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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Probing the limits of Si:P δ -doped devices patterned by a scanning tunneling microscope in a field-emission mode

Recently, a single atom transistor was deterministically fabricated using phosphorus in Si by H-desorption lithography with a scanning tunneling microscope (STM). This milestone in precision, achieved by operating the STM in the conventional tunneling mode, typically utilizes slow (∼102 nm2/s) patterning speeds. By contrast, using the STM in a high-voltage (>10 V) field-emission mode, patterning speeds can be increased by orders of magnitude to ≳104 nm2/s. We show that the rapid patterning negligibly affects the functionality of relatively large micron-sized features, which act as contacting pads for these devices. For nanoscale structures, we show that the resulting electrical transport is consistent with the donor incorporation chemistry constraining the electrical dimensions to a scale of 10 nm even though the pattering spot size is 40 nm.

Rudolph, M.↗
DOE OSTI2021

The effect of building retrofit measures on CO2 emission reduction – A case study with U.S. Medium office buildings

Building retrofit has great potential to reduce CO2 emissions since buildings are responsible for 36% of emissions in the United States. Several existing studies have examined the effect of building retrofit measures on CO2 emission reduction. However, these studies oversimplified emission factors of electricity by adopting constant annual emission factors. This study uses hourly emission factors of electricity to analyze the effect of building retrofit measures on emission reduction using U.S. medium office buildings as an example. We analyzed CO2 emission reduction effects of eight building retrofit measures that related to envelop and mechanical system in five locations: Tampa, San Diego, Denver, Great Falls, and International Falls. The main findings are: (1) estimating CO2 emission reduction with constant emission factors overestimates the emission reduction for most measures in San Diego, while it underestimates the emission reduction for most measures in Denver and International Falls; (2) The same retrofit measure may have different effects in CO2 emission reduction depending on the climates. For instance, improving lighting efficiency and improving equipment efficiency have less impacts in emission reduction in cold climates than hot climates; and (3) The most energy efficient measure may not be the most emission efficient measure. For example, in Great Falls, the most energy efficient measure is improving equipment efficiency, but the most emission efficient measure is improving heating efficiency.

Lou, Yingli↗
DOE OSTI2016

Russia's black carbon emissions: focus on diesel sources

Black carbon (BC) is a significant climate forcer with a particularly pronounced forcing effect in polar regions such as the Russian Arctic. Diesel combustion is a major global source of BC emissions, accounting for 25–30 % of all BC emissions. While the demand for diesel is growing in Russia, the country's diesel emissions are poorly understood. This paper presents a detailed inventory of Russian BC emissions from diesel sources. Drawing on a complete Russian vehicle registry with detailed information about vehicle types and emission standards, this paper analyzes BC emissions from diesel on-road vehicles. We use the COPERT emission model (COmputer Programme to calculate Emissions from Road Transport) with Russia-specific emission factors for all types of on-road vehicles. On-road diesel vehicles emitted 21 Gg of BC in 2014: heavy-duty trucks account for 60% of the on-road BC emissions, while cars represent only 5% (light commercial vehicles and buses account for the remainder). Using Russian activity data and fuel-based emission factors, the paper also presents BC emissions from diesel locomotives and ships, off-road engines in industry, construction and agriculture, and generators. The study also factors in the role of superemitters in BC emissions from diesel on-road vehicles and off-road sources. The total emissions from diesel sources in Russia are estimated to be 49 Gg of BC and 17 Gg of organic carbon (OC) in 2014. Off-road diesel sources emitted 58% of all diesel BC in Russia.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Diagnosing residual motion via the x-ray self emission from indirectly driven inertial confinement implosions

In an indirectly driven implosion, non-radial translational motion of the compressed fusion capsule is a signature of residual kinetic energy not coupled into the compressional heating of the target. A reduction in compression reduces the peak pressure and nuclear performance of the implosion. Measuring and reducing the residual motion of the implosion is therefore necessary to improve performance and isolate other effects that degrade performance. Using the gated x-ray diagnostic, the x-ray Bremsstrahlung emission from the compressed capsule is spatially and temporally resolved at x-ray energies of >8.7 keV, allowing for measurements of the residual velocity. Here details of the x-ray velocity measurement and fitting routine will be discussed and measurements will be compared to the velocities inferred from the neutron time of flight detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Black carbon emissions in Russia: A critical review

Russia has a particularly important role regarding black carbon (BC) emissions given the extent of its territory above the Arctic Circle, where BC emissions have a particularly pronounced effect on the climate. This study presents a comprehensive review of BC estimates from a range of studies. We assess underlying methodologies and data sources for each major emissions source based on their level of detail, accuracy and extent to which they represent current conditions. We then present reference values for each major emissions source. In the case of flaring, the study presents new estimates drawing on data on Russian associated petroleum gas and the most recent satellite data on flaring. We also present estimates of organic carbon (OC) for each source, either based on the reference studies or from our own calculations. In addition, the study provides uncertainty estimates for each source. Total BC emissions are estimated at 689 Gg in 2014, with an uncertainty range between (407-1,416), while OC emissions are 9,228 Gg (with uncertainty between 5,595 and 14,728). Wildfires dominated and contributed about 83% of the total BC emissions, however the effect on radiative forcing is mitigated by OC emissions. We also present an adjusted estimate of Arctic forcing from Russian OC and BC emissions. In recent years, Russia has pursued policies to reduce flaring and limit particulate emissions from on-road transport, both of which appear to significantly contribute to the lower emissions and forcing values found in this study.

Black carbon↗
DOE OSTI2014

Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma

A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Air Pollutant Emissions Projections for the Cement and Steel Industry in China and the Impact of Emissions Control Technologies

China’s cement and steel industry accounts for approximately half of the world’s total cement and steel production. These two industries are two of the most energy-intensive and highest carbon dioxide (CO 2 )-emitting industries and two of the key industrial contributors to air pollution in China. For example, the cement industry is the largest source of particulate matter (PM) emissions in China, accounting for 40 percent of its industrial PM emissions and 27 percent of its total national PM emissions. The Chinese steel industry contributed to approximately 20 percent of sulfur dioxide (SO 2) emissions and 27 percent of PM emissions for all key manufacturing industries in China in 2013. In this study, we analyzed and projected the total PM and SO 2 emissions from the Chinese cement and steel industry from 2010–2050 under three different scenarios: a Base Case scenario, an Advanced scenario, and an Advanced EOP (end-of-pipe) scenario. We used bottom-up emissions control technologies data and assumptions to project the emissions. In addition, we conducted an economic analysis to estimate the cost for PM emissions reductions in the Chinese cement industry using EOP control technologies, energy efficiency measures, and product change measures. The results of the emissions projection showed that there is not a substantial difference in PM emissions between the Base Case and Advanced scenarios, for both the cement and steel industries. This is mainly because PM emissions in the cement industry caused mainly by production process and not the fuel use. Since our forecast for the cement production in the Base Case and Advanced scenarios are not too different from each other, this results in only a slight difference in PM emissions forecast for these two scenarios. Also, we assumed a similar share and penetration rate of control technologies from 2010 up to 2050 for these two scenarios for the cement and steel industry. However, the Advanced EOP scenario showed significantly lower PM emissions for the cement industry, reaching to 1.7 million tons of PM in 2050, which is less than half of that in the other two scenarios. The Advanced EOP scenario also has the lowest SO 2 emissions for the cement industry in China, reaching to 212,000 tons of SO 2 in 2050, which is equal to 40 percent of the SO 2 emissions in the Advanced scenario and 30 percent of the emissions in the Base Case scenario. The SO 2 emission is mainly caused by fuel (coal) burning in cement kiln or steel processes. For the steel industry, the SO 2 emissions of the Advanced EOP scenario are significantly lower than the other scenarios, with emissions declining to 323,000 tons in 2050, which is equal to 21 percent and 17 percent of the emissions of Advanced and Base Case scenarios in 2050, respectively. Results of the economic analysis show that for the Chinese cement industry, end-of-pipe PM control technologies have the lowest abatement cost per ton of PM reduced, followed by product change measures and energy efficiency measures, respectively. In summary, in order to meet Chinese national and regional air quality standards, best practice end-of-pipe emissions control technologies must be installed in both cement and steel industry and it must be supplemented by implementation of energy efficiency technologies and reduction of cement and steel production through structural change in industry.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

A global anthropogenic emission inventory of atmospheric pollutants from sector- and fuel-specific sources (1970–2017): an application of the Community Emissions Data System (CEDS)

Global anthropogenic emission inventories remain vital for understanding the sources of atmospheric pollution and the associated impacts on the environment, human health, and society. Rapid changes in today's society require that these inventories provide contemporary estimates of multiple atmospheric pollutants with both source sector and fuel type information to understand and effectively mitigate future impacts. To fill this need, we have updated the open-source Community Emissions Data System (CEDS) (Hoesly et al., 2019) to develop a new global emission inventory, CEDSGBD-MAPS. This inventory includes emissions of seven key atmospheric pollutants (NOx; CO; SO2; NH3; non-methane volatile organic compounds, NMVOCs; black carbon, BC; organic carbon, OC) over the time period from 1970–2017 and reports annual country-total emissions as a function of 11 anthropogenic sectors (agriculture; energy generation; industrial processes; on-road and non-road transportation; separate residential, commercial, and other sectors (RCO); waste; solvent use; and international shipping) and four fuel categories (total coal, solid biofuel, the sum of liquid-fuel and natural-gas combustion, and remaining process-level emissions). The CEDSGBD-MAPS inventory additionally includes monthly global gridded (0.5°?×?0.5°) emission fluxes for each compound, sector, and fuel type to facilitate their use in earth system models. CEDSGBD-MAPS utilizes updated activity data, updates to the core CEDS default scaling procedure, and modifications to the final procedures for emissions gridding and aggregation. Relative to the previous CEDS inventory (Hoesly et al., 2018), these updates extend the emission estimates from 2014 to 2017 and improve the overall agreement between CEDS and two widely used global bottom-up emission inventories. The CEDSGBD-MAPS inventory provides the most contemporary global emission estimates to date for these key atmospheric pollutants and is the first to provide global estimates for these species as a function of multiple fuel types and source sectors. Dominant sources of global NOx and SO2 emissions in 2017 include the combustion of oil, gas, and coal in the energy and industry sectors as well as on-road transportation and international shipping for NOx. Dominant sources of global CO emissions in 2017 include on-road transportation and residential biofuel combustion. Dominant global sources of carbonaceous aerosol in 2017 include residential biofuel combustion, on-road transportation (BC only), and emissions from the waste sector. Global emissions of NOx, SO2, CO, BC, and OC all peak in 2012 or earlier, with more recent emission reductions driven by large changes in emissions from China, North America, and Europe. In contrast, global emissions of NH3 and NMVOCs continuously increase between 1970 and 2017, with agriculture as a major source of global NH3 emissions and solvent use, energy, residential, and the on-road transport sectors as major sources of global NMVOCs. Due to similar development methods and underlying datasets, the CEDSGBD-MAPS emissions are expected to have consistent sources of uncertainty as other bottom-up inventories. The CEDSGBD-MAPS source code is publicly available online through GitHub: https://github.com/emcduffie/CEDS/tree/CEDS_GBD-MAPS (last access: 1 December 2020). The CEDSGBD-MAPS emission inventory dataset (both annual country-total and monthly global gridded files) is publicly available under https://doi.org/10.5281/zenodo.3754964 (McDuffie et al., 2020c).

Mcduffie, Erin↗
DOE OSTI2019

Spatial heterogeneity analysis of the effects of urbanization on airport CO2 emissions in China - A geographically weighted approach using nighttime light data

Regional disparities in carbon dioxide (CO2) emissions from airports at the city level are of increasing importance for low-carbon development of the civil aviation sector. However, CO2 emissions from airport operations have rarely been estimated and discussed. We investigate the main driving forces of airport CO2 emissions by using Ordinary Least Square (OLS) and Geographically Weighted Regression (GWR) models, separately, to investigate whether urbanization drives airport CO2 emissions and to investigate spatial heterogeneity at the city level. Nighttime light (NTL) data from satellite observations are adopted as a proxy for urbanization. We obtained energy consumption data by end-use purpose for 70 airports in China and calculated the CO2 emissions from on-ground airport operations. The median CO2 emissions of the 70 sample airports are estimated to be 15.9 million tonnes for 2015. Results from the GWR model indicate that airport CO2 emissions are affected by five main factors: urbanization, foreign direct investment, the share of tertiary industry in gross domestic output, passenger turnover of civil aviation and passenger turnover of railways. The elasticity of urbanization shows an increasing trend from the east of China to the west. The spatial heterogeneity of the CO2 emissions of the five airport clusters that are located in five urban agglomerations is discussed. In order to achieve effective reductions of CO2 emissions from airports, policy-makers should consider the spatial heterogeneity of the major driving factors of carbon emissions in different regions to avoid carbon lock-in.

Airport CO2 emissions↗
DOE OSTI2022

Enhancing and Extinguishing the Different Emission Features of 2D (EA(1-)(x)FA(x))(4)Pb3Br10 Perovskite Films

2D hybrid perovskites are attractive for optoelectronic devices. In thin films, the color of optical emission and the texture of crystalline domains are often difficult to control. Here, a method for extinguishing or enhancing different emission features is demonstrated for the family of 2D Ruddlesden-Popper perovskites (EA(1-)(x)FA(x))(4)Pb3Br10 (EA = ethylammonium, FA = formamidinium). When grown from aqueous hydrobromic acid, crystals of (EA(1-)(x)FA(x))(4)Pb3Br10 retain all the emission features of their parent compound, (EA)(4)Pb3Br10. Surprisingly, when grown from dimethylformamide (DMF), an emission feature, likely self-trapped exciton (STE), near 2.7 eV is missing. Extinction of this feature is correlated with DMF being incorporated between the 2D Pb-Br sheets, forming (EA(1-)(x)FA(x))(4)Pb3Br10 center dot(DMF)(y). Without FA, films grown from DMF form (EA)(4)Pb3Br10, retain little solvent, and have strong emission near 2.7 eV. Slowing the kinetics of film growth strengthens a different emission feature, likely a different type of STE, which is much broader and present in all compositions. Films of (EA(1-)(x)FA(x))(4)Pb3Br10 center dot(DMF)(y) have large, micron-sized domains and homogeneous orientation of the semiconducting sheets, resulting in low electronic disorder near the absorption edge. The ability to selectively strengthen or extinguish different emission features in films of (EA(1-)(x)FA(x))(4)Pb3Br10 center dot(DMF)(y) reveals a pathway to tune the emission color in these compounds.

2D halide perovskites↗
DOE OSTI2015

Local H i emissivity measured with Fermi-LAT and implications for cosmic-ray spectra

Cosmic-ray (CR) electrons and nuclei interact with the Galactic interstellar gas and produce high-energy γ-rays. The γ-ray emission rate per hydrogen atom, called emissivity, provides a unique indirect probe of the CR flux. We present the measurement and the interpretation of the emissivity in the solar neighborhood for γ-ray energy from 50 MeV to 50 GeV. We analyzed a subset of 4 yr of observations from the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope (Fermi) restricted to absolute latitudes 10{sup ∘}<|b|<70{sup ∘}. From a fit to the LAT data including atomic, molecular, and ionized hydrogen column density templates, as well as a dust optical depth map, we derived the emissivities, the molecular hydrogen–to–CO conversion factor X{sub CO}=(0.902±0.007)×10{sup 20} cm{sup −2} (K km s{sup −1}){sup −1}, and the dust-to-gas ratio X{sub DUST}=(41.4±0.3)×10{sup 20} cm{sup −2} mag{sup −1}. Moreover, we detected for the first time γ-ray emission from ionized hydrogen. We compared the extracted emissivities to those calculated from γ-ray production cross sections and to CR spectra measured in the heliosphere. We observed that the experimental emissivities are reproduced only if the solar modulation is accounted for. This provides a direct detection of solar modulation observed previously through the anticorrelation between CR fluxes and solar activity. Finally, we fitted a parameterized spectral form to the heliospheric CR observations and to the Fermi-LAT emissivity and obtained compatible local interstellar spectra for proton and helium kinetic energy per nucleon between between 1 and 100 GeV and for electron–positrons between 0.1 and 100 GeV.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Recovery of Natural Gas Equipment Emissions into Gas Compression Engines for the Reduction of Potential Greenhouse Gas Emissions

Since the turn of the millennium, the United States (U.S.) oil and natural gas (ONG) industry has nearly doubled its natural gas production rate. As a result, the ONG industry has recently come under increasing scrutiny for its contributions to greenhouse gas (GHG) emissions. Consequently, various solutions to this problem have been proposed and formulated to reduce the impacts of GHG emissions on the environment. West Virginia University (WVU) have found it important to research the impacts of recovering vented gas streams into prime-mover engines. The U.S. Department of Energy (DOE) and National Energy Technology Laboratory (NETL) have granted WVU funding to research and develop a “Methane Mitigator” (M2) - a “Scalable Vent Mitigation Strategy to Simultaneously Reduce Methane Emissions and Fuel Consumption from the Compression Industry.” One of the main areas of interest for this research was the collection of emissions from natural gas equipment into a Caterpillar G3508J natural gas compression engine. The parameters being analyzed from the engine were brake-specific emissions and power output. The emissions sources considered for this research were pneumatic controllers (PCs), reciprocating compressor vents, and the engine’s open crankcase breather. The compressor vent and PC emissions were simulated using a mass flow controller (MFC) and flowed into the engine using two separate methods: (1) directly into the air intake, and (2) through a retrofitted closed crankcase ventilation system (CCV), serving as a buffer volume. The crankcase emissions were quantified without the CCV, and the impact on exhaust emissions from circulating the crankcase gases into the intake was measured. The simulated compressor vent and PC flows from the MFC had limited effect on the steady state operation of the engine and resulting performance. When the simulated flows were fed directly into the engine’s air intake, the changes within the engine’s continuous performance and emission parameters were larger but lasted for shorter durations. Conversely, when the simulated flows were fed into the CCV before entering the air intake, the changes in the engine’s performance and emission parameters were less pronounced for continuous analysis but lasted for longer durations. In either case, the continuous emission changes in both emissions and performance varied in size depending on the test scenario being run, but the cycle average changes in emissions and performance showed little impact overall compared to the engine’s baseline operation. As a result, the inclusion of a CCV shows a decrease in baseline carbon dioxide equivalent (CO2-eq.) engine emissions (from combined exhaust and open crankcase) of almost 4%. Likewise, the CCV inclusion reduced baseline total methane (CH4) from combined exhaust and open crankcase by upwards of 16%. These atmospheric emissions only decreased further with the inclusions of collected PC and compressor vent flows. The resulting changes in time-averaged rated exhaust behavior (or lack thereof) prove that the proposed M2 system could likely be deployed at sites with modern lean-burn natural gas engines as a viable option for reducing and eliminating potential GHG sources that would have otherwise been unutilized as energy sources.

03 NATURAL GAS↗
DOE OSTI2018

Recent intensification of winter haze in China linked to foreign emissions and meteorology

Wintertime aerosol pollution in Northern China has increased over the past several decades as anthropogenic emissions in China have increased, and has increased dramatically since the beginning of the 21st century, but the causes and their quantitative contributions remain uncertain. Here we use an aerosol source tagging capability implemented in a global aerosol-climate model to assess long-term trends of PM2.5 (particulate matter less than 2.5 µm in diameter) in Northern China. Our analysis suggests that increasing PM2.5 concentrations due to local emission increases within China were obscured (~13%) by foreign emission reductions between 1980–2000. As foreign emissions stabilized during 2000-2014, their counteracting effect almost disappeared, uncovering China’s pollution potential from domestic emission increases. The meteorology dominated PM2.5 trend during 1990–1996 and also uncovered the pollution potential due to decadal variations in winds. The stabilized foreign emissions together with changing meteorology explain a quarter of the larger increasing trend of PM2.5 since the beginning of the 21st century. Future foreign emissions are not expected to help hiding China’s pollution, reductions in local emissions are the efficient way to improve future air quality in Northern China.

Yang, Yang↗
DOE OSTI2017

Binary Power Plant CO2 Life Cycle Emissions Including Isobutane Fugitive Emission

Geothermal energy production has one of the lowest life cycle CO2 emission factors (~ 15 g-CO2/kWh) for plants producing electricity (Hondo, 2005). This life cycle factor includes indirect emissions from plant construction as well as ongoing operations such as additional well drilling and equipment replacement. Not included in this calculation are direct emissions from geothermal power production. Geothermal flash plants emit CO2 at rates related to the reservoir concentration. Binary plants report “near zero” emissions of high global warming potential gases because of their closed loop system design. Binary plants use working fluids to drive the turbine generators and leakage of these working fluids have not yet been quantified. To assess the working fluid emissions from geothermal power production using an Organic Rankine Cycle, reported isobutane emissions were accessed for 3 California binary plants from the Great Basin Unified and Imperial County Air Pollution Control Districts as well as the California Air Resource Board. Each binary plant used in this study has been operating for more than 25 years. From the data, two types of isobutane emissions were accounted for over a 15 month period: ‘normal’ equipment leakage and equipment breakdown emissions. This preliminary analysis of working fluid emissions from these plants suggest that if a binary plant has equipment failures, the majority of the isobutane releases can be due to these events. The results indicate that a well maintained binary plant releases approximately 0.13 g-Isobutane/kWh where as a plant with equipment failures releases approximately 6 g-Isobutane/kWh. Assuming a greenhouse warming potential of 3 for isobutane, these emission values become 0.4 and 18 g-CO2e/kWh (where CO2e is the CO2 equivalent effect). The direct operation isobutane leakage for a well maintained binary plant does not significant increase the life cycle CO2 emission factor whereas a plant with significant equipment issues can effectively double the life cycle CO2 emissions. This limited data set suggests that when direct CO2e fugitive emission are add to the indirect CO2 emissions, the total CO2 emissions from binary power plants are equivalent or less than nuclear, as well as other renewables power production such as wind and solar.

15 GEOTHERMAL ENERGY↗
DOE OSTI2022

Triple Emission of 5'-( para -R-Phenylene)vinylene-2-(2'-hydroxyphenyl)benzoxazole (PVHBO). Part I: Dual Emission from the Neutral Species

The effects of 5'-(para-R-phenylene)vinylene (PV) substituents on the emission properties of 2-(2'-hydroxyphenyl)benzoxazole (HBO) are analyzed using steady-state and time-resolved absorption and emission spectroscopies in addition to quantum chemical calculations. All members in the series of PVHBOs are capable of excited-state intramolecular proton transfer (ESIPT) with a solvent sensitivity that is typical of a HBO derivative to produce a normal (aka enol) emission and an excited-state tautomer (aka keto) emission. These two emission bands of the neutral dyes are discussed in the current paper. The intermolecular proton transfer, i.e., the deprotonation, of a PVHBO results in the third band of the triple emission, which is described in the succeeding paper. The placement of an electron-withdrawing substituent R on the PVHBO scaffold increases the intensity of the keto emission relative to the enol emission in hydrogen-bonding solvents. The R substituents do not significantly alter the wavelengths of the enol and keto emission bands, which are located in the blue and green regions, respectively, of the visible spectrum. The ultrafast time-resolved spectroscopies and quantum chemical calculations offer explanations on how the R group and the solvent affect the enol and keto emission properties (i.e., wavelength, lifetime, fluorescence quantum yield, and relative ratio of their emissions). Here, the key findings include the following: (1) the emission energies of both enol and keto forms are not sensitively dependent on the R substituent and (2) the solvent-engaged enol excited state is quenched more efficiently as the R substituent becomes more electron-withdrawing. A PVHBO acts as a fusion of HBO and stilbenoid that intersect at the hydroxyphenyl moiety. Depending on the solvent and other environmental conditions, PVHBOs may exhibit the ESIPT property of HBO or the substituent-dependent emission of stilbenoid. This paper and the succeeding article provide a photophysical model of PVHBOs to explain the wavelengths and relative abundances of the three emission bands (enol, keto, and anion) that these compounds are able to produce. Judicial selection of the environmental factors may drive the emission of a PVHBO into the spectral regions of blue, green, and, in a couple of cases, orange or red.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Much of zero emissions commitment occurs before reaching net zero emissions

Abstract We explore the response of the Earth’s coupled climate and carbon system to an idealized sequential addition and removal of CO 2 to the atmosphere, following a symmetric and continuous emissions pathway, in contrast to the discontinuous emissions pathways that have largely informed our understanding of the climate response to net zero and net negative emissions to date. We find, using both an Earth system model and an ensemble of simple climate model realizations, that warming during the emissions reduction and negative emissions phases is defined by a combination of a proportionality of warming to cumulative emissions characterized by the transient climate response to emissions (TCRE), and a deviation from that proportionality that is governed by the zero emissions commitment (ZEC). About half of the ZEC is realized before reaching zero emissions, and the ZEC thus also controls the timing between peak cumulative CO 2 emissions and peak temperature, such that peak temperature may occur before peak cumulative emissions if ZEC is negative, underscoring the importance of ZEC in climate policies aimed to limit peak warming. Thus we argue that ZEC is better defined as the committed warming relative to the expected TCRE proportionality, rather than as the additional committed warming that will occur after reaching net zero CO 2 emissions. Once established, the combined TCRE and ZEC relationship holds almost to complete removal of prior cumulative CO 2 emissions. As cumulative CO 2 emissions approach zero through negative CO 2 emissions, CO 2 concentrations drop below preindustrial values, while residual long-term climate change continues, governed by multicentennial dynamical processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

A new process-based and scale-aware desert dust emission scheme for global climate models – Part I: Description and evaluation against inverse modeling emissions

Desert dust accounts for most of the atmosphere's aerosol burden by mass and produces numerous important impacts on the Earth system. However, current global climate models (GCMs) and land-surface models (LSMs) struggle to accurately represent key dust emission processes, in part because of inadequate representations of soil particle sizes that affect the dust emission threshold, surface roughness elements that absorb wind momentum, and boundary-layer characteristics that control wind fluctuations. Furthermore, because dust emission is driven by small-scale (~ 1 km or smaller) processes, simulating the global cycle of desert dust in GCMs with coarse horizontal resolutions (~ 100 km) presents a fundamental challenge. This representation problem is exacerbated by dust emission fluxes scaling nonlinearly with wind speed above a threshold wind speed that is sensitive to land-surface characteristics. Here, we address these fundamental problems underlying the simulation of dust emissions in GCMs and LSMs by developing improved descriptions of (1) the effect of soil texture on the dust emission threshold, (2) the effects of nonerodible roughness elements (both rocks and green vegetation) on the surface wind stress, and (3) the effects of boundary-layer turbulence on driving intermittent dust emissions. We then use the resulting revised dust emission parameterization to simulate global dust emissions in a standalone model forced by reanalysis meteorology and land-surface fields. We further propose (4) a simple methodology to rescale lower-resolution dust emission simulations to match the spatial variability of higher-resolution emission simulations in GCMs. The resulting dust emission simulation shows substantially improved agreement against regional dust emissions observationally constrained by inverse modeling. We thus find that our revised dust emission parameterization can substantially improve dust emission simulations in GCMs and LSMs.

54 ENVIRONMENTAL SCIENCES↗