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Rizzi M, Hovikoski J, Schovsbo NH, Therkelsen J, Olivarius M, Nytoft HP, Nga LH, Thuy NTT, Toan DM, Bojesen-Koefoed J, Petersen HI, Nielsen LH, Abatzis I, Korte C, Fyhn MBW. Factors controlling accumulation of organic carbon in a rift-lake, Oligocene Vietnam. Sci Rep 2020; 10:14976. [PMID: 32917944 PMCID: PMC7486892 DOI: 10.1038/s41598-020-71829-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 07/30/2020] [Indexed: 11/30/2022] Open
Abstract
Understanding of the processes of petroleum source rock (SR) accumulation in lacustrine rift basins and the behavior of lake systems as long-term carbon sinks is fragmentary. Investigation of an 800 m thick (500 m core and ~ 300 m outcrop), deep-lacustrine, Oligocene section in Vietnam, provides a rare insight into the controls and deposition of organic carbon (OC) and SR formation in continental rift basins. A multidisciplinary dataset, combining elemental data, inorganic and organic geochemistry with sedimentology, shows that the richest alginite-prone, sapropelic SR developed during periods of relative tectonic quiescence characterized by moderate primary productivity in a mainly dysoxic lacustrine basin. Increased rift activity and further development of graben morphology intensified water column stratification and anoxia, which hindered nutrient recycling. Sapropelic organic matter (OM) continued to accumulate, but with increasing amorphous OM content and decreasing total OC values. Periods of increased seasonality were characterized by thermocline weakening, enhanced mixing of water columns, increased primary productivity and diatom blooming. The results suggest that a change from dysoxia towards anoxia or extreme primary productivity does not necessarily enhance OC burial and SR quality. External nutrient input from a phosphate-rich hinterland is sufficient for sapropel formation, whereas the main limiting factor is methanogenesis.
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Affiliation(s)
- M Rizzi
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark.
| | - J Hovikoski
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - N H Schovsbo
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - J Therkelsen
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - M Olivarius
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - H P Nytoft
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - L H Nga
- Exploration & Production Centre, Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - N T T Thuy
- Exploration & Production Centre, Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - D M Toan
- Exploration & Production Centre, Vietnam Petroleum Institute, 167 Trung Kinh, Yen Hoa, Cau Giay, Hanoi, Vietnam
| | - J Bojesen-Koefoed
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - H I Petersen
- Total Upstream Danmark A/S, Amerika Plads 29, 2100, Copenhagen, Denmark
| | - L H Nielsen
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - I Abatzis
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - C Korte
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark
| | - M B W Fyhn
- Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350, Copenhagen, Denmark
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Messaris GAT, Abatzis I, Kagadis GC, Samartzis AP, Athanasopoulou P, Christeas N, Katsanos K, Karnabatidis D, Nikiforidis GC. Hysterosalpingography using a flat panel unit: evaluation and optimization of ovarian radiation dose. Med Phys 2012; 39:4404-13. [PMID: 22830773 DOI: 10.1118/1.4729715] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The aim of the present study was the evaluation and optimization of radiation dose to the ovaries (D) in hysterosalpingography (HSG). METHODS The study included a phantom study and a clinical one. In the phantom study, we evaluated imaging results for different geometrical setups and irradiation conditions. In the clinical study, 34 women were assigned into three different fluoroscopy modes and D was estimated with direct cervical TLD measurements. RESULTS In the phantom study, we used a source-to-image-distance (SID) of 110 cm and a field diagonal of 48 cm, and thus decreased air KERMA rate (KR) by 19% and 70%, respectively, for beam filtration: 4 mm Al and 0.9 mm Cu (Low dose). The least radiation exposure was accomplished by using the 3.75 pps fluoroscopy mode in conjunction with beam filtration: Low dose. In the clinical study, D normalized to 50 s of fluoroscopy time with a 3.75 pps fluoroscopy mode reached a value of 0.45 ± 0.04 mGy. Observers' evaluation of diagnostic image quality did not significantly differ for the three different modes of acquisition that were compared. CONCLUSIONS Digital spot radiographs could be omitted in modern flat panel systems during HSG. Fluoroscopy image acquisitions in a modern flat panel unit at 3.75 pps and a beam filtration of 4 mm Al and 0.9 mm Cu demonstrate acceptable image quality with an average D equal to 0.45 mGy. This value is lower compared to the studied literature. For these reasons, the proposed method may be recommended for routine HSG examination in order to limit radiation exposure to the ovaries.
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