Our understanding of tree stem methane (CH4) emissions is evolving rapidly. Few studies have combined seasonal measurements of soil, water and tree stem CH4 emissions from forested wetlands, inhibiting our capacity to constrain the tree stem CH4 flux contribution to total wetland CH4 flux. Here we present annual data from a subtropical freshwater Melaleuca quinquenervia wetland forest, spanning an elevational topo-gradient (Lower, Transitional and Upper zones). Eight field-campaigns captured an annual hydrological flood-dry-flood cycle, measuring stem fluxes on 30 trees, from four stem heights, and up to 30 adjacent soil or water CH4 fluxes per campaign. Tree stem CH4 fluxes ranged several orders of magnitude between hydrological seasons and topo-gradient zones, spanning from small CH4 uptake to ~203 mmol m-2 d-1. Soil CH4 fluxes were similarly dynamic and shifted from maximal CH4 emission (saturated soil) to uptake (dry soil). In Lower and Transitional zones respectively, tree stem CH4 contribution to the net ecosystem flux was greatest during flooded conditions (49.9 and 70.2 %) but less important during dry periods (3.1 and 28.2 %). Minor tree stem emissions from the Upper elevation zone still offset the Upper zone CH4 soil sink capacity by ~51% during dry conditions. Water table height was the strongest driver of tree stem CH4 fluxes, however tree emissions peaked once the soil was inundated and did not increase with further water depth. This study highlights the importance of quantifying the wetland tree stem CH4 emissions pathway as an important and seasonally oscillating component of wetland CH4 budgets.

The long-term net sink of carbon (C), nitrogen (N) and greenhouse gases (GHGs) in the northern permafrost region is projected to weaken or shift under climate change. But large uncertainties remain, even on present-day GHG budgets. We compare bottom-up (data-driven upscaling, process-based models) and top-down budgets (atmospheric inversion models) of the main GHGs (CO2, CH4, and N2O) and lateral fluxes of C and N across the region over 2000-2020. Bottom-up approaches estimate higher land to atmosphere fluxes for all GHGs compared to top-down atmospheric inversions. Both bottom-up and top-down approaches respectively show a net sink of CO2 in natural ecosystems (-31 (-667, 559) and -587 (-862, -312), respectively) but sources of CH4 (38 (23, 53) and 15 (11, 18) Tg CH4-C yr-1) and N2O (0.6 (0.03, 1.2) and 0.09 (-0.19, 0.37) Tg N2O-N yr-1) in natural ecosystems. Assuming equal weight to bottom-up and top-down budgets and including anthropogenic emissions, the combined GHG budget is a source of 147 (-492, 759) Tg CO2-Ceq yr-1 (GWP100). A net CO2 sink in boreal forests and wetlands is offset by CO2 emissions from inland waters and CH4 emissions from wetlands and inland waters, with a smaller additional warming from N2O emissions. Priorities for future research include representation of inland waters in process-based models and compilation of process-model ensembles for CH4 and N2O. Discrepancies between bottom-up and top-down methods call for analyses of how prior flux ensembles impact inversion budgets, more in-situ flux observations and improved resolution in upscaling.

Denitrification-Decomposition (DNDC) model, a mathematical construct that simulates biogeochemical processes including carbon and nitrogen dynamics, plant growth, and microbial activity across various ecosystems. The discourse includes an examination of the model’s developmental trajectory, with attention given to adaptations created for diverse ecosystems, regions, specific crops, and modular configurations. We additionally delve into the validation processes of the DNDC model and its broader applications across different fields. Despite the model’s extensive usage in previous studies, there has been a lack of critical, comprehensive evaluation of its merits and demerits. This paper aim to address this gap, providing a thorough critique and review of the DNDC model. In our discussion, we present a balanced overview of the DNDC model’s current strengths and weaknesses, and offer insights into its potential future developments. The ultimate goal of this paper is twofold. Firstly, we aim to provide guidance to researchers and practitioners who are either currently employing or considering the use of the DNDC model. Secondly, our critique and analysis is intended to be a constructive contribution towards the model’s future refinement and development.

X-ray amorphous material that is variably Mg/Fe/Si-rich and Al-poor and that likely contains secondary alteration products is prevalent in Gale crater sediments and rocks (15-73 wt.%). However, the structure and origin of these materials and their implications for past environmental conditions remain unknown. In this study, we use transmission electron microscopy and synchrotron microprobe analyses to examine Mg/Fe/Si-rich and Al-poor ultramafic soils from the warm Mediterranean climate Klamath Mountains of California and cold subarctic climate Tablelands of Newfoundland, Canada to help interpret environmental conditions during the formation of chemically similar X-ray amorphous material in Gale crater, Mars. Primary glass is absent from the Klamath Mountains and Tablelands materials; secondary X-ray amorphous material includes globular amorphous silica and chemically heterogeneous nanospherical amorphous material and nanocrystalline phases. Globular amorphous silica is only present in soils that undergo extensive periods of cyclic freezing. Fe-containing X-ray amorphous material from the subarctic Tablelands is significantly richer in Mg and Si than X-ray amorphous material from the warmer Klamath Mountains. Fe-rich nanocrystallites contain more Mg and Si in the subarctic Tablelands but are more highly Fe-enriched in the warmer Klamath Mountains. Potential secondary nanocrystalline phyllosilicates are only observed in the warmest examined soil in the Klamath Mountains. These characteristics – the presence or absence of amorphous silica, the chemical composition of X-ray amorphous material, the abundance and composition of Fe-rich nanocrystallites, and the presence or absence of secondary phyllosilicates - provide helpful identifiers to interpret past environmental conditions during the formation of X-ray amorphous material on Mars.

A 7-km wide circular structural feature on Black Mesa, Navajo Nation (Figure 1) has been proposed as representing an impact structure that formed in conjunction with nearby melt breccias. Some outcrops of mostly siliciclastic Mesaverde Group rocks on Black Mesa display various post-depositional thermometamorphic textures like melt brecciation and fusion of sand grains. Apatite fission track (AFT) analysis was applied to melt breccias and nearby unmelted sandstones to determine the age of melting at selected outcrops. For breccia sample BM-1: apatite is sparse, 1 of 9 AFT ages as young as 0 Ma (95%CI). Breccia sample BM-2B: apatite is sparse, 7 of 12 AFT ages as young as 0 Ma. Breccia sample BM-4B: 78 of 78 AFT ages as young as 0 Ma, pooled age <1 Ma. For unmelted sample BM-2A: 15 of 74 AFT ages as young as 0 Ma. Unmelted sample BM-3: 11 of 54 AFT ages as young as 0 Ma. Unmelted sample BM-4A: 76 of 87 AFT ages as young as 0 Ma. Sparse apatite likely indicates loss by thermal decomposition. A measured AFT pooled age <1 Ma for breccia sample BM-4B supports very recent melting, probably from an underground coal fire. Our evidence therefore supports an interpretation as clinker and contradicts the impact hypothesis at these outcrops.

A document by Raymond Donelick. Click on the document to view its contents.

AFT annealing parameter r mr0 relative to apatite standard B2 (Carlson et al., 1999; Ketcham et al., 1999) is re-calibrated here using a combination of natural apatite mixtures from sandstones and selected standards. The standards include well-studied DR, FC, TI, and RN-like (Ca-F-apatite end-member). A machine learning approach is used that predicts r mr0 based on independent chemical composition data from LA-ICP-MS. The c-axis-projected (e.g., Donelick et al., 1999), reduced mean length of partially annealed 252 Cf-derived FTs is measured and converted to r mr0 for each apatite grain studied. Absolute concentrations of Na, Mg, P, S, Cl, Ca, Mn, Fe, As, Sr, Y, 14 REEs, Th, U and relative concentrations of Al, Si, Sc, Br are determined for each grain by LA-ICP-MS using DR and other apatite species as matrix-matched standards (Donelick and Donelick, 2013). Of primary interest to r mr0 is: absolute Cl, Mn, Fe, Sr, ΣREEs, and annealing state of natural FTs (pre-annealed or not; t-T path dependence?); of secondary interest is relative Br, absolute Y, Th, U, and Pb-corrected UPb age (t-T path dependence?); of tertiary interest is everything else including the concentrations of individual REEs. Machine learning regression techniques applied to the data include linear regression, random forests, dense neural networks, and support vector models. We compared the validation results between these regression techniques and examine the importance of each chemical composition feature as determined by the model training. The best performing model identified so far is a random forest regressor, with a 5-fold cross validation mean absolute error of 0.057 +/-0.004 (1σ) on r mr0 .

A document by Aryav Bhesania. Click on the document to view its contents.

The distribution of Cr isotopes provides useful information to trace the source and origin of extraterrestrial samples, but it is usually influenced by high-energy cosmic rays. Since lunar and terrestrial materials have quite similar Cr isotope compositions, distinguishing the effect of cosmic rays in lunar samples is especially important. Those cosmic radiation particles (primary particles) can react with lunar materials, creating many secondary particles. Both primary and secondary particles can produce cosmogenic nuclides on the Moon. Radiation Environment and Dose at the Moon (REDMoon) is a novel GEANT4 Monte-Carlo model built to simulate the interactions of space particles with the lunar surface and subsurface content. Using this model, we simulate the production of cosmogenic Cr isotopes ($^{50}$Cr,$^{52}$Cr,$^{53}$Cr,$^{54}$Cr) at different depths of lunar surface, and compare the contribution of different reactions generating these nuclides. The results suggest that spallation reactions are the most important process producing cosmogenic Cr isotopes. We also analyze the relationship between $^{53}$Cr/$^{52}$Cr and $^{54}$Cr/$^{52}$Cr predicted by our model and compare it with different Apollo samples. As previously studied, we also find an approximate linear relationship between $\varepsilon^{53}$Cr and $\varepsilon^{54}$Cr (per 10,000 deviation of $^{53}$Cr/$^{52}$Cr and $^{54}$Cr/$^{52}$Cr ratios from the standard). Furthermore, we reveal a change of this linear relationship in different depths of lunar surface. Besides, we investigate how the slopes can be influenced by exposure age and the Fe/Cr ratio. With these additional factors carefully considered, the comparison between our modeled results and the measurements is better than previous studies.

Seismic tomography of Earth’s mantle images abundant slab remnants, often located in close proximity to active subduction systems. The impact of such remnants on the dynamics of subduction remains under explored. Here, we use simulations of multi-material free subduction in a 3-D spherical shell geometry to examine the interaction between visco-plastic slabs and remnants that are positioned above, within and below the mantle transition zone. Depending on their size, negatively buoyant remnants can set up mantle flow of similar strength and length scales as that due to active subduction. As such, we find that remnants located within a few hundred km from a slab tip can locally enhance sinking by up to a factor 2. Remnant location influences trench motion: the trench advances towards a remnant positioned in the mantle wedge region, whereas remnants in the sub-slab region enhance trench retreat. These motions aid in rotating the subducting slab and remnant towards each other, reducing the distance between them, and further enhancing the positive interaction of their mantle flow fields. In this process, the trench develops along-strike variations in shape that are dependent on the remnant’s location. Slab-remnant interactions may explain the poor correlation between subducting plate velocities and subducting plate age found in recent plate tectonic reconstructions. Our results imply that slab-remnant interactions affect the evolution of subducting slabs and trench geometry. Remnant-induced downwelling may also anchor and sustain subduction systems, facilitate subduction initiation, and contribute to plate reorganisation events.

The Atlantic Multidecadal Oscillation (AMO), Arctic Oscillation (AO), and related North Atlantic Oscillation (NAO) have been linked to multidecadal, decadal, and/or interannual sea-ice variability in the arctic, but their relative influences are still under evaluation. While instrumental AMO and reliable AO records are available since the mid-1800s and 1958, respectively, satellite sea-ice concentration datasets start only in 1979, limiting the shared timespan to study their interplay. Growth increments of the coralline algae, Clathromorphum compactum, can provide sea-ice proxy information for years prior to 1979. We present a seasonal 210-year algal record from Lancaster Sound in the Canadian Arctic Archipelago capturing low frequency AMO variability and high frequency interannual AO/NAO prior to 2000. We suggest that sea-ice variability here is strongly coupled to these large-scale climate processes, and that sea-ice cover was greater and the AO more negative in the early and late 19th century compared to the 20th.

Climate change and nitrogen (N) pollution are altering biogeochemical and ecohydrological processes in dryland watersheds, increasing N export, and threatening water quality. While simulation models are useful for projecting how N export will change in the future, most models ignore biogeochemical “hotspots” that develop in drylands as moist microsites become hydrologically disconnected from plant roots when soils dry out. These hotspots enable N to accumulate over dry periods and rapidly flush to streams when soils wet up. To better project future N export, we developed a framework for representing hotspots using the ecohydrological model RHESSys. We then conducted a series of virtual experiments to understand how uncertainties in model structure and parameters influence N export. Modeled export was sensitive to the abundance of hotspots in a watershed, increasing linearly and then reaching an asymptote with increasing hotspot abundance. Peak streamflow N was also sensitive to a soil moisture threshold at which subsurface flow from hotspots reestablished, allowing N to be transferred to streams; it increased and then decreased with an increasing threshold value. Finally, N export was generally higher when water diffused out of hotspots slowly. In a case study, we found that when hotspots were modeled explicitly, peak streamflow nitrate export increased by 29%, enabling us to better capture the timing and magnitude of N losses observed in the field. This modeling framework can improve projections of N export in watersheds where hotspots play an increasingly important role in water quality.

A document by Jason J. Venkiteswaran. Click on the document to view its contents.

The complex interactions among soil, vegetation, and site hydrologic conditions driven by precipitation and tidal cycles control biogeochemical transformations and bi-directional exchange of carbon and nutrients across the terrestrial-aquatic interfaces (TAIs) in the coastal regions. This study uses a highly mechanistic model, ATS-PFLOTRAN, to explore how these interactions impact the material exchanges and carbon and nitrogen cycling along a TAI transect in the Chesapeake Bay region that spans zones of open water, coastal wetland and upland forest. Several simulation scenarios are designed to parse the effects of the individual controlling factors and the sensitivity of carbon cycling to reaction constants derived from laboratory experiments. Our simulations revealed a hot zone for carbon cycling under the coastal wetland and the transition zones between the wetland and the upland. Evapotranspiration is found to enhance the exchange fluxes between the surface and subsurface domains, resulting in higher dissolved oxygen concentration in the TAI. The transport of organic carbon decomposed from leaves provides additional source of organic carbon for the aerobic respiration and denitrification processes in the TAI, while the variability in reaction rates mediated by microbial activities plays a dominant role in controlling the heterogeneity and dynamics of the simulated redox conditions. This modeling-focused exploratory study enabled us to better understand the complex interactions of various system components at the TAIs that control the hydro-biogeochemical processes, which is an important step towards representing coastal ecosystems in larger-scale Earth system models.

The Carpathian Mountains form the large collisional orocline stretching from Vienna, Austria to Bucharest, Romania. The Western and Inner Carpathians include the High Tatra mountains, which exhibit the highest elevation peaks of the entire mountain belt. Here we studied the exhumation history of an area near Gerlachovský štít, the topographically highest point of the High Tatras. Granitoid samples from different elevations were collected and analyzed for apatite (U-Th)/He (n=12; 5-6 aliquots) and zircon (U-Th)/He ages (n=22; 2-4 aliquots). In addition, apatite U-Pb dating by LA-ICPMS was conducted to complement existing zircon U-Pb dates to track the evolution of the High Tatra Mountains from the onset of magmatism during the Variscan orogeny. The (U-Th)/He apatite ages show a general increase from 9.6 ± 0.6 Ma to 31.9 ± 2.0 Ma to from lower to higher elevations. The zircon (U-Th)/He ages are more scattered and range from 13.5 ± 1.1 Ma to 47.8 ± 3.9 Ma. These reported ages agree with published low-temperature thermochronometric results. However, the apparent average exhumation rates for zircon and apatite (U-Th)/He data derived from the age-to-elevation profile near Gerlachovský štít are inconsistent with a proposed rapid early Miocene exhumation pulse. Apatite U-Pb ages obtained in this study are between 337.61 ± 2.21 Ma and 372.74 ± 3.09 Ma. These ages agree with previously reported zircon dates from the same or nearby samples. This observation is indicative of rapid cooling of the granitoids following crystallization. However, the greatest variance in both data sets were observed from samples collected near the sub-Tatra fault and along the Ružbachy fault. This observation was used to confine regions about these major structures that have distinct exhumation records. The results of the (U-Th)/He ages captures both pre- and post-Miocene slow cooling interrupted by early Miocene tectonic unroofing. Overall, these results are used to outline the earliest tectonic history of the High Tatra Mountains until the onset of more recent exhumation and impacts our understanding of the origin and development of this section of the arcuate mountain belt.

A document by Elizabeth Catlos. Click on the document to view its contents.

Climate change is expected to alter the input of nitrogen (N) sources in the Eastern Canadian Arctic Archipelago (ECAA) and Baffin Bay due to increased discharge from glacial meltwater and permafrost thaw. Since dissolved inorganic N is generally depleted in surface waters, dissolved organic N (DON) could represent a significant N source fueling phytoplankton activity in Arctic ecosystems. Yet, few DON data for this region exist. We measured concentrations and stable isotope ratios (δ15N and δ18O) of DON and nitrate (NO3−) to investigate the sources and cycling of dissolved nitrogen in regional rivers and at the sea surface from samples collected in the ECAA and Baffin Bay during the summer of 2019. The isotopic signatures of NO3- in rivers could be reproduced in a steady state isotopic model by invoking mixing between atmospheric NO3- and nitrified ammonium as well as NO3- assimilation by phytoplankton. DON concentrations were low in most rivers (≤4.9 µmol L−1), whereas the concentrations (0.54–12 µmol L−1) and δ15N of DON (−0.71–9.6 ‰) at the sea surface were variable among stations, suggesting dynamic cycling and/or distinctive sources. In two regions with high chl-a, DON concentrations were inversely correlated with chlorophyll‐an and the d15N of DON, suggesting net DON consumption in localized phytoplankton blooms. We derived an isotope effect of −6.9‰ for DON consumption. Our data helps establish a baseline to assess future change in nutrient regime for this climate sensitive region.

Hydrological conditions (i.e., high-flow versus low-flow) in peatland drainage streams influence both the quantity of dissolved organic carbon (DOC) exports and dissolved organic matter (DOM) composition. Yet, our knowledge on DOM fate after exports from the peatland remains limited while this highly reactive component sustains emissions and exports of carbon dioxide (CO2) from streams through degradation processes. The present study demonstrates the relationships between DOM composition evolution and catchment hydrological conditions along a 3 km long headwater stream running through a boreal peatland, from its source to the outlet. Our results show that hydrological conditions significantly influenced DOM composition evolution along the stream. DOM exported during high-flow conditions presented a composition similar to peat porewater in terms of DOC:DON ratio and aromaticity, but a lower average molecular weight, indicating preferential exports of low molecular weight DOM recently produced in the acrotelm. The DOM composition changed little along the stream during high-flow as it was rapidly flushed downstream. During low-flow conditions, DOM composition evolved along the stream in contrast to high-flow with a strong increase in DOM aromaticity and molecular weight along the stream. These changes were significantly correlated to the water residence time in the stream and to the estimated proportion of mineralized DOC to total DOC flux exported at the stream outlet. These results highlight the importance of hydrological conditions on DOM dynamics as DOM was locally mineralized during low-flow conditions, when DOC exports were low, while mineralization processes happened downstream under high-flow conditions which favored important DOC exports.

Peatlands are sources of the bioaccumulating neurotoxin methylmercury (MeHg) and linked to adverse health outcomes, yet the impact of climate change and reductions in atmospheric pollutants on mercury (Hg) export from peatlands are highly uncertain. Here, we present the response in annual flow-weighted concentrations (FWC) and yields of total-Hg (THg) and MeHg to cleaner air and climate change using an unprecedented hydroclimatic (55-years; streamflow, air temperature, precipitation, regional and peatland water tables), depositional chemistry (21-years; Hg and major ions concentration and total mass), and streamwater chemistry (~17-years; THg, MeHg, major ions, total organic carbon, and pH) datasets from a reference peatland catchment in the north central USA. Over the hydroclimatic record, annual mean air temperature increased by ~1.8 ℃, decreasing baseflow and, subsequently, the efficiency that precipitation was converted to streamwater runoff (runoff ratio). Concurrently, precipitation-based deposition of sulfate and Hg declined, where wet Hg deposition rates declined to near pre-industrial levels. Annual MeHg FWC was positively correlated mean annual air temperatures (p=0.03, r=0.51), annual runoff ratio (p<0.0001, r=0.76), and wet Hg deposition concentration (p<0.0001, r=0.79). Over the study period, decreasing wet Hg deposition concentration and annual runoff ratios counterbalanced increased peatland MeHg production due to higher air temperatures, leading to an overall decline in streamwater MeHg FWC. Climate change and cleaner air were responsible for 0.51 and 0.32 of the variability in MeHg FWC, respectively. Streamwater MeHg export may continue to decrease only if declines in runoff ratio and wet Hg deposition concentration persistently outpace increased air temperature.

Mineral precipitation can form complex patterns under non-equilibrium conditions, in which two representative patterns are rhythmic Liesegang stripes and fractal dendrites. Interestingly, both patterns occur in the same rock formations, including various dendritic morphologies found in different rocks, such as limestone and sandstone. However, the underlying mechanism for selecting the vastly different mineral precipitation patterns remains unclear. We use a phase-field model to reveal the mechanisms driving pattern selection in mineral precipitation. Simulations allow us to explore the effects of diffusion parameters on determining the dendritic morphologies. We also propose a general criterion to distinguish the resulting dendrites in simulations and field observations based on a qualitative visual distinction into three categories and a quantitative fractal dimension phase diagram. Using this model, we reproduce the classified dendrites in the field and invert for the key parameters that reflect the intrinsic material properties and geological environments. This study provides a quantitative tool for identifying the morphology selection mechanism with potential applications to geological field studies, exploration for resource evaluation, and other potential industrial applications.

A document by Shannon Sterling. Click on the document to view its contents.

A document by Vivesh V Kapur. Click on the document to view its contents.

Persistent volcanic activity is thought to be linked to degassing, but volatile transport at depth cannot be observed directly. Instead, we rely on indirect constraints such as CO2-H2O concentrations in melt inclusions trapped at different depth, but this data is rarely straight-forward to interpret. In this study, we integrate a multiscale conduit-flow model for non-eruptive conditions and a volatile-concentration model to compute synthetic profiles of volatile concentrations for different flow conditions and CO2 fluxing. We find that actively segregating bubbles in the flow enhance the mixing of volatile-poor and volatile-rich magma in vertical conduit segments, even if the radius of these bubbles is several orders of magnitude smaller than the width of the conduit. This finding suggests that magma mixing is common in volcanic systems when magma viscosities are low enough to allow for bubble segregation as born out by our comparison with melt-inclusion data: Our simulations show that even a small degree of mixing leads to volatile concentration profiles that are much more comparable to observations than either open- or closed-system degassing trends for both Stromboli and Mount Erebus. Our results also show that two of the main processes affecting observed volatile concentrations, magma mixing and CO2 fluxing, leave distinct observational signatures, suggesting that tracking them jointly could help better constrain changes in conduit flow. We argue that disaggregating melt-inclusion data based on the eruptive behavior at the time could advance our understanding of how conduit flow changes with eruptive regimes.

Although adequately detailed kerosene chemical-combustion Arrhenius reaction-rate suites were not readily available for combustion modeling until ca. the 1990’s (e.g., Marinov [1998]), it was already known from mass-spectrometer measurements during the early Apollo era that fuel-rich liquid oxygen + kerosene (RP-1) gas generators yield large quantities (e.g., several percent of total fuel flows) of complex hydrocarbons such as benzene, butadiene, toluene, anthracene, fluoranthene, etc. (Thompson [1966]), which are formed concomitantly with soot (Pugmire [2001]). By the 1960’s, virtually every fuel-oxidizer combination for liquid-fueled rocket engines had been tested, and the impact of gas phase combustion-efficiency governing the rocket-nozzle efficiency factor had been empirically well-determined (Clark [1972]). Up until relatively recently, spacelaunch and orbital-transfer engines were increasingly designed for high efficiency, to maximize orbital parameters while minimizing fuels and structural masses: Preburners and high-energy atomization have been used to pre-gasify fuels to increase (gas-phase) combustion efficiency, decreasing the yield of complex/aromatic hydrocarbons (which limit rocket-nozzle efficiency and overall engine efficiency) in hydrocarbon-fueled engine exhausts, thereby maximizing system launch and orbital-maneuver capability (Clark; Sutton; Sutton/Yang). The combustion community has been aware that the choice of Arrhenius reaction-rate suite is critical to computer engine-model outputs. Specific combustion suites are required to estimate the yield of high-molecular-weight/reactive/toxic hydrocarbons in the rocket engine combustion chamber, nonetheless such GIGO errors can be seen in recent documents. Low-efficiency launch vehicles also need larger fuels loads to achieve the same launched mass, further increasing the yield of complex hydrocarbons and radicals deposited by low-efficiency rocket engines along launch trajectories and into the stratospheric ozone layer, the mesosphere, and above. With increasing launch rates from low-efficiency systems, these persistent (Ross/Sheaffer [2014]; Sheaffer [2016]), reactive chemical species must have a growing impact on critical, poorly-understood upper-atmosphere chemistry systems.