A Drone-Based Bioaerosol Sampling System to Monitor Ice Nucleation Particles in the Lower Atmosphere

Abstract

Terrestrial ecosystems can influence atmospheric processes by contributing a huge variety of biological aerosols (bioaerosols) to the environment. Several types of biological particles, such as pollen grains, fungal spores, and bacteria cells, trigger freezing processes in super-cooled cloud droplets, and as such can contribute to the hydrological cycle. Even though biogenic particles are known as the most active form of ice nucleation particles (INPs), the transport to high tropospheric altitudes, as well as the occurrence in clouds, remains understudied. Thus, transport processes from the land surface into the atmosphere need to be investigated to estimate weather phenomena and climate trends. To help fill this knowledge gap, we developed a drone-based aerosol particles sampling impinger/impactor (DAPSI) system for field studies to investigate sources and near surface transport of biological INPs. DAPSI was designed to attach to commercial rotary-wing drones to collect biological particles within about 100 m of the Earth’s surface. DAPSI provides information on particulate matter concentrations (PM10 & PM2.5), temperature, relative humidity, and air pressure at about 0.5 Hz, by controlling electrical sensors with an onboard computer (Raspberry Pi 3). Two remote-operated sampling systems (impinging and impacting) were integrated into DAPSI. Laboratory tests of the impinging system showed a 96% sampling efficiency for standardized aerosol particles (2 µm polystyrene latex spheres) and 84% for an aerosol containing biological INPs (Betula pendula). A series of sampling missions (12 flights) were performed using two Phantom 4 quadcopters with DAPSI onboard at a remote sampling site near Gosau, Austria. Fluorescence microscopy of impactor foils showed a significant number of auto-fluorescent particles < 0.5 µm at an excitation of 465–495 nm and an emission of 515–555 nm. A slight increase in ice nucleation activity (onset temperature between −27 °C and −31 °C) of sampled aerosol was measured by applying freezing experiments with a microscopic cooling technique. There are a number of unique opportunities for DAPSI to be used to study the transport of bioaerosols, particularly for investigations of biological INP emissions from natural sources such as birch or pine forests.

Airborne Fungal Spore Review, New Advances and Automatisation

“…Although the contribution of bioaerosols to IN and CCN has received increased attention in recent times, there remains a great deal of controversy surrounding the total contribution of PBAPs to cloud formation. Compared to the more prominent atmospheric aerosols, such as sulphates, organics, sea-salt, dust, and smoke particles, the area remains notably understudied [98].…”

Surfaces of silver birch (<i>Betula pendula</i>) are sources of biological ice nuclei: in vivo and in situ investigations

“…Heavy rain events and thunderstorms have been associated with high INP concentrations (Bigg and Miles, 1964;Isono and Tanaka, 1966). More recently, studies highlight that rainfall triggers the release of PBAPs into the atmosphere (Huffman et al, 2013;Rathnayake et al, 2017;Prenni et al, 2013;Hara et al, 2016;Tobo et al, 2013).…”

Ice Nucleation Activity of Alpine Bioaerosol Emitted in Vicinity of a Birch Forest

“…Observed IN concentrations were examined in the context of meteorological parameters including temperature, relative humidity, and rainfall. This paradigmatic work extends the aerosol-sampling technology highlighted by Bieber, et al [39] by (1) measuring ice nucleation activity (INA) at lower limit of quantification with the high-throughput Twin-plate Ice Nucleation Assay (TINA), (2) focusing on IN concentrations on the ground and above the tree canopy of birches and, (3) extending fluorescence and electron microscopy from detection to assignment of bioparticles. The specific objectives of our work were to: (i) investigate the ice-nucleation activity of aerosols sampled at different altitudes in an alpine environment near major sources of vegetation, (ii) examine potential associations of IN concentrations in alpine environments with meteorological parameters, and (iii) characterize biological aerosol particles according to their morphology using fluorescence and scanning electron microscopy (SEM).…”