scholarly journals OH reactivity in a South East Asian tropical rainforest during the Oxidant and Particle Photochemical Processes (OP3) project

2013 ◽  
Vol 13 (18) ◽  
pp. 9497-9514 ◽  
Author(s):  
P. M. Edwards ◽  
M. J. Evans ◽  
K. L. Furneaux ◽  
J. Hopkins ◽  
T. Ingham ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Tropical Rainforest ◽  
Primary Source ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Large Variability ◽  
Photochemical Processes ◽  
Radical Reactivity ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. OH (hydroxyl radical) reactivity, the inverse of the chemical lifetime of the hydroxyl radical, was measured for 12 days in April 2008 within a tropical rainforest on Borneo as part of the OP3 (Oxidant and Particle Photochemical Processes) project. The maximum observed value was 83.8 ± 26.0 s−1 with the campaign averaged noontime maximum being 29.1 ± 8.5 s−1. The maximum OH reactivity calculated using the diurnally averaged concentrations of observed sinks was ~ 18 s−1, significantly less than the observations, consistent with other studies in similar environments. OH reactivity was dominated by reaction with isoprene (~ 30%). Numerical simulations of isoprene oxidation using the Master Chemical Mechanism (v3.2) in a highly simplified physical and chemical environment show that the steady state OH reactivity is a linear function of the OH reactivity due to isoprene alone, with a maximum multiplier, to account for the OH reactivity of the isoprene oxidation products, being equal to the number of isoprene OH attackable bonds (10). Thus the emission of isoprene constitutes a significantly larger emission of reactivity than is offered by the primary reaction with isoprene alone, with significant scope for the secondary oxidation products of isoprene to constitute the observed missing OH reactivity. A physically and chemically more sophisticated simulation (including physical loss, photolysis, and other oxidants) showed that the calculated OH reactivity is reduced by the removal of the OH attackable bonds by other oxidants and photolysis, and by physical loss (mixing and deposition). The calculated OH reactivity is increased by peroxide cycling, and by the OH concentration itself. Notable in these calculations is that the accumulated OH reactivity from isoprene, defined as the total OH reactivity of an emitted isoprene molecule and all of its oxidation products, is significantly larger than the reactivity due to isoprene itself and critically depends on the chemical and physical lifetimes of intermediate species. When constrained to the observed diurnally averaged concentrations of primary VOCs (volatile organic compounds), O3, NOx and other parameters, the model underestimated the observed diurnal mean OH reactivity by 30%. However, it was found that (1) the short lifetimes of isoprene and OH, compared to those of the isoprene oxidation products, lead to a large variability in their concentrations and so significant variation in the calculated OH reactivity; (2) uncertainties in the OH chemistry in these high isoprene environments can lead to an underestimate of the OH reactivity; (3) the physical loss of species that react with OH plays a significant role in the calculated OH reactivity; and (4) a missing primary source of reactive carbon would have to be emitted at a rate equivalent to 50% that of isoprene to account for the missing OH sink. Although the presence of unmeasured primary emitted VOCs contributing to the measured OH reactivity is likely, evidence that these primary species account for a significant fraction of the unmeasured reactivity is not found. Thus the development of techniques for the measurement of secondary multifunctional carbon compounds is needed to close the OH reactivity budget.

scholarly journals OH reactivity in a South East Asian Tropical rainforest during the Oxidant and Particle Photochemical Processes (OP3) project

2013 ◽  
Vol 13 (2) ◽  
pp. 5233-5278 ◽  
Author(s):  
P. M. Edwards ◽  
M. J. Evans ◽  
K. L. Furneaux ◽  
J. Hopkins ◽  
T. Ingham ◽  
...  
Keyword(s):  
Tropical Rainforest ◽  
Primary Source ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Large Variability ◽  
Reactive Carbon ◽  
Carbon Compounds ◽  
Isoprene Oxidation ◽  
Master Chemical Mechanism ◽  
Physical And Chemical

Abstract. OH reactivity, the reciprocal of its lifetime from reaction with its sinks, was measured for 12 days in April 2008 within a tropical rainforest on Borneo as part of the OP3 project. The maximum observed value was 83.8 ± 26.0 s−1 with the campaign averaged noon-time maximum being 29.1 ± 8.5 s−1. The maximum OH reactivity calculated using the campaign averaged noon-time concentrations of observed sinks was ~18 s−1, significantly less than the observations, consistent with other studies in similar environments. OH reactivity was dominated by reaction with isoprene. Numerical simulations of isoprene oxidation using the Master Chemical Mechanism (v3.2) in a highly simplified physical and chemical environment show that the steady state OH reactivity is a linear function of the OH reactivity due to isoprene alone, with a maximum multiplier being equal to the number of isoprene OH attackable bonds (10). Thus the emission of isoprene constitutes a significantly larger emission of reactivity than is offered by the primary reaction with isoprene alone, with significant scope for the secondary oxidation products of isoprene to constitute the missing reactivity. A physically and chemically more sophisticated simulation (including physical loss, photolysis, and other oxidants) showed that the calculated OH reactivity is reduced by the removal of the OH attackable bonds by other oxidants and photolysis, and by physical loss (mixing and deposition). The calculated OH reactivity is increased by peroxide cycling, and by the OH concentration itself. Notable in these calculations is that the lifetime of OH reactivity is significantly longer than the lifetime of isoprene and critically depends on the chemical and physical lifetime of intermediate species. When constrained to the observed campaign averaged diurnal concentrations of primary volatile organic compounds (VOCs), O3, nitrogen oxides (NOx) and other parameters, the model underestimated the observed mean OH reactivity by 30%. However, it was found that: (1) the short lifetimes of isoprene and OH lead to a large variability in their concentrations and so significant variation in the calculated OH reactivity, (2) uncertainties in the OH chemistry in these high isoprene environments can lead to an underestimate of the OH reactivity, and (3) the physical loss of species that react with OH plays a significant role in the calculated OH reactivity, (4) a missing primary source of reactive carbon would have to be emitted at a rate equivalent to 50% that of isoprene to account for the missing OH sink. A clear argument for a significant missing flux of primary emitted VOC compounds to account for the unmeasured reactivity is not found and the development of techniques for the measurement of secondary multifunctional carbon compounds is needed to close the OH reactivity budget.

scholarly journals Emissions of putative isoprene oxidation products from mango branches under abiotic stress

2013 ◽  
Vol 64 (12) ◽  
pp. 3669-3679 ◽  
Author(s):  
Kolby J. Jardine ◽  
Kimberly Meyers ◽  
Leif Abrell ◽  
Eliane G. Alves ◽  
Ana Maria Yanez Serrano ◽  
...  
Keyword(s):  
Abiotic Stress ◽  
Oxidation Products ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

scholarly journals Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling

2008 ◽  
Vol 8 (4) ◽  
pp. 14033-14085 ◽  
Author(s):  
D. Taraborrelli ◽  
M. G. Lawrence ◽  
T. M. Butler ◽  
R. Sander ◽  
J. Lelieveld
Keyword(s):  
Atmospheric Chemistry ◽  
Oxidation Mechanism ◽  
Tropospheric Chemistry ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Good Representation ◽  
Chemical Production ◽  
Global Models ◽  
Mixing Ratios ◽  
Isoprene Oxidation

Abstract. We present an oxidation mechanism of intermediate size for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended as the second version of the well-established Mainz Isoprene Mechanism (MIM). Our aim is to improve the representation of tropospheric chemistry in regional and global models under all NOx regimes. We evaluate MIM2 and re-evaluate MIM through comparisons with MCM v3.1. We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios. Unlike MIM, MIM2 produces small relative biases for NOx and organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates (RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative biases with respect to hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), methanol (CH3OH), formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids (HCOOH and CH3C(O)OH), being always below ≈6% in all NOx scenarios studied. Most of the isoprene oxidation products are represented explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal. MIM2 is mass-conserving with respect to carbon, including CO2 as well. Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources, as well as for studies focused on the carbon cycle. Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO), propene (CH2=CHCH3) and glyoxal (CHOCHO) with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively. Our new mechanism is expected to substantially improve the results of atmospheric chemistry models by more accurately representing the interplay between atmospheric chemistry, transport and deposition, especially of nitrogen reservoir species. MIM2 allows regional and global models to easily incorporate new experimental results on the chemistry of organic species.

Secondary organic aerosol yields from cloud-processing of isoprene oxidation products

2008 ◽  
Vol 35 (2) ◽  
Author(s):  
Barbara Ervens ◽  
Annmarie G. Carlton ◽  
Barbara J. Turpin ◽  
Katye E. Altieri ◽  
Sonia M. Kreidenweis ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Cloud Processing ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

scholarly journals Marine aerosol production: a review of the current knowledge

2007 ◽  
Vol 365 (1856) ◽  
pp. 1753-1774 ◽  
Author(s):  
Colin D O'Dowd ◽  
Gerrit de Leeuw
Keyword(s):  
Sulphuric Acid ◽  
Current Knowledge ◽  
Oxidation Products ◽  
Marine Aerosol ◽  
Aerosol Formation ◽  
Multistep Process ◽  
Isoprene Oxidation ◽  
Iodine Oxides ◽  
20 Nm ◽  
Isoprene Oxidation Products

The current knowledge in primary and secondary marine aerosol formation is reviewed. For primary marine aerosol source functions, recent source functions have demonstrated a significant flux of submicrometre particles down to radii of 20 nm. Moreover, the source functions derived from different techniques up to 10 μm have come within a factor of two of each other. For secondary marine aerosol formation, recent advances have identified iodine oxides and isoprene oxidation products, in addition to sulphuric acid, as contributing to formation and growth, although the exact roles remains to be determined. While a multistep process seems to be required, isoprene oxidation products are more likely to participate in growth and sulphuric acid is more likely to participate in nucleation. Iodine oxides are likely to participate in both nucleation and growth.

scholarly journals Canopy fluxes of monoterpene, isoprene and isoprene oxidation products in a pine-oak forest

2020 ◽  
Vol 76 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Tomoki MOCHIZUKI ◽  
Satoru TAKANASHI ◽  
Ryuichi WADA ◽  
Yuzo MIYAZAKI ◽  
Takashi NAKANO ◽  
...  
Keyword(s):  
Oxidation Products ◽  
Oak Forest ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

scholarly journals Measurements of total hydroxyl radical reactivity during CABINEX 2009 – Part 1: field measurements

2014 ◽  
Vol 14 (6) ◽  
pp. 2923-2937 ◽  
Author(s):  
R. F. Hansen ◽  
S. M. Griffith ◽  
S. Dusanter ◽  
P. S. Rickly ◽  
P. S. Stevens ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Flow Reactor ◽  
Trace Gases ◽  
Field Measurements ◽  
Oxidation Products ◽  
Radical Reactivity ◽  
Inorganic Species ◽  
Volatile Organic ◽  
Interaction Experiment ◽  
Northern Michigan

Abstract. Total hydroxyl radical (OH) reactivity was measured at the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions, and Transport) forested field site in northern Michigan during the 2009 Community Atmosphere–Biosphere INteraction EXperiment (CABINEX). OH reactivity measurements were made with a turbulent-flow reactor instrument at three heights from the forest floor above (21 and 31 m) and below (6 m) the canopy at three different time periods during the CABINEX campaign. In addition to total OH reactivity measurements, collocated measurements of volatile organic compounds (VOCs), inorganic species, and ambient temperature were made at the different heights. These ancillary measurements were used to calculate the total OH reactivity, which was then compared to the measured values. Discrepancies between the measured and calculated OH reactivity, on the order of 1–24 s−1, were observed during the daytime above the canopy at the 21 and 31 m heights, as previously reported for this site. The measured OH reactivity below the canopy during the daytime was generally lower than that observed above the canopy. Closer analysis of the measurements of OH reactivity and trace gases suggests that the missing OH reactivity could come from oxidation products of VOCs. These results suggest that additional unmeasured trace gases, likely oxidation products, are needed to fully account for the OH reactivity measured during CABINEX.

Sign in / Sign up

Export Citation Format

Share Document