Development and testing of an online method to measure ambient fine particulate reactive oxygen species (ROS) based on the 2',7'-dichlorofluorescin (DCFH) assay

摘要

An online, semi-continuous instrument to measure fine particle (PM_2.5)reactive oxygen species (ROS) was developed based on the fluorescent probe2'7'-dichlorofluorescin (DCFH). Parameters that influence probe responsewere first characterized to develop an optimal method for use in a fieldinstrument. The online method used a mist chamber scrubber to collect total(gas plus particle) ROS components (ROS_t) alternating with gasphase ROS (ROS_g) by means of an inline filter. Particle phase ROS(ROS_p) was determined by the difference between ROS_tand ROS_g. The instrument was deployed in urban Atlanta, Georgia,USA, and at a rural site during various seasons. Concentrations from theonline instrument generally agreed well with those from an intensive filtermeasurement of ROS_p. Concentrations of the ROS_pmeasurements made with this instrument were lower than reported in otherstudies, often below the instrument's average limit of detection(0.15 nmol H₂O₂ equivalents m?3). Mean ROS_pconcentrations were 0.26 nmol H₂O₂ equivalents m?3 at theAtlanta urban sites compared to 0.14 nmol H₂O₂equivalents m?3 at the rural site.