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.

Air quality data collection near pollution sources is difficult, particularly when sites are complex, have physical barriers, or are themselves moving. Small Unmanned Aerial Vehicles (UAVs) offer new approaches to air pollution and atmospheric studies. However, there are a number of critical design decisions which need to be made to enable representative data collection, in particular the location of the air sampler or air sensor intake. The aim of this research was to establish the best mounting point for four gas sensors and a Particle Number Concentration (PNC) monitor, onboard a hexacopter, so to develop a UAV system capable of measuring point source emissions. The research included two different tests: (1) evaluate the air flow behavior of a hexacopter, its downwash and upwash effect, by measuring air speed along three axes to determine the location where the sensors should be mounted; (2) evaluate the use of gas sensors for CO2, CO, NO2 and NO, and the PNC monitor (DISCmini) to assess the efficiency and performance of the UAV based system by measuring emissions from a diesel engine. The air speed behavior map produced by test 1 shows the best mounting point for the sensors to be alongside the UAV. This position is less affected by the propeller downwash effect. Test 2 results demonstrated that the UAV propellers cause a dispersion effect shown by the decrease of gas and PN concentration measured in real time. A Linear Regression model was used to estimate how the sensor position, relative to the UAV center, affects pollutant concentration measurements when the propellers are turned on. This research establishes guidelines on how to develop a UAV system to measure point source emissions. Such research should be undertaken before any UAV system is developed for real world data collection.

Frugivorous tephritid fruit flies have lineages with high levels of host generalism. These insects use olfaction to locate fruits, but how they are able to recognize the odors of so many different host species is poorly understood. We used a series of behavioral experiments to investigate the role of fruit ripening volatiles as host cues in the Queensland fruit fly, Bactrocera tryoni (Froggatt), a polyphagous pest in Australia. Odors of mature guava (Psidium guajava) attracted female and male flies more strongly than three other ripening stages and guava pulp. We analyzed volatiles from guava odor and selected eleven compounds, all of which elicited an electrophysiological response in the antenna of female flies. Three of these, ethyl acetate, ethyl butyrate, and ethyl propionate, were released at the highest rates from the most attractive ripening stage. In behavioral trials, these three esters were not attractive individually, whereas a combination was necessary and sufficient in attracting female flies. The three-component blend was as attractive as the entire 11-component blend, which without these key volatiles was not attractive. Moreover, injecting low ranking hosts (squash and cucumber) with the three volatiles increased attraction in ovipositing female flies. These fruit flies are classed as generalists, but like many polyphagous insects they could be regarded as resource specialists, preferring specific plant reproductive stages with predictable odor cues. Exploring olfaction from this perspective could improve our understanding of host choice in polyphagous insects, and the selection of volatiles to be used as attractants in insect pest management.

This paper describes a generic and integrated solar powered remote Unmanned Air Vehicles (UAV) and Wireless Sensor Network (WSN) gas sensing system. The system uses a generic gas sensing system for CH 4 and CO 2 concentrations using metal oxide (MoX) and non-dispersive infrared sensors, and a new solar cell encapsulation method to power the UASs as well as a data management platform to store, analyse and share the information with operators and external users. The system was successfully field tested at ground and low altitudes, collecting, storing and transmitting data in real time to a central node for analysis and 3D mapping. The system can be used in a wide range of outdoor applications, especially in agriculture, bushfires, mining studies, opening the way to a ubiquitous low cost environmental monitoring. A video of the bench and flight test performed can be seen in the following link https://www.youtube.com/watch?v=Bwas7stYIxQ.

A quantitative assessment of the vertical profile of traffic pollution, specifically particle number concentration (PNC), in an open space adjacent to a motorway was possible for the first time, to the knowledge of the authors, using an Unmanned Aerial Vehicle (UAV) system. Until now, traffic pollution has only been measured at ground level while the vertical distribution, is limited to studies conducted from buildings or fixed towers and balloons. This new UAV system demonstrated that the PNC sampled during the period form 10 a.m. to 4 p.m., outside the rush hours with a constant traffic flow, increased from a concentration of 2 × 10 p/cm near the ground up to 10 m, and then sharply decreased attaining a steady value of 4 × 10 p/cm beyond a height of about 40 m. While more comprehensive investigations would be warranted under different conditions, such as topography and vehicle and fuel type, this finding is of great significance, given that it demonstrates the impact of traffic emissions on human exposure, but less so to pollution within the upper part of the boundary layer.