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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NiH8S2(NO2)4 by Materials Project

Ni(SO4)2(NH2)4 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of four ammonia molecules and one Ni(SO4)2 ribbon oriented in the (1, 0, 0) direction. In the Ni(SO4)2 ribbon, Ni2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.03 Å) and two longer (2.08 Å) Ni–O bond lengths. S2- is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.47–1.52 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Ni2+ and one S2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ni2+ and one S2- atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one S2- atom.

36 MATERIALS SCIENCE↗
NASA NTRS2024

Satellite NO 2 Trends and Hotspots Over Offshore Oil and Gas Operations in the Gulf of Mexico

The Outer Continental Shelf of the Gulf of Mexico (GOM) is populated with numerous oil and natural gas (ONG) platforms which produce NO x (NO x = NO + NO 2 ), a major component of air pollution. The Bureau of Ocean Energy Management (BOEM) is mandated to ensure that the air quality of coastal states is not degraded by these emissions. As part of a NASA-BOEM collaboration, we conducted a satellite data-based analysis of nitrogen dioxide (NO 2 ) patterns and trends in the GOM. Data from the OMI and TROPOMI sensors were used to obtain 18+ year records of tropospheric column (TrC) NO 2 in three GOM regions: (a) Houston urban area, (b) near shore area off the Louisiana coast, and a (c) deepwater area off the Louisiana coast. The 2004–2022 time series show a decreasing trend for the urban (−0.027 DU/decade) and near shore (−0.0022 DU/decade) areas, and an increasing trend (0.0019 DU/decade) for the deepwater area. MERRA-2 wind and TROPOMI NO 2 data were used to reveal several NO2 hotspots (up to 25% above background values) under calm wind conditions near individual platforms. The NO 2 signals from these deepwater platforms and the high density of shallow water platforms closer to shore were confirmed by TrC NO 2 anomalies of up to 10%, taking into account the monthly TrC NO 2 climatology over the GOM. The results presented in this study establish a baseline for future estimates of emissions from the ONG hotspots and provide a methodology for analyzing NO 2 measurements from the new geostationary TEMPO instrument.

NO2↗
DOE OSTI2020

Materials Data on LiH4(NO2)3 by Materials Project

(LiH4(NO3)2)2N2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four ammonia molecules and four LiH4(NO3)2 clusters. In each LiH4(NO3)2 cluster, Li1+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are two shorter (1.97 Å) and two longer (2.06 Å) Li–O bond lengths. N+2.33+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.26 Å) N–O bond length. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Li1+ and one N+2.33+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+ and two H1+ atoms. In the third O2- site, O2- is bonded in a single-bond geometry to one N+2.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuH14C4(NO2)4 by Materials Project

CuH6(CO3)2(CO(NH2)2)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four formylhydrazine molecules and one CuH6(CO3)2 sheet oriented in the (1, 0, 0) direction. In the CuH6(CO3)2 sheet, Cu2+ is bonded in a distorted octahedral geometry to six O2- atoms. There are a spread of Cu–O bond distances ranging from 2.02–2.62 Å. C3+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.10 Å. Both C–O bond lengths are 1.27 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C3+ atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one Cu2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Cu2+ and one C3+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cu2+ and one C3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TeH14C2(NO2)4 by Materials Project

(CO(NH2)2)2Te(OH)6 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight urea molecules and four Te(OH)6 clusters. In each Te(OH)6 cluster, there are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the second H1+ site, H1+ is bonded in a distorted single-bond geometry to one O2- atom. The H–O bond length is 1.01 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. Te6+ is bonded in an octahedral geometry to six O2- atoms. There is four shorter (1.94 Å) and two longer (1.98 Å) Te–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one H1+ and one Te6+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one H1+ and one Te6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one H1+ and one Te6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoH8S2(NO2)4 by Materials Project

Co(SO4)2(NH2)4 crystallizes in the triclinic P1 space group. The structure is one-dimensional and consists of four ammonia molecules and one Co(SO4)2 ribbon oriented in the (1, 0, 0) direction. In the Co(SO4)2 ribbon, Co2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Co–O bond distances ranging from 2.03–2.08 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.47–1.53 Å. In the second S2- site, S2- is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of S–O bond distances ranging from 1.47–1.52 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Co2+ and one S2- atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Co2+ and one S2- atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Co2+ and one S2- atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Co2+ and one S2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one S2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba3Ir2(NO2)12 by Materials Project

Ba3(N5O12)2(IrN)2 crystallizes in the tetragonal P-4m2 space group. The structure is three-dimensional and consists of two IrN clusters and one Ba3(N5O12)2 framework. In each IrN cluster, Ir4+ is bonded in a single-bond geometry to one N+2.83+ atom. The Ir–N bond length is 1.68 Å. N+2.83+ is bonded in a single-bond geometry to one Ir4+ atom. In the Ba3(N5O12)2 framework, there are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are four shorter (2.92 Å) and eight longer (3.10 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded to eight equivalent O2- atoms to form edge-sharing BaO8 hexagonal bipyramids. All Ba–O bond lengths are 2.89 Å. In the third Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form edge-sharing BaO12 cuboctahedra. There are four shorter (2.86 Å) and eight longer (2.96 Å) Ba–O bond lengths. There are two inequivalent N+2.83+ sites. In the first N+2.83+ site, N+2.83+ is bonded in a distorted trigonal pyramidal geometry to four equivalent O2- atoms. All N–O bond lengths are 1.95 Å. In the second N+2.83+ site, N+2.83+ is bonded in a water-like geometry to two O2- atoms. There is one shorter (1.29 Å) and one longer (1.52 Å) N–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+ and two N+2.83+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Ba2+ and one O2- atom. The O–O bond length is 1.32 Å. In the third O2- site, O2- is bonded in an L-shaped geometry to two equivalent N+2.83+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to two Ba2+ and one O2- atom. The O–O bond length is 1.31 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnH20C2S2(NO2)6 by Materials Project

MnH8(SO6)2(CN3H6)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two guanidinium molecules and one MnH8(SO6)2 cluster. In the MnH8(SO6)2 cluster, Mn2+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with two equivalent SO4 tetrahedra. There are four shorter (2.18 Å) and two longer (2.25 Å) Mn–O bond lengths. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. S2- is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one MnO6 octahedra. The corner-sharing octahedral tilt angles are 31°. There is two shorter (1.49 Å) and two longer (1.50 Å) S–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted water-like geometry to one Mn2+ and two H1+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn2+ and one S2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the sixth O2- site, O2- is bonded in a distorted water-like geometry to one Mn2+ and two H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NpCoS2(NO2)6 by Materials Project

(Np(SO5)2)2(CoN3)2(N2)3(O2)2 crystallizes in the orthorhombic Pnma space group. The structure is one-dimensional and consists of four azanide;cobalt(3+) molecules; four triaziridine molecules; two Np(SO5)2 ribbons oriented in the (1, 0, 0) direction; and two O2 ribbons oriented in the (1, 0, 0) direction. In each Np(SO5)2 ribbon, Np4+ is bonded to seven O2- atoms to form distorted NpO7 pentagonal bipyramids that share corners with three equivalent SO4 tetrahedra and an edgeedge with one SO4 tetrahedra. There are a spread of Np–O bond distances ranging from 1.77–2.46 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to four O2- atoms to form SO4 tetrahedra that share corners with three equivalent NpO7 pentagonal bipyramids. There are a spread of S–O bond distances ranging from 1.43–1.52 Å. In the second S2- site, S2- is bonded to four O2- atoms to form SO4 tetrahedra that share an edgeedge with one NpO7 pentagonal bipyramid. There is two shorter (1.46 Å) and two longer (1.53 Å) S–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Np4+ and one S2- atom. In the second O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Np4+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one Np4+ and one S2- atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Np4+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one S2- atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Np4+ and one S2- atom. In each O2 ribbon, there are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two equivalent O2- atoms. Both O–O bond lengths are 1.61 Å. In the second O2- site, O2- is bonded in a linear geometry to two equivalent O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag3C(NO2)3 by Materials Project

AgCN(AgNO3)2 crystallizes in the monoclinic Pc space group. The structure is three-dimensional and consists of two AgCN ribbons oriented in the (1, 0, 0) direction and one AgNO3 framework. In each AgCN ribbon, Ag1+ is bonded in a distorted linear geometry to one C4+ and one N+1.67+ atom. The Ag–C bond length is 2.05 Å. The Ag–N bond length is 2.10 Å. C4+ is bonded in a linear geometry to one Ag1+ and one N+1.67+ atom. The C–N bond length is 1.18 Å. N+1.67+ is bonded in a linear geometry to one Ag1+ and one C4+ atom. In the AgNO3 framework, there are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ag–O bond distances ranging from 2.49–2.92 Å. In the second Ag1+ site, Ag1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ag–O bond distances ranging from 2.47–2.93 Å. There are two inequivalent N+1.67+ sites. In the first N+1.67+ site, N+1.67+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.26–1.28 Å. In the second N+1.67+ site, N+1.67+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.26 Å) and two longer (1.28 Å) N–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three Ag1+ and one N+1.67+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Ag1+ and one N+1.67+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N+1.67+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N+1.67+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ag1+ and one N+1.67+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N+1.67+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2Pd(NO2)4 by Materials Project

Pd(AgN2O4)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four palladium molecules and one AgN2O4 framework. In the AgN2O4 framework, there are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ag–O bond distances ranging from 2.38–2.81 Å. In the second Ag1+ site, Ag1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ag–O bond distances ranging from 2.50–3.14 Å. There are four inequivalent N3+ sites. In the first N3+ site, N3+ is bonded in a distorted bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.26 Å) N–O bond length. In the second N3+ site, N3+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.27 Å) N–O bond length. In the third N3+ site, N3+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.26 Å) N–O bond length. In the fourth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.26 Å) N–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two Ag1+ and one N3+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Ag1+ and one N3+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N3+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to two Ag1+ and one N3+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one N3+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two Ag1+ and one N3+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to two Ag1+ and one N3+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Submillimeter and millimeter observations of solar system objects

Microwave spectroscopy of solar system objects was supported. It necessarily involves millimeter and submillimeter wavelengths where rotational transitions reside. The existing national facilities are at OVRO, the 12-meter at Kitt Peak, UC array at Hat Creek, the Caltech CSO on Mauna Kea, and the 14-meter at the Univ. of Massachusetts, near Amherst. The group used all of these instruments in the last year except the Univ. of Massachusetts 14-meter. This wavelength range (0.3 to 3 mm) is about to enjoy an explosion of interest as submillimeter receivers become better and easier to use. This region of the spectrum is rich in transitions of molecules that exist in the planetary atmospheres which can be studied for temperature-pressure profiles, wind tracers, and atmospheric chemistry. The list of solar system objects that have been recently addressed with these techniques include: (1) Venus: CO studies of T-P profiles, winds, and photochemistry; SO2 detections; Continuum mapping remains to be done at 1 mm; (2) Earth H2O, CO, NO, NO2, O(18)O, etc. as a test bed for other atmospheres; (3) Mars: H2O, CO, O(18)O studies of T-P profiles, winds (fall of 1990), and photochemistry; (4) Saturn: Same as Jupiter plus submillimeter and millimeter mapping of the ring system; (5) Uranus and Neptune: Continuum thermal mapping; and (6) Titan: CO, HCN, and HC3NT-P information and photochemistry. Recent results are given.

Muhleman, Duane O.↗
NASA NTRS1990

An airborne compatible photofragmentation two-photon laser-induced fluorescence instrument for measuring background tropospheric levels of NO, NO(x), and NO2

The operating principle, design, and performance of a two-photon LIF (TP-LIF) sensor for simultaneous measurements of NO, NO(x) (NO + NO2), and NO2 are described. In this instrument, NO is first measured by direct spectroscopic TP-LIF detection; NO2 is converted to NO by photofragmentation using an XeF excimer laser operating at 353 nm; and the resulting NO is then detected quantitatively by TP-LIF. The detection limits of the instrument are found to be 3.5 parts per trillion by volume (pptv) of NO and 10 pptv for NO2, with integration times of 2 and 6 min, respectively. The in-flight performance of the instrument was evaluated during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 program in summer 1986, as reported by Gregory et al. (1990).

Sandholm, S. T.↗
NASA NTRS1999

Prebiotic Nitrogen Fixation by FeS Reduction of Nitrite Under Acidic Conditions

Theories for the origin of life require the availability of reduced nitrogen for the formation of such species as amino acid and nucleic acids. In a strongly reducing atmosphere, compounds essential to the chemical evolution of life, such as amino acids, can form by reactions between HCN, NH3, and carbonyl compounds produced in spark discharges. However, under non-reducing atmospheres, electric discharges produced NO rather than HCN or NH3. This raises the questions of; how ammonia can be formed under a neutral atmosphere, and what conditions are needed such formation to occur? On possibility is the conversion of NO into nitric and nitrous acids (through HNO) and rained into the oceans. The reduction of nitrite by aqueous Fe(II) (6 Fe(+2) + 7 H(+) + NO2(-) yields 6 Fe(III) + 2 H2O + NH3) such as was present on the early Earth could then have produced ammonia. However, this reaction does not proceed at pHs less than 7.3. An alternative is reduction by other forms of Fe(II), such as FeS. We will present results that show that FeS can reduce nitrite to ammonia at pHs as low as pH 5 under a variety of conditions.

Summers, David P.↗
NASA NTRS2016

An Observationally Constrained Evaluation of the Oxidative Capacity in the Tropical Western Pacific Troposphere

Hydroxyl radical (OH) is the main daytime oxidant in the troposphere and determines the atmospheric lifetimes of many compounds. We use aircraft measurements of O3, H2O, NO, and other species from the Convective Transport of Active Species in the Tropics (CONTRAST) field campaign, which occurred in the tropical western Pacific (TWP) during January-February 2014, to constrain a photochemical box model and estimate concentrations of OH throughout the troposphere. We find that tropospheric column OH (OHCOL) inferred from CONTRAST observations is 12 to 40% higher than found in chemical transport models (CTMs), including CAM-chem-SD run with 2014 meteorology as well as eight models that participated in POLMIP (2008 meteorology). Part of this discrepancy is due to a clear-sky sampling bias that affects CONTRAST observations; accounting for this bias and also for a small difference in chemical mechanism results in our empirically based value of OHCOL being 0 to 20% larger than found within global models. While these global models simulate observed O3 reasonably well, they underestimate NOx (NO +NO2) by a factor of 2, resulting in OHCOL approx.30% lower than box model simulations constrained by observed NO. Underestimations by CTMs of observed CH3CHO throughout the troposphere and of HCHO in the upper troposphere further contribute to differences between our constrained estimates of OH and those calculated by CTMs. Finally, our calculations do not support the prior suggestion of the existence of a tropospheric OH minimum in the TWP, because during January-February 2014 observed levels of O3 and NO were considerably larger than previously reported values in the TWP.

Hydroxyl radical↗
DOE OSTI2020

Materials Data on H8(NO2)3 by Materials Project

(NH4)4(NO3)2(O2)3 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of two ammonium molecules, one peroxynitrous acid molecule, and one trioxidane molecule.

36 MATERIALS SCIENCE↗
NASA NTRS2020

Revisiting the Effectiveness Of HCHO/NO2 Ratios for Inferring Ozone Sensitivity to Its Precursors Using High Resolution Airborne Remote Sensing Observations in A High Ozone Episode During the KORUS-AQ Campaign

The nonlinear chemical processes involved in ozone production (P(O3)) have necessitated using proxy indicators to convey information about the primary dependence of P(O3) on volatile organic compounds (VOCs) or nitrogen oxides (NOx). In particular, the ratio of remotely sensed columns of formaldehyde (HCHO) to nitrogen dioxide (NO2) has been widely used for studying O3 sensitivity. Previous studies found that the errors in retrievals and the incoherent relationship between the column and the near-surface concentrations are a barrier in applying the ratio in a robust way. In addition to these obstacles, we provide calculational-observational evidence, using an ensemble of 0-D photochemical box models constrained by DC-8 aircraft measurements on an ozone event during the Korea-United States Air Quality (KORUS-AQ) campaign over Seoul, to demonstrate the chemical feedback of NO2 on the formation of HCHO is a controlling factor for the transition line between NOx-sensitive and NOx-saturated regimes. A fixed value (~2.7) of the ratio of the chemical loss of NOx (LNOx) to the chemical loss of HO2+RO2 (LROx) perceptibly differentiates the regimes. Following this value, data points with a ratio of HCHO/NO2 less than 1 can be safely classified as NOx-saturated regime, whereas points with ratios between 1 and 4 fall into one or the other regime. We attribute this mainly to the HCHO-NO2 chemical relationship causing the transition line to occur at larger (smaller) HCHO/NO2 ratios in VOC-rich (VOC-poor) environments. We then redefine the transition line to LNOx/LROx~2.7 that accounts for the HCHO-NO2 chemical relationship leading to HCHO = 3.7 × (NO2 – 1.14 × 1016 molec.cm-2). Although the revised formula is locally calibrated (i.e., requires for readjustment for other regions), its mathematical format removes the need for having a wide range of thresholds used in HCHO/NO2 ratios that is a result of the chemical feedback. Therefore, to be able to properly take the chemical feedback into consideration, the use of HCHO = a × (NO2 – b) formula should be preferred to the ratio in future works. We then use the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument to study O3 sensitivity in Seoul. The unprecedented spatial (250 × 250 m2) and temporal (~every 2 h) resolutions of HCHO and NO2 observations form the sensor enhance our understanding of P(O3) in Seoul; rather than providing a crude label for the entire city, more in-depth variabilities in chemical regimes are observed that should be able to inform mitigation strategies correspondingly.

KORUS-AQ; formaldehyde; NOx; VOC; OMI; GeoTASO; oz↗
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↗