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Assessment of air quality has been traditionally conducted by ground based monitoring, and more recently by manned aircrafts and satellites. However, performing fast, comprehensive data collection near pollution sources is not always feasible due to the complexity of sites, moving sources or physical barriers. Small Unmanned Aerial Vehicles (UAVs) equipped with different sensors have been introduced for in-situ air quality monitoring, as they can offer new approaches and research opportunities in air pollution and emission monitoring, as well as for studying atmospheric trends, such as climate change, while ensuring urban and industrial air safety. The aims of this review were to: (1) compile information on the use of UAVs for air quality studies; and (2) assess their benefits and range of applications. An extensive literature review was conducted using three bibliographic databases (Scopus, Web of Knowledge, Google Scholar) and a total of 60 papers was found. This relatively small number of papers implies that the field is still in its early stages of development. We concluded that, while the potential of UAVs for air quality research has been established, several challenges still need to be addressed, including: the flight endurance, payload capacity, sensor dimensions/accuracy, and sensitivity. However, the challenges are not simply technological, in fact, policy and regulations, which differ between countries, represent the greatest challenge to facilitating the wider use of UAVs in atmospheric research.

Rising pollution levels resulting from vehicular emissions and the depletion of petroleum-based fuels have left mankind in pursuit of alternatives. There are stringent regulations around the world to control the particulate matter (PM) emissions from internal combustion engines. To this end, researchers have been exploring different measures to reduce PM emissions such as using modern combustion techniques, after-treatment systems such as diesel particulate filter (DPF) and gasoline particulate filter (GPF), and alternative fuels. Alternative fuels such as biodiesel (derived from edible, nonedible, and waste resources), alcohol fuels (ethanol, n-butanol, and n-pentanol), and fuel additives have been investigated over the last decade. PM characterization and toxicity analysis is still growing as researchers are developing methodologies to reduce particle emissions using various approaches such as fuel modification and after-treatment devices. To address these aspects, this review paper studies the PM characteristics, health issues, PM physical and chemical properties, and the effect of alternative fuels such as biodiesel, alcohol fuels, and oxygenated additives on PM emissions from diesel engines. In addition, the correlation between physical and chemical properties of alternate fuels and the characteristics of PM emissions is explored.

Thunderstorm asthma (TA) is a significant health concern, recorded in 26 instances globally, primarily linked to ryegrass pollen. Existing research has shown that physical forces such as wind and rain can cause pollen to rupture during thunderstorms, creating micronic, inhalable allergen-rich fragments called sub-pollen particles (SPPs). However, little is known about the role of electrical charges in storm clouds, such as those associated with lightning, in triggering pollen rupture. This study presents the first simulation-based evidence that the static electric fields typical of storm clouds (105-870 kV/m) can fragment pollen into SPPs. The results reveal a clear increase in pollen fragmentation and dispersal when exposed to these charges - especially at higher electric field strengths and higher humidity. Under discharge conditions, such as simulated lightning (arcing), fragmentation intensifies, generating abundant, irregularly shaped ruptured pollen particles, as confirmed by scanning electron microscopy. The results identify both static and discharge electrical processes in storm clouds as drivers of pollen rupture, advancing the mechanistic understanding of TA. In the context of climate change-driven increases in severe storm frequency and intensity, this dual-mechanism insight has important implications for forecasting TA risk and mitigating respiratory health impacts.

The disposal of waste rubber and scrap tyres is a significant issue globally; disposal into stockpiles and landfill poses a serious threat to the environment, in addition to creating ecological problems. Fuel production from tyre waste could form part of the solution to this global issue. Therefore, this paper studies the potential of fuels derived from waste tyres as alternatives to diesel. Production methods and the influence of reactor operating parameters (such as reactor temperature and catalyst type) on oil yield are outlined. These have a major effect on the performance and emission characteristics of diesel engines when using tyre derived fuels. In general, tyre derived fuels increase the brake specific fuel consumption and decrease the brake thermal efficiency. The majority of studies indicate that NOx emissions increase with waste tyre derived fuels; however, a few studies have reported the opposite trend. A similar increasing trend has been observed for CO and CO 2 emissions. Although most studies reported an increase in HC emission owing to lower cetane number and higher density, some studies have reported reduced HC emissions. It has been found that the higher aromatic content in such fuels can lead to increased particulate matter emissions.

The frequency of coral bleaching events increased during the past decade in the Great Barrier Reef (GBR) due to climate change, and rising ocean temperatures. Recent work has demonstrated that enhancing local-scale cloud albedo can reduce the sea surface temperatures (SSTs) in this region. However, little research has been done on variations in the aerosol properties, as well as aerosol–radiation and aerosol–cloud interactions over different regions of the GBR, which is critical for predicting the potential for marine cloud brightening (MCB) climate forcing on a local or regional scale. Here, we examined trends in the aerosol population in terms of their physical and cloud condensation nuclei (CCN) properties during a research cruise in the Central and Northern GBR. Overall higher particle number concentrations, CCN number concentrations, and CCN activation ratios were observed during periods where the air masses passed over the continent prior to reaching the research vessel, despite lower hygroscopicity parameters. We suggest that organics contribute considerably to CCN number concentrations in this region of the GBR, which highlight the important role of additional emissions from inland Queensland. As well as the total aerosol number concentration, precipitation history along the back trajectory affected CCN number concentrations. These results represent a first step towards building a climatological understanding of aerosol and CCN properties over the GBR during summertime, a region and season where no observations have been previously reported.

Reactive oxygen species (ROS) play an important role in atmospheric pollution, and their detection is essential for assessing air quality and health risks. This study developed and validated a standardized methodology for using the BPEAnit probe in a specially designed particle-into-liquid sampler, the Particle Into Nitroxide Quencher (PINQ), to measure reactive oxygen species in atmospheric monitoring applications. The method demonstrated high sensitivity, with a detection limit of 0.03 nmol·m−3, robust linearity (R2 = 0.9999), and negligible system residue, ensuring accurate ROS quantification. Comparative analyses of startup conditions revealed superior baseline stability under cold start conditions despite the longer stabilization time required. The auto-oxidation of the BPEAnit probe, measured at a rate of 3.01 nmol·m−3 per hour, was identified as a critical factor for long-term monitoring, highlighting the necessity of standardized procedures to mitigate the drift effect. The study established the system’s suitability for urban air quality assessments and public health risk evaluations, offering insights into its limitations and operational challenges. Future advancements could focus on enhancing probe stability and expanding the method’s utility in diverse operational environments, thereby broadening its applicability to diverse monitoring scenarios.

The aerosol-driven radiative effects on marine low-level cloud represent a large uncertainty in climate simulations, in particular over the Southern Ocean, which is also an important region for sea spray aerosol production. Observations of sea spray aerosol organic enrichment and the resulting impact on water uptake over the remote Southern Hemisphere are scarce, and therefore the region is under-represented in existing parameterisations. The Surface Ocean Aerosol Production (SOAP) voyage was a 23 d voyage which sampled three phytoplankton blooms in the highly productive water of the Chatham Rise, east of New Zealand. In this study we examined the enrichment of organics to nascent sea spray aerosol and the modifications to sea spray aerosol water uptake using in situ chamber measurements of seawater samples taken during the SOAP voyage. Primary marine organics contributed up to 23 % of the sea spray mass for particles with diameter less than approximately 1 µm and up to 79 % of the particle volume for 50 nm diameter sea spray. The composition of the submicron organic fraction was consistent throughout the voyage and was largely composed of a polysaccharide-like component, characterised by very low alkane-to-hydroxyl-concentration ratios of approximately 0.1–0.2. The enrichment of organics was compared to the output from the chlorophyll-a-based sea spray aerosol parameterisation suggested by Gantt et al. (2011) and the OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) models. OCEANFILMS improved on the representation of the organic fraction predicted using chlorophyll a, in particular when the co-adsorption of polysaccharides was included; however, the model still under-predicted the proportion of polysaccharides by an average of 33 %. Nascent 50 nm diameter sea spray aerosol hygroscopic growth factors measured at 90 % relative humidity averaged 1.93±0.08 and did not decrease with increasing sea spray aerosol organic fractions. The observed hygroscopicity was greater than expected from the assumption of full solubility, particularly during the most productive phytoplankton bloom (B1), during which organic fractions were greater than approximately 0.4. The water uptake behaviour observed in this study is consistent with that observed for other measurements of phytoplankton blooms and can be partially attributed to the presence of sea salt hydrates, which lowers the sea spray aerosol hygroscopicity when the organic enrichment is low. The inclusion of surface tension effects only marginally improved the modelled hygroscopicity, and a significant discrepancy between the observed and modelled hygroscopicity at high organic volume fractions remained. The findings from the SOAP voyage highlight the influence of biologically sourced organics on sea spray aerosol composition; these data improve the capacity to parameterise sea spray aerosol organic enrichment and water uptake.

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 (EFPNs) were calculated in terms of number of particles emitted (no.) per weight of fuel consumed (kgfuel). Fuel consumption was calculated using the simultaneous measurements of plume CO2 concentration. The calculated EFPN was 7.6±1.4×1015no. kgfuel-1 which is in line with those reported in the literature for ship emissions ranging from 0.2 to 6.2×1016 no. kgfuel-1. This UAV system successfully assessed ship emissions to derive EFPN under real world conditions. This is significant as it provides a novel, relatively inexpensive and accessible way to assess ship EFPN at sea.

A local tropical cyclone (TC) in South China Sea was observed making its first complete landfall on an island. Following the arrival of the TC eye, PM2.5 concentration rose from 4 µg/m³ to 44 µg/m³. Mass reconstruction results reveal that sea salt emerged as the primary source. The similar molar ratios of elements before and after landfall confirm that the source of PM2.5 is associated with the local terrigenous sediment. The ratio of Na+/Cl− in the TC eyewall is approximately 5:1 indicating the existence of chlorine depletion. Meanwhile, the concentration of Cl− and molar ratios like Si/Fe inside the TC eyewall show a rapid increase, and reach a peak in the TC eye, indicating that marine particulate matter invades and presents a treasure‐bowl‐like stepwise aggregation. Our findings provide statistical and theoretical foundations for understanding extreme air pollution events, offering direct evidence of sea‐land transport throughout the entire TC. Plain Language Summary Tropical cyclones are among the most destructive weather extremes. We selected a local TC originating in the South China Sea, which made its first landfall on an island rather than the mainland, providing a rare opportunity to research the atmospheric composition of complete landfall and the sea‐land transport. Results show that PM2.5 concentration increased tenfold during the landfall, with sea salt proven to be a dominant contributor. Interestingly, the elements ratio shows a chlorine depletion in the eyewall which may change our understanding of existing models. The center of eyewall seems to be a divide for sea‐land transport, and the inner side of the eyewall and the eye exhibit a treasure‐bowl‐shaped increase in PM. It shows us the complete process of land‐sea transport in the TC center: The updraft on the outside of the eyewall disturbs the seawater and brings a large amount of marine PM. As the updraft on the inside of the eyewall gradually weakens, the marine PM continues to settle and mixes with the terrestrial PM. When the downdraft inside the eye takes over, the deposition of marine PM reaches its peak. Key Points Ground‐based observations documented the entire initial landfall of the tropical cyclone eye The inner sides of the eyewall show a treasure‐bowl‐like feature, concentrating PM components into the cyclone's eye Abnormal Na+/Cl− ratio indicates significant chlorine depletion in the eyewall, causing severe underestimation in models

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.