上海城区二次气溶胶的形成:光化学氧化与液相反应对二次气溶胶形成的影响
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摘要
二次组分是大气细颗粒物中最重要的组成部分之一.本研究旨在探究上海城区大气气溶胶颗粒物中二次组分的贡献及其形成的主要影响因素.利用高分辨率飞行时间气溶胶质谱仪(HR-TOF-AMS)对上海城区春季及夏季的亚微米颗粒物(PM_1)进行实时的在线表征,发现有机物是PM_1中最主要的组成部分,占比为55%;其次是硫酸盐(24%)与硝酸盐(10%).进一步结合正交矩阵因子解析模型(PMF)对有机组分进行了来源解析.结果表明,一次有机气溶胶(POA)与二次有机气溶胶(SOA)分别占总有机物浓度的34%与66%; POA主要来自机动车源与餐饮源的贡献,且在春季和夏季对有机物的贡献趋于稳定.观测期间共观察到3个二次气溶胶显著生成的过程:其中,春季二次组分的显著增长过程以硫酸盐和老化的有机气溶胶在正午时段上升显著为主要特征,主要受光化学氧化过程的促进;夏季二次组分的显著生成过程主要是液相反应与光化学氧化共同促进的结果,如液相反应过程中,硝酸盐浓度与颗粒相水含量有较好的相关性(R~2=0. 72),而光化学氧化期间SOA浓度与大气氧化性(O_x)有较好的相关性.总体而言,二次组分是上海城市大气气溶胶颗粒物中最重要的组成部分,二次有机与无机组分在PM_1颗粒物中占比分别为35. 5%和43%,光化学氧化与液相反应对二次组分的形成有显著的促进作用.
Secondary species are one of the most important components of PM_1 particles. To investigate the contributions as well as the factors that affect the formation of the secondary aerosols,a high-resolution time-of-flight aerosol mass spectrometer(HR-TOF-AMS,AMS) was employed to characterize sub-micron particles(PM_1) during spring and summer in urban Shanghai. Organics were dominant in PM_1 particles and comprised around 55% of the total PM_1 mass concentration,followed by sulfate(24%) and nitrate(10%).Positive matrix factorization was further applied to explore the sources of the organics. It was found that primary and secondary organic aerosols accounted for around 34% and 66% of the total organics, respectively. Three episodes were observed during the measurements,where secondary species increased substantially. Increases of secondary species were represented by increases of sulfate and LV-OOA_1 in spring,especially during the noontime,thus indicating that their formation is promoted by photochemical oxidation;yet in summer,photochemical and aqueous chemistry together accelerate the formation of secondary species,as indicated by the good correlations between nitrate and aerosol liquid water as well as between SOA and O_x. Overall,we found that contributions from secondary organic and inorganic aerosols to total PM_1 particles were 35. 5% and 43%,respectively. This study highlights that the influence of photochemical and aqueous chemistry is significant in the promotion of secondary species formation in Shanghai.
Secondary species are one of the most important components of PM_1 particles. To investigate the contributions as well as the factors that affect the formation of the secondary aerosols,a high-resolution time-of-flight aerosol mass spectrometer(HR-TOF-AMS,AMS) was employed to characterize sub-micron particles(PM_1) during spring and summer in urban Shanghai. Organics were dominant in PM_1 particles and comprised around 55% of the total PM_1 mass concentration,followed by sulfate(24%) and nitrate(10%).Positive matrix factorization was further applied to explore the sources of the organics. It was found that primary and secondary organic aerosols accounted for around 34% and 66% of the total organics, respectively. Three episodes were observed during the measurements,where secondary species increased substantially. Increases of secondary species were represented by increases of sulfate and LV-OOA_1 in spring,especially during the noontime,thus indicating that their formation is promoted by photochemical oxidation;yet in summer,photochemical and aqueous chemistry together accelerate the formation of secondary species,as indicated by the good correlations between nitrate and aerosol liquid water as well as between SOA and O_x. Overall,we found that contributions from secondary organic and inorganic aerosols to total PM_1 particles were 35. 5% and 43%,respectively. This study highlights that the influence of photochemical and aqueous chemistry is significant in the promotion of secondary species formation in Shanghai.
引文
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[35] Hu W W,Hu M,Hu W,et al. Chemical composition,sources,and aging process of submicron aerosols in Beijing:contrast between summer and winter[J]. Journal of Geophysical Research,2016,121(4):1955-1977.
[36] Qin Y M,Li Y J,Wang H,et al. Particulate matter(PM)episodes at a suburban site in Hong Kong:evolution of PM characteristics and role of photochemistry in secondary aerosol formation[J]. Atmospheric Chemistry and Physics,2016,16(22):14131-14145.
[37] Pusede S E,Duffey K C,Shusterman A A,et al. On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol[J]. Atmospheric Chemistry and Physics,2016,16(4):2575-2596.
[38] Young D E,Kim H,Parworth C,et al. Influences of emission sources and meteorology on aerosol chemistry in a polluted urban environment:results from DISCOVER-AQ California[J].Atmospheric Chemistry and Physics,2016,16(8):5427-5451.
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[40] Wang Y,Zhuang G S,Zhang X Y,et al. The ion chemistry,seasonal cycle,and sources of PM2. 5and TSP aerosol in Shanghai[J]. Atmospheric Environment,2006,40(16):2935-2952.
[2] Chow J C,Watson J G,Kuhns H,et al. Source profiles for industrial,mobile,and area sources in the big bend regional aerosol visibility and observational study[J]. Chemosphere,2004,54(2):185-208.
[3] May A A,Nguyen N T,Presto A A,et al. Gas-and particlephase primary emissions from in-use,on-road gasoline and diesel vehicles[J]. Atmospheric Environment,2014,88:247-260.
[4] Cheng Z,Wang S,Fu X,et al. Impact of biomass burning on haze pollution in the Yangtze River delta,China:a case study in summer 2011[J]. Atmospheric Chemistry and Physics,2014,14(9):4573-4585.
[5]林瑜,叶芝祥,杨怀金,等.成都市中心城区大气PM1的污染特征及来源解析[J].中国环境科学,2017,37(9):3220-3226.Lin Y,Ye Z X,Yang H J,et al. Pollution level and source apportionment of atmospheric particles PM1in downtown area of Chengdu[J]. China Environmental Science,2017,37(9):3220-3226.
[6] Seinfeld J I. Atmospheric chemistry and physics:from air pollution to climate change[J]. Environment:Science and Policy for Sustainable Development,1998,40(7):26.
[7] Zhang Q,Jimenez J L,Canagaratna M R,et al. Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically-influenced Northern Hemisphere midlatitudes[J]. Geophysical Research Letters,2007,34(13):L13801.
[8] Hu W,Hu M,Hu W W,et al. Seasonal variations in high timeresolved chemical compositions, sources, and evolution of atmospheric submicron aerosols in the megacity Beijing[J].Atmospheric Chemistry and Physics,2017,17(16):9979-10000.
[9] Chapleski R C,Zhang Y F,Troya D,et al. Heterogeneous chemistry and reaction dynamics of the atmospheric oxidants,O3,NO3,and OH,on organic surfaces[J]. Chemical Society Reviews,2016,45(13):3731-3746.
[10] Tsigaridis K, Kanakidou M. Global modelling of secondary organic aerosol in the troposphere:a sensitivity analysis[J].Atmospheric Chemistry and Physics,2003,3(5):1849-1869.
[11] Guo S,Hu M,Guo Q F,et al. Primary sources and secondary formation of organic aerosols in Beijing, China[J].Environmental Science&Technology,2012,46(18):9846-9853.
[12] Li Y J, Sun Y L, Zhang Q, et al. Real-time chemical characterization of atmospheric particulate matter in China:a review[J]. Atmospheric Environment,2017,158:270-304.
[13] Feng J L,Li M,Zhang P,et al. Investigation of the sources and seasonal variations of secondary organic aerosols in PM2. 5in Shanghai with organic tracers[J]. Atmospheric Environment,2013,79:614-622.
[14] Zhou M,Qiao L P,Zhu S H,et al. Chemical characteristics of fine particles and their impact on visibility impairment in Shanghai based on a 1-year period observation[J]. Journal of Environmental Sciences,2016,48:151-160.
[15] Wang H L,Chen C H,Wang Q,et al. Chemical loss of volatile organic compounds and its impact on the source analysis through a two-year continuous measurement[J]. Atmospheric Environment,2013,80:488-498.
[16]宫照恒,薛莲,孙天乐,等.基于高分辨质谱在线观测的2011深圳大运会前后PM1化学组成与粒径分布[J].中国科学:化学,2013,43(3):363-372.Gong Z H,Xue L,Sun T L,et al. On-line measurement of PM1chemical composition and size distribution using a high-resolution aerosol mass spectrometer during 2011 Shenzhen Universiade[J]. Scientia Sinica Chimica,2013,43(3):363-372.
[17] Huang X F,He L Y,Xue L,et al. Highly time-resolved chemical characterization of atmospheric fine particles during2010 Shanghai World Expo[J]. Atmospheric Chemistry and Physics,2012,12(11):4897-4907.
[18] Hu W W,Hu M,Yuan B,et al. Insights on organic aerosol aging and the influence of coal combustion at a regional receptor site of Central Eastern China[J]. Atmospheric Chemistry and Physics,2013,13(19):10095-10112.
[19] Ulbrich I M,Canagaratna M R,Zhang Q,et al. Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data[J]. Atmospheric Chemistry and Physics,2009,9(9):2891-2918.
[20] Zhang Q,Jimenez J L,Canagaratna M R,et al. Understanding atmospheric organic aerosols via factor analysis of aerosol mass spectrometry:a review[J]. Analytical and Bioanalytical Chemistry,2011,401(10):3045-3067.
[21] Middlebrook A M,Bahreini R,Jimenez J L,et al. Evaluation of composition-dependent collection efficiencies for the aerodyne aerosol mass spectrometer using field data[J]. Aerosol Science and Technology,2012,46(3):258-271.
[22] Huang X F,Xue L,Tian X D,et al. Highly time-resolved carbonaceous aerosol characterization in Yangtze River Delta of China:Composition,mixing state and secondary formation[J].Atmospheric Environment,2013,64:200-207.
[23] Wang Q Z,Dong X Y,Fu J S,et al. Environmentally dependent dust chemistry of a super Asian dust storm in March 2010:observation and simulation[J]. Atmospheric Chemistry and Physics,2018,18(5):3505-3521.
[24]何瑶,黄汝锦,王启元,等.我国PM1浓度、化学组分及来源的时空分布[J].中国粉体技术,2017,23(3):1-10.He Y,Huang W J,Wang Q Y,et al. Temporal and spatial distribution of atmospheric PM1concentration,composition and source in China[J]. China Powder Science and Technology,2017,23(3):1-10.
[25] Behera S N, Sharma M. Investigating the potential role of ammonia in ion chemistry of fine particulate matter formation for an urban environment[J]. Science of the Total Environment,2010,408(17):3569-3575.
[26] Khoder M I. Atmospheric conversion of sulfur dioxide to particulate sulfate and nitrogen dioxide to particulate nitrate and gaseous nitric acid in an urban area[J]. Chemosphere,2002,49(6):675-684.
[27] Ohta S,Okita T. A chemical characterization of atmospheric aerosol in Sapporo[J]. Atmospheric Environment. Part A.General Topics,1990,24(4):815-822.
[28] Truex T J,Pierson W R,Mc Kee D E. Sulfate in diesel exhaust[J]. Environmental Science&Technology,1980,14(9):1118-1121.
[29] Zhang X Y,Wang Y Q,Zhang X C,et al. Carbonaceous aerosol composition over various regions of China during 2006[J].Journal of Geophysical Research,2008,113(D14):D14111,doi:10. 1029/2007JD009525.
[30] Quan J N,Zhang X S,Zhang Q,et al. Importance of sulfate emission to sulfur deposition at urban and rural sites in China[J]. Atmospheric Research,2008,89(3):283-288.
[31] Clegg S L,Brimblecombe P,Wexler A S. Thermodynamic model of the system H+NH4+-SO24--NO3--H2O at tropospheric temperatures[J]. The Journal of Physical Chemistry A,1998,102(12):2137-2154.
[32] Ravishankara A R. Heterogeneous and multiphase chemistry in the troposphere[J]. Science,1997,276(5315):1058-1065.
[33] Ng N L,Canagaratna M R,Jimenez J L,et al. Real-time methods for estimating organic component mass concentrations from aerosol mass spectrometer data[J]. Environmental Science&Technology,2011,45(3):910-916.
[34] Allan J D,Williams P I,Morgan W T,et al. Contributions from transport,solid fuel burning and cooking to primary organic aerosols in two UK cities[J]. Atmospheric Chemistry and Physics,2010,10(2):647-668.
[35] Hu W W,Hu M,Hu W,et al. Chemical composition,sources,and aging process of submicron aerosols in Beijing:contrast between summer and winter[J]. Journal of Geophysical Research,2016,121(4):1955-1977.
[36] Qin Y M,Li Y J,Wang H,et al. Particulate matter(PM)episodes at a suburban site in Hong Kong:evolution of PM characteristics and role of photochemistry in secondary aerosol formation[J]. Atmospheric Chemistry and Physics,2016,16(22):14131-14145.
[37] Pusede S E,Duffey K C,Shusterman A A,et al. On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol[J]. Atmospheric Chemistry and Physics,2016,16(4):2575-2596.
[38] Young D E,Kim H,Parworth C,et al. Influences of emission sources and meteorology on aerosol chemistry in a polluted urban environment:results from DISCOVER-AQ California[J].Atmospheric Chemistry and Physics,2016,16(8):5427-5451.
[39] Lin P,Hu M,Deng Z,et al. Seasonal and diurnal variations of organic carbon in PM2. 5in Beijing and the estimation of secondary organic carbon[J]. Journal of Geophysical Research,2009,114(D2):D00G11,doi:10. 1029/2008JD010902.
[40] Wang Y,Zhuang G S,Zhang X Y,et al. The ion chemistry,seasonal cycle,and sources of PM2. 5and TSP aerosol in Shanghai[J]. Atmospheric Environment,2006,40(16):2935-2952.