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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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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Investigation of Process Emissions during Thermal Cutting of Clad Metals from the Nuclear Sector - 20183

Typically, reactor pressure vessels as well as steam generators comprising low alloyed steel with a cladding of stainless steel. Recently the permissible values for Cr (VI) in the air of the working areas have been reduced in Germany from 100 μg/m{sup 3} to 1 μg/m{sup 3} air. This results in the danger that even with low-alloy steel with claddings these limit values would be exceeded when using flame cutting technologies. In order to ensure compliance with the permissible limit values, exhaust gas systems with gas cleaning measures are provided. The process emission test shall replace the assumptions required for the design of these systems with measured values. NUKEM Technologies Engineering Services GmbH (NUKEM) has chosen autogenous flame cutting as an example of a thermal cutting system for process emission testing, as there are no proven values in the literature for the Cr (VI) and NiOx emissions produced. The autogenous flame cutting can be used for a variety of cutting tasks within decommissioning projects. In order to simulate the material to be cut, mock ups were generated and cut from information about the material specification for the reactor pressure vessel from existing nuclear power plants including possible claddings. The cutting length needed for analysis in the test will be maximum 100 mm. The airborne emissions from the thermal cutting process will be captured and analyzed as follows: - Dust emission: The generated particles will be collected by a hood equipped with strong suction device and suitable filter elements. The resulting filter is gravimetrically measured before and after the tests. - Particle Size Distribution: The airborne particle size distribution measurement will result in figures for the size and number of particles arising from the thermal cutting process. - Gas Analysis: The gas analysis enables the determination of e.g. CO{sub 2}, CO, O{sub 3}, NO, NO{sub 2}. - Cr (VI) and NiOx Analysis: For the Cr (VI) and NiOx analysis, samples of the filter residue will be taken. As a result Cr (VI) in relation to total Cr as well as the Ni content will be determined by ICP-optically emission spectroscopy and put in relation to the total dust amount. The process emissions test itself as well as the necessary gas analyses and spectroscopic analyses were carried out at the Institute of Materials Science (IW) of Leibniz Universitaet Hannover (LUH). The results of the process emission tests are used to confirm the design of the gas cleaning systems. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Operational Emissions Accounting for Commercial Buildings

Buildings account for 30% of greenhouse gas emissions in the US. In order to aid in better decisions that reduce emissions from building operations, accurate emissions accounting is important. This report reviews existing operational GHG emission accounting approaches, frameworks, and data sources. We present the results of testing emissions accounting frameworks and emission factors with example data from two buildings and provide recommendations while using an emissions accounting framework.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Anthropogenic emissions of NOx over China: Reconciling the difference of inverse modeling results using GOME-2 and OMI measurements

Inverse modeling using satellite observations of nitrogen dioxide (NO2) columns has been extensively used to estimate nitrogen oxides (NOx) emissions in China. Recently, the Global Ozone Monitoring Experiment-2 (GOME-2) and Ozone Monitoring Instrument (OMI) provide independent global NO2 column measurements on a nearly daily basis at around 9:30 and 13:30 local time across the equator, respectively. Anthropogenic NOx emission estimates by applying previously developed monthly inversion (MI) or daily inversion (DI) methods to these two sets of measurements show substantial differences. We improve the DI method by conducting model simulation, satellite retrieval, and inverse modeling sequentially on a daily basis. After each inversion, we update anthropogenic NOx emissions in the model simulation with the newly obtained a posteriori results. Consequently, the inversion-optimized emissions are used to compute the a priori NO2 profiles for satellite retrievals. As such, the a priori profiles used in satellite retrievals are now coupled to inverse modeling results. The improved procedure was applied to GOME-2 and OMI NO2 measurements in 2011. The new daily retrieval-inversion (DRI) method estimates an average NOx emission of 6.9 Tg N/yr over China, and the difference between using GOME-2 and OMI measurements is 0.4 Tg N/yr, which is significantly smaller than the difference of 1.3 Tg N/yr using the previous DI method. Using the more consistent DRI inversion results, we find that anthropogenic NOx emissions tend to be higher in winter and summer than spring (and possibly fall) and the weekday-to-weekend emission ratio tends to increase with NOx emission in China.

Gu, Dasa↗
DOE OSTI2023

Black carbon emissions from modern automated cordwood stoves for space heating

Wood burning stove design is improving as regulation become stricter for particulate matter emissions. Here, this study describes results of black carbon (BC) emissions from three modern automated wood stoves when tested in common failure modes using a test protocol that included cold-starts, high and low fuel loading densities, and use of overly large pieces of fuel. Emission sampling was performed using a dilution sampling system in tandem with an aethalometer to measure BC with high time resolution. Results show that the time-weighted average BC emission rates were 0.91, 4.30, and 1.74 g/h for the three stoves tested (A, B, and C respectively), the values, both higher and lower than the United States 2020 certification test emission limit of 2.5 g/h. The results demonstrate good performance overall, given the rigorous nature of the testing protocol used. The aethalometer data showed that the performance was relatively poor during cold-start, when the fuel was ignited and combusted without a coalbed, and when stoves failed to optimize air delivery due to specific loading and output conditions. During the cold-start test section, the average BC emission rate was seven times higher than the overall average for Stove A, 10 times above the average for Stove B, and two times above the average emission rate for Stove C. Calculations of the Average Angstrom Absorption Exponent (AAE) of the exhaust aerosol showed little correlation with BC concentration. The results show that automation results in a quantifiable reduction in particular BC emissions.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Hourly and daily rainfall intensification causes opposing effects on C and N emissions, storage, and leaching in dry and wet grasslands

Climate change is expected to alter hourly and daily rainfall regimes and, in turn, the dynamics of ecosystem processes controlling greenhouse gas emissions that affect climate. Here, we investigate the effects of expected twenty-first century changes in hourly and daily rainfall on soil carbon and nitrogen emissions, soil organic matter (SOM) stocks, and leaching using a coupled mechanistic carbon and nitrogen soil biogeochemical model (BAMS2). The model represents various abiotic and biotic processes involving 11 SOM pools. These processes include fungal depolymerization, heterotrophic bacterial mineralization, nitrification, denitrification, microbial mortality, necromass decomposition, microbial response to water stress, protection, aqueous advection and diffusion, aqueous complexation, and gaseous dissolution. Multi-decadal modeling with varying rainfall patterns was conducted on nine Australian grasslands in tropical, temperate, and semi-arid regions. Our results show that annual CO 2 emissions in the semi-arid grasslands increase by more than 20% with a 20% increase in annual rainfall (with no changes in the rainfall timing), but the tropical grasslands have opposite trends. A 20% increase in annual rainfall also increases annual N 2 O and NO emissions in the semi-arid grasslands by more than 10% but decreases emissions by at least 25% in the temperate grasslands. When subjected to low frequency and high magnitude daily rainfall events with unchanged annual totals, the semi-arid grasslands are the most sensitive, but changes in annual CO 2 emissions and SOM stocks are less than 5 %. Finally, intensification of hourly rainfall did not significantly alter CO 2 emissions and SOM stocks but changed annual NH 3 emissions in the tropical grasslands by more than 300%.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Volatile organic compound emissions from 4D printing: Effects of material composition and external stimulus

4D printing of stimuli-responsive materials extends 3D printing by enabling the fabricated structures to transform their shapes and properties over time in response to external stimuli. Numerous research efforts have been dedicated to developing new smart materials, enhancing material printability, and ensuring time-evolving properties. Meanwhile, the use of smart materials and external stimuli in 4D printing has introduced the possibility of air emissions that can potentially deteriorate the indoor air quality at the workplace and pose continuous health hazards to users during the production and use phases. These potential air emissions caused by 4D printing have not yet been assessed in current literature, leading to unknown occupational hazards and human health effects. This study focuses on stereolithography-based 4D printing with constrained thermo-mechanics and builds an emission model to quantify the volatile organic compound emissions from printing, shape programming, and shape recovery stages. The established model mathematically links the emission characteristics with material compositional design and stimuli-response mechanisms. Additionally, shape fixity and recovery abilities are considered to analyze the trade-off between the air emissions and stimuli-response performance of 4D printed parts. Case study results suggest that the methacrylate-based thermo-responsive material with higher glass transition temperature leads to higher air emissions, surpassing the permissible exposure level in the indoor environment. By altering the thermo-temporal conditions, a 61.29% reduction in emission yield can be achieved while ensuring a satisfactory shape memory performance.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Uncertainties of isoprene emissions in the MEGAN model estimated for a coniferous and broad-leaved mixed forest in Southern China

Using local observed emission factor, meteorological data, vegetation 5 information and dynamic MODIS LAI, MEGANv2.1 was constrained to predict the isoprene emission from Dinghushan forest in the Pearl River Delta region during a field campaign in November 2008, and the uncertainties in isoprene emission estimates were quantified by the Monte Carlo approach. The results indicate that MEGAN can predict the isoprene emission reasonably during the campaign, and the mean value of isoprene emission is 2.35 mg m-2 h-1 in daytime. There are high uncertainties associated with the MEGAN inputs and calculated parameters, and the relative error can be as high as -89 to 111% for a 95% confidence interval. The emission factor of broadleaf trees and the activity factor accounting for light and temperature dependence are the most important contributors to the uncertainties in isoprene emission estimated for the Dinghushan forest during the campaign. The results also emphasize the importance of accurate observed PAR and temperature to reduce the uncertainties in isoprene emission estimated by model, because the MEGAN model activity factor accounting for light and temperature dependence is highly sensitive to PAR and temperature.

Situ, S.↗
DOE OSTI2015

Life-cycle assessment of greenhouse gas and air emissions of electric vehicles: A comparison between China and the U.S.

We evaluated the fuel-cycle emissions of greenhouse gases (GHGs) and air pollutants (NOx, SO2, PM10, and PM2.5) of electric vehicles (EVs) in China and the United States (U.S.), two of the largest potential markets for EVs in the world. Six of the most economically developed and populated regions in China and the U.S. were selected. The results showed that EV fuel-cycle emissions depend substantially on the carbon intensity and cleanness of the electricity mix, and vary significantly across the regions studied. In those regions with a low share of coal-based electricity (e.g., California), EVs can reduce GHG and air pollutant emissions (except for PM) significantly compared with conventional vehicles. However, in the Chinese regions and selected U.S. Midwestern states where coal dominates in the generation mix, EVs can reduce GHG emissions but increase the total and urban emissions of air pollutants. In 2025, EVs will offer greater reductions in GHG and air pollutant emissions because emissions from power plants will be better controlled; EVs in the Chinese regions examined, however, may still increase SO2 and PM emissions. Reductions of 60–85% in GHGs and air pollutants could be achieved were EVs charged with 80% renewable electricity or the electricity generated from the best available technologies of coal-fired power plants, which are futuristic power generation scenarios.

Electric vehicles↗
DOE OSTI2013

Implications of uncertainty on regional CO2 mitigation policies for the U.S. onroad sector based on a high-resolution emissions estimate

In this study we present onroad fossil fuel CO2 emissions estimated by the Vulcan Project, an effort quantifying fossil fuel CO2 emissions for the U.S. in high spatial and temporal resolution. This high-resolution data, aggregated at the state-level and classified in broad road and vehicle type categories, is compared to a commonly used national-average approach. We find that the use of national averages incurs state-level biases for road groupings that are almost twice as large as for vehicle groupings. The uncertainty for all groups exceeds the bias, and both quantities are positively correlated with total state emissions. States with the largest emissions totals are typically similar to one another in terms of emissions fraction distribution across road and vehicle groups, while smaller-emitting states have a wider range of variation in all groups. Errors in reduction estimates as large as ±60% corresponding to ±0.2 MtC are found for a national-average emissions mitigation strategy focused on a 10% emissions reduction from a single vehicle class, such as passenger gas vehicles or heavy diesel trucks. Recommendations are made for reducing CO2 emissions uncertainty by addressing its main drivers: VMT and fuel efficiency uncertainty.

Mendoza, D↗
DOE OSTI2013

Study on the reduction of atmospheric mercury emissions from mine waste enriched soils through native grass cover in the Mt. Amiata region of Italy

Atmospheric mercury emissions from mine-waste enriched soils were measured in order to compare the mercury fluxes of bare soils with those from other soils covered by native grasses. Our research was conducted near Mt. Amiata in central Italy, an area that was one of the largest and most productive mining centers in Europe up into the 1980s. To determine in situ mercury emissions, we used a Plexiglas flux chamber connected to a portable mercury analyzer (Lumex RA-915+). This allowed us to detect, in real time, the mercury vapor in the air, and to correlate this with the meteorological parameters that we examined (solar radiation, soil temperature, and humidity). The highest mercury flux values (8000 ng m{sup −2} h{sup −1}) were observed on bare soils during the hours of maximum insulation, while lower values (250 ng m{sup −2} h{sup −1}) were observed on soils covered by native grasses. Our results indicate that two main environmental variables affect mercury emission: solar radiation intensity and soil temperature. The presence of native vegetation, which can shield soil surfaces from incident light, reduced mercury emissions, a result that we attribute to a drop in the efficiency of mercury photoreduction processes rather than to decreases in soil temperature. This finding is consistent with decreases in mercury flux values down to 3500 ng m{sup −2} h{sup −1}, which occurred under cloudy conditions despite high soil temperatures. Moreover, when the soil temperature was 28 °C and the vegetation was removed from the experimental site, mercury emissions increased almost four-fold. This increase occurred almost immediately after the grasses were cut, and was approximately eight-fold after 20 h. Thus, this study demonstrates that enhancing wild vegetation cover could be an inexpensive and effective approach in fostering a natural, self-renewing reduction of mercury emissions from mercury-contaminated soils. -- Highlights: ► Mercury air/surface exchange from grass covered soil is different from bare soil. ► Light enhances mercury emissions and is the main parameter driving the process. ► The presence of wild vegetation covering the soil reduces mercury emission. ► Vegetative covers could be a solution to reduce atmospheric mercury pollution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Energy consumption and CO{sub 2} emissions in Iran, 2025

Climate change and global warming as the key human societies' threats are essentially associated with energy consumption and CO{sub 2} emissions. A system dynamic model was developed in this study to model the energy consumption and CO{sub 2} emission trends for Iran over 2000–2025. Energy policy factors are considered in analyzing the impact of different energy consumption factors on environmental quality. The simulation results show that the total energy consumption is predicted to reach 2150 by 2025, while that value in 2010 is 1910, which increased by 4.3% yearly. Accordingly, the total CO{sub 2} emissions in 2025 will reach 985 million tonnes, which shows about 5% increase yearly. Furthermore, we constructed policy scenarios based on energy intensity reduction. The analysis show that CO{sub 2} emissions will decrease by 12.14% in 2025 compared to 2010 in the scenario of 5% energy intensity reduction, and 17.8% in the 10% energy intensity reduction scenario. The results obtained in this study provide substantial awareness regarding Irans future energy and CO{sub 2} emission outlines. - Highlights: • Creation of an energy consumption model using system dynamics. • The effect of different policies on energy consumption and emission reductions. • An ascending trend for the environmental costs caused by CO{sub 2} emissions is observed. • An urgent need for energy saving and emission reductions in Iran.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Organophosphorus esters (OPEs) in PM2.5 in urban and e-waste recycling regions in southern China: concentrations, sources, and emissions

Highlights: • OPE concentrations and compositions displayed great variations among the sources. • High OPE levels were related to the electronic, plastic, and chemical industries. • Correlations between OPEs suggests different emission mechanisms from the sources. • The total air emission of OPEs from the 20 urban industrial sources was 1460 kg/yr. • The total air emission of OPEs from the e-waste recycling facilities was 133 kg/yr. Organophosphate esters (OPEs) are novel ubiquitous contaminants that are attracting growing concern, but their emissions into the environment are still poorly understood. In this study, 12 OPEs were measured in fine particulate matter (PM{sub 2.5}) at 20 industrial sites in an urban region and four e-waste recycling facilities in a rural region in southern China. There was no significant difference in the concentrations of ∑OPEs between the urban region (519–62,747 pg/m{sup 3}, median = 2854 pg/m{sup 3}) and the rural e-waste region (775–13,823 pg/m{sup 3}, 3321 pg/m{sup 3}). High OPE concentrations in urban PM{sub 2.5} were generally associated with the electrical, electronic, plastic, and chemical industries. There were no significant correlations between most OPEs in these two regions, suggesting different emission mechanisms. The average emissions of ∑OPEs estimated using a simplified dispersion model were 73.0 kg/yr from the urban industrial point sources and 33.2 kg/yr from the e-waste recycling facilities. The estimated emission inventory from industrial activities in the whole city (3228–4452 kg/yr) was approximately 30-fold higher than that from the e-waste recycling (133 kg/yr) facilities because urban region has a much larger industrial scale. To the best of our knowledge, this is the first effort to model the emissions of OPEs from industrial and e-waste recycling activities to the atmosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Depth-dependent links between microbial taxa and nitrous oxide emissions in a long-term cotton cropping system employing soil health practices

Long-term management practices can shape soil microbial communities in ways that influence nitrogen (N) dynamics and nitrous oxide (N 2 O) emissions. We leverage a 41-year continuous cotton cropping experiment with contrasting tillage, cover cropping, and N fertilization regimes to investigate how these long-term strategies influence soil microbial communities and their associations with N 2 O fluxes during the cotton growing season. Using 16S rRNA gene metabarcoding, we assessed microbial composition in surface and subsurface soils and evaluated its relationship with temporal N 2 O emissions. Among the management practices, N fertilization – a known driver of N 2 O emissions – had the strongest effect on microbial community composition and was linked to a greater number of taxa correlated to N 2 O emissions, particularly in surface soils. Soil pH emerged as a key variable influencing microbial structure across depth and was negatively associated with both N 2 O emissions and microbial composition in the surface layers of fertilized soils. In total, 57 archaeal/bacterial taxa were correlated with N 2 O fluxes, but only seven were shared across depths, suggesting distinct microbial contributors in surface and subsurface soils. Several of these taxa have been previously reported to be associated with N and C cycling processes such as nitrate respiration or carbon turnover, indicating functional context to their correlation with N 2 O fluxes. Temporal shifts in the abundance of key taxa aligned with seasonal peaks in N 2 O emissions, notably in early and late August, and were most pronounced under conventional tillage, hairy vetch cover cropping, and N fertilization. While 16S-based associations cannot confirm functional gene presence or activity, these findings demonstrate that long-term fertilization and associated soil acidification are dominant drivers of microbial shifts linked to N 2 O emissions and highlight the importance of accounting for depth-specific and seasonal microbial dynamics when evaluating management impacts on greenhouse gas emissions.

16S rRNA gene sequencing↗
DOE OSTI2020

Life cycle greenhouse gas emissions and energy use of polylactic acid, bio-derived polyethylene, and fossil-derived polyethylene

Bioplastics recently have become an attractive, viable, and popular alternative to conventional petroleum-based plastics, with the hope that replacing fossil-derived plastics with renewable alternatives will reduce greenhouse gas (GHG) emissions and fossil energy consumption (FEC). The bioplastic industry is encouraging creative designs and enhanced properties such as biodegradability, which is considered a sustainable solution for waste plastic management. However, biodegradability also means that carbon in the product is emitted to the atmosphere as GHG emissions. In this paper, a life cycle analysis (LCA) of biodegradable polylactic acid (PLA) and bio-polyethylene (bio-PE) plastics was conducted to understand the environmental effects of these bioplastics from feedstock production to product end-of-life (EOL). In particular, emissions from biodegradability (EOL emissions) are accounted for. The results were compared to those of conventional fossil-based plastics such as high-density polyethylene (HDPE) and low-density polyethylene (LDPE). Results showed that the lowest GHG emissions (-1.0 and 1.7 kg CO 2 e per kg for bio-PE and PLA with no biodegradation, respectively) and FEC (29 and 46 MJ per kg of bio-PE and PLA, respectively) were achieved with bio-derived plastics, particularly bio-PE plastic. However, despite the benefits of biogenic carbon uptake, when landfill and composting emissions were considered for the PLA pathway, the life cycle emissions of PLA increase significantly, from 16% to 163% depending on the biodegradation condition, compared to the case where there is no degradation in the landfill. This study also contributed to understand the effects on the GHG emissions of biodegradability in landfill and composting scenarios, regional electricity mix, and plastics manufacturing technologies. (C) 2020 The Authors. Published by Elsevier Ltd.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Structural consideration on the emission properties of Eu{sup 2+}-doped Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} orthophosphates

Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} were synthesized by a standard solid state reaction. Structural analyses have revealed that Li{sub 2}BaMgP{sub 2}O{sub 8} is a member of the olgite family, as is the case with Na{sub 2}BaMgP{sub 2}O{sub 8}. The layer-framework build up by corner-sharing MgO{sub 6} octahedra and PO{sub 4} tetrahedra twists around C{sub 3} axes to match the size of B-site cation (Li{sup +} or Na{sup +}). This twisting affects the coordination number for the B-site cation and unit cell size. Eu-doped Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} exhibited intense violet-blue emission under ultraviolet excitation. They were characterized by two emission centers; Eu{sup 2+} ions replacing A-site cations (Ba{sup 2+}) and B-site cations (Li{sup +} or Na{sup +}). The B-site Eu{sup 2+} emission was very sensitive to the twisting behavior caused by original B-site cation. - Graphical abstract: Emission properties of Eu{sup 2+}-doped M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} (M{sup I}: Li, Na) are discussed from the viewpoint of the host crystal structure solved by X-ray powder diffraction technique and Raman spectroscopy. Highlights: Black-Right-Pointing-Pointer Olgite-type Li{sub 2}BaMgP{sub 2}O{sub 8} has been prepared by a solid state reaction. Black-Right-Pointing-Pointer Crystal structure of M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} changes, depending on M{sup I} ion size. Black-Right-Pointing-Pointer Eu{sup 2+}-doped M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} exhibits violet-blue emission under ultraviolet irradiation. Black-Right-Pointing-Pointer Emission from M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} is characterized by two Eu{sup 2+} emission centers. Black-Right-Pointing-Pointer One emission component of the two is sensitive to the structural change induced by M{sup I}.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Luminescence properties of Ca{sub 0.65}La{sub 0.35}F{sub 2.35}:Yb{sup 3+}, Er{sup 3+} with enhanced red emission via upconversion

Graphical abstract: Under 980 nm excitation, Ca{sub 0.65}La{sub 0.35}F{sub 2.35}:20 mol.%Yb{sup 3+}, xEr{sup 3+} showed intense red upconversion luminescence, which was ascribed to {sup 4}F{sub 9/2} {yields} {sup 4}I{sub 15/2} transition of Er{sup 3+}. The ground-state absorption (GSA), excited-state absorption (ESA) and energy transfer (ET) processes between Er{sup 3+}/Yb{sup 3+} ions and Er{sup 3+}/Er{sup 3} ions were involved in the enhanced red emission mechanism. . Research highlights: {yields} Yb{sup 3+}/Er{sup 3+} codoped Ca{sub 0.65}La{sub 0.35}F{sub 2.35} materials with intense red emission via upconversion were prepared by a high temperature solid-state method. {yields} Ca{sub 0.65}La{sub 0.35}F{sub 2.35}:20 mol.%Yb{sup 3+}, xEr{sup 3+} showed intense red upconversion luminescence, which was ascribed to {sup 4}F{sub 9/2} {yields} {sup 4}I{sub 15/2} transition of Er{sup 3+}. {yields} The green and red emissions are two-photon processes, while both energy transfers between Yb{sup 3+}/Er{sup 3+} and Er{sup 3+}/Er{sup 3+} are involved in the red emission mechanism of the Ca{sub 0.65}La{sub 0.35}F{sub 2.35}:20 mol.%Yb{sup 3+}, xEr{sup 3+} materials. -- Abstract: Yb{sup 3+}/Er{sup 3+} codoped Ca{sub 0.65}La{sub 0.35}F{sub 2.35} materials with intense red emission via upconversion were prepared by a high temperature solid-state method. Based on the upconversion luminescence properties investigations, it was found that, under 980 nm excitation, Ca{sub 0.65}La{sub 0.35}F{sub 2.35}:20 mol.%Yb{sup 3+}, xEr{sup 3+} showed intense red upconversion luminescence, which was ascribed to {sup 4}F{sub 9/2} {yields} {sup 4}I{sub 15/2} transition of Er{sup 3+}, although both green and red emissions could be detected. It was also found that the green and red emissions originated the two photon processes, and the ground-state absorption (GSA), excited-state absorption (ESA) and energy transfer (ET) processes between Er{sup 3+}/Yb{sup 3+} ions and Er{sup 3+}/Er{sup 3} ions were involved in the enhanced red emission mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Attribution of PM 2.5 exposure in Beijing–Tianjin–Hebei region to emissions: implication to control strategies

The Beijing–Tianjin–Hebei (BTH) region is one of the most heavily polluted regions in China, with both high PM 2.5 concentrations and a high population density. A quantitative source-receptor relationship can provide valuable insights that can inform effective emission control strategies. Both source apportionment (SA) and source sensitivity (SS) can provide such information from different perspectives. In this study, both methods are applied in northern China to identify the most significant emission categories and source regions for PM 2.5 exposure in BTH in 2013. Despite their differences, both models show similar distribution patterns for population and simulated PM 2.5 concentrations, resulting in overall high PM 2.5 exposure values (approximately 110 μg/m 3 ) and particularly high exposure values during the winter (approximately 200 μg/m 3 ). Both methods show that local emissions play a dominant role (70%), with some contribution from surrounding provinces (e.g., Shandong) via regional transport. The two methods also agree on the priority of local emission controls: both identify industrial, residential, and agricultural emissions as the top three categories that should be controlled locally. In addition, the effect of controlling agricultural ammonia emissions is approximately doubled when the co-benefits of reducing nitrate are considered. In conclusion, the synthesis of SA and SS for addressing specific categories of emissions provides a quantitative basis for the development of emission control strategies and policies for controlling PM 2.5 in China.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

Indicators of carbon alteration (ICAs) suggest patterns in reservoir methane emissions

Reservoir operations influence emissions via multiple causal pathways. In this paper, we quantify indicators of carbon alteration (ICAs) focused on methane. ICAs were chosen to reflect the potential for methane emission along four causal pathways: 1) water column mixing, 2) wet-dry cycles in sediment, 3) sediment redistribution, and 4) vegetation. We developed algorithms to calculate ICAs for three reservoirs along a longitudinal gradient in the Tennessee River basin of the southeast US. The ICAs revealed interesting longitudinal patterns. Indicators of both methane production and destruction increased downstream. The potential for ebullitive methane emissions driven by sub-daily water level fluctuations and emissions mediated by vegetation were higher in downstream mainstem reservoirs than in the upstream tributary reservoir. Along the remaining two pathways, longitudinal patterns were equivocal (sediment pathway) or suggested decreased emissions downstream (water-column mixing). We also observed seasonal patterns and, by combining ICAs, inferred times when ramping could be achieved with lower risk of emissions. The ICAs demonstrated here are the first step in quantifying mechanistic relationships between reservoir operation and methane emissions. In future, they may lead to improved operations in reservoir cascades and regional-scale estimates of emissions that account for differences among reservoirs.

Greenhouse gases↗