Collaborative Research: US GEOTRACES GP17-OCE and GP17-ANT: Pb Isotopes

虽然海洋中发现的大多数化学元素铅（Pb）来自人类向大气排放，但在南大洋等偏远地区，铅的自然来源可能很重要。铅的天然来源来自地壳，并通过冰川侵蚀和气溶胶输入输送到海洋。铅是由放射性衰变产生的，它有三种稳定的同位素，来自铀和钍的衰变。因此，在不同年龄的烃源岩沉积物中可以看到不同的铅同位素比率。这些同位素比值使得区分海洋中的污染物铅是否来自美国、澳大利亚、欧洲和中国成为可能。铅的同位素测量提供了大气气溶胶对全球污染物输送的时间变化以及海洋环流和颗粒输送对污染物和其他元素的分布的信息。本项目将从南大洋的南太平洋部分采集水样，以帮助确定该海洋地区人为铅的来源，将其与南极大陆的天然铅区分开来，并了解铅在海洋环流中的扩散。该项目将支持一名研究生和一名早期职业博士后学者。拟议的工作将作为对南太平洋和南大洋太平洋部分的GEOTRACES微量元素和同位素取样考察的一部分进行。在这些考察中对铅同位素的测量将提供追踪海洋中其他颗粒活性金属的来源、命运和运输的能力。对水柱、沉积物岩心顶部和气溶胶样品进行全套Pb同位素分析（204,206,207,208），以深入了解水柱中人为铅污染的程度、南美大陆不同铅同位素的相对贡献、太平洋-南极脊热液Pb输入的意义以及沉积物Pb同位素是否反映大气环流模式的变化。这项工作将允许评估各种人为和自然过程，这些过程决定了铅的全球分布和过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Although most of the chemical element lead (Pb) found in the ocean is derived from human emissions to the atmosphere, natural sources of Pb may be important in remote locations such as the Southern Ocean. Natural sources of Pb are derived from the Earth’s crust and are delivered to the ocean by glacial erosion and aerosol inputs. Lead is produced by radioactive decay and has three stable isotopes that are derived from the decay of uranium and thorium. Thus, distinct lead isotope ratios are seen in deposits from source rocks of different ages. These isotope ratios make it possible to distinguish whether pollutant lead in the ocean is derived from American, Australian, European, and Chinese sources. Isotope measurements of Pb provide information about temporal changes in the global transport of pollutants by atmospheric aerosols and the distribution of contaminants and other elements by ocean circulation and particulate transport. In this project, water samples will be collected from the South Pacific sector of the Southern Ocean to help establish the origins of anthropogenic lead in this ocean region, distinguish it from natural lead from the Antarctic continent, and understand the dispersal of Pb by ocean circulation. The project will support one graduate student and one early career postdoctoral scholar.The proposed work will be carried out as part of the GEOTRACES trace element and isotope sampling expedition to the South Pacific and Pacific sector of the Southern Ocean. The measurement of Pb isotopes during these expeditions will provide the ability to trace the source, fate, and transport of other particle-reactive metals in the ocean. Water column, sediment core top and aerosol samples will be analyzed for the full suite of Pb isotopes (204, 206, 207, 208) to provide insights into the extent of anthropogenic Pb contamination in the water column, the relative contribution of different lead isotopes from the South American continent, significance of hydrothermal Pb input from Pacific-Antarctic Ridge and whether sediment Pb isotopes reflect variation in the atmospheric circulation pattern. This work will allow evaluation of various anthropogenic and natural processes that determine the global distributions and processes of Pb.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.