Performance evaluation of the cost-effective and lightweight Alphasense optical particle counter for use onboard unmanned aerial vehicles

Air quality monitoring using airborne platforms is rapidly gaining ground as unmanned aerial vehicles (UAVs) are becoming easier, less expensive, and safer to operate on a routine basis. To facilitate measurements of key atmospheric properties, however, efforts are still required in developing/testing miniaturized instruments for use onboard UAVs. Here, we test two commercially available cost-effective/lightweight optical particle counters (OPCs; Alphasense Model N2) capable of measuring the size distributions of airborne particles having diameters from 380 nm to 17 μm. Tests were made against a reference and recently calibrated OPC (Grimm Model 1.109) using monodisperse polystyrene spheres. All instruments were placed in a chamber in which the temperature and pressure varied in the ranges of –5 to 23°C and 0.7 to 1.0 atm, respectively; conditions typically encountered during UAV flights. Agreement in the particle number concentrations measured by the Alphasense and the Grimm OPCs was within 40%, under all experimental conditions used in this work, when particles having sizes >1 μm were employed during the tests. Deviations higher than 50%, however, were observed when the instruments were tested with 1.0- and 0.8-μm polysterene spheres. The particle sizes reported by both Alphasense OPCs were within ± 5% with respect to the nominal polysterene spheres’ size under all operating pressures and temperatures down to 5°C. At lower temperatures, the sizing accuracy of one of the two Alphasense OPCs degraded significantly. While our findings support that the Alphasense OPCs can be used at low temperature/pressure conditions, they should be carefully tested prior the measurements to ensure good performance.Atmospheric Remote Sensin

Towards understanding the characteristics of new particle formation in the Eastern Mediterranean

To quantify the contribution of new particle formation (NPF) to ultrafine particle number and cloud condensation nuclei (CCN) budgets, one has to understand the mechanisms that govern NPF in different environments and its temporal extent. Here, we study NPF in Cyprus, an Eastern Mediterranean country located at the crossroads of three continents and affected by diverse air masses originating from continental, maritime, and desert-dust source areas. We performed 1-year continuous measurements of aerosol particles down to similar to 1 nm in diameter for the first time in the Eastern Mediterranean and Middle East (EMME) region. These measurements were complemented with trace gas data, meteorological variables, and retroplume analysis. We show that NPF is a very frequent phenomenon at this site and has higher frequencies of occurrence during spring and autumn. NPF events were both of local and regional origin, and the local events occurred frequently during the month with the lowest NPF frequency. Some NPF events exhibited multiple onsets, while others exhibited apparent particle shrinkage in size. Additionally, NPF events were observed during the nighttime and during episodes of high desert-dust loadings. Particle formation rates and growth rates were comparable to those in rological variables and trace gases played a role in explaining the intra-monthly variability of NPF events, but they did not explain why summer months had the least NPF frequency. Similarly, pre-existing aerosol loading did not explain the observed seasonality. The months with the least NPF frequency were associated with higher H2SO4 concentrations but lower NO2 concentrations, which is an indicator of anthropogenic influence. Air masses arriving from the Middle East were not observed during these months, which could suggest that precursor vapors important for nucleation and growth are transported to our site from the Middle East. Further comprehensive measurements of precursor vapors are required to prove this hypothesis.Peer reviewe

Submicron aerosol pollution in Greater Cairo (Egypt): A new type of urban haze?

International audienc