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Platinum group elements (Pt and Ir) deposition at Dome C (East Antarctica) between 572 kyr BP to 800 kyr BP

2022-03-24T07:13:07Z

Title: Platinum group elements (Pt and Ir) deposition at Dome C (East Antarctica) between 572 kyr BP to 800 kyr BP Authors: C. Barbante; Hwang, Heejin; Hong, Sungmin; C.F. Boutron; P.Gabrielli; Hur, Soon Do; Tseren-Ochir, Soyol-Erdene Abstract: Platinum group elements (PGE: Ir and Pt) concentrations were determined in 42 sections from the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core, covering a period from ~572 kyr BP to ~800 kyr BP, by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) coupled with desolvation nebulizion system and sub-boiling pre-concentration. Our data enable us to extend the previous EPICA Dome C (EDC) records of Ir and Pt covering the past 270 kyr, which corresponds to the last two climatic cycles. Here we discuss the Ir and Pt concentration records coupling with crustal reference element (Ba) and some refractory trace metals (Yb and Hf). Crustal enriched elements (Ba, Yb and Hf) show well defined variations in concentrations in relation to climatic conditions with lower values during the interglacial periods and much increased values by ~10 during the glacial periods. On the other hand, the siderophile elements (Ir and Pt) show a less differences between their concentrations for different climatic conditions. Mean concentrations of Ir and Pt for the glacial periods were approximately two times higher than their mean concentrations for the interglacial periods. Concentration ratios (Ir/Pt) and crustal enrichment factors (EFc) of Ir and Pt indicate that atmospheric PGE in Antarctica originated dominantly from non-crustal source (i.e., extraterrestrial), and the extenpled plasma sector field mass spectrometry (ICP-SFMS) coupled with desolvation nebulizion system and sub-boiling pre-concentration. Our data enable us to extend the previous EPICA Dome C (EDC) records of Ir and Pt covering the past 270 kyr, which corresponds to the last two climatic cycles. Here we discuss the Ir and Pt concentration records coupling with crustal reference element (Ba) and some refractory trace metals (Yb and Hf). Crustal enriched elements (Ba, Yb and Hf) show well defined variations in concentrations in relation to climatic

RARE EARTH ELEMENT CYCLING IN THE PORE WATERS OF THE BERING SEA SLOPE (IODP EXP. 323)

2022-03-24T07:13:30Z

Title: RARE EARTH ELEMENT CYCLING IN THE PORE WATERS OF THE BERING SEA SLOPE (IODP EXP. 323) Authors: Huh, Youngsook; Tseren-Ochir, Soyol-Erdene Abstract: We studied the diagenetic behavior of rare earth elements in a highly productive passive margin setting of the Bering Sea Slope. Pore water concentrations of fourteen REEs were determined to a depth of ~140 meters below seafloor (mbsf). Site U1345 was drilled during the Integrated Ocean Drilling program (IODP) Expedition 323 at a water depth of 1008 m presently in the center of an oxygen minimum zone. The concentrations of REEs were enriched in the pore water relative to deep seawater indicating that there is significant liberation from sediment during diagenesis. There was a peak at ~ 10 mbsf, which was more pronounced for the HREE, whose depth coincided with those of dissolved iron and manganese and below the sulfate-methane transition zone (~6.3 mbsf). In the upper 1 mbsf, there is a minor peak in HREE. Below ~40 mbsf, the concentration profiles were relatively constant. The positive Ce anomaly was relatively constant (average shale-normalized Ce/Ce*=1.1±0.2) throughout the depth profile indicating that Ce depletion in seawater is completely regenerated and maintained. HREE-enrichment is observed for the entire 140 mbsf except for the upper ~1 mbsf where there is MREE-bulge. REE release in the shallow depths (upper ~1 m) is attributed to preferential release of LREEs and MREEs during organoclastic reduction of Fe, Mn hydroxides in anoxic sediments. The high HREE concentrations observed Site U1345 was drilled during the Integrated Ocean Drilling program (IODP) Expedition 323 at a water depth of 1008 m presently in the center of an oxygen minimum zone. The concentrations of REEs were enriched in the pore water relative to deep seawater indicating that there is significant liberation from sediment during diagenesis. There was a peak at ~ 10 mbsf, which was more pronounced for the HREE, whose depth coincided with those of dissolved iron and manganese and below the sulfate-methane transition zone (~6.3 mbsf). In the upper 1 mbs

Deposition at Dome Fuji, Antarctica since the 1950s

2022-03-24T07:13:45Z

Title: Deposition at Dome Fuji, Antarctica since the 1950s Authors: Tseren-Ochir, Soyol-Erdene; Huh, Youngsook; Kotaro Fukui; Hideaki Motoyama; Hur, Soon Do; Hong, Sungmin Abstract: Worldwide production of PGEs has been rising steadily over the past few decades because of the increased use of these metals, such as in catalysts, jewelry, and electronics. Here, we present the first time series for PGE (Pt, Ir, and Rh) deposition in Antarctica and determined the changes in the global background atmospheric level over a recent 50-year period based on determinations of Pt, Ir, and Rh in snow samples collected from Queen Maud Land, East Antarctica. The 50-year average PGE concentrations in Antarctic snow were 17 fg g–1 (4.7–76 fg g–1) for Pt, 0.12 fg g–1 (<0.05–0.34 fg g–1) for Ir, and 0.71 fg g–1 (0.12–8.8 fg g–1) for Rh. The concentration peaks for Pt, Ir, and Rh were observed at depths corresponding to volcanic eruption periods, indicating that PGEs can be used as a good tracer of volcanic activity in the past. A significant increase in concentrations and crustal enrichment factors for Pt and a slight enhancement in enrichment factors for Rh were observed after the 1980s. This suggests that there has been large-scale atmospheric pollution for Pt and probably for Rh since the 1980s, which may be attributed to the increasing emissions of these metals from anthropogenic sources such as automobile catalysts and metal production processes.) deposition in Antarctica and determined the changes in the global background atmospheric level over a recent 50-year period based on determinations of Pt, Ir, and Rh in snow samples collected from Queen Maud Land, East Antarctica. The 50-year average PGE concentrations in Antarctic snow were 17 fg g–1 (4.7–76 fg g–1) for Pt, 0.12 fg g–1 (<0.05–0.34 fg g–1) for Ir, and 0.71 fg g–1 (0.12–8.8 fg g–1) for Rh. The concentration peaks for Pt, Ir, and Rh were observed at depths corresponding to volcanic eruption periods, indicating that PGEs can be used as a good tracer of volcan

Dissolved platinum in major rivers of East Asia

2022-03-24T07:11:38Z

Title: Dissolved platinum in major rivers of East Asia Authors: Huh, Youngsook; Tseren-Ochir, Soyol-Erdene Abstract: Dissolved platinum concentrations of eleven large pristine river systems in East Asia (~200 samples) were determined to better constrain the oceanic platinum budget. Most samples had concentrations less than 1.4 pM, and relatively high concentrations up to 5.8 pM were measured in only approximately 6% of the samples. Principal component analysis was carried out using Pt, major elements (Na, K, Mg, Ca, HCO3-, Cl-, SO42-, Si), Sr, and 87Sr/86Sr of the dissolved load to derive the potential sources of Pt. The Pt in the main (<1.4 pM) group was best clustered with Mg, HCO3-, Ca, Sr, and SO42-, interpreted as weathering of carbonates and associated gypsum. The Pt in the outlier group was best clustered with Si, K, 87Sr/86Sr, Ca, and HCO3-, interpreted as weathering of silicates. The median Pt concentrations of the individual river systems had only a small range, from 0.18 pM (Duman) to 0.63 (Huang He), and the difference in Pt yield mainly resulted from the difference in runoff. The rivers draining the eastern Tibetan Plateau – the Salween, Mekong, Chang Jiang (Yangtze), Hong (Red), and Huang He (Yellow) – had relatively higher Pt yield than the rivers of the Russian Far East – the Amur, Lena, Yana, Indigirka, and Kolyma. The discharge-weighted mean Pt concentration was 0.36 pM for the eleven river systems of East Asia. If this value is extrapolated globally, the estimated rivconcentrations up to 5.8 pM were measured in only approximately 6% of the samples. Principal component analysis was carried out using Pt, major elements (Na, K, Mg, Ca, HCO3-, Cl-, SO42-, Si), Sr, and 87Sr/86Sr of the dissolved load to derive the potential sources of Pt. The Pt in the main (<1.4 pM) group was best clustered with Mg, HCO3-, Ca, Sr, and SO42-, interpreted as weathering of carbonates and associated gypsum. The Pt in the outlier group was best clustered with Si, K, 87Sr/86Sr, Ca, and HCO3-, interpreted as weathering of silicates.