We estimate postmeter methane (CH) emissions from California's residential natural gas (NG) system using measurements and analysis from a sample of homes and appliances. Quiescent whole-house emissions (i.e., pipe leaks and pilot lights) were measured using a mass balance method in 75 California homes, while CH to CO emission ratios were measured for steady operation of individual combustion appliances and, separately, for transient operation of three tankless water heaters. Measured quiescent whole-house emissions are typically <1 g CH/day, though they exhibit long-tailed gamma distributions containing values >10 g CH/day. Most operating appliances yield undetectable CH to CO enhancements in steady operation (<0.01% of gas consumed), though storage water heaters and stovetops exhibit long-tailed gamma distributions containing high values (∼1-3% of gas consumed), and transients are observed for the tankless heaters. Extrapolating results to the state-level using Bayesian Markov chain Monte Carlo sampling combined with California housing statistics and gas use information suggests quiescent house leakage of 23.4 (13.7-45.6, at 95% confidence) Gg CH, with pilot lights contributing ∼30%. Emissions from steady operation of appliances and their pilots are 13.3 (6.6-37.1) Gg CH/yr, an order of magnitude larger than current inventory estimates, with transients likely increasing appliance emissions further. Together, emissions from residential NG are 35.7 (21.7-64.0) Gg CH/yr, equivalent to ∼15% of California's NG CH emissions, suggesting leak repair, improvement of combustion appliances, and adoption of nonfossil energy heating sources can help California meet its 2050 climate goals.
The direct breakup of 70-MeV 7 Li scattered from a l20 Sn target is investigated at forward angles. Inside the grazing angle, it is found that the breakup is dominated by the Coulomb interaction between projectile and target.PACS numbers: 25.70.NpThe study of the breakup of light-ion projectiles such as 6 Li and 7 Li is of special interest since the simple cluster nature of these nuclei considerably simplifies calculations concerning the breakup process. Thus using the a-t cluster description for 7 Li in an adiabatic calculation, Thompson and Nagarajan 1 concluded that the direct breakup of 70-MeV 7 Li into the a + t channel was mainly due to the differential nuclear force between the 208 Pb target and the projectile fragments. However, a subsequent study of inelastic scattering of 68-MeV 7 Li from 208 Pb, where a similar cluster-adiabatic calculation was used, showed that the Coulomb interaction becomes increasingly important for smaller angles. 2 This therefore raises the question as to the importance of the Coulomb interaction for projectile breakup at forward scattering angles. In this Letter we present new evidence that, at forward angles, the direct breakup of 70-MeV 7 Li on 120 Sn is primarily due to the Coloumb interaction between projectile and target.The experiment was undertaken by use of the 20-MV NSF tandem accelerator at Daresbury. Since we specifically wished to study small relative energies between the emitted a and t fragments, the two solid-state detector telescopes were placed in close vertical geometry. 3 The collimators were 10 mm x 8 mm and the vertical separation between their centers was 15 mm. The collimators were placed at 115 mm from the target, except at the most forward angle of 11.5°, where they were at 150 mm. The target was isotopically pure 120 Sn of 4 mg/cm 2 thickness.The energy spectra of a particles for events where the total energy of the coincident a and t particles corresponded to the target being left in its ground state are shown in Figs. Kb)-1(d). The spectra for the more backward angles are dominated by a pair of peaks associated with the kinematic solutions for the reaction 120 Sn( 7 Li, 7 Li4. 63 -• a + /) 120 Sn gs .. The center-of-mass (cm.) energy of the a-rpair, e r , for a given a energy, is shown on the top axis. 500 400 ^300 ^200 100 0 400 ^300 D O ^200 100 0 80 £60 D O ^40 20 0 20 £15 D O <-> 10 e (MeV)2. 16 2. 16 310 ITO 0129 f. 0 3T6 a) Monte-Carlo S i mu Lat i on 120c ,7. 7. * s 120c bn ( L i . Li, ,,->a + t) bn ' 4, 63 gs E, =70MeV lab 8 =22.0° ,, 120c 7 , 7 , * . 120c b) Sn (Li. LI -»ot + t) bn E, =70MeV 6, =22. 0° c)6lab=:15. 0° 20. 0 30. 0 40. 0 50. 0 E (MeV) 60.0 FIG. 1. (a) a-energy spectrum for sequential breakup of 7 Li using a Monte Carlo simulation, (b)-(d) Experimental a-energy spectra of the reaction 120 Sn( 7 Li, 7 Li* -a + r) 120 Sn g . s . at 22°, 15°, and 11.5°.
In order to address the health risks and climate impacts associated with pollution from cooking on biomass fires, researchers have focused on designing new cookstoves that improve cooking performance and reduce harmful emissions, specifically particulate matter (PM). One method for improving cooking performance and reducing emissions is using air injection to increase turbulence of unburned gases in the combustion zone. Although air injection reduces total PM mass emissions, the effect on PM size-distribution and number concentration has not been thoroughly investigated. Using two new wood-burning cookstove designs from Lawrence Berkeley National Laboratory, this research explores the effect of air injection on cooking performance, PM and gaseous emissions, and PM size distribution and number concentration.Both cookstoves were created using the Berkeley-Darfur Stove as the base platform to isolate the effects of air injection. The thermal performance, gaseous emissions, PM mass emissions, and particle concentrations (ranging from 5 nm to 10 µm in diameter) of the cookstoves were measured during multiple high-power cooking tests. The results indicate that air injection improves cookstove performance and reduces total PM mass but increases total ultrafine (less than 100 nm in diameter) PM concentration over the course of high-power cooking.
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