U.S. GEOTRACES PMT: Measurement of the organic complexation and chemical lability of dissolved copper using multiple techniques

铜是海洋中的一种元素，是生命所必需的。与海洋生物吸收的许多元素一样，铜在海水中的浓度很低；然而，铜在水柱中的分布与其他生物必需元素不同。这种差异可能归因于海水中残留部分几乎是惰性的。这个项目试图了解这种材料是什么，为什么它如此不具反应性，以及它最终是如何被“破解”并重新进入生物循环的。南加州大学(USC)的一位科学家将在美国GEOTRACES太平洋子午线(PMT)巡航期间描述铜的化学特征。这艘邮轮是从阿拉斯加到塔希提岛的南北横断面，横跨广泛的水深、温度、生物和化学。铜的测量将与许多其他具有不同化学成分的痕量元素一起进行。通过比较它们的行为，再加上对每种元素的了解？S的化学性质，这位科学家将进一步了解是什么控制了海洋中铜的行为。计划对研究生和优秀本科生进行物种形成技术培训。这些研究生还将通过南加州大学青年调查项目指导市中心学校的高中生。这次巡航及其发现将被纳入南加州大学教授的外展活动和课程中，包括为非理科专业的学生开设的通识课程。南加州大学的一名科学家假设，在高清道夫地区，不稳定的复合体将占主导地位，不稳定的形式将在不稳定的本底水池上方的较老的深水中积累。为了量化化合物的分布和化学性质，将使用两种不同的基于竞争性配体交换的形态形成技术。第一种是吸附阴极溶出伏安法，在以前的GEOTRACES切片上使用过。第二种是研究人员开发的基于配体交换的液/液分配方法。分配导致与竞争配体反应或不反应的组份的物理分离，允许通过使用铜-65作为示踪剂来交换强络合铜。示踪剂使更慢的反应能够在实验中研究。样品将用电感耦合等离子体质谱进行同位素稀释分析。南加州大学的一位同事(Seth John)还将为非稳定性铜的天然铜同位素分析准备样品，以检验非稳定性或半稳定性络合物对海水中溶解的铜的重同位素特征有贡献的假设。PMT能够从海洋传送带末端的深水中收集大量样品，以及颗粒金属和清除的同位素示踪剂的数据。此外，活性铜和非活性铜之间的关系可以在几个不同的生物群中进行研究，包括沿PMT的高营养、低叶绿素区域和低营养亚热带环流。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Copper (Cu) is an element in the ocean that is essential for life. Like many elements taken up by marine life, its concentrations in seawater are very low; however, Cu has a distribution in the water column that is different from other biologically essential elements. This difference may be attributed to the presence of a residual fraction in seawater that is virtually inert. This project seeks to understand what this material is, why it is so unreactive, and how it can eventually be 'cracked" and re-enter the biological cycle. A scientist from the University of Southern California (USC) will characterize the Cu chemistry during the US GEOTRACES Pacific Meridional Transect (PMT) cruise. This cruise is a north-south transect from Alaska to Tahiti that spans a wide range of water depths, temperatures, biology, and chemistry. The Cu measurements will be made alongside many other trace elements that have different chemistries. By comparing their behavior, coupled with the knowledge of each element?s chemical properties, the scientist will further our knowledge of what controls the behavior of Cu in the ocean. Training of graduate students and outstanding undergraduates in the speciation techniques is planned. The graduate students will also mentor high school students from inner city schools through the USC Young Investigators Program. The cruise and its findings will be incorporated into outreach activities and courses taught at USC, including a general education class for non-science majors.A scientist from USC hypothesizes that non-labile complexes will predominate in high-scavenging regimes and that labile forms will accumulate in older deep waters above a non-labile background pool. To quantify the distribution and chemical properties, two different speciation techniques will be used based on competitive ligand exchange. The first, adsorptive cathodic stripping voltammetry, was used on previous GEOTRACES sections. The second is based on a ligand exchange, liquid/liquid partition methodology developed by the researcher. Partitioning leads to physical separation of fractions that are reactive or not with the competitive ligand allowing the exchangeability of strongly complexed copper by using Cu-65 as a tracer. The tracer enables much slower reactions to be studied experimentally. Samples will be analyzed using isotope dilution by inductively coupled plasma-mass spectrometry. Samples will also be prepared for natural Cu isotope analysis of non-labile Cu by a colleague at USC (Seth John) to test the hypothesis that non-labile or semi-labile complexes contribute to the heavy isotope signature of dissolved Cu in seawater. The PMT enables high volume sample collection from deep waters at the terminus of the oceanic conveyor belt, along with data for particulate metals and isotope tracers of scavenging. Moreover, the relationship between labile and non-labile Cu can be studied over several distinct biomes, including high-nutrient, low chlorophyll regions and oligotrophic subtropical gyres along the PMT.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.