Cavity Ring Down Spectrometer (CRDS)

相对较新的技术空腔衰荡光谱（CRDS）能够快速可靠地测量气体样品中同位素13C-和12C-CO2以及13C- c和12C-CH4的绝对浓度。CRDS优于GC同位素比质谱（GC- irms）等传统方法：该仪器相对较小，坚固耐用，易于维护，并且也可以部署到现场的原位测量活动中。CRDS不仅通过其同位素比率而且通过其绝对数量来检测这些气体，对于本文提出的两个主要研究应用至关重要：(i)提高新型类聚乙烯聚合物的生物降解性，以及（ii）评估导致淡水湖泊中甲烷分布和通量的过程。在一个合作项目中，我们正在优化微生物降解由可再生资源（植物油）合成的新型、完全可回收的长链聚酯材料。环境微生物群落对塑料的完全降解通常是通过二氧化碳的演变来监测的。然而，为了区分复杂环境基质（如土壤、堆肥）中从背景活动演变而来的二氧化碳，选择用13c -碳同位素标记聚合物是一种方法。在康斯坦茨大学，有一个前所未有的机会，可以获得足够数量的13C标记的长链聚酯，用于生物降解实验。CRDS使我们能够有选择地非常精确地跟踪塑料碳在复杂的自然基质中向最终产品13C CO2的级联转化过程。因此，我们可以在迭代循环中微调破坏聚合物结晶度的酯链和侧基的频率，朝着在几年内而不是几十年或几个世纪内结合足够的材料特性和完全生物降解性的新型聚合物的发展。此外，通过前所未有的实地研究，例如在科考船上的实地活动和沿着水柱取样，CRDS使我们能够评估淡水生态系统（如康斯坦茨湖和其他湖泊和水库）中温室气体CO2和CH4的时空分布和释放。这将获得13C/12C-CH4的比率和母体浓度，从而可以区分CH4的产生（厌氧和好氧甲烷生成）、运输（如扩散排放）和转化（如好氧和厌氧CH4氧化）过程。因此，我们将解开分层水柱中溶解的CH4的起源和湖泊氧水层中CH4的过饱和（“甲烷悖论”）。总的来说，CRDS可以帮助我们解决一些长期存在的关于淡水湖泊CH4产生、转化、运输和排放现象的问题，最终改善气候模式。H4

The relatively new technology Cavity Ring Down Spectroscopy (CRDS) enables fast and reliable measurement of absolute concentrations of isotopic 13C- and 12C-CO2, and 13C-C and 12C-CH4, in gas samples. CRDS is superior to conventional methods such as GC isotope-ratio mass spectrometry (GC-IRMS): the instrument is comparatively small, robust and easy to maintain, and it can be deployed also to in situ measurement campaigns in the field. CRDS to detect these gases not only by their isotopic ratio but in their absolute quantities, is essential for two main research applications proposed here: (i) improving the biodegradability of novel polyethylene-like polymers, and (ii) assessing the processes responsible for the distribution and the fluxes of methane in freshwater lakes.In a collaborative project, we are optimizing the microbial degradation of novel, fully recyable, long-chain polyester materials synthesised from renewable resources (plant oil). Complete degradation of plastic by environmental microbial communities is typically monitored via the evolution of CO2. However, to differentiate the CO2 evolved from background activity in complex environmental matrices (e.g. soil, compost), labelling of the polymers with 13C-carbon isotope is the method of choice. At University of Konstanz exists an unprecedented opportunity in that sufficient amounts of 13C labelled long-chain polyesters can be made accessible for biodegradation experiments. CRDS enables us to selectively and very precisely follow the plastic-carbon through the cascade of transformation processes towards the end product 13C CO2 in complex natural matrices. Thereby, we can fine-tune in iterative cycles the frequency of ester-links and side groups breaking up the crystallinity of the polymers, towards a development of novel polymers that combine sufficient material properties and complete biodegradability within few years instead of decades or centuries.Additionally, CRDS enables us to evaluate spatial and temporal distributions and release of the greenhouse gases CO2 and CH4 from freshwater ecosystems such as Lake Constance and other lakes and reservoirs, in unprecedented in-situ studies, e.g., field campaigns on a research ship and when sampling along the water column. This will acquire 13C/12C-CH4 ratios and parent concentrations and thus, allow for distinguishing of CH4 production (anaerobic and aerobic methanogenesis), transport (e.g., diffusive emission) and transformation (e.g., aerobic and anaerobic CH4 oxidation) processes. We thereby will disentangle the origin of the dissolved CH4 in the stratified water column and the oversaturation of CH4 in the oxic water layers of lakes (‘methane paradox’). Overall, CRDS may enable us to resolve several long-standing questions on the CH4 production, transformation, transport and emission phenomena for freshwater lakes to, ultimately, improve climate models.H4