Development of automated semi-online measurement system to evaluate chemical toxicity of fine particulate matter

Abstract

Atmospheric aerosol particles have long been associated with hazardous effects on human health. For the evaluation of toxicity, however, filter extracts analysis requires a series of manual procedures which is highly time-consuming that can underestimate the amount of unstable and short-lived species in the atmosphere. Therefore, in this study, an automated semi-continuous measurement system was developed for the time-resolved determination of ambient ROS based on the fluorescent probe, dichlorofluorescein assay. The optimization of parameters that can influence response of the system performance was preliminarily characterized. The system included particle into liquid sampler (PILS) as a continuous collector of ambient PM2.5 into liquid phase. An automated syringe pump was introduced for unattended operation by executing the sequence of command regarding the assay protocol. Then, ROS was detected by fluorescent spectrometer. The designated system was assessed via field measurement in the spring, from April 18 to 28 and May 2 to 8, 2019 for 17 days on 3rd floor of Samsung building in Gwangju Science and Technology Institute (35.23 ° N, 126.84 ° E). The measured ROS was also compared with PM2.5 concentration using optical particle counter (OPC) alongside of the ROS monitoring system and ozone concentration. The practical analysis shows that the ROS monitoring system reported temporal and variable ROS amount in the atmosphere, while traditional offline ROS analysis measured about 6 times lower value than semi-online result. The average concentration of the total measurement period was 0.53±0.050 and 0.087 ± 0.002 nmol H2O2 equivalents m-3, respectively. Diurnal variation of ROS was observed with lowest concentration at 4-5 am and the highest concentration at 5-6 am, which highly correlated with hourly variation of ozone during entire sampling period. This is somehow consistency with other previous studies demonstrating that photochemical reaction is important sources of daytime ROS. However, identification of ROS needs further investigation combining with other online measurement for chemical species or physical property of fine particles. The results highlighted that the importance of a time-resolved system applied to the further field studies on toxicological characterization of PM2.5. Furthermore, an applicable designation of this system to couple with other different assays can provide complementary and comprehensive toxicological elucidation of ambient fine particles.