Supplementary material to "Characterization of Ozone Production in San Antonio, Texas Using Observations of Total Peroxy Radicals"

Abstract. Observations of total peroxy radical concentrations ([XO2] ≡ [RO2] + [HO2]) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made on board the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas, region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv h−1, a factor of 2 higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv h−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO2, suggest that the region was predominantly NOx-limited. Only approximately 20 % of observations were in the VOC-limited regime, predominantly before 11:00 EST, when ozone production was low. Biogenic volatile organic compounds (VOCs) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

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Characterization of Ozone Production in San Antonio, Texas Using Observations of Total Peroxy Radicals

10.5194/acp-2018-1083 ◽

2018 ◽

Cited By ~ 1

Author(s):

Daniel C. Anderson ◽

Jessica Pavelec ◽

Conner Daube ◽

Scott C. Herndon ◽

W. Berk Knighton ◽

...

Keyword(s):

San Antonio ◽

Ozone Production ◽

Peroxy Radicals ◽

Urban Center ◽

Entire Region ◽

Volatile Organic ◽

In Situ Observations ◽

Study Sites

Abstract. Observations of total peroxy radicals (XO2 = RO2 + HO2) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made onboard the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv hr−1, a factor of two higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv hr−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO3, suggest that the region is NOx limited for times after approximately 09:00 local time, before which ozone production is VOC-limited. Biogenic volatile organic compounds (VOC) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

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Unexpected Fast Monoterpene Oxidation In Eastern China

10.5194/egusphere-egu21-15908 ◽

2021 ◽

Author(s):

Haichao Wang

Keyword(s):

Eastern China ◽

Field Measurements ◽

Ozone Production ◽

Nitrate Radical ◽

Peroxy Radicals ◽

Ozone Pollution ◽

Volatile Organic ◽

Secondary Aerosols ◽

Photochemical Ozone

Monoterpene plays an important role in the formation of secondary aerosols and ozone in the troposphere. However, the field characterization of monoterpene chemistry in ozone pollution is still very sparse. Here we report fast daytime oxidation of monoterpene by hydroxyl radical, nitrate radical and ozone based on field measurements in Eastern China. We find fast monoterpene oxidation produces peroxy radicals efficiently and enhances the photochemical ozone production largely with an additional 8.6 ppb of ozone production per day on average (14%), whose effect was even more important than that of isoprene chemistry in the analyzed dataset. We propose that the reduction of anthropogenic volatile organic compounds should be much more stringent in the presence of high monoterpenes to alleviating ozone pollution.

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Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

10.26434/chemrxiv.9729143 ◽

2019 ◽

Author(s):

Oriol Planas ◽

Feng Wang ◽

Markus Leutzsch ◽

Josep Cornella

Keyword(s):

Transition Metal ◽

Main Group ◽

Group Element ◽

Oxidation States ◽

Boron Compounds ◽

Main Text ◽

Main Group Element ◽

Rational Ligand Design ◽

Supplementary Material

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts. A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.

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Comparisons of observed and modeled OH and HO2concentrations during the ambient measurement period of the HOxComp field campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-2567-2012 ◽

2012 ◽

Vol 12 (5) ◽

pp. 2567-2585 ◽

Cited By ~ 23

Author(s):

Y. Kanaya ◽

A. Hofzumahaus ◽

H.-P. Dorn ◽

T. Brauers ◽

H. Fuchs ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Chemical Mechanism ◽

Ozone Production ◽

High Yield ◽

Base Case ◽

Peroxy Radicals ◽

Field Campaign ◽

Mixing Ratios ◽

Measurement Mode ◽

Single Instrument

Abstract. A photochemical box model constrained by ancillary observations was used to simulate OH and HO2 concentrations for three days of ambient observations during the HOxComp field campaign held in Jülich, Germany in July 2005. Daytime OH levels observed by four instruments were fairly well reproduced to within 33% by a base model run (Regional Atmospheric Chemistry Mechanism with updated isoprene chemistry adapted from Master Chemical Mechanism ver. 3.1) with high R2 values (0.72–0.97) over a range of isoprene (0.3–2 ppb) and NO (0.1–10 ppb) mixing ratios. Daytime HO2(*) levels, reconstructed from the base model results taking into account the sensitivity toward speciated RO2 (organic peroxy) radicals, as recently reported from one of the participating instruments in the HO2 measurement mode, were 93% higher than the observations made by the single instrument. This also indicates an overprediction of the HO2 to OH recycling. Together with the good model-measurement agreement for OH, it implies a missing OH source in the model. Modeled OH and HO2(*) could only be matched to the observations by addition of a strong unknown loss process for HO2(*) that recycles OH at a high yield. Adding to the base model, instead, the recently proposed isomerization mechanism of isoprene peroxy radicals (Peeters and Müller, 2010) increased OH and HO2(*) by 28% and 13% on average. Although these were still only 4% higher than the OH observations made by one of the instruments, larger overestimations (42–70%) occurred with respect to the OH observations made by the other three instruments. The overestimation in OH could be diminished only when reactive alkanes (HC8) were solely introduced to the model to explain the missing fraction of observed OH reactivity. Moreover, the overprediction of HO2(*) became even larger than in the base case. These analyses imply that the rates of the isomerization are not readily supported by the ensemble of radical observations. One of the measurement days was characterized by low isoprene concentrations (∼0.5 ppb) and OH reactivity that was well explained by the observed species, especially before noon. For this selected period, as opposed to the general behavior, the model tended to underestimate HO2(*). We found that this tendency is associated with high NOx concentrations, suggesting that some HO2 production or regeneration processes under high NOx conditions were being overlooked; this might require revision of ozone production regimes.

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