山东省环境空气中PM2.5与O3的复合污染特征与时空变化趋势
Characteristics and Spatiotemporal Variation of PM2.5 and O3 in Shandong Province
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摘要: 摘要:山东省PM2.5-O3复合特征突出,空间差异性明显,因此本文基于2016—2020年国控和省控环境空气自动监测站监测数据及同期各气象代表站气象监测数据,分析PM2.5和O3时空分布的变化特征,初步探究其与气象因子及前体物的关系. 结果表明:①2016—2020年山东省空气质量逐步改善,优良天数比例上升了7.1%,重污染天数比例下降了3.5%. 除O3年评价值上升9.6%以外,SO2、PM10、PM2.5、CO和NO2的浓度均下降,降幅依次为61.3%、29.8%、28.6%、26.3%和11.4%. 各市PM2.5年评价值均下降(范围为18.4%~34.9%);除德州市外,其他15市O3年评价值均上升,滨州市的升幅最大(30.8%). 1月PM2.5平均浓度最高,呈现先下降后上升的年变化趋势,6月O3平均浓度最高,且逐年上升. ②PM2.5和O3都呈现内陆地区高于沿海地区的分布特征,PM2.5浓度在西部内陆地区较高,O3浓度在中北部内陆地区较高,PM2.5-O3复合污染特征在中西部地区较明显. 统计期间共计出现PM2.5-O3复合污染日224 d,分布在2—11月,出现天数逐年减少. ③为探究PM2.5-O3复合污染的影响因素及气象特征,进行相关性分析及气象因子阈值筛查,结果表明,PM2.5和O3_8 h日均浓度与其主要前体物和气象因子均呈现相反的相关关系,且对不同因子的响应有一定区域性差异. 统计结果显示,当气温为14.9~24.1 ℃、湿度为55.5%~75.1%、风速为0.6~2.9 m/s、气压为992.8~1018.8 hPa时PM2.5-O3复合污染易于发生,该条件下大部分城市的气温、湿度和气压均值介于单独发生PM2.5和O3污染时的对应因子均值,但平均风速小于单独发生PM2.5和O3污染的平均风速. 研究显示,“十三五”期间山东省PM2.5浓度波动下降,O3浓度波动上升,二者的协同关系日趋明显,气象因素对PM2.5和O3的生成和累积有一定影响.Abstract: Abstract : The composite characteristics of PM2.5-O3 in Shandong Province were relatively prominent and also showed obvious spatial differences. To study characteristics of co-pollution of surface O3 and PM2.5 in Shandong province, spatial distributions of the PM2.5 and O3 concentrations were analyzed and the relationship between O3 and PM2.5, meteorological parameters and their precursors were explored based on the monitoring data of national and provincial ambient air quality monitoring sites and meteorological sites from 2016 to 2020. The results indicated that: (1) During 2016-2020, the air quality in Shandong Province improved gradually with excellent and good days increasing by 7.1% and heavily polluted days decreasing by 3.5%. Except for the 90th percentile of the maximum daily 8-hour average of the O3 concentrations (O3 MDA8 90th), which increased by 9.6%, the concentrations of SO2, PM10, PM2.5, CO and NO2 decreased by 61.3%, 29.8%, 28.6%, 26.3% and 11.4%, respectively. The annual average values of PM2.5 in all cities of Shandong Province declined with decreasing ratios ranging from 18.4% to 34.9%. The O3 MDA8 90th increased in all the cities except for Dezhou City. The largest increasing ratio of O3 MDA8 90th was 30.8% in Binzhou City. The highest average PM2.5 concentrations was observed in January while the highest average O3 concentration was observed in June. The PM2.5 concentrations in January decreased and then increased from 2016 to 2020, while the O3 concentrations in June increased from 2016 to 2020. (2) The PM2.5 and O3 concentrations in inland cities were higher than those in coastal cities with higher PM2.5 concentration observed in western inland areas and higher O3 concentrations in central and northern inland areas. Synergistic pollution characteristics of PM2.5 and O3 were obvious in the central and western Shandong Province. There were 224 days characterized by the synergistic pollution of PM2.5 and O3 during the whole study period, which mainly occurred from February to November. The days with the synergistic pollution of PM2.5 and O3 decreased year by year. (3) The correlationship between concentrations of PM2.5 or O3 and meteorological factors, as well as threshold of meteorological factors during PM2.5, O3 or PM2.5-O3 composite pollutant days, were also carried out. The results showed that the daily average PM2.5 and O3_8 h concentrations had negative correlations with their precursors and meteorological parameters. Moreover, spatial differences existed in the correlation between PM2.5 and O3, their precursors and meteorological parameters. The statistical results show that PM2.5-O3 complex pollution favorably occurred when the atmospheric temperature, relative humidity, wind speed and atmospheric pressure ranged from 14.9-24.1 °C, from 55.5%-75.1%, 0.6-2.9 m/s and 992.8-1018.8 hPa, respectively. In most cities of Shandong Province, the average values of atmospheric temperature, relative humidity and atmospheric pressure during the synergistic pollution of PM2.5 and O3 were between those during the PM2.5 pollution and those during the O3 pollution. But the average wind speed during the synergistic pollution of PM2.5 and O3 was lower than those during the PM2.5 pollution and during the O3 pollution. In summary, the study showed that on a whole the PM2.5 concentration declined but the O3 concentration enhanced, and synergistic changes of PM2.5 and O3 became more obvious during the ‘13th Five-Year Plan’ period. Meteorological factors played a role in the formation and accumulation of PM2.5 and O3.
Keywords : PM2.5 and O3; pollution characteristics; temporal and spatial distribution; meteorological factors; Shandong Province
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