Effects of Seasonal Variation on Spatial and Temporal Distributions of Ozone in Northeast China

The levels of tropospheric ozone (O 3 ) are closely related to regional meteorological conditions, precursor emissions, and geographical environments, which have a significant negative impact on human health. The concentrations of O 3 were relatively low, while the spatial distribution was strongly heterogeneous in Northeast China; however, little is known about how the influencing factors affect the distribution of O 3 in Northeast China. Here, the O 3 concentration, meteorological observation data, precursors (NO 2 ), and vegetation coverage data from 41 monitoring cities in Northeast China from 2017 to 2020 were collected and analyzed. The spatial–temporal distributions and evolution characteristics of O 3 concentrations were investigated using statistical analysis, kriging interpolation, spatial autocorrelation analysis, cold–hot spot analysis, and geographic detectors, and the effects of meteorological factors, NO 2 , and green land area on O 3 concentrations were evaluated seasonally and spatially. The results showed that O 3 pollution in Northeast China was generally at a relatively low level and showed a decreasing trend during 2017–2020, with the highest concentrations in the spring and the lowest concentrations in the autumn and winter. May–July had relatively high O 3 concentrations, and the over-standard rates were also the highest (>10%). The spatial distribution showed that the O 3 concentration was relatively high in the south and low in the northeast across the study area. A globally significant positive correlation was derived from the spatial autocorrelation analysis. The cold–hot spot analysis showed that O 3 concentrations exhibited spatial agglomerations of hot spots in the south and cold spots in the north. In Northeast China, the south had hot spots with high O 3 pollution, the north had cold spots with excellent O 3 levels, and the central region did not exhibit strong spatial agglomerations. A weak significant negative correlation between O 3 and NO 2 indicated that the emissions of NOx derived from human activities have weak effects on the O 3 concentrations, and wind speed and sunshine duration had little effect on spatial differentiation of the O 3 concentrations. Spatial variability in O 3 concentrations in the spring and autumn was mainly driven by temperature, but in the summer, the influence of temperature was weakened by the relative humidity and precipitation; no factor had strong explanatory power in the winter. The temperature was the only controlling factor in hot spots with high O 3 concentrations. In cold spots with low O 3 concentrations, the relative humidity and green land area jointly affected the spatial distributions of O 3 .