A UAV-based sampling system to analyse greenhouse gases and volatile organic carbons encompassing compound specific stable isotope analysis

Abstract. The study herein reports on the development of two sampling devices and the subsequent analytical setup for the sampling and analysis of atmospheric trace gases. Both samplers can be mounted to an unmanned aerial vehicle (UAV), the targeted compounds were greenhouse gases (e.g. CO2, CH4) and volatile organic compounds (VOC, i.e. chlorinated ethenes), for all compounds mole fraction and the stable carbon isotope ratio were measured. In addition to compound calibration in the laboratory, the functionality of the samplers and the UAV-based sampling was tested in the field. Atmospheric air was either flushed through sorbent tubes for VOC sampling or collect and sampled in glass vials for greenhouse gas analysis. The measurement setup for the sorbent tubes achieved analyte mass recovery rates of 63 %–100 % (more favourable for lower chlorinated VOCs), when prepared from gaseous or liquid calibration standards, and reached a precision better than 0.7 ‰ for δ13C in the molar ratio range of 0.35–4.45 nmol. The precision of triplicate CO2 measurements from whole air sample replicates was < 7.3 mmol mol-1 and < 0.3 ‰ and < 0.03 µmol mol-1 and < 0.24 ‰ for CH4 working gas standard replicates. The UAV-equipped samplers were tested over two field sampling campaigns designed to (1) compare UAV-collected and manually collected samples taken up a vertical profile at a forest site and (2) identify potential emissions of CO2, CH4 or VOC from a former domestic waste dump. The results emphasized the functionality of the sampling and measurement setup described, demonstrating that it a viable tool for monitoring atmospheric trace gas inventories and identifying emission sources.