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

虽然海洋中发现的大部分化学元素铅（Pb）来自人类排放到大气中，但在南大洋等偏远地区，铅的自然来源可能很重要。铅的自然来源来自地壳，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，有三种稳定的同位素，来自铀和钍的衰变。因此，不同时代烃源岩沉积物中铅同位素比值存在明显差异。这些同位素比值可以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。铅的同位素测量提供了关于大气气溶胶对污染物的全球输送以及海洋环流和颗粒输送对污染物和其他元素的分布的时间变化的信息。在这个项目中，将从南大洋的南太平洋部分收集水样，以帮助确定该海洋区域人为铅的来源，将其与来自南极大陆的天然铅区分开来，并了解海洋环流对铅的扩散。该项目将资助一名研究生和一名博士后初期工作人员，拟议的工作将作为GEOTRACES在南太平洋和南大洋太平洋部分进行的微量元素和同位素取样考察的一部分进行。在这些考察期间对铅同位素的测量将提供追踪海洋中其他颗粒反应金属的来源、命运和运输的能力。将对水柱、沉积物芯顶部和气溶胶样品进行全套铅同位素分析（204，206，207，208），以提供对水体中人为铅污染程度的深入了解，南美大陆不同铅同位素的相对贡献，太平洋-南极海岭热液Pb输入的意义以及沉积物Pb同位素是否反映了大气环流模式的变化。 这项工作将允许各种人为和自然的过程，确定全球分布和过程的铅的评价。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.