Inverse Relations of PM2.5 and O3 in Air Compound Pollution between Cold and Hot Seasons over an Urban Area of East China

Abstract

By analyzing the data of urban air pollutant measurements from 2013 to 2015 in Nanjing, East China, we found that the correlation coefficients between major atmospheric compound pollutants PM 2.5 and O 3 were respectively 0.40 in hot season (June, July and August) and −0.16 in cold season (December, January and February) with both passing the confidence level of 99%. This provides evidence for the inverse relations of ambient PM 2.5 and O 3 between cold and hot seasons in an urban area of East China. To understand the interaction of PM 2.5 and O 3 in air compound pollution, the underlying mechanisms on the inversion relations between cold and hot seasons were investigated from the seasonal variations in atmospheric oxidation and radiative forcing of PM 2.5 based on three-year environmental and meteorological data. The analyses showed that the augmentation of atmospheric oxidation could strengthen the production of secondary particles with the contribution up to 26.76% to ambient PM 2.5 levels. High O 3 concentrations in a strong oxidative air condition during hot season promoted the formation of secondary particles, which could result in a positive correlation between PM 2.5 and O 3 in hot season. In cold season with weak atmospheric oxidation, the enhanced PM 2.5 levels suppressed surface solar radiation, which could weaken O 3 production for decreasing ambient O 3 level with the low diurnal peaks. Under the high PM 2.5 level exceeding 115 µg·m −3 , the surface O 3 concentration dropped to 12.7 µg·m −3 at noon with a significant inhibitory effect, leading to a negative correlation between PM 2.5 and O 3 in cold season. This observational study revealed the interaction of PM 2.5 and O 3 in air compound pollution for understanding the seasonal change of atmospheric environment.

Spatiotemporal Distribution of PM2.5 and O3 and Their Interaction During the Summer and Winter Seasons in Beijing, China

“…Feng et al [37] pointed out that high aerosol concentrations can significantly decrease photolysis frequencies and reduce O 3 concentration by more than 50 µg/m 3 in the summertime. In addition, previous studies also reported a significant positive correlation between PM 2.5 and O 3 concentrations during the summertime [38,39]. The discrepancy in these studies suggests that the interaction between O 3 and PM 2.5 in the atmosphere may vary over time across space, which should be further investigated.…”

“…Numerous epidemiological studies found that O3 had an association with premature mortality [55]. A recent study reported that O3 has replaced PM2.5 as the chief pollutant in economically developed areas of China (e.g., Beijing-Tianjin-Hebei, Yangtze To study the effect of PM 2.5 concentration on O 3 concentration in winter, we analyzed the diurnal variation of O 3 under four PM 2.5 levels, selected on the basis of previous researches by Jia et al [38]: exceeding 115 µg/m 3 , from 75 to 115 µg/m 3 , from 35 to 75 µg/m 3 , and below 35 µg/m 3 . When PM 2.5 level was greater than 115 µg/m 3 , O 3 concentration was low with small hourly variation.…”

“…To study the effect of O 3 concentrations on PM 2.5 concentrations in summer, the diurnal variation of PM 2.5 was displayed under four O 3,max (daily maximum O 3 concentration) levels (see Figure 8) [38]: exceeding 200 µg/m 3 , from 160 to 200 µg/m 3 , from 100 to 160 µg/m 3 , and below 100 µg/m 3 . When O 3,max was greater than 200 µg/m 3 , PM 2.5 concentration was the highest and the diurnal variation was significant, with the maximum PM 2.5 concentration observed at 10:00.…”

“…When O3, max exceeded 200 μg/m 3 , 160-200 μg/m 3 , 100-160 μg/m 3 , and below 100 μg/m 3 , respectively, the average PM2.5/CO ratios were 0.083, 0.075, 0.055, and 0.048, respectively. To study the effect of PM2.5 concentration on O3 concentration in winter, we analyzed the diurnal variation of O3 under four PM2.5 levels, selected on the basis of previous researches by Jia et al [38]: exceeding 115 μg/m 3 , from 75 to 115 μg/m 3 , from 35 to 75 μg/m 3 , and below 35 μg/m 3 . When PM2.5 level was greater than 115 μg/m 3 , O3 concentration was low with small hourly variation.…”

The inflammatory potential of diet impacts the association between air pollution and childhood asthma

“…10 Although studies have been conducted under ozone exposure, it was recently described that high ozone concentrations with strong atmospheric oxidation could promote the secondary particle formation enhancing ambient PM2.5 levels. 22 Moreover, the synergic effect when considering all dietary components seems to have a larger impact on disease pathogenesis than individual nutrients and bioactive compounds. 12 Therefore, we used the DII to describe the overall intake of food for each child, considering the combination, frequency, quantity, and variety of the diet.…”