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NASA NTRS2020

High Resolution Global Coupled Chemistry-Meteorology Simulations Using the NASA GEOS Composition Forecast System, GEOS-CF

We will give an overview of the NASA Global Earth Observing System Composition Forecast system (GEOS-CF), a high-resolution (0.25 degree) global composition model developed by the NASA Global Modeling and Assimilation Office (GMAO). This system combines the GEOS weather and aerosol model with the GEOS-Chem chemistry module (version 12) to provide a holistic view of atmospheric composition that captures a wide range of air pollutants such as ozone, nitrogen oxides, volatile organic compounds, and fine particulate matter. The spatial resolution of 0.25 degrees (approx. 25 km) is fine enough to resolve local features such as nighttime ozone titration previously resolved only by urban or regional models. Furthermore, since there are no boundary conditions for a global model, the GEOS-CF captures large-scale processes such as long-range transport of air pollutants from forest fires. Comparisons against surface observations highlight the model’s overall capability to reproduce the diurnal variability of air pollutants under a variety of meteorological conditions. In addition, we show how machine learning techniques can be used to correct for sub-grid variability, which further improves model estimates at a given surface observation site. The GEOS-CF system offers a new tool for scientists and the public health community alike and is being developed jointly with several government and non-profit partners. As an example, we will show the use of GEOS-CF during the Satellite Coastal and Oceanic Atmospheric Pollution Experiment (SCOAPE). The campaign, conducted in collaboration between NASA and the Bureau of Ocean Energy Management (BOEM), aims to investigate the response of onshore air quality to Outer Continental Shelf (OCS) oil and gas exploration, development and production. Detailed gas-phase chemistry, as provided by GEOS-CF, is critical to understand the formation of air pollution related to hydrocarbon emissions from offshore oil and gas activities. The accuracy of GEOS-CF can be further improved by incorporating detailed offshore emissions compiled by BOEM.

Knowland, K. Emma↗
NASA NTRSDate not supplied

Impact of COVID-19 Restrictions on Atmospheric Concentrations of O3 and NO2 Across the Globe

We use a machine learning algorithm combining information from the NASA GEOS composition forecast (GEOS-CF) model and surface observations of nitrogen dioxide (NO2) and ozone (O3) at more than 5,000 observation sites to assess the impact of COVID-19 restrictions on surface air quality in 46 countries. Our methodology removes the compounding impacts of meteorology, seasonality and atmospheric chemistry on air pollution, thus allowing for a quantitative estimate of the change in surface air quality following COVID-19 containment measures. Compared to GEOS-CF model predictions that do not include emission reductions related to COVID-19 restrictions, surface observations show a drop in surface NO2 of up to 60% after the implementation of lockdowns. Average NO2 concentrations between February 2020 to June 2020 were 18% lower than business as usual. The earliest and strongest declines are observed over China, followed by Europe and the US. While NO2 concentrations over China recovered within 2 months, the recovery has been slower over Europe and the US. The impact of COVID-19 restrictions on O3 is complicated by non-linear atmospheric chemistry. Locally, O3 can show a short-term increase of up to 50% as a result of the decrease in NO2, which leads to a reduction in night time titration. However, this effect is offset by a decrease in photochemical production during the day. Our results indicate that these two competing processes resulted in a net zero change in average surface ozone during the first 5 months of the pandemic. The results also indicate that the reduced photochemical production becomes increasingly important over time. Our analysis is based on surface observations and model simulations available in near real-time, and we will present an up-to-date view of the short and medium-term impacts of COVID-19 restrictions on air quality around the world.

COVID-19↗
NASA NTRS2021

Global Impact of COVID-19 Restrictions on the Atmospheric Concentrations of Nitrogen Dioxide and Ozone

Social-distancing to combat the COVID-19 pandemic has led to widespread reductions in air pollutant emissions. Quantifying these changes requires a business-as-usual counterfactual that accounts for the synoptic and seasonal variability of air pollutants. We use a machine learning algorithm driven by information from the NASA GEOS-CF model to assess changes in nitrogen dioxide (NO2) and ozone (O3) at 5,756 observation sites in countries from January through June 2020. Reductions in NO2 coincide with timing and intensity of COVID-19 restrictions, ranging from 60% in severely affected cities (e.g., Wuhan, Milan) to little change (e.g., Rio de Janeiro, Taipei). On average, NO2 concentrations were (13-23) % lower than business as usual from February 2020 onward. China experienced the earliest and steepest decline, but concentrations since April have mostly recovered and remained within 5% to the business-as-usual estimate. NO2 reductions in Europe and the US have been more gradual with a halting recovery starting in late March. We estimate that the global NOx (NO+NO2) emission reduction during the first 6 months of 2020 amounted to 3.1 (2.6-3.6) TgN, equivalent to 5.5(4.7-6.4) % of the annual anthropogenic total. The response of surface O3 is complicated by competing influences of non-linear atmospheric chemistry. While surface O3 increased by up to 50% in some locations, we find the overall net impact on daily average O3 between February -June 2020 to be small. However, our analysis indicates a flattening of the O3 diurnal cycle with an increase in nighttime ozone due to reduced titration and a decrease in daytime ozone, reflecting a reduction in photochemical production.

Christoph A Keller↗
NASA NTRS2021

The impact of Los Angeles Basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models

In this work, the impact of Los Angeles Basin pollution transport and stratospheric intrusions on the surface ozone levels observed in the San Gabriel Mountains is investigated based on a combination of surface and lidar measurements as well as WRF-Chem (Weather Research and Forecasting with Chemistry) and WACCM (Whole Atmosphere Community Climate Model) runs. The number of days with observed surface ozone levels exceeding the National Ambient Air Quality Standards exhibit a clear seasonal pattern, with a maximum during summer, when models suggest a minimum influence of stratospheric intrusions and the largest impact from Los Angeles Basin pollution transport. Additionally, measured and modeled surface ozone and PM10 were analyzed as a function of season, time of the day, and wind direction. Measurements and models are in good qualitative agreement, with maximum surface ozone observed for southwest and west winds. For the prevailing summer wind direction, slightly south of the ozone maximum and corresponding to south-southwest winds, lower ozone levels were observed. Back trajectories suggest that this is associated with transport from the central Los Angeles Basin, where titration limits the amount of surface ozone. A quantitative comparison of the lidar profiles with WRF-Chem and WACCM models revealed good agreement near the surface, with models showing an increasing positive bias as function of altitude, reaching 75 % at 15 km above sea level. Finally, three selected case studies covering the different mechanisms affecting the near-surface ozone concentration over the San Gabriel Mountains, namely stratospheric intrusions and pollution transport, are analyzed based on surface and ozone lidar measurements, as well as co-located ceilometer measurements and models.

Impact↗
NASA NTRSDate not supplied

Formaldehyde Column Density as an Indicator for Elevated Surface Ozone

Efforts to observe near-surface ozone directly from space are hindered by the limited sensitivity of ozone satellite retrievals to the lower troposphere. Formaldehyde (HCHO) column observations from the NASA DISCOVER-AQ campaign showed a strong relationship with surface ozone, particularly when biogenic volatile organic compounds (VOCs) were the dominant ozone precursor due to their strong temperature-driven variability. Both tropospheric ozone and HCHO are secondarily produced through the oxidation of VOCs and in regions where the main fate of RO2 is reaction with NO, thus formaldehyde and ozone are generally co-produced. This work explores the relationship between column formaldehyde and surface ozone using data from two air quality research campaigns, the Long Island Sound Tropospheric Ozone Study (LISTOS) in 2018 and the Korea U.S. - Air Quality (KORUS-AQ) campaign in 2016. These campaigns included HCHO column information from airborne in-situ profiling and remote sensing and ground-based Pandora spectrometers in combination with surface ozone monitors in each region. These data are used to further explore the HCHO-ozone relationship and its potential for identifying areas of elevated ozone using remote sensing or satellite observations of column HCHO alone. These two regions offer a valuable comparison given their different VOC mixtures and the higher NOx levels in Seoul that result in ozone titration effects. This work will also address the potential for this application with future geostationary satellite observations.

Laura Margaret Judd↗
NASA NTRSDate not supplied

Results of the Field Test and Defining Sensormotor Fitness for Duty Standards

The primary goals of the Field Test were (1) to determine functional abilities associated with long-duration space flight crews beginning as soon after landing as possible (< 2 hours), and (2) to characterize the time course of recovery with additional follow-up measurement sessions within 24 hours after landing. The NASA and Russian teams have collected data on a total of 39 different United States Orbital Segment (USOS) and Russian crewmembers, with 9 Russian crewmembers being tested twice (total of 48 tests). Eighteen subjects (7 Russian, 11 USOS) completed a reduced Field Test (pilot) protocol and 30 subjects (19 Russian and 11 USOS) participated in the full Field Test. This presentation will focus on a subset of the measures that will be used in the upcoming ground study to determine sensorimotor fitness for duty standards, namely: tandem walk, obstacle walk, eye-hand coordination task, finger-to-nose task, and Computerized Dynamic Posturography (CDP). Exploration-class missions including Artemis, Gateway, and beyond will require a new level of autonomy around periods of gravitational transition, where sensorimotor disturbances increase. The operational support that is available upon return to Earth including rescue teams, medical interventions, and the ability to rest as needed will not be available after landing on the lunar or Martian surface. Because of this, there is a need to define fitness for duty standards that will help inform crew capabilities during and soon after gravitational transitions. Due to the new requirements of the exploration environment, we must utilize a set of exploration field measures, for which no previous spaceflight data exists to define fitness for duty standards. A Sensorimotor Adaptation Analog (SAA) that can provide different levels of acute disorientation through combined vestibular, visual, and proprioceptive disruptions will be used to increase the range of performance in exploration field measures, simulating the moderate-to-severe performance decrements observed in spaceflight. The levels of SAA will be titrated and validated by comparison to gold standard measures that have a wealth of spaceflight data at different time points during recovery. These data will be pulled directly from the results of Field Test and help ensure the range of performance while being exposed to SAA mimics the range of performance from pre-flight to immediately postflight in Field Test subjects. Specifically, we will be using the tandem walk, obstacle walk, eye-hand coordination task, finger-to-nose task, and CDP as the gold standard measures. Referencing this Field Test data in the form of gold standard measures will also help us characterize and contextualize how each magnitude of SAA disorientation compares to recovery from long-term microgravity exposure.

M J F Rosenberg↗
NASA NTRS2022

Limitations in Representation of Physical Processes Prevents Successful Simulation of PM2.5 During KORUS-AQ

High levels of fine particulate matter (PM2.5) pollution in East Asia often exceed local air quality standards. Observations from the Korea United States-Air Quality (KORUS-AQ) field campaign in May and June 2016 showed that development of extreme pollution (haze) occurred through a combination of long-range transport and favorable meteorological conditions that enhanced local production of PM2.5. Atmospheric models often have difficulty simulating PM2.5 chemical composition during haze, which is of concern for the development of successful control measures. We use observations from KORUS-AQ to examine the ability of the GEOS-Chem chemical transport model to simulate PM2.5 composition throughout the campaign and identify the mechanisms driving the pollution event. At the surface, the model underestimates sulfate by -64% but overestimates nitrate by +36%. The largest underestimate in sulfate occurs during the pollution event, where models typically struggle to generate elevated sulfate concentrations due to missing heterogeneous chemistry in aerosol liquid water in the polluted boundary layer. Hourly surface observations show that the model nitrate bias is driven by an overestimation of the nighttime peak. In the model, nitrate formation is limited by the supply of nitric acid, which is biased by +100% against aircraft observations. We hypothesize that this is due to a large missing sink, which we implement here as a factor of five increase in dry deposition. We show that the resulting increased deposition velocity is consistent with observations of total nitrate as a function of photochemical age. The model does not account for factors such as the urban heat island effect or the heterogeneity of the built-up urban landscape resulting in insufficient model turbulence and surface area over the study area that likely results in insufficient dry deposition. Other species such as NH3 could be similarly affected but were not measured during the campaign. Nighttime production of nitrate is driven by NO2 hydrolysis in the model, while observations show that unexpectedly elevated nighttime ozone (not present in the model) should result in N2O5 hydrolysis as the primary pathway. The model is unable to represent nighttime ozone due to an overly rapid collapse of the afternoon mixed layer and excessive titration by NO. We attribute this to missing nighttime heating driving deeper nocturnal mixing that would be expected to occur in a city like Seoul. This urban heating is not considered in air quality models run at large enough scales to treat both local chemistry and long-range transport. Key model failures in simulating nitrate, mainly overestimated daytime nitric acid, incorrect representation of nighttime chemistry, and an overly shallow and insufficiently turbulent nighttime mixed layer, exacerbate the model’s inability to simulate the buildup of PM2.5 during haze pollution. To address the underestimate in sulfate most evident during the haze event, heterogeneous aerosol uptake of SO2 is added to the model which previously only considered aqueous production of sulfate from SO2 in cloud water. Implementing a simple parameterization of this chemistry improves the model abundance of sulfate but degrades the SO2 simulation implying that emissions are underestimated. We find that improving model simulations of sulfate has direct relevance to determining local vs. transboundary contributions to PM2.5. During the haze pollution event, the inclusion of heterogeneous aerosol uptake of SO2 decreases the fraction of PM2.5 attributable to long-range transport from 66% to 54%. Locally-produced sulfate increased from 1% to 25% of locally-produced PM2.5, implying that local emissions controls would have a larger effect than previously thought. However, this additional uptake of SO2 is coupled to the model nitrate prediction which affects the aerosol liquid water abundance and chemistry driving sulfate-nitrate-ammonium partitioning. An additional simulation of the haze pollution with heterogeneous uptake of SO2 to aerosol and simple improvements to the model nitrate simulation results in 30% less sulfate due to 40% less nitrate and aerosol water, and results in an underestimate of sulfate during the haze event. Future studies need to better consider the impact of model physical processes such as dry deposition and nighttime boundary layer mixing on the simulation of nitrate and the effect of improved nitrate simulations on the overall simulation of secondary inorganic aerosol (sulfate+nitrate+ammonium) in East Asia. Foreign emissions are rapidly changing, increasing the need to understand the impact of local emissions on PM2.5 in South Korea to ensure continued air quality improvements.

Katherine R. Travis↗
NASA NTRSDate not supplied

Assessments of Physiology And Cognition in Hybrid-reality Environments (APACHE) – Physical Workload Approximation

The Human Physiology, Performance, Protection & Operations Laboratory (H-3PO) at NASA Johnson Space Center (JSC) is developing a hybrid reality exploration surface analog, “Assessments of Physiology and Cognition in Hybrid-reality Environments” (APACHE). The goal of APACHE is to create a planetary extravehicular activity (EVA) simulation environment that provides a representative physical and cognitive workload approximation using a combination of virtual reality (VR), physical reality, and hybrid reality (HR) techniques. To develop and characterize the physical workload approximation within the APACHE environment, a two-part approach was implemented. In part 1, baseline physical work load during ambulation within APACHE was evaluated and compared with that in other planetary EVA analog environments and with existing data sets from Apollo planetary EVAs and reduced gravity testing of prototype planetary spacesuits. For this evaluation, 10 subjects were asked to ambulate in three surface analog environments: a passive treadmill in APACHE, natural terrain in an outdoor field environment, and a standard motorized treadmill. Subjects’ heart rate and metabolic rate (VO2/VCO2) were measured and compared among the different test conditions and existing data sets. Gait parameters were also collected to compare with suited mechanics and to understand the role of gait kinematics in physical workload. In part 2, the aim is to evaluate the addition of a custom weighted body suit to the aforementioned surface analog environments and the ability to titrate the suit configuration to provide the best possible physical workload approximation for simulation of lunar and Martian EVAs.

Alex Baughman↗
NASA NTRSDate not supplied

Preliminary Results Using Galvanic Vestibular Reduction as a Non-Pharmaceutical Tool for Motion Sickness Mitigation

Introduction: Alterations in vestibular sensory processing following G-transitions lead to motion sickness and spatial disorientation upon return to Earth’s gravity. The use of non-pharmaceutical mitigation for motion sickness has several potential advantages over drug treatment options. The purpose of this study was to validate a non-pharmaceutical tool using galvanic vestibular reduction (GVR) to mitigate G-transitional induced motion sickness and spatial disorientation. Methods: Using a repeated measures counter-balanced design, motion sickness and perception are obtained during Coriolis cross-coupling stimuli on a rotating chair across three GVR treatment interventions: throughout stimulus testing (prevention), following symptom onset (rescue), and placebo control. Subjects perform up to 10 sets of pitch head movements during constant rotation. For each set, head movement is cued every 10 seconds, alternating between pitch forward (chin resting to chest) and pitch backward (head upright) for a total of 7 forward and backward movements. During each head movement, subjects are asked to use a joystick to record the magnitude of their perceived rotation along all three axes. During the 2-minute pause between sets, motion sickness symptom scoring was obtained using the Pensacola Diagnostic Index and subject discomfort (0-20) ratings. Performance on a sensorimotor and cognitive test battery is measured during a fourth session to map changes in GVR level with functional performance. Results: Fifteen of 30 subjects have completed testing to date. Preliminary findings suggest GVR may be more effective in reducing symptoms in subjects who self-report less susceptibility on a pre-test motion sickness susceptibility questionnaire. Based on the joystick measures, GVR significantly reduces both the magnitude (mean 22% - 34%) and duration (mean 42% - 49%) of perceived roll and pitch sensation with head movements during constant rotation. It is important to note that comparable levels of GVR (up to 2.5mA) does not impair performance on a functional test battery including mobility and balance tasks. Discussion: Our preliminary findings suggest GVR may be useful in reducing disorienting roll and pitch illusions associated with Coriolis cross-coupling stimuli. While transfer to post-flight treatment will need to be validated, the potential advantages of our non-pharmaceutical countermeasure approach would be to provide rapid therapeutic effect while allowing continuous titration of GVR amplitude during recovery to maintain operational performance.

Gaurav Pradhan↗
NASA NTRSDate not supplied

Assessments of Physiology And Cognition in Hybrid-reality Environments (APACHE) – Physical Workload Approximation

The Human Physiology, Performance, Protection & Operations Laboratory (H-3PO) at NASA Johnson Space Center (JSC) is developing a hybrid reality exploration surface analog, “Assessments of Physiology And Cognition in Hybrid-reality Environments” (APACHE). The goal of APACHE is to create a planetary extravehicular activity (EVA) simulation environment that provides a representative physical and cognitive workload approximation using a combination of virtual reality (VR), physical reality, and hybrid reality (HR) techniques. To develop and characterize the physical workload approximation within the APACHE environment, a two-part approach was implemented. In part 1, baseline physical workload during ambulation within APACHE was evaluated and compared with that in other planetary EVA analog environments and with existing data sets from Apollo planetary EVAs and reduced gravity testing of prototype planetary spacesuits. For this evaluation, 10 subjects were asked to ambulate in three surface analog environments: a passive treadmill in APACHE, natural terrain in an outdoor field environment, and a standard motorized treadmill. Subjects’ heart rate and metabolic rate (VO2/VCO2)were measured and compared among the different test conditions and existing data sets. Gait parameters were also collected to compare with suited mechanics and to understand the role of gait kinematics in physical workload. In part 2, the aim is to evaluate the addition of a custom weighted body suit to the aforementioned surface analog environments and the ability to titrate the suit configuration to provide the best possible physical workload approximation for simulation of lunar and Martian EVAs.

Alexander J Baughman↗
NASA NTRS2023

Galvanic Vestibular Reduction Modifies Perception of Coriolis Cross-Coupling and Delays Motion Sickness Onset

INTRODUCTION: Alterations in vestibular sensory processing following G-transitions lead to head movement sensitivity and motion sickness upon return to Earth’s gravity. The purpose of this study was to evaluate whether a non-pharmaceutical tool using galvanic vestibular reduction (GVR) could suppress disorienting illusions and mitigate motion sickness. A similar approach using anodal (inhibitory) currents delivered to both ears has been shown to result in a selective reversible ablation of irregular vestibular afferents [1]. METHODS: Using a repeated measures counter-balanced design, motion sickness and perception were obtained in 26 subjects during Coriolis cross-coupling stimuli on a rotating chair across three GVR treatment interventions: throughout stimulus testing (prevention), following symptom onset (rescue), and placebo control. The GVR peak current was maintained at 2.5 mA across subjects and across prevention / rescue sessions. Subjects performed up to 10 sets of pitch head movements during constant rotation. For each set, head movement was cued every 10 seconds, alternating between pitch forward (chin resting to chest) and pitch backward (head upright) for a total of 7 forward and backward movements. During each head movement, subjects were asked to use a joystick to record the magnitude of their perceived rotation along three axes. During the 2-minute pause between sets, motion sickness symptom scoring was obtained using the Pensacola Diagnostic Index and subject discomfort (0-20) ratings. Performance on a sensorimotor and cognitive test battery was measured during a fourth session to map changes in GVR level with functional performance. RESULTS: Fourteen of the 26 subjects were not susceptible to the motion stressor (i.e., did not reach an endpoint in the control condition). While the time to endpoint, or number of head movements, did not significantly vary across the three GVR conditions in the remaining subjects, the symptom levels were significantly lower through the third set of head movements when GVR was on throughout the testing. Initiating GVR following symptom onset did not appear to alter the symptom progression nor time to motion sickness endpoint. Based on the joystick measures, GVR significantly modified the perceived roll and pitch sensation during head movements, reducing the amplitude of tilt in most subjects. It is important to note that comparable levels of GVR did not impair performance on a functional test battery including mobility, balance and cognitive tasks. DISCUSSION: Our findings suggest GVR may be useful in reducing disorienting roll and pitch illusions and delaying the onset of motion sickness. Further enhancements will be required to individualize the stimulation amplitude and optimize the waveform delivery. Adapting this non-pharmaceutical countermeasure approach to allow self-administered titration of current amplitude during recovery would enable transfer to post-flight treatment of motion sickness. [1] Minor L. B. and Goldberg J. M. (1991) J Neurosci 11, 1636-48. 109, 889-894.

G N Pradhan↗
NASA NTRS2005

A Kinetic and Product Study of the Cl + HO2 Reaction

Absolute rate data and product branching ratios for the reactions Cl + HO2 to HCl + O2 (k1a) and Cl + HO2 to OH + ClO (k1b) have been measured from 226 to 336 K at a total pressure of 1 Torr of helium using the discharge flow resonance fluorescence technique coupled with infrared diode laser spectroscopy. For kinetic measurements, pseudo-first-order conditions were used with both reagents in excess in separate experiments. HO2 was produced by two methods: through the termolecular reaction of H atoms with O2 and also by the reaction of F atoms with H2O2. Cl atoms were produced by a microwave discharge of Cl2 in He. HO2 radicals were converted to OH radicals prior to detection by resonance fluorescence at 308 nm. Cl atoms were detected directly at 138 nm also by resonance fluorescence. Measurement of the consumption of HO2 in excess Cl yielded k1a and measurement of the consumption of Cl in excess HO2 yielded the total rate coefficient, k1. Values of k1a and k1 derived from kinetic experiments expressed in Arrhenius form are (1.6 +/- 0.2) x 10-11 exp[(249 +/- 34)/T] and (2.8 +/- 0.1) x 10-11 exp[(123 +/- 15)/T] cm3 molecule-1 s-1, respectively. As the expression for k1 is only weakly temperature dependent, we report a temperature-independent value of k1 = (4.5 +/- 0.4) x 10-11 cm3 molecule-1 s-1. Additionally, an Arrhenius expression for k1b can also be derived: k1b = (7.7 +/- 0.8) x 10-11 exp[-(708 +/- 29)/T] cm3 molecule-1 s-1. These expressions for k1a and k1b are valid for 226 K T 336 and 256 K T 296 K, respectively. The cited errors are at the level of a single standard deviation. For the product measurements, an excess of Cl was added to known concentrations of HO2 and the reaction was allowed to reach completion. HCl product concentrations were determined by IR absorption yielding the ratio k1a/k1 over the temperature range 236 K T 296 K. OH product concentrations were determined by resonance fluorescence giving rise to the ratio k1b/k1 over the temperature range 226 K T 336 K. Both of these ratios were subsequently converted to absolute numbers. Values of k1a and k1b from the product experiments expressed in Arrhenius form are (1.5 +/- 0.1) x 10-11 exp[(222 +/- 17)/T] and (10.6 +/- 1.5) x 10-11 exp[-(733 +/- 41)/T] cm3 molecule-1 s-1, respectively. These expressions for k1a and k1b are valid for 256 K T 296 and 226 K T 336 K, respectively. A combination of the kinetic and product data results in the following Arrhenius expressions for k1a and k1b of (1.4 +/- 0.3) x 10-11 exp[(269 +/- 58)/T] and (12.7 +/- 4.1) x 10-11 exp[-(801 +/- 94)/T] cm3 molecule-1 s-1, respectively. Numerical simulations were used to check for interferences from secondary chemistry in both the kinetic and product experiments and also to quantify the losses incurred during the conversion process HO2 to OH for detection purposes.

rate constants↗