Volatile Chemical Product Enhancements to Criteria Pollutants in the United States
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54 ENVIRONMENTAL SCIENCES↗
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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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Gas and Propane Combustion from Stoves Emits Benzene and Increases Indoor Air Pollution
Exposure pathways to the carcinogen benzene are well-established from tobacco smoke, oil and gas development, refining, gasoline pumping, and gasoline and diesel combustion. Combustion has also been linked to the formation of nitrogen dioxide, carbon monoxide, and formaldehyde indoors from gas stoves. To our knowledge, however, no research has quantified the formation of benzene indoors from gas combustion by stoves. Across 87 homes in California and Colorado, natural gas and propane combustion emitted detectable and repeatable levels of benzene that in some homes raised indoor benzene concentrations above well-established health benchmarks. Mean benzene emissions from gas and propane burners on high and ovens set to 350 °F ranged from 2.8 to 6.5 μg min –1 , 10 to 25 times higher than emissions from electric coil and radiant alternatives; neither induction stoves nor the food being cooked emitted detectable benzene. Benzene produced by gas and propane stoves also migrated throughout homes, in some cases elevating bedroom benzene concentrations above chronic health benchmarks for hours after the stove was turned off. Combustion of gas and propane from stoves may be a substantial benzene exposure pathway and can reduce indoor air quality.
54 ENVIRONMENTAL SCIENCES↗
Redox Fluctuations and Organic Complexation Govern Uranium Redistribution from U(IV)-Phosphate Minerals in a Mining-Polluted Wetland Soil, Brittany, France
Wetlands have been proposed to naturally attenuate U transfers in the environment via U complexation by organic matter and potential U reduction. However, U mobility may depend on the identity of particulate/dissolved uranium source materials and their redox sensitivity. Here, we examined the fate of uranium in a highly contaminated wetland (up to 4500 mg·kg –1 U) impacted by former mine water discharges. Bulk U L III -EXAFS and (micro-)XANES combined with SEM-EDXS analyses of undisturbed soil cores show a sharp U redox boundary at the water table, together with a major U redistribution from U(IV)-minerals to U(VI)-organic matter complexes. Above the water table, U is fully oxidized into mono- and bidentate U(VI)-carboxyl and monodentate U(VI)-phosphoryl complexes. Minute amounts of U(VI)-phosphate minerals are also observed. Below the water table, U is fully reduced and is partitioned between U(IV)-phosphate minerals (i.e., ningyoite and a lermontovite-like phase), and bidentate U(IV)-phosphoryl and monodentate U(IV)-carboxyl complexes. Such a U redistribution from U-minerals inherited from mine water discharge deposits could result from redox cycling nearby the water table fluctuation zone. In conclusion, oxidative dissolution of U(IV)-phosphate minerals could have led to U(VI)-organic matter complexation, followed by subsequent reduction into U(IV)-organic complexes. However, uranium(IV) minerals could have been preserved in permanently waterlogged soil.
54 ENVIRONMENTAL SCIENCES↗
Organic pollutant photodecomposition by Ag/KNbO 3 nanocomposites: A combined experimental and theoretical study
In this study, Ag nanoparticles supported on well-defined perovskite orthorhombic KNbO 3 nanowires are synthesized via facile photoreduction and systematically characterized by XRD, Raman, DRUV–vis, XPS, PL, TEM, HRTEM, and HAADF-STEM. The photoreactivity of Ag/KNbO 3 nanocomposites as a function of Ag contents (0.4–2.8 wt %) is assessed toward aqueous rhodamine B degradation under UV- and visible-light, respectively. It is found that the UV-induced photoreactivity initially increases and then decreases with increasing Ag contents. At an optimal Ag content (ca. 1.7 wt %), the greatest photoreactivity is achieved under UV light, with the photocatalytic reaction rate of 1.7 wt % Ag/KNbO 3 exceeding that of pristine KNbO 3 by a factor of ca. 13. In contrast, visible light-induced photoreactivity monotonically increases with increasing Ag contents in the range of 0.4–2.8 wt %. On the basis of the detected active species and intermediate products in the photocatalytic processes, conjugated structure cleavage and N-deethylation are revealed to be the respective predominant pathway under UV and visible-light illumination. To gain an insight into the observed photoreactivity, the electronic properties of Ag/KNbO 3 have been investigated using spin-polarized DFT calculations. Herein, Ag extended adlayers (1–4 ML) on the slab models of KNbO 3 (101) are employed to mimic large supported Ag nanoparticles. A Bader analysis of the electron density shows a small net charge transfer (ca. 0.1 e) from KNbO 3 to Ag. The electron localization function of Ag/KNbO 3 (101) illustrates that Ag adlayers with thickness larger than 2 ML are essentially metallic, and weak polarization occurs at the interface. In addition, the metallic Ag adlayers generate a continuum of Ag bandgap states, which play a key role in determining different Ag content-dependent behavior between UV and visible-light illumination.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Tea ( Camellia sinensis ) Extract-Mediated Green Synthesis of Co 3 O 4 and Co 3 O 4 @Graphene Nanocomposites for Multifunctional Applications in Pollutant Degradation, Sensing, and Energy Storage
A novel solution-mixing method was proposed to synthesize Co 3 O 4 /graphene nanocomposites (Co 3 O 4 @Gr) using a green tea leaf (Camellia sinensis) extract as the reducing agent. XRD analysis shows that the as-prepared Co 3 O 4 @Gr exhibits a cubic spinel crystal structure. From morphological analysis, the obtained Co 3 O 4 NS forms spherical clusters that are uniformly distributed on the graphene surface. FT-IR and Raman analyses confirmed the strong molecular and vibrational interactions between the Co 3 O 4 NS and Gr. The suppressed PL intensity peak of the Co 3 O 4 @Gr NCs indicated significant inhibition in the recombination of charge carriers between the hybrid orbitals within the composites. As a result, the catalytic efficiency of Co 3 O 4 @Gr NCs increased to 80% compared to pristine Co 3 O 4 , which exhibited only 45% efficiency against methylene blue (MB) dye. Moreover, the as-prepared NCs exhibited a detection limit of 0.01−224 μM, demonstrating a superior low-DPA detection with high sensitivity. The Co 3 O 4 @Gr/GCE exhibits admirable selectivity for various pesticides, fungicides, and metal ions, with outstanding reproducibility and stability. From electrochemical investigations, the highest specific capacitance values of the as-synthesized Co 3 O 4 @Gr were 349 F/g at a scan rate of 5 mV/s and 158 F/g at a current density of 1 A/g.
Capacitors↗
Analysis of Hypoxia and Sensitivity to Nutrient Pollution in Salish Sea
We report that increasing levels of nutrients, persistent hypoxia, harmful algal blooms, and increased frequency of fish kills are degrading the ecological health of the Salish Sea. An improved version of a diagnostic hydrodynamic and biogeochemical model (nutrients, phytoplankton, carbon, dissolved oxygen, pH) of the Salish Sea has been developed with the ability to simulate characteristic circulation and water quality features. Sensitivity tests were conducted to assess the responsiveness of the system to land-based (rivers and wastewater sources) nutrient loading. The influence of Fraser River on the magnitude of estuarine exchange with the Pacific Ocean and nearshore habitat was examined given that it contributes nearly half of the total freshwater discharged to the Salish Sea. A large region of hypoxia in Hood Canal that extends over 30–40 km during its peak was reproduced and attributed primarily to the existence of a two-layer classic fjord-type circulation and a nearly stagnant deep bottom layer that occupies nearly 60% of the water column. Nitrate mass in the euphotic zone from land-based and oceanic sources is depleted to near-zero limiting levels during summer. Under such conditions, the Salish Sea is responsive to changes in nutrient loads entering the euphotic zone directly. Lastly, a hypothetical scenario involving the elimination of land-based nutrient sources results in notable water-quality improvement, featuring a reduction in algal biomass (≈5.4%), reduction in sediment oxygen demand (≈17.1%), and significant reduction in hypoxic area (≈39%) and exposure in area-days to bottom layer hypoxia (≈62%) within the Salish Sea.
54 ENVIRONMENTAL SCIENCES↗
A Strong Anthropogenic Black Carbon Forcing Constrained by Pollution Trends Over China
Estimates of the effective radiative forcing from aerosol-radiation interaction (ERF ari ) of anthropogenic Black Carbon (BC) have been disputable and require better constraints. Here we find a substantial decline in atmospheric absorption of −5.79Wm −2 decade −1 over eastern central China (ECC) responding to recent anthropogenic BC emission reductions. By combining the observational finding with advances from Coupled Model Intercomparison Project phase6 (CMIP6), we identify an emergent constraint on the ERF ari of anthropogenic BC. We show that across CMIP6 models the simulated trends correlate well with simulated annual mean shortwave atmospheric absorption by anthropogenic BC over China. Making use of this emergent relationship allows us to constrain the aerosol absorption optical depth of anthropogenic BC and further provide a constrained range of 2.4–3.0 Wm −2 for its top-of-atmosphere ERF ari over China, higher than existing estimates. Furthermore, our work supports a strong warming effect of BC over China, and highlights the need to improve BC simulations over source regions.
CMIP6 models↗
Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution
Not provided.
Science & Technology - Other Topics↗
Linking mixtures of air pollution exposures and preterm birth with a self-organizing map
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Kelly, Brenna [University of Utah, Salt Lake City,↗
Ozone pollution reduction partially offsets the negative impact of climate change mitigation efforts on global hunger
Studies warning of the potential negative effects of climate mitigation on food security through the competing use of land for bioenergy and afforestation have overlooked the impact of reduced ozone and its potential enhancement of crop yields. Here we use six global agro-economic models to compare the impacts of climate change with climate mitigation policy and ozone reduction on agriculture. We find that ozone reduction could reduce the negative impact of a 1.5 °C-consistent climate change mitigation policy on global hunger by 15% in 2050. Sub-Saharan Africa and India, where hunger is most severe, account for 56% of this global reduction. Our findings indicate that the negative effects of climate mitigation on global hunger could be partially offset by the ozone reduction impact.
54 ENVIRONMENTAL SCIENCES↗
Buckybowls as gas adsorbents: binding of gaseous pollutants and their electric-field induced release
Here, the adsorption of nitric oxide and nitrogen dioxide (NO x ) to the Buckybowls sumanene and corannulene was investigated. Binding energies were up to 1.8x larger than for coronene as the planar analogue, demonstrating the advantages of Buckybowls for gas adsorption. In agreement with previous reports on carbon dioxide and methane adsorption, the favorable binding energies for NO x were shown to be associated with the curvature of the Buckybowls. It is shown that applying an electric field along the bowl symmetry axis modifies the bowl curvatures and impacts adsorbate binding energies, including the potential to desorb adsorbates. As a proof of concept, it is shown that applying electric fields of different strengths and orientations selectively controls sumanene's preference to bind nitric oxide, nitrogen dioxide, and carbon dioxide, suggesting potential applications for dynamically tunable gas adsorption. Moreover, it is demonstrated that adsorbates can be desorbed by applying suitable electric field strengths, allowing cleaning of the Buckybowls for renewed usage.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Electro-hydrodynamics and kinetic modelling of polluted air flow activated by multi-tip-to-plane corona discharge
The present paper is devoted to the 2D simulation of an Atmospheric Corona Discharge Reactor (ACDR) involving 10 pins powered by a DC high voltage and positioned 7 mm above a grounded metallic plane. The corona reactor is periodically crossed by thin mono filamentary streamers with a natural repetition frequency of some tens of kHz. The simulation involves the electro-dynamic, chemical kinetic, and neutral gas hydrodynamic phenomena that influence the kinetics of the chemical species transformation. Each discharge stage (including the primary and the secondary streamers development and the resulting thermal shock) lasts about one hundred nanoseconds while the post-discharge stages occurring between two successive discharge phases last one hundred microseconds. The ACDR is crossed by a lateral air flow including 400 ppm of NO. During the considered time scale of 10 ms, one hundred discharge/post-discharge cycles are simulated. The simulation involves the radical formation and thermal exchange between the discharges and the background gas. The results show how the successive discharges activate the flow gas and how the induced turbulence phenomena affect the redistribution of the thermal energy and the chemical kinetics inside the ACDR.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗