The Atmospheric Oxidation Capacity (6Th Lecture)
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hν 1 H2O O3 HO2 O3 O( D) OH HO2 H2O2 Air Pollution Control and Air Chemistry: The atmospheric oxidation capacity (6th lecture) Detlev Möller Chair for Atmospheric Chemistry and Air Pollution Control Faculty of Environmental Sciences and Process Engineering Brandenburg Technical University Cottbus, Germany Objectives: To describe the atmospheric chemical OxHy system being an redox cycle with the tendency to oxidize reduced trace substances such as sulphur, nitrogen and carbon. ¾ oxidants and OxHy redox cycle, ¾ ozone chemistry and radical formation, ¾ oxidative stress ¾ summer smog, ozone dynamic What does mean oxidation (or oxidising) capacity or potential? It is the ability of the atmosphere to oxidize trace substances. Most trace substances (emission) are entering the atmosphere in reduced from: → Sulphur(IV) SO Sulphur(-II) H2S, DMS 2 → Sulphur(VI) SO 2- Sulphur (IV) SO2 4 → Nitrogen(II) NO Nitrogen(-III) NH3 → Nitrogen(II) NO Nitrogen(I) N2O Nitrogen(II) NO → Nitrogen(V) HNO3 → Carbon(II) CO Carbon(-IV) CH4, NMVOC (RCH3) Carbon(II) CO → Carbon(IV) CO2 oxidation process Each oxidation step is combined with a reduction (redox process). In the atmosphere, most important oxidants are OxHx species establishing the redox cycles between water (H2O) and oxygen (O2) via active intermediates (radicals and peroxides). There is no general (mathematical) definition. Often it is idenfied with the OH radical concentration. We can not define it similar to the redox potential in aqueous solutions. red From kinetic point of view, Xi + OXj → + Products, we can ox design it as the free reaction energy (Gibb´s potential): Ptherm = ∑ΔRG j j ox and as the specific oxidation potential (rate): Pkin = ∑kOXj⎣⎡ j ⎦⎤ j All important HxOy components redox species formation/destruction name level - - -3 H2O H2O + e aquated electron - + H2O OH + H / OH + H water + + H (H3O ) - hydrogen ion (hydrogenium) -2 OH- OH + e- hydroxyl ion - - [O2 ] O2 + e oxide + - + H2O H2O – e / OH + H water anion OH O + H / H2O - H hydroxyl radical -1 - - HO2 HO2 + e hydroperoxide anion H2O2 OH + OH hydrogenperoxide - - O2 O2 + e hyperoxide anion HO2 O2 + H / O + OH hydroperoxoradical - - O3 O3 + e ozonide anion -1/±0 HO3 OH + O2 ozonide - - HO4 O3 + OH ozone acid anion (hypothetical) H2O4 HO2 + HO2 / 2 OH + O2 ozone acid (hypothetical) H - hydrogen O - oxygen, atomar ±0 O2 O + O oxygen, molecular O3 O + O2 ozone redox states of oxygen species e- - O3 O3 H+ e- + - H2O H2O HO3 OH H+ H+ e- - - O OH OH HO4 2 H+ H+ e- 2- - O H2O2 H2O2 H2O4 O H+ HO2 e- - HO2 HO2 hν H+ H+ e- e- 2- - O2 O2 O2 -2 -2/-1 -1/-1 -1/0 0 basic HxOy reactions in aqueous phase catalase 2 H2O2 → 2 H2O + O2 II - III Fenton reaction H2O2 (+ Fe ) → OH + OH (+Fe ) - + dismutase HO2 + O2 (+ H ) → H2O2 + O2 - - enzymatic reduction O2 (+ e ) → O2 - III II desactivation O2 (+ Fe ) → O2 (+ Fe ) - + ozone decay O3 + O2 (+ H ) → OH + 2 O2 Atmospheric chemistry Ozone formation within the troposphere 3 O( P) + O2 → O3 3 O3 +hν (λ<850 nm → O( P) + O2 3 NO2 +hν (λ<420 nm → O( P) + NO OH chemistry of the clean atmosphere hν 3 O3 O( P) O2 M hν H2O O(1D) OH O3 O3 HO2 H2O2 HO2 OH chemistry of the polluted atmosphere NO hν O3, HO2 (-OH) het NO2 HNO2 hν hν NO (-NO) (-NO) hν NO2 O3 OH HNO3 CO, VOC, O3, SO2 HO2 H2O2 hν RCHO HO2 ROOH RO2 RONO2 NO2 OH O2 HO2 RH R RO2 ROOH NO (-NO2) RO (-CO ) hν 2 O2 (-HO2) RCHO OH hν (-HO2) RCR hν RCO O O2 NO2 NO (-NO2) RC(O)O RC(O)OO RC(O)OONO2 [PAN] organic radical chemistry D) 1 ( O H O SO2 + O2 SO3 2 CO + O CO 2 O 2 RCH + 2O + NO O RCHO +H O + NO 3 2 2 2 2 O (ozone) O HO OH P) 3 ( O O NO The chemical cycle of „reactive“ oxygen NO k7 [][NO HO2 ] ( 10 ppt) k6 deposition Catalytic ozone destruction in remote areas NO2 OH HNO3 NO3 nocturnal chemistry hν formation on wetted surfaces HNO2 O3 het (precursors) CO, VOC, SO2 OH NO2 hν O3 O3 O3 O3 urban ozone „titration“ CO2, VOC´, SO3 HO2 NO (products) HO2 CO + 2 O2 + hν→CO2 + O3 net: SO2 + 2 O2 + hν→SO3 + O3 H2O2 RCH3 + 3 O2 + hν→RCHO + H2O + 2 O3 Dependence of ozone formation potential from NO and VOC concentration (Sillman diagramme) VOC = 100 ppb C VOC = 50 ppb C VOC = 20 ppb C ) 10 -1 9 8 7 6 5 4 3 2 formation ppb h (in potential 1 3 O 0 0 5 10 15 20 NO concentration (in ppb) gas phase ozone formation cycle NO NO2 NO3 hv H2O2 SO2 O3 HO2 OH HNO2 N2O5 ORG NO ORG H2O2 S(IV) O3 HO2 OH N(III) NO3 - S(VI) + products O2 N(V) aqueous phase ozone stoichiometry in sink products 1.5 O3 3.0 O3 2.0 O3 1.0 O3 0.5 O3 0.5 O3 1.0 O3 PAN O3 VOC, CO hν OH NO hν hν HO2 HNO3 N2O5 NO3 NO2 OH HO2 H2O2 NO2 O3 O3, HO2 hν NO hν gas phase OH HNO2 liquid phase VOC NO − NO − − H O 3 2 OH O2 /HO2 2 2 S(IV) S(IV) O3 products Oxidative stress The scheme of atmospheric impact factors climate forcing: positive / negative toxicity: physico-chemical acidity: nutrient / pollutant properties of the atmosphere acid / alkaline oxidation capacity: oxidation / reduction Oxidative Stress Oxidative stress is imposed on cells as a result of one of three factors: 1) an increase in oxidant generation, 2) a decrease in antioxidant protection, or 3) a failure to repair oxidative damage. Cell damage is induced by reactive oxygen species (ROS). ROS are either free radicals, reactive anions containing oxygen atoms, or molecules containing oxygen atoms that can either produce free radicals or are chemically activated by them. Examples are hydroxyl radical, superoxide, hydrogen peroxide, and peroxynitrite. The main source of ROS in vivo is aerobic respiration, although ROS are also produced by peroxisomal β-oxidation of fatty acids, microsomal cytochrome P450 metabolism of xenobiotic compounds, stimulation of phagocytosis by pathogens or lipopolysaccharides, arginine metabolism, and tissue specific enzymes. Under normal conditions, ROS are cleared from the cell by the action of superoxide dismutase (SOD), catalase, or glutathione (GSH) peroxidase. The main damage to cells results from the ROS-induced alteration of macromolecules such as polyunsaturated fatty acids in membrane lipids, essential proteins, and DNA. Additionally, oxidative stress and ROS have been implicated in disease states, such as Alzheimer's disease, Parkinson's disease, cancer, and aging. Atmospheric oxidative stress precursers atmosphere cell - H2O2 HO2 / O2 , OH NO + O3 NO3 NO2 + O3 NO3 O3 OH Ozone trend European ozone trend 6060 Pic du du Midi Midi (3000 (3000 m) m) trend (without Arosa and Zugspitze) JungfraujochJungfraujoch (3500 (3500 m) m) 5050 MontMont Ventoux Ventoux (1900 (1900 m) m) ) DeutscheDeutsche Alpen Alpen (1046 (1046 m) m) b p p 4040 HohenpeissenbergHoher Peißenberg (1000 (1000 m) m) n i ( n ZugspitzeZugspitze (3000 (3000 m) m) o i t a r t 3030 ArosaArosa (1860 (1860 m) m) n e c n o c 3 O 2020 1010 00 18851885 19051905 1925 1925 1945 1945 1965 1965 19851985 2005 year Ozone dependence from altitude (after historic Soviet and Swiss data from the 1920s and 1930s) 1600016 1400014 y = 0,1083x3,0499 12000 12 R2 = 0,9965 ) m 1000010 k n i ( 80008 e d u t 6 i 6000 t l a 40004 20002 0 0 00 10 102 2003 3004 4005 500 O3 concentration (in ppb) (note: in 2000-3000 m altitude about 15-20 ppb O3 must be added to the ground level) -3 Ozone trendatthestation Wahnsdorf(nearDresden) O3 concentration (in µg m ) 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 0 0 19521955 19601965 197 [O 1955 3 ] =35+ 1.4x(1974-2000), r 1958 1961 1964 1967 19700 1975198019 year 1973 1976 1979 1982 85 199019952000 2 1985 1955-1959 1960-1971 1972-1977 1974-2001 1955 - 1959 1960 – 1971 1971 – 1977 1974 – 2001 = 0.82 1988 1991 1994 1997 2000 European ozone trend (Marenco curve) 6060 PicPic du du Midi Midi (3000 (3000 m) m) trend (without Arosa and Zugspitze) JungfraujochJungfraujoch (3500 (3500 m) m) 5050 MontMont Ventoux Ventoux (1900 (1900 m) m) DeutscheDeutsche Alpen Alpen (1046 (1046 m) m) ) b p Hohenpeissenberg (1000 m) p Hoher Peißenberg (1000 m) 4040 n i ( Zugspitze (3000 m) n Zugspitze (3000 m) o i t a r Arosa (1860 m) t 3030 Arosa (1860 m) n e c altitude corrected Wahnsdorf data (3000 m) n o c altitude corrected Arosa data (3000 m) 3 O 2020 1010 00 18851885 1905 19251925 19451945 19651965 1985 year Number of days with exceedance found at means from all stations in German number of days and [O3], resp. in µg/m3 90 1999: 368); after Beilke 2000 80 70 60 y (number of stations: 1990: 201 und 50 40 least at one station and annual 30 20 10 0 1990 1991 >180 µg/m3 1992 >240 µg/m3 annual mean 1993 1994 1995 1996 1997 1998 1999 Stratospheric ozone: deviation from mean in nbar -48 -40 -32 -24 -16 16 24 -8 0 8 1967 1972 1977 1982 1987 1992 1997 2002 Ozone trendatstationHohenpeißenberg year ozone at 5,5 km (+30%) ozone at5,5km (-ozone at21km 15%) -8 -4 0 4 8 12 16 20 24 28 tropospheric ozone: deviation from mean in nbar seasonal maximum (summer) and minimum ozone (winter) 140 Schwarzwald-max ) 120 Wank-max -3 Brotjackriegel-max 100 Schauinsland-max Wurmberg-max 80 Brocken-max Schwarzwald-min 60 Wank-min 40 Brotjackriegel-min Schauinsland-min 20 Wurmberg-min ozone concentration (in µg m Brocken-min 0 1992 1993 1994 1995 1996 year Trend ozone saisonal mean (winter) 80 Schwarzwald 60 Wank Brotjackriegel Schauinsland Wurmberg [O3] in µg/m3 in [O3] 40 Brocken 20 1992 1993 1994 1995 1996 year Ozone variation Ozone profil measurements by BTU mobile lidar Elight M510 downtown Berlin (Alexanderplatz) during an intercomparison campaign with aircraft measurements In 1998 (BERLIOZ experiment) summer-winter ratio of ozone concnetration 0 1 2 3 4 5 6 0 500 Sp essar t Schwarzwald Altitude andsaisonalvariation Königstein 1000 Hoher Peißenberg Hoher Brocken Altitude a.s.l.