A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles

Abstract

A sampler for volatile organic compounds (VOCs) was developed for deployment on a multicopter unmanned aerial vehicle (UAV). The sampler was designed to collect gas- and aerosol-phase VOCs on up to four commercially available VOC-adsorbent cartridges for subsequent offline analysis by thermal-desorption gas chromatography. The sampler had a mass of 0.90 kg and dimensions of 19 cm ×20 cm ×5 cm. Power consumption was < 10 kJ in a typical 30 min flight, representing < 3 % of the total UAV battery capacity. Autonomous sampler operation and data collection in flight were accomplished with a microcontroller. Sampling flows of 100 to 400 sccm were possible, and a typical flow of 150 sccm was used to balance VOC capture efficiency with sample volume. The overall minimum detection limit of the analytical method for a 10 min sample was 3 ppt and the uncertainty was larger than 3 ppt or 20 % for isoprene and monoterpenes. The sampler was mounted to a commercially available UAV and flown in August 2017 over tropical forest in central Amazonia. Samples were collected sequentially for 10 min each at several different altitude–latitude–longitude collection points. The species identified, their concentrations, their uncertainties, and the possible effects of the UAV platform on the results are presented and discussed in the context of the sampler design and capabilities. Finally, design challenges and possibilities for next-generation samplers are addressed.