石英中炭素14の超高感度測定法の開発と氷河地形編年への応用

石英中に存在する宇宙線生成核種炭素14を検出するための高感度で迅速な加速器質量分析法を確立し、モレーン岩石に炭素14表面照射年代法を適応させて氷河地形編年を行うことが目的である。6MVタンデム加速器とガスイオン源を用いて、二酸化炭素から炭素14を迅速に測定する手法開発を進めた。ガスイオン源は固体イオン源と比べてバックグラウンドと測定誤差が高いが、少なくとも0.5-1.0ミリグラムの二酸化炭素について炭素14の迅速測定が可能である。他の宇宙線生成核種（ベリリウム10・アルミニウム26・塩素36・カルシウム41）の超高感度測定も可能となった。The first test of the 14C-accelerator mass spectrometry (AMS) system was successfully performed using a gas/solid hybrid ion source and an automated sample preparation system with an elemental analyzer (EA). The maximum 12C current of 11 µA was achieved using the optimized CO2 flow rate to the hybrid ion source. The machine background of 14C/12C for the AMS system reached to 2.4 × 10^-16 (0.02 percent modern carbon, pMC) using unprocessed mineral graphite. The blank level of 14C/12C including the combustion process for an IAEA-C1 graphite sample was 4.6 × 10^-16 (0.05 pMC), demonstrating the low blank level of the automatic sample preparation system. In contrast, the blank level of 14C/12C including the combustion process for an IAEA-C1 CO2 sample was 5.0 × 10^-15 (0.49 pMC), an order of magnitude worse than that for the graphite sample. The measurement uncertainty for the gas ion source was 0.6%, 2 times worse than that for the solid ion source (0.3%).研究課題/領域番号:16K16347, 研究期間(年度):2016-04-01 - 2019-03-3

Geochemical Control of PAHs by Inflowing River Water to West Nanao Bay, Japan, and Its Influences on Ecological Risk: Small-Scale Changes Observed under Near-Background Conditions at an Enclosed Bay

Polycyclic aromatic hydrocarbons (PAHs), even at low concentrations, have been shown to trigger changes in life cycles and provoke abnormal behaviors in numerous marine organisms. From May 2019 to September 2020, particulate and dissolved PAH concentrations were analyzed on the surface water of West Nanao Bay, Japan, to determinate their levels, emission sources, environmental pathways, and ecological risks at this remote but semi-enclosed bay. The 14 targeted PAHs were analyzed by HPLC-fluorescence detector. Mean total PAH concentrations were lower than 20.0 ng L−1 for most samples. Based on fluoranthene (Flu) to pyrene (Pyr) ([Flu]/[Flu + Pyr]) and benzo[a]anthracene (BaA) to chrysene (Chr) ([BaA]/[BaA + Chr]) isomeric ratios and a varimax rotated PCA, it was established that biomass combustion was the principal source in the particulate phase and that liquid fossil fuel combustion was the principal source in the dissolved phase. From salinity and turbidity distribution, riverine discharges were determined to be the major and continuous transportation pathway of particulate PAHs. It was observed that rain events had a role in the transport of dissolved PAHs. The risk quotients (RQ∑14 PAHs (NCs): 0–84.53) indicated that PAHs represented a very low to low acute environmental risk. The results of this study will contribute to filling the paradigm gap of ecotoxicological studies in remote areas, working as a booster for future in-lab studies of non-lethal implications of endocrine disruptors such as PAHs

A New 14

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.A new continuous sediment core (PY608W-PC; 3.8 m length) for reconstruction of climatic and environmental changes in the southeastern Tibetan Plateau was taken from the eastern part of Lake Pumoyum Co in August 2006. Sediment layers of the lower part of PY608W-PC (380-300 cm depth) were composed mainly of relatively large plant residues (up to ~3 cm in length) with an admixture of fine sand and sandy silt. The large plant residues disappeared at ~300-290 cm depth in core PY608W-PC and were replaced by silt-silty clay. The large plant residues from the lower part of PY608W-PC could be aquatic, because the plant residues were extremely enriched in 13C (up to -3.0‰, -5.6 +/- 2.3‰ on average). On the other hand, the plant residue concentrates (PRC fractions) from the upper part of the core (290-0 cm in depth) could be terrestrial C3 plants (delta-13C = -21.8 +/- 1.7 on average). Radiocarbon dating was performed on the large plant residues and PRC fractions from the PY608W-PC sediment core, which represented the chronology from ~19,000 cal BP to present.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

A New 14C Data Set of the PY608W-PC Sediment Core from Lake Pumoyum Co (Southeastern Tibetan Plateau) over the Last 19 kyr

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.A new continuous sediment core (PY608W-PC; 3.8 m length) for reconstruction of climatic and environmental changes in the southeastern Tibetan Plateau was taken from the eastern part of Lake Pumoyum Co in August 2006. Sediment layers of the lower part of PY608W-PC (380-300 cm depth) were composed mainly of relatively large plant residues (up to ~3 cm in length) with an admixture of fine sand and sandy silt. The large plant residues disappeared at ~300-290 cm depth in core PY608W-PC and were replaced by silt-silty clay. The large plant residues from the lower part of PY608W-PC could be aquatic, because the plant residues were extremely enriched in 13C (up to -3.0‰, -5.6 +/- 2.3‰ on average). On the other hand, the plant residue concentrates (PRC fractions) from the upper part of the core (290-0 cm in depth) could be terrestrial C3 plants (delta-13C = -21.8 +/- 1.7 on average). Radiocarbon dating was performed on the large plant residues and PRC fractions from the PY608W-PC sediment core, which represented the chronology from ~19,000 cal BP to present.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

14C Dating of Holocene Soils from an Island in Lake Pumoyum Co (Southeastern Tibetan Plateau)

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.Soil samples from an 85-cm-long continuous section (PY608ES) were collected from an island in Lake Pumoyum Co (southeastern Tibetan Plateau, ~5020 m asl) in August 2006. To estimate past environmental conditions of Lake Pumoyum Co during the Holocene, we analyzed radiocarbon ages, stable carbon isotope compositions, and total organic carbon/total nitrogen (TOC/TN) atomic ratios of the soil samples. The 14C measurements were performed with the Tandetron accelerator mass spectrometry system at the Center for Chronological Research, Nagoya University. The 14C concentration in the surface layer (101 pMC; 5-10 cm soil depth) was nearly modern. A 14C chronology of the sequence indicated that continuous soil development began on the island in Lake Pumoyum Co at ~5800 cal BP (at 63 cm soil depth, the top of a gravel layer). These results may reflect a decrease in the lake level in the middle Holocene. The age of the obvious lithologic boundary (~5800 cal BP) corresponds to the end of Holocene climate optimum.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Interannual variation of polycyclic aromatic hydrocarbons in surface seawater at adjacent seas of the Japanese archipelago

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr19-03c/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr20-01/