Cavity Ring Down Spectrometer (CRDS)

相对较新的技术腔振荡谱(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同位素比质谱仪(GC-IRMS)等传统方法：该仪器相对较小，坚固耐用，易于维护，还可以部署到现场测量活动中。CRDS不仅通过同位素比率而且通过绝对量来检测这些气体，对于这里提出的两个主要研究应用是至关重要的：(I)提高新型类聚乙烯聚合物的生物降解性，以及(Ii)评估影响淡水湖中甲烷分布和通量的过程。在一个合作项目中，我们正在优化从可再生资源(植物油)合成的新型、完全可回收的长链聚酯材料的微生物降解。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释放来监测的。然而，为了区分复杂环境基质(如土壤、堆肥)中的本底活动释放出的二氧化碳，用13C-碳同位素标记聚合物是一种选择的方法。在康斯坦茨大学，有一个前所未有的机会，可以让足够数量的13C标记的长链聚酯用于生物降解实验。CRDS使我们能够选择性和非常精确地跟踪塑料-碳，通过层叠的转化过程，获得复杂自然基质中的最终产品13C二氧化碳。因此，我们可以在迭代周期中微调酯键和侧基破坏聚合物结晶度的频率，从而开发出在几年内而不是几十年或几个世纪内结合足够材料性能和完全生物降解性的新型聚合物。此外，CRDS使我们能够在史无前例的现场研究中评估温室气体CO2和CH4的时空分布和释放，这些研究来自康斯坦茨湖和其他湖泊和水库等淡水生态系统，例如在考察船上的实地活动和沿水柱采样。这将获得13C/12C-CH4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)、传输(例如扩散排放)和转化(例如好氧和厌氧CH4氧化)过程。因此，我们将解开层状水层中溶解的CH4的来源和湖泊氧化水层中CH4的过饱和(甲烷悖论)。总体而言，CRDS可能使我们能够解决淡水湖CH4的产生、转化、运输和排放现象等几个长期存在的问题，最终改善气候模型。

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