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Air Pollution

Air Pollution. Composition of the Atmosphere. Permanent gases (constant proportion in the atmosphere) 99.999 % of atmospheric mass Nitrogen(78%), Oxygen(21%) Argon, Neon, Helium, Krypton, Xenon, Hydrogen Variable gases (small percentage, but impact the behavior of the atmosphere)

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Air Pollution

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  1. Air Pollution

  2. Composition of the Atmosphere • Permanent gases (constant proportion in the atmosphere) • 99.999 % of atmospheric mass • Nitrogen(78%), Oxygen(21%) • Argon, Neon, Helium, Krypton, Xenon, Hydrogen • Variable gases (small percentage, but impact the behavior of the atmosphere) • Water Vapor, Carbon Dioxide, Ozone, Methane • SO2, NOx, CO, VOC • Particulate matter (aerosol)

  3. Troposphere(對流層) • 對流層是大氣中最低的一層。 • 高度每增加100公尺，氣溫平均下降約0.65℃。 • 對流層的厚度大約9-16km，由赤道向兩極減少，在同一緯度，對流層夏季較厚，冬季較薄。 • 雖然對流層的厚度不及整個大氣層厚度的1%，但是由於地球引力的作用，這一層卻集中了大氣3/4的質量和幾乎全部的水氣。 • 空氣通過對流和亂流運動，使近地面的熱量、水氣、質量等易於向上輸送，在垂直向得以混合，也因此雲、霧、雨、雪等主要大氣現象都出現在此層。 • 因為人類主要在此層活動，空氣污染物的排放、傳輸和去除也大都發生在此層。 • 在對流層的上方，界於對流層和平流層間，有一厚度為數百米到一兩公里的過度層，稱為對流層頂(tropopause)。

  4. Stratosphere(平流層) • 自對流層頂到50km左右為平流層。(比對流層厚) • 在平流層的下層隨著高度增加溫度保持不變或略有上升，大約到30km以上溫度會隨著高度顯著的增加，在50km左右會達到270K，平流層內此種溫度變化與臭氧吸收紫外線(UV)有密切關係，雖然臭氧在30km以上逐漸減少，但這裡紫外線的輻射較強，故溫度隨著高度增加而快速增加，造成顯著的暖層， • 平流層內氣流較為穩定，空氣的垂直混合作用較為微弱。 • 平流層中間有一臭氧層(ozone layer)，可以吸收有害的太陽紫外線輻射，是地球生態的保護，然而由於長期的氟氯碳化物(CFCs)累積，及其他由地面排放及高空飛行的飛機所排出的污染物，造成所謂的臭氧層破壞的問題，是目前環境科學家所關心的問題。 • 火山爆發所產生的微粒，會進入此層對太陽輻射產生影響， • 此層是許多長程飛行的高度，因此飛機所排出的污染物會在平流層擴展。

  5. Ozone Layer(臭氧層) • 在平流層中約20-25 km高，臭氧濃度最高，稱為臭氧層 。 • UV breaks down oxygenO2 + UV → O + O • Quickly combinesO2 + O → O3 • Which also can be broken downO3 + UV → O2 + O • 臭氧層可阻擋紫外線，避免人類被太陽曬傷、白內障、皮膚癌等。

  6. Air Pollutants (空氣污染物) 空氣污染物：指空氣中足以直接或間接妨害國民健康或生活環境之物質。 • 氣體(Gaseous): CO, SO2, NOx, VOC • 粒狀物(Particulate) : TSP (total suspended particulate), PM10, PM2.5,ultrafine particle • 原生性或一次污染物(Primary pollutants): emitted directly into the air. • 衍生性或二次污染物(Secondary pollutants): formed in the atmosphere by primary pollutants through reactions. (O3, H2SO4)

  7. Sources(污染源) • Stationary sources(固定污染源):工廠、發電廠等的煙囪、排氣口、營建工地 • Mobile sources(移動污染源):一邊移動，一邊排放污染物，如:道路車輛、火車、飛機、輪船

  8. 二氧化硫(Sulfur Dioxide, SO2) • 天然排放源如：火山、DMS(dimethylsulfide)和H2S的生物氧化等， • 大多數二氧化硫是人為產生的，主要包括：含硫燃料燃燒、焙燒金屬硫化物礦、化學製造過程產生的。 • 影響 • 人體健康 • 動植物 • 古蹟 • 反應產生硫酸鹽氣膠(酸雨、能見度、氣候、 …)

  9. 氮氧化物（Nitrogen Oxides, NOX） • 主要包括一氧化氮（NO）和二氧化氮（NO2 ）。 • 自然排放源包括：土壤和水中厭氧微生物的生物過程、閃電和火山爆發等。 • 人為排放主要來自高溫下燃燒，空氣中的N2和O2會反應產生NO 。主要來自火力發電廠、移動污染源、工業鍋爐、焚燒爐、 • 影響 • 人體健康 • 光化學污染 • 降低能見度:NO2呈黃棕色 • 植物 • 反應產生硝酸鹽氣膠(酸雨、能見度、氣候、 …)

  10. 一氧化碳(Carbon Monoxide, CO) • 含碳燃料在不完全燃燒的情況下產生的副產品 。 • 天然排放源包括: 森林火災、海洋生物活動等。 • 人為排放主要來自移動污染源，固定污染源排放量較少。 • 一氧化碳並不會對生態環境或財物造成危害，其主要的影響是人體暴露在高濃度的CO所產生的中毒事件。 • CO濃度太高會降低紅血球的帶氧能力，一般人吸入低濃度的一氧化碳時會感到頭痛、暈眩及疲倦。當吸入高濃度的一氧化碳時更會造成視力糢糊、失去協調能力，甚至死亡。 • 一氧化碳中毒常發生於通風不良的情況

  11. 揮發性有機物(Volatile Organic Compounds, VOCs ) • 通常指在常溫下其蒸氣壓大於0.01psi (0.0007atm, 70Pa)，且其沸點小於260℃的有機液體和固體。 • VOC包括碳氫化合物(hydrocarbon, HC)和其他有機化合物，通常含碳原子數小於12的有機物都為VOC。 • 甲烷在大氣中反應較慢，排除甲烷後其他大氣中的碳氫化合物稱為非甲烷碳氫化合物(non-methane hydrocarbon, NMHC)，NMHC代表參與大氣中光化學反應的碳氫化合物。 • 甲烷加上NMHC稱為總碳氫化合物(Total Hydrocarbon, THC)。

  12. 揮發性有機物 • 自然排放主要來自植物排放，少數則來自採煤區、油田天然氣及自然火災等 • 人為排放的揮發性有機物其來源相當龐雜，若以行業別觀點加以分類，則可分成工業、商業、住宅、車輛等 • 若依其排放特性加以區分，則可歸納為不完全燃燒、製程排放、油品揮發、溶劑使用及生物作用等五大類 • 影響 • 有些VOC具有惡臭，會造成心理的不適。 • 大氣環境中由於 VOCs 具有滲透、脂溶及揮發等特性，故極易經由皮膚接觸及呼吸系統而對人體造成危害，其侵害人體的對象主要為皮膚、呼吸系統、腎、肝、中樞神經系統等，且部分揮發性有機化合物已被列為致癌物，例如苯等有機溶劑。 • VOCs 均具化學活性，是臭氧的前趨物，在陽光照射下，會與氮氧化物反應， • 當VOCs濃度過高，容易在封閉性空間或作業環境中產生火災爆炸

  13. 大氣氣膠(aerosol) • 總懸浮微粒(TSP, total suspended particulate) • 懸浮微粒(PM10) • 細微粒(PM2.5) • 原生性氣膠 (primary aerosol) • 衍生性氣膠 (secondary aerosol)

  14. O3 Concentration (ppm) NO2 NO Time (hours) Photochemical Air Pollution primary pollutants + hν secondary pollutants VOC + NOx + hν O3 + PAN + HNO3 + particles (PAN = peroxyacetyl nitrate CH3C(O)OONO2 ) NO2 + hν (λ<430 nm)  NO + O O + O2 O3 *sole significant source of anthropogenic O3* NO + O3 NO2 + O2 (competing process) O3 forms when [NO] decreases

  15. 代表性的空氣污染問題 • 都市尺度:煙霧(smog) • 區域尺度:酸雨、衍生性氣膠、黃砂長程傳輸 • 全球尺度:臭氧層破壞、全球變遷

  16. Smog = Smoke + Fog • London Type • Los Angles Photochemical smog

  17. Verbal IconsThe image created by the words we choose to describe air pollution is very important. Smog itself is an invented icon which in the mode of Lewis Caroll combines Smoke and Fog. The London smog of 1952 that caused some 4000 deaths was called the killer smog. Think of the power of terms such as acid rain and ozone hole to conjure images.

  18. Thames below Westminster, (c.1871) Claude-Oscar Monet London smog • documented since the 13th century • widespread use of high-sulfur coal • caused by meteorological conditions • radiation inversion • cycle of condensation on aerosols at low T (night), and evaporation at higher T (day) • contained the pollutants in a small volume • high concentrations of SO2 and particles over London • fog droplets provided the aqueous medium for SO2 SO42- http://www.bbc.co.uk/paintingtheweather/csv/painting/thames.shtml

  19. Foggy Day in Decemeber 1952. http://en.wikipedia.org/wiki/File:Nelson%27s_Column_during_the_Great_Smog_of_1952.jpg

  20. Title: Smog wardens taking chemical readings, London, 1955.Caption: 'Two of London's smog wardens, called out for the first time yesterday, check the fog's thickness at Blackfriars.' Photograph by L Joseph.Credit: Daily Herald Archive/NMPFT/ Science & Society Picture Library Title: Testing for smog, London, 16 November 1954.'Like a walking laboratory, the smog detective in Civil Defence uniform goes out to seek information on the silent killer. Mr Harry Fleet, of Southwark Civil Defence, was out in last night's fog measuring the acidity, sulphur dioxide, hydrogen sulphide and carbon monoxide in the air. In his right hand is an aspirator which takes in the 'atmosphere'. Round his neck hangs a rack of test tubes and reagents to help identify the gases in the air.' Photograph by L Joseph.Credit: Daily Herald Archive/NMPFT/ Science & Society Picture Library http://www.nmsi.ac.uk/piclib/imagerecord.asp?id=META006890

  21. 'Pollution measures on the roof of the Meteorological Office A foggy Piccadilly partially lit by the light from a fruit seller's stall, 1952

  22. The London Smog Disaster of 1952.Days of toxic darkness. http://www.portfolio.mvm.ed.ac.uk/studentwebs/session4/27/greatsmog52.htm

  23. This 1963 photo shows a massive smog episode in New York City. (Photo: AP/Wide World Photo, EPA Journal Jan/Feb 1990.)

  24. Video • Killer fog http://www.youtube.com/watch?v=VJeTWGbLvzQ&feature=related

  25. Photochemical (LA) Smog • first observed in the 1940’s in Los Angeles, Calif. • occurred on hot days with bright sun • plant pathologists at UCR observed damage to plants in the LA basin area • in the lab: organics + NOx + sunlight  O3 + “other products” • also observed for auto exhaust: NOx + HC’s • VOC and NOx emissions are “trapped” by thermal inversions and irradiated by sunlight http://maquinna.vsb.bc.ca/students/bclung02/Div05/ect/smogp.htm

  26. Characteristic coloration for smog in California in the beige cloud bank behind Golden Gate Bridge. The brown coloration is due to the NOx in the photochemical smog. http://en.wikipedia.org/wiki/Smog

  27. Aerial View of Photochemical Smog Pollution Over Mexico City(22 December 2010) (Source: http://en.wikipedia.org/wiki/File:AerialViewPhotochemicalSmogMexicoCity_2.jpg)

  28. Brown Cloud over Denver, November 2002. http://ccc.atmos.colostate.edu/~hail/cool/polution/pages/denver_smog2.htm Photo by B. Burkhart

  29. Asian smog cloud threatens millions, says U.N. A man stands in front of the Bombay skyline overshadowed by a blue haze due to automobile pollution September 28, 2000. A 3-km thick cloud of pollution shrouding southern Asia is threatening the lives of millions of people in the region, according to a United Nations-sponsored study. REUTERS/File photo by Savita Kirloskar

  30. A plane monitors smog over Los Angeles, 1972.(Photo by Gene Daniels, EPA. Photo and caption: National Archives.)

  31. Table 1.2

  32. Control of Photochemical Smog :VOC and/or NOx?

  33. Video -- photochemical smog • History of air pollution: http://www.arb.ca.gov/videos/uaqtp/101.wmv • Clearing California Skies : http://www.arb.ca.gov/videos/clrcaskies.wmv • Classification of air pollutants http://www.arb.ca.gov/videos/uaqtp/103.wmv • Basic air pollution chemistry http://www.arb.ca.gov/videos/uaqtp/111.wmv

  34. Acid Deposition酸沉降

  35. Acid Deposition • recognized in the 18th century • 1872: Robert Angus Smith described 3 types of rain regions in England • coined the term acid rain • oxidation of SO2 and NO2 acids • wet deposition (濕沉降) and dry deposition(乾沉降) • deposition is both local and 1000+ km away from primary source http://www.epa.gov/airmarkets/acidrain/#what

  36. 乾沉降:在沒有降雨、雪、霧等情況下產生的沉降乾沉降:在沒有降雨、雪、霧等情況下產生的沉降 濕沉降(酸雨):降雨、雪、霧等情況下產生的沉降 http://www.soton.ac.uk/~engenvir/environment/air/acid.buildings.html

  37. Normal Rainfall = pH 5.6 (CO2+H2O->H2CO3) Acid Rain < 5.0

  38. Acid Deposition and Humans • Respiratory diseases • Toxic metal leaching • Damage to structures, especially containing calcium carbonate • Decreased visibility • Decreased productivity and profitability of fisheries, forests, and farms

  39. Acid Deposition and Aquatic Systems • Fish declines • Aluminum toxicity • Acid shock • Eutrophication(優養化) of lakes or estuary

  40. 台灣平均pH值、年降雨量(mm)、硫酸和硝酸根沉降量(kg/ha/yr)之等值線圖。(取材自Chen et al., 1996)

  41. 電腦模擬1990年和2010年東亞地區總酸沉降量

  42. 1990年硫酸鹽沉降來源和受點分析

  43. Secondary aerosol(衍生性氣膠)

  44. Atmospheric Particles (aerosol) • Armospheric particles come in many sizes and shapes and can be made up of hundreds of different chemicals. • Some particles, known as primary particles are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires. • Others form in complicated reactions in the atmosphere of chemicals such as sulfur dioxides and nitrogen oxides that are emitted from power plants, industries and automobiles. These particles, known as secondary particles, make up most of the fine particle pollution in the country.

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