Investigating YREE Co-Precipitation with Phosphate and Biogenic Aragonite as Possible Indicators of Ocean Acidification

该奖项由2009年美国复苏和再投资法案（公法111-5）资助。马里兰州大学的研究人员将进行钇和稀土元素（YREE）的碳酸盐共沉淀和磷酸盐络合的实验室研究。 预计这些过程对pH值的微小变化很敏感，因此海洋酸化的变化可能对其化学性质产生影响。 YREE在海水中以碳酸盐为主的溶液形态，碳酸盐和磷酸盐都形成已知含有这些元素的生物矿物。 许多生物和地质碳酸盐和磷酸盐增生的YREE的相对浓度已被解释的“生命”和成岩作用。 然而，这些解释需要理解的基本原理的YREE吸附过程中，这是目前缺乏的。 在本项目期间将进行的实验提供了一个理论框架，对生物成因文石中的YREE/Ca比值的解释。 特别是，这项研究将有助于评估它们对pH值的依赖性以及作为海洋酸化指标的潜在用处。 海洋的逐渐酸化从根本上降低了海水中文石和方解石的饱和状态。 虽然大多数海洋酸化研究关注的是对钙化生物健康的直接后果，但人们日益认识到，其他海洋地球化学循环可能以各种方式受到影响，例如通过微量金属的化学形态和表面反应性的变化。 这项研究的焦点元素，由于其纳入生物矿物，可能会作为记录器的海水pH值的历史地质时间尺度。更广泛的影响：钇和稀土元素分馏模式、丰度异常和放射性同位素一直被用作地球化学工具。 在地质和环境科学的许多分支中发现了许多应用，并且不断出现新的应用。 鉴于碳酸盐和磷酸盐矿物在海洋和陆地系统中的广泛重要性，预计这项研究产生的见解将与当前低温地球化学中的许多问题具有广泛的相关性。 PI收集翼足类动物外壳材料将涉及参与两个前往东北太平洋的研究任务，这将允许与加拿大科学家合作。 这项工作将涉及研究生培训，并提供向公众进行教育宣传的机会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Researchers at the University of Maryland will conduct a laboratory study of carbonate co-precipitation and phosphate complexation of yttrium and the rare earth elements (YREEs). These processes are anticipated to be sensitive to minor pH variations, thus changes in ocean acidification could play a role in their chemistry. YREEs have carbonate-dominated solution speciation in seawater, and carbonate and phosphate both form biogenic minerals that are known to contain these elements. The relative concentrations of YREE in many biogenic and geological carbonate and phosphate accretions have been interpreted in terms of 'vital' and diagenetic effects. However, these explanations require an understanding of the basic principles underlying the YREE adsorption process, which is presently lacking. The experiments that will be conducted during this project provide a theoretical framework against which interpretations of YREE/Ca ratios in biogenic aragonite can be made. In particular, this research will allow an assessment of their pH dependence and potential usefulness as indicators of ocean acidification. Progressive acidification of the oceans essentially lowers the saturation states of aragonite and calcite in seawater. While most ocean acidification studies are concerned with the immediate consequences for the health of calcifying organisms, there is a growing awareness that other marine geochemical cycles may be affected in various ways, for example through shifts in the chemical speciation and surface reactivity of trace metals. The focal elements for this study, by virtue of their incorporation into biogenic minerals, might act as recorders of seawater pH on historic to geological time scales. Broader Impacts: Yttrium and the rare earth element fractionation patterns, abundance anomalies, and radiogenic isotopes have long been utilized as geochemical tools. Numerous applications are found across many branches of the geological and environmental sciences and new ones continue to emerge. In view of the widespread importance of carbonate and phosphate minerals in marine and terrestrial systems, the insights generated from this study are expected to be of broad relevance to many current problems in low-temperature geochemistry. The collection of pteropod shell material by the PI will involve participation in two research missions to the Northeast Pacific Ocean, which would allow for collaboration with Canadian scientists. The work will involve graduate student training and offers opportunities for educational outreach to the general public.