Collaborative Research: Quantifying the atmospheric flux of bio-active trace elements to the southwestern Indian Ocean

合作研究：量化西南印度洋生物活性微量元素的大气通量

• 批准号: 2023011
• 负责人: Mark Stephens
• 金额: $ 34.32万
• 依托单位: Florida International University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-11-01 至 2024-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023011&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; atmospheric; flux

Marine phytoplankton (microscopic photosynthetic algae) produce about half of the oxygen we breath and remove billions of tons of carbon dioxide from the atmosphere each year. This primary productivity plays a central role in controlling atmospheric carbon dioxide (pCO2) levels and the global climate. Yet, phytoplankton productivity is limited by lack of iron (an essential trace element) in about 40% of the global ocean. While phytoplankton productivity helps remove carbon dioxide from the atmosphere, it also removes iron and other essential trace elements (like manganese, cobalt, copper, and zinc) from the upper ocean. One critical issue is, “What are the sources for these essential trace elements that are needed to replace those removed by phytoplankton to keep the annual productivity cycles going?” This is especially important in the waters of the Southern Ocean around Antarctica, where ocean circulation brings deep water to the surface; water that is enriched in nutrients like nitrate and phosphate but depleted in essential trace elements. The main source for iron in the open ocean is from desert dust deposition. In this project, scientists will collect aerosols (fine particles in the air) and rain samples over the Southern Ocean to measure how much iron (and the other essential trace elements) is depositing to surface waters. Other scientists will be measuring how fast phytoplankton are growing, and together we will learn how the input of trace elements from dust helps to remove carbon dioxide from the atmosphere. This information can then be used to help predict the future of Earth’s climate. The scientists will communicate results of their study to the public via open house events at their respective campuses, as well as through online forums. One undergraduate student from Florida International University, a leading minority serving university, would be supported and trained as part of this project. The project will measure the aerosol fractional solubility and atmospheric deposition of bio-essential trace elements as part of a multidisciplinary project studying trace element sources, transformations and sinks in the Indian Ocean sector of the Southern Ocean. The research cruise track will cross the currents and oceanographic fronts that are major pathways of the general circulation in the region where we expect to find multiple possible aerosol sources, and where aerosol Fe deposition and rainfall rates are predicted to range over 1-2 orders of magnitude. Aerosol samples (bulk and size-fractionated) will be collected on a daily basis and event-based rain samples to be analyzed for total and soluble major and trace elements including nitrate, phosphate, silicate, chloride, sulfate, Na, Mg, Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Cd. In addition, scientists will analyze the water-soluble organic compounds in aerosols, focusing on compounds such as oxalate and methane-sulfonic acid (MSA) that enhance aerosol trace element solubility. Scientists will use Be-7 concentrations in aerosols and the upper water column to calculate aerosol bulk deposition velocities and test whether the relationship between rainfall rate and bulk deposition velocity that we have previously published can be applied on a more global basis. Further, scientists will use the trace element concentration data along with air-mass back trajectory analysis to apportion the aerosols between anthropogenic and natural sources, and study how aerosol sources affect the fractional solubility. Aerosol and rain subsamples will be provided to collaborators on the cruise for the analysis of additional important parameters.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.

海洋浮游植物（微观光合藻类）每年从大气中从大气中清除数十亿吨二氧化碳。这种主要生产力在控制大气二氧化碳（PCO2）水平和全球气候中起着核心作用。然而，浮游植物生产力受到大约40％全球海洋中缺乏铁（必不可少的痕量元素）的限制。虽然浮游植物的生产力有助于从大气中清除二氧化碳，但它也可以从上海中去除铁和其他必要的微量元素（例如锰，钴，铜和锌）。一个关键的问题是：“这些基本痕量要素的来源是什么来代替浮游植物以保持年度生产力周期进行的那些基本要素？”这在南极洲周围的南大洋的水域尤为重要，海洋循环将深水带到了地面。富含硝酸盐和磷酸盐等营养的水，但在基本的微量元素中耗尽。在开海中铁的主要来源是沙漠尘埃沉积。在该项目中，科学家将收集气溶胶（空气中的细颗粒），并在南大洋上收集雨水样品，以测量铁（以及其他必要的痕量元素）沉积到地表水域的多少。其他科学家将衡量浮游​​植物的增长速度，我们将共同学习粉尘中的微量元素输入如何有助于从大气中清除二氧化碳。然后，这些信息可用于帮助预测地球气候的未来。科学家将通过各自校园以及在线论坛上的开放日活动将其研究结果传达给公众。将支持佛罗里达国际大学的一名本科生，这是一所领先的少数派服务大学。并作为该项目的一部分进行了培训。该项目将衡量生物含量元素的气溶胶分数溶解度和大气沉积，这是一个多学科项目的一部分，该项目研究了南方海洋印度洋部门的微量元素，转化和下沉。研究巡航轨道将越过我们期望找到多种可能的气溶胶来源的该地区一般循环的主要途径，而气雾剂FE沉积和降雨速率预计将超过1-2个数量级。将每天和基于事件的雨水样品收集气雾剂样品（大量和尺寸分级），以分析总和固体和固体和固体元素和微量元素，包括硝酸盐，磷酸盐，硅硅，氯化物，硫酸盐，NA，MG，MG，MG，AL，AL，V，MN，MN，MN，MN，MN，FE，CO，NI，CU，CU，CU，CU，CU，CU，ZN和CD。此外，科学家将分析气溶胶中的水溶性有机化合物，重点是草酸盐和甲烷 - 磺酸（MSA）等化合物，从而增强了气溶胶痕量元素溶解度。科学家将在气溶胶和上水柱中使用BE-7浓度来计算气雾剂体积沉积速度，并测试我们先前发表的降雨速率与批量沉积速度之间的关系是否可以在更全球化的基础上应用。此外，科学家将使用痕量元素浓度数据以及空气质量后轨迹分析来接近人为和天然来源之间的气溶胶，并研究气溶胶源如何影响分数溶液。将向合作者提供气溶胶和雨子样本，以分析其他重要参数。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估被认为是宝贵的支持。