Application of photochemical indicators to evaluate ozone nonlinear chemistry and pollution control countermeasure in China

Ozone sensitivity in China was investigated by using a comprehensive three-dimensional air quality model system WRF-CALGRID. A real case and two cases with 35% emission reduction for either NOx or VOC were conducted for the period of March in 2010. The simulation results of O3 agreed fairly well with the observation data. Based on the meaning of O3 sensitivity, the ratio Ra was defined, with the transition value of 1 to distinguish NOx-sensitive region from VOC-sensitive region. With the aid of Ra, VOC- and NOx-sensitive regions in China were preliminary located. The transition ranges for some photochemical indicators were quantified. Only those of H2O2/NOz and H2O2/HNO3 met the requirement that the 95th percentile VOC-sensitive value should be equal to or lower than the 5th percentile NOx-sensitive value. 0.16-0.40 for H2O2/HNO3 and 0.14-0.28 for H2O2/NOz were adopted to distinguish different O3 sensitivity in China. The results showed that the VOC-sensitive regions are primarily distributed over the urban centers and the developed industrial areas in eastern and southern China, while the NOx-sensitive regions are mainly located in the remote areas of northern and western China. High correlation between Ra and indicators was found, and a new approach to quantify the transition values of indicators was proposed. These indicators can play an important role in the air complex pollution control of urban clusters over East Asia.