NSFOCE-BSF: Collaborative Research: The Role and Mechanisms of Nuclei-induced Calcium Carbonate Precipitation in the Coastal Carbon Cycle: A First In-depth Study

碳酸钙（CaCO3）在海水中的形成是海洋碳循环的一个基本途径。碳酸钙的形成可以通过生物生产（生物形成外壳或骨骼材料的钙化）或通过非生物（非生物或化学）过程发生。尽管开阔水域和沿海水域的大多数表层海水碳酸钙含量过饱和，但有几个因素抑制了碳酸钙的非生物生产。因此，目前的范式是海水中大多数碳酸钙的形成是生物的。然而，实验室实验表明，在过饱和海水中加入固相颗粒，通过为沉淀提供“种子”，促进了核诱导CaCO3沉淀（NICP）。在小巴哈马浅滩富caco3沉积物的再悬浮过程中，NICP已被证实。直到最近，基本上没有证据表明NICP发生在悬浮颗粒CaCO3含量相对较低的典型海洋系统中。该项目的以色列合作伙伴最近进行的一项研究提供了证据，表明NICP可能在红海的碳预算中发挥重要作用，这是由于山洪暴发和可能通过空气传播的粉尘引起的颗粒物质流入造成的。这一发现提示NICP可能是海洋碳循环中被忽略的重要CaCO3形成途径。该项目的目标是进行第一次全面、深入的研究，以评估NICP在海洋中的意义。该项目是美国和以色列科学家之间的一项国际合作，由美国国家科学基金会和美以两国科学基金会共同资助。博士后研究人员，其博士工作构成本研究的基础，将通过本项目得到支持。本项目将指导和培训一名以色列硕士生和一名美国少数民族本科生实习生。该项目将采用综合方法来评估可能导致NICP的不同机制，包括河流沉积物输入、山洪引发的陆地颗粒流入、底部沉积物再悬浮和大气粉尘输入。实地调查将在一系列沿海环境中进行：红海北部，密西西比河和萨宾河羽流和墨西哥湾北部的加尔维斯顿湾，每个地方都有大量的非碳酸盐丰富的沉积物。调查人员还将进行有控制的实验室实验，以核实和扩大实地观察。如果NICP被证明是重要的，这一发现可以促进对碳循环的重要部分和海洋碳系统对持续扰动的响应的重新检查。

The formation of calcium carbonate (CaCO3) in seawater is a fundamental pathway in the marine carbon cycle. Calcium carbonate formation may occur through biological production (calcification by organisms building shells or skeletal material) or through non-biological (abiotic, or chemical) processes. Although most surface seawater in both open and coastal waters is supersaturated in calcium carbonate, several factors inhibit the abiotic production of calcium carbonate. Therefore the current paradigm is that most calcium carbonate formation in seawater is biological. However, laboratory experiments have demonstrated that addition of solid-phase particles to supersaturated seawater promotes nuclei-induced CaCO3 precipitation (NICP) by providing "seeds" for precipitation. NICP has been demonstrated in the Little Bahama Banks during events of re-suspension of CaCO3-rich sediments. Until very recently, essentially no evidence has shown that NICP occurs in typical marine systems where suspended particles have relatively low CaCO3 content. A recent study by the Israeli partners in this project provides evidence that NICP may play a significant role in the carbon budget in the Red Sea, as a result of an influx of particulate material caused by flash floods and potentially airborne dusts. Such a finding suggests that NICP may be an important CaCO3 formation pathway that has been mostly ignored in the ocean carbon cycle. The goal of this project is to conduct the first comprehensive, in-depth study to evaluate the significance of NICP in the oceans. The project is an international collaboration between U.S. and Israeli scientists, jointly funded by NSF and the U.S.-Israel Binational Science Foundation. A postdoctoral researcher whose Ph.D. work forms the foundation for this study will be supported through this project. An Israeli masters-level student and one U.S. minority undergraduate intern will be advised and trained in this project.The project will use an integrated approach to assess different mechanisms that may result in NICP, including riverine sediment input, land-derived particle influx via flash floods, bottom sediment resuspension, and atmospheric dust input. Field investigations will be done in a suite of coastal environments: the northern Red Sea, the Mississippi and Sabine River plumes and Galveston Bay in the northern Gulf of Mexico, each of which receive significant quantities of non-carbonate rich sediments. The investigators will also conduct controlled laboratory experiments to verify and extend field observations. If NICP is shown to be significant, this finding could promote a reexamination of important parts of the carbon cycle and the response of the ocean carbon system to ongoing perturbations.