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Spatial characterization of fine PM at the urban and neighborhood scale: from distributed monitoring to imaging

Yael Etzion,  Barak FishbainDavid Broday,Tamar Yacobi

The project focuses on optical methodologies for spatial monitoring of ambient fine PM at the urban and neighborhood scales. Three sensing technologies are examined as complimentary solutions. The first is a distributed stationary network of compact optical sensors that provides number concentrations of fine PM (>0.5 µm) every 1 min. The second is an array of mobile optical sensors provides fine PM (>0.3 µm) every 5 s but is restricted for only short campaigns. The third is an automatic and flexible imaging system, based on a regular DSLR camera, that serves for horizontal aerosol RS by means of imaging of the urban scenery (every 5 min). Together, the three layers form a relatively low-cost multi-sensor network. A second phase deployment of the compact optical sensors was carried out between Sep.-Dec. 2014 to measure below the camera line of site, which started at the Technion campus and spanned up to the adjacent Ziv neighborhood (Phase I area). The objective was to examine differences in fine PM between neighboring microenvironments. For this, we applied frequency (wavelet) analysis on the measured PM time series (Mar.- July., 2014, and Sep.-Dec., 2014). We were able to differentiate fine PM events that correspond to local emissions from contributions representing larger scale processes, such as diurnal process and synoptic events. A manuscript discussing this work is under preparation. This approach is now applied for simultaneously measured wind data, in order to better understand the effects of wind at different spatiotemporal scales on fine PM concentrations. We also launched a collaboration with QUT (Brisbane, AU) to examine this approach for urban neighborhoods in Queensland. In addition, DSLR images were taken between May-Dec., 2014, over the same neighborhood area (Technion Campus, Ziv, Ramat Chen) and revealed the need to revise the image processing algorithms as well as the image parameters examined (PBM, entropy, hue, etc.) for estimating PM. An extensive work is currently done to tune parameters of the image processing, and for selecting better image variables. In parallel to the study in Haifa, the imaging procedure has been exercised in July in Brisbane, AU, and the images are currently being analyzed.