Methane seepage in an urban development area (Bacau, Romania): origin, extent, and hazard

Baciu, Călin; Etiope, Giuseppe; Cună, Stela; Spulber, L.

doi:10.1111/j.1468-8123.2008.00228.x

Cited by 25 publications

(7 citation statements)

References 18 publications

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“…Methane flux was calculated using the linear regression of increased gas concentration values over time (Thielemann et al. 2000; Baciu et al. 2008).…”

Section: Methodsmentioning

confidence: 99%

Origin and flux of a gas seep in the Northern Alps (Giswil, Switzerland)

Etiope¹,

Zwahlen²,

Anselmetti³

et al. 2010

Geofluids

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Natural gas seeps in the Alpine region are poorly investigated. However, they can provide useful information regarding the hydrocarbon potential of sedimentary Alpine units and related geofluid migration, typically controlled by pressurized gas accumulations and tectonics. A gas seep located near Giswil, in the Swiss Northern Alps, was investigated, for the first time, for molecular and isotopic gas composition, methane flux to the atmosphere, and gas flux variations over time. The analyses indicated that the gas was thermogenic (CH 4 > 96%; d 13 C 1 : )35.5& to )40.2&) and showed evidence of subsurface petroleum biodegradation ( 13 C-enriched CO 2 , and very low C 3+ concentrations). The source rock in the region is marine Type II kerogen, which is likely the same as that providing thermogenic gas in the nearby Wilen shallow well, close to Lake Sarnen. However, the lack of d 13 C CO2 and d 13 C 3 data for that well prevented us from determining whether the Wilen and Giswil seeps are fed by the same reservoir and seepage system. Gas fluxes from the Giswil seep, measured using a closedchamber system, were significant and mainly from two major vents. However, a substantial gas exhalation from the soil occurs diffusely in an area of at least 115 m 2 , leading to a total CH 4 output conservatively estimated to be at least 16 tonnes per year. Gas flux variations, monitored over a 1-month period by a special tent and flowmeter, showed not only daily meteorological oscillations, but also an intrinsic 'pulsation' with periods of enhanced flux that lasted 2-6 h each, occurring every few days. The pulses are likely related to episodes of gas pressure build-up and discharge along the seepage system. However, to date, no relationship to seismicity in the active Sarnen strike-slip fault system has been established.

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“…Methane flux was calculated using the linear regression of increased gas concentration values over time (Thielemann et al. 2000; Baciu et al. 2008).…”

Section: Methodsmentioning

confidence: 99%

Origin and flux of a gas seep in the Northern Alps (Giswil, Switzerland)

Etiope¹,

Zwahlen²,

Anselmetti³

et al. 2010

Geofluids

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“…Measurements were made with the accumulation chamber method (Livingston & Hutchinson 1995Baciu et al. 2008; D’Alessandro et al.…”

Section: Study Area and Methodsmentioning

confidence: 99%

Diffuse hydrothermal methane output and evidence of methanotrophic activity within the soils at Sousaki (Greece)

et al. 2011

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Methane soil flux measurements have been made in 38 sites at the geothermal system of Sousaki (Greece) with the closed chamber method. Fluxes range from )47.6 to 29 150 mg m )2 day )1 , and the diffuse CH 4 output of the system has been estimated at 19 t a )1 . Contemporaneous CO 2 flux measurements showed a moderate positive correlation between CO 2 and CH 4 fluxes. Comparison of the CO 2 ⁄ CH 4 soil flux ratios with the CO 2 ⁄ CH 4 ratio of the gases of the main gas manifestations provided evidence for methanotrophic activity within the soil. Laboratory CH 4 consumption experiments confirmed the presence of methanotrophic microorganisms in soil samples collected at Sousaki. Consumption was generally in the range from )4.9 to )38.9 pmolCH 4 h )1 g )1 but could sometimes reach extremely high values ()33 000 pmolCH 4 h )1 g )1 ). These results are consistent with recent studies on other geothermal systems that revealed the existence of thermoacidophilic bacteria exerting methanotrophic activity in hot, acid soils, thereby reducing methane emissions to the atmosphere.

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“…The gas flux was calculated from an understanding of the concentration build‐up, the accumulation time, and the chamber height (Thielemann et al. 2000; Baciu et al. 2008).…”

Section: Methodsmentioning

confidence: 99%

Methane emission from natural gas seeps and mud volcanoes in Transylvania (Romania)

Spulber¹,

Etiope²,

Baciu³

et al. 2010

Geofluids

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Gas seepage from petroleum basins is the second largest natural source of methane to the atmosphere, after wetlands. The uncertainty in global emission estimates should be reduced by extending the flux database which is fundamental for defining the emission factors and the actual area of seepage adopted for up-scaling. As a contribution to this goal, we report a new seepage data-set for the Transylvanian Basin, one of the largest natural gas producing regions of Europe, that is characterized by the widespread occurrence of natural leakages of gas at the surface, including at least 73 mud volcanoes and gas seeps. In this study, methane flux was measured using closed-chambers, from 12 seepage sites, in correspondence with focused gas vents (mud volcano craters, bubbling pools, and flammable gas leaks), in the soil surrounding the vents, and at 15 sites located far from macroseep zones but close to gas fields. Fluxes from individual vents (macro-seeps) were found to reach orders of kg CH 4 m )2 day )1 (up to 12 kg m )2 day )1 ) and diffuse fluxes from soils (miniseepage) were found to be up to a few g CH 4 m )2 day )1 . Far from seep zones, positive CH 4 fluxes (microseepage) may occur locally, typically on the order of tens to hundreds of mg m )2 day )1 . The values, as well as the occurrence of seepage even far from vent zones and in mud volcanoes that are apparently extinct, are coherent with results obtained in other countries. Gas fluxes from macro-seeps and soils may change seasonally, but the interannual variation of the average emission factor was found to be minimal. The total CH 4 output for Transylvania macro-seeps is estimated conservatively to be around 680 t year )1 ; the total geo-CH 4 seepage emission from the Transylvania petroleum system could be approximately 40 · 10 3 t year )1 , and at least 100 · 10 3 t year )1 for all Romanian petroleum systems, that is roughly 10% of the total anthropogenic CH 4 emission in the country.

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Methane seepage in an urban development area (Bacau, Romania): origin, extent, and hazard

Cited by 25 publications

References 18 publications

Origin and flux of a gas seep in the Northern Alps (Giswil, Switzerland)

Origin and flux of a gas seep in the Northern Alps (Giswil, Switzerland)

Diffuse hydrothermal methane output and evidence of methanotrophic activity within the soils at Sousaki (Greece)

Methane emission from natural gas seeps and mud volcanoes in Transylvania (Romania)

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