Measuring 210Po in Seawater: A Comparison of Methods

测量海水中 210Po：方法比较

• 批准号: 2219285
• 负责人: J Kirk Cochran
• 金额: $ 20.77万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219285&HistoricalAwards=false
• 关键词: Measuring; 210Po; Seawater; Comparison; Methods

The natural radionuclides lead-210 and its granddaughter polonium-210 are present dissolved in seawater and have multiple applications for understanding ocean processes, including determining how fast other similar elements are removed from the oceans and as indicators of the sinking of particulate organic carbon from the photic zone. The latter process is an important control on the level of carbon dioxide in the atmosphere and is thus important to measure. Significantly, the two radionuclides have very different geochemical behaviors- lead is taken up on particle surfaces while polonium can be incorporated into organic matter and recycled with it. From the 1970’s to the present, these radionuclides have been measured on many oceanographic cruises. Two methods have been used to extract them from seawater for measurement. One involves precipitating iron hydroxide from a water sample; the other involves precipitation of a colloidal chelating agent added to the samples. Historical and recent results suggest that both methods give comparable results for lead-210, but the latter method can produce higher concentrations of polonium-210 than the former. This research hypothesizes that polonium-210 in seawater can be associated with dissolved organic matter, especially in the upper water column where organic matter cycling is high, and this can prevent its extraction from a seawater sample by precipitation of iron hydroxide. The aim of this research project is to determine under what circumstances the two methods give comparable results for polonium-210 concentrations in seawater. This research will compare the two methods at a long-established oceanographic site (DYFAMED) in The Mediterranean Sea, where prior results are available for these radionuclides. The work will involve field sampling and a series of laboratory experiments with the iron hydroxide method. This will enable recommendations of best practices for utilization of the methods going forward, even if different methods are used on different oceanographic campaigns such as GEOTRACES and EXPORTS. The project will support one graduate student and outreach events at American Natural History Museum, New York.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.

天然放射性核素铅 210 及其孙子钋 210 溶解在海水中，在了解海洋过程方面具有多种应用，包括确定其他类似元素从海洋中去除的速度以及作为颗粒有机碳从海洋中下沉的指标。后一个过程是对大气中二氧化碳水平的重要控制，因此对测量很重要，这两种放射性核素具有非常不同的地球化学行为——铅被颗粒吸收。从 20 世纪 70 年代至今，人们使用两种方法从海水中提取氢氧化铁进行测量。水样；另一种涉及添加到样品中的胶体螯合剂的沉淀。历史和最近的结果表明，两种方法对铅 210 的结果相当，但后一种方法可以产生更高浓度的铅。这项研究开创了海水中的钋210可以与溶解的有机物相关联，特别是在有机物循环较高的上层水体中，这可以防止其通过沉淀从海水样品中提取出来。该研究项目的目的是确定在什么情况下这两种方法可以得出海水中钋 210 浓度的可比结果。这项研究将在一个长期存在的海洋学地点对这两种方法进行比较。 （DYFAMED）在地中海提供了这些放射性核素的先前结果。这项工作将涉及使用氢氧化铁方法进行现场采样和一系列实验室实验，这将为今后使用这些方法提供最佳实践建议。即使不同的海洋学活动（例如 GEOTRACES 和 EXPORTS）使用不同的方法，该项目也将支持纽约美国自然历史博物馆的一名研究生和外展活动。该奖项反映了 NSF 的法定使命，并通过评估被认为值得支持。使用基金会的智力价值和更广泛的影响审查标准。