Development of an active ozone production efficiency measuring system under varying precursors conditions

Abstract

Surface ozone is a secondary pollutant formed by precursors of VOCs and NOx via the photochemical reactions in the troposphere. Due to its detrimental effects on living creatures, many efforts have been invested to control the near surface ozone by focusing on the reduction of NOx and VOCs emissions. However, the ozone production rates (OPRs), which heavily influences ozone concentration, non-linearly vary concerning its precursor abundances. Thus, the demand for the direct observation of OPRs has been increased. Starting with the Measurement of Ozone Production Sensor (MOPS), few attempts have been made to monitor OPRs, however, due to their high wall loss issue as well as difficulties in the absolute quantitative evaluation of OPRs, limited attempts for ambient measurements have been achieved so far. To overcome this difficulty, we developed a system to directly evaluate the ozone production sensitivity (OPS) by normalized OPRs with NOx and selective VOC species rather than OPRs using four chamber system. To minimize the chemical and physical interferences, an active system is designed by integrating the solar mimicking light source and by injecting a known amount of precursors. We were able to accelerate the chemistry which results in the reduction in residence time as well as time response of the instrument. Also, the four chamber system enables us to simultaneously monitor the control condition to compare the experimental ones (i.e. UV blocked and addition of precursors chambers). The concentration of resulted ozone and NOx after the chamber was monitored by chemiluminescence instrument with both photolytic and molybdenum convertors. Characterizing and test results performed in the laboratory and campus of GIST. The experimental period is from October to December 2019. Two precursors injected simultaneously sampling ambient air in an independent experiment, 2-10 ppb of NO and 1 ppb of isoprene. Standard condition and controlled condition compared to figure out OPS to changed precursors condition. Surface ozone is a secondary pollutant formed by precursors of VOCs and NOx via the photochemical reactions in the troposphere. Due to its detrimental effects on living creatures, many efforts have been invested to control the near surface ozone by focusing on the reduction of NOx and VOCs emissions. However, the ozone production rates (OPRs), which heavily influence ozone concentration, non-linearly vary for its precursor abundances. Thus, the demand for the direct observation of OPRs has been increased. Starting with the Measurement of Ozone Production Sensor (MOPS), few attempts have been made to monitor OPRs, however, due to their high wall loss issue as well as difficulties in the absolute quantitative evaluation of OPRs, limited attempts for ambient measurements have been achieved so far. To overcome this difficulty, we developed a system to directly evaluate the ozone production sensitivity (OPS) by normalized OPRs with NOx and selective VOC species rather than OPRs using four chamber system. To minimize the chemical and physical interferences, the active system is designed by integrating the solar mimicking light source and by injecting a known amount of precursors. We were able to accelerate the chemistry which results in the reduction in residence time as well as time response of the instrument. Also, the four chamber system enables us to simultaneously monitor the control condition to compare the experimental ones (i.e. UV blocked and addition of precursors chambers). The concentration of resulted ozone and NOx after the chamber was monitored by chemiluminescence instrument with both photolytic and molybdenum convertors. Characterizing and test results performed in the laboratory and campus of GIST. The experimental period is from October to December 2019. Two precursors injected simultaneously sampling ambient air in an independent experiment, 2-10 ppb of NO and 1 ppb of isoprene. Standard condition and controlled condition compared to figure out OPS to changed precursors condition.