An automated online instrument to quantify aerosol-bound reactive oxygen species (ROS) for ambient measurement and health-relevant aerosol studies

摘要

The adverse health effects associated with ambient aerosol particles have been well documented, but it is still unclear which aerosol properties are most important for their negative health impact. Some studies suggest the oxidative effects of particle-bound reactive oxygen species (ROS) are potential major contributors to the toxicity of particles. Traditional ROS measurement techniques are labour-intensive, give poor temporal resolution and generally have significant delays between aerosol sampling and ROS analysis. However, many oxidising particle components are reactive and thus potentially short-lived. Thus, a technique to quantify particle-bound ROS online would be beneficial to quantify also the short-lived ROS components. brbr We introduce a new portable instrument to allow online, continuous measurement of particle-bound ROS using a chemical assay of 2a?27a?2-dichlorofluorescein (DCFH) with horseradish peroxidase (HRP), via fluorescence spectroscopy. All components of the new instrument are attached to a containing shell, resulting in a compact system capable of automated continuous field deployment over many hours or days. brbr From laboratory measurements, the instrument was found to have a detection limit of a??a??a?ˉ4a?ˉnmol [Hsub2/subOsub2/sub] equivalents per cubic metre (msup3/sup) air, a dynamic range up to at least a??a??a?ˉ2000a?ˉnmol [Hsub2/subOsub2/sub] equivalents per msup3/sup air and a time resolution of a?¤a??a?ˉ12a?ˉmin. The instrument allows for a??a??a?ˉ16a?ˉh automated measurement if unattended and shows a fast response to changes in concentrations of laboratory-generated oxidised organic aerosol. The instrument was deployed at an urban site in London, and particulate ROS levels of up to 24a?ˉnmol [Hsub2/subOsub2/sub] equivalents per msup3/sup air were detected with PMsub2.5/sub concentrations up to 28a?ˉ?μga?ˉmsupa??3/sup. brbr The new and portable Online Particle-bound ROS Instrument (OPROSI) allows fast-response quantification; this is important due to the potentially short-lived nature of particle-bound ROS as well as fast-changing atmospheric conditions, especially in urban environments. The instrument design allows for automated operation and extended field operation with twice-daily presence of an operator. As well as having sensitivity suitable for ambient level measurement, the instrument is also suitable at concentrations such as those required for laboratory and chamber toxicological studies.