Experimental Determination of Temperature and Precipitation Rate Effects on Element Partitioning Between Aragonite and Seawater

海洋无脊椎动物文石骨骼的元素组成在用于了解和模拟地球气候系统的气候替代数据中所占比例越来越大。然而，控制元素在文石和海水之间分配的因素还不是很清楚。到目前为止，只有三项实验研究确定了文石和海水之间的元素分配，都只关注Sr2+的行为，其中两项是在同一温度下进行的。在这个项目中，伍兹霍尔海洋研究所的研究人员将通过实验确定一系列二价阳离子(例如，镁、锶、Ba2+、镉和锰)作为环境替代品的文石-海水分配系数，以解决这一关键的知识差距。实验数据将被用来校准晶格应变分配模型，该模型将为解释文石骨架的组成提供定量基础。此外，将实验结果与从精选的自然生成的文石中获得的数据进行比较，将有助于识别最真实地记录环境变量的代用品和文石吸积物的组合。这项拟议的工作建立在一项试验性初步研究结果的基础上，该研究旨在确定在15-45℃下非生物成因文石和海水之间的分配。该方法与以前的研究不同，因为SIMS离子微探针将用于分析单个文石颗粒中各种二价阳离子的浓度，而不是仅关注使用块状沉淀物进行锶的分配。SIMS分析提供的高空间分辨率允许识别单个颗粒上存在的成分梯度，以及可能从高镁钙石外延转化而来的文石的存在。这项研究有望产生许多更广泛的影响。有理由相信，这项研究将为古气候、地球化学、生物和环境保护界提供一个定量的基础，以解释保存在现存和古代文石增生体中的成分记录，这是目前无法获得的。它将架起传统学科界限的桥梁，并将拥有截然不同但互补的专业知识的科学家聚集在一起。此外，这项研究将对NSF研究生的博士论文做出重要贡献。该项目还将为研究生和暑期学生研究员提供教育和培训。这项研究的结果将及时在调查人员的网站上公布。

The elemental composition of the aragonitic skeletons of marine invertebrates contribute an increasingly significant proportion of the climate proxy data used to understand and model Earth's climate system. However, the factors that control how elements are partitioned between aragonite and seawater are not well understood. To date only three experimental studies have determined element distribution between aragonite and seawater, all focused exclusively on the behavior of Sr2+ and two were carried out at a single temperature. In this project, researchers at the Woods Hole Oceanographic Institution will address this critical gap in knowledge through an experimental determination of aragonite- seawater partition coefficients for a range of divalent cations that show promise as environmental proxies (e.g., Mg2+, Sr2+, Ba2+, Cd2+, and Mn2+) as functions of temperature and precipitation rate. The experimental data will be used to calibrate a lattice strain partitioning model that will provide a quantitative basis for interpreting the compositions of aragonitic skeletons. In addition, a comparison of experimental results with data obtained from selected, naturally occurring aragonites will permit identification of combinations of the proxies and aragonite accretions that most faithfully record environmental variables. The proposed work builds on results from an experimental pilot study to determine the partitioning of Mg2+, Ca2+, Sr2+, and Ba2+ between abiogenic aragonite and seawater at 15 to 45 C. This approach differs from previous studies in that the SIMS ion microprobe will be used to analyze the concentrations of a full range of divalent cations in individual aragonite grains, rather than focusing exclusively on Sr partitioning using the bulk precipitate. The high spatial resolution afforded by SIMS analyses allows recognition of the presence of compositional gradients across individual grains, and the presence of aragonite that may have been epitaxially converted from high-Mg-calciteThis research promises a number of broader impacts. There is reason to believe that this research will provide the paleoclimate, geochemical, biological and environmental conservation communities with a quantitative basis for interpreting the compositional record preserved in living and ancient aragonitic accretions, which is presently unavailable. It will bridge traditional disciplinary boundaries and bring together scientists with very different but complementary expertise. Moreover, this study will contribute significantly toward the PhD thesis of NSF graduate student fellow. This project will also provide for the education and training of graduate and summer student fellows. The results from this study will be made publicly available in a timely manner on the investigators' website.