Publication: Can Isoprene Oxidation Explain High Concentrations of Atmospheric Formic and Acetic Acid over Forests?

Publication - Can Isoprene Oxidation Explain High Concentrations of Atmospheric Formic and Acetic Acid over Forests?

Title: Can Isoprene Oxidation Explain High Concentrations of Atmospheric Formic and Acetic Acid over Forests?
DOI: 10.1021/acsearthspacechem.0c00010
Publication Year: 2020
Author list: Link, M. F.; Nguyen, T. B.; Bates, K. H.; Müller, J.-F.; Farmer, D. K.
Journal Short Name: ACS Earth Space Chem.
Publisher: ACS

Abstract
Formic and acetic acid concentrations are particularly high over forested areas of the world. However, the gas-phase mechanisms for producing these acids are poorly understood even for isoprene, the globally dominant biogenic hydrocarbon. We quantified formic and acetic acid production from reactions of hydroxyl radical (OH) (between high and low ranges of nitric oxide (NO) levels) with isoprene, methacrolein (MACR), isoprene epoxydiol (IEPOX), isoprene hydroxy hydroperoxide (ISOPOOH), and α-pinene from the focused isoprene experiments at California Institute of Technology (FIXCIT) laboratory chamber study. We find that (i) OH oxidation of MACR, IEPOX, and ISOPOOH are sources of formic acid, (ii) isoprene peroxy radical isomerization and associated photolysis oxidation products are potentially important sources of organic acids, and (iii) high levels of NO generally suppress organic acid formation from OH oxidation of isoprene. We modified existing chemical mechanisms for isoprene oxidation to account for organic acid production pathways observed in the FIXCIT study. We simulated organic acid production during the Southeastern Oxidant and Aerosol Study using the updated chemical mechanisms and represented acetic acid within a factor of 2 but still underpredicted formic acid by a factor of 6. While we cannot explain ambient formic acid with explicit chemical mechanisms, the FIXCIT results suggest that the oxidation of isoprene could account for as much as 70% of the global annual production of formic acid from gas-phase reactions.

Additional Notes



Experiments (18)

ID Name Start date Experiment Category Reaction Type Reactant(s) Oxidant Name Temperature Humidity Type of Seed RO2 Main Fate Data Sets (count) Actions
97 2014 FIXCIT Study_20140111_nitric oxide/ALPHA-PINENE/hydrogen peroxide_Hydroxyl radical_No Seed_Alpha-pinene + OH, high NO, dry, (NH4)2SO4 seed at end 2014-01-11 Gas phase chemical reaction Photooxidation nitric oxide, ALPHA-PINENE, hydrogen peroxide Hydroxyl radical 26 5 NO 13 Download
94 2014 FIXCIT Study_20140106_Isoprene/Ozone/Water_Hydroxyl radical_No Seed_Isoprene + OH + O3, low NO, dry, no seeds 2014-01-06 Gas phase chemical reaction Photooxidation Isoprene, Ozone, Water Hydroxyl radical 25 5 No Seed HO2 11 Download
390 2014 FIXCIT Study_20140117_4-hydroxy 3-peroxy ISOPOOH_Hydroxyl radical_No Seed_4,3-ISOPOOH + OH, low NO, dry, no seeds 2014-01-17 Gas phase chemical reaction Photooxidation 4-hydroxy 3-peroxy ISOPOOH Hydroxyl radical 25 5 HO2 14 Download
95 2014 FIXCIT Study_20140113_ALPHA-PINENE/nitric oxide/OZONE/formaldehyde_Nitrate radical_Ammonium sulfate_HO2 fate, dry RH, seed added at end 2014-01-13 Gas phase chemical reaction Dark oxidation ALPHA-PINENE, nitric oxide, OZONE, formaldehyde Nitrate radical 25 5 Ammonium sulfate HO2 12 Download
391 2014 FIXCIT Study_20140102_ISOPRENE/hydrogen peroxide_Hydroxyl radical_No Seed_Isoprene + OH, low NO, dry, no seeds 2014-01-02 Gas phase chemical reaction Photooxidation ISOPRENE, hydrogen peroxide Hydroxyl radical 27 5 HO2 10 Download
392 2014 FIXCIT Study_20140103_ISOPRENE/nitric oxide/hydrogen peroxide_Hydroxyl radical_No Seed_Isoprene + OH, high NO, dry, no seeds 2014-01-03 Gas phase chemical reaction Photooxidation ISOPRENE, nitric oxide, hydrogen peroxide Hydroxyl radical 26 5 NO 9 Download
396 2014 FIXCIT Study_20140110_ALPHA-PINENE/hydrogen peroxide_Hydroxyl radical_No Seed_Alpha-pinene + OH, low NO, dry, (NH4)2SO4 seed at end 2014-01-10 Gas phase chemical reaction Photooxidation ALPHA-PINENE, hydrogen peroxide Hydroxyl radical 27 5 HO2 13 Download
398 2014 FIXCIT Study_20140107_ISOPRENE/Methyl nitrite_Hydroxyl radical_No Seed_Isoprene + OH "slow chemistry" (isomerization), dry, 40C, no seeds 2014-01-07 Gas phase chemical reaction Photooxidation ISOPRENE, Methyl nitrite Hydroxyl radical 40 5 Autoxidation/Isomerization 13 Download
399 2014 FIXCIT Study_20140109_ISOPRENE/Nitrogen dioxide/Ozone/Formaldehyde_Nitrate radical_N/A_Isoprene + NO3/HO2, dry, no seed 2014-01-09 Gas phase chemical reaction Dark oxidation ISOPRENE, Nitrogen dioxide, Ozone, Formaldehyde Nitrate radical 26 5 N/A HO2 13 Download
400 2014 FIXCIT Study_20140125_METHACROLEIN/hydrogen peroxide_Hydroxyl radical_Ammonium sulfate_Methacrolein + OH, low NO, dry, (NH4)2SO4 seed at end 2014-01-25 Gas phase chemical reaction, Aerosol formation Photooxidation METHACROLEIN, hydrogen peroxide Hydroxyl radical 28 5 Ammonium sulfate HO2 14 Download
401 2014 FIXCIT Study_20140126_METHACROLEIN/nitrogen dioxide/methyl nitrite/methacrylic acid epoxide_Hydroxyl radical_Ammonium sulfate_Methacrolein + OH, high NO, dry, then humidify and add (NH4)2SO4 seed at end 2014-01-26 Gas phase chemical reaction, Aerosol formation Photooxidation METHACROLEIN, nitrogen dioxide, methyl nitrite, methacrylic acid epoxide Hydroxyl radical 26 5 Ammonium sulfate NO2 15 Download
403 2014 FIXCIT Study_20140116_ALPHA-PINENE/Methyl nitrite_Hydroxyl radical_No Seed_Alpha-pinene + OH "slow chemistry", dry, 40C, no seeds 2014-01-16 Gas phase chemical reaction Photooxidation ALPHA-PINENE, Methyl nitrite Hydroxyl radical 40 5 Autoxidation/Isomerization 13 Download
405 2014 FIXCIT Study_20140121_ISOPRENE/hydrogen peroxide_Hydroxyl radical_No Seed_Isoprene + OH, low NO, dry, no seeds, lower initial concentration 2014-01-21 Gas phase chemical reaction Photooxidation ISOPRENE, hydrogen peroxide Hydroxyl radical 27 5 HO2 14 Download
406 2014 FIXCIT Study_20140123_ISOPRENE/OZONE_Hydroxyl radical_No Seed_Isoprene + OH + O3, low NO, 50% humidity, no seeds 2014-01-23 Gas phase chemical reaction Photooxidation ISOPRENE, OZONE Hydroxyl radical 25 50 HO2 13 Download
407 2014 FIXCIT Study_20140124_4-hydroxy-3-nitrooxy ISOPN/Methyl nitrite/nitric oxide/_Hydroxyl radical_Ammonium sulfate_4,3-isoprene hydroxynitrate + OH, high NO, 50% RH, (NH4)2SO4 seed 2014-01-24 Gas phase chemical reaction, Aerosol formation Photooxidation 4-hydroxy-3-nitrooxy ISOPN, Methyl nitrite, nitric oxide, Aerosol Hydroxyl radical 26 52 Ammonium sulfate NO 13 Download
408 2014 FIXCIT Study_20140127_trans-beta-IEPOX/methyl nitrite_Hydroxyl radical_No Seed_Trans-beta-IEPOX + OH, moderate NO, dry, no seeds 2014-01-27 Gas phase chemical reaction Photooxidation trans-beta-IEPOX, methyl nitrite Hydroxyl radical 25 5 NO 13 Download
409 2014 FIXCIT Study_20140129_isoprene/ozone/CYCLOHEXANE_Ozone_No Seed_Isoprene + O3, cyclohexane OH scrubber, 50% humidity, no seeds 2014-01-29 Gas phase chemical reaction Photooxidation isoprene, ozone, CYCLOHEXANE Ozone 25 58 Not Sure 13 Download