Isotopic and Chemical Assessment of the Dynamics of Methane Sources and Microbial Cycling during Early Development of an Oil Sands Pit Lake

Water-capped tailings technology (WCTT) is a key component of the reclamation strategies in the Athabasca oil sands region (AOSR) of northeastern Alberta, Canada. The release of microbial methane from tailings emplaced within oil sands pit lakes, and its subsequent microbial oxidation, could inhibit the development of persistent oxygen concentrations within the water column, which are critical to the success of this reclamation approach. Here, we describe the results of a four-year (2015–2018) chemical and isotopic (δ13C) investigation into the dynamics of microbial methane cycling within Base Mine Lake (BML), the first full-scale pit lake commissioned in the AOSR. Overall, the water-column methane concentrations decreased over the course of the study, though this was dynamic both seasonally and annually. Phospholipid fatty acid (PLFA) distributions and δ13C demonstrated that dissolved methane, primarily input via fluid fine tailings (FFT) porewater advection, was oxidized by the water column microbial community at all sampling times. Modeling and under-ice observations indicated that the dissolution of methane from bubbles during ebullition, or when trapped beneath ice, was also an important source of dissolved methane. The addition of alum to BML in the fall of 2016 impacted the microbial cycling in BML, leading to decreased methane oxidation rates, the short-term dominance of a phototrophic community, and longer-term shifts in the microbial community metabolism. Overall, our results highlight a need to understand the dynamic nature of these microbial communities and the impact of perturbations on the associated biogeochemical cycling within oil sands pit lakes.

WETMETH 1.0: a new wetland methane model for implementation in Earth system models

Wetlands are the single largest natural source of methane (CH4), a powerful greenhouse gas affecting the global climate. In turn, wetland CH4 emissions are sensitive to changes in climate conditions such as temperature and precipitation shifts. However, biogeochemical processes regulating wetland CH4 emissions (namely microbial production and oxidation of CH4) are not routinely included in fully coupled Earth system models that simulate feedbacks between the physical climate, the carbon cycle, and other biogeochemical cycles. This paper introduces a process-based wetland CH4 model (WETMETH) developed for implementation in Earth system models and currently embedded in an Earth system model of intermediate complexity. Here, we (i) describe the wetland CH4 model, (ii) evaluate the model performance against available datasets and estimates from the literature, and (iii) analyze the model sensitivity to perturbations of poorly constrained parameters. Historical simulations show that WETMETH is capable of reproducing mean annual emissions consistent with present-day estimates across spatial scales. For the 2008–2017 decade, the model simulates global mean wetland emissions of 158.6 Tg CH4 yr−1, of which 33.1 Tg CH4 yr−1 is from wetlands north of 45∘ N. WETMETH is highly sensitive to parameters for the microbial oxidation of CH4, which is the least constrained process in the literature.

The Use of Subsidence to Estimate Carbon Loss from Deforested and Drained Tropical Peatlands in Indonesia

Drainage is a major means of the conversion of tropical peat forests into agriculture. Accordingly, drained peat becomes a large source of carbon. However, the amount of carbon (C) loss from drained peats is not simply measured. The current C loss estimate is usually based on a single proxy of the groundwater table, spatially and temporarily dynamic. The relation between groundwater table and C emission is commonly not linear because of the complex natures of heterotrophic carbon emission. Peatland drainage or lowering groundwater table provides plenty of oxygen into the upper layer of peat above the water table, where microbial activity becomes active. Consequently, lowering the water table escalates subsidence that causes physical changes of organic matter (OM) and carbon emission due to microbial oxidation. This paper reviews peat bulk density (BD), total organic carbon (TOC) content, and subsidence rate of tropical peat forest and drained peat. Data of BD, TOC, and subsidence were derived from published and unpublished sources. We found that BD is generally higher in the top surface layer in drained peat than in the undrained peat. TOC values in both drained and undrained are lower in the top and higher in the bottom layer. To estimate carbon emission from the top layer (0–50 cm) in drained peats, we use BD value 0.12 to 0.15 g cm−3, TOC value of 50%, and a 60% conservatively oxidative correction factor. The average peat subsidence is 3.9 cm yr−1. The range of subsidence rate per year is between 2 and 6 cm, which results in estimated emission between 30 and 90 t CO2e ha−1 yr−1. This estimate is comparable to those of other studies and Tier 1 emission factor of the 2013 IPCC GHG Inventory on Wetlands. We argue that subsidence is a practical approach to estimate carbon emission from drained tropical peat is more applicable than the use of groundwater table.

Change in the Structure of Asphaltene Macromolecules of the Krapivinskoye Oil Field During Biological Oxidation

Using physico-chemical methods of research (elemental analysis, infrared spectroscopy, selective chemical destruction of sulfide and ester bonds, chromatomass spectrometry) the influence of biodegradation processes on the composition and structure of asphaltenes of light oil at the Krapivinskoye deposit was studied. The results of comparative characteristics of initial asphaltenes and asphaltenes after biodestruction are presented. Attention is paid to studying their structural parameters and composition of fragments bound in asphaltene molecules through ester and sulfide bridges. It has been shown that microbial oxidation of asphaltenes of light oil by aboriginal soil microflora (laboratory experiment) occurs through a series of catalytic processes with formation of intermediate products of transformation – alcohols, aldehydes, ketones and fatty acids. It has been established that “grey and ether-bound” fragments in asphaltene molecules of biodegradable oil differ from “bound” compounds in the structure of the original asphaltenes with the qualitative composition of saturated and aromatic hydrocarbons and heteroatomic components

Unusual Perforations in Phlogopite Crystals from Caldara di Manziana (Italy) Caused by Sulphuric Acid Generated by Microbial Oxidation of H2S Emanations

Phlogopite flakes strewn on the soil of Caldara di Manziana (Italy) display multiple minute perforations. The site is a caldera linked to recent volcanism (90 ka to 0.8 Ma) with present emanations of CO2 (~150 t d−1) and H2S (~2.55 t d−1). Stereomicroscopy and SEM–EDX observation of the phlogopite crystals shows holes and depressions <200 µm to 2 mm across. They are circular, pseudo-hexagonal, or irregular. Within the depressions, there are deposits of phlogopite alteration products consistent with a sulphuric acid attack, showing loss of Mg and K. Some are thin and homogeneous; others are thick, irregular, and chemically heterogeneous, including plates, flakes, tubes of Fe-beidellite or Fe-bearing halloysite, silica, Fe oxides, and gypsum. Areas of phlogopite surface are also altered. Sulphuric acid is produced from the H2S gas by the mediation of sulphur-oxidizing bacteria. Pseudo-hexagonal perforations are interpreted to result from slow acid attack with dissolution controlled by phlogopite crystal symmetry. Some depressions developed surrounding films of pseudo-hexagonal shape, interpreted as jarosite crystallizing radially outwards from the depressions. This style of acid attack is possibly promoted by local high humidity and precipitation that generate long-lived water droplets and films on mineral surfaces where sulphuric acid is active for prolonged times.

Bioremediation Of Soil Of The Kola Peninsula (Murmansk Region) Contaminated With Diesel Fuel

This work focuses on the creation and use of associations of hydrocarbon-oxidizing microorganisms. Bioremediation of soils with the help of mixed cultural and associations of microorganisms provides wider adaptive possibilities than individual species. This is especially important in conditions of short northern summer. The results of field experiments showed that microbial associations based on indigenous microorganisms (bacteria Pseudomonas fluorescens, P. putida, P. baetica, Microbacterium paraoxydans and fungi Penicillium commune, P. canescens st. 1, P. simplicissimum st. 1) with mineral fertilizers reduced the content of total petroleum hydrocarbons in the Hortic Arthrosol soil of the Kola Peninsula by 82% over 120 days. Also, the microbial associations with mineral fertilizers had a positive effect on the physical properties of the soil, increasing its humidity. The bacterial-fungi associations changed the number, abundance and structure of the indigenous community of microorganisms. Penicillium canescens, which was included in the composition of fungi association, became dominant. During the rapid decomposition of hydrocarbons are released to the soil toxic intermediates or metabolites of the microbial oxidation of hydrocarbons. Hydrocarbon oxidizing microfungi suppressed the germination of test plant seeds to one degree or another. Penicillium commune fungal metabolites inhibited seed germination only by 29% for Lepidium sativum L. and 24% for Triticum aestivum L. This species can be used for bioremediation of petroleum contaminated soils.

Mimicking the Microbial Oxidation of Elemental Sulfur with a Biphasic Electrochemical Cell

<p>The lack of an artificial system that mimics elemental sulfur (S₈) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S₈, overcoming the <a>incompatible solubilities </a>of the hydrophobic reactants (O₂ and S₈) and hydrophilic products (H⁺, SO₃^2–, SO₄^2–, <i>etc.</i>). The interfacial AuNPs provide a catalytic surface onto which O₂ and S₈ can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.</p>

Mimicking the Microbial Oxidation of Elemental Sulfur with a Biphasic Electrochemical Cell

<p>The lack of an artificial system that mimics elemental sulfur (S₈) oxidation by microorganisms inhibits a deep mechanistic understanding of the sulfur cycle in the biosphere and the metabolism of sulfur-oxidizing microorganisms. In this article, we present a biphasic system that mimics biochemical sulfur oxidation under ambient conditions using a liquid|liquid (L|L) electrochemical cell and gold nanoparticles (AuNPs) as an interfacial catalyst. The interface between two solvents of very different polarity is an ideal environment to oxidise S₈, overcoming the <a>incompatible solubilities </a>of the hydrophobic reactants (O₂ and S₈) and hydrophilic products (H⁺, SO₃^2–, SO₄^2–, <i>etc.</i>). The interfacial AuNPs provide a catalytic surface onto which O₂ and S₈ can adsorb. Control over the driving force for the reaction is provided by polarizing the L|L interface externally and tuning the Fermi level of the interfacial AuNPs by the adsorption of aqueous anions.</p>