Development and testing a low-cost device for airborne PM monitoring in highly anthropized areas: The international maritime hub of Civitavecchia (Rome, Italy)

In this paper we describe our work aimed at designing a system able to measure the particulate matter (PM) concentrations via an optical particle counter (OPC) and simultaneously collect it via standard 2.5 cm filters for laboratory characterization. The Port of Civitavecchia (Italy), one of the most important maritime hubs of the Mediterranean Sea, was selected as a test site for an eight-months monitoring campaign. Comparison between the data provided by our device with those from the referenced and certified monitoring stations from the governmental Regional Agency for the Protection of the Environment (ARPA Lazio) allowed to define clear threshold values (PM10 = 25 μg/m3 and PM2.5 = 10 μg/m3). These threshold values need to be considered when correcting the OPC raw data with respect to the humidity (RH) conditions. The sample material was characterized through optical microscopy and SEM-EDS (scanning electron microscopy coupled with energy-dispersive X-ray fluorescence) and spectroscopy (FTIR, Raman), showing a variegate composition from Al-Fe-oxides to silicates, carbonates, and sulfates, to coal and amorphous carbon together with microplastics and textile fibers. As a final test, we analyzed the PM trends provided by our device during the COVID-19 lockdown, when stringent restrictions in the human activities caused well-known fluctuations in the atmospheric pollution. We again observed an evolution of the PM peaks in excellent agreement with the results yielded by the ARPA Lazio monitoring stations. This result provides a valuable confidence test for our devices highlighting the effectiveness of the presented strategy for airborne particulate-matter monitoring.