Reactive oxygen species (ROS) emissions and formation pathways in residential wood smoke under different combustion and aging conditions

Abstract

Abstract. Wood combustion emissions can induce oxidative stress in the human respiratory tract caused by reactive 15 oxygen species (ROS), either directly or after oxidation in the atmosphere. To improve our understanding of the ROS generation potential of wood combustion emissions, a suite of smog chamber (SC) and potential aerosol mass (PAM) chamber experiments were conducted under well determined conditions for different combustion devices and technologies, different fuel types, operation methods, combustion regimes, combustion phases and aging conditions. The ROS content as well as the chemical properties of the aerosols were quantified by a novel ROS 20 analyzer and a high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS). For all eight tested combustion devices, primary ROS concentrations substantially increased upon aging. The level of primary and aged ROS emission factors (EF ROS ) were dominated by the combustion device (within different combustion technologies) and to a greater extent by the combustion regimes: the variability within one device was much higher than the variability of EF ROS from different devices. Aged EF ROS under bad combustion conditions were ~2-80 times higher 25 than under optimum combustion conditions. EF ROS from automatically operated combustion devices were on average one order of magnitude lower than those from manually operated appliances, which indicates that automatic combustion devices operated at optimum conditions to achieve near-complete combustion should be employed to