scholarly journals Reconstruction of the Long-Term Dynamics of Particulate Concentrations and Solid–Liquid Distribution of Radiocesium in Three Severely Contaminated Water Bodies of the Chernobyl Exclusion Zone Based on Current Depth Distribution in Bottom Sediments

Land ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 29
Author(s):  
Alexei Konoplev ◽  
Gennady Laptev ◽  
Yasunori Igarashi ◽  
Hrigoryi Derkach ◽  
Valentin Protsak ◽  
...  
Keyword(s):  
Bottom Sediments ◽  
Sediment Cores ◽  
Temporal Trends ◽  
Water Bodies ◽  
Contaminated Water ◽  
Exclusion Zone ◽  
Liquid Distribution ◽  
Diffusional Model ◽  
Solid Liquid

Given the importance of understanding long-term dynamics of radionuclides in the environment in general, and major gaps in the knowledge of 137Cs particulate forms in Chernobyl exclusion zone water bodies, three heavily contaminated water bodies (Lakes Glubokoe, Azbuchin, and Chernobyl NPP Cooling Pond) were studied to reconstruct time changes in particulate concentrations of 137Cs and its apparent distribution coefficient Kd, based on 137Cs depth distributions in bottom sediments. Bottom sediment cores collected from deep-water sites of the above water bodies were sliced into 2 cm layers to obtain 137Cs vertical profile. Assuming negligible sediment mixing and allowing for 137Cs strong binding to sediment, each layer of the core was attributed to a specific year of profile formation. Using this method, temporal trends for particulate 137Cs concentrations in the studied water bodies were derived for the first time and they were generally consistent with the semiempirical diffusional model. Based on the back-calculated particulate 137Cs concentrations, and the available long-term monitoring data for dissolved 137Cs, the dynamics of 137Cs solid–liquid distribution were reconstructed. Importantly, just a single sediment core collected from a lake or pond many years after a nuclear accident seems to be sufficient to retrieve long-term dynamics of contamination.

Radiocesium wash-off, river transport and redistribution in fluvial system after the Fukushima Dai-ichi nuclear power plant accident

2020 ◽  
Author(s):  
Aleksei Konoplev ◽  
Yoshifumi Wakiyama ◽  
Toshihiro Wada ◽  
Valentin Golosov ◽  
Maxim Ivanov ◽  
...  
Keyword(s):  
Bottom Sediments ◽  
Water Samples ◽  
Sediment Cores ◽  
Speciation Analysis ◽  
Water Bodies ◽  
Fukushima Accident ◽  
River Transport ◽  
Dam Reservoirs ◽  
Extreme Flood

<p>Processes responsible for long-term changes in environmental radioactivity after the Fukushima accident are currently high on the agenda. Dynamics of particulate and dissolved radiocesium (r-Cs) has been studied on a number of water bodies, namely Abukuma River, Niida River and Maeda River, the dam reservoirs of Yokokawa (Ota River), Sakashita (Kuma River), Ogaki (Ukedo River) and Shinobu (Abukuma River) and four heavily contaminated irrigation ponds in Okuma town (Inkyozaka, Suzuuchi, Funasawa, Kashiramori). Water samples were collected for dissolved and particulate r-Cs analysis at multiple sites for these water bodies. Wash-off from slopes of contaminated catchments and river transport are key long-term pathways for radionuclide dispersal from contaminated areas after the Fukushima accident. The climate and geographical conditions for the Fukushima Prefecture of Japan are characterized by relatively high annual precipitation (1300-1800 mm/year) and steep slopes which promote higher erosion and higher particulate r-Cs wash-off. At the same time, the r-Cs distribution coefficient <em>K<sub>d</sub></em> in Fukushima rivers was found to be at least an order of magnitude higher than the corresponding values for Chernobyl-derived r-Cs and r-Cs resulting from nuclear weapon tests (NWT) in European rivers. The normalized dissolved wash-off coefficient for Fukushima river watersheds, based on the measured dissolved r-Cs activity concentrations was found to be 1-2 orders of magnitude lower than those for Chernobyl and NWT fallout. In the irrigation ponds r-Cs showed a persistent behavior and was characterized by regular seasonal variations: r-Cs concentrations tend to grow during summer and decrease during winter. Speciation analysis for Okuma ponds showed a much higher exchangeability of r-Cs in bottom sediments than catchment soils. Several methodologies to collect water samples and to separate the particulate and dissolved fractions have been used and showed comparable results for all water bodies under study. For all rivers, reservoirs, and ponds higher values of <em>K<sub>d</sub></em>(r-Cs) have been confirmed when compared with Chernobyl-derived r-Cs in European water bodies. Some observations demonstrated remobilization of r-Cs at river mouths compared to upstream sections which could be explained by the change of river water hydrochemistry from upstream to the mouth, specifically a substantial increase in the concentration of major r-Cs competing cations for selective sorption sites on the suspended matter. Some dam reservoirs and ponds were subjected to integrated suspended sediment sampling. For the dam reservoirs, the particulate r-Cs activity concentration has been found to be water depth-dependent. Sediment cores collected at eight sites along the Abukuma river floodplain in 2018 and during October-November 2019, right after Typhoon Hagibis occurred in the middle of October 2019, demonstrated substantial redistribution of r-Cs due to erosion and redeposition during heavy rainfall and extreme flood. Bottom sediments coring in the dam reservoirs allowed estimation of the average sedimentation rate in the reservoirs and the rate of r-Cs accumulation. This research was partially supported by the Japan Society for the Promotion of Science (JSPS), Grant-in-aid for Scientific Research (B) (18H03389), bilateral project No. 18-55-50002 of Russian Foundation for Basic Research (RFBR) and JSPS.</p>

Artificial radionuclides, mercury, lead, and oil components in sediment cores as markers of the Anthropocene Epoch

2021 ◽  
Author(s):  
Yury Fedorov ◽  
Andrey Kuznetsov ◽  
Irinageo Dotsenko ◽  
Anna Mikhailenko
Keyword(s):  
Bottom Sediments ◽  
Working Group ◽  
Anthropogenic Impact ◽  
Sediment Cores ◽  
Water Bodies ◽  
Sedimentation Rates ◽  
Sea Of Azov ◽  
The Holocene ◽  
The Sea Of Azov ◽  
Oil Components

<p>The majority of researches of the Working group on the ‘Anthropocene’ of the International Commission on Stratigraphy (ICS) voted for the recognition of the Anthropocene as a formal chrono-stratigraphic unit characterized by profound alterations of several conditions and processes on Earth by human impact. It is also proposed to place its beginning and the end of the Holocene epoch in the mid-20th century, coinciding with the launch of nuclear weapon tests [1]. In contemporary sediment cores of the Sea of ​​Azov, the Don and the Kuban rivers, we will distinguish a "layer of anthropogenic impact", meaning the layer containing considerable quantities of technogenic material and (or) pollutants [2]. To reveal the chronology of its formation, its thickness, and boundaries, it is proposed to use the results of layer-by-layer determining of the Cs-137 and Am-241 specific activities, as well as the content of oil components, lead and mercury in the bottom sediments of the water bodies. The upper Cs-137 peak formed due to the Chernobyl accident and sometimes the lower Cs-137 and Am-241 peaks related to the global radioactive fallout in the 1950s and 1960s have been detected [3]. The decrease of mercury, lead, and oil components concentrations from the upper to the lower parts of sediment cores has also been observed. The results of analysis of technogenic radionuclides and priority pollutants distribution have proved that since the 1950s and 1960s in the bottom sediments of the Sea of ​​Azov and water bodies of its basin the “layer of anthropogenic impact" has been being formed. Its thickness varies from 20 to 50 cm and may even exceed 50 cm in areas characterized by high sedimentation rates. It has been found out that in the mid-20th century the ecosystem of the Sea of ​​Azov began to suffer from intense anthropogenic pressure, which reached its maximum in the 1970s and 1980s. It is proposed to consider the studied pollutants (technogenic radionuclides, mercury, lead, and oil components) as a possible set of priority markers of the Anthropocene epoch. The Holocene - Anthropocene boundary should be placed at the base of the identified “layer of anthropogenic impact”.</p><p> </p><p>The research was supported by the Russian Foundation for Basic Research, project no. 19-05-50097.</p><p> </p><p>Bibliography</p><p>[1] Working Group on the ‘Anthropocene’. Results of binding vote by AWG. http://quaternary.stratigraphy.org/working-groups/anthropocene/ (last accessed 17 January 2021).</p><p>[2] Kuznetsov A.N., Fedorov Yu.A., and Yaroslavtsev V.M. (2018) Technogenic and natural radionuclides in the bottom sediments of the Sea of Azov: regularities of distribution and application to the study of pollutants accumulation chronology. IOP Conference Series: Earth and Environmental Science 107, 012063.</p><p>[3] Fedorov Yu.A., Kuznetsov A.N., and Trofimov M.E. (2008) Sedimentation rates in the Sea of Azov inferred from Cs-137 and Am-241 specific activity. Doklady Earth Sciences, vol. 423, no. 1, pp. 1333-1334.</p>

Natural-Analog Studies for Partial Validation of Conceptual Models of Radionuclide Retardation at the Wipp

1990 ◽  
Vol 212 ◽  
Author(s):  
David B. Ward ◽  
Douglas G. Brookins ◽  
Malcolm D. Siegel ◽  
Steven J. Lambert
Keyword(s):  
Flow Model ◽  
Solution Chemistry ◽  
Liquid Distribution ◽  
Waste Isolation Pilot Plant ◽  
Natural Analog ◽  
Long Term Stability ◽  
Solute Interactions ◽  
Solid Liquid ◽  
Analog Study

ABSTRACTTransport by groundwater within the Culebra Dolomite, an aquifer above the Waste Isolation Pilot Plant (WIPP), is the most probable mechanism for long-term release of radionuclides to the accessible environment. Radionuclides could be retarded by sorption if the groundwater is exposed to sufficient amounts of fracture-lining clays. In this natural-analog study, distributions of U and trace metals have been examined to constrain the strength of clay/solute interactions within the Culebra.Uranium solid/liquid distribution ratios, calculated from U concentrations of groundwaters and consanguineous fracture-filling clays, range from ∼80 to 800 mℓ/g and imply retardation factors of 60 to 500 using a fracture-flow model. Retardation factors inferred from uranium-series disequilibria and 14C ages in Culebran groundwaters alone are much lower (∼10), implying that clays may contain a significant unreactive component of U. Such a possibility is corroborated by Rb/Sr ages; these imply long-term stability of the clays, with resetting occurring more than 250 Ma ago. Factor analysis and mass-balance calculations suggest, however, that Mg-rich clays are dissolving in Pleistocene-age groundwaters and/or are converting to Na-rich smectites, and that B and Li are taken up from the water by the clays. Apparently, the solution chemistry reflects gradual equilibration of clays with groundwater, but thus far the bulk of the clays remain structurally intact. Measurements of the distribution of U in the Culebra will be more meaningful if the inert and exchangeable components of the U content of the clays can be quantified.

Oxygen Regime of the Water Bodies as Main Factor of Different Metals Forms Migration within the System “Bottom Sediments - Water”

2009 ◽  
Vol 45 (2) ◽  
pp. 85-105 ◽  
Author(s):  
P. N. Linnik ◽  
O. V. Timchenko ◽  
A. V. Zubko ◽  
I. B. Zubenko ◽  
L. A. Malinovskaya
Keyword(s):  
Bottom Sediments ◽  
Water Bodies ◽  
Oxygen Regime ◽  
Main Factor

Investigations on the filtration of natural aquatic suspensions supported by dosing small amounts of Fe(III)-salts (βFe ≤ 0.1 mg.L-1): mode of action and basic design criteria

2002 ◽  
Vol 2 (2) ◽  
pp. 91-98
Author(s):  
R. Winzenbacher ◽  
R. Schick ◽  
H.-H. Stabel ◽  
M. Jekel
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Iron Hydroxides ◽  
Essential Step ◽  
Iron Salts ◽  
Alkaline Earths ◽  
Co Precipitation ◽  
Solid Liquid ◽  
Solid Liquid Separation

Improved removal of particles during the treatment of natural aquatic suspensions has been achieved by pre-ozonation and the addition of small quantities of iron salts (βFe ≤ 0.1 mg.L-1; “Fe(III)-assisted filtration”) followed by rapid filtration. As shown by investigations on a large-scale installation at Lake Constance Water Supply, this procedure reliably reduces suspended solids by at least 2-3 powers of ten in long-term use. However, the high efficacy of Fe(III)-assisted filtration cannot be explained on the basis of known coagulation mechanisms (like adsorption-charge neutralization, co-precipitation). Instead, the essential step was found to be the conditioning of the filter medium by coating it with colloids containing Fe(OH)3, and this “Fe coating” process occurs only in the presence of alkaline earths (especially Ca2+). According to further experiments, the enhanced solid-liquid separation was ultimately traced to chemical interactions such as the formation of calcium-organic association structures between the iron hydroxides and other solids. For design of Fe(III)-assisted filtration steps, finally, a βCa/DOC ratio above 40 mg.mg-1 and pre-oxidation with ozone dosages not exceeding 2 mg O3/mg DOC was recommended.

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