Collaborative Research: Impact of Atmospheric Deposition on the Distribution and Speciation of Trace Elements in the Upper Ocean - Focus on Iron in the Sargasso Sea

最近对马尾藻海(BATS地区)的研究表明，表层水中的溶解铁(Fe)浓度有很大的季节性变化，从2003年夏季气溶胶Fe浓度高时的~1-2 nm下降到2004年春季气溶胶Fe浓度低时的~0.1-0.2 nm。这些变化被解释为夏季季节性沙尘输入高度层化、营养稀缺的表层水域，然后在冬早春对流混合、生物吸收和颗粒清除导致风成铁的清除。来自百慕大生物研究所、特拉华大学和伍兹霍尔海洋研究所的研究人员设计了一个简单的模型，该模型表明，风沙输入到表层海洋的溶解铁不会随着气溶胶总铁浓度的变化而变化。为了验证这一假说，科学家们将利用马尾藻海作为一个天然实验室，以实现下列目标：(1)定量了解矿物气溶胶沉积(干和湿)对马尾藻海表层水中铁的浓度和形态的影响；(2)测试为马尾藻海开发的新的气溶胶铁溶解度模型，从而评估该模型在全球范围内应用的可能性；(3)评估对安装在浮标上的自主气溶胶采样器的需求，以量化开放海洋上气溶胶铁的浓度和溶解度。为了实现这些目标，将进行时间序列观测和深入的过程研究。这项工作将包括船上水柱采样、百慕大都铎山塔的大气采样、在百慕大试验床系泊上使用自动气溶胶采样器，以及随后分析海水、气溶胶和雨水样品中铁和其他痕量金属的浓度和形态。至于更广泛的影响，这项研究将提供必要的数据，以改进生物地球化学-生态系统模型的预测能力。此外，该项目还将记录安装在浮标上的自主气溶胶采样系统的用途，该系统将大气和海洋过程连接起来，用于海洋地球化学和生物地球化学方面的环境监测和研究。这项研究的目标与SOLAS和GEOTRACES计划的重点是一致的。来自特拉华大学的一名研究生和一名本科生(作为REU计划的一部分得到资助)将作为该项目的一部分接受培训。

Recent studies in the Sargasso Sea (BATS region) have revealed a large, seasonal-scale change in the dissolved iron (Fe) concentration of the surface waters where concentrations decreased from ~1-2 nM in summer 2003, when aerosol Fe concentrations were high, to ~0.1-0.2 nM in spring 2004, when aerosol Fe concentrations were low. These changes were interpreted as the result of the seasonal dust input into the highly-stratified, oligotrophic surface waters during the summer, followed by the removal of this aeolian iron due to the convective mixing, biological uptake and particle scavenging during the winter-early spring. Researchers from the Bermuda Biological Station for Research, the University of Delaware and Woods Hole Oceanographic Institute have devised a simple model that implies that aeolian input of dissolved Fe into the surface ocean does not scale with total aerosol Fe concentrations. To test this hypothesis, the scientists will use the Sargasso Sea as a natural laboratory to carry out the following objectives: (1) achieve a quantitative understanding of the impact of mineral aerosol deposition (dry and wet) on the concentration and speciation of Fe in surface waters of the Sargasso Sea; (2) test the new model for aerosol Fe solubility that have been developed for the Sargasso Sea, and thus evaluate the potential for application of this model at the global scale; and (3) evaluate the need for an autonomous, buoy-mounted aerosol sampler for quantifying the concentration and solubility of aerosol iron over the open ocean. To attain these goals, both time-series observations and intensive process studies will be done. The work will include shipboard water-column sampling, atmospheric sampling at the Tudor Hill tower on Bermuda, the use of an autonomous aerosol sampler on the Bermuda Testbed Mooring, and subsequent analyses of the concentration and speciation of Fe and other trace metals in seawater, aerosol, and rainwater samples. As regards broader impacts, this study will provide needed data to improve predictive capabilities of biogeochemical-ecosystem models. In addition, this project will document the utility of an autonomous, buoy-mounted aerosol sampling systems linking atmospheric and oceanographic processes for environmental monitoring and research in marine geochemistry and biogeochemistry. The goals of this research are compatible with the focus of the SOLAS and GEOTRACES programs. One graduate student and one undergraduate student (funded as part of the REU program) from the University of Delaware will be trained as part of this project.