Continuous and near real-time measurements of gaseous elemental mercury (GEM) from an Unmanned Aerial Vehicle: A new approach to investigate the 3D distribution of GEM in the lower atmosphere

We present the first real attempt to directly and continuously measure GEM through a Lumex RA-915 M,
designed for real-time detection of mercury vapor, mounted on an UAV (Unmanned Aerial Vehicle, namely a
heavy-lift octocopter), inside and outside the former Hg-mining area of Abbadia San Salvatore (Mt. Amiata,
Italy), known as a GEM source. We tested the effectiveness of the UAV-Lumex combination at different heights in
selected sites pertaining to both mining facilities and surrounding urban zones, shedding light on the GEM spatial
distribution and concentration variability. The Lumex great sensitivity and the octocopter optimal versatility and
maneuverability, both horizontally and vertically, allowed to depict the GEM distribution in the atmosphere up
to 60 m above the ground. The acquisition system was further optimized by: i) synchronizing Lumex and UAV
GPS data by means of a stand-alone GPS that was previously synchronized with Lumex; ii) using a vertical
sampling tube (1.20 m high) connected to the Lumex inlet to overcome the rotors strong airflows and turbulence
that would have affected GEM measurements; iii) supplying the octocopter with batteries for power supply to