Identification and treatment of false methane values produced by the tunable diode laser absorption spectroscopy technology equipped on unmanned aerial vehicles.

Fugitive or diffuse methane emissions constitute an important source of damage to the environment, much greater even than CO2 both over a time span of 20 years and over a longer time span of 100. It is therefore of preeminent importance to undertake all the efforts necessary to implement new tools, protocols, and methods that contribute to the identification and measurement of these emissions to implement site-specific actions of mitigation, repair, and conscious management of the emitting plants. Among the remote sensing and leak detection technologies currently used, the tunable diode laser absorption spectroscopy (TDLAS) method plays a relevant role. Thanks to the study and implementation of increasingly high-performance sensors to be equipped on drones, this method is strongly promoted in the unmanned aerial vehicle sector. However, as often happens, the operational performance of a measurement method must be associated with measurement errors, which must be foreseen (where possible), and certainly detailed and corrected. The purpose of this article is to describe the procedure for identifying and processing "false-positive" values recorded by the payload during a survey flight for the measurement of methane concentrations in airborne matrix, with a TDLAS sensor. The methodology contained in this article is based on the study of scientific evidence referable to previous in-depth experiences on false positives and largely on the direct experience gained by the project team of the TALSEF laboratory (University of Bari, Italy) during numerous measurement campaigns in landfills, oil and gas sites, and cattle stables.