Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder

Size: px

Start display at page:

Download "Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder"

Janel Griffith
5 years ago
Views:

1 Gas- and Particle-Phase Products and their Mechanisms of Formation from the Reactions of Monoterpenes with N 3 Radicals: Comprehensive Measurements and Modeling Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder

2 Gas- and Particle-Phase Products and their Mechanisms of Formation from the Reactions of Monoterpenes with N3 Radicals: Comprehensive Measurements and Modeling Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder Megan Claflin

3 Southern xidant & Aerosol Study (SAS) Investigate the role of interactions among anthropogenic and biogenic emissions on air quality ( 3 and SA) Biogenic VCs are the most abundant class of VCs emitted Isoprene and monoterpenes are ~ 70% of ~1000 Tg yr 1 global emissions Conducted lab studies of oxidation of monoterpenes & isoprene to determine functional group composition for SAS-lab comparison

4 Ambient rganic Nitrates (J.(J. Geophys. Geophys. Res., Res., 2010) 2010) (PNAS, 2015) (Atmos. Chem. Phys, 2017) (Atmos. Chem. Phys., 2016) (Atmos. Chem. Phys, 2013) (PNAS, 2016) (Atmos. Chem. Phys, 2015) (Atmos. Chem. Phys, 2015)

5 Reactions of Monoterpenes (mostly b-pinene) + N 3 Radicals

6 Methods Functional Group Composition Deriv-Spec FTIR 8 m 3 FEP Teflon Environmental Chamber 55% RH Deliquesced (NH 4 ) 2 S 4 Seed Particles 1 ppm b-pinene 0.33 ppm N 2 5 N 3 + N 2 Filter Sampling DNPH Cartridges PFBHA Denuder Molecular Analysis HPLC Tenax GC-FID SMPS TDPBMS EI-MS b-pinene + N 3 reaction & SA formation complete in ~10 min TD-CI-ITMS ESI-MS Gas Sampling Particle Sampling ff-line Analysis

7 Mechanism of Reaction of b-pinene + N 3 Radicals N 2 N 2 + N 3 + N 3 β-pinene + 2 N 2 H N 2 R 2 HN N 2 R R 2 or N 3 N 2 + H H + Decomp N 2 Formaldehyde Nopinone Decomp + 2 N R H HCN N 2 N 2 R 2 or N 3 N 2 DCN o H N 2 Decomp + 2 N 2 HDCN N 2 TCN + R 2 N 2 N 2 R 2 N 2 H HDCN N 2 HCNA H H N 2 + Acetone

8 Multifunctional Gas-Phase Products

9 SA Product Separation & Quantitation: HPLC-UV Measure nitrate absorbance at 210 nm Quantify using authentic standard of Peak 6 compound

10 SA Product Identification: Mass Spectrometry Peak 6 Diacetal formation < 1 min

11 SA Products & Mass Fractions 95% of SA mass identified and quantified

12 SA Product Molar Yields Peak Number Monomer and ligomers Mole MW of Molar Fraction Product Yield (%) (%) Monomer ID Monomer Building Blocks Mole MW of Fraction Monomer (%) Molar Yield (%) HN a DCN b HCN c TCN HDCN HCNA Total monomer molar yield = 62.4% Based on min filter samples corrected for particle wall loss

13 Deriv-Spec Functional Group Analysis Carbonyl Ester Carboxyl Hydroxyl Peroxide Nitrate Carbonyl, ester, carboxyl, hydroxyl: derivatize Peroxide: oxidize 2I to I 2 Nitrate Measure UV-Vis absorbance Quantify using surrogate standards

14 SA Bulk Functional Group Analysis Deriv-Spec FTIR Functional groups per C 10 molecule No -H C-H C= N 2 with CH 2 without CH 2

15 SA Functional Group Composition: Bulk vs. Molecular Analysis Bulk Molecular Deriv-Spec HPLC-UV-MS Functional FG/C Group 10 Molecule Peroxide Ester Carbonyl Carboxyl Hydroxyl Nitrate Methylene *Estimated based on rate of sucrose hydrolysis at same ph * SA results: Claflin & Ziemann, JPCA, 2018

16 Mechanism of Reaction of β-pinene + N 3 Radicals N 2 N 2 + N 3 + N 3 Molar yields ParQcle phase = 62.4% β-pinene + 2 N 2 R 2 N 2 H HN 23.6% N 2 + Yeh & Ziemann, JPCA, 2015 Vereecken & Peeters, PCCP, 2009, 2010 H H Formaldehyde + Decomp Nopinone N 2 R 2 or N 3 N 2 Decomp + 2 N R 2 2 N 2 R 2 or N 3 N 2 R N 2 <1% No peroxide dimers No R 2 + H 2 No R 2 + N 3 (N 2 5 Δβ-pinene = 20 ppb) + H HCN DCN 25.9% 2.9% isomer 2.0% o N 2 HDCN N 2 TCN + H R 2 N 2 N 2 Decomp + 2 N 2 R 2 N 2 H HDCN 4.8% isomer 3.2% N 2 HCNA H H N 2 + Acetone

17 Unobserved Potential Additional Pathways Vereecken & Peeters PCCP, 2012 b-pinene + H 70% ring opening: 30% 2 Exothermicity (kcal mol 1 ) H ~30: N 3 ~20 No dinitrates No peroxides

Conclusions Identified and quantified essentially

N 3 radical reaction Developed quantitative gas- and

Demonstrates importance of particle-phase reactions

chemistry for other monoterpenes Future work

18 Conclusions Identified and quantified essentially all gas- and particle phase products from b-pinene + N 3 radical reaction Developed quantitative gas- and particle-phase reaction mechanism and model Demonstrates importance of particle-phase reactions in SA formation needs to be in models May be similar chemistry for other monoterpenes Future work includes: > ther monoterpenes > High H 2 and autoxidation conditions

Atmos. Chem. Lecture 12, 10/21/13: Atmospheric organic chemistry (intro!)

Atmos. Chem. Lecture 12, 10/21/13: Atmospheric organic chemistry (intro!) lareth: Measurement networks H + alkanes: New branch points ther oxidants, hydrocarbons Implicatons for H x PSet 3 due Wed 10/23;