Stable Isotope Analysis of Greenhouse Gases Requires Analyte Preconcentration

Abstract

Nitrous oxide (N₂O) is an important trace gas contributing to global warming and depletion of ozone in the stratosphere. Its increasing abundance is caused mainly by anthropogenic sources, such as application of fertilizers in agriculture or emissions from industry. To understand the N₂O global budget, its sources and sinks need to be well-described and quantified. In this project, a new method for N₂O source appointment was developed that can help with this task. The method is based on analysis of the eight most abundant isotopic molecules of N₂O, using quantum cascade laser absorption spectroscopy (QCLAS). The applicability of the method towards the N₂O biogeochemical cycle was demonstrated on a prominent N₂O source (bacterial denitrification) and the most important N₂O sink (UV photolysis) on samples prepared in laboratory experiments. An extension of the QCLAS method to natural samples can be achieved by hyphenation with a preconcentration technique that increases concentration of the analyte and standardizes the sample matrix. This article provides an overview of currently applied preconcentration techniques in the field of greenhouse-gas analysis and a description of the preconcentration device TREX that will be employed in future projects with the developed QCLAS method.