Hawaii Aerosol Time-Series (HATS):Quantifying Marine Dust Deposition and Composition in an Oligotrophic Gyre

海洋的化学性质可以通过引入和去除元素而改变，包括低浓度的微量元素。在某些情况下，已知这些元素对生物过程和海洋食物网至关重要。在海岸附近，河流是从陆地到海洋的物质的主要来源。在河流所及范围之外，对大多数海洋来说，从陆地通过空气吹来的物质是地表沃茨微量元素的最大来源。这种物质通过溶解在雨水中或通过尘埃颗粒的沉降进入海洋。因此，了解海洋微量元素的大气来源对于了解全球化学循环和生物生产模式都很重要。该项目将在两年内对夏威夷附近的大气和海洋表层进行采样，以更深入地了解海洋中微量金属的来源和归宿。这项研究将研究来自大气的颗粒在海洋中下沉时如何与周围的水相互作用。该项目将有助于全球综合和建模工作。它将直接支持研究生和本科生。该项目的结果及其相关性将通过校园开放日活动和公开讲座系列传达给公众。海洋中微量元素的供应和去除过程是正在进行的研究领域。一个重要的重点是了解沉积到海洋的气溶胶微量元素的来源和归宿，因为这是进入公海的微量营养素和污染物的主要来源。湿和干大气输入的实地观测数量有限，很少有方法可以将容易测量的气溶胶微量元素浓度转化为沉积通量。因此，大气中微量元素向大多数海洋区域的流动仍然没有受到很好的限制，它们对海洋生物化学循环，包括海洋碳循环的影响也不确定。直接量化关键微量元素向海洋的大气通量，并确定其沉积后的命运和化学转化是继续调查的关键领域，并被列为GEOTRACES计划的核心组成部分。同样，气溶胶的溶解度分数和生物可利用的微量元素的流量也没有得到很好的理解。相应地，有必要测试和改进对总尘埃沉降通量的估计，同时对开阔海洋中的颗粒组成进行观测。该项目将通过为期两年的陆上取样工作和旨在完成三项任务的六次季节性航行来满足这些需要。(1)使用从气溶胶，降水和上层海洋库存测量的铍-7的沉积通量直接估计灰尘和气溶胶微量元素通量的夏威夷海洋时间序列站阿罗哈，一个代表性的和远程贫营养的网站。这一区域的特点是尘埃浓度和降水量具有可预测的季节性变化，是一个特别适用于通过观察多年周期内海洋-大气耦合的季节性变化来测试尘埃沉积技术极限的区域。(2)探索气溶胶微量元素通量到北太平洋表面的季节性变化的程度，以及该输入的矿物学驱动海洋颗粒成分和库存的变化。(3)调查在北太平洋上空收集的气溶胶微量元素的溶解度分数显示时间变化的程度，并计算可溶性气溶胶微量元素的通量率。该研究将促进对从大气到海洋的尘埃和可溶性气溶胶微量元素通量的理解，并将该通量与上层海洋颗粒物清单、矿物学和化学成分联系起来。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The chemistry of the ocean can be changed by the introduction and removal of elements, including trace elements which are present at low concentrations. In some cases, these elements are known to be vital to biological processes and ocean food webs. Near the shore, rivers are a large source for material from land to the ocean. Beyond the reach of rivers, and for most of the oceans, material blown from land through the air is the largest source of trace elements to surface waters. This material enters the oceans dissolved in rain or by settling of dust particles. Understanding atmospheric sources of trace elements to the oceans is thus important to understanding both global chemical cycles and patterns of biological production. This project will sample the atmosphere and the surface ocean near Hawaii over two years to gain a deeper understanding of the sources and fates of trace metals in the ocean. The study will examine how particles from the atmosphere interact with the surrounding water as they sink through the ocean. The project will contribute to global synthesis and modeling efforts. It will directly support graduate and undergraduate students. Results of the project and their relevance will be communicated to the public through campus open house events and a public lecture series.The processes that supply and remove trace elements in the ocean are ongoing areas of research. An important focus is on understanding the sources and fate of aerosol trace elements deposited to the ocean as this represents a major source of micronutrients and contaminants into the open ocean. Field observations of wet and dry atmospheric inputs are limited in number, and few methods are available to transform readily measured aerosol trace element concentrations into deposition fluxes. Thus, atmospheric fluxes of trace elements to most ocean regions remain poorly constrained and their impact on ocean biochemical cycles, including the marine carbon cycle, are uncertain. Directly quantifying atmospheric fluxes of key trace elements to the ocean and identifying their fates and chemical transformations after deposition are critical areas of continued investigation and are included, for example, as a core component of the GEOTRACES program. Similarly, aerosol fractional solubility and the flux of bioavailable trace elements is not well understood. There is a corresponding need to test and improve estimates of total dust deposition fluxes alongside simultaneous observations of particle composition in the open ocean. This project will address these needs through a two-year land-based sampling effort and six seasonal cruises aimed at three tasks. (1) Use the deposition flux of beryllium-7 measured from aerosols, precipitation, and the upper ocean inventory to directly estimate dust and aerosol trace element fluxes to the Hawaii Ocean Time-series Station Aloha, a representative and remote oligotrophic site. This region is characterized by a predictable seasonal variability in dust concentrations and precipitation and is an exceptionally applicable region for testing the limits of dust deposition techniques by observing seasonal variability in ocean-atmosphere coupling over a multi-year cycle. (2) Explore the extent to which seasonal variations in aerosol trace element flux to the surface of the North Pacific, and mineralogy of that input drive variability in the composition and inventories of marine particles. (3) Investigate the extent to which the fractional solubility of aerosol trace elements collected over the North Pacific shows temporal variability and calculate flux rates of soluble aerosol trace elements. The study will advance understanding of dust and soluble aerosol trace element flux from the atmosphere to the ocean and link that flux to upper ocean particle inventory, mineralogy, and chemical composition.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.