Comment on acp-2023-40

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> The increase of volatile organic compounds (VOCs) emissions released into the atmosphere is one of the main threats to human health and climate. VOCs can adversely affect human life through their contribution to air pollution directly and indirectly by reacting via several mechanisms in the air to form secondary organic aerosols. In this study, aerial drone equipped with miniaturized air sampling systems including up to four solid-phase microextraction (SPME) Arrows and four in-tube extraction (ITEX) samplers for the collection of VOCs, along with portable devices for the real-time measurement of black carbon (BC) and total particle numbers at high altitudes was exploited. In total, 135 air samples were collected under optimal sampling conditions in October 2021 at the boreal forest SMEAR II Station, Finland. A total of 48 different VOCs, including nitrogen-containing compounds, alcohols, aldehydes, ketones, organic acids, and hydrocarbons, were detected at different altitudes from 50 to 400 m above ground level with the concentrations up to 6898 ng m^-3 in gas phase and 8613 ng m^-3 in particle phase. Clear differences in VOCs distribution were seen in samples collected from different altitudes, depending on the VOC sources. It was also possible to collect aerosol particles by the filter accessory attached on the ITEX sampling system, and five dicarboxylic acids were quantified with the concentrations of 0.43 to 10.9 &micro;g m^-3. The BC and total particle number measurements provided similar diurnal patterns, indicating their correlation. For spatial distribution, surprisingly the BC concentrations were increased at higher altitudes being 2278 ng m^-3 at 100 m and 3909 ng m^-3 at 400 m. The measurements onboard the drone provided insights into horizontal and vertical variability in BC and aerosol number concentrations above the boreal forest.