Drone-Based VOC Sampling System for Atmospheric Insights in the Amazon

Abstract

Produced mainly through natural emission from vegetation (~1015 grams a year), volatile organic compounds (VOCs) in influence climate through their involvement in photochemistry, such as the production of ozone in the presence of NOx and light. Decades of stationary tower-based studies (~10s of meters) and aircraft flights (~10s of kilometers) have revealed extreme heterogeneity in VOC concentrations in time and space. However, the actual variation in forest cover occurs at ~1 km and less, a scale that represents a missing link in our present-day understanding of VOCs in atmospheric chemistry. This project involves the engineering design, production, and validation of a drone-deployed VOC sampling instrument. The instrument design includes a custom pump and selector valve system for sequentially collecting samples through multiple sorbent-packed thermal desorption tubes and features a lightweight enclosure that can be integrated directly to the chassis of existing drone platforms. Component validation tests revealed high ow rate consistency and no significant gas leakage, both important requirements for post-flight gas chromatography analysis. An onboard microcontroller successfully controlled sampling routines and ow system data acquisition and storage to an onboard memory card. Furthermore, flight tests with the sampler instrument integrated to a DJI Matrice 600 drone demonstrated unimpaired flight dynamics as well as full ow system function under a series of flight maneuvers in high winds. Once deployed as part of a multi-drone fleet from a mobile boat platform, this sampling instrument will help elucidate uncertainties surrounding the magnitudes, variations, and processes controlling VOC emission and uptake at previously unexplored spatial and temporal scales.