北京地区秋冬季大气污染特征及成因分析
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摘要
为了研究近两年北京地区PM2. 5污染特征及成因变化,利用常规观测资料和改进的后向轨迹模型(Traj Stat)对2016～2017年秋冬季大气重污染时段的颗粒物浓度、气象要素和气团传输路径进行了综合分析.结果表明,研究期间北京地区共发生13次持续2 d以上的重污染事件,冬季过程约占61. 5%,且污染程度和持续时间均高于秋季.地面受弱气压场控制、高湿度、静小风以及较低的混合层高度,加之北京三面环山的特殊地势是导致秋冬季静稳型污染频发的重要因素,重污染期间PM2. 5/PM10的平均比值高达0. 86.累积阶段气团主要来自于西北、偏西、西南和东南方向,其中西南和东南路径为典型污染传输通道,轨迹频率为21. 6%.此外,采用WRF-CAMx模型定量估算了2016年12月16～22日典型过程中本地和外来污染源对北京PM2. 5的贡献,结果发现不同气团输送条件下,二者的贡献差异较大.当南部气团输入时,本地贡献会显著下降,以外部区域输送为主导;若气流来自西北方向情况则相反.污染过程期间,本地贡献为16. 5%～69. 3%.
To study the changing of characteristics and formation mechanisms of PM_(2.5) in Beijing during the last two years,particulate matter concentrations,weather conditions,and air-mass trajectories were analyzed during severe pollution episodes in fall and winter2016-2017 using routine observations and the Traj Stat model. Results showed that 13 heavy pollution events,each lasting at least two days,occurred in Beijing. Of these,approximately 61. 5% occurred in winter,characterized by heavier pollution concentrations and longer durations than those occurring in autumn. A low-pressure gradient,high humidity,low surface wind speed,low boundary layer,and particular terrain( i. e.,being surrounded by mountains on three sides) all contributed to the high occurrence frequency of severe pollution episodes in autumn and winter. During the pollution episodes,the average ratio of PM_(2.5) to PM10 reached 0. 86. The airmasses during the accumulation stage were mainly transported from the northwest,west,southwest,and southeast of Beijing. The southwestern and southeastern transmission paths accounted for 21. 6% of the total pollution load. In addition,the WRF-CAMx model was used to quantitatively analyze the contributions of local and external sources to the concentrations of PM_(2.5) in Beijing during 16-22 December 2016. Based on this analysis,PM_(2.5) contributions notably varied with different air-masses; in the case of southern airmasses,external sources dominated the PM_(2.5) concentrations in Beijing and local contributions decreased rapidly; in contrast,in the case of northwestern air-masses,the opposite pattern occurred. Overall,the contribution of local sources to PM_(2.5) concentrations in Beijing varied from 16. 5% to 69. 3% during the monitored pollution episodes.
To study the changing of characteristics and formation mechanisms of PM_(2.5) in Beijing during the last two years,particulate matter concentrations,weather conditions,and air-mass trajectories were analyzed during severe pollution episodes in fall and winter2016-2017 using routine observations and the Traj Stat model. Results showed that 13 heavy pollution events,each lasting at least two days,occurred in Beijing. Of these,approximately 61. 5% occurred in winter,characterized by heavier pollution concentrations and longer durations than those occurring in autumn. A low-pressure gradient,high humidity,low surface wind speed,low boundary layer,and particular terrain( i. e.,being surrounded by mountains on three sides) all contributed to the high occurrence frequency of severe pollution episodes in autumn and winter. During the pollution episodes,the average ratio of PM_(2.5) to PM10 reached 0. 86. The airmasses during the accumulation stage were mainly transported from the northwest,west,southwest,and southeast of Beijing. The southwestern and southeastern transmission paths accounted for 21. 6% of the total pollution load. In addition,the WRF-CAMx model was used to quantitatively analyze the contributions of local and external sources to the concentrations of PM_(2.5) in Beijing during 16-22 December 2016. Based on this analysis,PM_(2.5) contributions notably varied with different air-masses; in the case of southern airmasses,external sources dominated the PM_(2.5) concentrations in Beijing and local contributions decreased rapidly; in contrast,in the case of northwestern air-masses,the opposite pattern occurred. Overall,the contribution of local sources to PM_(2.5) concentrations in Beijing varied from 16. 5% to 69. 3% during the monitored pollution episodes.
引文
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[28]张周祥.秋冬季北京北部重污染事件PM1化学组分特征及气象因素的贡献[D].北京:中国气象科学研究院,2017.
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[31]姚青,蔡子颖,韩素芹,等.天津冬季相对湿度对气溶胶浓度谱分布和大气能见度的影响[J].中国环境科学,2014,34(3):596-603.Yao Q,Cai Z Y,Han S Q,et al.Effects of relative humidity on the aerosol size distribution and visibility in the winter in Tianjin[J].China Environmental Science,2014,34(3):596-603.
[32]王跃思,姚利,王莉莉,等.2013年元月我国中东部地区强霾污染成因分析[J].中国科学:地球科学,2014,44(1):15-26.Wang Y S,Yao L,Wang L L,et al.Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China[J].Science China:Earth Sciences,2014,57(1):14-25.
[2]杨旭,张小玲,康延臻,等.京津冀地区冬半年空气污染天气分型研究[J].中国环境科学,2017,37(9):3201-3209.Yang X,Zhang X L,Kang Y Z,et al.Circulation weather type classification for air pollution over the Beijing-Tianjin-Hebei region during winter[J].China Environmental Science,2017,37(9):3201-3209.
[3]江琪,王飞,张恒德,等.2013~2015年北京市PM2.5、反应性气体和气溶胶粒径的特性分析[J].中国环境科学,2017,37(10):3647-3657.Jiang Q,Wang F,Zhang H D,et al.The characteristics of PM2.5、reactive gas and aerosol size distributions of Beijing from2013 to 2015[J].China Environmental Science,2017,37(10):3647-3657.
[4]程念亮,张大伟,陈添,等.2015年北京市两次红色预警期间PM2.5浓度特征[J].环境科学,2016,37(7):2409-2418.Cheng N L,Zhang D W,Chen T,et al.Concentration characteristics of PM2.5in Beijing during two red alert periods[J].Environmental Science,2016,37(7):2409-2418.
[5]张晗宇,程水源.北京市秋季亚微米细颗粒物浓度及其化学组分特征[J].科技导报,2018,36(2):47-54.Zhang H Y,Cheng S Y.Study on the concentration of submicron fine particles and its chemical constituents in autumn in Beijing[J].Science&Technology Review,2018,36(2):47-54.
[6]王燕丽,薛文博,雷宇,等.京津冀区域PM2.5污染相互输送特征[J].环境科学,2017,38(12):4897-4904.Wang Y L,Xue W B,Lei Y,et al.Regional transport matrix study of PM2.5in Jingjinji region,2015[J].Environmental Science,2017,38(12):4897-4904.
[7]Wen W,He X D,Ma X,et al.Understanding the regional transport contributions of primary and secondary PM2.5components over Beijing during a severe pollution episodes[J].Aerosol and Air Quality Research,2018,18(7):1720-1733.
[8]Liao T T,Wang S,Ai J,et al.Heavy pollution episodes,transport pathways and potential sources of PM2.5during the winter of 2013 in Chengdu(China)[J].Science of the Total Environment,2017,584-585:1056-1065.
[9]Hua Y,Wang S X,Jiang J K,et al.Characteristics and sources of aerosol pollution at a polluted rural site southwest in Beijing,China[J].Science of the Total Environment,2018,626:519-527.
[10]Zhu Y H,Huang L,Li J Y,et al.Sources of particulate matter in China:insights from source apportionment studies published in1987-2017[J].Environment International,2018,115:343-357.
[11]Kim B U,Bae C,Kim H C,et al.Spatially and chemically resolved source apportionment analysis:case study of high particulate matter event[J].Atmospheric Environment,2017,162:55-70.
[12]Wen W,Cheng S Y,Liu L,et al.Source apportionment of PM2.5in Tangshan,China-hybrid approaches for primary and secondary species apportionment[J].Frontiers of Environmental Science&Engineering,2016,10(5):83-96.
[13]何斌,梅世龙,陆琛莉,等.MEIC排放清单在空气质量模式中的应用研究[J].中国环境科学,2017,37(10):3658-3668.He B,Mei S L,Lu C L,et al.The application of MEICemission inventory in air quality model[J].China Environmental Science,2017,37(10):3658-3668.
[14]Wang X Q,Wei W,Cheng S Y,et al.Characteristics and classification of PM2.5pollution episodes in Beijing from 2013 to2015[J].Science of the Total Environment,2018,612:170-179.
[15]薛亦峰,周震,聂滕.2015年12月北京市空气重污染过程分析及污染源排放变化[J].环境科学,2016,37(5):1593-1601.Xue Y F,Zhou Z,Nie T,et al.Exploring the severe haze in Beijing during December,2015:pollution process and emissions variation[J].Environmental Science,2016,37(5):1593-1601.
[16]Jia J,Cheng S Y,Liu L,et al.An integrated WRF-CAMx modeling approach for impact analysis of implementing the emergency PM2.5control measures during red alerts in Beijing in December 2015[J].Aerosol and Air Quality Research,2017,17(10):2491-2508.
[17]江琪,王飞,张恒德,等.北京市PM2.5和反应性气体浓度的变化特征及其与气象条件的关系[J].中国环境科学,2017,37(3):829-837.Jiang Q,Wang F,Zhang H D,et al.Analysis of temporal variation characteristics and meteorological conditions of reactive gas and PM2.5in Beijing[J].China Environmental Science,2017,37(3):829-837.
[18]刘超.典型区域PM2.5污染特征及影响因素研究[D].北京:北京工业大学,2014.
[19]王占山,李云婷,孙峰,等.2015年1月下旬北京市大气污染过程成因分析[J].环境科学学报,2016,36(7):2324-2331.Wang Z S,Li Y T,Sun F,et al.Formation mechanism of air pollution episodes in Beijing in late January 2015[J].Acta Scientiae Circumstantiae,2016,36(7):2324-2331.
[20]Duncan B N,Martin R V,Staudt A C,et al.Interannual and seasonal variability of biomass burning emissions constrained by satellite observations[J].Journal of Geophysical Research:Atmospheres,2003,108(D2):4100.
[21]廖晓农.华北秋季强弱线型对流发展时天气尺度环境条件探讨[J].气象,2013,39(3):291-301.Liao X N.A discussion on the synoptic condition for the autumn linear convection developing in Huabei area[J].Meteorological Monthly,2013,39(3):291-301.
[22]邓发荣,康娜,Kumar K R,等.长江三角洲地区大气污染过程分析[J].中国环境科学,2018,38(2):401-411.Deng F R,Kang N,Kumar K R,et al.Analysis of air pollution episodes over different cites in the Yangtze River Delta[J].China Environmental Science,2018,38(2):401-411.
[23]程念亮,李云婷,张大伟,等.2013年1月北京市一次空气重污染成因分析[J].环境科学,2015,36(4):1154-1163.Cheng N L,Li Y T,Zhang D W,et al.Formation mechanism of a serious pollution event in January 2013 in Beijing[J].Environmental Science,2015,36(4):1154-1163.
[24]杨孝文,周颖,程水源,等.北京冬季一次重污染过程的污染特征及成因分析[J].中国环境科学,2016,36(3):679-686.Yang X W,Zhou Y,Cheng S Y,et al.Characteristics and formation mechanism of a heavy winter air pollution event in Beijing[J].China Environmental Science,2016,36(3):679-686.
[25]王跃.北京PM2.5时空变化特征及重污染时段气象成因研究[D].南京:南京信息工程大学,2014.
[26]Solazzo E,Bianconi R,Pirovano G,et al.Operational model evaluation for particulate matter in Europe and North America in the context of AQMEII[J].Atmospheric Environment,2012,53:75-92.
[27]贾佳,韩力慧,程水源,等.京津冀区域PM2.5及二次无机组分污染特征研究[J].中国环境科学,2018,38(3):801-811.Jia J,Han L H,Cheng S Y,et al.Pollution characteristic of PM2.5and secondary inorganic ions in Beijing-Tianjin-Hebei region[J].China Environmental Science,2018,38(3):801-811.
[28]张周祥.秋冬季北京北部重污染事件PM1化学组分特征及气象因素的贡献[D].北京:中国气象科学研究院,2017.
[29]Liu X G,Li J,Qu Y,et al.Formation and evolution mechanism of regional haze:a case study in the megacity Beijing,China[J].Atmospheric Chemistry and Physics,2013,13(9):4501-4514.
[30]Sun Y L,Zhang Q,Schwab J J,et al.A case study of aerosol processing and evolution in summer in New York City[J].Atmospheric Chemistry and Physics,2011,11(24):12737-12750.
[31]姚青,蔡子颖,韩素芹,等.天津冬季相对湿度对气溶胶浓度谱分布和大气能见度的影响[J].中国环境科学,2014,34(3):596-603.Yao Q,Cai Z Y,Han S Q,et al.Effects of relative humidity on the aerosol size distribution and visibility in the winter in Tianjin[J].China Environmental Science,2014,34(3):596-603.
[32]王跃思,姚利,王莉莉,等.2013年元月我国中东部地区强霾污染成因分析[J].中国科学:地球科学,2014,44(1):15-26.Wang Y S,Yao L,Wang L L,et al.Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China[J].Science China:Earth Sciences,2014,57(1):14-25.