More Like this

1. Aerobic methane synthesis and dynamics in a river water environment

   https://doi.org/10.1002/lno.12383  

   Alowaifeer, Abdullah M. ; Wang, Qian ; Bothner, Brian ; Sibert, Ryan J. ; Joye, Samantha B. ; McDermott, Timothy R. ( June 2023 , Limnology and Oceanography)

   Reports of aerobic biogenic methane (CH₄) have generated new views about CH₄sources in nature. We examine this phenomenon in the free‐flowing Yellowstone river wherein CH₄concentrations were tracked as a function of environmental conditions, phototrophic microorganisms (using chlorophylla, Chla, as proxy), as well as targeted methylated amines known to be associated with this process. CH₄was positively correlated with temperature and Chla, although diurnal measurements showed CH₄concentrations were greatest during the night and lowest during maximal solar irradiation. CH₄efflux from the river surface was greater in quiescent edge waters (71–94 μmol m⁻² d) than from open flowing current (~ 57 μmol m⁻² d). Attempts to increase flux by disturbing the benthic environment in the quiescent water directly below (~ 1.0 m deep) or at varying distances (0–5 m) upstream of the flux chamber failed to increase surface flux. Glycine betaine (GB), dimethylamine and methylamine (MMA) were observed throughout the summer‐long study, increasing during a period coinciding with a marked decline in Chla, suggesting a lytic event led to their release; however, this did not correspond to increased CH₄concentrations. Spiking river water with GB or MMA yielded significantly greater CH₄than nonspiked controls, illustrating the metabolic potential of the river microbiome. In summary, this study provides evidence that: (1) phototrophic microorganisms are involved in CH₄synthesis in a river environment; (2) the river microbiome possesses the metabolic potential to convert methylated amines to CH₄; and (3) river CH₄concentrations are dynamic diurnally as well as during the summer active months.

    

   more » « less
2. On the formation of complex organic molecules in the interstellar medium: untangling the chemical complexity of carbon monoxide–hydrocarbon containing ice analogues exposed to ionizing radiation via a combined infrared and reflectron time-of-flight analysis

   https://doi.org/10.1039/C9CP01793C  

   Abplanalp, Matthew J. ; Kaiser, Ralf I. ( August 2019 , Physical Chemistry Chemical Physics)

   Recently, over 200 molecules have been detected in the interstellar medium (ISM), with about one third being complex organic molecules (COMs), molecules containing six or more atoms. Over the last few decades, astrophysical laboratory experiments have shown that several COMs are formed via interaction of ionizing radiation within ices deposited on interstellar dust particles at 10 K (H 2 O, CH 3 OH, CO, CO 2 , CH 4 , NH 3 ). However, there is still a lack of understanding of the chemical complexity that is available through individual ice constituents. The present research investigates experimentally the synthesis of carbon, hydrogen, and oxygen bearing COMs from interstellar ice analogues containing carbon monoxide (CO) and methane (CH 4 ), ethane (C 2 H 6 ), ethylene (C 2 H 4 ), or acetylene (C 2 H 2 ) exposed to ionizing radiation. Utilizing online and in situ techniques, such as infrared spectroscopy and tunable photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS), specific isomers produced could be characterized. A total of 12 chemically different groups were detected corresponding to C 2 H n O ( n = 2, 4, 6), C 3 H n O ( n = 2, 4, 6, 8), C 4 H n O ( n = 4, 6, 8, 10), C 5 H n O ( n = 4, 6, 8, 10), C 6 H n O ( n = 4, 6, 8, 10, 12, 14), C 2 H n O 2 ( n = 2, 4), C 3 H n O 2 ( n = 4, 6, 8), C 4 H n O 2 ( n = 4, 6, 8, 10), C 5 H n O 2 ( n = 6, 8), C 6 H n O 2 ( n = 8, 10, 12), C 4 H n O 3 ( n = 4, 6, 8), and C 5 H n O 3 ( n = 6, 8). More than half of these isomer specifically identified molecules have been identified in the ISM, and the remaining COMs detected here can be utilized to guide future astronomical observations. Of these isomers, three groups – alcohols, aldehydes, and molecules containing two of these functional groups – displayed varying degrees of unsaturation. Also, the detection of 1-propanol, 2-propanol, 1-butanal, and 2-methyl-propanal has significant implications as the propyl and isopropyl moieties (C 3 H 7 ), which have already been detected in the ISM via propyl cyanide and isopropyl cyanide, could be detected in our laboratory studies. General reaction mechanisms for their formation are also proposed, with distinct follow-up studies being imperative to elucidate the complexity of COMs synthesized in these ices. 

   more » « less
3. Modeling impacts of saltwater intrusion on methane and nitrous oxide emissions in tidal forested wetlands

   https://doi.org/10.1002/eap.2858  

   Wang, Hongqing ; Dai, Zhaohua ; Krauss, Ken W. ; Trettin, Carl C. ; Noe, Gregory B. ; Burton, Andrew J. ; Ward, Eric J. ( July 2023 , Ecological Applications)

   Emissions of methane (CH₄) and nitrous oxide (N₂O) from soils to the atmosphere can offset the benefits of carbon sequestration for climate change mitigation. While past study has suggested that both CH₄and N₂O emissions from tidal freshwater forested wetlands (TFFW) are generally low, the impacts of coastal droughts and drought‐induced saltwater intrusion on CH₄and N₂O emissions remain unclear. In this study, a process‐driven biogeochemistry model, Tidal Freshwater Wetland DeNitrification‐DeComposition (TFW‐DNDC), was applied to examine the responses of CH₄and N₂O emissions to episodic drought‐induced saltwater intrusion in TFFW along the Waccamaw River and Savannah River, USA. These sites encompass landscape gradients of both surface and porewater salinity as influenced by Atlantic Ocean tides superimposed on periodic droughts. Surprisingly, CH₄and N₂O emission responsiveness to coastal droughts and drought‐induced saltwater intrusion varied greatly between river systems and among local geomorphologic settings. This reflected the complexity of wetland CH₄and N₂O emissions and suggests that simple linkages to salinity may not always be relevant, as non‐linear relationships dominated our simulations. Along the Savannah River, N₂O emissions in the moderate‐oligohaline tidal forest site tended to increase dramatically under the drought condition, while CH₄emission decreased. For the Waccamaw River, emissions of both CH₄and N₂O in the moderate‐oligohaline tidal forest site tended to decrease under the drought condition, but the capacity of the moderate‐oligohaline tidal forest to serve as a carbon sink was substantially reduced due to significant declines in net primary productivity and soil organic carbon sequestration rates as salinity killed the dominant freshwater vegetation. These changes in fluxes of CH₄and N₂O reflect crucial synergistic effects of soil salinity and water level on C and N dynamics in TFFW due to drought‐induced seawater intrusion.

    

   more » « less
4. Iron–Nickel Alloys for Carbon Dioxide Activation by Chemical Looping Dry Reforming of Methane

   https://doi.org/10.1002/ente.201500539  

   More, Amey ; Bhavsar, Saurabh ; Veser, Götz ( May 2016 , Energy Technology)

   Chemical looping combustion is a clean combustion technology for fossil or renewable fuels. We have previously shown that the process can also be used to enable CO₂activation through reduction to CO with Fe oxygen carriers in so‐called “chemical looping dry reforming” (CLDR). Although Fe shows good reactivity with CO₂, its reactivity with methane as a fuel is low. In contrast, Ni is highly reactive for methane conversion but cannot be oxidized with CO₂. Here, we demonstrate that Fe–Ni alloys combine the reactivities of each metal synergistically. By combining materials synthesis and characterization with reactive evaluation in multicycle CLDR operation, we demonstrate that relatively low amounts of Ni suffice to activate the carrier for methane conversion and that the presence of Fe enables the reoxidation of Ni with CO₂. Moreover, the weak oxidant CO₂allows the controlled oxidation of the Fe–Ni alloy, which enables CH₄upgrading through syngas (CO+H₂) production.

    

   more » « less
5. Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions

   https://doi.org/10.1002/jeq2.20475  

   Shrestha, Raj K. ; Jacinthe, Pierre‐Andre ; Lal, Rattan ; Lorenz, Klaus ; Singh, Maninder P. ; Demyan, Scott M. ; Ren, Wei ; Lindsey, Laura E. ( July 2023 , Journal of Environmental Quality)

   Biochar is one of the few nature‐based technologies with potential to help achieve net‐zero emissions agriculture. Such an outcome would involve the mitigation of greenhouse gas (GHG) emission from agroecosystems and optimization of soil organic carbon sequestration. Interest in biochar application is heightened by its several co‐benefits. Several reviews summarized past investigations on biochar, but these reviews mostly included laboratory, greenhouse, and mesocosm experiments. A synthesis of field studies is lacking, especially from a climate change mitigation standpoint. Our objectives are to (1) synthesize advances in field‐based studies that have examined the GHG mitigation capacity of soil application of biochar and (2) identify limitations of the technology and research priorities. Field studies, published before 2022, were reviewed. Biochar has variable effects on GHG emissions, ranging from decrease, increase, to no change. Across studies, biochar reduced emissions of nitrous oxide (N₂O) by 18% and methane (CH₄) by 3% but increased carbon dioxide (CO₂) by 1.9%. When biochar was combined with N‐fertilizer, it reduced CO₂, CH₄, and N₂O emissions in 61%, 64%, and 84% of the observations, and biochar plus other amendments reduced emissions in 78%, 92%, and 85% of the observations, respectively. Biochar has shown potential to reduce GHG emissions from soils, but long‐term studies are needed to address discrepancies in emissions and identify best practices (rate, depth, and frequency) of biochar application to agricultural soils.

    

   more » « less