Development of an active ozone production efficiency measuring system under varying NOx and VOCs 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 reduction of NOx and VOCs emissions. However, the ozone production rates (OPRs), which heavily influences on ozone concentration, non-linearly varies with respect to the NOx concentration. Due to this fact few attempts known as MOPS (Measurement of Ozone Production Sensor) have been made to directly monitor the OPRs. To characterize the MOPS, radical measurements are essential due to its high wall loss issue which limits the possibility in general use. To overcome this difficulty, we developed a system to directly evaluate the ozone production efficiency (OPE) rather than OPRs with four chamber system, in addition to the integration of active light source. By adding additional light source with solar mimicked radiation patterns, we were able to accelerate the chemistry which results the reduction in residence time as well as time response of the instrument. In addition, 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). Concentration of resulted ozone and NOx after the chamber were monitored by chemiluminescence instrument with both photolytic and molybdenum converters. Test results performed in the laboratory and campus of Gwangju Institute of Science and Technology in Korea will be presented.