EFFECT OF NOX IN THE PHOTOCHEMICAL SYSTEM OF Α-PINENE

Transcription

1 EFFECT OF NOX IN THE PHOTOCHEMICAL SYSTEM OF Α-PINENE I SUNGAH KANG, THOMAS MENTEL, JÜRGEN WILDT, IIDA PULLINEN MONIKA SPRINGER, SEBASTIAN SCHMITT

2 1. MOTIVATION Peroxy Radical and Highly Oxidized Molecule(HOM) SOA? 1. Monomer HOM pattern change 2. Fragmentation 3. Dimer suppression 4. Alkoxy-peroxy pathway Iida Pullinen thesis Ehn et al December 2018 Page 2

3 2. EXPERIMENTS: JÜLICH PLANT ATMOSPHERE CHAMBER black lights CPC SMPS HR-TOF-AMS T = 288K RH = 60% Selective to NO 3 -HOM CIMS -TOF!!! Experimental procedure - continously stirred tank reactor (1450l), residence time : min. - bring system into steady state - UV on: photolyze O 3 and produce OH, range cm -3 - black lights on: photolyze NO 2 -> NO ( ppb) 06 December 2018 Page 3

4 Normalized Signal Normalized Signal Normalized Signal Normalized Signal 3.1 RESULT: MONOMER HOM PATTERN CHANGE 3.5x Organic Nitrate Peroxy Radical Termination Product 0.3 ppb NOx m/z 3.5x ppb NOx m/z 3.5x ppb NOx m/z Reaction: RO2+HO2, RO2+RO2 3.5x ppb NOx RO2+NO, RO2+NO m/z 06 December 2018 Page 4

5 3.1 RESULT: MONOMER HOM PATTERN CHANGE SVOC LVOC ELVOC Fuchs-Sutugin! c(hom) = P HOM L HOM c(hom) 0 c(hom) = L W HOM +L P HOM L W HOM L P HOM = γ eff ῡ 4 S P No dependency on termination functional group : Similar functionality (multiple hydroperoxyl groups) Pullinen et al in preparation 06 December 2018 Page 5

6 3.2 RESULT: FRAGMENTATION Fragmentation of Monomer and Dimer formation Alkoxy radical: ROO + NO RO + NO 2 Increase of smaller compounds in monomer and dimer range More volatile compounds 06 December 2018 Page 6

7 3.3 RESULT: DIMER SUPPRESSION Dimer intensity decreased (16times) 1. RO 2 + NO/NO 2 Organic Nitrate 2. Smaller dimer(c<20) C /C 20 (2 9.5) 06 December 2018 Page 7

8 3.3 RESULT: DIMER SUPPRESSION Effect on SOA? Dimer involving one relative volatile compound = lose mass of dimer (Dimer formation involves less functionalized peroxy radical, SVOC) 06 December 2018 Page 8

9 3.4 RESULT: ALKOXY-PEROXY PATHWAY Correction for NPF, factors , correction for turnover, factors of Reference for normalization: ( ± cm -3 s -1 at ~0.3 ppb NO X ) a) If HOM-alkoxy radical decompose to small fragments ΣHOM number concentration decrease b) If HOM-alkoxy rearrange, keeping the C-number (observable with NO 3- CIMS) ΣHOM number concentration constant 06 December 2018 Page 9

10 3.4 RESULT: ALKOXY-PEROXY PATHWAY Still high amount of Peroxy Radical H-shift O 2 addition Alkoxy-peroxy pathway keeps RO2 up 06 December 2018 Page 10

11 3.4 RESULT: ALKOXY-PEROXY PATHWAY Mass Defect plot Kendrick-mass=IUPAC-mass x C: Da H: Da O: Da N: Da 1. No NOx has only dimer in this middle mass range 2. Monomer only appear when there is NOx oxidation degree increased 06 December 2018 Page 11

12 4.SUMMARY Effect of NOx in photochemical system of α-pinene a. Monomer HOM pattern change Ketone, Hydroperoxide, Alcohol Organic Nitrate Not much effect on SOA mass (γ eff ) b. Fragmentation increased Major C10 compounds Increase of C 5 to C 9 compound SOA mass suppression (Less condensable compound) Sarrafzadeh et al, 2016 c. Dimer suppression of HOM-SVOC dimers Lose chance for SVOC to condense on SOA (Dimer-O 2 lose) Smaller dimers because of fragmentation higher vapor pressure SOA mass suppression (main reason) However: d. Alkoxy-Peroxy Pathway Produce more peroxy radical (even with lower [OH]) SOA mass gain (Compensate suppression) Page 12

13 00 Month 2018 Page 13

14 Back up slides 00 Month 2018 Page 14

15 HOM in photochemical systems Monomers C 10 Dimers C 20 HOM are efficiently formed with OH by α-pinene (and β-pinene) Berndt et al., 2016 Pullinen, PhD thesis, 2016

16 NO X controls photochemical OH / HO 2 system HNO 3 O +H O 3 2 low NO X CO CH VOC 4 +NO 2 OH +hn NO 2 HO 2 + HO 2 H 2 O 2 + O 2 radical sink medium NO X HO 2 + NO OH + NO 2 radical recycling CO 2 OVOC HO 2 +HO 2 HO 2 2 NO high NO X NO 2 + OH +M HNO 3 radical sink

17 Starting point: β-pinene SOA yield as f[no X ] Sarrafzadeh et al., 2016

18 increase of [OH]: NO+HO 2 NO 2 + OH 07 December 2018 Page 18

19 lower [OH]: OH+NO 2 HNO 3 07 December 2018 Page 19

20 HOM-ON, HOM-PP -> SOA: condensation Photochemistry in JPAC into ss Add seed aerosol increase surface sink, decrease HOM lifetime Apply gas-phase kinetics L P HOM = γ eff ῡ 4 S P

21 Apply: Correction for NPF, factors Correction for OH, factors of reference for normalization: ( ± cm -3 s -1 at ~0.3 ppb NO X ) Black: HOM concentration fairly constant Mass decreases: HOM lower with lower molecular weight Red: Hydrolysis of type HOM-RONO2 > HOM-ROH will affect the HOM mass