Emission dynamics of reactive oxygen species and oxidative potential in particles from a gasoline car and wood stove

Abstract. Air pollution is one of the largest environmental health risks and one of the leading causes of adverse health outcomes and mortality worldwide. The possible importance of the oxidative potential (OP) as a metric to quantify particle toxicity in air pollution is increasingly being recognized. In this work, the OP and reactive oxygen species (ROS) activity of particles from fresh and aged gasoline passenger car emissions and residential wood combustion (RWC) emissions were investigated using two novel instruments. Applying online instruments using an ascorbic acid (AA) and 2’,7’-dichlorodihydrofluorescein (DCFH) assay provides a much higher time resolution compared to traditional filter-based methods and allows for new insights into highly dynamic changes in OP and ROS activity of these sources. Due to the efficiency of the particulate filter in the Euro 6d car, almost no primary particles were emitted and thus no particle OP and ROS was detected in primary exhaust. However, a substantial and highly dynamic OP and ROS activity was observed after photochemical ageing due to the formation of secondary particles. Increasing OP and ROS activity due to ageing was also observed when comparing fresh and aged RWC emissions. Overall, RWC emissions had significantly higher OP and ROS signals compared to car emissions. This suggests that aged RWC emissions could be a major contributor to air pollution toxicity, and may be an intrinsically more harmful emission source than car exhaust, although the formation potential for secondary particles from car emissions was still high. These measurements illustrate the strong differences and highly dynamic nature of toxicity-relevant particle properties from two air pollution sources and could contribute to more efficient air pollution mitigation policies.