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挥发性有机物(volatile organic compounds,VOCs)为饱和蒸汽压在标准状况下大于133.3 Pa、沸点低、分子量小、常温状态下易挥发的有机化合物[1]. VOCs来源丰富且复杂,来源包括生物源(如植物排放和火山爆发等)和人为源(如溶剂挥发、燃料燃烧和机动车排放等),其中城市地区主要来自于人为源的VOCs因为其危害较大而受到广泛关注. VOCs的危害性主要分为两个方面:一是环境影响,VOCs能发生氧化反应,产生臭氧(O3)和二次有机气溶胶(SOA)从而影响空气质量[2 − 3],具体表现为在对流层中,光化学反应活性较强的VOCs物种既可在光照条件下与NOx(氮氧化物)发生反应生成O3[4 − 5],也可与大气中的氧化剂(如羟基自由基等)发生反应生成较弱挥发性的VOCs,进而经过吸附等物理过程分散到颗粒相中转化为SOA[6];另一方面,部分VOCs会损害人体的生理功能和免疫系统等,例如苯、甲苯、乙苯和二甲苯(BTEX)和卤代烃会损害神经和造血系统,甚至导致癌症[7 − 8]. 因此,更好地了解大气中VOCs的特征,是深入分析VOCs对O3、SOA污染形成和人类健康影响的关键.
VOCs和O3是我国城市大气复合污染中的重要组成部分. 与其他大气污染物相比,O3污染问题更加复杂,治理难度更大、周期更长[9]. 西北地区大气环境特殊,沙尘量高且湿度较低,近年来大气二次污染程度不断加剧,防治形势严峻[10]. 胡琳等[11]在西北城市O3污染的研究中指出当温度高于30 ℃、相对湿度低于60%时,容易出现高浓度臭氧现象. 刘松等[12]研究了2013—2016年西安O3时空变化特性与影响因素,发现高浓度O3主要出现在高温度、低湿度且风向为东南风或南风的天气背景下. 除气象因素外,许多研究也关注了人为排放和大气化学方面对臭氧的影响. 张瑞欣[13]研究西北工业城市乌海市臭氧污染成因时指出VOCs排放与O3污染高度相关,而VOCs主要来源包括工艺过程源、生物质燃烧源、炼焦及精细化工源、非金属制品源. 曹泽磊[14]研究西安市高新区O3及其前体物污染时指出,机动车尾气排放、汽车维修与喷漆过程排放是VOCs和臭氧浓度较高的主要原因. 兰州市是甘肃省政治经济中心,主体产业为石化与冶炼. 主城区地形上两山环绕南北,海拔约1520 m,河谷型地形地貌导致扩散条件差,区域内光照较强,极易发生光化学反应造成臭氧污染. 上世纪70、80年代,兰州西固区就发生过由高浓度VOCs引起的光化学烟雾现象[15]. 随着城市化进程的加快,兰州市城区环境形势愈发严峻,2019年兰州市轻度(含)以上污染中,以臭氧为首要污染物的天数占36.6%[16]. 近年来兰州大力整治石化行业VOCs排放,大气臭氧浓度却没有得到有效控制,2022年夏季臭氧平均质量浓度为151 µg·m−3,接近空气质量二级标准,可见兰州市大气VOCs污染已经转变为复合污染源排放型. 鉴于兰州市VOCs与O3污染来源和成因的复杂性,为实现兰州市整体O3污染治理与管控,进行大气VOCs与O3污染精细化特征分析及来源解析十分必要.
兰州大气组分超级监测站以臭氧污染机理研究为目的,实现兰州市城关区大气污染立体监测,构建“天、地、空”全方位立体管控体系,为研判臭氧污染演变趋势、预警决策、科学治理及区域联防联控提供技术支持. 本研究通过监测2021年兰州市大气O3、VOCs和其他大气组分,开展O3和VOCs污染特征研究,同时评估其臭氧生成潜势(ozone formation potential,OFP),利用正交矩阵因子模型(positive matrix factorization,PMF)对VOCs进行来源解析,为兰州市大气环境O3和VOCs污染管控提供数据基础和科学支撑.
基于超级站观测的兰州大气挥发性有机污染物特征及对臭氧形成的影响
Characteristics of atmospheric volatile organic compounds and their relationship with ozone concentration in Lanzhou based superstation observation
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摘要: 近年来随着兰州市经济社会的不断发展,臭氧(O3)和挥发性有机物(VOCs)污染现象日益严重,成为制约兰州市空气污染治理的重要瓶颈. 为合理有效地治理兰州市O3和VOCs污染,兰州大气组分超级监测站构建全方位立体管控体系,观测与分析2021年兰州市O3及其前体物VOCs的浓度分布特征,并利用正交矩阵因子分析(PMF)模型和臭氧生成潜势(OFP)分别分析了VOCs的来源及对臭氧生成的贡献. 兰州市O3浓度夏季最高,春季和秋季稍低,冬季最低,夏季光化学污染高发是导致O3含量较高的主要原因. VOCs污染集中在秋冬季,可能原因为冬季光化学反应减少、积累效应增加和燃煤排放增多使得VOCs含量高. 大气VOCs组成较为稳定,主要为含氧VOCs(OVOCs,35.7%)和烷烃(30.8%). 利用PMF源解析模型确定了当地VOCs的主要贡献源为机动车排放源(27.1%)、化石燃料燃烧源(23.8%)、化工工艺源(17.9%)、汽油挥发源(16.0%)、溶剂使用源(10.7%). 通过对比VOCs的OFP,发现乙烯、丙烯、甲苯对臭氧生成潜势贡献较大,在臭氧污染治理中应重点关注.Abstract: In recent years, with the economic and social development of Lanzhou City, ozone (O3) and volatile organic compounds (VOCs) pollution has become increasingly serious and restrict the control of air pollution in Lanzhou. In order to control the pollution of O3 and VOCs in Lanzhou reasonably and effectively, an all-dimensional control system was built in Lanzhou Atmospheric Component Super Monitoring Station to characterize of O3 and its precursors (VOCs) in 2021 in Lanzhou. Positive matrix factorization (PMF) model and ozone formation potential (OFP) were used to analyze the sources of VOCs and the contribution of VOCs to ozone formation respectively. In Lanzhou, O3 level was the highest in summer, slightly lower in spring and autumn, and the lowest in winter. The high incidence of photochemical pollution in summer was the main reason for the high O3 level. VOCs concentration was relative higher in autumn and winter, and the possible causes were the decrease of photochemical reaction, the increase of accumulation effect and coal-burning emission made high VOCs level. The components of VOCs were relatively stable, dominating by OVOCs (35.7%) and alkanes (30.8%). PMF model results showed that motor vehicle emission source (27.1%), fossil fuel combustion source (23.8%), chemical process source (17.9%), gasoline volatilization source (16.0%) and solvent use source (10.7%) were the main contributors to VOCs in this area. By comparing the OFP of VOCs, ethylene, propylene, and toluene played an important role in the ozone formation potential, which should be paid more attention during ozone pollution control.
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Key words:
- O3 /
- volatile organic compounds /
- ozone formation potential /
- source apportionment.
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[1] KOUNTOURIOTIS A, ALEIFERIS P G, CHARALAMBIDES A G. Numerical investigation of VOC levels in the area of petrol stations[J]. Science of the Total Environment, 2014, 470/471: 1205-1224. doi: 10.1016/j.scitotenv.2013.10.064 [2] SHI X R, ZHENG Y X, LEI Y, et al. Air quality benefits of achieving carbon neutrality in China[J]. Science of the Total Environment, 2021, 795: 148784. doi: 10.1016/j.scitotenv.2021.148784 [3] LI K, JACOB D J, LIAO H, et al. Ozone pollution in the North China Plain spreading into the late-winter haze season[J]. Proceedings of the National Academy of Sciences of the United States of America, 2021, 118(10): e2015797118. [4] LING Z H, GUO H, CHENG H R, et al. Sources of ambient volatile organic compounds and their contributions to photochemical ozone formation at a site in the Pearl River Delta, Southern China[J]. Environmental Pollution, 2011, 159(10): 2310-2319. doi: 10.1016/j.envpol.2011.05.001 [5] SHARMA S, SHARMA P, KHARE M. Photo-chemical transport modelling of tropospheric ozone: A review[J]. Atmospheric Environment, 2017, 159: 34-54. doi: 10.1016/j.atmosenv.2017.03.047 [6] YANG X, XUE L K, YAO L, et al. Carbonyl compounds at Mount Tai in the North China Plain: Characteristics, sources, and effects on ozone formation[J]. Atmospheric Research, 2017, 196: 53-61. doi: 10.1016/j.atmosres.2017.06.005 [7] Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for dinitrotoluenes [EB/OL]. [2023-04-13]. [8] International Agency for Research on Cancer (IARC), IARC monographs on the identification of carcinogenic hazards to humans [EB/OL]. [2023-04-13]. [9] 赵伟, 王硕, 庞晓蝶, 等. 2015—2021年陕西关中城市群臭氧污染变化趋势[J]. 环境科学, 2022, 43(12): 5399-5406. ZHAO W, WANG S, PANG X D, et al. Trends of ozone pollution in Guanzhong urban agglomeration from 2015 to 2021[J]. Environmental Science, 2022, 43(12): 5399-5406 (in Chinese).
[10] 周茜. 甘新地区城市大气中的挥发性有机物(VOCs)与颗粒物研究[D]. 兰州: 兰州大学. ZHOU X. Study on volatile organic compounds(VOCs) and particulate matter in urban atmosphere over the Gan-Xin region[D]. Lanzhou: Lanzhou University (in Chinese).
[11] 胡琳, 程路, 王琦, 等. 西安近地面臭氧浓度特征及关键气象因子分析[J]. 干旱区资源与环境, 2021, 35(6): 102-109. HU L, CHENG L, WANG Q, et al. Analysis of ozone concentration characteristics and key meteorological factors in Xi’an[J]. Journal of Arid Land Resources and Environment, 2021, 35(6): 102-109 (in Chinese).
[12] 刘松, 程燕, 李博伟, 等. 2013—2016年西安市臭氧时空变化特性与影响因素[J]. 地球环境学报, 2017, 8(6): 541-551. LIU S, CHENG Y, LI B W, et al. Characteristics of temporal and spatial variations of ozone and it’s influencing factor over Xi’an during 2013—2016[J]. Journal of Earth Environment, 2017, 8(6): 541-551 (in Chinese).
[13] 张瑞欣. 西部地区河谷地带煤化工工业城市臭氧污染成因及来源解析研究[D]. 兰州: 兰州大学, 2022. ZHANG R X. Causes and source apportionment of ozone pollution in coal chemical industrial city over the valley region of western China[D]. Lanzhou: Lanzhou University, 2022 (in Chinese).
[14] 曹泽磊. 西安市高新区臭氧及其前体物浓度变化特征研究[D]. 西安: 西安建筑科技大学, 2021. CAO Z L. Studies on concentration variation characteristics of ozone and its precursors in Xi’an High Technology District[D]. Xi'an: Xi'an University of Architecture and Technology, 2021 (in Chinese).
[15] 张远航, 邵可声, 唐孝炎, 等. 中国城市光化学烟雾污染研究[J]. 北京大学学报(自然科学版), 1998, 34(增刊1): 392-400. ZHANG Y H, SHAO K S, TANG X Y, et al. The study of urban photochemical smog pollution in China[J]. Acta Scicentiarum Naturalum Universitis Pekinesis, 1998, 34(Sup 1): 392-400 (in Chinese) .
[16] 张奇漪, 唐伟, 陈超, 等. 杭州市夏季臭氧污染特征及一次污染过程分析[J]. 环境科学与技术, 2023, 46(增刊1): 42-47. ZHANG Q Y, TANG W, CHEN C, et al. Analysis of characteristics of ozone pollution and a pollution process in summer in Hangzhou[J]. Environmental Science & Technology, 2023, 46(Sup 1): 42-47 (in Chinese).
[17] U. S. Environmental Protection Agency Office of Research and Development. EPA Positive Matrix Factorization (PMF) 5.0 fundamentals and user guide [EB/OL]. [2014-08-01]. [18] BUZCU B, FRASER M P. Source identification and apportionment of volatile organic compounds in Houston, TX[J]. Atmospheric Environment, 2006, 40(13): 2385-2400. doi: 10.1016/j.atmosenv.2005.12.020 [19] CARTER W P. Updated maximum incremental reactivity scale and hydrocarbon bin reactivities for regulatory applications[R]. California Air Resources Board Contract. 2009: 339. [20] 马秉吉. 兰州地区臭氧污染的影响因子及典型个例的数值模拟研究[D]. 兰州: 兰州大学, 2020. MA B J. Study on the influence factors of ozone pollution and the numerical simulation of typical cases in Lanzhou[D]. Lanzhou: Lanzhou University, 2020 (in Chinese).
[21] 罗诗露, 张艳利, 王新明. 广州城区臭氧污染高发期PAN浓度水平与变化特征[J]. 地球化学, 2022, 51(6): 625-635. LUO S L, ZHANG Y L, WANG X M. Ambient levels and variations of peroxyacetyl nitrate during periods with high incidence of ozone pollution in urban Guangzhou[J]. Geochimica, 2022, 51(6): 625-635 (in Chinese).
[22] 冯春莉, 饶永才, 李辉, 等. 徐州市臭氧污染特征及前体物协同控制策略分析[J]. 环境科学学报, 2023, 43(5): 325-332. FENG C L, RAO Y C, LI H, et al. Analysis of ozone pollution characteristics and precursor cooperative control strategy in Xuzhou City[J]. Acta Scientiae Circumstantiae, 2023, 43(5): 325-332 (in Chinese).
[23] LI J, ZHAI C Z, YU J Y, et al. Spatiotemporal variations of ambient volatile organic compounds and their sources in Chongqing, a mountainous megacity in China[J]. Science of the Total Environment, 2018, 627: 1442-1452. doi: 10.1016/j.scitotenv.2018.02.010 [24] 吴也正, 张鑫, 顾钧, 等. 苏州市初夏臭氧污染成因及年际变化[J]. 环境科学, 2024, 45(3): 1392-1401. WU Y Z, ZHANG X, GU J, et al. Ozone pollution in Suzhou during the early summertime: formation mechanism and interannual variation[J]. Environmental Science, 2024, 45(3): 1392-1401(in Chinese).
[25] 董昊, 王含月, 程龙, 等. 芜湖市臭氧污染特征与影响因素分析[J]. 环境化学, 2022, 41(7): 2364-2374. doi: 10.7524/j.issn.0254-6108.2021040103 DONG H, WANG H Y, CHENG L, et al. Pollution characteristics and influence factors of ozone in Wuhu City[J]. Environmental Chemistry, 2022, 41(7): 2364-2374 (in Chinese). doi: 10.7524/j.issn.0254-6108.2021040103
[26] WANG W N, van der A R, DING J Y, et al. Spatial and temporal changes of the ozone sensitivity in China based on satellite and ground-based observations[J]. Atmospheric Chemistry and Physics, 2021, 21(9): 7253-7269. doi: 10.5194/acp-21-7253-2021 [27] 张涛, 周炎, 岳玎利, 等. 珠三角典型地区挥发性有机化合物浓度水平及化学反应活性季节变化特征[J]. 环境污染与防治, 2021, 43(1): 1-7,13. ZHANG T, ZHOU Y, YUE D L, et al. Seasonal variation characteristics of concentration and chemical reactivity of VOCs in typical areas of the Pearl River Delta[J]. Environmental Pollution & Control, 2021, 43(1): 1-7,13 (in Chinese).
[28] 白宇婷. 区域大气挥发性有机物特征及来源解析: 以内蒙古自治区呼、包、巴三市为例[D]. 呼和浩特: 内蒙古大学, 2022. BAI Y T. Characterization of atmospherization of atmospheric volatile organic compounds and source analysis in the Hohhot-Baotou-Bayannur region[D]. Hohhot: Inner Mongolia University, 2022 (in Chinese).
[29] 李泱, 常莉敏, 吕沛诚, 等. 兰州市大气臭氧生成的敏感性分析及其前体物减排对策建议[J]. 环境科学学报, 2021, 41(5): 1628-1639. LI Y, CHANG L M, LÜ P C, et al. Sensitivity analysis of atmospheric ozone formation and its precursors emission reduction countermeasures in Lanzhou city[J]. Acta Scientiae Circumstantiae, 2021, 41(5): 1628-1639 (in Chinese).
[30] WANG H L, LOU S R, HUANG C, et al. Source profiles of volatile organic compounds from biomass burning in Yangtze River Delta, China[J]. Aerosol and Air Quality Research, 2014, 14(3): 818-828. doi: 10.4209/aaqr.2013.05.0174 [31] BORBON A, LOCOGE N, VEILLEROT M, et al. Characterisation of NMHCs in a French urban atmosphere: Overview of the main sources[J]. Science of the Total Environment, 2002, 292(3): 177-191. doi: 10.1016/S0048-9697(01)01106-8 [32] LIAO K J, HOU X T. Optimization of multipollutant air quality management strategies: A case study for five cities in the United States[J]. Journal of the Air & Waste Management Association (1995), 2015, 65(6): 732-742. [33] LIU Y, SHAO M, FU L L, et al. Source profiles of volatile organic compounds (VOCs) measured in China: Part I[J]. Atmospheric Environment, 2008, 42(25): 6247-6260. doi: 10.1016/j.atmosenv.2008.01.070 [34] 向丽, 田密, 杨季冬, 等. 重庆万州城区大气PM2.5中正构烷烃污染特征及来源分析[J]. 环境科学学报, 2016, 36(4): 1411-1418. XIANG L, TIAN M, YANG J D, et al. Pollution characteristics and source apportionment of n-alkanes in PM2.5 in Wanzhou[J]. Acta Scientiae Circumstantiae, 2016, 36(4): 1411-1418 (in Chinese).
[35] McCARTHY M C, AKLILU Y A, BROWN S G, et al. Source apportionment of volatile organic compounds measured in Edmonton, Alberta[J]. Atmospheric Environment, 2013, 81: 504-516. doi: 10.1016/j.atmosenv.2013.09.016 [36] 胡玲, 宋兴伟, 吴祺, 等. 基于PMF模型的南京市VOCs污染特征与来源解析研究[J]. 环境与发展, 2022, 34(4): 131-138,143. HU L, SONG X W, WU Q, et al. Research on the characteristics and source analysis of VOCs pollution in Nanjing City based on PMF model[J]. Environment and Development, 2022, 34(4): 131-138,143 (in Chinese).
[37] TAN J H, DUAN J C, CHAI F H, et al. Source apportionment of size segregated fine/ultrafine particle by PMF in Beijing[J]. Atmospheric Research, 2014, 139: 90-100. doi: 10.1016/j.atmosres.2014.01.007 [38] 陈浩, 曹磊, 高飞, 等. 西安市南郊夏季臭氧生成潜势与VOCs来源研究[J]. 环境科学与管理, 2021, 46(3): 48-52. CHEN H, CAO L, GAO F, et al. Analysis of ozone generation potential and VOCs sources in southern suburb of Xi’an in summer[J]. Environmental Science and Management, 2021, 46(3): 48-52 (in Chinese).
[39] BARLETTA B, MEINARDI S, SIMPSON I J, et al. Ambient mixing ratios of nonmethane hydrocarbons (NMHCs) in two major urban centers of the Pearl River Delta (PRD) region: Guangzhou and Dongguan[J]. Atmospheric Environment, 2008, 42(18): 4393-4408. doi: 10.1016/j.atmosenv.2008.01.028 [40] DUAN J C, TAN J H, YANG L, et al. Concentration, sources and ozone formation potential of volatile organic compounds (VOCs) during ozone episode in Beijing[J]. Atmospheric Research, 2008, 88(1): 25-35. doi: 10.1016/j.atmosres.2007.09.004 [41] 曹函玉, 潘月鹏, 王辉, 等. 2008—2010年北京城区大气BTEX的浓度水平及其O3生成潜势[J]. 环境科学, 2013, 34(6): 2065-2070. CAO H Y, PAN Y P, WANG H, et al. Concentrations and ozone formation potentials of BTEX during 2008-2010 in urban Beijing, China[J]. Environmental Science, 2013, 34(6): 2065-2070 (in Chinese).
[42] WANG G, CHENG S Y, WEI W, et al. Characteristics and source apportionment of VOCs in the suburban area of Beijing, China[J]. Atmospheric Pollution Research, 2016, 7(4): 711-724. doi: 10.1016/j.apr.2016.03.006 [43] 张超, 林伟立, 韩婷婷, 等. 北京城区大气苯系物变化特征及其环境意义[J]. 环境化学, 2022, 41(2): 460-469. doi: 10.7524/j.issn.0254-6108.2020092203 ZHANG C, LIN W L, HAN T T, et al. Exploring the variations in ambient BTEX at urban Beijing and its environmental implications[J]. Environmental Chemistry, 2022, 41(2): 460-469 (in Chinese). doi: 10.7524/j.issn.0254-6108.2020092203
[44] HUI L R, LIU X G, TAN Q W, et al. Characteristics, source apportionment and contribution of VOCs to ozone formation in Wuhan, Central China[J]. Atmospheric Environment, 2018, 192: 55-71. doi: 10.1016/j.atmosenv.2018.08.042