Problem of man-made Sulphur is very actual for air quality in - PowerPoint PPT Presentation

01 • Problem of man-made Sulphur is • very actual for air quality in Russia • NEW environmental law of Russian Government is: • since 1 July 2006 : • Suphur wastes by diesels must be • lower on 38% • Benzene oil must be without Pb addition

02 Sunlight action on the oxidation SO2 into sulphate aerosol affecting the climate and ecology of the Earth Galina Skubnevskaya , Serge Dubtsov, Alex Ankilov Alex Kozlov Galina Dultseva RFBR Grant 02-05-64783

03 • Global Sulphur cycle • Man-made stress for Earth • Ways of SO2 transformation to H2SO4 • About role of exited SO2 in the atmosphere • Some results of study of exited SO2 (1980-2005) (Photolysis and Photonucleation ) • Some conclusions and plans for future

Global sulphur cycle In the air over Baikal lake 04 Sulphur flow is ~ 3-5 tonn/km 2 year Acidity of rains and snow << 5,6 pH ATMOSPHERE Атмосфера East Siberian forests are in danger OTHERS Другие H SO 4 SO 2 COS g/m3 2 0,7 0,5 2,3 0,8 Reservoirs (Gt): 102 Crust 19000000 20 Sedimentary rock 163 258 26 72 28 208 ~28 5000000 Реки Почва Rivers 5 2,6·10 Океаны Soil Вулканы 35 4 Oceans 13000000 Oceans Volca- S = 10 9 орг 1,3·10 9 Биомасса Озёра 1e9 noes 760 2e9 Soil 260 Lakes Биота 138 BIOTA Living organisms 0.76 9 9 Осадки 0,3·10 Осадки 5,2·10 Precipitations 3e8 OCEANS 9 9 Кора 2,2·10 Кора 16,6·10 Atmosphere 0,004 Precipitations 5e8 Crust 2e9 Океаны Суша Crust 17e9 Sulfur distribution (Mt) on the Earth surface and Sulfur flows ( М t/year)

05 Oxidation state of S changes in Global cycle Oxidation Степень окисления state 0 0 S Сульфиды metal H S, ДМС H 2 S, (CH3) 2 S – 2 металлов sulfides 2 SO 2 + 4 2- H SO + 6 SO 2 4 4 Red arrows – microbiological processes

In XXI century Emission of S from Man-made 06 sources became comparable with Natural ones Content, ppb -1 g/m3 polluted Remote air regions О 3 100-500 20-80 N О + NO2 50-750 0,1-0,5 0,1-1 SO2 2-300 Man-made 1-5 500- hydrocar- 1200 bons 3-10 50-70 aerosols mkg/ m 3 mkg/ m 3

07 Acidity of rains ,snow and fogs < 5,6 pH is dangerous SO 2 influence on the acidity of atmospheric precipitations: Flow to the Earth surface Residence time, hour 2– SO 2 H 2 SO 4 SO 4 – – Oxidation 37 – 50 – Neutralization 100 83 70 Washing out Dry deposition 70 200 –

08 Sunlight action on SO2 generates ecological problems in Earth atmosphere • Sunlight action stimulates transformations of primary S wastes into ecotoxicants in the air and in photosmog • Photosmog includes toxicants and aerosols with S that affect on lungs and health of citizens .( H2S, (CH3)2S, SO2, H2SO4, organic sulphoacids in air and in aerosols) • Sulphate nanoparticles in lower stratosphere (Junge layer on h~16 km) affect climate and fall of acid rains • Photochemistry and photonucleation of SO2 is unsolved global problem in the Earth atmosphere.

Typical Relation of SO4(2-)/ SO2 in the air 09 At the surface of Earth Substance Remote regions Urban areas Cities (mcg/m 3 ) SO 2 ~0,2 0,1- 0,6 0,3-1 2– (aerosol) (mcg/m 3 ) SO 4 ~0,8 0,2-0,5 1-5 10 2– SO / SO 4 2 3 [SO ], мкг / м 4 2 1 0,4 2– SO 4 0,2 SO 2 80° 60° 40° 20° 0° 20° 40° 60° с . ш . Географическая широта ю . ш . 2– (aerosol) /SO2>1 SO 4 SUNLIGHT ACTION ? is due to

10 Chemical Ways of SO2 oxidation • Reactions on soot and atmospheric particles ( heterogenic oxidation ) • Reactions in rains ( in liquid phase) • Reactions of photocatalysis by particles (ZnO ) Ways of SO2 transformation to H2SO4 • Photochemical oxidation of SO2 in the air • a)SO2 is activated by free radicals OH,HO2, etc. • b) SO2 is activated by sunlight with SO2 exitation in high electronic states of SO2 with energy > 2 Ev ( ~ 45 kcal/mole) (exited SO2 reactions)

12 SO2exited + SO2 � SO3+SO Atmospheric structure is dominate? Давление , Па –6 –4 –2 0 6 4 10 10 10 10 10 10 200 Температура 160 P(H)=P exp[–gmH/RT] 0 120 м n(H)=n exp[–gmH/KT] , к 0 H а т о с ы 80 В Мезосфера Давление 40 Стратосфера SO2+ OH � H2SO4 20 Тропосфера is dominate 100 300 500 700 Температура , К T e m p e r a t u r e a n d p r e s s u r e v e r t i c a l d i s t r i b u t i o n Temperature, ° С Region Range, km pressure, Torr Stratosphere 18 – 50 – 56 – 2 Troposphere 0 –-18 760 -…. 15 – 56

13 Heterogeneous oxidation of SO2 � H2SO4 SO 2 is absorbed by fly ash and soot particles. Photocatalysis is possible on metal oxides particles that have semiconducters properties (TiO 2 , ZnO,etc.) I 2 + , e ) – + )(O ) – · MeO (MeO (MeO 2(O ) (MeO ) Адс . Адс . 2 H O SO 2 2 2 + )(H O ) – · · (MeO [SO (O)] (MeO )(O ) Адс . 2 2 Адс . 2 · · 2(HO ) (MeO ) (SO ) (MeO )(O ) Адс . 3 Адс . · · 2– + (SO ) + 2( HO ) [SO (HO )] (SO ) + 2(H ) Адс . Адс . Адс . 2 2 2 Адс . Адс . 4

17 Chemical Ways of SO2 oxidation • Reactions on soot and atmospheric particles ( heterogenic oxidation ) • Reactions in rains ( in liquid phase) • Reactions of photocatalysis by particles (ZnO ) Ways of SO2 transformation to H2SO4 • Photochemical oxidation of SO2 in the air • a)SO2 is activated by free radicals OH,HO2, etc. • b) SO2 is activated by sunlight with SO2 exitation in high electronic states of SO2 with energy > 2 Ev ( ~ 45 kcal/mole) (exited SO2 reactions)

Homogeneous oxidation where SO 2 is “ passive”reactant 14 time, h. Oxidant Reaction k cm 3 /s concentration, cm –3 SO 2 + O 2 → SO 3 + O· 10 –30 5 ·10 18 50000000 SO 2 + O 3 → SO 3 + O 2 10 –22 8 ·10 11 3000000 SO 2 + HO· 2 → SO 3 + HO· 7,8 ·10 –16 3 ·10 8 1200 SO 2 + CH 3 OO· → SO 3 + CH 3 O· 1,8 ·10 –14 7 ·10 7 227 SO 2 + HO· +H 2 O → H 2 SO 4 + HO· 1,8 ·10 –12 1,8 ·10 6 86 2 SO2 oxidation proceeds due to formation of secondary S radicals: SO 2 + HO· → HSO 3 · HSO 3 · + O 2 → HSO 5 · HSO 3 · + NO2 → HSO 4 · + NO HSO 4 · + NO 2 + H 2 O → H 2 SO 4 + HNO 3

SO2 can be photoactive reactant in the atmosphere 15 Absorption spectra of SO2 3 SO 2 + SO 2 → very week band 3 B 1 ; E~25-50 kcal 330-390nm 1,3 SO 2 + SO2 → week bands 1 B 1 , 1 А 2 ; E ~ 50-90 kcal 260-340 nm Energy 1800-2400 А Strong band , OS-O � O + SO ; 247nm D (OS - O) = 5 эВ =247 nm

Heterogeneus oxidation of SO 2 18 Soil and dust particles absorb SO2 and O2 and catalyze transformation SO2 � H2SO4 Dependence of Rate of SO2 oxidation over power plants Относительная доля k, ч –1 1,0 SO 2 4 0,02 0,6 3 H SO 2 4 0,01 Сульфаты 2 0,2 1 10 20 30 40 50 6 8 10 12 14 16 18 Время , ч Время суток , ч

19 • Experimental set-up for study of photonucleation

• Kinetics of Photolysis of gas precursor 20 of aerosol formation 0.05 0.00 Photolysis rate -0.05 -0.10 ln (D/D 0 ) -0.15 -0.20 -4 s -1 K phot = 5.3684x10 -0.25 -0.30 -0.35 0 100 200 300 400 500 600 Time / s

21 Grows of particles in time during UV action on precursor vapor in gas phase 7 10 -3 Particle concentration / cm 6 10 Rate of birth of particles 5 10 1 = 3 Rate of photolysis of 4 10 10 W phot = 2.68 х 10 2 precursor in the gas phase 10 W phot = 1.03 х 10 3 10 10 W phot = 0.41 х 10 lines - model calculation 2 10 0,1 1 10 Time / s Comparison of modeling and experimental data allows to calculate key value of the photonucleation - rate of birth of particles

22 SO2 photonucleation is dependent on n-pentane pressure in SO2+C5H12+air mixture for reaction NOTE : Photoaerosol of HRSOx acids continue to grow in dark but photoaerosol of H2SO4 does not grow in dark Зависимость концентрации аэрозоля от давления пентана при фотолизе смеси SO 12 - воздух 2 - C 5 H 6,5 6,0 5,5 Lg N / a.u. 5,0 4,5 4,0 3,5 3,0 2,5 2,0 Pentane Pressure, Torr 0 2 4 6 8 10 12 14 [C 5 H 12 ] / Torr

23 Application HPLC, ESR, NMR,UV,IR,MS methods for analysis of chemical properties of photoproducts Detection of short-lived radicals OH Analysis of Sulphate aerosol by Bigg’s by spin traps ESR method method with electron microscopy help 10000 5000 0 -5000 -10000 3380 3400 3420 3440 3460 3480 Gauss Dultseva, G.G., Skubnevskaya, G.I., Mironenko V.E., Graduate work, NSU (1982) Volodarsky, L.V.,Tikhonov, A.Y. J.Phys.Chem. 1996 , v.100, 17523

24 Analysis of gas and aerosols products Methods and approach for particles analysi s employed • Procedures of sample preparation , arte-facts elimination High Performance Liquid Chromatography • • UV, IR spectroscopy • NMR spectroscopy • Electron microscopy Gas chromatography – Mass spectrometry • • Thin Layer Chromatography • Qualitative analytical procedures for functional groups • Ion chromatography Etc. •