Search

This study investigated the size-segregated carbonaceous components of particulate matter (PM), including ultrafine particles (UFP or PM0.1), across three distinct urban settings in Phnom Penh, Cambodia: an educational site (University of Health Sciences, UHS), an institutional site (Ministry of Environment, MoE), and a residential area near a landfill. A cascade impactor-type sampler equipped with an inertial filter was used to collect size-segregated particles down to UFPs. Carbonaceous species, including organic carbon (OC) and elemental carbon (EC), were analyzed using a thermal/optical carbon analyzer to determine their composition and ratios. The results indicated no significant differences in mass concentration between weekdays and weekends at all sites; however, PM profiles varied across the location. The UHS site displayed higher EC levels in UFP, with concentrations suggesting significant local vehicular emissions, underscored by a lower OC/EC ratio (2.39 ± 1.13) compared to other sites. In contrast, the landfill site exhibited higher OC components in finer particles, suggesting emissions from organic sources such as waste burning and cooking activities, evidenced by higher OC/EC ratios across all particle sizes (e.g., OC/EC ratio in UFP at 3.78 ± 0.98). The MoE site presented a balanced profile with moderate levels of both OC and EC, influenced by its proximity to natural dispersion factors like the Tonle Sap River. Additionally, air mass backward trajectory analysis integrated with hotspot data indicated transboundary influences, particularly from agricultural burning in surrounding provinces, including Vietnam. Therefore, both local and transboundary emissions influenced the PM levels in Phnom Penh city. [ABSTRACT FROM AUTHOR]

A multi-nozzle layered mesh inertial filter, developed by the authors based on inertial filter technology for separating ultrafine particles (UFPs) at a moderate pressure drop, was investigated in an attempt to improve the steepness of the separation efficiency curve by combining an inertial filter and an impactor. In this system, the separation curves overlap each other, while maintaining about a 100 nm difference in cutoff size dp50. Such a combination, which we refer to as a ‘hybrid inertial filter’, was validated for a single nozzle geometry. Using a multi nozzle geometry, it was scaled up to a high volume air sampling flow rate of 400 l min−1 at a pressure drop of  <15 kPa. An air sampling unit designed for a commercial portable high volume air sampler, consisting of a multi-cyclone (dp50  =  1 µm) and a hybrid inertial filer (dp50  =  130 nm), was devised and its performance was compared with that for conventional air samplers. The scaled up version of the hybrid inertial filter using multi-nozzle geometry was confirmed. The features of the hybrid inertial filter included the suppression of the bouncing of particles with sizes  >300 nm, a steeper collection efficiency curve and less pressure drop than those of a previous type of inertial filter. The ambient PM0.13 evaluated for the present unit was found to be in good agreement with values obtained for 2 different types of cascade air samplers. [ABSTRACT FROM AUTHOR]