GEOTRACES Atlantic Section: Aerosol and Rainfall collection and analysis

该奖项由《2009年美国复苏和再投资法案》(公法第111-5条)资助。国际地质勘查项目的总体目标是提高我们对世界上具有重要地球化学意义的微量元素及其同位素(TEI)--S海洋--的来源、分布和汇的了解。经过几年的协调和规划，在2008年和2009年的相互校准工作之后，美国地球物理观测系统准备在2010年推进北大西洋部分的工作。地球轨道系统科学计划(2006年)描述了测量TEI浓度和海洋中气溶胶和降雨量沉降量的重要性。气溶胶和降雨沉积可能是北大西洋TEI的一个重要来源，并将受到来自北美和欧洲的人为排放以及来自北非的粉尘排放(“撒哈拉尘埃”)的强烈影响。沙漠尘埃将是铁的重要来源，尽管与人为气溶胶中的铁相比，沙漠尘的溶解度相对较低。北大西洋表层水体中溶解Al和Fe以及Mn和Co(两种重要的生物活性TEI)在大气沉积中显著富集，而溶解铅则在整个北大西洋上层洋区升高。铅同位素可以用来区分北美和欧洲的气团，而钕同位素可以用来限制气溶胶源岩的年龄。北大西洋的大气中硝酸盐和氨的沉积也可能很大，硝酸盐的N和O同位素组成可以用来评估人为来源的贡献。在该奖项的资助下，佛罗里达州立大学的研究人员将在2010年的GEOTRACES北大西洋航段邮轮上收集气溶胶和降雨样本。三个大容量的气溶胶采样器和两个自动雨水采样器已经用之前的NSF资金购买了。它们用于收集酸清洗的Whatman-41(纤维素)过滤器(用于TEI)和预燃石英微纤维(QMA)过滤器(用于有机物种、汞和氮化合物)上的气溶胶。其中一个采样器配备了一个5级西拉式狭缝串级撞击器，用于收集分级气溶胶(从7微米到0.49微米)。在世界各地研究人员的合作下，24小时整合的气溶胶样本和基于事件的降雨样本将被分析用于一大套TEI。该团队和其他合作者将分析所有气溶胶样本，以获得超纯水溶解、海水溶解和总(残留)TEI。将对雨水样本进行分析，包括过滤和未过滤，以量化可溶和颗粒TEI浓度。所有采样日的空气质量反向轨迹将使用NOAA HySplit程序进行建模。此外，来自拖网鱼类和GEOTRACES痕量金属花环采样器的海水样本将使用岸基柱萃取法进行分析，其中包括锰、铁、钴、镍、铜、锌、镉和铅，该方法利用同位素稀释和高分辨率磁区ICPMS。更广泛的影响：研究生的教育和培训是这项研究的重要组成部分。这位首席研究员定期教授本科生和研究生课程，并将他的实地考察结果纳入讲座材料，以激励下一代地球科学家。整个研究团队将从参与大型项目中受益，这些项目将创建多个协作。数据将根据NSF/OCE和GEOTRACES内部校准计划的要求及时提交。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The overall goal of the International GEOTRACES program is to improve our understanding of the sources, distributions, and sinks of geochemically significant trace elements and their isotopes (TEIs) in the world?s oceans. After several years of coordination and planning, and following the 2008 and 2009 intercalibration efforts, US GEOTRACES is ready to move forward with the North Atlantic Ocean Section in 2010. The importance of measuringTEI concentrations and deposition to the oceans for aerosols and rainfall is described in the GEOTRACES Science Plan (2006). Aerosol and rainfall deposition can be a significant source of TEIs in the North Atlantic, and will be strongly affected by anthropogenic emissions from North America and Europe and dust emission from northern Africa ("Saharan dust"). Desert dust will be a significant source of Fe despite the relatively lower solubility compared to Fe in anthropogenic aerosols. Significant enrichment in surface waters of the North Atlantic from atmospheric deposition can be seen in the distributions of dissolved Al and Fe, as well as Mn and Co (two other important bioactive TEIs), while dissolved Pb is elevated throughout the upper ocean in the North Atlantic. Pb isotopes can be used to distinguish North American and European air masses, while Nd isotopes can be used to constrain the ages of aerosol source rocks. Atmospheric deposition of nitrate and ammonia may also be significant across the North Atlantic, and the isotopic N and O composition of nitrate can be used to evaluate anthropogenic source contributions. With funding under this award, researchers at the Florida State University will collect aerosol and rainfall samples on the GEOTRACES North Atlantic section cruise in 2010. Three high-volume aerosol samplers and two automated rain samplers have already been acquired using previous NSF funding. They are used to collect aerosols on acid-cleaned Whatman-41 (cellulosic) filters (for TEIs) and pre-combusted quartz microfiber (QMA) filters (for organic species, Hg, and nitrogen compounds). One sampler is equipped with a 5-stage Sierra-style slotted cascade impactor to collect size fractionated aerosols (from 7 um to 0.49 um). With collaboration from researchers around the world, the 24-hour integrated aerosol samples, and event-based rain samples, will be analyzed for a large suite of TEIs. The team and other collaborators will analyze all aerosol samples for ultra-pure water soluble, seawater soluble, and total (residual) TEIs. Rain samples will be analyzed, both filtered and unfiltered, to quantify the soluble and particulate TEI concentrations. Air mass back-trajectories for all sampling days will be modeled using the NOAA HySplit program. Additionally, seawater samples from the towed-fish and GEOTRACES Trace Metal rosette samplers will be analyzed for Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb using a shore-based column extraction method utilizing isotope dilution and high-resolution magnetic sector ICPMS. Broader Impacts: Education and training of graduate students are essential components of this research. The principal investigator regularly teaches undergraduate and graduate classes and incorporates the results of his fieldwork into lecture materials to motivate the next generation of Earth scientists. The entire research team will benefit from participation in large projects that will create multiple collaborations. The data will be submitted in a timely manner according to the requirements of NSF/OCE and the GEOTRACES Intercalibration program.