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Abstract

A sampler for volatile organic compounds (VOCs) was developed for deployment on a copter-technology unmanned aerial vehicle (UAV). The sampler was designed to collect VOCs on up to five commercially available VOC-adsorbent cartridges for subsequent offline analysis by thermal-desorption gas chromatography. The sampler had a mass of 0.90kg and dimensions of 19cm × 20cm × 5cm. Power consumption was <3Wh in a typical 30min 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 400sccm were possible, and a typical flow of 150sccm was used to balance VOC capture efficiency with sample volume. The overall minimum detection limit for the sampling volumes and the analytical method was close to 2ppt 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 10min each at several different altitude-latitude-longitude collection points. The species identified, their concentrations, and their uncertainties are presented and discussed in the context of the sampler design and capabilities. Finally, design challenges and possibilities for next-generation samplers are addressed.