Simulation and Field Campaign Evaluation of an Optical Particle Counter on a Fixed-Wing UAV

Unmanned aerial vehicles (UAVs) have great potential to be utilised as an airborne platform for measurement of atmospheric particulates and droplets. In particular, the spatio-temporal resolution of UAV measurements could be of use for the characterisation of aerosol, cloud, and radiation (ACR) interactions, which contribute to the largest uncertainty in the radiative forcing of climate change throughout the industrial era (Zelinka et al., 2014). Due to the infancy of the technique however, UAV-instrument combinations must be extensively validated to ensure the data is of high accuracy and reliability. This paper presents an evaluation of a particular UAV-instrument combination: the FMI-Talon fixed-wing UAV and the UCASS open-path optical particle counter. The performance of the UCASS was previously evaluated on a multi-rotor airframe by Girdwood et al. (2020). However, fixed-wing measurements present certain advantages—namely endurance, platform stability, and maximum altitude. Airflow simulations were utilised to define limiting parameters on UAV sampling—that is, an angle of attack limit of 10° and a minimum airspeed of 20 ms−1—which were then applied retroactively to field campaign data as rejection criteria. The field campaign involved an inter-comparison with reference instrumentation mounted on a research station, which the UAV flew past through stratus cloud. The effective diameter measured by the UAV largely agreed within 2 μm. The droplet number concentration agreed within 15 % on all but 5 profiles. It was concluded that UCASS would benefit from a mechanical redesign to avoid calibration drifts, and UAV attitude variations during measurement should be kept to a minimum.

Air Pollution Analysis during the Lockdown on the City of Milan

From February 2020, the progressive adoption of measures to contain coronavirus’s contagion has resulted in a sudden change in anthropogenic activities in Italy, especially in Lombardy. From a scientific point of view, this situation represents a unique laboratory for understanding and predicting the consequences of specific measures aimed at improving air quality. In this work, the lockdown effect on Milan’s (Italy) air quality was analyzed. The PM10 and PM2.5 values were measured by the ARPA Lombardia, and the real-time on-road (ROM) air quality monitoring network indicates the seasonality of these pollutants, which typically record the highest values in the coldest months of the year. The 10-year particulate matter concentrations analysis shows a PM10 reduction of 35% from 2010 to 2020. March 2020 data analysis shows an alternation of days with higher and lower particulate matter concentrations; values decrease in pollutants concentrations of 16%, respective to 2018. The complexity of the phenomena related to the atmospheric particulates formation, transport, and accumulation is highlighted by some circumstances, such as the Sahara dust events. The study showed that the trend of a general pollutant concentration reduction should be attributed to the decrease in emissions (specifically, from the transport sector) from the variation of meteorological and environmental conditions.

Addressing the importance of microplastic particles as vectors for long-range transport of chemical contaminants: perspective in relation to prioritizing research and regulatory actions

Over the last several years there has been increasing concern regarding the environmental fate and potential global transport of plastic debris, particularly in the form of microplastic particles (MPs). The global transport of MPs has also triggered concerns regarding the potential role that its mobility may represent towards influencing the long-range environmental transport (LRET) of particle-bound chemicals, particularly the large number of chemicals known to be added to plastic. This perspective considers the various lines-of-evidence that might be used towards understanding the LRET of persistent organic pollutants (POPs). For instance, it has been proposed that the LRET of POPs is facilitated by global fractionation processes that facilitate the mobility of chemicals from source regions towards remote locations, such as the polar regions, where they have the potential to accumulate. These processes are influenced by the physicochemical properties of POPs and can result in various transport mechanisms influencing environmental fate and transport. Here I suggest that there are similarities that can be drawn, whereby knowledge of how differences in the physicochemical properties of MPs relative to different emission scenarios, can influence the relative importance of sequestration processes that may result in global fractionation of MPs. Several challenges are identified throughout the perspective, with an urgent need towards the development and application of standard sampling and analytical methods being identified as critical for enabling datasets to be reliably compared for use in better understanding potential source-receptor relationships, as well as advancing the characterization and quantification of various environmental fate processes. In many instances, it is suggested that advances in our understanding can be facilitated based on knowledge obtained in other areas of research, such as in relation to studies developing tools to evaluate the mobility of particulate organic matter in aqueous environments or from studies investigating the fate and mobility of atmospheric particulates. Recognizing that not all MPs are equal, with respect to environmental fate and toxicological effects, knowledge regarding which types of MPs are likely to be subject to LRET can only strengthen our ability to evaluate their role as vectors of transport for plastic associated chemicals and the associated risks that their LRET may represent. Nevertheless, several outstanding issues remain that would benefit from constructive discussions between all stakeholders. It is anticipated that this perspective can play a role in initiating those discussions.

Elemental and isotopic compositions in blank filters collecting atmospheric particulates

Background The atmospheric particulates can be harmful to human health due to toxic substances sorbed onto particulates. Although the atmospheric particulates have been collected using different types of filters, few studies have reported background contents of major and trace element, and isotopic compositions in the blank filters used for collecting the particulates yet. Here, we first report background contents of major and trace elements, and isotopic compositions (Zn and Pb isotopes) in the blank filters. Then, we evaluate the best type of filter for elemental and isotope analyses in the particulates. Findings The contents of major elements are the lowest in the PTFE filter and become higher in the order of the Nylon, NC, and GF filters, indicating that either PTFE and/or Nylon filters are the most suitable for major element analysis in the atmospheric particulates. Likewise, the contents of trace elements are the lowest in the PTFE filter and become much higher in the order of the Nylon, NC, and GF filters, indicating that PTFE filter is the most suitable for trace element analysis in the atmospheric particulates. Otherwise, background elemental contents result in overestimating their concentrations in the atmospheric particulates. All δ66ZnJMC-Lyon values in two GF filters are within those from samples of the Chinese deserts and of the Chinese Loess Plateau. Likewise, their 206Pb/204Pb ratios are similar with those of samples from Xi’an and Beijing, indicating that the GF filter is not suitable for Zn and Pb isotope study in the atmospheric particulates. Conclusions This study suggests that the PTFE filter is the most suitable for elemental and isotope study in the atmospheric particulates and that the GF filter cannot be used for source identification in the atmospheric particulates using Zn and Pb isotopes.

Polarization Measurements and Evaluation Based on Multidimensional Polarization Indices Applied in Analyzing Atmospheric Particulates

Online identification and characterization of suspended aerosols can provide a scientific basis for understanding aerosol transformations, quantitatively evaluating the impacts on air quality, public health, and the source apportionment of different atmospheric particulate matters. In this study, we confirm the validity of our developed high-throughput multi-angle polarized scattering vector detection of aerosols and multidimensional polarization scattering index systems. By observation of the mean values, variance, and Wilk’s Lambda of multidimensional polarization indices for different aerosol types, the polarization index shows unique characterization abilities for aerosol properties, and the optimal combination of polarization indices can always be found for a specific aerosol category with a high resolution and discrimination. Clearly, the multidimensional polarization indices of individual aerosols are more suitable for online and real-time aerosol identification and even help to explain the in situ microphysical characteristics of aerosols or evaluate the dynamic evolution of aerosols.

THE INFLUENCING FACTORS OF SO42- AND NO3- IN PM10 IN JINHUA, CHINA

Sulfate (SO42-) and nitrate (NO3-) are the main secondary inorganic components in atmospheric particulates. It is of great significance to understand the formation and evolution of air pollution in the process of air pollution. In this study, samples of PM10 were collected in Jinhua City in eastern China from December 2019 to January 2020 and from June 2020 to August 2020, and also analyzed the influence of different meteorological conditions and gaseous pollutants on the formation of SO42- and NO3- in PM10. The results show that high relative humidity has a significant effect on the increase of sulfur oxidation rate (SOR) in winter, indicating that the winter liquid phase reaction is more conducive to the formation of SO42-. SOR and nitrogen oxidation rate (NOR) decrease with increasing temperature in winter, and increase with increasing temperature in summer. The light intensity has an important promoting effect on both SOR and NOR, indicating that the photochemical reaction is beneficial to the formation of SO42- and NO3-. Both the gaseous precursors SO2 and NO2 have significant promoting effects on the formation of SO42- and NO3- in winter, and the promoting effect of O3 on NOR is higher than that on SOR, indicating that atmospheric oxidation capacity has a greater effect on the formation of NO3-, and the effect of CO on SOR is higher than that on NOR, and there is a negative correlation with SOR.