講演情報
[AOS25-P14]Tracing Anthropogenic Lead Sources and Copper Cycling in the Western North Pacific: Insights from stable isotope ratios
*Bo-Heng Kao1,2、Yu-Hsuan Liang1、Kuo-Fang Huang1 (1.Institute of Earth Sciences, Academia Sinica、2.Department of Geosciences, National Taiwan University, Taiwan)
キーワード：
Anthropogenic Lead、Copper Cycling、Isotope Ratios、the Western North Pacific
Since the Industrial Revolution, anthropogenic emissions have increased dissolved Lead (Pb) concentrations in surface seawater from approximately 10 pmol/kg to 200 pmol/kg. While North Atlantic Pb levels have declined to ~20 pmol/kg following the phase-out on leaded gasoline in the United States, concentrations in the North Pacific and Indian Oceans remain elevated. Unlike Pb, copper (Cu) is an essential micronutrient, though it becomes toxic when free Cu2+ concentrations are high. Consequently, characterizing the depth profiles of Pb and Cu isotopes provides critical constraints on the sources and cycling of these elements in the ocean.
Here we investigate the concentrations and isotopic compositions of dissolved Pb and Cu in the Northern South China Sea (NSCS), Kuroshio Current, and West Philippine Sea. Seawater samples were collected using a trace-metal clean sampling system during cruise NOR1-0068. Trace metals were preconcentrated and purified using NOBIAS PA1 chelating resin and AG MP-1 anion exchange resin. Elemental concentrations were determined by HR-ICP-MS, and isotopic ratios were measured via MC-ICP-MS. Distinct subsurface Pb maxima were observed in the NSCS at 100 m (29.7 pmol/kg) and 300 m (40.4 pmol/kg). Corresponding isotopic signatures (206Pb/207Pb = 1.1609 and 1.611; 208Pb/207Pb = 2.4458 and 2.4475; 206Pb/204Pb = 18.1286 and 18.1302) indicate a dominant anthropogenic origin. Notably, surface Pb concentrations in the Bashi Channel were approximately 20 pmol/kg higher than at neighboring stations, with isotopic ratios (206Pb/207Pb range from 1.1437 to 1.1463; 208Pb/207Pb from 2.4241 to 2.4270; 206Pb/204Pb from 17.8271 to 17.8715) closely resembling anthropogenic signatures from China and Southeast Asia. These results suggest that Pb is transported and redistributed across the region via both atmospheric deposition and oceanic circulation. Dissolved Cu (0.19-3.14 nmol/kg) exhibited nutrient-type behavior, with UV-irradiated samples yielding concentrations 2–3 times higher than non-UV treated samples. These results indicate significant organic complexation of Cu, and further isotope analysis will better constrain marine Cu cycling in the western North Pacific.
Here we investigate the concentrations and isotopic compositions of dissolved Pb and Cu in the Northern South China Sea (NSCS), Kuroshio Current, and West Philippine Sea. Seawater samples were collected using a trace-metal clean sampling system during cruise NOR1-0068. Trace metals were preconcentrated and purified using NOBIAS PA1 chelating resin and AG MP-1 anion exchange resin. Elemental concentrations were determined by HR-ICP-MS, and isotopic ratios were measured via MC-ICP-MS. Distinct subsurface Pb maxima were observed in the NSCS at 100 m (29.7 pmol/kg) and 300 m (40.4 pmol/kg). Corresponding isotopic signatures (206Pb/207Pb = 1.1609 and 1.611; 208Pb/207Pb = 2.4458 and 2.4475; 206Pb/204Pb = 18.1286 and 18.1302) indicate a dominant anthropogenic origin. Notably, surface Pb concentrations in the Bashi Channel were approximately 20 pmol/kg higher than at neighboring stations, with isotopic ratios (206Pb/207Pb range from 1.1437 to 1.1463; 208Pb/207Pb from 2.4241 to 2.4270; 206Pb/204Pb from 17.8271 to 17.8715) closely resembling anthropogenic signatures from China and Southeast Asia. These results suggest that Pb is transported and redistributed across the region via both atmospheric deposition and oceanic circulation. Dissolved Cu (0.19-3.14 nmol/kg) exhibited nutrient-type behavior, with UV-irradiated samples yielding concentrations 2–3 times higher than non-UV treated samples. These results indicate significant organic complexation of Cu, and further isotope analysis will better constrain marine Cu cycling in the western North Pacific.