<p class="first" id="P2">Characterizing highly dynamic, transient, and vertically
lofted emissions from open
area sources poses unique measurement challenges. This study developed and applied
a multipollutant sensor and time-integrated sampler system for use on mobile applications
such as vehicles, tethered balloons (aerostats) and unmanned aerial vehicles (UAVs)
to determine emission factors. The system is particularly applicable to open area
sources, such as forest fires, due to its light weight (3.5 kg), compact size (6.75
L), and internal power supply. The sensor system, termed “Kolibri”, consists of sensors
measuring CO
<sub>2</sub> and CO, and samplers for particulate matter (PM) and volatile organic
compounds (VOCs).
The Kolibri is controlled by a microcontroller which can record and transfer data
in real time through a radio module. Selection of the sensors was based on laboratory
testing for accuracy, response delay and recovery, cross-sensitivity, and precision.
The Kolibri was compared against rack-mounted continuous emissions monitoring system
(CEMs) and another mobile sampling instrument (the “Flyer”) that has been used in
over ten open area pollutant sampling events. Our results showed that the time series
of CO, CO
<sub>2</sub>, and PM
<sub>2.5</sub> concentrations measured by the Kolibri agreed well with those from
the CEMs and the
Flyer, with a laboratory- tested percentage error of 4.9%, 3%, and 5.8%, respectively.
The VOC emission factors obtained using the Kolibri were consistent with existing
literature values that relate concentration to combustion efficiency. The potential
effect of rotor downwash on particle sampling was investigated in an indoor laboratory
and the preliminary results suggested that its influence is minimal. Field application
of the Kolibri sampling open detonation plumes indicated that the CO and CO
<sub>2</sub> sensors responded dynamically and their concentrations co-varied with
emission transients.
The Kolibri system can be applied to various challenging open area scenarios such
as fires, lagoons, flares, and landfills.
</p>