Acquisition of spectroscopic and mass spectrometric instrumentation for the evaluation of N cycling and provenance

1456430Ostrom对不同物种中氮的同位素组成的研究有助于深入了解生物地球化学过程的动态，最近的结果表明，在北太平洋，长期的氮同位素年表表明生态系统状态发生了显著变化，这引发了以下问题：该信号是否表明人类过度捕捞导致营养下降，改变了海洋食物网的整个营养结构，和/或与气候耦合的环境变化有关的固氮增加。这笔赠款支持购买气体源稳定同位素比质谱仪(SIRMS)、激光光腔衰减式质谱仪(LCOS)、建造压缩机系统的材料，以填充各种N2O浓度和同位素组成的空气罐，以及能够改善氨基酸ä15N值的气相色谱-氮(GC-N)化合物特定同位素分析系统。该设备将通过有针对性地研究一氧化二氮(一种温室气体)中氮的稳定同位素组成以及从水生和海洋生物组织中回收的氨基酸中氮的稳定同位素组成，促进侧重于海洋和水生系统中全球氮循环的调查者研究。所要求的设备将取代密歇根州立大学老化的SIRMS，LCOS将允许对基于激光的同位素分析与传统SIRMS分析的价值和精度进行比较研究，PI将准备一套LCOS测量所需的N同位素标准，并向更广泛的社区提供。

1456430OstromStudies of the isotopic composition of Nitrogen in various species yield insights on the dynamics of biogeochemical processes and recent results suggest that within the North Pacific Ocean, long-term nitrogen isotope chronologies are indicating a marked ecosystem state change raising questions as to whether the signal indicates a trophic decline resultant from overfishing by humans that has shifted the entire trophic structure of the oceanic food web and/or an increase in nitrogen fixation linked to climate-coupled changes in the environment. This grant supports acquisition of a gas source stable isotope ratio mass spectrometer (SIRMS), a laser optical cavity ring down mass spectrometer (LCOS), materials to construct a compressor system for filling air tanks with a range of N2O concentrations and isotopic compositions, and a gas chromatography nitrogen (GC-N) compound specific isotope analysis system capable of improved amino acid ä15N values. The equipment will foster investigator research focused on global nitrogen cycling in the oceans and aquatic systems with targeted studies of the stable isotopic composition of Nitrogen in Nitrous Oxide (N2O), a greenhouse gas and within amino acids recovered from aquatic and marine organism tissues. The requested equipment will replace an aging SIRMS at Michigan State, the LCOS will allow comparative studies of the value and precision of laser-based isotopic analysis versus traditional SIRMS analysis and the PI will prepare and make available to the broader community a suite of N isotopic standards needed for LCOS measurements.