Inferring trace element inputs to North Pacific surface waters from Alaskan and Asian dust

推断阿拉斯加和亚洲尘埃对北太平洋地表水的微量元素输入

• 批准号: 1756126
• 负责人: James Murray
• 金额: $ 29.15万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756126&HistoricalAwards=false
• 关键词: Inferring; trace; element; inputs; North

An important part of understanding chemical cycling in the ocean is understanding the processes that deliver elements and nutrients to or remove them from the oceans. The atmosphere can be an important source of material from rain and from dust. In some parts of the oceans, input of elements such as iron from dust (and possibly rain) can play an important role in stimulating the growth of phytoplankton, the base of the marine food chain. This study will involve collection and analysis of a two-year time-series of filtered air samples from two locations in the subarctic North Pacific, aimed at understanding the inputs of metals to the ocean surface from Alaskan and Asian dust and from fossil fuel combustion. The dust time series observations and analyses proposed will provide insight that will aid the interpretation of observations from the 2018 U.S. GEOTRACES Pacific Meridional Transect expedition. This project will support a graduate student for two years and will be the basis of his or her Ph.D. research.The investigators will collect atmospheric dust samples from two land-based locations well suited to capture the flux to surface waters of the subarctic North Pacific. One is on the northern side of the Aleutian chain, and the second is an island to the northeast (Middleton Island), at the shelf break, in the northern Gulf of Alaska. Sampling will be carried out year round at Middleton Island using an automated sampling system, while high-volume sampling will be carried out for one month at each of the two locations during targeted known seasonal events. These will help infer and characterize inputs from Asian dust, known to occur primarily in the spring, and from Alaskan dust, known to occur primarily in the autumn. Samples from large events will be made available to the GEOTRACES research community for analyses. The HYSPLIT model will be used to simulate dust transport and deposition, for comparison to observations. Previous work documents substantial interannual variability in dust fluxes from Alaska and from Asia, and volcanic ash input is even more variable. Given the seasonality and interannual and spatial variability of the dust sources, and the short residence time of Fe and other trace elements and isotopes in surface waters, this history of deposition from dust and fossil fuel combustion, and its geochemical characterization, will help to distinguish the various inputs more comprehensively than is possible with a single research cruise.
A variety of size fractions will be collected and analyzed to infer the particle size range that contains each of the metals. Analyses will be carried out on over twenty elements, including Fe, Al, the REE, the isotopes of Pb, Sr and Nd (the tracers that best distinguish the dust source end members), and metals including V and Ag to infer contributions from fossil fuel combustion. Activities in air of the natural radionuclides lead-210 and beryllium-7, and their depositional fluxes, will be determined to convert elemental concentrations in dust into flux estimates to surface waters. Experiments will evaluate the control of different organic ligands on the solubility of iron and other metals in surface seawater, the relative solubility of different size fractions, and the relative solubility of dust- versus fossil fuel-derived metals.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.

了解海洋化学循环的一个重要部分是了解向海洋输送元素和营养物质或将其从海洋中移除的过程。大气是雨水和灰尘等物质的重要来源。在海洋的某些地区，来自尘土（可能还有雨水）的铁等元素的输入可以在刺激浮游植物生长方面发挥重要作用，浮游植物是海洋食物链的基础。这项研究将包括收集和分析北太平洋亚北极地区两个地点过滤空气样本的两年时间序列，旨在了解来自阿拉斯加和亚洲灰尘以及化石燃料燃烧的金属对海洋表面的输入。提出的尘埃时间序列观测和分析将提供有助于解释2018年美国GEOTRACES太平洋经向样带考察观测结果的见解。该项目将支持研究生两年，并将成为他或她的博士研究的基础。研究人员将从两个陆地地点收集大气尘埃样本，这两个地点非常适合捕捉北太平洋亚北极地表水的通量。一个位于阿留申岛链的北侧，另一个位于东北的一个岛屿（米德尔顿岛），位于阿拉斯加湾北部的大陆架断裂处。米德尔顿岛将全年使用自动采样系统进行采样，而在已知的目标季节性事件期间，将在两个地点各进行一个月的大量采样。这将有助于推断和描述主要出现在春季的亚洲沙尘和主要出现在秋季的阿拉斯加沙尘的输入。来自大型活动的样本将提供给GEOTRACES研究团体进行分析。HYSPLIT模式将用于模拟尘埃的输送和沉积，以便与观测结果进行比较。先前的工作记录了来自阿拉斯加和亚洲的沙尘通量的年际变化，而火山灰输入的变化甚至更大。考虑到沙尘源的季节性、年际和空间变异，以及铁和其他微量元素和同位素在地表水中的短暂停留时间，这一沙尘和化石燃料燃烧沉积的历史及其地球化学特征，将有助于比单一的研究巡航更全面地区分各种输入。将收集和分析各种尺寸分数，以推断包含每种金属的粒度范围。将对20多种元素进行分析，包括铁、铝、稀土、Pb、Sr和Nd的同位素（最能区分粉尘源端成员的示踪剂），以及包括V和Ag在内的金属，以推断化石燃料燃烧的贡献。将测定天然放射性核素铅-210和铍-7在空气中的活动及其沉积通量，以将尘埃中的元素浓度转化为地表水通量估算值。实验将评估不同有机配体对铁和其他金属在表层海水中的溶解度的控制，不同大小馏分的相对溶解度，以及粉尘与化石燃料衍生金属的相对溶解度。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。

项目成果

Dissolved Fe Supply to the Central Gulf of Alaska Is Inferred to Be Derived From Alaskan Glacial Dust That Is Not Resolved by Dust Transport Models

• DOI: 10.1029/2021jg006323
• 发表时间: 2021-06-01
• 期刊: JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
• 影响因子: 3.7
• 作者: Crusius, John