UAV-based gas monitoring systems for the underpinning of urban, agricultural and industrial emission roadmaps &#8211; a methodological approach
Authors: Leitner Simon , Feichtinger Wendelin , Mayer Stefan , Mayer Florian , Krompetz Dustin , Hood-Nowotny Rebecca , Watzinger Andrea 
Published: March 2020

&lt;p&gt;Currently sampling of the atmosphere for gas emission measurements involves building towers or hiring airplanes - capital-intensive methods. Easy access to unmanned aerial vehicles (UAV) has opened-up new opportunities for remote gas sampling. The project Iso-2-Drone aims to develop and produce a modular UAV-based gas monitoring system for emission measurements to substitute current technologies. A key feature of the UAV-attached gas sampler design was the ready-to-use nature of the system. This meant that the system was designed to mesh with commonly available equipment, using collection vessels which can be easily and immediately measured by common continuous flow - isotope ratio mass spectrometer (CF-IRMS) instrumentation. The target compounds comprise the three major natural greenhouse gases CH&lt;sub&gt;4&lt;/sub&gt;, CO&lt;sub&gt;2&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O to be measured at natural isotopic abundance and ambient levels.&lt;/p&gt;&lt;p&gt;We use 20 mL headspace vials for CH&lt;sub&gt;4&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; sampling. Vials can be conditioned on-sight with our sample preparation prototype using repeatedly evacuating and synthetic air refilling cycles to prevent ambient air contamination. On the UAV-attached sampler atmospheric air is sampled passively by pressure compensation of the vacuum. N&lt;sub&gt;2&lt;/sub&gt;O is sampled actively via adsorption tubes, filled with Molecular Sieve 5&amp;#197; and conditioned in the lab. Both a prototype device and two UAV-attached samplers have been designed, built and are currently tested.&lt;/p&gt;&lt;p&gt;The measurement setup in the lab comprises of two autosamplers, a purge &amp; trap system (VSP 4000, IMT Innovative Maschinentechnik GmbH) and a headspace sampler (CTC CombiPal, Chromtech GmbH) in order to switch from ppb range necessary for CH&lt;sub&gt;4 &lt;/sub&gt;and N&lt;sub&gt;2&lt;/sub&gt;O to a ppm range for CO&lt;sub&gt;2&lt;/sub&gt;. For CO&lt;sub&gt;2 &lt;/sub&gt;measurements the CTC injects 600 &amp;#181;l of sampled air to a Restek Micropacked Column (Shin Carbon ST 100/120, 2m x 1mm ID and 1/16&amp;#8221; OD) within a Thermo Scientific Trace GC Ultra heated up from 40&amp;#176;C to 110&amp;#176;C, maintained for 5 min, before heating up to 180&amp;#176;C by 12&amp;#176;C per minute. Thereby CO&lt;sub&gt;2&lt;/sub&gt; is properly separated from the potentially interfering N&lt;sub&gt;2&lt;/sub&gt;O. For CH&lt;sub&gt;4&lt;/sub&gt; the residual air sample is cryo-focused at -140&amp;#176;C in a HayeSep D filled trap, transferred to the GC and targeted with a Poraplot Q (30m x 0.32mm) held at 35&amp;#176;C. Using the similar GC method and autosampler N&lt;sub&gt;2&lt;/sub&gt;O is desorbed after switching the autosampler to thermal desorption mode. All three analytes pass an oxidation/reduction reactor (1030&amp;#176;C) before they are introduced into the IRMS (Thermo Scientific DeltaV Advantage) via a universal gas interface (Thermo Scientific Conflo IV). The IRMS continuously scans the intensity of the mass-to-charge ratios of mass 44, 45, 46 for CH&lt;sub&gt;4&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; and 28, 29 for N&lt;sub&gt;2&lt;/sub&gt;0 converted to N&lt;sub&gt;2&lt;/sub&gt;. &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N are referenced against calibrated laboratory reference gases.&lt;/p&gt;&lt;p&gt;We are currently tuning the methods and testing the prototypes and will present the lasted results and open questions at the conference.&lt;/p&gt;