Characterization of aragonite and calcite solubility products in seawater using modern CO2 system measurement techniques

碳酸钙是一种矿物（固体），由经济和环境上重要的海洋生物（包括蛤和牡蛎）产生，用于结构支撑和保护免受捕食。由于海洋从大气中吸收二氧化碳，珊瑚礁的结构矿物碳酸钙越来越容易溶解（化学诱导分解）。该项目致力于提高对海洋生态系统具有独特重要性的不同形式碳酸钙稳定性的预测和解释的准确性。固体碳酸钙在海水中的稳定性或不稳定性通常通过（a）测量所收集的海水样品中溶解的化学组分的浓度和（B）计算（数学模型）防止固体碳酸钙溶解所需的海水中溶解的钙和溶解的碳酸盐的量来评估。碳酸钙稳定性建模所需的计算是从实验中产生的，在实验中，固体碳酸钙颗粒被添加到海水样品中，并允许颗粒溶解，直到溶解结束，此后没有观察到颗粒的进一步变化。通过这种实验产生的海水中碳酸钙稳定性的模型对贝类产业很重要，并且对于理解作为经济上重要的海洋生物的食物的含碳酸盐生物的自然化学循环很重要。在过去十年中，贝类产业的经济利益刺激了监测工作，以评估孵化场沃茨中碳酸钙稳定性的日常变化。人们还认识到，碳酸钙稳定性模型对于了解海洋表层作为早期生命阶段鲑鱼基本食物的非常小的生物体的可用性非常重要。目前海水中固体碳酸钙稳定性的模型已有35年以上的历史，并且是使用现代标准认为过时的测量技术生成的。该项目将使用现代最先进的方法来确定海水中固体碳酸钙稳定性所需的化学条件，然后将这些测量结果用于创建在各种盐度和温度下碳酸钙稳定性的定量模型。在推广活动方面，这位科学家计划通过彼得堡科学节和女孩海洋学夏令营的互动模块向公众传播研究结果，并为圣彼得堡彼得堡SciCafe系列准备关于该项目及其与海洋酸化的关系的演讲。 这项研究将支持一名研究生和一名本科生暑期实习生的论文研究。 该项目是对全球海洋中独特的重要矿物碳酸钙（CaCO 3）的溶解度进行的最先进的调查。陆地CaCO 3矿物的风化以碳酸氢盐（HCO 3-）和碳酸盐[CO 3（2-）]的形式增加海水的碱度。海洋表面的海洋钙化物沉淀固体CaCO 3，用于结构支撑和保护免受捕食。海洋钙化菌产生的生物碳酸钙沉淀并溶解在更深的沃茨中。这些过程有时被称为碳酸钙泵，对于将碳从海洋表面转移到深处非常重要。因此，碳酸钙以其固体形式和溶解组分在全球碳循环中发挥着不可或缺的作用。海洋碳酸钙溶解度的评估是必不可少的定量理解和解释固体碳酸钙和其溶解组分之间的转换。CaCO 3溶解度定量表示为与CaCO 3的特定结晶多晶型物平衡时海水中溶解的Ca 2+和CO 3（2-）浓度（mol/kg海水）的乘积（Ksp）。Ksp受海水温度（T）、盐度（S）和压力（P）的影响，用于量化饱和状态（Ω），即海水中溶解的Ca 2+和CO 3（2-）的饱和度。鉴于海洋酸化导致全球海洋中CaCO 3饱和度不断下降，必须对Ksp进行准确的定量评估。除了海洋碳循环模型中Ksp特征的重要性外，Ksp参数化对贝类产业中的水化学评估也至关重要。在过去的十年中，贝类养殖者的经济利益刺激了Ω对贝类健康影响的研究。碳酸钙的溶解度对评估某些渔业的经济效益也很重要。碳酸钙稳定性模型对于了解表层海洋中作为早期生命阶段鲑鱼必需食物的含碳酸盐生物的可用性非常重要。目前海水中固体碳酸钙稳定性的模型已有35年以上的历史，并且是使用现代标准认为过时的测量技术生成的。在本项目中，Ksp将使用现代最先进的pH值、碱度和碳酸根离子浓度测量程序进行测定。这些测量结果将被用于创建Ksp在各种盐度和温度下的定量模型。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Calcium carbonate is a mineral (solid) produced by economically and environmentally important types of marine organisms (including clams and oysters) for structural support and protection from predation. Calcium carbonate, the structural mineral of coral reefs, is becoming increasingly susceptible to dissolution (chemically-induced decomposition) due to the ocean’s uptake of carbon dioxide from the atmosphere. This project is devoted to improving the accuracy of predictions and interpretations of the stability of different forms of calcium carbonate that are uniquely important to the oceanic ecosystem. The stability or instability of solid calcium carbonate in seawater is routinely evaluated from (a) measurements of the concentrations of dissolved chemical components in collected seawater samples and (b) calculations (mathematical models) of the amounts of dissolved calcium and dissolved carbonate in seawater that are required to prevent solid calcium carbonate from dissolving. The necessary calculations for modeling calcium carbonate stability are generated from experiments in which solid calcium carbonate particles are added to seawater samples and the particles are allowed to dissolve until dissolution ends and no further changes in the particles are observed thereafter. The models of calcium carbonate stability in seawater produced through such experiments are important to the shellfish industry and are important to understanding the natural chemical cycles of carbonate-bearing organisms that serve as food for economically-important marine organisms. Over the past decade, the economic interests of the shellfish industry have stimulated monitoring efforts to assess day-to-day changes in the stability of calcium carbonate in hatchery waters. It is also recognized that models of calcium carbonate stability are important to understanding the availability of very small organisms in the surface ocean that serve as an essential food for early-life-stage salmon. Current models of the stability of solid calcium carbonate in seawater are more than thirty-five years old and were generated using measurement techniques that are considered antiquated by modern standards. Modern state-of-the-art methods will be used in this project to determine the chemical conditions required for stability of solid calcium carbonate in seawater, and these measurements will then be used to create quantitative models of calcium carbonate stability over a wide range of salinities and temperatures. For outreach activities, the scientist plans to communicate results from the study to the public via interactive modules at the St. Petersburg Science Festival and the Oceanography Camp for Girls, as well as prepare a presentation for the St. Petersburg SciCafe series about this project and how it relates to ocean acidification. This research will support the dissertation research of one graduate student and an undergraduate summer intern. This project is a state-of-the-art investigation of the solubility of calcium carbonate (CaCO3), a uniquely important mineral in the global ocean. Weathering of terrestrial CaCO3 minerals adds alkalinity to seawater in the form of bicarbonate (HCO3-) and carbonate [CO3(2-)]. Marine calcifiers at the ocean surface precipitate solid CaCO3 for structural support and protection from predation. The biogenic CaCO3 produced by marine calcifiers settles into and dissolves within deeper waters. These processes, sometimes called the calcium carbonate pump, are important for transferring carbon from the surface ocean to depth. As such, calcium carbonate, in both its solid form and dissolved components, plays an integral role in the global carbon cycle. Assessments of marine CaCO3 solubility are essential for a quantitative understanding and interpretation of transformations between solid CaCO3 and its dissolved components. CaCO3 solubility is quantitatively expressed in terms of the product (Ksp) of the dissolved Ca2+ and CO3(2-)concentrations (mol/kg seawater) in seawater at equilibrium with a specified crystalline polymorph of CaCO3. Ksp is influenced by seawater temperature (T), salinity (S), and pressure (P) and is used to quantify saturation state (Ω), the degree to which seawater is under- or over-saturated with dissolved Ca2+ and CO3(2-). In view of the decreasing saturation states of CaCO3 in the global ocean, a consequence of ocean acidification, accurate quantitative assessments of Ksp are essential. In addition to the importance of Ksp characterizations in models of oceanic carbon cycling, Ksp parameterizations are essential to assessments of water chemistry in the shellfish industry. Over the past decade, the economic interests of shellfish growers have stimulated research into the effects of Ω on shellfish health. CaCO3 solubility is also important to assessing the economics of certain fisheries. Models of calcium carbonate stability are important to understanding the availability of carbonate-bearing organisms in the surface ocean that serve as an essential food for early-life-stage salmon. Current models of the stability of solid calcium carbonate in seawater are more than thirty-five years old and were generated using measurement techniques that are considered antiquated by modern standards. In this project, Ksp will be determined using modern state-of-the-art procedures for measurements of pH, alkalinity, and carbonate ion concentrations. These measurements will then be used to create quantitative models of Ksp over a wide range of salinities and temperatures.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.