Assessing the effects of carboxylated amino acids and polysaccharides on the fluid-calcite element partitioning

许多海洋生物都有由碳酸盐矿物组成的精致的骨架和贝壳。氨基酸和碳水化合物等有机分子在调节这些碳酸盐的结构和质地方面起着重要作用。最近的研究表明，某些氨基酸促进镁在碳酸盐的吸收，从而影响整体的化学成分。这些有机分子很可能也会影响其他元素的吸收，尽管这个想法还没有得到验证。通过精心控制的实验室实验，本研究将探讨有机分子对碳酸盐中几种微量元素丰度的影响。海洋生物碳酸盐的微量元素组成被广泛用作推断古代海水温度和化学成分的工具（“代用物”），尽管已知生物过程也会影响贝壳化学成分。这项研究的结果将通过提供对碳酸盐形成的生物控制的见解来提高微量元素代理的可靠性。这将提高我们重建过去海洋动力学、生物学和化学的能力，这是理解地球气候系统的关键。研究成果还应与其他领域相关，如从环境中去除有毒重金属、用于工业用途的新合成材料工程、地质CO2封存等。基于使用pH-stat系统的无机方解石沉淀实验，研究小组将确定在恒定饱和水平下，CaCO3中元素/Ca的比例和沉淀率是否取决于有机分子的类型和浓度，以及取决于多少。研究小组还将通过使用已知的方解石沉淀抑制剂进行额外的实验，确定这种影响是由于沉淀速率的调节（动力学效应）还是由于直接的分子/离子相互作用。该项目为早期职业研究者提供支持，并为夏威夷大学的本科生提供研究机会，夏威夷大学的学生群体具有异常多样化的种族背景。

Many marine organisms build elaborate skeletons and shells made of carbonate minerals. Organic molecules such as amino acids and carbohydrates play important roles in regulating the structure and texture of these carbonates. Recent studies show that certain amino acids enhance magnesium uptake in carbonates and thereby influence the overall chemical composition. It is likely that these organic molecules influence the uptake of other elements as well, though this idea has not been tested. Using carefully controlled laboratory experiments, this study will investigate the effect of organic molecules on the abundance of several trace elements in carbonates. Trace element compositions of marine biogenic carbonates are widely used as tools ("proxies") to infer the temperature and the chemistry of ancient seawater, though it is known that biological processes also influence the shell chemistry. The outcome of this study will improve the reliability of trace element proxies by providing insights into biological controls on carbonate formation. This should advance our ability to reconstruct the dynamics, biology, and chemistry of the oceans in the past, which is a key to understanding the Earth's climate system. The research outcomes should be also relevant to other areas, such as removal of toxic heavy metals from the environment, engineering of new synthetic materials for industrial purposes, and geological CO2 sequestration. Based on inorganic calcite precipitation experiments using a pH-stat system, the research team will determine if and by how much element/Ca ratios in CaCO3 and precipitation rates depend on the types and concentrations of organic molecules at a constant saturation level. The research team will also address whether such effects are due to modulation of precipitation rates (kinetic effects) or due to direct molecular/ionic interactions by performing additional experiments using a known calcite precipitation inhibitor. This project provides support for an early-career investigator as well as research opportunities for undergraduate students at the University of Hawaii, where the student population has an exceptionally diverse ethnic background.