MRI: Acquisition of a field-deployable mass spectrometer for biogeochemical research and education.

该合同将有助于购买质子转移反应质谱仪(PTR-MS)，以研究与水环境中挥发性硫、氮和碳化合物的生物地球化学循环有关的各种问题。质谱仪已成为实验室研究中不可估量的工具，拥有质谱学核心设施的大量研究机构就是明证。然而，在野外常规使用的质谱计要少得多，特别是在海洋考察中。PTR-MS系统将提供无与伦比的能力，同时测量与科考船上和偏远野战营地中的二氧化碳、甲烷、一氧化二氮和二甲基硫化物(DMS)等一些生态和气候重要化合物的浓度和通量有关的参数。该仪器将为本科生和研究生研究提供一种新颖和最先进的研究工具。正在进行的研究指出，涉及浮游植物、DMS和云形成的气候反馈机制知之甚少，这反过来又阻碍了对它们进行成功建模的努力。需要改进海洋DMS循环中的许多功能关系，以改进未来的模型，包括开发特定于分类单元的关系。同样，目前的模型无法成功和一致地再现周期的某些特征，例如“夏季DMS悖论”，这表明一些模型可能没有纳入或准确描述关键过程。海洋前体二甲基磺酸丙酸酯与DMS的裂解或与其他S-化合物的去甲基化的相对比例也被认为是DMS生产的重要控制因素，但控制这些比例的因素尚不清楚。同时，全球气候变化预计将在世界范围内引起一系列物理化学反应--S海洋，这将在细胞水平(生理)和群落水平(生态)对海洋浮游植物群落产生深刻影响。这些影响可能是通过改变营养循环，如铁或氮，或改变控制浮游植物生长的非生物因素，如温度和光线。根据所涉及的分类群，浮游植物群落的反应将对全球生物地球化学循环产生积极和消极的影响，包括碳、氮和硫的循环，以及涉及这些元素的反馈机制。PTR-MS系统将用于解决硫、氮和碳的生物地球化学循环中的一些关键问题，包括特定物种的细胞内DMSP浓度和生物合成速率、浮游植物代谢组学、维生素B12在DMSP产生中的作用和海洋DMS水平的调节、海水氨浓度和海洋DMS和氨排放之间的耦合，以及南极湖泊和冰下环境中的生物地球化学循环。在这些调查期间从PTR-MS系统获得的结果将促进对水生生物地球化学过程的了解，并提供关于一些生物地球化学重要化合物的形成(或降解)速率以及关键生物地球化学途径在细胞和生态系统一级的相对重要性的关键信息。这些数据将有助于完善全球生物地球化学和气候模型。

This award will facilitate the purchase of a Proton Transfer Reaction Mass Spectrometer (PTR-MS) to study a variety of questions relating to the biogeochemical cycling of volatile sulfur, nitrogen and carbon compounds in aquatic environments. Mass spectrometers have become an invaluable tool in the laboratory research, as evidenced by the large number of research institutions with mass spectrometry core facilities. Yet, considerably fewer mass spectrometers are routinely used in the field, particularly on oceanographic expeditions. The PTR-MS system will provide an unparalleled ability to simultaneously measure parameters relating to the concentrations and fluxes of a number of ecologically and climatically important compounds such as carbon dioxide, methane, nitrous oxide and dimethylsulfide (DMS) onboard research ships and in remote field camps. The instrument will provide a novel and state-of-the-art research tool for undergraduate and graduate research.Ongoing studies point out that climate feedback mechanisms involving phytoplankton, DMS and cloud formation are poorly understand, which in turn hinders efforts to successfully model them. Refinement of many of the functional relationships in the oceanic DMS cycle is required to improve future models, including developing taxon-specific relationships. Similarly, the inability of current models to successfully and consistently reproduce some features of the cycle, such as the "summer DMS paradox", suggests that key processes may not be incorporated or accurately depicted in some models. The relative proportions of the cleavage of the oceanic precursor dimethylsulfoniopropionate (DMSP) to DMS or demethylation to other S-compounds are also thought to be an important control on DMS production, but the factors controlling these proportions remain unclear. Concurrently, changing global climate is expected to cause an array of physico-chemical responses in the world?s oceans that will have profound impact on marine phytoplankton communities both at a cellular level (physiologically) and at a community level (ecologically). The impacts could occur through changes in nutrient cycling, such as iron or nitrogen, or changes in abiotic factors that control phytoplankton growth, such as temperature and light. Depending on the taxa involved, the responses of the phytoplankton communities will impact both positively and negatively global biogeochemical cycles, including those of carbon, nitrogen and sulfur, and feedback mechanisms involving those elements. The PTR-MS system will be used to address a number of critical questions in the biogeochemical cycling of sulfur, nitrogen and carbon, including species-specific intracellular DMSP concentrations and biosynthesis rates, phytoplankton metabolomics, the role of vitamin B12 in the production of DMSP and the modulation of oceanic DMS levels, seawater ammonia concentrations and the coupling between oceanic DMS and ammonia emissions, and biogeochemical cycling in Antarctic lakes and sub-glacial environments. The results obtained from the PTR-MS system during these investigations will advance understanding of aquatic biogeochemical processes and provide critical information on the rates of formation (or degradation) of a number of biogeochemically important compounds and the relative importance of critical biogeochemical pathways, at both cellular and ecosystem levels. This data will help refine global biogeochemical and climate models.