwa River estuarine mangroves of Irian Jaya (West Papua), Indonesia

Radiotracer ²¹⁰Pb and contaminant copper were used to estimate sediment accumulation rates in 4 cores from the Ajkwa River estuary and mangrove tidal channels in western Irian Jaya. Mass accumulation rates (4.5–13 kg dry wt m⁻² yr⁻¹) were within the envelope of expectations for a region of high rainfall, great river catchment relief, and rapid tectonic uplift of mountains. Copper accumulation rates were enhanced 40 fold in surface sediments, compared to pre-1950 sections of the sediment cores. These recent sediments with enhanced copper concentrations come from Freeport Indonesia mine tailings over the last 27 years. Variations in sediment core profiles of Al, Fe, and organic carbon were small, indicating no great change in bulk sediment composition. Sulfur concentrations decline toward the sediment surface, suggesting a decline in rates of microbial sulfate reduction. Enhanced sediment copper concentrations will be a useful tracer of sediment dispersal from the Ajkwa River estuary along this coast.     

Establishing a high-resolution surface sediment chronology with multiple dating methods – Testing 137Cs determination with Nurmijärvi clastic-biogenic varves

The uppermost 50 cm of sediments from the 23 m deep lacustrine basin of Nurmijärvi, a lake in south-central Finland, are composed of the clastic-biogenic type of varves. We use multiple dating methods to render a sediment chronology that is as precise and accurate as possible for future paleoenvironmental research on this high-fidelity sedimentary archive. The 250-year-long varve chronology contains a chronological error of ±2%, as estimated based on repeated varve counts. The varve-based chronology was verified with the vertical distribution of ¹³⁷Cs by comparing variations in the paleomagnetic relative declination of the surface sediments with instrumental observations and a calculated representation of declination features in Finland. A comparison of the sediment cesium content using two gamma counters, different sediment pretreatments, and normalization of the ¹³⁷Cs concentration with masses and accumulation rates of different sediment components revealed that the AD 1986 fallout peak from the Chernobyl accident is the dominant feature in the studied sediments, regardless of the sample pretreatment or normalizing procedure. The vertical distribution of the AD 1986 peak in sediments with clastic-biogenic varves is fairly narrow, thus providing an accurate age-depth marker for the recent deposits. However, the Nurmijärvi section also reveals a ca. 10-year-long period of catchment-to-basin ¹³⁷Cs mobilization and redeposition after the AD 1986 fallout, as well as significant downwards diffusion of the Chernobyl-derived cesium in the sediment. This study highlights the ways in which the quality of surface sediment chronology needs to be considered and secured prior to comparisons between paleoproxy records and instrumental observations.     

A detailed chronology of the sedimentation in the Danube abyssal fan records the major episodes of the late-Holocene Black Sea evolution

We have constructed a high-resolution Bayesian sedimentation model spanning the last 5500 years based on 25 AMS radiocarbon dated sediments of bulk organic matter (OM) sampled from the NW Black Sea anoxic waters of the continental slope. The corrections for the ¹⁴C ages due to marine reservoir effect (MRE) and detritus organic carbon are correlated with exogenous information such as ²¹⁰Pb dating, metallurgy pollution and human-induced soil erosion, highlighting the Danube influence on the geochemistry and chronology of the NW Black Sea sediments through the input of terrigenous organic matter. The results show excellent agreement with some of the previous studies, supporting a total age offset for the bulk OM of 60 years as MRE and 580 years as detritus organic carbon influence. The revisited chronology pinpoints the first and second invasion of the coccolithophores Emiliania huxleyi at 2524 ± 87 and 625 ± 65 years cal. BP. Sedimentation rate shows an increase of about three times with the starting of the late Medieval, which correspond to the highest observed sediment discharge of the Danube as are considered the last 500-300 years. This type of high-resolution sedimentation model is an important step for constructing the carbon budget in bottom waters of variable oxygen concentration.     

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

Landscape‐scale controls on the spatial distribution of caesium 137: A study based on an airborne geophysical survey across Northern Ireland

The spatial distribution of ¹³⁷Cs across the landscape and the processes controlling its redistribution are of interest because (i) ¹³⁷Cs has been widely used to quantify the movement of soil and sediments and (ii) substantial fallout of ¹³⁷Cs after the Chernobyl accident has led to contamination of foodstuffs in some places. A high‐resolution airborne geophysical radiometric survey of Northern Ireland has provided an opportunity to study the distribution and possible redistribution of ¹³⁷Cs. The ¹³⁷Cs activity (recorded at 1·2 million points) is distributed in a series of bands oriented approximately 160° and 115° clockwise from north. Geostatistical analysis of the data shows a strong, short‐range structure (correlation ranges between 0·6 and 8 km) in ¹³⁷Cs activity across the vast majority of the region; the spatial distribution shows association with a published, coarse‐scale depositional pattern of ¹³⁷Cs from Chernobyl. Two indices of land form derived from a digital elevation model, namely compound topographic index and the length–slope factor of the Revised Universal Soil Loss Equation, account for only 3% of the variance in ¹³⁷Cs activity. In contrast, soil type and land cover in combination (including their interaction) account for 20% of the variance. In areas that received moderate fallout from Chernobyl, soil type alone accounts for a substantial proportion of the spatially correlated ¹³⁷Cs activity. We attribute this to each soil type having a fairly uniform radiocaesium interception potential that differs from those of other soil types and that this potential controls the vertical migration of ¹³⁷Cs. Over the granitic Mourne Mountains there is a strong spatial cross‐correlation between ¹³⁷Cs activity and airborne estimates of soil potassium, suggesting that the latter provides a measure of the soil's radiocaesium interception potential; this is probably dominated by the quantity of the mineral illite. Copyright © 2010 John Wiley & Sons, Ltd. and British Geological Survey     

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.     

ENAA Studies of pollution in anoxic Black Sea sediments

The vertical distributions of five potential pollutants - Zn, As, Br, Sn, and Sb - were determined via epithermal neutron activation in the upper 50 cm of unconsolidated sediments from the Black Sea, which were collected 600 m below sea surface. This analysis demonstrated increasing concentrations towards the upper limits of sediments, which were greater than alert concentrations in the case of As and Br, and in accordance with Romanian Environment Regulations. The utilization of Chernobyl ¹³⁷Cs as a time marker allowed for dating of this region to the last 100 years.     

The fate of Chernobyl radiocesium in the River Öre catchment,northern Sweden

A¹³⁷Cs-balance for the catchment of the River Öre in central northern Sweden which received about 30 kBq m^–2 of radiocesium from the Chernobyl accident was calculated for the period 1986–1991. Altogether, slightly less than 10% of the total deposition in the catchment was estimated to be exported from the terrestrial parts during this period of time. More than 90% of this loss is transported with the River Öre to the outer sea of the Gulf of Bothnia. The retention in Lake Örträsket which is the only lake along the river course and the Öre Estuary outside the river mouth was thus slightly less than 10%. Nearly all of the radiocesium deposited in the lake is permanently retained in the sediments and successively covered with less radioactive sediment. A considerable export of radiocesium from the estuary to the outer sea takes place due to resuspension and subsequent transport by wind and wave generated currents.     

The application of caesium‐137 measurements to investigate floodplain deposition in a large semi‐arid catchment in Queensland,Australia: a low‐fallout environment

Floodplains comprise geomorphologically important sources and sinks for sediments and associated pollutants, yet the sedimentology of large dryland floodplains is not well understood. Processes occurring on such floodplains are often difficult to observe, and techniques used to investigate smaller perennial floodplains are often not practical in these environments. This study assesses the utility of ¹³⁷Cs inventory and depth‐profile techniques for determining relative amounts of floodplain sedimentation in the Fitzroy River, northeastern Australia; a 143 000 km² semi‐arid river system. Caesium‐137 inventories were calculated for floodplain and reference location bulk soil cores collected from four sites. Depth profiles of ¹³⁷Cs concentration from each floodplain site and a reference location were recorded. The areal density of ¹³⁷Cs at reference locations ranged from 13 to 978 Bq m^–2 (0–1367 Bq m^–2 at the 95% confidence interval), and the mean value ± 2 (standard error of the mean) was 436 ± 264 Bq m^–2, similar to published data from other Southern Hemisphere locations. Floodplain inventories ranged from 68 to 1142 Bq m^–2 (0–1692 Bq m^–2 at the 95% confidence interval), essentially falling within the range of reference inventory values, thus preventing calculation of erosion or deposition. Depth‐profiles of ¹³⁷Cs concentration indicate erosion at one site and over 66 cm of deposition at another since 1954. Analysis of ^239+240Pu concentrations in a depositional core substantiated the interpretation made from ¹³⁷Cs data, and depict a more tightly constrained peak in concentration. Average annual deposition rates range from 0 to 15 mm. The similarity between floodplain and reference bulk inventories does not necessarily indicate a lack of erosion or deposition, due to low ¹³⁷Cs fallout in the region and associated high measurement uncertainties, and a likely influence of gully and bank eroded sediments with no or limited adsorbed ¹³⁷Cs. In this low‐fallout environment, detailed depth‐profile data are necessary for investigating sedimentation using ¹³⁷Cs. Copyright © 2009 John Wiley & Sons, Ltd.     

Distribution of 137Cs in the Lena River estuary-Laptev Sea system.

Surface sediment samples in the Laptev Sea have average 137Cs content of 7.1 Bq kg(-1), a value intermediate between that of the western Kara Sea (23 Bq kg(-1) and the East Siberian Sea (4.2 Bq kg-'). Both surface sediment content and sediment inventory of 137Cs in the Laptev Sea sediments show significant variability, and the influence of a variety of environmental factors.137Cs concentrations in the Laptev Sea surface sediments range from 0.8 to 16 Bq kg(-1). There is a marked increase in 137Cs content of surface sediment samples collected near the Lena River delta, and a local enrichment in the 137Cs inventories at these sites is also evident. Fine-grained mixed-layer illite/ smectite rich sediments in the estuary provide effective adsorption sites to fix 137Cs, in spite of desorption processes associated with low salinities in estuarine mixing. The Lena River-Laptev Sea mixing zone is a major site of sea-ice production. River and shelf sediments are incorporated into sea-ice formed in this region (Holmes and Creager, 1974). The irregular 137Cs activity profiles of the Lena River estuary cores indicate disturbance or removal of 137Cs-laden sediments via sea-ice related processes. Lena River and Estuary sediments may have served as a secondary source (i.e. other than direct fallout) of 137Cs in sea-ice. North-east of the Lena River estuary, sediment contains a thin layer of 137Cs-bearing material over an erosion surface. The 137Cs-laden surface layer may be the result of transient deposition of estuarine sediments being delivered by sea-ice or spring floods.     

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.     

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.     

Assessment of sediment yield in a small karst catchment by using 137Cs tracer technique

There is very thin soil layer in karst rocky desertification areas in Southwest China,sediment deposition and sediment yield in the karst area affects the development of vegetation greatly.In the present study,the ¹³⁷Cs technique was used to assess the rate of sediment deposition and sediment yield in a small karst catchment.The ¹³⁷Cs inventory within the depression varied between 800 m^-2 and 2,200 Bq m^-2,with the mean value of 1,500.1 Bq m^-2.The ¹³⁷Cs reference inventory at a nearby reference site was 805.9 Bq m^-2.It could be inferred to that sediment deposition had occurred in the catchment.The mean depth of sediments deposition in the depression was 6 cm and the deposition rate was approximately 0.13 cm yr^-1.The analysis of the topographic characteristics of the catchment revealed that the sediment deposition occurred mainly at the lower part of the small catchment.Although,there was a sinkhole in the depression,little sediment had drained out with runoff through the sinkhole,because the local people built ridges around the sinkholes for storing water.According to this,sediment yield rate in the small catchment was estimated to be approximately 19.25 to 27.5 t km^-2 yr^-1,and the extremely low sediment yield was maybe the main obstacle to vegetation restoration in karst rocky desertification areas.     

Modern (<100 years) sedimentation in the Taiwan Strait: Rates and source-to-sink pathways elucidated from radionuclides and particle size distribution

A large number of sediment cores collected during 2005-2010 from the Taiwan Strait were analyzed for radionuclides (²¹⁰Pb, ¹³⁷Cs and ⁷Be) to elucidate sedimentation dynamics in this all-important gateway linking two largest marginal seas in the western Pacific (namely, the South China Sea and the East China Sea). Apparent sediment accumulation rates derived from ²¹⁰Pb and ¹³⁷Cs profiles vary from <0.1 to >2 cm/yr, averaging ∼0.4 cm/yr and showing a spatial pattern closely related to hydrodynamics and sediment source-to-sink pathways. Spatial-temporal variation of ⁷Be activity in surface sediments off Taiwan’s west coast indicates episodic deposition of flood layers and their mobility from river estuaries toward the north. In conjunction with particle size distribution in surface sediments and the structure of sediment strata revealed by sub-bottom echo images; the radionuclide data can be used to outline three different sediment source-to-sink dispersal systems. Based on sediment loads of surrounding rivers and the distribution of sediment accumulation rates, lateral transport is required to account for the budget and size distribution of sediments in the strait.     

Can channel banks be the dominant source of fine sediment in a UK river?: an example using 137Cs to interpret sediment yield and sediment source

Cultivated fields have been shown to be the dominant sources of sediment in almost all investigated UK catchments, typically contributing 85 to 95% of sediment inputs. As a result, most catchment management strategies are directed towards mitigating these sediment inputs. However, in many regions of the UK such as the Nene basin there is a paucity of sediment provenance data. This study used the caesium‐137 (¹³⁷Cs) inventories of lake and floodplain cores as well as the ¹³⁷Cs activities of present day sediment to determine sediment provenance. Sediment yields were also reconstructed in a small lake catchment. Low ¹³⁷Cs inventories were present in the lake and floodplain cores in comparison to the reference inventory and inventories in cores from other UK catchments. Caesium‐137 activities in the present day sediments were low; falling close to those found in the channel bank catchment samples. It was estimated that 60 to 100% of the sediment in the Nene originated from channel banks. Pre‐1963 sediment yields were approximately 11.2 t km^?2 yr^?1 and post‐1963 was approximately 11.9 t km^?2 yr^?1. The lack of increased sediment yield post‐1963 and low sediment yield is unusual for a UK catchment (where a yield of 28 to 51 t km^?2 yr^?1 is typical for a lowland agricultural catchment), but is explained by the low predicted contribution of sediment from agricultural topsoils. The high channel bank contribution is likely caused by the river being starved of sediment from topsoils, increasing its capacity to entrain bank material. The good agreement between the results derived using cores and recently transported sediments, highlight the reliability of ¹³⁷Cs when tracing sediment sources. However, care should be taken to assess the potential impacts of sediment particle size, sediment focusing in lakes and the possible remobilization of ¹³⁷Cs from sedimentary deposits. Copyright © 2016 John Wiley & Sons, Ltd.     

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.