Studies of 26Al and 10Be as Potential Constraints on Paleoproductivity and Extraterrestrial Influx

26Al 和 10Be 对古生产力和外星人流入的潜在限制的研究

• 批准号: 0117895
• 负责人: Teh-Lung Ku
• 金额: $ 45万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-10-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0117895&HistoricalAwards=false
• 关键词: Studies; 26Al; 10Be; Potential; Constraints

ABSTRACTOCE-0117895The source functions and geochemical pathways of 26Al (half-life 0.72 My) and 10Be (1.5 My) in the sea are closely linked. These radioisotopes, produced mainly by the interaction of cosmic rays with the atmospheric constituents, enter the ocean via wet and dry fallout with a nearly constant ratio and deposit to the seafloor through particle scavenging. The scavenging time of 10Be is comparable to the ocean mixing time of ~103 years,but that of 26Al is about 30 times shorter. As a consequence, 10Be is more readily transported to areas of high particle flux or high productivity such as ocean margins, where the deposition ratio of 10Be/26Al becomes much higher than their production ratio. These features -relatively stable source function, constant production ratio,and high particle reactivity with differential removal -render the two nuclides as a pair suitable for tracing geochemical and geophysical processes.In this project, researchers at the University of Southern California will evaluate the utility of the 10Be/26Al ratio in sediments as a proxy for paleo-particle flux or paleoproductivity, and the use of the 3He/26Al ratio in sediment cores to probe the factors affecting the flux of earth-bound interplanetary dust particles (IDP) and its variation with time. Measurements of 10Be and 26Al will be carried out on samples of seawater, sediment-trap material, and sediment, and of 3He in sediment cores. Measurements of U-Th isotopes, 27Al, 9Be, opal, carbonates and other chemical components will also be made on sediment trap and sediment samples. Data so obtained will be used to study the spatial and temporal variations in the distribution and flux of 10Be and 26Al and the mechanisms causing the variations. The influence of particle composition and remineralization on the sedimentary 10Be/26Al signals will be investigated to constrain better the 10Be/26Al proxy which will be applied to sediment cores from the equatorial Pacific and the Antarctic to provide an understanding of the productivity changes in areas characterized by high-nutrients and low-chlorophyll of the surface water. Past variations in IDP will be examined by the coupled measurements of 3He/26Al and 3He/230Th in sediment cores.

26 Al（半衰期0.72 My）和10 Be（1.5 My）在海洋中的源函数和地球化学途径密切相关。 这些放射性同位素主要由宇宙射线与大气成分相互作用产生，以几乎恒定的比例通过干湿沉降物进入海洋，并通过粒子清除存款到海底。 10 Be的清除时间与~103年的海洋混合时间相当，但26 Al的清除时间短约30倍。 因此，10 Be更容易被输送到高粒子通量或高生产率的地区，如海洋边缘，在那里10 Be/26 Al的沉积比变得比它们的生产比高得多。 这些特征-相对稳定的源函数、恒定的生产率和具有差异去除的高粒子反应性-使这两种核素适合作为一对来追踪地球化学和地球物理过程。在这个项目中，南加州大学的研究人员将评估沉积物中10 Be/26 Al比率作为古粒子通量或古生产力的替代的效用，利用沉积物柱芯中的~ 3 He/~（26）Al比值探讨了行星际尘埃颗粒（IDP）通量的影响因素及其随时间的变化。 将对海水、沉积物收集器材料和沉积物样品进行10 Be和26 Al的测量，并对沉积物芯中的3 He进行测量。 还将对沉积物捕获器和沉积物样品进行U-Th同位素、27 Al、9 Be、蛋白石、碳酸盐和其他化学成分的测量。 由此获得的数据将用于研究10 Be和26 Al的分布和通量的时空变化以及引起变化的机制。 将研究颗粒组成和矿化对沉积物10 Be/26 Al信号的影响，以更好地约束10 Be/26 Al代用品，该代用品将应用于赤道太平洋和南极的沉积物岩心，以了解以表层水的高营养物和低叶绿素为特征的地区的生产力变化。 通过对沉积物芯样中3 He/26 Al和3 He/230 Th的耦合测量，将对IDP的过去变化进行检查。