US GEOTRACES PMT: Shipboard determination of key dissolved trace elements

该项目将在阿拉斯加到塔希提岛的航行中提供溶解微量元素铝（Al），铁（Fe）和锰（Mn）的船上测量，该航行将作为美国GEOTRACES太平洋子午线断面（PMT）的一部分。 PMT探险是国际GEOTRACES计划的一部分，旨在提高对全球海洋地球化学循环的理解。海洋植物在表层沃茨中的生长取决于某些微量元素（特别是溶解的铁）的可用性。 此外，这种和其他微量元素的分布记录了海洋中当前和过去的化学和生物过程。 PMT巡航轨迹包括多种独特的海洋条件，因此工作结果将为不同的全球海洋过程提供重要的见解。为了产生更广泛的科学影响，研究结果将被纳入处理海洋在全球进程中当前和未来作用的模型。对克拉里昂-克利珀顿断裂带内微量元素分布情况的评估，沿着巡航轨迹，也将为计划进行锰结核海底开采的这一区域提供重要的基线。教育推广活动将在夏威夷的希洛中途停留，让当地学生参观该船。直接接触一艘正在工作的海洋学研究船，并在巡航后进行后续访问，将为学生提供一个独特的机会，与参与该项目的科学家直接讨论考察的结果。为了开发所需的数据集，以重新理解微量元素输入过程在建立海洋化学分布方面的相对重要性，在为期六十二天的航行中，将使用专门设计的采样包在四十一个地点采集整个水体的海水样本。巡航轨迹的北方部分起源于一个区域，在该区域，地表沃茨中溶解的铁浓度非常低，限制了植物的生长。 再往南，将通过测量地表沃茨中溶解的铝浓度来追踪从大陆吹来的矿物粉尘的大气沉积增加。 这种粉尘的加入也增加了溶解的Fe。 潜在的额外输入的铁从沿海地区将确定同步增加溶解锰浓度。该项目将比较和关联铝，铁，锰的变化，以量化和识别不同的添加过程沿着巡航轨迹。通过使用船载流动注射分析提供这些微量元素的近实时测量，有可能修改采样策略，以获得最大的科学回报。 船上的结果还将有助于确定在收集这些低水平微量元素时存在的任何采样污染问题。 总之，对这些基本要素的船上分析是确保GEOTRACES PMT成功的一项重要活动。

This project will provide shipboard measurements of the dissolved trace elements aluminum (Al), iron (Fe), and manganese (Mn) during an Alaska to Tahiti cruise that will sail as part of the US GEOTRACES Pacific Meridional Transect (PMT). The PMT expedition is part of the international GEOTRACES program designed to improve understanding of global ocean biogeochemical cycles. The growth of microscopic oceanic plants in surface waters depends on the availability of certain trace elements (particularly dissolved Fe). In addition, the distribution of this and other trace elements record current and past chemical and biological processes in the ocean. The PMT cruise track includes multiple unique oceanic conditions and thus the results of the work will provide important insight into diverse global ocean processes. For broader scientific impact, results will be incorporated into models that address the current and future role of the ocean in global processes. Assessing the distribution of trace elements in the Clarion-Clipperton Fracture Zone, along the cruise track, will also provide an important baseline for this region where seabed mining of manganese nodules is planned. Educational outreach will take place with a mid-cruise stop in Hilo, Hawaii to engage local students with visits to the ship. Direct exposure to a working oceanographic research vessel together with a post-cruise follow up visit will provide students with a unique opportunity to discuss the findings from the expedition directly with the scientists engaged in the project.To develop the data sets required for new understanding of the relative importance of trace element input processes in establishing oceanic chemical distributions, seawater samples from the entire water column will be collected using a custom designed sampling package at 41 locations during the 62-day cruise. The northern part of the cruise track originates in a region where very low concentrations of dissolved Fe in surface waters limit plant growth. Further to the south, increased atmospheric deposition of mineral dust blown from the continents will be traced by measuring the dissolved Al concentration in surface waters. The addition of this dust also adds dissolved Fe. Potential additional inputs of Fe from coastal regions will be identified by coincident increases in dissolved Mn concentrations. The project will compare and correlate variations in Al, Fe, and Mn to quantify and identify distinct addition processes along the cruise track. By using shipboard flow injection analysis to provide near real-time measurements for these trace elements, the potential exists to modify sampling strategies for maximum scientific return. The shipboard results will also help identify any sampling contamination problems that are a constant risk when collecting these low-level trace elements. Altogether, the shipboard analysis of these essential elements is an essential activity to ensure success of the GEOTRACES PMT.