中国PM_(2.5)与O_(3)协同控制路径

基于WRF-CAMx(the weather research and forecasting model and the comprehensive air quality model with extensions)空气质量模型定量分析了不同NO_(x)、挥发性有机物(volatile organic compounds,VOCs)在减排情景下全国及重点区域PM_(2.5)与O_(3)浓度变化情况,并通过引入敏感度的概念,评估PM_(2.5)与O_(3)对NO_(x)、VOCs减排的敏感性,直观地揭示了NO_(x)、VOCs减排对PM_(2.5)与O_(3)浓度改善效益,以此提出中国PM_(2.5)与O_(3)协同控制路径.模拟结果表明,NO_(x)减排可有效降低全国及重点区域PM_(2.5)与O_(3)浓度,减排比例较小时,PM_(2.5)浓度下降,但少部分区域O_(3)浓度升高,随着减排比例增加,PM_(2.5)与O_(3)浓度均呈加速下降趋势;VOCs减排过程中,全国及重点区域PM_(2.5)与O_(3)浓度一直保持下降趋势.减排敏感度结果表明,全国及重点区域PM_(2.5)对NO_(x)减排敏感度更高;而O_(3)有所不同,对于全国整体而言,对NO_(x)减排更敏感;重点区域中珠江三角洲地区O_(3)对VOCs减排敏感度更高;“2+26”城市、长江三角洲、汾渭平原地区O_(3)在减排比例较小时,对VOCs减排更敏感,随着减排比例增加,对NO_(x)减排敏感度更高.因此,建议在中长期大气污染物协同减排路径的设计中,将NO_(x)持续减排作为全国及重点区域PM_(2.5)与O_(3)污染改善的核心,将VOCs减排作为短期内降低重点区域PM_(2.5)与O_(3)浓度的关键.

Impacts of meteorology and emission variations on the heavy air pollution episode in North China around the 2020 Spring Festival

Based on the Weather Research and Forecasting model and the Models-3 community multi-scale air quality model(WRF-CMAQ),this study analyzes the impacts of meteorological conditions and changes in air pollutant emissions on the heavy air pollution episode occurred over North China around the 2020 Spring Festival(January to Februray 2020).Regional reductions in air pollutant emissions required to eliminate the PM2.5 heavy pollution episode are also quantified.Our results found that meteorological conditions for the Beijing-Tianjin-Hebei and surrounding"2+26"cities are the worst during the heavy pollution episode around the 2020 Spring Festival as compared with two other typical heavy pollution episodes that occurred after 2015.However,because of the substantial reductions in air pollutant emissions in the"2+26"cities in recent years,and the32%extra reduction in emissions during January to February 2020 compared with the baseline emission levels of the autumn and winter of 2019 to 2020,the maximum PM2.5 level during this heavy pollution episode around the 2020 Spring Festival was much lower than that in the other two typical episodes.Yet,these emission reductions are still not enough to eliminate regional heavy pollution episodes.Compared with the actual emission levels during January to February 2020,a 20%extra reduction in air pollutant emissions in the"2+26"cities(or a 45%extra reduction compared with baseline emission levels of the autumn and winter of 2019 to 2020)could help to generally eliminate regionwide severe pollution episodes,and avoid heavy pollution episodes that last three or more consecutive days in Beijing;a 40%extra reduction in emissions(or a 60%extra reduction compared with baseline emission levels of the autumn and winter of 2019 to 2020)could help to generally eliminate regionwide and continuous heavy pollution episodes.Our analysis finds that during the clean period after the heavy pollution episode around the 2020 Spring Festival,the regionwide heavy pollution episode would only occur with at least a 10-fold increase in air pollutant emissions.