The diurnal characteristics of PM-bound ROS and its influencing factors at urban ambient and roadside environments

Abstract The airborne particulate matter (PM) is known to cause adverse pulmonary and cardiovascular health effects. This study investigated the diurnal characteristics of PM induced PM-bound ROS from real time measurements in typical roadside and urban background sites in Hong Kong, and identified potential influencing factors to its variation in atmosphere. A nitroxide probe (BPEAnit) was employed in the real-time measurement of separate PM and gas phase induced reactive oxygen species (ROS) with a Particle-into-Liquid-Sampler. Measurements were carried in 2 h intervals over a 24 h period, and repeated for 6 days at each site. The total ROS (particle + gas phase) measurements resulted in multiple peaks at 08:00, 16:00 and 20:00 h time periods at background site, compared to non-intermittent decrease/increase trends at roadside. The total ROS generation was noted significantly higher by 50–100% (n = 6 p