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  • Other Sources  (9)
  • ACS (American Chemical Society)  (9)
  • 2020-2024  (9)
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  • 2020  (9)
  • 1
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    Dynamics of live oil droplets and natural gas bubbles in deep water (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: Explaining the dynamics of gas-saturated live petroleum in deep water remains a challenge. Recently, Pesch et al. (Environ. Eng. Sci. 2018, 35, 289−299) reported laboratory experiments on methane-saturated oil droplets under emulated deep-water conditions, providing an opportunity to elucidate the underlying dynamical processes. We explain these observations with the Texas A&M Oil spill/Outfall Calculator (TAMOC), which models the pressure-, temperature-, and composition-dependent interactions between: oil-gas phase transfer; aqueous dissolution; and densities and volumes of liquid oil droplets, gas bubbles, and two-phase droplet-bubble pairs. TAMOC reveals that aqueous dissolution removed 〉95% of the methane from ~3.5-mm live oil droplets within 14.5 min, prior to gas bubble formation, during the experiments of Pesch et al. Additional simulations indicate that aqueous dissolution, fluid density changes, and gas-oil phase transitions (ebullition, condensation) may all contribute to the fates of live oil and gas in deep water, depending on the release conditions. Illustrative model scenarios suggest that 5-mm diameter gas bubbles released at 〈470 m water depth can transport methane, ethane, and propane to the water surface. Ethane and propane can reach the water surface from much deeper releases of 5-mm diameter live oil droplets, during which ebullition occurs at water depths of 〈70 m.
    Type: Article , PeerReviewed
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  • 2
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    Bromotryptamine and Imidazole Alkaloids with Anti-inflammatory Activity from the Bryozoan Flustra foliacea (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: Chemical investigation of the marine bryozoan Flustra foliacea collected in Iceland resulted in isolation of 13 new bromotryptamine alkaloids, flustramines Q-W (1-7) and flustraminols C-H (8-13), and two new imidazole alkaloids, flustrimidazoles A and B (14 and 15), together with 12 previously described compounds (16-27). Their structures were established by detailed spectroscopic analysis using 1D and 2D NMR and HRESIMS. Structure 2 was verified by calculations of the 13C and 1H NMR chemical shifts using density functional theory. The relative and absolute configurations of the new compounds were elucidated on the basis of coupling constant analysis, NOESY, [α]D, and ECD spectroscopic data, in addition to chemical derivatization. The compounds were tested for in vitro anti-inflammatory activity using a dendritic cell model. Eight compounds (1, 3, 5, 13, 16, 18, 26, and 27) decreased dendritic cell secretion of the pro-inflammatory cytokine IL-12p40, and two compounds (4 and 14) increased secretion of the anti-inflammatory cytokine IL-10. Deformylflustrabromine B (27) showed the most potent anti-inflammatory effect (IC50 2.9 μM). These results demonstrate that F. foliacea from Iceland expresses a broad range of brominated alkaloids, many without structural precedents. The potent anti-inflammatory activity in vitro of metabolite 27 warrants further investigations into its potential as a lead for inflammation-related diseases.
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  • 3
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    Methane Emissions from Abandoned Oil and Gas Wells in California (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: California hosts ∼124,000 abandoned and plugged (AP) oil and gas wells, ∼38,000 idle wells, and ∼63,000 active wells, whose methane (CH4) emissions remain largely unquantified at levels below ∼2 kg CH4 h–1. We sampled 121 wells using two methods: a rapid mobile plume integration method (detection ∼0.5 g CH4 h–1) and a more sensitive static flux chamber (detection ∼1 × 10–6 g CH4 h–1). We measured small but detectable methane emissions from 34 of 97 AP wells (mean emission: 0.286 g CH4 h–1). In contrast, we found emissions from 11 of 17 idle wells—which are not currently producing (mean: 35.4 g CH4 h–1)—4 of 6 active wells (mean: 189.7 g CH4 h–1), and one unplugged well—an open casing with no infrastructure present (10.9 g CH4 h–1). Our results support previous findings that emissions from plugged wells are low but are more substantial from idle wells. In addition, our smaller sample of active wells suggests that their reported emissions are consistent with previous studies and deserve further attention. Due to limited access, we could not measure wells in most major active oil and gas fields in California; therefore, we recommend additional data collection from all types of wells but especially active and idle wells.
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  • 4
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    Unexpected Source and Transport of Iron from the Deep Peru Margin (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: Iron is the most important micronutrient in the ocean, but the nature and magnitude of its sources and sinks to the ocean are poorly constrained. Here we assess our understanding of the sources and sinks of iron in margin environments by synthesizing observations from the U.S. GEOTRACES GP16 Eastern Tropical Pacific Zonal Transect (EPZT) cruise near the Peru margin. GP16 observations showed elevated dissolved iron (dFe) concentrations along the margin, but a larger westward plume of dFe at slope depths (1000–3000 m) in oxygenated waters, rather than at shelf depths (100–300 m) in oxygen deficient waters. We examine the potential explanations for this unexpected observation. Multiple tracers from GP16 suggest that sediment resuspension was important at slope depths, which would lead to enhanced benthic flux of dFe above what was previously measured. The difference in the apparent persistence and penetration of shelf versus slope plumes of dFe into the interior of the ocean likely results from faster removal rates of the shelf dFe compared to slope dFe. The dFe sourced from the shelf was almost entirely in the dFe(II) form, whereas dFe sourced from the slope was almost entirely in the dFe(III) form. Although benthic dFe(II) diffuses into oxygen deficient overlying waters, there is still oxidation of dFe(II), which precipitates to particulate Fe(III). In contrast, the slope plume appears to persist in a stabilized dFe(III) form. We hypothesize that sediment porewaters with moderate organic carbon delivery to sediments and shallow oxygen penetration are especially good sources of persistent dFe to the water column.
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  • 5
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    Tridiscorhabdin and Didiscorhabdin, the First Discorhabdin Oligomers Linked with a Direct C–N Bridge from the Sponge Latrunculia biformis Collected from the Deep Sea in Antarctica (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: Guided by LC-MS/MS molecular networking-based metabolomics and cytotoxic activity, two new discorhabdin-type alkaloids, tridiscorhabdin (1) and didiscorhabdin (2), were isolated from the sponge Latrunculia biformis, collected from the Weddell Sea (Antarctica) at -291 m depth. Their structures were established by HRESIMS, NMR, [α]D, and ECD data coupled with DFT calculations. Both compounds bear a novel C-N bridge (C-1/N-13) between discorhabdin monomers, and 1 represents the first trimeric discorhabdin molecule isolated from Nature. Tridiscorhabdin (1) exhibited strong cytotoxic activity against the human colon cancer cell line HCT-116 (IC50 value 0.31 μM).
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  • 6
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    Dissolved Strontium, Sr/Ca Ratios, and the Abundance of Acantharia in the Indian and Southern Oceans (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: We report measurements of strontium concentrations and Sr/Ca ratios in the Indian and Southern Oceans, which show that subtle geochemical variations along the main thermocline are the product of calcium carbonate (CaCO3) and celestite (SrSO4) precipitation and dissolution. Our calculations suggest that celestite skeletons precipitated by Acantharia contribute up to 10 mol % of the combined amount of carbonate and celestite shells precipitated in the Indian Ocean. The data suggest that the distribution of the concentration of strontium in the global ocean is governed by the different modes of deep-water formation in the Southern Ocean and North Atlantic. The formation of Antarctic bottom waters from strontium-rich, upwelled deep waters forms a southern end member contrasted with the strontium depleted North Atlantic deep water. The difference in strontium concentrations and Sr/Ca ratios of the different water masses reported here is maintained by precipitation, export, and dissolution of CaCO3 and SrSO4. These preformed strontium concentrations correlate linearly with nitrate and phosphate concentrations in the Indian Ocean, but this correlation is weaker in low latitudes, where the mixotrophic lifestyle of Acantharia allows them to thrive in nutrient-depleted environments.
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  • 7
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    Novel Syntrophic Isovalerate-Degrading Bacteria and Their Energetic Cooperation with Methanogens in Methanogenic Chemostats (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: Isovalerate is an important intermediate in anaerobic degradation of proteins/amino acids. Little is known about how this compound is degraded due to challenges in cultivation and characterization of isovalerate-degrading bacteria, which are thought to symbiotically depend on methanogenic archaea. In this study, we successfully enriched novel syntrophic isovalerate degraders (uncultivated Clostridiales and Syntrophaceae members) through operation of mesophilic and thermophilic isovalerate-fed anaerobic reactors. Metagenomics- and metatranscriptomics-based metabolic reconstruction of novel putative syntrophic isovalerate metabolizers uncovered the catabolic pathway and byproducts (i.e., acetate, H2, and formate) of isovalerate degradation, mechanisms for electron transduction from isovalerate degradation to H2 and formate generation (via electron transfer flavoprotein; ETF), and biosynthetic metabolism. The identified organisms tended to prefer formate-based interspecies electron transfer with methanogenic partners. The byproduct acetate was further converted to CH4 and CO2 by either Methanothrix (mesophilic) and Methanosarcina (thermophilic), which employed different approaches for acetate degradation. This study presents insights into novel mesophilic and thermophilic isovalerate degraders and their interactions with methanogens.
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  • 8
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    A New in Situ Method for Tracing Denitrification in Riparian Groundwater (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: The spatiotemporal dynamics of denitrification in groundwater are still not well-understood because of a lack of efficient methods to quantify this biogeochemical reaction pathway. Previous research used the ratio of N2 to argon (Ar) to quantify net production of N2 via denitrification by separating the biologically generated N2 component from the atmospheric-generated components. However, this method does not allow the quantification of the atmospheric components accurately because the differences in gas partitioning between N2 and Ar are being neglected. Moreover, conventional (noble) gas analysis in water is both expensive and labor-intensive. We overcome these limitations by using a portable mass spectrometer system, which enables a fast and efficient in situ analysis of dissolved (noble) gases in groundwater. By analyzing a larger set of (noble) gases (N2, He, Ar, and Kr) combined with a physically meaningful excess air model, we quantified N2 originating from denitrification. Consequently, we were able to study the spatiotemporal dynamics of N2 production due to denitrification in riparian groundwater over a six-month period. Our results show that denitrification is highly variable in space and time, emphasizing the need for spatially and temporally resolved data to accurately account for denitrification dynamics in groundwater.
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  • 9
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    Quantification of CO2 Mineralization at the Wallula Basalt Pilot Project (2020)
    ACS (American Chemical Society)
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    Publication Date: 2023-02-08
    Description: In 2013, the Pacific Northwest National Laboratory led a geologic carbon sequestration field demonstration where ∼1000 tonnes of CO2 was injected into several deep Columbia River Basalt zones near Wallula, Washington. Rock core samples extracted from the injection zone two years after CO2 injection revealed nascent carbonate mineralization that was qualitatively consistent with expectations from laboratory experiments and reactive transport modeling. Here, we report on a new detailed analysis of the 2012 pre-injection and 2015 post-injection hydrologic tests that capitalizes on the difference in fluid properties between scCO2 and water to assess changes in near-field, wellbore, and reservoir conditions that are apparent approximately two years following the end of injection. This comparative hydrologic test analysis method provides a new way to quantify the amount of injected CO2 that was mineralized in the field test. Modeling results indicate that approximately 60% of the injected CO2 was sequestered via mineralization within two years, with the resulting carbonates occupying ∼4% of the available reservoir pore space. The method presented here provides a new monitoring tool to assess the fate of CO2 injected into chemically reactive basalt formations but could also be adapted for long-term monitoring and verification within more traditional subsurface carbon storage reservoirs.
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