scholarly journals Radiation-ecological evaluation of rock dumps in the south zone of the Elkon uranium mine region (the Southern Yakutia)

2019 ◽  
pp. 65-78
Author(s):  
A. P. Chevychelov ◽  
P. I. Sobakin ◽  
A. N. Gorokhov
Keyword(s):  
Radioactive Contamination ◽  
Surface Waters ◽  
Vegetation Cover ◽  
Specific Activity ◽  
Radiation Hazard ◽  
Uranium Mine ◽  
The South ◽  
Humid Climate ◽  
Southern Yakutia ◽  
South Zone

This study aims at investigating the allocation conditions of rock dumps in the South zone located in the Elkon uranium mine region (the Southern Yakutia), and also at determining their radiation parameters as sources of technogenic contamination of the soil-vegetation cover and surface waters, and assessing the danger of these dumps for people. In this study, the generally accepted geographical methods were used, including comparative geographical and geochemical methods, as well as a combination of various radiometric research methods. The radiation parameters of the rock dumps of the South zone of the Elkon uranium mine region, the content and distribution of uranium, radium and radon in surface waters, as well as 238U content in technogenic soils at different distances from radioactive contamination sources were studied. It was found that the most active dumps, in terms of their radiation parameters, are located close to the radioactive ores, with the EDR of 1600-2150 R/h, effective specific activity - 20441-23640 Bq/kg, and uranium content of 1637-1888 mg/kg. The ranking of the studied dumps according to the degree of radiation hazard showed that 12 out of 31 dumps (39%) belong to the safe category, 6 (19%) belong to the category of potentially dangerous, and 5 and 8 (16% and 26%) were classified as dangerous and very dangerous respectively. In the conditions of the mountainous terrain, cold and humid climate of the studied area, these rock dumps, which are unevenly spread in mountain and taiga landscapes over the area of about 500 km2, are the main source of radioactive contamination of soil and vegetation cover and surface waters. The maximum contents of uranium, radium and radon in the studied surface waters were 18010-7 g/L, 4.710-12 g/L and 256.8 Bq/L respectively, which are 100, 8 and 198 times higher than their background concentrations in waters of natural landscapes. In the studied technogenic zones, a direct relationship was registered between the pollution intensity in surface water and that in the drained alluvial soils formed in the floodplains of these watercourses.

scholarly journals Isotopic fractionation of carbon during uptake by phytoplankton across the South Atlantic subtropical convergence

2019 ◽  
Vol 16 (18) ◽  
pp. 3621-3635 ◽  
Author(s):  
Robyn E. Tuerena ◽  
Raja S. Ganeshram ◽  
Matthew P. Humphreys ◽  
Thomas J. Browning ◽  
Heather Bouman ◽  
...  
Keyword(s):  
Food Web ◽  
Cell Size ◽  
Surface Waters ◽  
Isotopic Fractionation ◽  
Water Masses ◽  
Global Ocean ◽  
Carbon Uptake ◽  
The South ◽  
Marine Food Web ◽  
Marine Food

Abstract. The stable isotopic composition of particulate organic carbon (δ13CPOC) in the surface waters of the global ocean can vary with the aqueous CO2 concentration ([CO2(aq)]) and affects the trophic transfer of carbon isotopes in the marine food web. Other factors such as cell size, growth rate and carbon concentrating mechanisms decouple this observed correlation. Here, the variability in δ13CPOC is investigated in surface waters across the south subtropical convergence (SSTC) in the Atlantic Ocean, to determine carbon isotope fractionation (εp) by phytoplankton and the contrasting mechanisms of carbon uptake in the subantarctic and subtropical water masses. Our results indicate that cell size is the primary determinant of δ13CPOC across the Atlantic SSTC in summer. Combining cell size estimates with CO2 concentrations, we can accurately estimate εp within the varying surface water masses in this region. We further utilize these results to investigate future changes in εp with increased anthropogenic carbon availability. Our results suggest that smaller cells, which are prevalent in the subtropical ocean, will respond less to increased [CO2(aq)] than the larger cells found south of the SSTC and in the wider Southern Ocean. In the subantarctic water masses, isotopic fractionation during carbon uptake will likely increase, both with increasing CO2 availability to the cell, but also if increased stratification leads to decreases in average community cell size. Coupled with decreasing δ13C of [CO2(aq)] due to anthropogenic CO2 emissions, this change in isotopic fractionation and lowering of δ13CPOC may propagate through the marine food web, with implications for the use of δ13CPOC as a tracer of dietary sources in the marine environment.

Specific Activity and Radioactive Contour Maps of Natural (40K, 226Ra and 232Th) and Anthropogenic (137Cs) Radionuclides in Surface Soil Samples from Phang Nga Province, Thailand

2014 ◽  
Vol 979 ◽  
pp. 35-38
Author(s):  
Prasong Kessaratikoon ◽  
Ruthairat Boonkrongcheep ◽  
Supphawut Benjakul ◽  
Suchin Udomsomporn
Keyword(s):  
Dose Rate ◽  
Surface Soil ◽  
Specific Activity ◽  
Hazard Index ◽  
Research Data ◽  
Soil Samples ◽  
Gamma Ray Spectrometry ◽  
The South ◽  
Absorbed Dose Rate ◽  
Contour Maps

The specific activity of the natural (40K, 226Ra and 232Th) and anthropogenic (137Cs) radionuclides have been studied and evaluated for 97 surface soil samples collected from 7 districts of Phang Nga province in the south of Thailand. High-purity germanium (HPGe) detector and gamma ray spectrometry analysis system were employed to measure and analyze the experimental results. It was found that, the ranges of specific activities of 40K, 226Ra, 232Th and 137Cs in surface soil samples are 251.50 – 15740.34, 15.21 – 791.42, 18.14 – 854.34 and < 0.33 – 16.91 Bq/kg with average values are 2886.77 ± 225.93, 165.71 ± 8.45, 160.36 ± 7.93 and 5.76 ± 2.49 Bq/kg, respectively. The results were also compared with some research data in national and global radioactivity measurement and evaluations. Furthermore, the radiological hazards of Phang Nga province were calculated through the radium equivalent activity (Raeq), the external hazard index (Hex), the gamma absorbed dose rate (D) and the annual effective dose rate (AEDout) and also compared with research data in the south of Thailand and the safety limits recommended values by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Moreover, the radioactive contour maps of the natural (40K, 226Ra and 232Th) and anthropogenic (137Cs) radionuclides have been also created for the investigated area.

scholarly journals Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific

2008 ◽  
Vol 5 (4) ◽  
pp. 1165-1173 ◽  
Author(s):  
R. Sempéré ◽  
M. Tedetti ◽  
C. Panagiotopoulos ◽  
B. Charrière ◽  
F. Van Wambeke
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Detectable Effect ◽  
Neutral Sugar ◽  
The South ◽  
East Pacific ◽  
Significant Stimulation ◽  
Order Of Magnitude ◽  
Neutral Sugars

Abstract. The distribution and bacterial availability of dissolved neutral sugars were studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Four contrasting stations were investigated: Marquesas Islands (MAR), the hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre (EGY), and the coastal waters associated to the upwelling area off Chile (UPW). Total (free and combined) dissolved neutral sugar (TDNS) concentrations were in the same order of magnitude at MAR (387±293 nM), GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY (250 m, 58 nM), respectively. Their contribution to dissolved organic carbon (TDNS-C×DOC−1%) was generally low for all sites varying from 0.4% to 6.7% indicating that South East Pacific surface waters were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS; e.g. sugars analyzed without hydrolysis) concentrations were very low within the detection limit of our method (5–10 nM) accounting for <5% of the TDNS. In general, the predominant sugars within the TDNS pool were glucose, xylose, arabinose, and galactose, while in the FDNS pool only glucose was present. TDNS stock to bacterial production ratios (integrated values from the surface to the deep chlorophyll maximum) were high at GYR with respect to the low primary production, whereas the opposite trend was observed in the highly productive area of UPW. Intermediate situations were observed for MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to natural solar radiation was also experimentally studied and compared to dark treatments. Our results showed no or little detectable effect of sunlight on DOM bacterial assimilation in surface waters of UPW and GYR, while a significant stimulation was found in MAR and EGY. The overall results clearly suggest that DOM is less labile at GYR compared to UPW, which is consistent with the observed accumulation of dissolved organic carbon and the elevated C/N ratios reported by Raimbault et al. (2008).

The Effect of a Storm on an Inshore Area with Markedly Stratified Waters

1935 ◽  
Vol 1 (4) ◽  
pp. 227-237 ◽  
Author(s):  
H. B. Hachey
Keyword(s):  
Nova Scotia ◽  
North Atlantic ◽  
Surface Waters ◽  
South Coast ◽  
The South ◽  
Wind Action ◽  
Bottom Waters ◽  
Mixed Water

Coincident with the formation and subsequent movement of a North Atlantic cyclone following the characteristic track, offshore surface waters are forced to the south coast of Nova Scotia with consequent removal of intermediate and bottom waters. Wind action, as the storm approaches, intensifies the mixing of the waters. Markedly stratified waters are thus temporarily replaced by a body of thoroughly mixed water.

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