HONO Observation and Assessment of the Effects of Atmospheric Oxidation Capacity in Changzhou During the Springtime of 2017

HONO measurement was conducted using a wet-chemistry-based method at the Changzhou Environmental Monitoring Center in April 2017. HONO ranged from 0.2-13.9 μg·m-3 with an average of (2.9±2.3) μg·m-3. O3, HCHO, volatile organic compounds, photolysis frequency, and meteorological parameters were simultaneously monitored.·OH concentration was simulated by a Master Chemical Mechanism box model and the daytime maximum·OH concentration ranged from 1.0×106 to 14×106 molecules per cubic centimeter. The formation rates of·OH by photolysis of HONO, O3, HCHO, H2O2, and alkene ozonolysis were calculated as well. The effects of the five sources on atmospheric oxidation capacity were revealed:O3 photolysis (46.4%) > HONO photolysis (41.1%) > alkene ozonolysis (10.9%) > HCHO photolysis (1.5%) > H2O2 photolysis (0.1%). HONO photolysis for OH radical production played a major role in the early morning, before with an increase in O3 concentration, O3 photolysis began to account for most of the·OH production. After 17:00, due to a significant decrease in the intensity of solar radiation, the alkene ozonolysis started playing a major role in the formation of·OH. The photolysis of formaldehyde and hydrogen peroxide played a negligible role in·OH radical production in this study.