Hypoxic and acidic — Soils on mofette fields

Rennert, Thilo; Pfanz, Hardy

doi:10.1016/j.geoderma.2016.06.019

Cited by 16 publications

(13 citation statements)

References 61 publications

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“…Weaker gas bubbling occurs in some oil seeps emerging from the soil in the park (Figures 2b and 2c). Gardens and soil covered areas often show lack of grass, which is a suspected indication of oxygen depletion in the soil (as observed, e.g., in CO 2 -rich mofettes; Rennert & Pfanz, 2016) due to enhanced hydrocarbon concentrations ( Figure 2d).…”

Section: Description Of the Seepage Areamentioning

confidence: 79%

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

2017

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Natural hydrocarbon (oil and gas) seeps are widespread in Los Angeles, California, due to gas migration, along faults, from numerous subsurface petroleum fields. These seeps may represent important natural contributors of methane (CH4) and heavier alkanes (C2‐C4) to the atmosphere, in addition to anthropogenic fossil fuel and biogenic sources. We measured the CH4 flux by closed‐chamber method from the La Brea Tar Pits park (0.1 km2), one of the largest seepage sites in Los Angeles. The gas seepage occurs throughout the park, not only from visible oil‐asphalt seeps but also diffusely from the soil, affecting grass physiology. About 500 kg CH4 d−1 is emitted from the park, especially along a belt of enhanced degassing that corresponds to the 6th Street Fault. Additional emissions are from bubble plumes in the lake within the park (order of 102–103 kg d−1) and at the intersection of Wilshire Boulevard and Curson Avenue (>130 kg d−1), along the same fault. The investigated area has the highest natural gas flux measured thus far for any onshore seepage zone in the USA. Gas migration, oil biodegradation, and secondary methanogenesis altered the molecular composition of the original gas accumulated in the Salt Lake Oil Field (>300 m deep), leading to high C1/C2+ and i‐butane/n‐butane ratios. These molecular alterations can be important tracers of natural seepage and should be considered in the atmospheric modeling of the relative contribution of fossil fuel (anthropogenic fugitive emission and natural geologic sources) versus biogenic sources of methane, on local and global scales.

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Section: Description Of the Seepage Areamentioning

confidence: 79%

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

2017

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“…This is expressed in crippled vegetation that is less high and brown-colored because of chlorosis, meaning the insufficient production of chlorophyll. Different plant species in the surrounding areas are also found in the dry mofette areas [29,30]. Sometimes, the dry mofettes have vegetation-free depressions where soil CO 2 concentration and CO 2 flux are too high for plants to grow [29].…”

Section: Research Areamentioning

confidence: 99%

“…Different plant species in the surrounding areas are also found in the dry mofette areas [29,30]. Sometimes, the dry mofettes have vegetation-free depressions where soil CO 2 concentration and CO 2 flux are too high for plants to grow [29]. Because the ground in these areas is saturated with CO 2 [28], the organic material does not decompose as fast as in the surrounding areas and accumulates, which leads to an elevated ground level.…”

Section: Research Areamentioning

confidence: 99%

Nonvolcanic Carbon Dioxide Emission at Continental Rifts: The Bublak Mofette Area, Western Eger Rift, Czech Republic

et al. 2019

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This study presents the results of gas flux measurements of cold, mantle-derived CO2 release at the Bublák mofette field (BMF), located inside of the N-S directed Počátky Plesná fault zone (PPFZ). The PPFZ is presently seismically active, located in the eastern part of the Cheb Basin, western Eger Rift, Central Europe. The goal of the work was to identify the linkage between tectonics and gas flux. The investigated area has a size of 0,43 km2 in which 1.115 locations have been measured. Besides classical soil CO2 gas flux measurements using the closed chamber method (West Systems), drone-based orthophotos were used in combination with knowledge of plant zonation to find zones of high degassing in the agriculturally unused part of the BMF. The highest observed soil CO2 gas flux is 177.926,17 g m-2 d-1, and the lowest is 0,28 g m-2 d-1. Three statistical methods were used for the calculation of the gas flux: arithmetic mean, kriging, and trans-Gaussian kriging. The average CO2 soil degassing of the BMF is 30 t d-1 for an area of 0,43 km2. Since the CO2 soil degassing of the Hartoušov mofette field (HMF) amounts to 23 t d-1 for an area of 0,35 km2, the average dry degassing values of the BMF and HMF are in the same magnitude of order. The amount of CO2 flux from wet mofettes is 3 t d-1 for the BMF and 0,6 t d-1 for the HMF. It was found that the degassing in the BMF and HMF is not in accordance with the pull-apart basin interpretation, based on the direction of degassing as well as topography and sediment fill of the suggested basins. En-echelon faults inside of the PPFZ act as fluid channels to depth (CO2 conduits). These structures inside the PPFZ show beginning faulting and act as tectonic control of CO2 degassing.

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“…3) revealed distinct differences in the spatial pattern of emitted CO 2 , with low emission rates in a north-south trending zone in the southern part of the mofette field and heavy degassing in the central and northern part (Schütze et al, 2012;Kämpf et al, 2013;Rennert and Pfanz, 2016;Nickschick et al, 2015Nickschick et al, , 2017. This led Nickschick et al (2015) to hypothesize that sinistral strike-slip fault movement causes the opening of pull-apart structures, in which intense mantle-derived CO 2 degassing occurs in conduits.…”

Section: Co 2 Mappingmentioning

confidence: 99%

Drilling into an active mofette: pilot-hole study of the impact of CO<sub>2</sub>-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic)

et al. 2017

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Abstract. Microbial life in the continental "deep biosphere" is closely linked to geodynamic processes, yet this interaction is poorly studied. The Cheb Basin in the western Eger Rift (Czech Republic) is an ideal place for such a study because it displays almost permanent seismic activity along active faults with earthquake swarms up to M L 4.5 and intense degassing of mantle-derived CO 2 in conduits that show up at the surface in form of mofettes. We hypothesize that microbial life is significantly accelerated in active fault zones and in CO 2 conduits, due to increased fluid and substrate flow. To test this hypothesis, pilot hole HJB-1 was drilled in spring 2016 at the major mofette of the Hartoušov mofette field, after extensive pre-drill surveys to optimize the well location. After drilling through a thin caprock-like structure at 78.5 m, a CO 2 blowout occurred indicating a CO 2 reservoir in the underlying sandy clay. A pumping test revealed the presence of mineral water dominated by Na + , Ca 2+ , HCO The cored sediments are mudstones with minor carbonates, sandstones and lignite coals that were deposited in a lacustrine environment. Deformation structures and alteration features are abundant in the core. Ongoing studies will show if they result from the flow of CO 2 -rich fluids or not.

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Hypoxic and acidic — Soils on mofette fields

Cited by 16 publications

References 61 publications

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

Nonvolcanic Carbon Dioxide Emission at Continental Rifts: The Bublak Mofette Area, Western Eger Rift, Czech Republic

Drilling into an active mofette: pilot-hole study of the impact of CO<sub>2</sub>-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic)

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Hypoxic and acidic — Soils on mofette fields

Cited by 16 publications

References 61 publications

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

Emission of Methane and Heavier Alkanes From the La Brea Tar Pits Seepage Area, Los Angeles

Nonvolcanic Carbon Dioxide Emission at Continental Rifts: The Bublak Mofette Area, Western Eger Rift, Czech Republic

Drilling into an active mofette: pilot-hole study of the impact of CO&lt;sub&gt;2&lt;/sub&gt;-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic)

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Drilling into an active mofette: pilot-hole study of the impact of CO<sub>2</sub>-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic)