This is the FLUXNET-CH4 version of the carbon flux data for the site US-Bi1 Bouldin Island Alfalfa.
Abstract Rising atmospheric CO 2 concentration ([CO 2 ]) enhances photosynthesis and reduces transpiration at the leaf, ecosystem, and global scale via the CO 2 fertilization effect. The CO 2 fertilization effect is among the most important processes for predicting the terrestrial carbon budget and future climate, yet it has been elusive to quantify. For evaluating the CO 2 fertilization effect on land photosynthesis and transpiration, we developed a technique that isolated this effect from other confounding effects, such as changes in climate, using a noisy time series of observed land-atmosphere CO 2 and water vapor exchange. Here, we evaluate the magnitude of this effect from 2000 to 2014 globally based on constraint optimization of gross primary productivity (GPP) and evapotranspiration in a canopy photosynthesis model over 104 global eddy-covariance stations. We found a consistent increase of GPP (0.138 ± 0.007% ppm −1 ; percentile per rising ppm of [CO 2 ]) and a concomitant decrease in transpiration (−0.073% ± 0.006% ppm −1 ) due to rising [CO 2 ]. Enhanced GPP from CO 2 fertilization after the baseline year 2000 is, on average, 1.2% of global GPP, 12.4 g C m −2 yr −1 or 1.8 Pg C yr −1 at the years from 2001 to 2014. Our result demonstrates that the current increase in [CO 2 ] could potentially explain the recent land CO 2 sink at the global scale.
The thermal dehydrogenation of butane to butene and hydrogen was investigated over Pt nanoparticles supported on calcined hydrotalcite containing indium, Mg(In)(Al)O. Prior work has shown that upon reduction in H2 at temperatures above 673 K, bimetallic Pt-In particles of are formed, as evidenced by XANES and EXAFS. The performance of Pt/Mg(In)(Al)O for butane dehydrogenation was found to be highly dependent on the bulk In/Pt ratio. The optimal ratio was found to be between 0.33 and 0.88, yielding >95% selectivity to butenes. Hydrogen co-fed with butane was shown to suppress coke formation and catalyst deactivation, a ratio of H2/C 4H10 = 2.5 providing the best catalytic performance. Regeneration of catalysts after removal of accumulated carbon and reduction in H2 restored the original catalyst activity and selectivity. Butane dehydrogenation above 803 K resulted in higher formation of butadiene, a known precursor to coke. No evidence for butane cracking was found to occur on Pt/Mg(In)(Al)O due to moderately basic nature of the support. The present study shows that Pt/Mg(In)(Al)O exhibits superior performance for butane dehydrogenation compared to supported Pt catalysts promoted with Sn, Ge, Pb, and In prepared by successive incipient wetness impregnation of the Pt and promoter precursors. © 2013 Elsevier B.V.
The interactions of CO and H/sub 2/ with Pd/SiO/sub 2/ promoted with Li, Na, K, Rb, and Cs have been investigated using temperature-programmed desorption and temperature-programmed surface reaction. Introduction of the promoter following the preparation of the Pd/SiO/sub 2/ catalyst causes a small increase (similarly ordered 7%) in the dispersion of the Pd particles. Reduction of the promoted catalysts removes a significant quantity of oxygen from the promoter, but only a small portion of the promoter appears to cover the Pd particles. Alkali promotion of Pd/SiO/sub 2/ does not significantly influence the amounts of H/sub 2/ and CO that can be adsorbed on the metal. The alkali promoters have a slight influence on the distribution of H/sub 2/ adstates but cause a significant change in the distribution of CO adstates. For low reduction temperatures, alkali promotion of Pd/SiO/sub 2/ decreases the activity of Pd for the dissociation of CO. However, increasing the reduction temperature increases the CO dissociation activity of the promoted samples due to the increased degree of reduction of the promoter. This enhanced dissociation activity is reversed by the reoxidation of the promoter by the H/sub 2/O or CO/sub 2/ formed under reaction conditions. The nascent carbon formedmore » by CO dissociation on alkali-promoted Pd/SiO/sub 2/ is less reactive than that on unpromoted Pd/SiO/sub 2/, and the promoted catalysts have a lower activity for CH/sub 4/ synthesis relative to that for unpromoted Pd/SiO/sub 2/ decreasing in the order: unpromoted > Li > Na > K > Rb > Cs. 49 references.« less
This is the FLUXNET-CH4 version of the carbon flux data for the site US-Bi2 Bouldin Island corn.
Abstract The activity of Rh supported on SiO 2 , Al 2 O 3 , MgO, La 2 O 3 , and TiO 2 for NO reduction by CO and H 2 has been investigated in regard to automotive emission.
Naturally occurring cellulose is crystalline as a consequence of the strong interactions between the glucan chains that comprise it and therefore is insoluble in most solvents. One of the few solvent systems able to dissolve cellulose is lithium chloride (LiCl) dissolved in N,N-dimethylacetamide (DMA). By an integrated application of all-atom molecular dynamics (MD) simulations, reaction path optimization, free-energy calculations, and a force-matching analysis of coarse-grained atomistic simulations, we establish that DMA-mediated preferential interactions of Li(+) cations and Cl(-) anions with glucan chains enable cellulose dissolution in LiCl/DMA. The relatively weak solvation of Li(+), Cl(-), and glucan chains by DMA results in strong effective interactions of Li(+) and Cl(-) ions with the glucans, leading to cellulose dissolution. The small size of the Li(+) cations allows them to strongly couple to multiple interaction sites on the glucan chains of cellulose, including the spatially restricted regions around the ether linkages connecting neighboring glucose residues. Li(+) cations were thus identified as the main component responsible for driving cellulose dissolution. The mechanism for explaining the solubility of cellulose in the LiCl/DMA system deduced from the analysis of atomistic-scale simulations conducted in this work is also consistent with most of the empirical observations related to cellulose dissolution in salt/amide solvent systems.
Abstract There are few observational studies measuring the ecosystem‐scale productivity effects of changes in incident diffuse photosynthetically active radiation (PAR diffuse ), especially related to wildfire smoke. Climate change‐induced increases to the duration and intensity of fire conditions have made smoke a common occurrence across western North America, with largely unquantified ecosystem feedbacks. Under equivalent amounts of radiation, increased atmospheric particulate matter could lead to a boost in productivity as scattering redistributes photons throughout multilayer canopies. In this work, we leverage a meso‐network of eddy covariance measurement sites across a unique array of managed and restored C 3 and C 4 canopy types to understand how recent wildfire smoke affected ecosystem productivity during the summer of 2018, an especially smoky year in the agriculturally productive Central Valley. We find that diffuse PAR diffuse increased by more than a third compared to the previous growing season, while total PAR was only slightly diminished. These conditions caused nearly a doubling of light use efficiency over the range of diffuse fraction observed, with the highest sensitivity to diffuse fraction exhibited by corn and alfalfa crops. We utilized an empirical model to assess the trade‐off between enhanced diffuse fraction and reduced total PAR. Under mean radiation conditions, daily integrated gross ecosystem productivity increased by 1.2–4.2% compared to the previous growing season. Finally, we explore the potential negative effect of heightened ozone, a copollutant often associated with wildfire. In addition to the effects of wildfire smoke, the results of this natural experiment can help validate future predictions of aerosol‐productivity feedbacks.
Because of human action, the Earth has entered an era where profound changes in the global environment are creating novel conditions that will be discernable far into the future. One consequence may be a large reduction of the Earth's biodiversity, potentially representing a sixth mass extinction. With effective stewardship, the global change drivers that threaten the Earth's biota could be alleviated, but this requires clear understanding of the drivers, their interactions, and how they impact ecological communities. This review identifies 10 anthropogenic global change drivers and discusses how six of the drivers (atmospheric CO2 enrichment, climate change, land transformation, species exploitation, exotic species invasions, eutrophication) impact Earth's biodiversity. Driver impacts on a particular species could be positive or negative. In either case, they initiate secondary responses that cascade along ecological lines of connection and in doing so magnify the initial impact. The unique nature of the threat to the Earth's biodiversity is not simply due to the magnitude of each driver, but due to the speed of change, the novelty of the drivers, and their interactions. Emphasizing one driver, notably climate change, is problematic because the other global change drivers also degrade biodiversity and together threaten the stability of the biosphere. As the main academic journal addressing global change effects on living systems, GCB is well positioned to provide leadership in solving the global change challenge. If humanity cannot meet the challenge, then GCB is positioned to serve as a leading chronicle of the sixth mass extinction to occur on planet Earth.© 2019 John Wiley & Sons Ltd. PMID: 31663217 Funding information This work was supported by: Natural Science and Engineering Research Council of Canada, International Grant ID: RGPIN-2017-06476
Abstract Synthesis of transportation fuel from lignocellulosic biomass is an attractive solution to the green alternative‐energy problem. The production of biodiesel, in particular, involves the process of upgrading biomass‐derived small molecules to diesel precursors containing a specific carbon range (C 11 –C 23 ). Herein, a carbon‐upgrading process utilizing an acid‐catalyzed condensation of furanic platform molecules from biomass is described. Various types of sulfonic acid catalysts have been evaluated for this process, including biphasic and solid supported catalysts. A silica‐bound alkyl sulfonic acid catalyst has been developed for promoting carbon–carbon bond formation of biomass‐derived carbonyl compounds with 2‐methylfuran. This hydrophobic solid acid catalyst exhibits activity and selectivity that are comparable to those of a soluble acid catalyst. The catalyst can be readily recovered and recycled, possesses appreciable hydrolytic stability in the presence of water, and retains its acidity over multiple reaction cycles. Application of this catalyst to biomass‐derived platform molecules led to the synthesis of a variety of furanic compounds, which are potential biodiesel precursors.
We report the successful application of a templating approach employing ordered mesoporous carbon to the synthesis of BiVO4, Bi2Mo3O12, and Bi0.85V0.55Mo0.45O4 and the performance of these materials as catalysts for the oxidation of propene to acrolein. Ordered mesoporous carbon templates were used to control the nucleation and growth of the mixed metal oxide crystals, allowing higher final surface areas to be obtained. The resulting materials were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and BET surface area analysis. The surface area of the mixed metal oxide catalysts was found to depend on the type of mesoporous silica used to prepare the carbon template and on the conditions under which the carbon template was formed. Through an appropriate choice of template, the surface areas of the mixed metal oxides exceeded 15 m(2)/g. Catalytic testing revealed that materials produced via templating in ordered mesoporous carbon had per-gram activities that were up to 85 times higher than those produced by a conventional hydrothermal synthesis and exhibited stable catalytic activities over 24 h.
The swelling and dissolution of thin film poly(methyl methacrylate), PMMA, in methyl isobutyl ketone (MIBK), and in solvent/nonsolvent mixtures of MIBK/methanol and methyl ethyl ketone/isopropanol have been investigated. Films were monitored using in situ ellipsometry. Parametric studies of the effects of molecular weight, molecular weight distribution, softbaking quench rate, solvent size, and temperature were performed with MIBK. These parameters were shown to have a significant effect on dissolution. The effects of solvent composition and temperature on swelling and dissolution were investigated with the binary solvents. Ternary diagrams based on Flory-Huggins interaction parameters were used to interpret the thermodynamics of swelling and dissolution. A narrow transition region (NTR) where the developer changed from a swelling to dissolving agent with a small change in composition or temperature was observed.
