Nitrogen trifluoride global emissions estimated from updated atmospheric measurements

Revealing the global emission gaps for fully fluorinated greenhouse gases

In response to the global trend of climate change, it is important to accurately quantify emissions of fully fluorinated greenhouse gases (FFGHGs, referring to SF6/NF3/CF4/C2F6/C3F8/c-C4F8 here). Atmospheric observation-based top-down methods and activity-based bottom-up methods are usually used together to estimate FFGHG emissions at the global and regional levels. In this work, emission gaps at global and regional levels are discussed among top-down studies, between the top-down and bottom-up FFGHG emissions, and among bottom-up emissions. Generally, trends and magnitudes of individual FFGHG emissions among top-down estimates are close to each other within the uncertainties. However, global bottom-up inventories show discrepancies in FFGHG emissions among each other in trends and magnitudes. The differences in emission magnitudes are up to 93%, 90%, 88%, 83%, 87%, and 85% for SF6, NF3, CF4, C2F6, C3F8, and c-C4F8, respectively. Besides, we reveal the insufficient regional TD studies and the lack of atmospheric observation data/stations especially in areas with potential FFGHG emissions. We make recommendations regarding the best practices for improving our understanding of these emissions, including both top-down and bottom-up methods.

Fully fluorinated non-carbon compounds NF3 and SF6 as ideal technosignature gases

Waste gas products from technological civilizations may accumulate in an exoplanet atmosphere to detectable levels. We propose nitrogen trifluoride (NF3) and sulfur hexafluoride (SF6) as ideal technosignature gases. Earth life avoids producing or using any N-F or S-F bond-containing molecules and makes no fully fluorinated molecules with any element. NF3 and SF6 may be universal technosignatures owing to their special industrial properties, which unlike biosignature gases, are not species-dependent. Other key relevant qualities of NF3 and SF6 are: their extremely low water solubility, unique spectral features, and long atmospheric lifetimes. NF3 has no non-human sources and was absent from Earth's pre-industrial atmosphere. SF6 is released in only tiny amounts from fluorine-containing minerals, and is likely produced in only trivial amounts by volcanic eruptions. We propose a strategy to rule out SF6's abiotic source by simultaneous observations of SiF4, which is released by volcanoes in an order of magnitude higher abundance than SF6. Other fully fluorinated human-made molecules are of interest, but their chemical and spectral properties are unavailable. We summarize why life on Earth-and perhaps life elsewhere-avoids using F. We caution, however, that we cannot definitively disentangle an alien biochemistry byproduct from a technosignature gas.

Emissions of Tetrafluoromethane (CF4) and Hexafluoroethane (C2F6) From East Asia: 2008 to 2019

The perfluorocarbons (PFCs), tetrafluoromethane (CF₄) and hexafluoroethane (C₂F₆), are potent greenhouse gases with very long atmospheric lifetimes. They are emitted almost entirely from industrial sources, including the aluminum and rare earth metal smelting industries that emit them as by-products, and the semiconductor and flat panel display manufacturing industries that use them and vent unutilized amounts to the atmosphere. Despite extensive industrial efforts to quantify and curb these emissions, "top-down" PFC emission estimates derived from atmospheric measurements continue to rise and are significantly greater than reported process- and inventory-based "bottom-up" emissions. In this study, we estimate emissions of CF₄ and C₂F₆ from East Asia, where PFC emitting industries are heavily concentrated, using a top-down approach (a Bayesian inversion) with high-frequency atmospheric measurements at Gosan (Jeju Island, South Korea) for 2008-2019. We also compile and analyze the available bottom-up CF₄ and C₂F₆ emissions in East Asia from industrial and government reports. Our results suggest that the observed increases in global PFC emissions since 2015 are driven primarily by China's aluminum industry, with significant contributions from Japan's and Korea's semiconductor industry. Our analysis suggests that Chinese emissions occur predominantly from the aluminum industry, although their emissions per production ratio may be improving. Our results for Japan and Korea find significant discrepancies between top-down and bottom-up emissions estimates, suggesting that the effectiveness of emission reduction systems (abatement) used in their semiconductor industries may be overestimated. Overall, our top-down results for East Asia contribute significantly to reducing the gap in the global PFC emission budgets.

Silicon Oxide Etching Process of NF3 and F3NO Plasmas with a Residual Gas Analyzer

The use of NF₃ is significantly increasing every year. However, NF₃ is a greenhouse gas with a very high global warming potential. Therefore, the development of a material to replace NF₃ is required. F₃NO is considered a potential replacement to NF₃. In this study, the characteristics and cleaning performance of the F₃NO plasma to replace the greenhouse gas NF₃ were examined. Etching of SiO₂ thin films was performed, the DC offset of the plasma of both gases (i.e., NF₃ and F₃NO) was analyzed, and a residual gas analysis was performed. Based on the analysis results, the characteristics of the F₃NO plasma were studied, and the SiO₂ etch rates of the NF₃ and F₃NO plasmas were compared. The results show that the etch rates of the two gases have a difference of 95% on average, and therefore, the cleaning performance of the F₃NO plasma was demonstrated, and the potential benefit of replacing NF₃ with F₃NO was confirmed.

Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons

Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measurements of archived air samples and on in situ measurements at stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, we report global abundances, trends, and regional enhancements for HCFC-132b ([Formula: see text]), which is newly discovered in the atmosphere, and updated results for HCFC-133a ([Formula: see text]) and HCFC-31 ([Formula: see text]ClF). No purposeful end-use is known for any of these compounds. We find that HCFC-132b appeared in the atmosphere 20 y ago and that its global emissions increased to 1.1 Gg⋅y^-1 by 2019. Regional top-down emission estimates for East Asia, based on high-frequency measurements for 2016-2019, account for ∼95% of the global HCFC-132b emissions and for ∼80% of the global HCFC-133a emissions of 2.3 Gg⋅y^-1 during this period. Global emissions of HCFC-31 for the same period are 0.71 Gg⋅y^-1 Small European emissions of HCFC-132b and HCFC-133a, found in southeastern France, ceased in early 2017 when a fluorocarbon production facility in that area closed. Although unreported emissive end-uses cannot be ruled out, all three compounds are most likely emitted as intermediate by-products in chemical production pathways. Identification of harmful emissions to the atmosphere at an early stage can guide the effective development of global and regional environmental policy.

Fragmentation dynamics of nitrogen trifluoride induced by electron collision

The fragmentation dynamics of nitrogen trifluoride (NF₃) in collisions with a 500 eV electron is studied by using a momentum imaging spectrometer. The kinetic energy releases of two-body, three-body, and four-body fragmentation channels of NF₃ ^q+ (q = 2, 3) are investigated. The fragmentation dynamics of three-body, as well as four-body, dissociation channels is analyzed by the Dalitz plot and the Newton diagram. It is found that for all of the dissociation channels, the fragment including N atom (ion) always shares significant momenta, regardless of whether it is charged. For F atom, however, it is always emitted with negligible momenta.

Crystal Structures of α- and β-Nitrogen Trifluoride

The crystal structures of α-NF₃ and β-NF₃ are reported for the first time. As shown by powder neutron diffraction, the low-temperature α-NF₃ crystallizes in the orthorhombic space group Pnma ( oP16) with lattice parameters a = 6.71457(13) Å, b = 7.30913(14) Å, c = 4.55189(8) Å, V = 223.396(7) ų, and Z = 4 at T = 6 K. The intramolecular atom distances in α-NF₃ are 1.3639(16) and 1.3677(11) Å for N-F, and 2.1216(16) and 2.120(2) Å for F···F. The F-N-F bond angles are 101.92(7)° and 101.63(10)°. All data are in excellent agreement with quantum-chemical predictions and previously reported experimentally obtained gas-phase data. The high-temperature β-NF₃ is a plastic crystal, space group P4₂/ mnm ( tP120), with the lattice parameters a = 15.334(6) Å, c = 7.820(3) Å, V = 1838.6(12) ų, and Z = 30 at T = 60 K. Its crystal structure is closely related to that of the Frank-Kasper sigma phase.

Detachable Trap Preconcentrator with a Gas Chromatograph-Mass Spectrometer for the Analysis of Trace Halogenated Greenhouse Gases

A detachable trap preconcentrator coupled with a gas chromatograph-mass spectrometer (GC-MS) was developed for measuring trace amounts of anthropogenic halogenated greenhouse gases such as hydrofluorocarbons (HFCs) and nitrogen trifluoride (NF₃). Hayesep D cooled to -135 °C was used as an adsorbent for preconcentrating the target analytes. A differential trapping method was applied to remove major interfering substances such as CO₂, N₂, and O₂ in order to ensure sufficient sampling volume of secondary injection trap. This was accomplished without using any CO₂-removal agent such as molecular sieve adsorbents. Consequently, the temperature of the primary transfer trap was set to -75 °C for selective desorption of a significant amount of CO₂ that could be vented out. In the meantime, the major components of air, e.g., N₂ and O₂, were vented out before transferring the analytes to the secondary injection trap, in order to protect the gas plumbing from pressure shock induced by rapid temperature ramping over 100 °C/min in the secondary trap. When the traps were heated, linear motion was operated to detach them from the copper baseplate on the freezer, thereby restricting heat transfer to the freezer and maintaining the freezer close to the background temperature of -135 °C. This trap design is a key improvement to address the insufficient cooling capacity of the employed freezer, allowing sensitive detection of trace halogenated greenhouse gases in GC-MS. NF₃ and various HFCs at ambient levels were quantitatively and qualitatively measured with a precision of 0.35% at rates below 45 min/cycle. In particular, the limit of detection for NF₃ was evaluated to be 0.2 pmol/mol, with linear responses at ambient concentration.

The photovoltaic industry on the path to a sustainable future--environmental and occupational health issues

As it supplies solar power, a priori considered harmless for the environment and human health compared with fossil fuels, the photovoltaic (PV) industry seems to contribute optimally to reduce greenhouse gas emissions and, overall, to sustainable development. However, considering the forecast for rapid growth, its use of potentially toxic substances and manufacturing processes presenting health and safety problems may jeopardize its benefits. This paper aims to establish a profile of the PV industry in order to determine current and emerging environmental and health concerns. A review of PV system life cycle assessments, in light of the current state of the industry and its developmental prospects, reveals information deficits concerning some sensitive life cycle indicators and environmental impacts, together with incomplete information on toxicological data and studies of workers' exposure to different chemical and physical hazards. Although solar panel installation is generally considered relatively safe, the occupational health concerns related to the growing number of hazardous materials handled in the PV industry warrants an all-inclusive occupational health and safety approach in order to achieve an optimal equilibrium with sustainability. To prevent eco-health problems from offsetting the benefits currently offered by the PV industry, manufacturers should cooperate actively with workers, researchers and government agencies toward improved and more transparent research, the adoption of specific and stricter regulations, the implementation of preventive risk management of occupational health and safety and, lastly, greater responsibilization toward PV systems from their design until their end of life.

Experimental study of the mesospheric removal of NF3 by neutral meteoric metals and Lyman-α radiation

NF3 is a potent anthropogenic greenhouse gas with increasing industrial usage. It is characterized by a large global warming potential due in part to its large atmospheric lifetime. The estimated lifetime of about 550 years means that potential mesospheric destruction processes of NF3 should also be considered. The reactions of NF3 with the neutral metal atoms Na, K, Mg and Fe, which are produced by meteoric ablation in the upper mesosphere, were therefore studied. The observed non-Arrhenius temperature dependences of the reactions between about 190 and 800 K are interpreted using quantum chemistry calculations of the relevant potential energy surfaces. The NF3 absorption cross section at the prominent Lyman-α solar emission line (121.6 nm) was determined to be (1.59 ± 0.10) × 10(-18) cm(2) molecule(-1) (at 300 K). In the mesosphere above 60 km, Lyman-α photolysis is the dominant removal process of NF3; the reactions with K and Na are 1-2 orders of magnitude slower. However, the atmospheric lifetime of NF3 is largely controlled by reaction with O((1)D) and photolysis at wavelengths shorter than 190 nm; these processes dominate below 60 km.