PM_(2.5)和臭氧对前体物减排和气象变化的响应及其政策启示

Responses of PM_(2.5)and O_(3)to Emission Reduction and Meteorology Variation and Their Policy Implications

《大气污染防治行动计划》实施以来,我国重点区域PM_(2.5)浓度快速下降,但臭氧(O_(3))浓度逐步上升,大气污染控制形势已由单一的PM_(2.5)控制转变为PM_(2.5)和O_(3)的协同控制.了解PM_(2.5)和O_(3)对前体物排放变化和气象条件变化的响应,对制定PM_(2.5)和O_(3)协同控制策略具有重要意义.本文通过使用FNL全球再分析资料和自下而上的排放清单ABaCAS-EI,结合三维空气质量模式和响应曲面模型,评估前体物变化和气象条件变化后PM_(2.5)和O_(3)浓度的响应,并依据解析的响应关系提出了前体物减排、联防联控区域划分和目标设定等方面的政策建议.结果表明:(1)VOCs减排对降低各省份PM_(2.5)和O_(3)浓度均有利,NO_(x)的减排量不足会导致京津冀、长三角地区的O_(3)浓度和京津冀地区的PM_(2.5)浓度增加,为避免PM_(2.5)和O_(3)年评价值反弹需要的VOCs与NO_(x)减排比分别为15%~25%(PM_(2.5))和5%~90%(O_(3)).(2)O_(3)污染防治需要更大范围的联防联控,对于京津冀地区,需要考虑引入河南省和山东省的联合控制,对于长三角和珠三角地区,还需要联合江西省、福建省进行控制.(3)气象条件对PM_(2.5)和O_(3)背景值的影响较大,使用3年或5年滑动平均值可以有效降低气象条件年际变化对PM_(2.5)和O_(3)浓度的影响(对于PM_(2.5),2008—2019年其背景值极差的降幅分别为35%~81%或60%~86%;对于O_(3),极差的降幅分别为40%~67%或53%~87%).采用多年滑动平均有助于科学设定和考核PM_(2.5)和O_(3)的控制目标.研究显示:PM_(2.5)和O_(3)的协同控制依赖于NO_(x)和VOCs的协同减排,其减排比例在不同地区存在差异;此外,科学的PM_(2.5)和O_(3)的协同控制还需要更大范围的联防联控和评价指标的持续更新.

Since the implementation of the Action Plan of Air Pollution Prevention and Control,the PM_(2.5)concentrations in key regions has decreased rapidly,while O_(3)concentration has gradually increased.Therefore,the air pollution control target has changed from individual PM_(2.5)control to coordinated control of PM_(2.5)and O_(3).Understanding the responses of PM_(2.5)and O_(3)to changes in precursor emissions and meteorological conditions is of great significance for formulating coordinated control strategies for PM_(2.5)and O_(3).This study evaluated the response of PM_(2.5)and O_(3)concentrations to the changes of precursors and meteorological conditions using FNL reanalysis dataset,emission inventory of Air Benefit and Cost and Attainment Assessment System(ABaCAS-EI),the air quality model and response surface model.Based on the analysis of the response relationship,policy recommendations on precursor emission reduction,regional division of joint prevention and control,and target setting were proposed.The results show that:(1)VOCs emission reduction is beneficial to reducing PM_(2.5)and O_(3)concentration in all provinces.Insufficient NO_(x)emission reduction will increase O_(3)concentration especially in the Beijing-Tianjin-Hebei and Yantze River Delta regions.Meanwhile,the VOCs to NO_(x)emission reduction ratio is 15%-25%for PM_(2.5)and 5%-90%for O_(3)to avoid this adverse effect.For the Beijing-Tianjin-Hebei Region,the joint control of Henan and Shandong may need to be considered.For the Yangtze River Delta and Pearl River Delta,the joint control of Jiangxi and Fujian may be more important in the future.(3)Meteorological conditions have a great influence on PM_(2.5)and O_(3)background values.The effects of three-year moving average and five-year moving average on reducing PM_(2.5)and O_(3)fluctuation in each region are 35%-81%and 60%-86%for PM_(2.5),and 40%-67%or53%-87%for O_(3).Applying multi-year moving averages to mitigate the variation of meteorological conditions helps to scientifically set and assess the targets for PM_(2.5)and O_(3).The results indicate that the coordinated control of PM_(2.5)and O_(3)depends on the coordinated emission reduction of NO_(x)and VOCs,and the specific emission reduction ratio varies for different regions.In addition to precursor emission reduction,scientific and coordinated control of PM_(2.5)and O_(3)also requires a wider range of joint prevention and control and continuous update of evaluation indicators.