Characterization of Urban Ozone and Non-Methane Hydrocarbon Pollution in Heilongjiang Province

This study utilizes ambient air quality monitoring data from 13 prefecture-level cities in Heilongjiang Province to systematically analyze the pollution characteristics and dynamic evolution of ozone (O3) and non-methane hydrocarbons (NMHCs). The findings reveal that overall air quality in Heilongjiang Province has improved substantially in recent years. The concentrations of SO2, NO2, PM10, PM2.5 and CO in 2023 decreased significantly compared with 2015, with an average reduction of 38.7%. However, O3 concentrations have continued to rise, indicating that O3 pollution has become an increasingly pressing environmental concern. On an annual scale, the monthly average O3 concentration in 2023 displayed a “clear single-peak” pattern, reaching its maximum in June, at a concentration of 139 μg/m3. In contrast, the monthly average NMHC concentration exhibited a “distinct double-peak” pattern, with elevated levels in January and December, at 59.4 and 48.35 μg/m3, respectively. From an hourly perspective, the highest O3 concentrations across the 13 cities occurred between 11:00 and 17:00, while NMHC concentrations showed an opposite trend. Furthermore, during the heating season (October to April of the following year), O3 and NMHC concentrations increased by 0.78 and 1.56 times, respectively, compared with the non-heating season. In terms of ambient air quality levels, both O3 and NMHC concentrations exhibited a gradual upward trend under conditions of “excellent”, “good”, and “light pollution”. However, under “moderate pollution”, “heavy pollution”, and “severe pollution” levels, O3 and NMHC concentrations exhibited irregular patterns, likely due to the interaction of multiple complex factors. O3 pollution follows a “central concentration and peripheral diffusion” pattern, reflecting the combined influence of human activities and natural conditions. In contrast, NMHC concentrations display pronounced spatial heterogeneity, with low levels in the west and high levels in the east, primarily driven by regional differences in industrial structure and environmental conditions. In summary, this study aims to elucidate the spatiotemporal distribution characteristics of O3 and NMHC pollution in Heilongjiang Province and their complex relationship with air quality levels, providing a scientific basis for future pollution prevention and control strategies. Subsequent research should focus on identifying the underlying causes of pollution to develop more precise and effective mitigation measures, thereby continuously improving ambient air quality in the province.