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

Abstract

The levels of tropospheric ozone (O3) are closely related to regional meteorological conditions, precursor emissions, and geographical environments, which have a significant negative impact on human health. The concentrations of O3 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 O3 in Northeast China. Here, the O3 concentration, meteorological observation data, precursors (NO2), 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 O3 concentrations were investigated using statistical analysis, kriging interpolation, spatial autocorrelation analysis, cold-hot spot analysis, and geographic detectors, and the effects of meteorological factors, NO2, and green land area on O3 concentrations were evaluated seasonally and spatially. The results showed that O3 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 O3 concentrations, and the over-standard rates were also the highest (>10%). The spatial distribution showed that the O3 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 O3 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 O3 pollution, the north had cold spots with excellent O3 levels, and the central region did not exhibit strong spatial agglomerations. A weak significant negative correlation between O3 and NO2 indicated that the emissions of NOx derived from human activities have weak effects on the O3 concentrations, and wind speed and sunshine duration had little effect on spatial differentiation of the O3 concentrations. Spatial variability in O3 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 O3 concentrations. In cold spots with low O3 concentrations, the relative humidity and green land area jointly affected the spatial distributions of O3.