北京城区亚微米气溶胶特征及其有机气溶胶的来源解析

发布时间：2018-02-03 15:16

  本文关键词： 高分辨率飞行时间气溶胶质谱仪 亚微米气溶胶 化学组成 后向轨迹 有机物来源解析　出处：《西南大学》2017年博士论文　论文类型：学位论文

【摘要】：北京作为中国的政治、经济和文化中心,近年来遭遇了严重的细颗粒物污染。随着北京及其周边地区经济的迅速发展,工业化和城市化进程的不断推进,能源消耗和机动车保有量也出现了持续的增长,导致空气质量不断恶化,大气细颗粒处于高浓度水平,重霾污染频繁发生。亚微米颗粒物是细颗粒物的重要组成部分,具有比表面积大、大气寿命长和光散射效率高等特征,对大气水平能见度具有重要影响。因此,系统研究亚微米气溶胶的特征及其有机气溶胶的来源,有助于深入了解亚微米颗粒物在大气中的环境效应。本研究站点位于北京中国科学院大气物理研究所325 m气象观测塔院内(东经116.37o,北纬39.97o)进行,利用高分辨率飞行时间气溶胶质谱仪(HR-ToF-AMS)、颗粒物快速捕集系统(RCFP-IC)和黑碳仪(BC)(MAAP-5012)等观测仪器于2015年8月~2016年8月对北京城区亚微米气溶胶进行了高时间分辨率的观测研究。通过对观测资料整理和分析研究,归纳了北京城区不同季节亚微米气溶胶浓度变化、化学成分组成、日变化和酸度变化特征;利用HYSPLIT4.9后向轨迹模式分析了气团传输对北京城区亚微米气溶胶的影响;评估了2015年抗战纪念活动阅兵期间污染减排措施对亚微米气溶胶的影响;研究了春节除夕夜烟花爆竹燃放对细颗粒物浓度及其水溶性离子组分的影响。通过对HR-ToF-AMS高分辨率质谱数据分析得到不同季节有机气溶胶(Organic aerosol,OA)中的元素比例和多环芳烃;利用PMF模型对HR-ToF-AMS高分辨率的OA质谱数据和硝酸盐质谱数据进行耦合解析,识别出了各个季节有机气溶胶的主要来源及贡献以及分离出有机硝酸盐和无机硝酸盐。主要研究结果如下:(1)北京城区亚微米气溶胶的春、夏、秋和冬季的平均浓度分别为44.1±49.5、31.8±21.1、46.4±58.0和61.7±71.6μg?m-3,可知冬季空气质量最差,夏季最好,春季和秋季污染较冬季轻。春、夏、秋和冬季有机物对pm1的贡献始终为最高,分别为40%、41%、50%和52%。无机组分中,夏季硫酸盐、硝酸盐和铵盐对pm1贡献分别为20%、17%和13%;春季和秋季硝酸盐对pm1的贡献比例稍微高于硫酸盐;而夏季和冬季,硫酸盐对pm1的贡献比例高于硝酸盐。由于北京及其周边地区冬季燃煤,硫酸盐对pm1的贡献达到了18%;夏季光化学反应强烈,气态前体物向颗粒物的转化加快,再加之相对湿度大,更有利于液相反应,因此夏季硫酸盐对pm1的贡献比例达到了20%。秋季硫酸盐和硝酸盐对pm1的贡献达到了15%和16%;四季铵盐贡献比例范围为7%~13%,bc贡献比例范围分别为8%~11%;氯盐对pm1的贡献比例较高的季节出现在春季和冬季,这与北京地区春季的沙尘和冬季的燃煤有关。(2)随着季节变化,pm1中各组分的日变化出现一定的差异。pm1中有机物在中午(11:00-12:00)和晚上(19:00-22:00)用餐时段出现两个明显峰值,但晚间峰值明显高于中午。春、夏、秋和冬季有机物午间和晚间峰值分别为16.7和22.5、12.7和14.1、20.1和30.5、25.6和37.5μg?m-3;由于北京城区夜间允许重型和轻型柴油车通过,bc日变化呈现出夜间浓度高于白天;春、夏、秋硝酸盐在上午(8:00-9:00)出现峰值,而冬季则是在上午10:00后呈现缓慢增加。春、夏、秋、冬季硫酸盐在午后15:00出现峰值。(3)污染天,oa对pm1的贡献比例降低,而二次无机气溶胶(secondaryinorganicaerosol,sia)(硫酸盐+硝酸盐+铵盐)贡献比例增加,尤其在重污染过程增长最快。不同季节的氧化性有机气溶胶(ooa,包括lv-ooa和sv-ooa,其中lv-ooa为低挥发的氧化性有机气溶胶,sv-ooa为半挥发的氧化性有机气溶胶)是oa的主要贡献组分。不同污染程度下,生物质燃烧气溶胶(bboa)和燃煤有机气溶胶(ccoa)贡献比例较稳定,而不同季节不同污染程度的烹饪有机气溶胶(coa)和碳氢有机气溶胶(hoa)变化差异很大。(4)ams和rcfp-ic两组系统同期对亚微米气溶胶中氯盐、硝酸盐、硫酸盐和铵盐监测对比表明,二者对观测的上述组分在不同季节都呈现一致的变化趋势。春季ams观测的氯盐,硝酸盐和硫酸盐浓度都低于rcfp-ic。夏、冬季ams观测的硝酸盐,硫酸盐浓度高于rcfp-ic;春、夏、秋、冬季ams观测的铵盐浓度都低于rcfp-ic。(5)通过ams的测定的nh4+(measured)与nh4+(predicted)的比值分析发现春、夏、秋、冬季大气中的亚微米气溶胶呈现不同程度的酸性,春夏秋季的斜率分别为0.88、0.95和0.76,说明气溶胶呈现出弱酸性;而在冬季,斜率值最低,为0.69,气溶胶呈较强的酸性。(6)通过后向轨迹聚类分析表明,不同季节远距离传输对北京地区大气污染有着不同的影响,春、冬季气团轨迹来向多样化,气团轨迹传输方向多于夏、秋季节,而在秋、冬季节,气团来向基本整体以西北和西南方向为主。来自南部气团携带有高浓度亚微米气溶胶浓度,其组成主要以二次无机和有机组分为主,而北部气团中亚微米气溶胶浓度最低,其二次无机组分的贡献明显低于南部气团。(7)典型个例事件分析结果表明,抗战纪念活动阅兵期间(2015年8月20日~2015年9月3日),北京城区pm2.5和pm1平均浓度为13.5和12μg?m-3,有机物对pm1贡献超过60%,与减排前期(2015年8月12日~2015年8月19日)相比,pm2.5和pm1分别下降了74.7%和72.2%。减排后期(2015年9月4日~2015年9月10日),随着污染减排措施的取消,颗粒物浓度出现反弹,pm2.5和pm1的平均浓度达到了27和31μg?m-3,硫酸盐和硝酸盐比例明显提高。(8)春节除夕夜烟花爆竹燃放(2月7日20:00-2月8日8:00)导致pm10、pm2.5和pm1的平均浓度达到589、414和318μg?m-3,pm2.5/pm10的比例为0.70,表明细颗粒物是主要贡献。pm2.5和pm1的twsi质量浓度分别为277和146μg?m-3,相应的贡献比例分别为46%和66.8%。pm2.5中k+、cl-和so42-的平均浓度为101、51和101μg?m-3,对总水溶性离子(twsi)的贡献分别为36%、18%和38%;pm1中k+、cl-和so42-的平均浓度为39、34和55μg?m-3,对twsi的贡献分别为25%、22%和38%。(9)利用pmf模型对不同季节北京亚微米气溶胶中有机物和硝酸盐的高分辨率质谱(highresolutionmassspectra,hrms)数据耦合进行深入解析发现,春、夏、秋和冬季都有相同的5种组分,分别是:低挥发的氧化性有机气溶胶(lv-ooa)、半挥发的氧化性有机气溶胶(sv-ooa)、烹饪源排放的烹饪有机气溶胶(coa)、交通源排放的碳氢有机气溶胶(hoa)和无机硝酸盐气溶胶(nia)。在秋季和冬季,由于受到生物质燃烧和燃煤取暖的影响,oa被解析出了生物质燃烧气溶胶(bboa)和燃煤有机气溶胶(ccoa)。在春季,lv-ooa、sv-ooa、coa和hoa四种组分对oa的贡献分别为29%、34%、17和20%;在夏季,四种组分对oa的贡献分别为47%、12%、22%和19%;在秋季,四种组分对oa的贡献分别为43%、12%、18%和11%;在冬季,四种组分对oa的贡献分别为16%、22%、13%和25%。由于秋季生物质燃烧和冬季燃煤的影响,bboa和ccoa对oa的贡献分别为16%和24%。(10)通过对hr-tof-ams的hrms数据分析得到不同季节亚微米有机气溶胶中多环芳烃(polycyclicaromatichydrocarbons,pahs)浓度,结果表明,夏季pahs浓度最低(0.01±0.004μg?m-3),冬季最高(0.22±0.24μg?m-3),春季和秋季节分别为0.03±0.03和0.04±0.01μg?m-3。冬季的pahs日变化浓度高于其它三个季节且夜间浓度高于白天。(11)通过nox+(no+和no2+)离子碎片在nia和oa组分质谱中的占比,结合相应的计算公式可以直接计算不同季节的有机硝酸盐和无机硝酸盐,结果表明,有机硝酸盐季节变化为:冬季(2.5±2.3μg?m-3)秋季(0.8±1.2μg?m-3)夏季(0.7±0.2μg?m-3)春季(0.6±0.5μg?m-3);无机硝酸盐的季节变化为:冬季(7.6±8.2μg?m-3)秋季(6.8±11.0μg?m-3)夏季(6.1±5.8μg?m-3)春季(4.1±5.7μg?m-3)。有机硝酸盐日变化呈现夏季白天浓度高于夜间,春、秋和冬季浓度都呈现夜间浓度高于白天;无机硝酸盐日变化各季节变化各不相同。
[Abstract]:Beijing China as political, economic and cultural center, in recent years, suffered a fine particle pollution serious. With the rapid development of economy in Beijing and its surrounding areas, industrialization and city development, energy consumption and the amount of vehicle also has sustained growth, resulting in deteriorating air quality, atmospheric fine particles are the high level of concentration, heavy haze pollution occurred frequently. Submicron particle is an important part of fine particles, with a large surface area, long atmospheric lifetimes and light scattering characteristics of high efficiency, atmospheric horizontal visibility has important influence. Therefore, the source characteristics of submicron aerosols and organic aerosol. Helps to deepen the environmental effects of solution of submicron particles in the atmosphere. The study site is located in Beijing China Atmospheric Physics Research Institute 325 m meteorological observation in Tayuan (East By 116.37o, 39.97o, North) using high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), fast particle trapping system (RCFP-IC) and carbon black (BC) instrument (MAAP-5012) and other instruments in August 2015 ~2016 year in August in Beijing city of submicron aerosols were observed with high time resolution. Based on study on data collection and analysis, summarizes the seasonal changes of submicron aerosol concentration in Beijing City, chemical composition, diurnal variation and acidity change characteristics; using HYSPLIT4.9 back trajectory model of gas transmission group in Beijing city of submicron aerosols; evaluated the impact of the 2015 war memorial activities during the parade of Asian pollution reduction measures micron aerosol; on the spring Festival Eve fireworks effect of soluble ion component of water and concentration of fine particles on the HR-ToF-AMS score. High-resolution mass spectrometry data analysis in different seasons organic aerosol (Organic aerosol, OA) in the proportion of elements and PAHs; coupling analysis of the HR-ToF-AMS OA high resolution mass spectrometry data and nitrate MS data using the PMF model, to identify the main sources and the contribution of each season and isolate the organic aerosol nitrate and organic inorganic nitrate. The main results are as follows: (1) Beijing city of submicron aerosols in spring, summer, autumn and winter, the average concentration was 44.1 + 49.5,31.8 + 21.1,46.4 + 58 and 61.7 + 71.6 G? M-3, can know the worst winter air quality, the best in summer, spring and autumn than in winter and light pollution. Spring, summer, autumn and winter with organic matter on PM1 always is the highest, respectively 40%, 41%, 50% and 52%. units in summer, sulfate, nitrate and ammonium on the contribution of PM1 were 20%, 17% and 13%; the spring and autumn nitrate Contribution ratio of acid salt of PM1 is slightly higher than that of sulfate; and summer and winter, the contribution proportion of PM1 was higher than that of sulfate nitrate. As winter coal in Beijing and its surrounding areas, the contribution of sulfate on PM1 reached 18%; summer photochemical reaction, before transforming the objects to gaseous particles accelerated, coupled with the relative humidity larger, more conducive to the liquid phase reaction, so the contribution ratio of summer sulfate on PM1 reached 20%. in autumn with sulfate and nitrate of PM1 reached 15% and 16%; quaternary ammonium contribution ratio in the range of 7%~13%, BC proportion range were 8%~11%; chloride PM1 contribution of the higher proportion of the season in spring and in winter, and the Beijing area in spring and winter. The coal dust (2) with seasonal variation, diurnal variation of each component of some differences in organic matter in.Pm1 PM1 (11: 00-12:00) at noon and night (19:00-22:00) the dining hours there are two obvious peak, but the evening peak was significantly higher than at noon. Spring, summer, autumn and winter organic midday and evening peak were 16.7 and 22.5,12.7 and 14.1,20.1 and 30.5,25.6 and 37.5 G? M-3; because of Beijing city at night to allow heavy and light diesel engine by BC, showed the day changes the night was higher than in spring, summer, autumn day; nitrate (8:00-9:00) in the morning peak, while in winter it is 10:00 in the morning after a slow increase. Spring, summer, autumn, winter peak appeared at 15:00 in the afternoon. The sulfate (3) pollution days, proportion of the contribution of OA to PM1 decreased, while the two inorganic aerosol (secondaryinorganicaerosol, SIA) (nitrate + ammonium sulfate +) proportion increased, especially in the growth of heavy pollution in different seasons. The oxidation of organic aerosol (OOA, including lv-ooa and sv-ooa, where lv-ooa is the oxidation of the low volatile Machine aerosol, sv-ooa oxidation of semi volatile organic aerosol) is the main component of OA. With different degree of pollution, biomass burning aerosols (bboa) and coal organic aerosol (CCOA) contribution ratio is relatively stable, and different seasons and different pollution degree of cooking organic aerosol (COA) and hydrocarbon organic aerosol (HOA) the change is very different. (4) AMS and rcfp-ic two system over the same period of chloride, submicron aerosol nitrate and ammonium sulfate, shows that the monitoring results, the two group of the observation points in different seasons are presented the same trend in spring. AMS observation of chloride, nitrate and sulfate concentrations are lower than rcfp-ic. summer, AMS observation of nitrate sulfate concentration was higher than that of rcfp-ic; in winter, spring, summer, autumn and winter, ammonium AMS observations are less than rcfp-ic. (5) through the determination of AMS nh4+ (measured) and nh4+ (predicted) ratio analysis Find the spring, summer, autumn and winter in the atmosphere of the submicron aerosol showed different degrees of acidity, the slope of spring and autumn were 0.88,0.95 and 0.76, showing that the aerosol weak acid; while in winter, the slope was the lowest, 0.69, aerosol more acidic. (6) through back trajectory cluster analysis showed in different seasons, long-distance transmission has a different effect on the air pollution in Beijing area, spring, winter air mass trajectories to diversification, air mass trajectory propagation direction more than summer and autumn, and in autumn, winter, air to the basic overall to the northwest and southwest. From the southern air with high concentration of sub micron aerosol concentration, it is composed of two inorganic and organic components, while the north air mass the submicron aerosol concentration is lowest, the inorganic component contribution was significantly lower than that of the southern air. (7) the typical case analysis of events The results show that during the commemoration of the war Parade (August 20, 2015 ~2015 September 3rd), Beijing City PM2.5 and PM1 average concentration of 13.5 and 12 g? M-3, organic matter more than 60% contribution to PM1 reduction, and early (August 12, 2015 ~2015 August 19th), PM2.5 and PM1 were decreased by 74.7% and 72.2%. emission reduction period (September 4, 2015 ~2015 in September 10th), with the abolition of pollution reduction measures, particle concentration rebound, the average concentration of PM2.5 and PM1 reached 27 and 31 G? M-3, sulfate and nitrate increased significantly. (8) the Spring Festival New Year's Eve Fireworks (February 7th 20:00-2 month 8 days at 8:00) lead to PM10, the average concentration of PM2.5 and PM1 reached 589414 and 318 G? M-3, pm2.5/pm10 ratio was 0.70, showed that the mass concentration of TWSI fine particulate matter is the main contribution of.Pm2.5 and PM1 were 277 and 146 G? M-3, the corresponding contribution rates were 46% and 66.8%.pm2.5 In k+, the average concentration of cl- and so42- 101,51 and 101 G? M-3, the total water soluble ions (TWSI) contributions were 36%, 18% and 38%; PM1 k+, the average concentration of cl- and so42- 39,34 and 55 G? M-3, the contribution to TWSI was 25%, 22% and 38%. (9) PMF model using high resolution mass spectrometry of organic matter and nitrate in different seasons in Beijing submicron aerosols (highresolutionmassspectra, HRMS) data coupling in-depth analysis found that the spring, summer, autumn and winter are the same 5 components, namely: low volatile organic gas oxidation sol (lv-ooa), the oxidation of semi volatile organic aerosol (sv-ooa), cooking cooking organic aerosol source emission (COA), hydrocarbon organic aerosol traffic source emission (HOA) and inorganic nitrate aerosol (NIA). In the autumn and winter, due to biomass burning and burning coal-fired heating effect, OA the analysis of biomass fuel 鐑ф皵婧惰兌(bboa)鍜岀噧鐓ゆ湁鏈烘皵婧惰兌(ccoa).鍦ㄦ槬瀛，

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