Urban–Rural Comparisons of Biogenic Volatile Organic Compounds and Ground-Level Ozone in Beijing

Abstract

Ground-level ozone (O3) pollution has been a severe environmental and health problem for decades. The importance of biogenic volatile organic compounds (BVOCs) in the formation of tropospheric photochemistry O3 has been highlighted, especially in areas of rapid urbanization. We conducted simultaneous measurements of trace gases, including NO, NOX, O3, and BVOCs (i.e., isoprene and α-pinene), in the urban and rural forest areas of Beijing to determine the relationships between them. The results highlight the differences between the urban and rural forest areas of Beijing in terms of ambient air concentrations of BVOCs and O3, and the interrelationships between BVOCs, NOX, and ozone were quantified. Moreover, the isoprene concentration was found to be higher in the atmosphere of the urban site than of the rural site, which had higher α-pinene concentrations and higher O3 concentrations. The NOX concentration was higher at the urban site than at the rural site, and there was a significant exponential relationship between NOX and O3 at the urban site, indicating that the impact of NOx on O3 at the urban site was greater than that at the rural site. The O3 concentration increased with rising isoprene and α-pinene in both sites. In the case of substantially increased BVOC concentrations, declining NOX concentrations strongly promote the formation of O3. Consideration should be given to planting tree species with low-BVOC emissions, as they are crucial for mitigating O3 pollution in urban areas. Additionally, the relationships between BVOCs, NOX, and O3 should be considered in policymaking related to O3 control.