This research demonstrates the use of an unmanned aerial vehicle (UAV) to characterize the gaseous (CO₂) and particle (10–500 nm) emissions of a ship at sea. The field study was part of the research voyage “The Great Barrier Reef as a significant source of climatically relevant aerosol particles” on board the RV Investigator around the Australian Great Barrier Reef. Measurements of the RV Investigator exhaust plume were carried out while the ship was operating at sea, at a steady engine load of 30 %. The UAV system was flown autonomously using several different programmed paths. These incorporated different altitudes and distances behind the ship in order to investigate the optimal position to capture the ship plume. Five flights were performed, providing a total of 27 horizontal transects perpendicular to the ship exhaust plume. Results show that the most appropriate altitude and distance to effectively capture the plume was 25 m a.s.l. and 20 m downwind. Particle number emission factors (EF_PNs) were calculated in terms of number of particles emitted (no.) per weight of fuel consumed (kg_fuel). Fuel consumption was calculated using the simultaneous measurements of plume CO₂ concentration. The calculated EF_PN was $\mathrm{7.6}\pm \mathrm{1.4}\times {\mathrm{10}}^{\mathrm{15}}$ no. kg${}_{\mathrm{fuel}}^{-\mathrm{1}}$ which is in line with those reported in the literature for ship emissions ranging from 0.2 to 6.2×10¹⁶ no. kg${}_{\mathrm{fuel}}^{-\mathrm{1}}$ . This UAV system successfully assessed ship emissions to derive EF_PN under real world conditions. This is significant as it provides a novel, relatively inexpensive and accessible way to assess ship EF_PN at sea.

To estimate the oxidative potential (OP) of particulate matter (PM), two commonly used cell-free, molecular probes were applied: dithiothreitol (DTT) and dichloro-dihydro-fluorescein diacetate (DCFH-DA), and their performance was compared with 9,10-bis (phenylethynyl) anthracene-nitroxide (BPEAnit). To the best of our knowledge, this is the first study in which the performance of the DTT and DCFH has been compared with the BPEAnit probe. The average concentrations of PM, organic carbon (OC) and elemental carbon (EC) for fine (PM_2.5) and coarse (PM₁₀) particles were determined. The results were 44.8 ± 13.7, 9.8 ± 5.1 and 9.3 ± 4.8 µg·m⁻³ for PM_2.5 and 75.5 ± 25.1, 16.3 ± 8.7 and 11.8 ± 5.3 µg·m⁻³ for PM₁₀, respectively, for PM, OC and EC. The water-soluble organic carbon (WSOC) fraction accounted for 42 ± 14% and 28 ± 9% of organic carbon in PM_2.5 and PM₁₀, respectively. The average volume normalized OP values for the three assays depended on both the sampling periods and the PM fractions. The OP^BPEAnit had its peak at 2 p.m.; in the afternoon, it was three times higher compared to the morning and late afternoon values. The DCFH and BPEAnit results were correlated (r = 0.64), while there was no good agreement between the BPEAnit and the DTT (r = 0.14). The total organic content of PM does not necessarily represent oxidative capacity and it shows varying correlation with the OP. With respect to the two PM fractions studied, the OP was mostly associated with smaller particles.

Reactive oxygen species (ROS) present on or generated by particulate matter (PM) have been implicated in PM-induced health effects. Methodologies to quantify ROS concentrations vary widely, both in detection and collection methods. However, there is currently an increasing emphasis on rapid collection and measurement due to observations of short half-life ROS. To address this problem, this paper details the design and characterization of a novel instrument for the measurement of PM-bound ROS named the Particle Into Nitroxide Quencher (PINQ). This instrument combines the 9,10-bis (phenylethynyl) anthracene-nitroxide (BPEAnit) ROS assay in conjunction with a purpose-built aerosol collection device, the insoluble aerosol collector (IAC). The IAC continuously collects PM regardless of size or chemistry directly into a liquid sample with a collection efficiency of > 0.97 and a cut-off size of < 20 nm. The sampling time resolution of the PINQ is 1 min, with a limit of detection (LOD) of 0.08 nmol m⁻³ in equivalent BPEAnit-Me concentration per volume of air. This high sample time resolution and sensitivity is achieved due to a combination of the highly concentrated IAC liquid sample, minimized liquid sample volume, and the rapid reaction and stability of the BPEAnit probe.