北京市含碳?xì)馊苣z污染特征及來(lái)源研究-優(yōu)博

1、作者姓名：段鳳魁論文題目：北京市含碳?xì)馊苣z污染特征及來(lái)源研究作者簡(jiǎn)介：段鳳魁，女，1973年4月出生，2001年9月師從清華大學(xué)賀克斌教授，于2005年7月獲得博士學(xué)位。中文摘要j 含碳?xì)馊苣z是當(dāng)今大氣科學(xué)領(lǐng)域的研究熱點(diǎn)，是我國(guó)區(qū)域性、復(fù)合型大氣污染的關(guān) 鍵物種，對(duì)人體健康、生態(tài)環(huán)境、氣候變化、能見(jiàn)度都能產(chǎn)生諸多不良影響。含碳?xì)馊?膠在細(xì)顆粒物PM2.5中約占20-60%,從總量上主要分為有機(jī)碳（OC）和元素碳（EC）（統(tǒng) 稱為碳質(zhì)組分）。OC包括數(shù)千種有機(jī)化合物單體，不同種類有機(jī)化合物可能包含了不同 的污染源信息。鑒于含碳?xì)馊苣z的復(fù)雜性和多樣性，尤其是在EC測(cè)定、有機(jī)化學(xué)組分提取和鑒別等方面

2、存在的困難，國(guó)際上在含碳?xì)馊苣z方面的研究與無(wú)機(jī)化學(xué)組分（如水 溶性離子、無(wú)機(jī)多元素等）相比還比較少，近十年來(lái)進(jìn)展不大，在我國(guó)相關(guān)研究起步較 晚。進(jìn)行城市含碳?xì)馊苣z污染特征、來(lái)源及形成機(jī)理等前沿問(wèn)題的探討，對(duì)有的放矢地 解決我國(guó)城市大氣復(fù)合型污染問(wèn)題具有十分重要的意義。本論文在長(zhǎng)期PM2.5化學(xué)物種采1樣的基礎(chǔ)上，從碳質(zhì)組分總量（OC&EC）、二次有機(jī)碳（SOC）、典型有機(jī)化學(xué)組分等三| 個(gè)層面出發(fā)，深入系統(tǒng)地探討了北京市含碳?xì)馊苣z污染特征及來(lái)源，所得研究成果可為“十一五”期間我國(guó)城市大氣污染防治提供數(shù)據(jù)支持和科學(xué)指導(dǎo)，并可為相關(guān)環(huán)境政策 的制訂提供參考。iij目前國(guó)內(nèi)對(duì)于含碳?xì)馊苣z的研究一般僅

3、僅從總量上加以分析，或者側(cè)重于某類有機(jī)化合物（如PAHs）的研究，而且研究對(duì)象大多以總懸浮顆粒物 TSP或可吸入顆粒物PM10 為主，對(duì)PM2.5中碳質(zhì)組分從總量到單體化合物的系統(tǒng)研究還比較欠缺。尤其是二次有機(jī)碳的污染特征及形成機(jī)理國(guó)內(nèi)尚無(wú)報(bào)道。本論文研究?jī)?nèi)容立足于碳質(zhì)組分總量ii（ OC&EC ）、二次有機(jī)碳、有機(jī)化合物單體三個(gè)層面，既能從整體上把握城市含碳?xì)馊躨膠的污染特征，又能兼顧其中的關(guān)鍵點(diǎn)，可為同類研究以及城市大氣污染防治工作提供 新的思路。 針對(duì)PM2.5樣品一般量少、難以重復(fù)的局限性，論文首先建立了基于固相萃取（SPE）ii技術(shù)的PM2.5中典型有機(jī)組分的樣品前處理方法和色譜分析

4、方法。正構(gòu)烷烴、PAHs和有機(jī)酸分別具有分布廣泛、致毒性、難以直接測(cè)定的特點(diǎn)，是PM2.5中的典型有機(jī)污染物。I論文通過(guò)自填SPE萃取柱、優(yōu)化分離富集條件，使正構(gòu)烷烴、PAHs和有機(jī)酸三類目標(biāo)| | 組分得到了完全分離，并提高了樣品處理效率和回收率；通過(guò)探索實(shí)驗(yàn)條件獲得了一元I和二元有機(jī)酸衍生化最佳條件，解決了 GC/MS方法測(cè)定強(qiáng)極性、低分子量二元酸的難點(diǎn)ii問(wèn)題。該方法在同類研究中具有應(yīng)用價(jià)值。在此基礎(chǔ)上，定量檢測(cè)了為期一年的PM2.5I!樣品中25種正構(gòu)烷烴（C10-C34）、16種美國(guó)EPA優(yōu)控PAHs和35種有機(jī)酸（二元酸！iiDiC2-DiC11和一元酸FC10-FC32）三大類重

5、要有機(jī)組分。通過(guò)長(zhǎng)期、連續(xù)PM2.5樣品采集和化學(xué)分析，獲得了北京市連續(xù)三年P(guān)M2.5、0C、|EC質(zhì)量濃度時(shí)間序列特征；分別以清華園、昌平、密云為城區(qū)、郊區(qū)和背景點(diǎn)，獲得了I不同功能區(qū)為期一年P(guān)M2.5中碳質(zhì)組分的質(zhì)量濃度對(duì)比結(jié)果。研究發(fā)現(xiàn)，碳質(zhì)組分OC、iiEC質(zhì)量濃度采暖期高于非采暖期，日均、周均、月均以及季均濃度與PM2.5及氣態(tài)污染物SO2呈大致同步變化趨勢(shì)，反映了不同季節(jié)燃煤貢獻(xiàn)的變化；三個(gè)站點(diǎn) OC/TC值以及iiTC/PM2.5比較接近，分別為80%和20%，揭示了北京地區(qū)PM2.5中碳質(zhì)組分化學(xué)組成相 對(duì)穩(wěn)定的特點(diǎn)。研究結(jié)果表明，2001年9月至2004年10月期間，各種污染

6、物年均值都ii有不同程度的下降，第三個(gè)采樣年較第一個(gè)采樣年OC、EC、PM2.5和SO2分別下降了 32%、 15%、10%和 50%，反映了此期間相關(guān)大氣污染控制措施實(shí)施的取得的效果。這些研究結(jié)果對(duì)于北京市“十一五”期間大氣污染控制措施的制定以及實(shí)施具有重要的參考價(jià)值。!通過(guò)重要時(shí)段OC、EC的實(shí)時(shí)監(jiān)測(cè)，發(fā)現(xiàn)了不同季節(jié) OC/EC比值的頻數(shù)分布規(guī)律、！ii碳質(zhì)組分質(zhì)量濃度逐時(shí)、逐日變化規(guī)律，并對(duì)北京市城區(qū)和郊區(qū)二次有機(jī)碳SOC的來(lái)源和形成機(jī)理進(jìn)行了初步推斷。研究表明，碳質(zhì)組分濃度極大值出現(xiàn)在上午7:00前后和晚ii上20:00前后兩個(gè)時(shí)間段，濃度極小值出現(xiàn)在下午14:00前后，反映了機(jī)動(dòng)車排

7、放和邊界 層氣象條件的協(xié)同影響。研究發(fā)現(xiàn)不同季節(jié) OC/EC比值頻數(shù)分布呈不同特征，即：采暖 期、非采暖期分別呈單峰正態(tài)分布和雙峰分布。這種差異反映了燃煤源與二次有機(jī)碳的 相對(duì)貢獻(xiàn)隨季節(jié)而變化的特征。在此基礎(chǔ)上，進(jìn)一步對(duì)北京市城區(qū)SOC的來(lái)源和形成機(jī)理進(jìn)行了初步推斷，所得結(jié)論得到了國(guó)際同行的積極肯定。這些研究結(jié)果對(duì)于北京市2008 年奧運(yùn)會(huì)舉辦期間大氣污染物及其來(lái)源的監(jiān)控具有重要的實(shí)際應(yīng)用價(jià)值。i定量解析了為期一年正構(gòu)烷烴、PAHs和有機(jī)酸三大類典型有機(jī)組分的污染特征。研i究發(fā)現(xiàn)，正構(gòu)烷烴奇數(shù)碳優(yōu)勢(shì)明顯，采暖期、非采暖期碳數(shù)分別呈雙峰型（C21、C29）ii和單峰型（C29）分布，質(zhì)量總濃度冬

8、季高于其它季節(jié)； PAHs碳數(shù)分布采暖期以4環(huán)為主，非采暖期以5、6環(huán)為主；一元有機(jī)酸偶數(shù)碳優(yōu)勢(shì)明顯， C16、C18是主峰碳；二元- 酸以草酸、丙二酸為主，夏季濃度高于其它季節(jié)。在此基礎(chǔ)上，應(yīng)用特征參數(shù)法和主成II分分析法（PCA）對(duì)三大類典型有機(jī)組分的污染源進(jìn)行定性/半定量識(shí)別。結(jié)果表明，燃-煤、高等植物蠟排放是正構(gòu)烷烴兩大主要污染源；燃煤、機(jī)動(dòng)車排放和油品揮發(fā)是PAHsI的主要污染源；油煙、高等植物蠟、二次轉(zhuǎn)化是有機(jī)酸的主要來(lái)源。上述研究結(jié)果將為評(píng)估不同季節(jié)人為源與自然源對(duì)有機(jī)氣溶膠的貢獻(xiàn)并進(jìn)而制定相應(yīng)控制措施提供可靠依ii據(jù)。|建立了北京市含碳?xì)馊苣z化學(xué)組成質(zhì)量平衡，解析了 EC、一次

9、0C（POC）、SOC質(zhì)量濃度比的關(guān)系（1: 2: 2），揭示了有機(jī)氣溶膠二次轉(zhuǎn)化的重要性；0C被正構(gòu)烷烴、: :PAHs和有機(jī)酸三類組分定量解析的部分僅為10%。這對(duì)于深入認(rèn)識(shí)我國(guó)城市含碳?xì)馊苣z化學(xué)組成的復(fù)雜性具有重要科學(xué)意義，并可為其中難以提取和難以鑒別有機(jī)成分的后續(xù)研究提供重要的數(shù)據(jù)支持。Ii關(guān)鍵詞：OC/EC;二次有機(jī)碳；多環(huán)芳烴;有機(jī)酸；主成分分析法The Characteristics and Sources ofCarbon aceous Aerosols in Beiji ngDuan Fen gkuiABSTRACTCarbon aceous aerosol is the h

10、ot research issue in the curre nt atmospheric field, which cRn produce negative effects on human health, ecosystem, climate change and visibility, and is theIkey component of the regional and complex pollution in China. Carbonaceouscomponents in cludi ng orga nic carb on (OC) and eleme ntal carb on

11、(EC), acco unts for 20-60% of PM2.5 in urba n area. OC contains thousa nds of orga nic compo un ds, and differe nt category of orga nics maybe related to differe nt polluti on sources. Because of the complexity comp onents of OC, the difficulties of EC measurement and organic compounds extraction an

12、d identification, the studies for carb on aceous aerosol are less tha n those for sulfate aerosol, nitrate aerosol and other inorganic aerosols, and few progresses has bee n made for the past decade. In China, carry out the studies of carb on aceous aerosol, i nclud ing the chemical characteristics,

13、 sources and formation mechanism, will be of important significance for control the complex air pollution in:urban areas. Based on the Iong-term chemical species sampling of PM5, this work presents aii:comprehe nsive discussi on of the chemical characteristics and sources of carb on aceous aerosol f

14、rom three aspects: the total of carb on aceousspecies (OC&EC), sec on dary orga nic carb onii；:(SOC) and the typical orga nic compo un ds. The results will provide data supports and scie nce guide to the urban air pollution control during the eleventh five-year project in China, and canii；:also be t

15、he reference for the formulation of related environmental policies.:In Chi na, the former studies usually focused either on the total of carb on aceous aerosol, brii；:on some certa in category of orga nics such as PAHs. Additi on al, most of those studies;:concentrated on the total suspended particl

16、es (TSP) and PM10 samples, and few is related toii:PM2.5. Especially, there is no report about the characteristics and formation of SOC. This work;:bas ing on three aspects, i.e., OC&EC, SOC and in dividual orga nic compo un ds, prese nts both:IIthe total characteristics and the key point of carb on

17、 aceousaerosol, which will provide new1Iideas for the congener studies.I-It is necessary to build the efficient method for sample treatment because of the limited|qua ntity of PM2.5 sample. In this study, preparati on method based on solid phaseextract ionI-(SPE) and an alytical method using GC/MS w

18、ere developed for three typical orga nic species iniPM2.5. Alka nes, PAHs and orga nic acids are three typical orga nic polluta nts characterized byI-ubiquitous existenee, toxicity and difficulty of direct measurement, respectively. Optimaliiparameters for extract ion, separati on and derivati on we

19、re obta ined based on con diti onexperiments. By SPE method, the efficiency for sample preparation has been improved. TheOptimal derivation temperature and time for organic acid were obtained, and therefore, polar1 : and low molecular weight dicarboxylic acids can be determined by GC/MS method. This

20、method can be used in similar studies. Total 75 organic compounds were quantitativelydetermined including 25 n-alkanes (C10-C34), 16 PAHs (US EPA priority control) and 35 orga nic acids (C10-C32 for fatty acid and C2-C11 for dicarboxylic acid).On basis of the Ion g-term, con ti nu ous sampli ng and

21、chemical measureme nts, time series I and characteristics of PM2.5, OC and EC concentrations for 3 years were obtained.Comparisons between urban, rural and background site, i.e., Tsinghua University, Changping and Miyun, respectively, for 1 year were presented. The concentration of OC and EC showed:

22、 : obviously seas onal variati on, i.e., high in heati ng seas on tha n in non-heati ng seas on, meaning Tthe contribution variation of coal burning in Beijing. The ratios of OC/TC and TC/PM 2.5 wereI-similar at three sites, i.e., 80% and 20%, respectively, indicating the relative stabilizationfor-I

23、Icarb on aceous compositi on. Carbon aceous species varied synchrono usly with the ambie ntI:pollutants such as SO and PM2.5 for their daily, weekly, monthly and seasonal concentrations.During Sep. 2001 through Oct. 2004, it was show n that the polluta nts decreased in differe ntextent, 32%, 15%, 10

24、% and 50% for OC, EC, PM 2.5 and SO2, respectively. These results will be helpful for the enaction and application of the air pollution control measuresduring theIieleve nth five-year project.:-Characteristics of OC/EC frequency distribution, hourly and weekly concentration i:variation have been ana

25、lyzed based on the real time monitoring for OC and EC in this study.The real time monitoring of OC and EC indicated the obvious hourly variation. There were two11concentration peaks for OC and EC appearing at 7:00 a.m. and 20:00 p.m., and one lowest value appeared at 14:00. It reflected the comb in

26、ati on effects of both vehicle emissi on and the meteorological conditions. The distributions of OC/EC ratio frequency during non-heating seas on and heati ng seas on were differe nt, prese nting no rmal and bi-peak mode, respectively.-The latter can be ascribed to both the in creased coal bur ning

27、and the formatio n of sec on daryorga nic aerosols in win ter. Above results will be of applicatio n value for the atmospheric pollutants monitoring during the summer Olympic Games in 2008 in Beijing.The chemical characteristics of n-alkanes, PAHs and organic acid presented obvious:seas onv ariatio

28、ns. The n-alka nes were characterized by the odd nu mber predo minant, which-Iprese nted bi-peak(C21 C29) and sin gle-peak (C29) modes for heat ing and non-heat ing seas on, respectively. The predo minant PAHs in heat ing seas on were the 4 rings compo un ds, which-Iwere mainly con tributed by coal

29、burning. However, i n non-heati ng seas on, 5 and 6 rings compo unds were the predo minant PAHs, which usually come from vehicles emissi on. For fatty-I acid, the eve n nu mber carb on such C16 and C18 were the major species. The Prin ciple-Comp onent An alysis method (PCA) was used to ide ntify the

30、 main sources of those species.-IResults showed that coal bur ning and pla nt wax were the two major emissi on sources forialkanes; coal burning and vehicles emission were the major sources of PAHs. For organic acid, the mass concen tratio ns prese nted weak seas onal variati on, in dicati ng that their sources may be:of few relations with fossil fuels. T