Isotopic characterization of nitrogen oxides (NO\u3ci\u3ex\u3c/i\u3e), nitrous acid (HONO), and nitrate (\u3ci\u3ep\u3c/i\u3eNO3-) from laboratory biomass burning during FIREX

New techniques have recently been developed and applied to capture reactive nitrogen species, including nitrogen oxides (NOx D NOCNO2), nitrous acid (HONO), nitric acid (HNO3), and particulate nitrate (pNO3 ), for accurate measurement of their isotopic composition. Here, we report – for the first time – the isotopic composition of HONO from biomass burning (BB) emissions collected during the Fire Influence on Regional to Global Environments Experiment (FIREX, later evolved into FIREX-AQ) at the Missoula Fire Science Laboratory in the fall of 2016. We used our newly developed annular denuder system (ADS), which was verified to completely capture HONO associated with BB in comparison with four other high-timeresolution concentration measurement techniques, including mist chamber–ion chromatography (MC–IC), open-path Fourier transform infrared spectroscopy (OP-FTIR), cavityenhanced spectroscopy (CES), and proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF)

Isotopic characterization of nitrogen oxides (NOx), nitrous acid (HONO), and nitrate (pNO3−) from laboratory biomass burning during FIREX

New techniques have recently been developed and applied to capture reactive nitrogen species, including nitrogen oxides (NOx=NO+NO2), nitrous acid (HONO), nitric acid (HNO3), and particulate nitrate (pNO−3), for accurate measurement of their isotopic composition. Here, we report – for the first time – the isotopic composition of HONO from biomass burning (BB) emissions collected during the Fire Influence on Regional to Global Environments Experiment (FIREX, later evolved into FIREX-AQ) at the Missoula Fire Science Laboratory in the fall of 2016. We used our newly developed annular denuder system (ADS), which was verified to completely capture HONO associated with BB in comparison with four other high-time-resolution concentration measurement techniques, including mist chamber–ion chromatography (MC–IC), open-path Fourier transform infrared spectroscopy (OP-FTIR), cavity-enhanced spectroscopy (CES), and proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF). In 20 “stack” fires (direct emission within ∼5 s of production by the fire) that burned various biomass materials from the western US, δ15N–NOx ranges from −4.3 ‰ to +7.0 ‰, falling near the middle of the range reported in previous work. The first measurements of δ15N–HONO and δ18O–HONO in biomass burning smoke reveal a range of −5.3 ‰ to +5.8 ‰ and +5.2 ‰ to +15.2 ‰, respectively. Both HONO and NOx are sourced from N in the biomass fuel, and δ15N–HONO and δ15N–NOx are strongly correlated (R2=0.89, p\u3c0.001), suggesting HONO is directly formed via subsequent chain reactions of NOx emitted from biomass combustion. Only 5 of 20 pNO−3 samples had a sufficient amount for isotopic analysis and showed δ15N and δ18O of pNO−3 ranging from −10.6 ‰ to −7.4 ‰ and +11.5 ‰ to +14.8 ‰, respectively. Our δ15N of NOx, HONO, and pNO−3 ranges can serve as important biomass burning source signatures, useful for constraining emissions of these species in environmental applications. The δ18O of HONO and NO−3 obtained here verify that our method is capable of determining the oxygen isotopic composition in BB plumes. The δ18O values for both of these species reflect laboratory conditions (i.e., a lack of photochemistry) and would be expected to track with the influence of different oxidation pathways in real environments. The methods used in this study will be further applied in future field studies to quantitatively track reactive nitrogen cycling in fresh and aged western US wildfire plumes

Stimulated amplification of propagating spin waves

Spin-wave amplification techniques are key to the realization of magnon-based computing concepts. We introduce a novel mechanism to amplify spin waves in magnonic nanostructures. Using the technique of rapid cooling, we create a non-equilibrium state in excess of high-energy magnons and demonstrate the stimulated amplification of an externally seeded, propagating spin wave. Using an extended kinetic model, we qualitatively show that the amplification is mediated by an effective energy flux of high energy magnons into the low energy propagating mode, driven by a non-equilibrium magnon distribution

Characteristics of brown carbon in Western United States wildfires

Brown carbon (BrC) associated with aerosol particles in western United States wildfires was measured between Jul. and Aug. 2019 onboard the NASA DC-8 research aircraft during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study. Two BrC measurement methods are investigated; highly spectrally-resolved light absorption in solvent (water and methanol) extracts of particles collected on filters and in-situ bulk aerosol particle light absorption measured at three wavelengths (405, 532, 664 nm) with a photo acoustic spectrometer (PAS). A light absorption closure analysis for wavelengths between 300 and 700 nm was performed. The combined light absorption of particle pure black carbon material, including enhancements due to internally mixed materials, plus soluble BrC and a Mie-predicted factor for conversion of soluble BrC to aerosol particle BrC, was compared to absorption spectra from a power law fit to the three PAS wavelengths. For the various parameters used, at a wavelength of roughly 400 nm they agreed, at lower wavelengths the individual component-predicted particle light absorption significantly exceeded the PAS and at higher wavelengths the PAS absorption was consistently higher, but more variable. Limitations with extrapolation of PAS data to wavelengths below 405 nm and missing BrC species of low solubility that more strongly absorb at higher wavelengths may account for the differences. Based on measurements closest to fires, the emission ratio of PAS measured BrC at 405 nm relative to carbon monoxide (CO) was on average 0.13 Mm−1 ppbv−1, emission ratios for soluble BrC are also provided. As the smoke moved away from the burning regions the evolution over time of BrC was observed to be highly complex; BrC enhancement, depletion, or constant levels with age were all observed in the first 8 hours after emission in different plumes. Within 8 hours following emissions, 4-nitrocatechol, a well characterized BrC chromophore commonly found in smoke particles, was largely depleted relative to the bulk BrC. In a descending plume where temperature increased by 15 K, 4-nitrocatechol dropped possibly due to temperature-driven evaporation, but bulk BrC remained largely unchanged. Evidence was found for reactions with ozone, or related species, as a pathway for secondary formation of BrC under both low and high oxides of nitrogen (NOx) conditions, while BrC was also observed to be bleached in regions of higher ozone and low NOx, consistent with complex behaviors of BrC observed in laboratory studies. Although the evolution of smoke in the first hours following emission is highly variable, a limited number of measurements of more aged smoke (15 to 30 hours) indicate a net loss of BrC. It is yet to be determined how the near-field BrC evolution in smoke affects the characteristics of smoke over longer time and spatial scales, where its environmental impacts are likely to be greater

Gridded isopach maps from the South Pacific and their use in interpreting the sedimentation history of the West Antarctic continental margin

Large scale maps of sediment thicknesses are essential prerequisites for the next generation of high resolution paleobathymetric reconstructions. In addition, maps of sediment thicknesses on continental margins are useful for studies of terrigenous sediment supply and sediment distribution on the ocean floor. Based on a compilation of more than 10000 km of single and multichannel seismic reflection data and correlations with ocean drilling sites, we model isopach grids of the Southern Pacific margin of West Antarctica. Following recent seismic stratigraphic models, we differentiate between "pre-glacial" and "glacially transported" sediments. The subsequent modelling of sediment thickness grids allows us to compare the pre-glacial and glacial sedimentary development in the study area. Based on available drillhole dates, we estimate the onset of accumulation of glacially transported sediments to have occurred at about 10 Ma, based on approximate sediment deposition rates. The thickest glacial sediment accumulations occur in front of major glacial drainage outlets, i.e. Marguerite Trough on the western Antarctic Peninsula margin, Belgica Trough in the Bellingshausen Sea, and the trough off Pine Island Bay in the Amundsen Sea. Sedimentation rates between 140 and 170 m/m.y. are calculated for these sites

Bottom-current control on sedimentation in the western Bellingshausen Sea, West Antarctica

A set of single channel and multi channel seismic reflection profiles provide insights in the young Cenozoic sedimentation history on the continental rise of the western Bellingshausen Sea west and north of Peter I Island. This area was mainly influenced by the glacial controlled sediment supply from the continental shelf and by bottom current activity. The seismic data show northwards structural altering of a prominent sediment mound from a sediment drift structure into a oppositional orientated large channel-levee complex lying west of an erosional channel. This change indicates a northward decreasing influence of a westward flowing bottom contour current. The topography suggests Peter I Island to be the main feature for the change of the bottom current influence, acting as a barrier for the bottom current and the entrained sediment material. West of Peter I Island the eastward orientated Coriolis force remains as the affecting force which deflects suspended load of the turbidites to the west and leads to a stronger grow of the western channel-levee. Calculated sediment deposition rates based on the seismic data reveal the sediment mound as a remarkable and important sediment depocentre for young Cenozoic glacial transported and contouritic sediment material in the Bellingshausen Sea

Einfluss von glazialen Prozessen und Bodenströmungen auf die Sedimentationsprozesse am westantarktischen Kontinentalrand - Interpretation reflexionsseismischer Profile

The advances and retreats of grounded ice on the Antarctic continental shelf during glacial-interglacial cycles led to the deposition of large sediment deposits. Depositional patterns on the continental slope and rise reflect interactions between the effects of ice sheet fluctuations, mass transport processes and bottom currents. The central element of this thesis is the study of the late Cenozoic glacial history of the South Pacific continental margin of West Antarctica by interpreting the record of marine sediments there, with focus on the sedimentary successions of the outer continental shelf, slope and rise. The thesis presents the results of seismic stratigraphic analyses of multi-channel and single channel seismic reflection profiles collected on the continental margin during the course of several cruises since 1986. Seismic stratigraphic patterns are interpreted with reference to recent sedimentation models in order to differentiate between pre-glacial and glacially-influenced sediment units