The catalytic performance of methane oxidation catalysts, i.e., LaFe 0.95 Pd 0.05 O 3 , 2 wt % Pd/LaFeO 3 , and 2 wt % Pd/Al 2 O 3 , has been compared at 500 °C under periodic red-ox conditions. The state of palladium has been followed under operando conditions using XANES and QEXAFS at the Pd K-edge combined with mass spectrometry (MS) for product detection. Online MS data reveal that in correspondence to every change of feed composition (O 2 pulses) CO 2 production is enhanced over LaFe 0.95 Pd 0.05 O 3 that is associated with a drop in methane concentration. This is not the case for the samples where PdO nanoparticles are deposited on the support material (Pd/LaFeO 3 and Pd/Al 2 O 3 ). The time-resolved QEXAFS spectra have been treated with a modulation excitation spectroscopy approach. Phase sensitive detection (PSD) enabled to highlight the subtle changes in the whiteline region. Continuous reduction-oxidation of Pd occurs in all samples at every change of feed composition. However, by this process Pd in LaFe 0.95 Pd 0.05 O 3 reversibly emerges on the LaFeO 3 surface under reducing conditions and enters the LaFeO 3 structure under oxidizing conditions. On the contrary, Pd oscillates between the reduced and partially oxidized state in Pd/Al 2 O 3 and Pd/LaFeO 3 in which welldefined Pd nanoparticles are already available. This structural difference is responsible for the activity enhancement in correspondence of each switch and is attributed to the self-regenerative property of perovskitetype oxides.

Abstract. A compact and lightweight mid-infrared laser absorption spectrometer has been developed as a mobile sensing platform for high-precision atmospheric methane measurements aboard small unmanned aerial vehicles (UAVs). The instrument leverages two recent innovations: a novel segmented circular multipass cell (SC-MPC) design and a power-efficient, low-noise, intermittent continuous-wave (icw) laser driving approach. A system-on-chip hardware control and data acquisition system enables energy-efficient and fully autonomous operation. The integrated spectrometer weighs 2.1 kg (including battery) and consumes 18 W of electrical power, making it ideally suited for airborne monitoring applications. Under stable laboratory conditions, the device achieves a precision (1σ) of 1.1 ppb within 1 s and 0.1 ppb CH4 at 100 s averaging time. Detailed investigations were performed to identify and quantify the effects of various environmental factors, such as sudden changes in pressure, temperature, and mechanical vibrations, which commonly influence UAV-mounted sensors. The instrument was also deployed in two feasibility field studies: an artificial methane release experiment and a study on vertical profiles in the planetary boundary layer. In both cases, the spectrometer demonstrated its airborne capability of capturing subtle and/or sudden changes in atmospheric CH4 mole fractions and providing real-time data at 1 s time resolution.

Abstract. The record of past greenhouse gas composition from ice cores is crucial for our understanding of global climate change. Future ice core projects will aim to extend both the temporal coverage (extending the timescale to 1.5 Myr) and the temporal resolution of existing records. This implies a strongly limited sample availability, increasing demands on analytical accuracy and precision, and the need to reuse air samples extracted from ice cores for multiple gas analyses. To meet these requirements, we designed and developed a new analytical system that combines direct absorption laser spectroscopy in the mid-infrared (mid-IR) with a quantitative sublimation extraction method. Here, we focus on a high-precision dual-laser spectrometer for the simultaneous measurement of CH4, N2O, and CO2 concentrations, as well as δ13C(CO2). Flow-through experiments at 5 mbar gas pressure demonstrate an analytical precision (1 σ) of 0.006 ppm for CO2, 0.02 ‰ for δ13C(CO2), 0.4 ppb for CH4, and 0.1 ppb for N2O, obtained after an integration time of 100 s. Sample–standard repeatabilities (1 σ) of discrete samples of 1 mL STP (Standard Temperature and Pressure) amount to 0.03 ppm, 2.2 ppb, 1 ppb, and 0.04 ‰ for CO2, CH4, N2O, and δ13C(CO2), respectively. The key elements to achieve this performance are a custom-developed multipass absorption cell, custom-made high-performance data acquisition and laser driving electronics, and a robust calibration approach involving multiple reference gases. The assessment of the spectrometer capabilities in repeated measurement cycles of discrete air samples – mimicking the procedure for external samples such as air samples from ice cores – was found to fully meet our performance criteria for future ice core analysis. Finally, this non-consumptive method allows the reuse of the precious gas samples for further analysis, which creates new opportunities in ice core science.

Abstract. A compact and lightweight mid-IR laser absorption spectrometer has been developed as mobile sensing platform for high-precision atmospheric methane measurements aboard small, unmanned aerial vehicles (UAVs). The instrument leverages on two recent innovations: a novel segmented circular multipass cell (SC-MPC) design and a power efficient, low-noise, intermittent continuous-wave (icw) laser driving approach. A system-on-chip hardware control and data acquisition system enables energy-efficient and fully autonomous operation. The integrated spectrometer weighs 2.1 kg (including battery) and consumes 18 W of electrical power, making it ideally suited for airborne monitoring applications. Under stable laboratory conditions, the device achieves a precision (1σ) of 1.1 ppb within 1 s and 0.1 ppb CH4 at 100 s averaging time. Detailed investigations were performed to identify and quantify the effects of various environmental factors, such as sudden changes in pressure, temperature, and mechanical vibrations, which commonly influence UAV mounted sensors. The instrument was also deployed in two feasibility field-studies: an artificial methane release experiment as well as a study on vertical profiles in the planetary boundary layer. In both cases, the spectrometer demonstrated its airborne capability of capturing subtle and/or sudden changes in atmospheric CH4 mole fractions and providing real-time data at 1 s time resolution.