Heavy metal inputs in Northern Patagonia lakes from short sediment core analysis

Summary Heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi National Park, Northern Patagonia, Argentina, were determined by INAA. Core dating was performed by measuring natural ²¹⁰Pb and anthropogenic ¹³⁷Cs, and by identification of tephra layers. No evidence was found for the input increase of the trace elements Sb, Ba, Cs, Zn, Co, Hf, Ni, Se, Sr, Ti, U, and V in the lake environment. High As concentrations (up to 250 μg ^. g^-1) were found in relation with the diffusion processes of Mn and Fe oxides. Strong correlation was observed between the Br concentration and organic matter content, but no evidence was found for the relevant increase of Br inputs in recent years. Ag concentrations were found to be enriched in the upper core layers over the baseline values determined for deep layers ranging from 0.1 to 0.2 μg ^. g^-1. Hg concentration profiles were also enriched in the upper core layers over the baseline (from less than 0.07 to 0.2 μg ^. g^-1 for pre-industrial time, to 0.1 to 0.3 μg ^. g^-1 for modern times) but in relation with the increased organic matter content of the sediment.     

210Pb fluxes in sediment layers sampled from Northern Patagonia lakes

Unsupported ²¹⁰Pb fluxes were determined from sediment core inventories in lakes located in Northern Patagonia, Argentina. Total ²¹⁰Pb, ²²⁶Ra, associated with supported ²¹⁰Pb, and ¹³⁷Cs specific activity profiles were measured by gamma-ray spectrometry. Unsupported ²¹⁰Pb fluxes showed very low values when compared to other regions, with a 12 fold variation, ranging from 4 to 48 Bq m^–2.y^–1. The linear correlation observed between the ²¹⁰Pb fluxes and¹³⁷Cs cumulative fluxes in sediment cores sampled from water bodies within a zone with similar precipitation demonstrated that both radioisotopes behave in the same manner in these systems concerning the processes occurred from fallout to sediment deposition, and that there are no appreciable local or regional sources of unsupported ²¹⁰Pb. Positive correlation of ²¹⁰Pb fluxes with organic matter contents of the uppermost sediment core layers was also observed.     

Depth distribution of137cesium,90strontium and210lead in sediments of lake Mondsee,Austria

¹³⁷Cs,⁹⁰Sr and²¹⁰Pb were determined in sediment cores from lake Mondsee /Austria/. The depth profiles show that¹³⁷Cs remains undisturbed, i.e. its distribution corresponds to the fallout deposition pattern.⁹⁰Sr, however, has been transported into the upper sediment layers. In this upper zone nearly constant levels of⁹⁰Sr and also of²¹⁰Pb/²¹⁰Po/were found. Comparison of the⁹⁰Sr and¹³⁷Cs profiles indicates that chemical processes must be responsible for the translocation of⁹⁰Sr as well as²¹⁰Pb, and not bioturbation, i.e. mixing of upper sediment layers by benthic organisms.Dedicated to Prof. Dr. Karl Schlögl, University of Vienna, for his 60th birthday.     

Radiometric dating of sediment records in Kuwait’s marine area

Six sediment cores collected from the Northwestern Arabian/Persian Gulf have been radiometrically dated by ²¹⁰Pb. Three cores were collected from stations within the Kuwait Bay, and three others were collected from stations outside the bay. Two models have been used for ²¹⁰Pb dating of sediment cores, i.e. Constant Flux: Constant Sedimentation (CF:CS) Model and the Constant Rate of Supply (CRS) Model. The average rates were found to vary significantly between 0.16 and 1.00 cm y^?1 for stations outside and within the bay respectively. The variability of the sedimentation rate was essentially physiographic characteristics and variable hydrodynamic condition. In this study, ¹³⁷Cs fallout radiotracer was also used to construct a realistic chronology. It was observed that the ¹³⁷Cs in the entire vertical profile has been continuously contributed by fluvial and atmospheric deposition.     

Natural and artificial radionuclides as a tool for sedimentation studies in the Arctic region

Natural ²¹⁰Pb and artificial ¹³⁷Cs were applied for estimation of sedimentation rates for 14 cores collected in the White Sea, Franz Victoria and Novaya Zemlya troughs. Vertical profiles of ¹³⁷Cs with high resolution (0.5–1 cm) are presented for 18 cores. The agreement between sedimentation rates obtained from ²¹⁰Pb age-dating and ¹³⁷Cs vertical profiles was found. Two maxima of ¹³⁷Cs specific activity were observed in the cores near the North Dvina and Onega mouths, which may be correspond to the Chernobyl accident and global fallouts in early 1960-s.     

Sedimentation rate of the floodplain sediments of the Yamuna river basin (tributary of the river Ganges, India) by using 210Pb and 137Cs techniques

The isotopes ¹³⁷Cs and ²¹⁰Pb were determined in sediment cores originating from the floodplain of the river Yamuna (the largest tributary in the Ganges river system, India). Sampling was done at five locations: Sharanpur (next to the Himalayan foothills), Delhi, Jagmanpur, Hamirpur and Allahabad, where Yamuna meets the Ganges. The rate of sedimentation derived from both techniques, ¹³⁷Cs and ²¹⁰Pb, appears to be quite similar. At the station Sharanpur the highest rate of sedimentation (5.99 cm/y) was noticed, most probably due to deforestation and other human influences in the Himalayan regions, while the lowest rate was observed in Hamirpur (2.48 cm/y). All the five cores studied showed a ¹³⁷Cs peak of 1963, due to radioactive fallout, caused by weapon tests. The three upstream stations (Sharanpur, Delhi and Jagmanpur) showed a ¹³⁷Cs peak due to the Chernobyl event. These measurements reflect that Chernobyl debris have been transferred to the low latitude river system across the Himalayas.     

Studies of the vertical distribution of134Cs,137Cs,238Pu,239, 240Pu,241Pu,241Am and210Pb in ombrogenous mires at mid-latitudes

Six peat cores taken from three unmodified blanket and raised bogs in Ireland were sectioned and analyzed for a range of radionuclides including¹³⁴Cs,¹³⁷Cs,²³⁸Pu,²³⁹Pu,²⁴¹Am, and²¹⁰Pb.¹³⁴Cs and¹³⁷Cs were measured by high resolution gamma-spectrometry, while the transuranium nuclides were determined after chemical separation by alpha-spectrometry.²⁴¹Pu, present on the electroplated discs together with Pu(), was measured directly by low-level liquid scintillation counting. Core chronologies were established by measuring the unsupported²¹⁰Pb component using low energy photon spectrometry (LEPS). From the resulting profiles, relaxation depths and migration rates for the above mentioned radionuclides have been determined and differences in the values of these parameters interpreted.²³⁸Pu/^239,240Pu and²⁴¹Pu/^239,240Pu ratios have been examined carefully and are discussed in some detail. Finally, the contribution from Chernobyl to the total radiocaesium inventory in each core has been established using the¹³⁴Cs/¹³⁷Cs ratio observed in the initial fallout from Chernobyl.     

Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan

The aim of this study was to measure the distribution and inventories of ^239+240Pu, ¹³⁷Cs, and excess ²¹⁰Pb (²¹⁰Pb_excess) in sediment core samples from brackish Lake Obuchi, which is in the vicinity of nuclear fuel facilities in Rokkasho Village, Japan. The inventory of the ^239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq·m^–2, respectively. The inventories of ¹³⁷Cs and ²¹⁰Pb_excess in sediments were 0.83–1.2 kBq·m^–2 and 25–30 kBq·m^–2, respectively. The mean ^239+240Pu/¹³⁷Cs and ²¹⁰Pb_excess/¹³⁷Cs activity ratios were 0.23 and 28, respectively. The^239+240Pu/¹³⁷Cs activity ratios were approximately 13–24 times the ratio expected from global fallout. The inventories of ^239+240Pu and ²¹⁰Pb in sediments were higher than the inventory expected from atmospheric fallout, but the ¹³⁷Cs inventory was significantly lower than expected.This revised version was published online in November 2005 with corrections to the Cover Date.     

The <Superscript>137</Superscript>Cs distribution in sediment profiles from the Yangtze River estuary: a comparison of modeling and experimental results

It has been generally accepted when estimating sedimentation rates using the ¹³⁷Cs dating method that the position of the ¹³⁷Cs maximum in a sediment profile represents the year 1963. In this paper we validated this approach by developing a model in which the annual ¹³⁷Cs global fallout flux for the Yangtze River estuary was established on the basis of the Tokyo flux corrected for precipitation rates observed in Shanghai. As the ¹³⁷Cs maxima in the sediment deposition profiles depend on the sedimentation rates, the sub-sampling intervals were calculated accordingly. Higher measured than the calculated values were found in some cores, what may be due to fluctuating sedimentation rates and an additional deposition of ¹³⁷Cs from land-based sources. The study provides useful information on the reliability of the measured ¹³⁷Cs maxima in sediment profiles frequently used for dating of sediments in marine (coastal regions, open seas) as well as in terrestrial (lakes) environments.     

137Cs and 210Pb radionuclides in open and closed water ecosystems

The aim of this study was to determine the level of radionuclide concentration in sediment cores in two different water ecosystems; one closed and one open. Based on this data the changes in these ecosystems were interpreted. Two sediment cores from the Dobczyce reservoir and the Smreczynski Staw Lake were collected and divided into 1 cm thick sub-samples. The samples were air dried and homogenized. The ¹³⁷Cs and ²¹⁰Pb (²¹⁰Pb_sup, ²¹⁰Pb_total, ²¹⁰Pb_uns) concentrations were measured using gamma and alpha spectrometry. Results showed that the ¹³⁷Cs concentration in the Dobczyce reservoir is lower than in the Smreczynski Staw Lake. Total ²¹⁰Pb concentration in the Dobczyce reservoir was around 70 Bq kg^?1 and in the Smreczynski Staw Lake was about 500 or 1,200 Bq kg^?1 with the decreasing tendency in the sediment core. Sediments are very important constituents of water ecosystems. In spite of the young age of the Dobczyce reservoir, the ¹³⁷Cs and ²¹⁰Pb radionuclides were very useful in understanding of the processes which have taken place in these ecosystems. The estimated sedimentation rate indicated such processes as regular sedimentation, mixing of sediments or floods. In the Smreczynski Staw Lake the changes have reflected the changes which took place in the Tatra Mountains.     

Geochemistry of marine sediments from inner Ría de Vigo (NW Spain)

Two sediment cores were recovered in San Simón Bay (NW Spain) in order to establish sediment accumulation rates by ²¹⁰Pb and ¹³⁷Cs dating and to reconstruct metal pollution history. Sediment composition was determined by X-ray Fluorescence. A main lithogenic origin was shown up. Grain size conditions radionuclide activities and element concentrations. Fine grained sediments concentrate pollutants and showed higher activities. Radionuclide profiles are affected by diagenetic processes and sedimentary disturbances, but a temporal framework could be obtained for the intertidal area, where the anthropogenic inputs of Cu, Pb and Zn started several decades ago.     

Sedimentation rate in the Sungai Linggi estuary using excess 210Pb and 137Cs

The purpose of this study was to estimate the sedimentation rate in the Sungai Linggi estuary using the constant initial concentration of unsupported or excess ²¹⁰Pb model and verified with ¹³⁷Cs method. Five sediment cores were collected on 25 January 2011 using gravity corer with the inner tube of 50 cm length and 7.5 cm diameter. The total ²¹⁰Pb activities in the sediment cores profile at all sampling stations were varied and upper than those obtained for supported ²¹⁰Pb i.e. ²²⁶Ra, indicated disequilibrium among ²¹⁰Pb and its grandparents in the ²³⁸U decay series. Meanwhile, the lower ¹³⁷Cs activities were observed at all sampling stations due to no significant sources of ¹³⁷Cs releases were transferred into Malaysian marine. The estimation of sedimentation rate indicated the agreement of ²¹⁰Pb and ¹³⁷Cs method with a general presence of deep mixing in the Sungai Linggi estuary. Therefore, the apparent sedimentation rates calculated from ²¹⁰Pb profiles generally reflect the true value with the range from 0.70 to 1.97 cmyr^?1. High sedimentation rate was observed at some sampling stations which are located in river channel, estuary and closer to mainland. This suggested that land-use development, agriculture activities, channelization etc. introduced a large amount of sediment loaded into those areas.     

Radiochronology of sediments from the Mediterranean Sea using natural210Pb and fallout137Cs

The²¹⁰Pb and¹³⁷Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct -ray spectroscopy. Sedimentation rates were derived for all locations using the²¹⁰Pb data. The rates range from 1.39±0.12 cm · y^–1 (0.50±0.04 g · cm^–2 · y^–1) to 0.08±0.01 cm · y^–1 (0.039±0.003 g · cm^–2 · y^–1). Except for one core, the¹³⁷Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of²¹⁰Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported²¹⁰Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm^–2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean.     

Evaluation of 239+240Pu, 137Cs and natural 210Pb fallout in agricultural upland fields in Rokkasho, Japan

The background distributions of ^239+240Pu and ¹³⁷Cs fallout in agricultural soil were investigated in Rokkasho where Japan's first commercial nuclear fuel reprocessing plant is now being constructed. The mean inventories of ^239+240Pu and ¹³⁷Cs in three fields with non-yam-cultivation history were 116 Bq·m⁻² and 3.4 kBq·m⁻², respectively. The mean atomic ratio of ²⁴⁰Pu/²³⁹Pu for all studied fields was 0.18±0.04, and was similar to that of global fallout. The ^239+240Pu concentrations correlated very well with ¹³⁷Cs (r = 0.97) in spite of heavy disturbance of the soil, and the activity ratio of ^239+240Pu/¹³⁷Cs was 0.037±0.007, which is a typical value for global fallout. These results showed that the nuclides had similar behavior in agricultural upland fields in Rokkasho. Since ²¹⁰Pb is steadily deposited from the atmosphere to the land, this nuclide could be an index for the degree of disturbance of a field and of soil lost from the field. The ratio of excess ²¹⁰Pb inventory in the soil to the equivalent inventory of atmospheric ²¹⁰Pb deposition was 96%, and indicated that soil was not lost from the cultivated fields. This revised version was published online in July 2006 with corrections to the Cover Date.     

Historical variations of Bera Lake (Malaysia) sediments geochemistry using radioisotopes and sediment quality indices

The Bera Lake basin is a lacustrine mire system and the largest natural lake in Peninsular Malaysia. Three cores were collected from the lake sediments in order to assess sediment quality and ecological risks for aquatic life and human health. An index analysis approach (C _f , C _d , E _r , and IR) and fallout ²¹⁰Pb and ¹³⁷Cs radioisotopes were applied to assess the impacts of environmental evolutionary changes. Sediment chronology was determined using the Constant Rate of Supply model with the resultant ages verified by ¹³⁷Cs horizons. Although the general contamination factors indicate low risk conditions in Bera Lake the risks associated with individual layers ranged from moderate to considerable. Five deforestation phases can be identified in the dated sediment cores with distinct variations in heavy metal influxes since 1972. These phases are in excellent agreement with the dates of land clearance and development projects undertaken over the past four decades. This study has highlighted the capability of contamination factors and chronological methods in environmental evolutionary studies where catchments have experienced extensive land use changes. The destiny of heavy metal influxes into a lake can also be revealed using this methodology.     

Natural and anthropogenic consequences of tropical forest soils in Northern Peru using environmental radionuclides as radiotracers

Environmental radionuclides (⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra) were determined in soils under semi-arid stands, a transition area from thorn to deciduous forest in El Angolo, and heath stands in the Alto Mayo in Northern Peru in order to elucidate their activity level in soil, and to trace underground environment in remote areas of little anthropogenic intervention. Anthropogenic ¹³⁷Cs was only found in the uppermost portion of the soils in small amount, whereas the ²¹⁰Pb activity was exceptionally high at the soil surfaces in a tropical stand of Alto Mayo. The results suggest a fallout nuclide, ²¹⁰Pb, having been transported from local source(s) not to be specified yet.     

Sedimentation rates,nitrogen and phosphorus retentions in the largest urban Lake Donghu,China

Summary Sediment core samples were collected in the largest urban Lake Donghu (Stations I and II) in China, and the activities of ²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs were measured by gamma-ray spectrometry. The sedimentation rates, calculated by ²¹⁰Pb constant rate of supply (CRS) model, ranged from 0.11 to 0.65 (average 0.39) cm^. y^-1at Station I, and from 0.21 to 0.78 (average 0.46) cm^. y^-1at Station II. Sedimentation rate calculated by ¹³⁷Cs as a time marker was 0.55 cm^. y^-1at Station II. Based on the average sedimentation rate, we obtained 769 and 147 t^. y^-1for nitrogen and phosphorus retentions in Lake Donghu sediments, respectively.     

Vertical Profiles, Inventories, and Activity Ratios of 239+240Pu and 137Cs in Sediments from Sagami Bay, Western Northwest Pacific Margin

Marine sediment cores were taken from Sagami Bay of the western Northwest Pacific and analyzed for ^239+240Pu and ¹³⁷Cs activities. A significant correlation was observed between ^239+240Pu and ¹³⁷Cs activities in sediment cores, i.e., their vertical profiles. The measured activities which were used to obtain the inventories of ^239+240Pu and ¹³⁷Cs in the sediment column, showed large variations, ranging from 36 to 474 MBq/km² for ^239+240Pu and 49 to 652 MBq/km² for ¹³⁷Cs. ^239+240Pu inventories in the sediment from one region in the Bay, Sagami Nada were 5–10 times greater than those predicted from atmospheric global fallout 42 MBq/km² at the same latitude. On the other hand, ¹³⁷Cs inventories, with a mean value of 297±168 MBq/km², were much less than predicted, 2040 MBq/km². The activity ratios of ^239+240Pu/¹³⁷Cs obtained, with a mean of 0.65±0.17, were significantly greater than the ratio predicted from fallout, 0.021. Furthermore, there was a clear relationship between both ^239+240Pu and ¹³⁷Cs inventories and the water content, indicating that higher inventories may be attributed principally to concentration in, and scavenging by, fine-grained particles.     

Dating of Black Sea sediments from Romanian coast using natural 210Pb and fallout 137Cs

The sediment samples collected near the shore from Romania were used for the determination of levels of natural ²¹⁰Pb, ²²⁶Ra and fallout ¹³⁷Cs radionuclides. The sediment samples were dried and ground to a fine powder. Airtight sealed samples were counted by gamma-spectrometer with 110 cm³ well-type HPGe detector for one week each. By using the isotopic analysis results, sediment accumulation rate was determined. A sedimentation rate of 0.20±0.01 cm^.y^-1 was determined using ²¹⁰Pb method and 0.15±0.03 cm^.y^-1 using ¹³⁷Cs isotope. Fallout peak from Chernobyl reactor accident, as well as the peaks due to nuclear tests, act as time markers.     

Elemental composition of lichens at Nahuel Huapi National Park,Patagonia, Argentina

Five species of epiphytic lichens were sampled from urban and periurban areas of Bariloche, a non industrial city located on the East side of the Nahuel Huapi National Park, North-Western Patagonia, Argentina, and from pristine areas of the Park. Each individual lichen was analyzed using Instrumental Neutron Activation Analysis. The results of the analysis showed high concentrations of lithophile elements, with very good correlations among them. The relative concentration of these elements in all lichen species is in good agreement with the elemental composition of sediments collected in the Park. Elemental concentrations which are not related to detritical inputs are also presented.