THE CHEMICAL SPECIATION OF MARINE PARTICULATE IRON: IMPLICATIONS FOR SOURCE AND

海洋颗粒铁的化学形态：对来源和来源的影响

• 批准号: 7722084
• 负责人: Phoebe J Lam
• 金额: $ 0.11万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7722084
• 关键词: Address; Amyotrophic Lateral Sclerosis; Area; Biological Availability; Chemicals; Computer Retrieval of Information on Scientific Projects Database; Data; Data Set; Depth; Detection; Funding; Grant; Heterogeneity; Institution; Iron; Marines; Measurement; Micronutrients; Oceans; Particulate; Productivity; Reporting; Research; Research Personnel; Resources; Role; Sampling; Source; Spottings; Surface; Synchrotrons; Techniques; United States National Institutes of Health; beamline; size

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Iron is the most important micronutrient in the ocean, and limits productivity in large areas of the ocean. Of the total iron in the open ocean, up to 90% is found in the particulate form. Little is known about the chemical speciation of particulate iron, however, hampering understanding of its bioavailability and of its role in the global cycling of iron. Synchrotron XAS is an ideal technique to probe the speciation of particulate iron. I have already collected an extensive dataset (>200 XANES spectra) on particulate Fe speciation in the open ocean using a microprobe synchrotron beamline at the ALS (beamline 10.3.2). It is already obvious that there is enormous heterogeneity in particulate iron speciation in my dataset, and this has never before been reported. The u-XANES data suggest that the iron at ~150m, or the depth of the continental shelf, may be more reduced than iron at the surface or deeper down. This reduced iron coincides with a maximum in Fe concentrations, suggested a plume of reduced iron supplied to this depth. While u-XAS is in some ways an easier measurement, since the incident beam can be preferentially directed at high-Fe regions in the sample, the high heterogeneity between spots of each sample hampers our ability to make conclusions about overall differences in speciation between depths and between size fractions. Sample to sample differences are better addressed with bulk XAS analyses, since they average over a much larger area than microprobe beamlines do. Because of the higher spot size, however, the effective overall concentration will be far lower, and questions of detection limit become an issue. I therefore seek exploratory beamtime at SSRL to supplement my microprobe dataset with bulk Fe K-edge XANES and EXAFS data to see whether a bulk XAS measurement is feasible on these samples. If the Fe levels of my samples are too low for EXAFS, XANES will still be very useful for determining sample to sample difference in Fe valence.

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 铁是海洋中最重要的微量营养素，限制了大面积海洋的生产力。在开阔海洋中，高达90%的铁以颗粒形式存在。然而，对颗粒铁的化学形态知之甚少，阻碍了对其生物利用度及其在全球铁循环中的作用的理解。 同步辐射XAS技术是研究颗粒态铁形态分布的理想技术。我已经收集了一个广泛的数据集（>200 XANES光谱）微粒铁形态在公海使用微探针同步加速器光束线在ALS（光束线10.3.2）。 很明显，在我的数据集中，颗粒铁形态存在巨大的异质性，这是以前从未报道过的。u-XANES数据表明，150米或大陆架深度的铁可能比表面或更深处的铁还原得更多。这种还原铁与Fe浓度的最大值相一致，表明有还原铁羽流供应到该深度。 虽然u-XAS在某种程度上是一种更容易的测量，因为入射光束可以优先指向样品中的高铁区域，每个样品的斑点之间的高度异质性阻碍了我们对深度之间和粒度级之间的物种形成的总体差异做出结论的能力。通过批量XAS分析可以更好地解决样本之间的差异，因为它们的平均面积比微探针束线大得多。 然而，由于更大的斑点尺寸，有效的总浓度将低得多，并且检测极限的问题成为一个问题。 因此，我在SSRL寻求探索性的束时间，以补充我的微探针数据集与散装铁K-边缘XANES和EXAFS数据，看看散装XAS测量是否对这些样品是可行的。如果我的样品的铁水平太低，EXAFS，XANES将仍然是非常有用的，以确定样品之间的差异，在铁价。