基于KZ滤波的京津冀2013~2018年大气污染治理效果分析

Effectiveness of Air Pollution Control Efforts in Beijing–Tianjin–Hebei Region during 2013–2018 Based on the Kolmogorov–Zurbenko Filter

通过国务院“大气十条”等严格的大气污染治理措施的实施,近年来我国空气质量得到全面改善。对大气污染治理效果开展科学分析研究,可为后续空气质量持续改善、污染科学精准治理提供有效科技支撑。由于气象条件是影响污染物浓度分布的重要因素,治理效果分析的一个重要问题是区分气象条件和减排措施对污染物浓度变化的具体贡献。本文利用京津冀地区13个城市2013~2018年86个监测站点逐日PM2.5浓度以及欧洲中期气象预报中心(ECMWF)气象再分析资料,采用KZ(Kolmogorov–Zurbenko)滤波分析PM2.5浓度观测序列的时频特性,将其分解为短期天气影响分量、中期季节变化分量以及长期趋势分量3个部分,针对分解浓度序列建立气象因子回归模型,实现定量评估气象和减排对治理效果的具体贡献。在研究时间段内,京津冀地区13个城市PM2.5浓度的长期分量显著下降(22.2%~58.0%),其中邢台市下降幅度最大(58.0%)。整体分析表明,气象条件和排放源均有利于大气污染的改善,但减排措施是空气质量显著改善的决定性原因,具体贡献为气象条件的影响占18.5%,排放源的影响占81.5%。逐城分析表明,唐山市的气象条件最有利于PM2.5浓度的减小(29.2%),而衡水市的减排措施最有利于PM2.5浓度的减小(92.0%)。

China’s air quality has improved in recent years by the implementation of strict pollution control action plans such as the National“Ten Measures for Air”ratified by the Chinese State Council.To achieve sustained improvements in air quality and targeted pollution control in the coming years the effectiveness of these pollution control initiatives must be scientifically evaluated.Because air quality levels are strongly influenced and at times even dominated by meteorological conditions,a major difficulty of such analysis is quantifying the contributions of meteorological conditions and pollution control initiatives to variations in the respective pollutant concentrations.In this study,we assessed the effectiveness of pollution control efforts for one of the most heavily polluted areas in China-the Beijing-Tianjing-Heibei region-by analyzing(1)the time-frequency properties of the PM2.5 time series collected from 86 monitoring sites in 13 cities of this region during 2013–2018 and(2)the corresponding meteorological conditions retrieved from the reanalysis product of the European Center for Medium-range Weather Forecast(ECMWF).We used the Kolmogorov–Zurbenko filter to separate the original PM2.5 series into three components:Short-term weather-related variations,medium-term seasonal variations,and long-term trends.We constructed regression models to account for the influence of meteorological variables on the PM2.5 concentrations to distinguish their impacts on pollution abatement from those of the emission reduction actions.We found that during 2013–2018,the long-term trends of PM2.5 concentration over 13 cities decreased significantly(22.2%–58.0%),with Xingtai city experiencing the greatest decrease(58.0%).Both meteorological conditions and emission reduction actions contributed to the improvement of air quality,but emission reduction actions were the decisive factor in the significant improvement in air quality.The contributions of meteorological conditions and emission reduction actions were 18.5%and 81.5%,respectively.Among the 13 cities,the meteorological conditions were the most beneficial for Tangshan(29.2%)whereas emission reduction actions played the most important role for Hengshui(92.0%).